Applied Micropaleontology in Coastal Ecuador, 1948

Hastigerinella eocenica Nuttall

Plate 26, figures 18, 19

Hastigerinella eocenica Nuttall 1928, Jour. Paleontology, vol. 2, p. 376, pl. 50, figs. 9-11.

Initial portion a low trochoid, later portion planispiral. First adult chambers globose but after the third or fourth showing radial prolongation which becomes progressively more pronounced. In washed residue material this species is most often represented by individual adult chambers.

This species was originally described from the Upper Eocene of Mexico and later records include the Eocene (Middle and ? Upper) of Trinidad (Cushman 1930, p. 18, pl. 3, figs. 6, 7; Renz 1942, p. 537) and the Eocene of California (Church 1931, p. 206, pl. B, fig. 8; Clark and Campbell 1942, p. 8). The form recorded under this name from the Upper Oligocene of Trinidad is a variety smaller than the Eocene specimens (Cushman and Stainforth 1945, p. 69, pl. 13, fig. 11). Thalmann (1942-a, pp. 14, 13) reported a record by Hugues of abundant Hastigerinella in the Eocene of El Alto and Lobitos in Peru, but questioned this unfigured reference because it is unusual for Hastigerinella to be a dominant genus. The Ecuadorian occurrence supports Hugues’ identification, and there is evidence that the genus thrived in cold waters unfavorable to other Foraminifera. Benton Stone (private communication) confirms that Hastigerinella occurs in the Eocene of N. Peru, where Hantkenina is exceedingly scarce. In a private communication C. D. Redmond states that H. eocenica occurs in the Middle and Upper Eocene of Colombia. In Ecuador the species is restricted to the late Middle and the Upper Eocene and is commonest in tuffaceous shales which contain abundant Radiolaria but usually only sparse Foraminifera. This species is almost absent in the normal neritic and reefal facies of the younger Eocene. A more trochoid species with attenuated pear‑shaped chambers appears in the early Oligocene.

Globigerina danvillensis Howe and Wallace

Plate 25, figures 24, 25

Globigerina danvillensis Howe and Wallace, 1932, Louisiana Dept. Conser., Geol. Bull, no. 2, p. 74, pl. 10, fig. 9.

General shape a low-spired quadrate trochoid, chambers mildly inflated, the most characteristic feature being the hispid or spinulose shell‑surface.

This species was first described from the Jackson Eocene of Louisiana and it was later recorded from the Jackson of Mississippi (Bergquist 1942, p. 95, pl. 9, figs. 24, 25). A very similar form occurs in the Upper Eocene of Trinidad, and it is probably related to G. topilensis from the Upper Eocene of Mexico (Cushman 1925, p. 7, pl. 1, fig. 9). In private communications C. D. Redmond states that he has tentatively identified a species from the Upper Eocene of Colombia as G. danvillensis, and B. Stone mentions similar forms in the Upper Eocene of northern Peru. In Ecuador this species is confined to Middle and Upper Eocene beds.

Globigerina wilsoni (?) Cole 1927

Plate 26, figures 1‑3

Globigerina wilsoni Cole, 1927, Bull. Am. Paleontology, vol. 14, no. 51, p. 34, pl. 4, figs. 8, 9.

General form a low trochoid, in larger specimens approaching nautiloid symmetry with only a faint trochoid bias. Dorsal side flat or depressed, early chambers not clearly discernible. Four chambers to a coil. Aperture crescent‑shaped, at the base of final chamber, embracing the inner coil from the umbilicus up to and sometimes beyond the periphery.

Except for the type reference from the Eocene, probably Upper Claiborne of Mexico, this species does not seem to have received mention in the literature. Possibly it has been confused with the older G. pseudo‑bulloides Plummer. In Ecuador it is commonest in the late Middle and Upper Eocene but ranges into the early Oligocene. Frequently this species and Hastigerinella eocenica are the only Foraminifera in Radiolaria‑rich shales, but G. wilsoni is equally plentiful in normal neritic facies of the same age.

Globigerina triloculinoides
(?) Beck, not Plummer

Plate 25, figures 32, 33

Globigerina triloculinoides, Beck, 1943, Jour. Paleontology, vol. 17, no. 6, p. 609, pl. 108, figs. 2, 3.

A low trochoid species, coiling actually quadrate but appearing trigonal because each chamber is approximately double the size of the previous one, and the third from last is inconspicuous, almost invisible in ventral aspect. Early chambers form a low spire with indistinct sutures, but the adult chambers are well inflated and separated by depressed sutures. In ventral aspect the inner margin of the final chamber extends diametrically across the test, concealing a simple aperture opening into the umbilicus.

This form differs aperturally from the Upper Cretaceous G. triloculinoides (Plummer 1926, p. 134, pl. 8, fig. 10; see also Galloway 1931, p. 348, pl. 39, fig. 11). It seems closer to the species first figured by Beck (loc. cit.) from the Eocene Cowlitz of Washington and later recorded from the Eo‑Oligocene Bastendorf of Oregon (Detling 1946, p. 359, pl. 51, fig. 2). A very similar form has been recorded as Globigerina sp. B from the Jackson Eocene of Louisiana and Mississippi (Howe and Wallace 1932, p. 75, pl. 10, fig. 5; Bergquist 1942, p. 95, pl. 9, figs. 20, 21, 29, 30). In Ecuador this species occurs in neritic assemblages of Upper Eocene and basal Oligocene age.

Globigerina aff. bulloides d�Orbigny

Plate 25, figures 14‑18

In Ecuador there are two forms which fall within the general usage of this name, which has been so abused as to have little value. One of these is a low trochoid of globose chambers, usually four but sometimes five to a coil. The aperture is a simple circular opening into the umbilicus and carries no lip. There is a faint similarity to G. cf. concinna but the coiling is less precise and the rate of increase of chamber‑size is distinctly greater, their diameters tripling approximately every fourth chamber. This form is close to G. diplostoma which Cushman has treated as a varietal form of G. concinna (1946‑a, p. 20, pl. 3, figs. 11, 12; pl. 4, figs. 14, 15).

In Ecuador this form ranges from Upper Eocene to mid‑Oligocene beds. It may be the same as specimens recorded from the Lower Oligocene of Mexico (Nuttall 1932, p. 29, pl. 6, figs. 13‑15).

The second form is superficially similar but more compact, the spire is flattened and the embryonic chambers are obscure. The aperture is a crescentic slit embracing the inner coil ventrally, and usually carries a small lip. Most specimens are quadrate but forms occur identical in all respects except for having five, six and even seven chambers in the final coil.

In Ecuador this form ranges from mid‑Oligocene at least as high as Upper Miocene and it is very abundant in the early Miocene.

Globorotalia centralis Cushman and Bermúdez

Plate 26, figures 27‑29

Globorotalia centralis Cushman and Bermúdez, 1937, Contr. Cushman Lab. Foram. Res., vol. 13, p. 26, pl. 2, figs. 62‑65.

A precise quadrate coil, dorsal face flat or slightly convex, chambers high (side‑view) in relation to their width (radial). In dorsal aspect each chamber tends to overlap the next one formed, emphasizing the square coiling. The distinctive aperture is a narrow slit at the base of the final chamber extending at least over the two previous chambers and sometimes to part of the next. There is no umbilical opening.

Prior to its original description from the Eocene of Cuba this species had been re-referred to Globigerina inflata from the Upper Eocene Pauji of Venezuela with the comment “common in the Upper and Middle Eocene of Mexico, the Upper Eocene of Trinidad and is recorded from the Middle Eocene of Texas” (Nuttall 1935, p. 130). A form recorded as G. inflata from the Ponce of Porto Rico, apparently from the Lower Oligocene, may be related (Galloway and Heminway 1941, p. 412, pl. 29, fig. 3). G. centralis is recorded as such from the Jackson Eocene of Mississippi (Berquist 1942, p. 97, pl. 9, figs. 34, 36, 37). The figured specimens from the Upper Eocene tend to be planoconvex with a cuboidal aspect. In Trinidad and Ecuador there is an evolutionary tendency towards inflation with decreasing age, so that the Oligocene specimens show a more globular shape and should probably be referred to a separate variety. In Ecuador, and also Trinidad, the range of the species, inclusive of the inflated variety, is from Upper Eocene to mid‑Oligocene. In association with Globigerina cf. concinna it is an excellent guide for distinguishing the older from the younger Oligocene.

Globigerina cf. concinna Reuss 1850

Plate 25, figures 19‑21

Globigerina concinna Reuss, 1850, Denkschr. Akad. Wiss. Wien, vol. 1, p. 373, pl. 47, fig. 8; Cushman 1946‑a, p. 20, pl. 3, figs. 10‑12; pl. 4, figs. 11‑15.

Dorsally a spire of subglobular chambers increasing in size slowly but very regularly, chamber diameters approximately doubling every fourth chamber. Invariably five chambers in the final coil. Ventral aspect of symmetrical pentagonal rosette of chambers around an open umbilicus. Aperture a simple circular opening directed upwards into the umbilicus and usually concealed in the direct ventral aspect.

This form has been variously described in tropical America as G. concinna and G. cf. concinna. Recently Cushman (loc. cit.) re‑figured topotypes of G. concinna Reuss and placed G. diplostoma in its synonymy. Although very similar to the European type, the American species differs in its very regular form, invariably with five chambers in the final coil and a low rate of increase in chamber size. It is probably a distinct species and because of its limited stratigraphic range deserves careful separation from the “G. bulloides” tribe. The specimen figured from the Pliocene Charco Azul of Panama, for instance, is rather of the bulloides group (Coryell and Mossman 1942, p. 238, pl. 36, fig. 27).

In Ecuador G. cf. concinna appears sparingly in the Upper Eocene and increases steadily in abundance into the lower Middle Oligocene, at which level it dies out abruptly. It has also been recorded from the Lower Oligocene Alazan of Mexico (Nuttall 1932, p. 29, pl. 6, figs. 9‑11), the Lower Oligocene Cipero of Trinidad (Cushman and Stainforth 1945, p. 67, pl. 13, fig. 1) and the “Lower Oligocene” Carapita of Venezuela (Franklin 1944, p. 317, pl. 48, fig. 5; see comments later in this paper, p. 44). Unrecorded occurrences are known to the writer in the late Eocene of Cuba and Peru, the Eo‑Oligocene San Fernando of Trinidad and the Lower Oligocene Codrington College marl of Barbados (in samples examined through the courtesy of A. Senn).

Globigerina dissimilis
Cushman and Bermúdez

Plate 25, figures 29‑31

Globigerina dissimilis Cushman and Bermúdez, 1937, Cushman Lab. Foram. Res., Contr., vol. 13, p. 25, pl. 3, figs. 4‑6.

A flattened globose form with four reniform chambers in the final whorl. The most distinctive feature is a supplementary chamber bridging the umbilicus. In many specimens, presumably microspheric, the embryonic portion is a minute Anomalina‑like group of chamberlets, totally unlike the adult form.

Prior to its original description from the Eocene of Cuba this species appears to have been identified as G. apertura from the Lower Oligocene Alazan of Mexico (Nuttall 1932, p. 29, pl. 8, figs. 1‑3). It has also been recorded from the Upper Eocene Hospital Hill and Lower to Middle Oligocene Cipero of Trinidad (Cushman and Stainforth 1945, pp. 8, 68, pl. 13, fig. 2). P. J. Bermúdez (private communication) states that it occurs in the Lower Oligocene of Cuba and the Middle Oligocene of the Dominican Republic. In Ecuador G. dissimilis first appears in the late Eocene and dies out in the late Middle Oligocene. As in Trinidad it ranges slightly higher than G. cf. concinna and its range in Colombia is the same, according to information supplied by C. D. Redmond.

Globigerina venezuelana Hedberg

Plate 25, figures 26‑28

Globigerina venezuelana Hedberg, 1937, Jour. Paleontology, vol. 11, p. 681, pl. 92, fig. 7.

A globose species, large for the genus, superficially like Globorotalia centralis with chambers high (side view) in relation to their width (radial). Dorsal spire slightly convex, usually with four chambers in the last whorl, meeting symmetrically and not overlapping as in G. centralis. In ventral aspect a large deep umbilicus is seen, ringed by the ventral extremities of the adult chambers, which are often coarsely granulose. Frequently the final chamber is abnormally small and in some specimens supplementary chamberlets are present between the principal chambers.

The type occurrence is in the Upper Oligocene Carapita of Venezuela. It is also recorded from the Upper Oligocene Cojimar of Cuba (D. K. Palmer 1941, p. 286) and the Lower to Upper Oligocene Cipero of Trinidad (Cushman and Stainforth 1945, p. 67, pl. 12, fig. 13), where it also ranges up into the Miocene. As indicated by Hedberg in his original description, this is probably conspecific with the Globigerina sp. (?) recorded from the Buff Bay Miocene of Jamaica (Cushman and Jarvis 1930, p. 366, pl. 34, fig. 5). C. D. Redmond (private communication) reports it from the Middle Oligocene (scarce) and Upper Oligocene of Colombia. In Ecuador G. venezuelana occurs sparingly in the early Oligocene but becomes the dominant pelagic species in the late Middle and Upper Oligocene, persisting up to mid‑Miocene.

A smaller, compressed, cuboidal form from the younger Oligocene and Miocene of Ecuador is considered to be a variety of G. venezuelana, although similar specimens have been recorded from the Upper Oligocene Cipero of Trinidad as G. inflata (Cushman and Stainforth, 1945, p. 67, pl. 12, fig. 12).

Globigerinatella insueta
Cushman and Stainforth

Plate 26, figures 16, 17

Globigerinatella insueta Cushman and Stainforth, 1945, Cushman Lab. Foram. Res., Spec. Pub. 14, pp. 68, 69, pl. 13, figs. 7‑9.

A very distinctive form, spherical with elongate supplementary chambers covering the sutures, and multiple apertures in the form of tiny lunate openings along the margins of these chambers.

This species has been recorded only from the Cipero of Trinidad, where its short life-range marks approximately the boundary between the Middle and Upper Oligocene. In Barbados it occurs in samples of the same age, examined through the courtesy of A. Senn. In Ecuador it is rarely encountered, although plentiful in the few samples which have yielded it, and all records are from the late Middle and early Upper Oligocene. These records suggest that Globigerinatella insueta should occur at comparable levels in the Venezuela‑Colombia region.

Globigerinoides triloba (Reuss)

Plate 26, figures 5, 6

Globigerina triloba Reuss, 1850, Denkschr. Akad. Wiss. Wien., vol. 1, p. 374, pl. 47, fig. 11; J. A. Cushman, 1946, Cushman Lab. Foram. Res. Contr., vol. 22, pt. 1, p. 20, pl. 4, figs. 16-18.

This form differs from G. sacculifera (see below) in the absence of bizarre final chambers, even in the largest specimens. It seems probable that G. sacculifera is an evolutionary offshoot from the ancestral G. triloba.

This species is recorded from the Miocene Port-au-Prince beds of Haiti (Coryell and Rivero, 1940, p. 340), and the Pliocene Charco Azul of Panama (Coryell and Mossman 1942, p. 238, pl. 36, fig. 29, 30). The same species was recorded as G. sacculifera, evidently either the young stages of this species or a primitive variety which has not developed the very long adult chambers, from the younger Oligocene Cipero of Trinidad (Cushman and Stainforth 1945, p. 68, pl. 13, fig. 3). It ranges well into the Miocene of Trinidad. In Ecuador it first appears in the late Middle Oligocene and is present in abundance throughout the Upper Oligocene and Miocene.

Globigerinoides sacculifera (Brady)

Plate 26, figures 7‑9

Globigerina sacculifera Brady, 1877, Geol. Mag., Dec. 2, vol. 4, p. 535. Brady, 1884, Rept. Voyage Challenger, Zool., vol. 9, p. 604, pl. 80, figs. 11‑17, pl. 82, fig. 4.

A squat trochoid species with large lunate apertures on both dorsal and ventral sides. Successive chambers roughly equal in size to all the preceding test. Chamber form at first regular, subglobular, but with maturity taking on bizarre bean‑ and kidney-shaped forms.

Specimens with these distinctive adult chambers have been described in the fossil state from the Miocene Choctawhatchee marl of Florida (Cushman 1918, p. 57), the Miocene Port-au-Prince beds of Haiti (Coryell and Rivero 1940, p. 340, pl. 42, figs. 24, 25, 32), the Miocene Bowden and Buff Bay beds of Jamaica (D. K. Palmer, 1945, p. 68; Cushman and Jarvis 1930, p. 366, pl. 34, fig. 4) and the Pliocene Charco Azul of Panama (Coryell and Mossman 1942 p. 238, pl. 36, fig. 28). This species also occurs in the Lower Miocene Lenuga of Trinidad as well as the Upper Oligocene of Colombia (C. D. Redmond, private communication). In Ecuador it is very scarce in the late Oligocene but becomes commoner through the early Miocene until at certain levels in the Middle and Upper Miocene it is present in flood abundance.

Globigerinoides rubra (d’Orbigny)

Plate 26, figures 11, 12

Globigerina rubra D’Orbigny, 1839, in Ramon de la Sagra, Histoire naturelle et physique de l’Ile de Cuba.

This species is distinguished from the triloba‑sacculifera suite by its lofty spire of almost globular chambers, four to each coil. Except in the juvenile stages the supplementary apertures on the dorsal face are large and prominent.

In the fossil state G. rubra has been recorded from the Miocene Bowden of Jamaica (D. K. Palmer 1945, p. 68), the Miocene Port-au-Prince beds of Haiti (Coryell and Rivero, 1940, p. 340), the Upper Oligocene Cipero and Lower Miocene Lengua of Trinidad (Cushman and Stainforth, 1945, pp. 9, 68). C. D. Redmond has stated in a private communication that in Colombia it is rare, ranging upwards from fairly high in the Upper Oligocene. In Ecuador it is not a common species but has been recorded throughout the Upper Oligocene and Miocene.

Globorotalia canariensis (d’Orbigny)

Plate 26, figures 30‑32

Rotalia canariensis D’Orbigny, 1839, in Barker, Webb, and Berthelot, Hist. Nat. Iles Canaries, vol. 2, pt. 2, p. 130, pl. 1, figs. 34, 35.

A species with obliquely overlapping chambers on the dorsal side, creating a lobulate outline, but almost straight radial sutures on the ventral side. Four to five chambers in the last coil. Periphery sharply defined but rounded, aperture small, ventral, at the base of the final chamber.

In the fossil state G. canariensis has been widely recorded from late Tertiary strata, for example the Aguide Oligocene of Venezuela (Cushman 1929, p. 101, pl. 14, fig. 14). the Miocene Port-au-Prince beds of Haiti (Coryell and Rivero 1940, p. 336, pl. 43, fig. 27), the Upper Oligocene of Ecuador (Galloway and Morrey 1929, p. 25), the Papantla Oligocene of Mexico (Dorr 1933, p. 435) and the Upper Oligocene Cipero of Trinidad (Cushman and Stainforth 1945, p. 70, pl. 13, fig. 12). The small form of the species persists into the Miocene of Trinidad. C. D. Redmond has noted this species in the Upper Oligocene of Colombia (private communication.) In Ecuador it ranges unobtrusively throughout the Upper Oligocene and the Miocene.

Globigerina digitata Brady

Plate 25, figures 22, 23

Globigerina digitata 1879. Quart. Jour. Micr. Sci., vol. 19, p. 286.

Species characterized by prolongation of the later chambers into thumb‑like shapes. The early chambers are compact and not readily discernible. There is no well-defined aperture, only gaping sutures on the ventral side. The shell is unusually thick and coarsely cancellate for the genus.

In Trinidad this species was recorded from the Upper Oligocene (Nuttall 1928, p. 96; Cushman and Stainforth 1945, p. 68, pl. 13, fig. 5). It is present in samples of the Upper Oligocene Cojimar of Cuba submitted to the writer by P. J. Bermúdez. In Ecuador it is rare, confined to the Upper Oligocene.

Candorbulina universa Jedlitschka

Plate 26, figure 33

Candorbulina universa Jedlitschka 1933, Verh. Nat. Ver. Brünn, 65J, 1934 (1933), p. 21, figs. 1‑7, 19, 21‑23.

A spherical form with trochoid nuclear portion usually visible. No main aperture present, but a ring of apertural pores near the margin of the final chamber.

Probably many of the records of Orbulina universa should be reidentified as this species. Definite records in America are from the Miocene of the eastern Coastal Plain of the United States, Panama and Venezuela (Cushman and Dorsey 1940, p. 42), and the Upper Oligocene and Miocene of Trinidad (Renz 1942, pp. 548, 556, 560; Cushman and Stainforth 1945, p. 69, pl. 13, fig. 10). In Ecuador the species ranges from late Oligocene through the Miocene and its range is the same in Colombia, according to a private communication from C. D. Redmond. Bilobed specimens are sometimes common, as figured by Cushman and Dorsey (1940, pl. 8, fig. 8).

Globigerinoides sp. indet.

Plate 26, figures 13‑15

This is a small species, readily distinguishable, but not completely identical with any figured species. The general form is a compressed quadrate trochoid, about as broad (radially) as high (side‑view). Chambers well inflated, increasing rapidly in size. The most prominent feature is the large main aperture, a gaping circular orifice on the ventral side of the last chamber. Supplementary apertures on the dorsal side are broad slits along the spiral suture, usually obscure except in adult specimens, rather than the lunate openings of most other species. There is a general resemblance to Globigerina apertura as figured by Cushman from the Miocene Yorktown of Virginia (1918, p. 57, pl. 12, fig. 8) but there is no indication of supplementary apertures in the original description of that species. There is also a resemblance to Globigerina adriatica as described by Fornasini from Recent material (1899, p. 582, pl. 3, figs. 6, 7, fide Ellis and Messina): G. adriatica is clearly a Globigerinoides and in dorsal aspect appears much like the Ecuadorian species, but the main aperture is by no means as conspicuous. D. K. Palmer (1945, p. 67, 68) has described as Globigerina bulloides a species from the Miocene Bowden of Jamaica “compactly coiled with 3 to 4 chambers in the final whorl; sutures deep; aperture conspicuous and subcircular … though they may be the young of G. rubra d’Orbigny no trace of multiple apertures has been noticed.” This description closely matches young specimens of the Ecuadorian species which differs from G. rubra in the shape of the supplementary apertures, the more rapid increase in chamber size and the more obtuse spire. It is a useful guide to Miocene age in Ecuador and is especially abundant in the Middle and Upper Miocene.

Sphaeroidinella dehiscens
(Parker and Jones)

Plate 26, figure 20

Sphaeroidina dehiscens Parker and Jones, 1865, Phil. Trans., vol. 155, p. 369, pl. 19, fig. 5.

A species with an ellipsoidal form, chambers and sutures conforming to its smooth contours. Only the last three chambers are clearly visible. Aperture a prominent “letter‑box” slit along the ventral margin of the final chamber. Shell rather thick, surface usually hyaline. There is some resemblance to Globigerina digitata, possibly an evolutionary relationship, but S. dehiscens is distinguished by its well‑defined aperture and the absence of any elongate chambers.

This species seems to be a guide to Miocene age on a regional scale, as shown by the following records in tropical America; the Buff Bay (Manchioneal) and Bowden of Jamaica (Cushman and Jarvis 1930, p. 367, pl. 34, figs. 6, 7; D. K. Palmer 1945, p. 69); the Port-au-Prince beds of Haiti (Coryell and Rivero 1940, p. 340), the topmost Cojimar of Cuba (D. K. Palmer 1940-41; see note on p. 44). In Trinidad it appears in and above the Lengua. In Colombia C. D. Redmond records Sphaeroidinella sp. as abundant in some Lower Miocene beds and scarce in the Upper Oligocene, but he does not regard it as typical S. dehiscens (private communication). In Ecuador it occurs throughout the Miocene, but has not been recorded from Oligocene samples.

Globorotalia menardii (d’Orbigny)

Plate 26, figures 36, 37

Rotalia menardii D’Orbigny, 1826, Ann. Sci. Nat., vol. 7, p. 273, no. 26, modèle no. 10.

A bi‑convex rotaliform species, somewhat compressed, usually with five but sometimes six chambers in the final whorl. Main character a very heavy ropy keel or rim of opaque shell material around the periphery.

There seem to be no authentic records of the typical heavy‑keeled form of this species in the pre‑Miocene of tropical America, though the ancestral lightly‑keeled G. praemenardii appeared in the late Oligocene. Nuttall recorded and figured typical G. menardii from the Lower Oligocene Alazan of Mexico (1932, p. 29, pl. 4, fig. 16), but he also included other species which hint at the accidental inclusion of some younger material in his collections (see comments below, p. 43). Miocene records include the Bowden of Jamaica (D. K. Palmer 1945, p. 70), the Port-au-Prince beds of Haiti (Coryell and Rivero 1940, p. 336, pl. 42, figs. 34, 35), the Miocene of St. Croix, V. I. (Cushman 1946-b, p. 13), the Quebradillas of Porto Rico (Galloway and Heminway 1941, p. 280), the Lengua and Brasso of Trinidad (Nuttall 1928, p. 101, pl. 7, fig. 20; Renz 1942, p. 556, 560; Cushman and Stainforth 1945, p. 9), the upper Agua Salada of Venezuela (Renz 1942, p. 553), the topmost Cojimar of Cuba (D. K. Palmer 1940-41, see comments below, p. 44), the Uscari of Costa Rica (K. V. W. Palmer, 1923, pp. 4, 9) and the Permenter’s Farm beds of Florida (Smith 1941, p. 273). C. D. Redmond states in a private communication that the heavy-keeled form first appears in the Lower Miocene of Colombia, except for rare specimens in the Upper Oligocene which could be referred to either G. menardii or G. praemenardii. It is also recorded from the Pliocene Charco Azul of Panama (Coryell and Mossman 1942, p. 234, pl. 36, fig. 5). In Ecuador G. menardii, together with Sphaeroidinella dehiscens, appears consistently just above the level at which Globorotalia barissanensis, Globigerina digitata and Globigerinoides conglobata become extinct. The time‑plane so marked is treated as the Oligocene‑Miocene boundary.

Globorotalia menardii (d’Orbigny)
vars. Fijiensis Cushman, and Multicamerata (?) Cushman and Jarvis

Plate 26, figures 38, 39

Globorotalia menardii var. fijiensis Cushman, 1934, Bernice p. Bishop Mus. Bull., no. 119, p. 36, pl. 16, fig. 5; Cushman and Jarvis, Jour. Paleontology, vol. 4, p. 367, pl. 34, fig. 8.

The specimens of G. menardii from Lower and early Middle Miocene samples in Ecuador are five‑ or rarely six‑chambered forms. In the late Middle and Upper Miocene this becomes outnumbered by specimens with from six to nine chambers in the final coil. Some of these are deeply umbilicate and closely similar to the variety G. menardii fijiensis described from the late Tertiary of Fiji and seen, by courtesy of B. Stone, in Upper Miocene samples from the Netherlands East Indies. The variety G. menardii multicamerata is not greatly different and it is interesting that this variety from the Buff Bay (Manchioneal) of Jamaica is not recorded from the slightly older Bowden (Middle Miocene) nor its presumed equivalent in Haiti, the Port‑au-Prince beds. This multicamerate form is known to the writer from beds in southwestern Colombia at the same levels as the Ecuadorian occurrence and it has been seen in Middle Miocene samples from the Dominican Republic, in the collection of B. Stone. Possibly the appearance of multicamerate G. menardii is regionally valuable in recognizing the late Miocene in the few areas of tropical America where there are neritic deposits of that age.

Pulleniatina obliquiloculata (Parker and Jones)

Plate 26, figures 21‑23

Pullenia sphaeroides var. obliquiloculata Parker and Jones, 1865, Royal Soc. London, Phil. Trans., vol. 155, pp. 365, 368, pl. 19, figs. 4a, b.

This species is coiled in an inflated trochoid with four or five chambers in the last whorl. The dorsal face is flattened, the ventral side moderately concave but non-umbilicate. The most characteristic feature is a tendency for successive chambers to overlap further over the dorsal face, thus approaching involute planispiral coiling. At least in the Ecuadorian specimens this final state is never reached, although the tendency towards it is clearly discernible. Other characters are the prominent lunate aperture, ventrally disposed, and the smooth polished surface of the test. In the original description similarity to Globigerina inflata is noted and a probable relationship is suggested by Cushman’s figures of topotype specimens of the latter species (1946‑a, p. 16, pl. 4, figs. 1‑4).

In the fossil state Pulleniatina obliquiloculata is recorded from the Pliocene Charco Azul of Panama (Coryell and Mossman 1942, p. 31, pl. 36, fig. 31) as well as the late Miocene and early Pliocene of the Netherlands East Indies (Leroy 1941, pp. 14, 18, 44, 45, 65, pt. 1, pl. 2, figs. 105-107; pt. 2, pl. 4, figs. 16-18). It is known from the Recent of the southern Pacific and B. Stone has shown the writer Recent material with typical specimens collected near Cuba. In Ecuador the species appears in moderate abundance in the neritic facies of the Upper Miocene.

Benthonic Smaller Foraminifera

In Upper Cretaceous and early Tertiary times, foraminiferal assemblages were constant over wide areas. In faunas of these ages the succession of genera and species is found to be much the same in localities thousands of miles apart. This is as true of the benthonic as of the pelagic species. In the middle and late Tertiary however, a pronounced provincialism affected the faunas and, with a few exceptions among the benthonic forms, only the pelagic species are reliable as time-markers in a regional sense. Among the bulk of the benthonic genera, evolution followed localized trends confined to individual basins and embayments. Under similar facies conditions very similar foraminiferal assemblages developed at different times in different areas. Great confusion can arise by failure to recognize these facts, which underlie the erratic age assignments published for several tropical American microfaunas. A typical case, cited not because it is unique but because the faulty argument is so clearly stated, is the correlation of the older Oligocene Alazan fauna of Mexico with the younger Oligocene faunas of Venezuela and Ecuador (Dorr 1933, pp. 434-438). Hedberg (1937, pp. 685, 695) has commented on this case and others.

In the list which follows only those benthonic Foraminifera are included which have limited ranges in Ecuador corresponding to their recorded distribution in tropical America. On the evidence so far accumulated these species can be regarded as time-markers as distinct from the many long-ranging species which indicate little beyond facies resemblance. They are listed and discussed in approximately their order of stratigraphic appearance. Levels of extinction are given as far as possible, but in some instances apparent extinction at the end of the Oligocene epoch in Ecuador may be only a reflection of the elimination of the local neritic facies at that time. The systematic arrangement of the species discussed is as follows:

Amphimorphina spp.

Plate 24, figures 9‑11

Several similar species of this genus have been described from the Upper Eocene of tropical America and the southern States, including A. lirata Cushman and Bermúdez from Cuba (1936, p. 2, pl. 1, figs. 6-8), A. ignota Cushman and Siegfus from California (1939, p. 27, pl. 6, figs 10-13) and A. yazooensis Bergquist from Mississippi (1942, p. 64, pl. 7, fig. 26). The species figured from the Upper Eocene of Venezuela as Plectofrondicularia mexicana appears to be a related form (Nuttall 1935, p. 127, pl. 15, fig. 6). In Colombia similar specimens are known from the upper Middle Eocene (C. D. Redmond, private communication).

In Trinidad specimens of Amphimorphina of the same general type occur in the Upper Eocene San Fernando formation and appear to evolve upwards into the early Oligocene forms referred to p. mexicani. In Ecuador the distribution is the same as in Trinidad.

Cibicides perlucidus Nuttall

Plate 25, figures 8‑10

Cibicides perlucidus Nuttall, 1932, Jour. Paleontology, vol. 6, p. 33, pl. 8, figs. 10‑12.

This species was originally reported from the lower part of the Lower Oligocene Alazan of Mexico and the Porto Rico record by Galloway and Heminway (1941, p. 251, etc.) seems to be from the same zone. The species has been recorded from Cuba and a similar form occurs in the Eocene marls of Trinidad. It has also been noted from the Middle Eocene of Oregon by Bandy (1944, p. 375, pl. 62, fig. 3). In Ecuador it is present in the late Middle and Upper Eocene and is often conspicuous in the basal Lower Oligocene, but it dies out abruptly at a horizon low in the Oligocene.

Uvigerina curta Cushman and Jarvis

Plate 24, figure 17

Uvigerina curta Cushman and Jarvis. 1929, Cushman Lab. Foram. Res., Contr., vol. 5, pt. 1, p. 13, pl. 3, figs. 13‑15.

Uvigerina Gallowayi Cushman

Uvigerina gallowayi Cushman, 1929. Cushman Lab. Foram. Res., Contr., vol. 5, pt. 4, p. 38, pl. 13, figs. 33, 34.

There is a species‑group of Uvigerina widespread in the Eo‑Oligocene of tropical America, characterized by lamellate costae on the earlier chambers. Typical representatives have been described as U. cubana Palmer and Bermúdez, U. curta Cushman and Jarvis, U. danvillensis Howe and Wallace, U. gallowayi Cushman, etc. The grounds for distinction between these allied forms have never been clearly expressed and the practice of figuring only one or two specimens fails to indicate the great range of variation within each species.

The Upper Eocene and early Oligocene forms in Ecuador tend to be relatively short and thick, with prominent flange‑like costae. They compare closely in morphology, range and variation with U. curta from the Eo‑Oligocene San Fernando of Trinidad. In the late Middle and Upper Oligocene a form appears which is equally variable but on average is more elongate, with more numerous and less flaring costae. This is referred to U. gallowayi Cushman, originally described from the Manta fauna as U. alata (Galloway and Morrey, 1929, p. 36, pl. 6, fig. 1). A private communication from C. D. Redmond reports similar distribution in Colombia. The U. gallowayi form has been locally recorded in the Miocene of Colombia but these specimens may have been reworked.

Uvigerina mexicana Nuttall

Plate 24, figure 18

Uvigerina mexicana Nuttall 1932, lour. Paleontology, vol. 6, p. 22, pl. 5, figs. 12, 13.

This species has been recorded from the Carapita Oligocene of Venezuela (Franklin 1944, p. 315, pl. 46, fig. 21), the Lower Oligocene Finca Adelina of Cuba (fide Franklin, loc. cit.) and, at its type locality, from the Lower Oligocene Alazan of Mexico. It occurs in the Lower and Middle Oligocene neritic facies of Trinidad. In Ecuador it is sometimes common in the Lower Oligocene and it occasionally ranges up into the Middle Oligocene. C. D. Redmond (private communication) states that its range in Colombia is Lower and Middle Oligocene. He mentions that its upper limit is close to that of Globigerina dissimilis, a fact which appears to be true regionally.

Uvigerina topilensis Cushman

Plate 24, figure 23

Uvigerina topilensis Cushman, 1925, Cushman Lab. Foram. Res., Contr., vol. 1, pt. 1, p. 5, pl. 1, fig. 5.

This species, characterized by its blunt elongate test and sparse continuous costae, seems to retain its distinctive form over wide areas. The types came from the Upper Eocene of Mexico and a similar form was recorded there from the Lower Oligocene as U. tenuistriata (Nuttall 1932, p. 21, pl. 5, fig. 8). Cushman recorded it from the Jackson Eocene of the Gulf Coast (1935, p. 41). In Ecuador this species has been noted only in Lower Oligocene samples.

Cibicides mexicanus Nuttall

Plate 25, figures 5‑7

Cibicides mexicanus Nuttall, 1932, Jour. Paleontology, vol. 6, p. 33, pl. 9, figs. 7‑9.

The types came from the lower part of the Lower Oligocene Alazan of Mexico. Cushman and Stainforth (1945, p. 73, pl. 15, fig. 5) record it from the Lower and Upper Oligocene of Trinidad, and mention its occurrence in the Eocene and Oligocene of Cuba, the Ponce of Porto Rico and the Eocene of Oregon. It should be noted that some variation in the amount of convexity was allowed in the Trinidad determinations (loc. cit.) and that the plano‑convex form as first figured is largely confined to the early Oligocene. In Ecuador this species is confined to the Lower and early Middle Oligocene.

Halkyardia sp.

Plate 25, figures 1, 2

This genus is often regarded as confined to the Eocene, although Galloway has referred to its occurrence in the Oligocene of Mexico (1933, p. 320). In Trinidad it is confined to the basal Oligocene in reefal facies, and it shows the same distribution in Ecuador. The Eocene records are from France, Dalmatia and New Zealand and it is possible that in the tropical American region it would be more correct to regard Halkyardia as an early Oligocene marker.

Rotalia mexicana mecatepecensis Nuttall

Plate 24, figures 27, 28

Rotalia mexicana mecatepecensis Nuttall, 1932, Jour. Paleontology, vol. 6, p. 26, pl. 4, figs. 11, 12.

Rugosity of the dorsal face distinguishes this variety from the original R. mexicana. In reefal facies of the Lower Oligocene of Ecuador there are abundant specimens apparently identical with Nuttall’s types from the Lower Oligocene Alazan of Mexico. It occurs also in neritic shales, but is scarcer and usually smaller than in the reef deposits. Thalmann has mentioned similar and correlative assemblages in western Colombia (private report) and it is recorded as locally abundant in the Oligocene Ponce of Porto Rico (Galloway and Heminway 1941).

Uvigerina rustica Cushman and Edwards

Plate 24, figure 25

Uvigerina rustica Cushman and Edwards, 1938, Cushman Lab. Foram. Res., Contr., vol. 14, pt. 4, p. 83, pl. 14, fig. 6.

This tuberculate species was based on specimens from the Aguide Oligocene fauna of Venezuela, first figured as U. hispida (Cushman 1929, p. 95, pl. 13, fig. 35), and it was considered identical with species earlier recorded from the Manta fauna of Ecuador and the Oligocene of Trinidad. Later authors have indicated that it occurs only in the younger Oligocene, and Miocene, as in Trinidad (Renz 1942, p. 546, 560; Cushman and Stainforth 1945, p. 47, pl. 7, fig. 13). The form described as U. hispida from the Lower Zemorrian to Lower Saucesian of California appears to be the same (Kleinpell 1938, p. 295, pl. 5, figs. 8, 16). H. H. Renz mentions its occurrence in the Lower Oligocene of Venezuela (private communication). Nuttall figured a similar form as U. auberiana from the Lower Oligocene of Mexico (1932, p. 21, pl. 5, fig. 7; see comments below, p. 43) and this is possibly the same as that listed by Dorr from the Oligocene of Nicaragua (1933, p. 436). Other records include the Cojimar of Cuba (D. K. Palmer 1941, p. 84, pl. 15, fig. 19), the Amoura of Costa Rica (Goudkoff and Porter 1942, p. 1652, 1653), the Oligo-Miocene of St. Croix, V. I. (Cushman 1946‑b, p. 9) and (?) the Papantla fauna of Mexico (Dorr 1933, p. 435). In Cuba and the Dominican Republic this species ranges from Upper Oligocene to Recent (P. J. Bermúdez, private communication). In Ecuador U. rustica first appears in the late Middle Oligocene and ranges up to the base of the Miocene. A similar form re‑appears in the late Miocene neritic facies.

Cibicides trinitatensis (Nuttall)

Plate 25, figures 11‑13

Truncatulina trinitatensis Nuttall, 1928, Quart. Jour. Geol. Society London, vol. 84, p. 97, pl. 7, figs. 3, 5, 6.

The types came from Trinidad, where the species occurs in beds of late Middle and Upper Oligocene age. Cushman (1946‑c, p. 40) mentions records from Upper Eocene to Miocene in other parts of the Caribbean region. In Ecuador it is plentiful in the late Middle and Upper Oligocene neritic facies, but is not known from higher or lower levels.

Pseudoglandulina comatula Cushman

Plate 24, figures 2, 3

Nodosaria Comatula Cushman 1923, U. S. Nat. Mus. Bull. 104, p. 82, pl. 14, fig. 5.

Hedberg recommended the use of this name for all the costate Pseudoglandulinas of the younger Oligocene, including the sparse‑ribbed specimens often separated as p. gallowayi. Forms which fall under this definition have been recorded from the younger Oligocene of Venezuela (Hedberg 1937, p. 673, pl. 91, figs. 9, 10; Renz 1942, p. 544; Cushman 1929, p. 87, pl. 13, fig. 13), Trinidad (Nuttall 1928, p. 84, pl. 4, fig. 23; pl. 5, fig. 3; Renz 1942, p. 546, 556; Cushman and Stainforth 1945, p. 27, pl. 4, fig. 3), Ecuador (Galloway and Morrey 1929, p. 13, pl. 1, fig. 7), Nicaragua (Dorr 1933, p. 436), California (Kleinpell 1938, p. 221), Cuba (Palmer and Bermúdez 1936), Porto Rico (Galloway and Heminway 1941, p. 338, pl. 11, fig. 2) and St. Croix, V. I. (Cushman 1946‑b, p. 5). C. D. Redmond describes its occurrence in Colombia as scanty but confined to the lower part of the Upper Oligocene (private communication). There are no records from the Miocene, and the only Lower Oligocene record is open to question (Nuttall 1932, p. 16; see comments below, p. 43). In Ecuador p. Comatula ranges from late Middle into early Upper Oligocene.

Robulus clericii (Fornasini)

Plate 24, figure 1

Cristellaria clericii Fornasini, 1895, Bologna.

This distinctive species has been recorded in the younger Oligocene and Miocene of Trinidad (Nuttall 1928, p. 87, pl. 5, fig. 10; Renz 1942, p. 557; Cushman and Stainforth 1945, p. 21, pl. 2, fig. 23), the younger Oligocene of Venezuela (Cushman 1929, p. 84, pl. 12, fig. 16, 17; Hedberg 1937, p. 669; Renz 1942, p. 554), the Oligocene of Nicaragua (Dorr 1933, p. 435, 436), the lower Zemorrian of California (Kleinpell 1938, p. 197), the Miocene of Haiti (Coryell and Rivero 1940, p. 332, pl. 43, fig. 7), the Miocene of Jamaica (D. K. Palmer 1945, p. 34), the Upper Oligocene of Cuba and the Miocene of the Dominican Republic (P. J. Bermúdez, private communication). In Ecuador the species becomes conspicuous in and ranges upwards from the late Middle Oligocene, but occasional specimens with the characteristic comma‑shaped chambers are known in the late Middle and Upper Eocene. The same seems to be true of its distribution in Colombia, according to C. D. Redmond, private communication.

Siphogenerina transversa Cushman

Plate 24, figure 21

Siphogenerina raphanus (Parker and Jones) transversus Cushman, 1918, C. S. Nat. Mus. Bull. 103, p. 64.

The types came from the Oligocene Culebra of Panama and the species is widely distributed in the late Oligocene and early Miocene of tropical America. Hedberg (1937, p. 677, pl. 91, fig. 18) recorded it from the Carapita of Venezuela and mentioned other occurrences in the Papantla fauna of Mexico, the Zemorrian of California, the Miocene of Colombia, the Tertiary of Trinidad and the Oligocene of Cuba. These records have been amplified in subsequent papers but no occurrences are known older than late Middle Oligocene, except for S. transversa var. cubensis from the Eocene of Cuba (Cushman and Bermúdez 1937, p. 16, pl. 2, figs. 8, 9). In Ecuador S. transversa ranges from late Middle Oligocene into the Miocene, and it has the same range in Colombia (C. D. Redmond, private communication). Its distribution is subject to facies control and it occurs in greatest abundance at the boundary of neritic and sub‑littoral facies.

Siphogenerina basispinata Cushman and Jarvis

Siphogenerina basispinata Cushman and Jarvis, 1929, Cushman Lab. Foram. Res., Contr., vol. 5, pt. 1, p. 13, pl. 3, figs. 4, 5.

This species was first described from the “Sagrina Beds” of Trinidad, currently considered Upper Oligocene. It has also been recorded from the upper Middle and Upper Oligocene Cipero of Trinidad (Cushman and Stainforth 1945, p. 49, pl. 8, fig. 3). It has been reported from the late Oligocene of St. Croix, V. I. (Cushman 1946‑b, p. 10) and occurs in the lower Upper Oligocene of Colombia (C. D. Redmond, private communication). In Ecuador it is also restricted to the younger Oligocene.

Siphogenerina multicostata Cushman and Jarvis

Plate 24, figure 22

Siphogenerina multicostata Cushman and Jarvis, 1929, Cushman Lab. Foram. Res., Contr., vol. 5, pt. 1, p. 14, pl. 3, fig. 6.

First recorded from the “Green Clay” of Trinidad, the range of this species was later given as upper Middle and Upper Oligocene at the same locality (Cushman and Stainforth 1945, p. 49, pl. 8, fig. 1), with reported occurrences in Venezuela, Cuba and Porto Rico. It has also been recorded from the Lower Miocene of Trinidad (Renz 1942, p. 560) the Zemorrian of California (Kleinpell 1938, p. 302, pl. 5, fig. 7), the Papantla Oligocene of Mexico (Dorr 1933, p. 435, and the late Oligocene of St. Croix, V. I. (Cushman 1946‑b, p. 10). In Ecuador it occurs only in the late Upper Oligocene.

Uvigerina carapitana Hedberg

Plate 24, figure 16

Uvigerina carapitana Hedberg, 1937, Jour. Paleontology, vol. 11, p. 617, pl. 91, fig. 20.

As defined by Hedberg, this species from the younger Oligocene of Venezuela was considered identical with forms from the young Oligocene of Panama, Trinidad and California. In Colombia the range seems to be through late Middle and Upper Oligocene (C. D. Redmond, private communication). In Ecuador the species has a short life‑range in the topmost Oligocene and is usually abundant in beds of that age near the inner margin of the neritic facies.

Bolivina costata d’Orbigny, and varieties

Plate 24, figures 14, 15

Bolivina costata d’Orbigny, 1839, Voyage dans l’Amerique Méridionale; Foraminifères. Strasbourg.

Specimens of Bolivina of this species-group are described from the Pliocene of California (Cushman 1926, pp. 41, 42, pl. 6, figs. 2, 3) but Kleinpell gives them scant attention in his discussion of the younger Tertiary of California. He refers only to B. cf. interjuncta from the Miocene (1938, p. 274). The variety B. costata dissimilis was described from the subsurface Miocene of Louisiana (Cushman and Ellisor 1939, p. 6, pl. 1, fig. 10). In Ecuador varieties of the B. Costata group begin to appear in the late Oligocene and persist through the Miocene. The same appears to be true in Colombia (C. D. Redmond, private communication). The varieties B. costata bicostata and B. costata interjuncta Cushman (loc. cit.) seem to be confined to Miocene beds in Ecuador.

Uvigerinella californica Cushman

Plate 24, figure 19

Uvigerinella californica Cushman, 1926, Cushman Lab. Forum. Res., Contr., vol. 2, pt. 3, p. 58, pl. 8, figs. 2. 5.

Types of this species were obtained from the Miocene of California and the range given by Kleinpell is upper Zemorrian to Luisian (1938, chart p. 150). This corresponds to its range in the sub‑littoral facies of Ecuador from late Oligocene to Lower Miocene. It is sometimes the dominant Species in the early Miocene sub‑littoral facies.

Uvigerinella obesa Cushman, and varieties

Plate 24, figure 20

Uvigerinella obesa Cushman, 1926, Cushman Lab. Foram. Res., Contr., vol. 2, pt. 3, p. 59, pl. 8, figs. 3, 7.

Forms which fall within the species‑group of U. obesa and include the variety U. obesa impolita have the same occurrence in Ecuador as U. californica (above). The occurrence of slightly different forms at different levels seems to be an effect of facies, as the order varies from one section to another. In California Kleinpell has given the range of U. obesa, sensu lato, as Saucesian to Luisian (1938, chart p. 151).

Palmerinella spp.

Plate 25, figure 4

This anomalinid genus, characterized by an elongate slit aperture, was first recorded as p. palmerae in Recent material from Cuba (Bermúdez 1934) and later reported from the Upper Miocene of Cuba. P. J. Bermúdez has kindly supplied the information that the same species also occurs in the Upper Miocene and Pliocene of the Dominican Republic. p. thalmanni is a related form from the basal Miocene of Ecuador (Stainforth and Stevenson 1946, p. 563, 564, pl. 86, figs. 7‑10). A very similar form submitted by P. J. Bermúdez came from the middle Mohnian of California. On present evidence the genus appears to be valid as a guide to Miocene and younger beds.

Bolivinita cf. quadrilatera
(Schwager)

Plate 24, figure 8

Textilaria quadrilatera Schwager, 1866, Novara Exped. 1857‑1859, Geol. Theil, vol. 2, pt. 2, p. 253, pl. 7, fig. 103, Vienna.

Although records of its occurrence go back to the Cretaceous there is scarcely any mention of this genus in the Tertiary of tropical America. Several new species were recorded from the Upper Miocene of New Zealand by Finlay but the name B. quadrilatera has most frequently been used for late Tertiary and Recent specimens. Leroy (1944, p. 84) reported it to be widely distributed in late Tertiary and Recent deposits of the Malay Archipelago, and B. Stone applies this name to a Recent species from Cuba (private communication). Specimens which occur abundantly in the neritic facies of the Upper Miocene in Ecuador, fall almost within the accepted variation of B. quadrilatera, differing mainly in their low angle of taper. They are absent from shallow marine and brackish sediments of similar age, which may account for lack of records in neighboring countries. B. angelina from the Pliocene of California differs in the more acute angle of overlap of its chambers (Church 1928, p. 265, text fig. 1). Because of the absence of such a conspicuous genus in slightly older faunas of the region it is reasonable to suggest that it may prove a useful marker for the young Tertiary.

Elphidium spp.

Plate 24, figures 4‑7

The genus ranges through the whole Tertiary, but Mio‑Pliocene records far outnumber those of the Eo‑Oligocene in tropical America. Although doubtless controlled by facies‑changes indicative of regional emergence, it is a fact of stratigraphic significance that brackish deposits with abundant Elphidium spp. and “Rotalia beccarii” became widespread only in late Miocene time. In Ecuador occasional specimens of Elphidium are known from the Upper Oligocene and early Miocene, but it is only in the Middle Miocene that the Elphidium‑“Rotalia” faunule appears.

Uvigerina peregrina parvula Cushman

Plate 24, figure 24

Uvigerina peregrina parvula Cushman, 1923, U. S. Nat. Mus. Bull. 104, pt. 4, p. 168, pl. 42, fig. 11.

In the late Miocene of Ecuador small specimens of Uvigerina appear in which the fine serrate ribs of the early portion break down to rows of spines and irregularly hispid surfaces on the later chambers. Such a form has been exactly figured from the Buff Bay beds of Jamaica (Cushman and Jarvis 1930, p. 363, pl. 33, fig. 11) but is not mentioned from the slightly older Bowden beds (D. K. Palmer 1945). There is some resemblance to U. pigmaea but most of the forms described under that name show a more abrupt change from costate to hispid decoration. U. joaquinensis from the upper Luisian of California may be a related species (Kleinpell 1938, p. 296, pl. 17, figs. 6, 10, 11). Cushman and Todd (1941, p. 51, pl. 14, figs. 14‑17) have questioned the correctness of the name applied to the Buff Bay specimens, but mention its occurrence in the Miocene of Panama.

LARGER FORAMINIFERA

There is scope for more detailed research on the larger Foraminifera of Ecuador, but on the basis of published literature and manuscript reports by D. L. Frizzell, A. Martinez, R. M. Stainforth and H. E. Thalmann the principal species are known to occur in the following succession:

Lower Middle Eocene

The San Eduardo limestone, known in isolated patches resting unconformably on basement rocks, carries a uniform fauna, as described by Vaughan (in Sheppard 1937, p. 156 et seq.; 1945, pp. 79, 104, 112). Sheppard (1937) used the name Guayaquil in a dual formational sense and the name San Eduardo is now used for the Eocene limestone as distinct from the Cretaceous cherts (see Thalmann 1946, p. 339; Sheppard 1946, p. 496, 497). Species which occur consistently in the San Eduardo are:

Discocyclina (Discocyclina) anconensis Barker

Discocyclina (Discocyclina) meroensis (W. Berry)

Discocyclina (Discocyclina) sheppardi Barker

Discocyclina (Asterocyclina) aff. rutteni Vaughan

At a single locality Amphistegina elliotti Cushman and Stainforth (1946) has been recorded, a form allied to A. lopeztrigoi from a comparable level in Cuba.

Upper Middle Eocene

Limestones, lithologically like the San Eduardo, and other slightly younger reefal facies mostly contain a very different fauna. This led at first to belief in a considerable age‑difference between the two faunas, but later it was suggested that a change in facies conditions, possibly lowering of water temperatures, was responsible. Very recently, limestone boulders collected by R. Walls in the Clay Pebble beds near Ancon have proved to contain an intimate mixture of the older and younger faunas. This is convincing evidence that no major hiatus separates the Middle Eocene orbitoid faunas. The younger assemblages contain no Discocyclina (Discocyclina) and only occasional Discocyclina (Asterocyclina), but are dominated by the genera Operculinoides and Helicolepidina. Species recorded include:

Discocyclina (Asterocyclina) aff. rutteni Vaughan

Lepidocyclina atascaderensis W. Berry

Lepidocyclina peruviana Cushman

Lepidocyclina r. douvillei Lisson

Lepidocyclina vichayalensis Rutten

Operculinoides floridensis (Heilprin) vars.

Operculinoides ocalanus (Cushman) vars.

Helicolepidina polygyralis Barker

Upper Eocene

Reefal facies are not conspicuously developed in the Upper Eocene of Ecuador, but occasional layers contain a fauna comparable in genera to the late Middle Eocene assemblages. The most diagnostic species is Helicostegina soldadensis and the genus Helicolepidina is absent. Locally Lepidocyclina peruviana is present in flood abundance.

Lower Oligocene

The early Oligocene is marked by faunas carrying Lepidocyclina yurnagunensis Cushman and L. undosa Cushman. Appearance of these species marks the base of the Oligocene in Cuba (R. H. Palmer 1945, p. 17) and in Trinidad (Renz 1942, p. 547, Cushman and Stainforth 1945, p. 10). There is a puzzling feature, however, in the abundance of Lepidocyclina (Pliolepidina) tobleri Douvillé which has been considered an established Upper Eocene marker whether regarded as a true species or a teratologic variant of L. pustulosa (see Vaughan and Cole 1941, pp. 66, 67). On all other evidence of Foraminifera, molluscs, barnacles, etc. the Ecuadorean beds in question are Oligocene.

Middle and Upper Oligocene

No reefal facies are known in Ecuador of late Lower and early Middle Oligocene age, but basal to various local transgressions in the later Oligocene are Lithothamnion‑limestones and reefal sands. In several of these, including its type locality, Miogypsina (Miolepidocyclina) ecuadorensis Tan is found in abundance, accompanied by Amphistegina spp. and in some instances Lepidocyclina (Nephrolepidina) sp. The age of these various beds is considered late Middle to early Upper Oligocene. The reefal facies is continuous to high in the Upper Oligocene but its younger portions contain only Amphistegina spp.

Radiolaria

Because of the wide extent of radiolarian facies in the sediments of Ecuador some attention has been paid to the stratigraphic ranges of the numerous species. It has been found that four different assemblages can be readily recognized, representative of the Upper Cretaceous, late Middle and Upper Eocene, Eo‑Oligocene sensu lato, and Lower Miocene. Locally the Cretaceous and Eocene strata include cherts which can only be studied in thin section, but it has been found that the diagnostic species can be recognized as well in sections as in washed residues. These studies have a definite practical value, for instance near Manta where similar, almost non-foraminiferal tuffaceous shales of Eocene and Lower Miocene age are exposed in close proximity. Stratigraphic diagnosis of samples has been successfully based entirely on their radiolarian content. Thalmann (1946‑b, p. 1285) reported species close to Porodiscus circularis Clark and Campbell and Cenosphaera veneris Clark and Campbell from the Upper Eocene of the Santa Elena Peninsula, indicative of correlation with the Upper Eocene of California. From material figured by Clark and Campbell (1942, pp. 12, 13, 47) the form Spongodiscus (Spongocyclia) communis Clark and Campbell seems close to a discoid radiolarian which occurs in abundance in the younger Eocene of Ecuador. It occurred consistently in the samples of Upper Eocene Kellogg and Sidney shales analyzed by Clark and Campbell, and it is quite distinct from the Miocene species Spongodiscus (Spongodisculus) gigas recorded in California by Campbell and Clark (1944, p. 27). A species typical of the Miocene in Ecuador closely resembles Acanthosphaera (Raphidocapsa) barbati Campbell and Clark (1944, p. 15) from the Miocene of California. The Ecuador Miocene faunas contain other members of the family Astrosphaeridae, not recorded in the Upper Eocene faunas of California (op. cit.). There is scope for more detailed research into the value of the fossil Radiolaria as age indicators with wide lateral ranges. Unfortunately very little progress has been made in systematic determination of the fossil Radiolaria of Ecuador.

Facies Considerations

The Tertiary sediments of Ecuador are representative of five distinct facies‑provinces, with some intermingling of characteristics in boundary areas. Four of the facies‑types are well known in a regional sense and can be compared with some accuracy to major bathymetric zones in the modern oceans. The fifth type is not so readily assessed, but some evidence is presented below for considering this radiolarian facies to be indicative of a cool water province.

Neritic facies

Since investigations of foraminiferal faunas first started in the central American region it has been recognized that as much of the similarity between faunas from different countries is due to facies‑identity as to age‑identity. While it has been established that numerous individual Foraminifera, some of them listed above, are valid as regional markers for limited time‑ranges, it cannot be denied that the following Eo‑Oligocene formations and others less fully described carry broadly similar faunas indicative of uniform and widespread facies conditions: BARBADOS, Bissex Hill; TRINIDAD, San Fernando (including “Bamboo Clay”) and lower part of Brasso; VENEZUELA, Pauji, Carapita and lower part of Agua Salada; ECUADOR, “Manta”; PANAMA, Tranquilla; COSTA RICA, Amoura; NICARAGUA, unnamed (Dorr 1933, p. 436); MEXICO, Chapapote, Alazan, “Papantla”; CALIFORNIA, Refugian (pro parte) and Zemorrian stages; GULF STATES, type Jackson and Vicksburg and various subsurface formation; CUBA, Cojimar; PORTO RICO, Ponce.

Features common to these formations are fine‑textured argillaceous lithology and very rich, uniform foraminiferal assemblages. It is generally accepted that this facies marked the continental shelf area between depths at which tidal and coastal influences affected ecology and depths at which photosynthesis became inoperative at the sea‑bottom owing to non‑penetration of sunlight. Archibenthic facies of the Globigerina‑ooze type are unknown in Ecuador, though some of the West Indian deposits on the fringe of the region do represent this deeper facies. The Hospital Hill and Cipero of Trinidad, the Oceanic of Barbados, and the Principe of Cuba may be cited as probably representative of the upper abyssal slope.

For the purposes of this paper the term neritic has been applied to the continental-shelf facies. In Ecuador various beds of Upper Eocene and Oligocene age can be referred to it. Also in the late Miocene there are remnants of a similar facies, comparable to the Bowden and Buff Bay beds in Jamaica and the Port‑au‑Prince beds in Haiti.

Sub‑littoral facies

Between the inshore limits of the neritic facies and the ancient strand‑lines the sediments are characterized by great variability. On average the sedimentary grade is coarser than in the neritic province and liable to rapid fluctuation both laterally and vertically. The faunas vary correspondingly. Though specimens of Foraminifera may be as abundant as in the neritic facies, the faunal lists are usually shorter and include not more than twenty or thirty species. Very often one species is numerically dominant in the assemblage, especially forms of the genera Bolivina, Uvigerina and Siphogenerina and of the subfamily Discorbinae. Molluscs and other megafossils play a more conspicuous role in these faunas than in the neritic facies.

Marine facies belonging to this group have been referred to the sub‑littoral facies, which is represented at different places in Ecuador by beds of Upper Eocene, younger Oligocene and Miocene age.

Reefal facies

Possibly reefs should be regarded as a special case of the sub‑littoral facies, though at times intimately connected with the shallower neritic facies. They can be divided into reef limestones and reef sands. The former are biochemical precipitates of lime in shallow tropical seas. In Ecuador algal-orbitoid limestones exist of Middle Eocene and younger Oligocene to basal Miocene age. The second type of reef deposit is of the sand‑bar type, characterized by coarsely clastic lithology and a rich fauna of specialized organisms, especially orbitoids and sessile forms. Such deposits are known in Ecuador of late Middle Eocene and Oligocene age.

Ranges of Some Tertiary Foraminifera in Coastal Ecuador

Species	Eocene	Oligocene			Miocene
Species	Eocene	Low.	Mid.	Up.	Low.	Mid.	Up.
Hastigerinella Eocenica	nnnnnnnn
Globigerina douvillensis	nnnnnnnn
Hantkenina alabamensis	——————
Stichocassidulina thalmanni	——————
Amphimorphina sp. lirata	——————
Globigerina wilsoni	nnnnnnnn——
Globigerina “triloculinoides”	————————
Bulimina jacksonensis	nnnnnnnn------
Cibicides perlucidus	—————nnnn
Uvigerina curta	nnnnnnnnnnnnn——
Globorotalia centralis	nnnnnnnnnnnnnnn
Globigerina cf. Concinna	------------------——nnnnn
Globigerina dissimilis	———————nnnnnnnn
Bulimina sculptilis	------nnnnnnnnnn-----
Halkyardia sp.	————
Rotalia mexicana mecatepecensis	nnnnn
Uvigerina topilensis	————
Cibicides mexicanus	nnnnn——
Uvigerina mexicana	nnnnn-----------
Globigerina venezuelana	--------———nnnnnnn——————
Globigerinatella insueta			———
Pseudoglandulina comatula			———
Globigerinoides conglobata			—————
Globorotalia barissanensis			nnnnnnn
Uvigerina gallowayi			—————
Cibicides trinitatensis			—————
Siphogenerina basispinata			—————
Siphogenerina transversa			nnnnnnn ---------------
Globorotalia praemenardii			———————————----
Uvigerina rustica			nnnnnnn ? —————
Robulus clericii	?		nnnnnnn--——————————
Globigerinoides triloba			——nnnnnnnnnnnnnnnnnn
Globigerinella aequilateralis			---------------nnnnnnnn—————
Elphidium spp.			---------------------------———————
Globigerina digitata			————
Globorotalia canariensis			--------------------------------------------
Globigerinoides rubra			--------------------------------------------
Candorbulina universa			nnnnnnnnnnnnnnnnnnn
Siphogenerina multicostata				———
Uvigerina carapitana				nnn
Uvigerinella californica				———nnnn
Uvigerinella obesa vars.				———nnnn
Bolivina costata vars.				———nnnnnnnnnnnnnn
Globigerinoides sacculifera				---------———nnnnn————
Palmerinella thalmanni				———
Globigerinoides sp. indet.				———nnnnnnnnnn
Sphaeroidinella dehiscens				———————————
Globorotalia mernardii				———————————
Globorotalia menardii vars.						nnnnnnn
Uvigerina pergrina parvula						nnnnnnn
Pulleniatina obliquiloculata						————
Bolivinita cf. quadrilatera							nnn

Fig. 2

Brackish facies

On the shoreward fringe of the marine environment low salinity due to river discharge or lagoonal conditions governs the specialized brackish facies. Because of the inevitable proximity of land, carbonaceous matter is usually conspicuous in the sediments, which tend to be of a variable but rather coarse littoral type. Organisms of many phyla have adapted themselves to this environment, the principal Foraminifera being Elphidium, the Miliolidae and the form usually referred to Streblus (“Rotalia”) cf. beccarii. In Ecuador there are local brackish-facies deposits in the Upper Eocene, the late Oligocene and the Miocene. Probably the Pliocene was a time of widespread brackish facies. but Plio‑Pleistocene chronology has not been accurately worked out.

Radiolarian facies

This name is applied to a distinctive facies which was recurrent from the mid-Eocene to mid‑Miocene in Ecuador. If only for its considerable local extent, at times dominating the whole marine environment, it deserves attention, but more significant is its affinity to various Thyasira‑bearing deposits in parts of the western seaboard of the United States. the conclusion reached in Ecuador is that this facies marked the path of cold ex‑polar currents comparable to the present‑day Humboldt drift. A subsidiary conclusion is that the vertical distribution of the molluscs Thyasira, Acila, Pleurophopsis, Vesicomya, etc. was governed by the existence of this cool‑water province and that this suite was well‑established in Upper Eocene time. It does not necessarily follow that same is true of the disputed Eo‑Oligocene in California, Oregon and Washington, but the parallelism is suggestive. The distinctive features of this facies are expressed below in a few objective statements, followed by inferential reasoning on which the above conclusions are based.

(1) The dominant lithologic type is finely tuffaceous shales, partly chertified, but conglomeratic sandstones may be interbedded as at Ancon Point and along the coast west of Manta. Most of the clastic sediments in Ecuador are tuffaceous to some degree, but those of the radiolarian facies are markedly so.

(2) The characteristic microfauna contains an abundance of Radiolaria with only few Foraminifera, the latter being usually of long‑ranging eurybathic species. An exception is the pelagic Hastigerinella eocenica which is rather common in the Upper Eocene radiolarian facies but scarce in synchronous neritic facies.

(3) The characteristic megafauna consists of a limited suite of molluscs typified by the genera Thyasira, Acila, Pleurophopsis, Vesicomya and Lucina. It is generally agreed that as a group these forms indicate a cold marine environment.

(4) This facies is always developed to the west, presumably ocean‑ward, of any normal marine facies existing at the same time. The lateral transition is abrupt in the faunal sense though not strongly marked lithologically. At different places and levels transition is seen into normal neritic, sub‑littoral, reefal and near‑brackish facies.

(5) Both the neritic and sub‑littoral facies in proximity to the radiolarian facies are abnormal in respect to pelagic Foraminifera. In some cases the sub‑littoral facies contains a phenomenal abundance of Globigerina, etc., whereas the neritic facies near its transition into the radiolarian facies is almost devoid of these normally abundant forms.

(6) The Tertiary basins of Ecuador preserved their general form from mid-Eocene to late Oligocene time, as shown by the paleogeographic distribution of the depth‑controlled facies already discussed. Paleogeographic maps show clearly that during times of co‑existence of normal and radiolarian marine facies the most normal marine facies existed to the north and east of major sea‑floor highs. “Normal” is used here in reference to overall frequency of Foraminifera and proportion of pelagic forms, as compared with similar facies in regions where the radiolarian facies was not developed. The eastern margin of the radiolarian facies ran tangential to and west of seafloor highs: normal marine facies were developed in the lee of these highs: intermediate areas contained transitional facies. abnormal (as under 5 above) in the distribution of pelagic Foraminifera or semi‑sterile.

(7) The maximum eastward extent of the radiolarian facies was reached at times of general subsidence, especially in Upper Eocene and early Miocene time.

On this evidence the radiolarian facies is not a bathymetric zone in the normal sense (from statement 4 above). The molluscan evidence indicates that low water temperature was a controlling factor (3), and this suggestion is supported by the abnormal distribution of pelagic Foraminifera (2, 5) since, as a whole, the pelagic Foraminifera favor warm waters (as in the Gulf Stream) and their inhibition or mass destruction at the fringes of the radiolarian facies can be taken as a sign of hostile cold conditions. The facts that the radiolarian facies-province included shallow water sediments (1) and that the pelagic as well as the benthonic Foraminifera were inhibited (2, 5) indicates that surface waters were cold. The development of normal tropical facies beyond the eastern limits of the radiolarian facies (4) indicates that the low temperatures can only be attributed to ocean currents. A parallel to the Humboldt current here suggests itself and receives confirmation by the limitation of normal marine facies to positions to the north and east of seafloor barriers and by the existence or influence of the radiolarian facies in unsheltered areas (6). Following this interpretation it would be natural for the cold province to encroach eastwards at times of subsidence (7) when physiographic barriers had been lowered, or in effect had retreated eastwards. The late Oligocene subsidence is not marked in northern Ecuador by eastward advance of the radiolarian facies, rather the reverse, a fact explained by deposition of a massive fan of late Eocene and early Oligocene sediments to the south.

Not explained in the above synopsis is the abundance of Radiolaria (2). Taliaferro (1943, pp. 147-150) has discussed comparable facies in the Franciscan-Knoxville of California, and has associated radiolarian cherts with excess of silica due to nearby volcanic activity. In the case of the Ecuador Tertiary beds the same explanation might appear feasible, as the growth of the Andes was accompanied by volcanic activity and most of the sediments are appreciably tuffaceous (see Sheppard 1937, p. 93; Thalmann 1946-b, p. 1285); but the existence of normal marine facies between the Andes and the belt-province of the radiolarian facies is an insurmountable objection. By the geosynclinal theory postulated by Olsson (1932, pp. 51-58) and earlier authors a Tertiary land-mass is assumed to the west, and volcanic activity in that area could be taken as the source of excess silica. This idea is tenable but it is more hypothetical than the cold-current theory and fails to account for the specialized molluscan suite and the peculiar disposition of the radiolarian facies. Also it would seem that any facies-province governed by the existence of a western land mass would move westwards during regional subsidence, whereas the reverse was true of the radiolarian facies. A much simpler explanation is that no other organisms could tolerate the low water temperatures (or secondary effects such as destruction of phytoplankton and elimination of photosynthesis) and hence the Radiolaria thrived in abundance. It is not certain that tuffaceous lithology was directly related to the biologic characteristics of the radiolarian facies, though the records from Oregon, California and Ecuador all point to some connection. Not to be overlooked is the pronounced effect of cold oceanic currents on the adjacent mainland. The product is arid desert and it is possible that the weathering products in such areas might differ from the clay colloids of moister areas.

Of the regional scale it may be observed that the marked change in direction of the South American coast‑line near Latitude 1° South reflects basement features of the type claimed above to have deflected the cold oceanic currents. The basement trend swings sharply from a northeasterly to a southeasterly direction, and areas to the south should clearly be less protected from north‑bound currents than areas to the north. This can be seen to be true for the Upper Eocene, when a faunally rich Hantkenina‑bearing neritic facies developed in sheltered patches in northern and central Ecuador, but is represented only by impoverished replicas in southern Ecuador and northern Peru. Also in the younger Oligocene there is a sharp line of faunal distinction between beds with the rich “Manta” (Caribbean‑type) fauna in central and northern Ecuador and the Heath‑type beds in southern Ecuador and northern Peru with a fauna recognizably related but relatively poor in species. The Thyasira-Pleurophopsis suite of molluscs is well known in the Heath of Peru (Olsson 1931, pp. 21, 22) but has never been found in beds of the same age in Ecuador.

In manuscript reports D. L. Frizzell has suggested cold‑water control to account for vagaries in the distribution of Discocyclina in the Peruvian Eocene. The suggestion matches the more generalized scheme of cold oceanic currents and can be applied to the abrupt disappearance of Discocyclina s. s. in the mid‑Eocene of Ecuador.

In Ecuador the radiolarian facies was in existence from late Middle Eocene to mid-Miocene time. During almost the whole of this period it extended east of the present coastline, the easternmost extent varying with paleogeographic changes. For a brief interval during the later Oligocene the facies receded west of the present coastline, but its presence can be deduced from a lack of pelagic Foraminifera in unsheltered parts of the neritic facies which replaced it.

TIME‑SPACE DISTRIBUTION OF BIOSTRATIGRAPHIC UNITS IN ECUADOR

The loose meaning attached here to a biostratigraphic unit is a bed which on faunal grounds can be determined as to age and facies. The purpose of this section is more to serve as a guide to collecting localities than to give a summary of paleogeography, except where necessary to substantiate statements on facies relationships. Some units are designated by a place name and a lithologic term. This does not suffice to define new formations and members, but in most cases the place name has been so used in private reports of the International Ecuadorian Petroleum Company and is suitable for retention in the future for further discussion of the stratigraphy of coastal Ecuador. Formation names introduced by Sheppard (1937) and still considered valid are used for the southwestern region.

Cretaceous

See Thalmann (1946) for a comprehensive summary.

(?) Early Tertiary

A thick series of indurated shales including sandstones and conglomerates underlies the Middle Eocene of southwestern Ecuador and is the principal outcropping formation of the Cerros de Estancia. Fossil evidence is almost negligible but a Lower Eocene age is commonly assumed because of its position between known Upper Cretaceous and Middle Eocene strata. Thalmann (1946-a, pp. 346, 347; 1946-b, p. 1235) considered the lower part of the series to be Paleocene, but there is no strong evidence against placing the whole unit in the Danian.

Lower Middle Eocene

The San Eduardo limestone, with its characteristic Discocyclina fauna, can most readily be examined at the quarries of the Fabrica de Cemento Nacional “Rocafuerte” a few kilometers west of Guayaquil. The limestone extends in strike prolongation from these quarries along the southern flank of the Cerros de Chongon. It pinches out some 40 km. west‑northwest of Guayaquil but reappears patchily on structural highs as far as the extreme north of the coastal area, e.g. Punta Ostiones. No other facies of the same age has been recognized.

Upper Middle Eocene

Reef facies

Limestones with the significant Discocyclina-Operculinoides‑Helicolepidina suite are only known as boulder remnants in the Clay Pebble beds. R. Walls drew attention to a concentration of this material near the narrow‑gauge railway‑cut just north of Ancon. The matrix of the Clay Pebble beds of the Ancon area and occasional sands in the Socorro contain a similar but slightly younger assemblage with no Discocyclina s. s. Elsewhere the same fauna occurs in the Javita limestone, developed patchily along the southwest flank of the Cerros de Colonche. Lithologically and by apparent strike prolongation the outcrops in several tributaries of Rio Nuevo are likely to be confused with the San Eduardo. Similar limestones, some with Helicolepidina polygyralis in rock‑forming abundance are known in the Manta area and on Rio Santiago in the north, but the exposures are obscure or difficult of access. The Punta Tinosa orbitoid grits, 12 km. west of Manta, are of the same age.

Marine facies

The Socorro formation of the south is of this age, but tends to carry undiagnostic arenaceous microfaunas except in its orbitoid facies. A radiolarian facies of the same age exists but is not readily distinguished from the more extensive developments in the Upper Eocene.

Upper Eocene

Upper Eocene deposits are widespread and readily segregated into facies‑types, so that for the first time an overall impression of facies relationships can be gained.

Neritic facies

A long strip of Upper Eocene beds in normal neritic facies is exposed along the upper courses of Rios Grande, Zapallo Grande and Santiago, major tributaries of Rio Cayapas, in northern Ecuador. These may be termed the Zapallo shales. No other surface exposures of the same type are known, but an identical subsurface unit has been encountered in the Manta area. In southern Ecuador the nearest approach to it is seen in the Hantkenina‑bearing Jusá shales exposed (under alluvium) some 15 km. E. S. E. of Colonche, and also known in subsurface. This southern facies is semi-sterile, strongly influenced by the radiolarian facies to the west.

Sub‑littoral and brackish facies

In the south, to the east of the Cerros de Estancia, the later Eocene was marked by an influx of clastic material. The sedimentation was variable and included formation of the Zapotal molluscan sands exposed along the eastern border of the Cerros de Estancia northwards from Zapotal, at Posorja at the mouth of Rio Guayas, and elsewhere. These sandstones are non‑foraminiferal, but associated shales known in subsurface yield shallow marine and brackish microfaunas.

Reefal facies

True reefal facies are scarce in the Upper Eocene, but the Salanguillo orbitoid sands exposed some 15 km. east‑northeast of Colonche yield almost a one‑species assemblage of Lepidocyclina peruviana. This development is on the same trend as the older San Eduardo and Javita limestones, from which it appears that the Eocene reef-facies fringed an old high and merged westwards into deeper water facies. Erosion has cut down to Middle Eocene levels, leaving only remnants of the Upper Eocene reefs. Around Punta Mambra on the south coast the Seca shales contain occasional layers with a Lepidocyclina‑Operculinoides‑ Helicostegina assemblage.

Radiolarian facies

In extent and uniformity the radiolarian facies dominated the Upper Eocene marine environment. The Seca as described by Sheppard and the San Mateo tuffaceous shales east of Punta Tinosa near Manta typify this unit. Farther north the beds have been chertified to a large extent and have been confused with the Cretaceous Guayaquil chert (see Thalmann 1946-a, pp. 343, 344). The basic fauna is a flood of Radiolaria and a few Hastigerinella eocenica and Globigerina wilsoni. There is a distinct tendency for gradation into a normal neritic facies, upwards as at Valdivia on the coast northwest of Colonche and in subsurface near Manta, and laterally eastwards between Ancon and Punta Mambra on the southern coast, in the Jusá shales, and between the Galera peninsula and the upper Rio Cayapas.

Lower and Early Middle Oligocene

Normal marine facies

Overlying the neritic Upper Eocene there is a belt of early Oligocene beds exposed along the upper courses of Rios Grande, Zapallo Grande and Santiago. The vicinity of Playa Rica on Rio Santiago is a good study area. These Playa Rica beds consist of alternating orbitoid sandstones, with a rich reefal fauna, and shales with a normal neritic fauna. Correlative beds are exposed to the north between Rios Verde and Maté, but there is no reefal element here and the neritic facies is semi‑euxinic, showing influence of the radiolarian facies to the west. In the whole of the northern Lower Oligocene there is a distinct tendency for transition upwards to radiolarian facies conditions. Farther south a single exposure is known of the Lower Oligocene reef facies, at Punta Mal Paso 4 km. west of Manta.

Brackish facies

The Zapotal depositional cycle of the south ended with brackish beds of presumed Lower Oligocene age. Because of differences in facies an accurate comparison cannot be made with the Playa Rica faunas, but the few specimens of Globigerina present, the appearance of Bulimina sculptilis in place of B. jacksonensis in slightly older beds, and other species unnamed but useful in local zonation all suggest an early Oligocene age. There are no good exposures of this unit but it is present consistently in the subsurface.

Radiolarian facies

The existence of this facies in the Galera peninsula might be assumed from the westward passage of typical Playa Rica to the semi‑euxinic facies on Rio Verde, and subsurface evidence substantiates this assumption. No surface exposures are available owing to the combined effects of pre‑Miocene and sub‑Recent erosion.

Mid-Oligocene

The tendency for the early Oligocene neritic facies to grade upwards into a radiolarian facies culminated in the local deposition of mid‑Oligocene tuffaceous shales between Rio Ostiones and the lower Esmeraldas. In unpublished reports the name Chumundé ash‑beds has been applied to these strata, from exposures on Rio Chumundé, a tributary to the Verde. They correspond in age to the brief hiatus marked by local unconformities at the base of the younger Oligocene formations. In the south, east of Cerros de Estancia, where the evidence is not destroyed by erosion, static non‑depositional conditions seem to have marked completion of the Zapotal cycle.

Late Middle and Upper Oligocene

In the northern area a brief mid‑Oligocene spasm caused uplift to the northeast, following which there was general subsidence of the whole of western Ecuador during the late Middle and Early Upper Oligocene. In this interval sub‑littoral sediments first transgressed the basinal margins and were in turn overstepped by neritic facies. In mid-Upper Oligocene isostatic equilibrium was achieved and the remaining Oligocene was marked by a process of basinal infill, with rapid westward advance of tongues of clastic sediments.

Neritic facies

The “Manta” fauna described by Galloway and Morrey (1929) is typical of the younger Oligocene neritic facies, and almost certainly came from Jaramijo Bay, 9 km. east of Manta. A better type area, because of the more complete section, centers on the town of Tosagua. The Rio Esmeraldas and its tributaries, such as the Viche, cut through extensive exposures of correlative beds. lithologically there is no difference between the Tosagua and Viche shales and their benthonic foraminifera are the same, but the Viche is much richer in pelagic forms. Pelagic Foraminifera also are abundant in similar shales between Manta and Jipijapa. As already mentioned, this peculiarity is related to shelter of the Viche and Jipijapa areas from the effects of cool currents.

In the south the shales overlying the Zapotal, exposed north and south of Dos Bocas, carry comparable neritic assemblages but faunal densities are lower and there is a rhythmic interbedding of almost barren tuffaceous shales, shales with dominantly arenaceous Foraminifera and shales with neritic facies assemblages. F. V. Stevenson, who made detailed studies of subsurface control sections, attributed this variability to periodic lowering of water temperatures. Owing to deep weathering it is difficult to locate surface exposures of rich foraminiferal material, though the unit is widely exposed in gullies and artificial cuts.

Sub‑littoral facies, including reef accumulations

The initial transgression of late Middle Oligocene sediments was marked in the north by sandy beds, partly conglomeratic, typified by an abundance of euhedral grains of volcanic minerals. Locally they contain Miogypsina‑Lithothamnion reefs. In late Upper Oligocene the process of basinal infill was initiated by deposition of very similar sediments, encroaching transitionally westwards over the neritic Viche shales. The final stage of basinal infill was deposition of fine-textured topset shales above the fans of foreset silts and sands, but this phase of sedimentation took place mainly in the Miocene. The older transgressive beds and the younger foreset beds of the north are usually referred to the Angostura formation, from a molluscan locality on Rio Santiago.

The lithologic and facies succession is much the same over the whole area east of Rio Esmeraldas, except that there are limits respectively to east and west of which the neritic and earlier sub‑littoral facies were not developed. In the time sense, however, a facies change which marks basal Miocene in one place may be low in the Upper Oligocene at another. The faunal succession at any point reflects the order of facies changes much more closely than the small age differences involved, and failure to appreciate this led to considerable confusion in early attempts at foraminiferal zonation. The difficulty was overcome by detailed attention to the ranges of pelagic Foraminifera.

Farther south a sub‑littoral facies of Angostura type is gradationally transgressive over the Tosagua shales. The Hacienda San Agustin, 20 km. north of east from Bahia, has been considered the type area. The San Agustin sands are clearly equivalent to the younger (infill‑phase) Angostura.

In southwestern Ecuador there are remnants of Miogypsina‑reefs which mark the initial transgression of the younger Oligocene. A well‑known locality is at San Pedro near Valdivia, the type locality for Miogypsina ecuadorensis Tan (see Barker 1932). A less-known locality marked by boulder-float remnants of a Miogypsina‑limestone lies around the trail between the two main tributaries of Rio Jusá, some 10 km. E. S. E. of Colonche.

Brackish facies

This facies was of negligible extent in the younger Oligocene, but is occasionally encountered in Angostura beds on the fringes of the northern basin.

Radiolarian facies

The Chumundé tuffaceous shales are succeeded abruptly by normal neritic Viche shales which continued to be deposited uniformly until late in Oligocene time. Sterile and euxinic conditions then began to appear in the Galera peninsula and Punta Ballena areas, but not farther east. As already discussed, the local absence of pelagic Foraminifera in the Tosagua shales is considered another indication of a cool water province in the west.

Lower and Early Middle Miocene

Remnants of the Oligocene neritic facies were rapidly obliterated by shallow marine sediments in the early Miocene. In the north the process of basinal infill continued as already indicated. The youngest foreset beds and a Siphogenerina‑rich facies transitional to the topset beds are generally early Miocene in age, but most of the early Miocene sediments belong to the topset beds, named the Onzole shales from excellent exposures along the upper course of the Onzole. Topset deposition had already started in the late Oligocene of the lower Cayapas area, but these Onzole shales become progressively younger towards the Galera peninsula where they overlie foreset beds of early Miocene age.

Farther south, in the Manta‑Tosagua region, there was evidently uplift and erosion at the end of Oligocene time, as the Onzole‑like Charapotó shales are locally unconformable on older beds. A sharp boundary can be drawn between radiolarian facies to the west and foraminiferal facies to the east within the Onzole and Charapotó shales along the present coastal strip. As in the Oligocene shales, pelagic Foraminifera are common to abundant in the Jipijapa and Onzole areas but lacking in the Tosagua area. In the early Middle Miocene of the Rio Onzole area the shales often contain floods of pelagic Foraminifera abnormal for a sub‑littoral to brackish facies, and these have been regarded as death‑assemblages on the fringe of a cold‑water province.

In southern Ecuador the subneritic facies of the Oligocene Dos Bocas shales graded upwards into shallow marine deposits which rapidly assumed brackish characters in the early Miocene. Subibaja and Zacachun, 60 km. due east of Guayaquil have been considered type areas.

The final stage of basinal infill in the north is seen in brackish beds with a “Rotalia”‑Elphidium assemblage, lithologically part of the Onzole shales of early Middle Miocene age. Outcrops are known at the headwaters of Rios Lagarto and Lagartillo which flow into the ocean near Punta Ostiones, and also farther south, on Rio Quinindé 35 km. south of the town of the same name.

Late Middle and Upper Miocene

Most sediments of this age are undistinctive brackish‑water deposits, but there was evidently substantial subsidence along the present coastline because a rich neritic facies developed. Remnants of these beds have escaped pre‑ and post‑Pleistocene uplift and erosion and can be studied along the coast between Charapotó and Jama, in the Galera peninsula, especially near Punta Gorda, and in other patches. A. Martinez (private report) has established four foraminiferal zones which appear to be valid over the whole known extent of this unit. Because of lithologic similarity this neritic facies is usually included in the Borbón silt, typified by weakly foraminiferal strata exposed on the lower Rio Onzole south of the town of Borbón.

Pliocene and Pleistocene

Shallow marine and brackish sediments on Puná Island carry Foraminifera of facies significance but little value in age determination. These and similar beds known under the thick alluvium of the Rio Guayas have been referred to the Pliocene on molluscan evidence. The Tablazo is a shallow marine deposit of Pleistocene age covering much of the present coastal fringe. It carries a very rich molluscan fauna but no Foraminifera of special age significance.

Regional Correlation

Despite the initial difficulties of distinguishing between the time‑elements and the facies elements in the Tertiary microfaunas, it has become steadily more apparent that, used judiciously, the fossil Foraminifera provide a reliable base for regional correlation in the central American region. The bottom‑living forms include numerous species and species‑groups restricted to the same limited life‑range over great areas. Earlier in this paper some evidence is given for believing that the planktonic forms are still more valuable because their distribution was scarcely affected by facies differences. Represented in Ecuador are five foraminiferal stages which can be recognized on a regional scale, as follows:

(1) An Upper Eocene stage: Upper limit marked by the extinction of Amphimorphina spp., Bulimina jacksonensis, Discocyclina spp. (s. l.), Globigerina danvillensis, Hantkenina spp., Hastigerinella eocenica, Helicostegina soldadensis.

(2) An earlier Oligocene stage: lower limit marked by extinction of the species listed above and by first appearance of Bulimina sculptilis, Globigerina venezuelana, Halkyardia sp., Lepidocyclina undosa, L. yurnagunensis: upper limit at or above the level of extinction of Cibicides perlucidus. Globigerina cf. concinna. G. “triloculinodes,” G. wilsoni, Globorotalia centralis, Halkyardia sp., Uvigerina curta, U. topilensis: species useful as guide‑fossils, but also ranging a short way into the next higher stage, are Cibicides mexicanus, Globigerina dissimilis and Uvigerina mexicana.

(3) A later Oligocene stage: lower limit above the level of extinction of species listed above and at or below the first appearance of Candorbulina universa, Cibicides trinitatensis, Globigerina digitata, Globigerinatella insueta, Globigerinella aequilateralis, Globigerinoides conglobata, G. rubra, G. sacculifera, G. triloba, Globorotalia barissanensis, G. canariensis, G. fohsi, G. praemenardii, Miogypsina spp., Pseudoglandulina Comatula, Robulus clericii, Siphogenerina basispinata, S. multicostata, S. transversa, Uvigerina carapitana, U. gallowayi, U. rustica, Uvigerinella californica, U. obesa: upper limit at or above the level of extinction of Cibicides mexicanus, C. trinitatensis, Globigerina dissimilis, Globigerinatella insueta, Globigerinoides conglobata, Globorotalia barissanensis, G. fohsi, Pseudoglandulina comatula, Siphogenerina basispinata, Uvigerina mexicana.

(4) A lower Miocene stage: lower limit marked by extinction of the species listed above and by first appearance of Globorotalia menardii, Sphaeroidinella dehiscens, Palmerinella spp.

(5) A younger Miocene stage: less clearly defined but typified by floods of Elphidium spp. and Streblus (“Rotalia”) cf. beccarii in the shallower water facies and by Bolivinita cf. quadrilatera. Uvigerina Peregrina parvula, multicamerate varieties of Globorotalia menardii and Pulleniatina obliquiloculata in neritic facies.

The master zonation in Ecuador is based on these species, and their order of appearance and extinction is so consistent in the published biostratigraphic literature of the Central American region that their value in zonation may be taken as empirically proved. The very few instances in which any of these species have been recorded out of position can fairly be called in question in face of the cumulative evidence of other areas. The only instances known to the writer are the following:

(a) The lower Oligocene Alazan fauna of Mexico, as described by Nuttall (1932), is a close equivalent of the Lower Oligocene Playa Rica of Ecuador and as a whole there is no question that the age was correctly given. There are, however, passing references to species which are regarded elsewhere as rigid markers for younger stages, including Cibicides trinitatensis (l. c., p. 33), “Uvigerina auberiana” (U. rustica) (p. 21), Pseudoglandulina comatula (p. 16) and Globorotalia menardii (p. 29). Also mentioned is Amphistegina lessoni, usually found in the younger Oligocene and Miocene. Dorr (1933, pp. 432, 433) listed the Foraminifera of what he called “a representative part of the middle and upper Alazan formation” from shale samples in the vicinity of Papantla, Vera Cruz, Mexico. This Papantla fauna contains none of the species listed by Nuttall as characteristic of the lower Alazan, but it does contain several species considered markers for the younger Oligocene foraminiferal stage (Globorotalia canariensis, Robulus clericii, Siphogenerina multicostata, S. transversa). Dorr was therefore probably right in correlating his Papantla fauna with the Aguide fauna of Venezuela and the Manta fauna of Ecuador, but wrong in correlating it with the true Lower Oligocene part of the Alazan. Hedberg (1937, p. 690) quotes Thalmann as mentioning “Papantla beds” referred to the Lower Miocene. The point seems to be fairly established that both older and younger Oligocene beds of similar facies are exposed in the general area of Tuxpan. From this it might follow that Nuttall’s material, while dominantly Lower Oligocene, accidentally contained a small amount of the younger material. The opinion of paleontologists with experience in the area would be useful in clarifying this important point.

(b) The fauna of the Carapita formation of Venezuela was discussed in detail by Hedberg (1937), who carefully assessed the facies problem before correlating the middle zone with the Upper Oligocene as this is generally understood. Later Franklin (1944) described the Carapita fauna from unspecified outcrops in the vicinity of Rio Oregano and without discussion of previous conclusions claimed a Lower Oligocene age by correlation with the Alazan of Mexico and the Finca Adelina of Cuba. Of the species listed above as stage‑markers on a regional scale Franklin listed the following: Robulus clericii (p. 309), Pseudoglandulina Comatula (p. 312), Uvigerina mexicana (p. 313), Globigerina concinna (p. 317) and Globigerinella aequilateralis (p. 318). Hedberg confirms the first two of these and refers to Globigerinella sp., but whereas he refers to a form tentatively assigned to Globigerina concinna as “fairly common”, the G. concinna figured by Franklin is described as occurring “only rarely”. Franklin’s form seems identical with G. cf. concinna of the present paper, but the discrepancy in frequency suggests that it is not the same as Hedberg’s unfigured form. Hedberg did not refer to Uvigerina mexicana in the Carapita but it occurs low in correlative beds in Trinidad. Apart from the species discussed above, Franklin’s distribution chart (pp. 302, 303) lists many long-ranging facies-controlled species and many that are simply Oligocene, no more typical of the older than of the younger stage. Still other species used as evidence of correlation with the Alazan are insufficiently distinct from younger Oligocene forms, examples being Gaudryina jacksonensis of the Alazan and Gaudryina jacksonensis irregularis Cushman and Renz of the Agua Salada, or Verneuilina mexicana of the Alazan and Verneuilina cyclostomata Galloway and Morrey of the Manta. In short Franklin’s evidence for Lower Oligocene age of the fauna he lists is unconvincing. Both Hedberg and Franklin have commented on the great thickness of the Carapita formation, and the bulk of Hedberg’s conclusions were based on the middle zone. It is possible that species such as Globigerina cf. concinna occur in the lower parts, but as a whole Franklin’s fauna does not differ appreciably from Hedberg’s and both represent the younger Oligocene.

(c) The Cojimar fauna of Cuba was treated by D. K. Palmer (1940-41) as a single zonal unit of Upper Oligocene age. It is noted, however, that in the accompanying distribution chart there appears to be a younger zone marked by the extinction of Globorotalia fohsi and the appearance of G. menardii and Sphaeroidinella dehiscens. In other areas this faunal change is treated as diagnostic for the base of the Miocene. This question has been discussed in correspondence with Mrs. D. K. Palmer and Dr. P. J. Bermúdez, who adhere to the view of an Upper Oligocene age, although Mrs. Palmer states “I still consider the Cojimar formation fauna to be late Oligocene in age with some evidence of transition to the Lower Miocene in its uppermost part.” Samples of the upper Cojimar kindly submitted to the writer by P. J. Bermúdez show no evidence of Miocene age. Heavy-keeled Globorotalia menardii is not apparent, though a form close to G. praemenardii is fairly common, whereas the Oligocene species Globorotalia barissanensis and Globigerina digitata are both present.

Turning to Ecuador, the Discocyclina fauna of the San Eduardo can be directly correlated with the Upper Scotland formation of Barbados on the evidence of abundant Discocyclina anconensis and the presence of Amphistegina of the A. lopeztrigoi group (A. senni in Barbados and A. elliotti in Ecuador). Vaughan (1945, p. 21) stated “The foraminiferal fauna of the Upper Scotland formation is obviously Middle Eocene, and it may be considered the type Middle Eocene larger foraminiferal fauna of America.” Vaughan also noted points of similarity between the faunas of the Upper Scotland, the Middle Eocene Guayabal and beds near Yecuatla in Mexico, and the Middle Eocene of Cuba and Florida.

The Operculinoides-Lepidocyclina-Helicolepidina assemblage of the Clay Pebble beds, Socorro sands and Javita‑type limestones is typified by Helicolepidina polygyralis, a form which Grimsdale considered Middle Eocene, ancestral to the Upper Eocene Helicostegina soldadensis (Barker and Grimsdale 1936, fig. 4, p. 244: Grimsdale in Vaughan and Cole 1941, p. 86). Berry recorded similar faunas from the Eocene of northern Peru (for references see Ellis and Messina, Catalogue of Foraminifera, Vol. 29, Bibliography, p. 17). In orbitoidal sands near Ancon occurs a species of Dictyoconus, a genus typical of the Eocene, usually Middle Eocene.

The Zapallo shales are typical of the Upper Eocene neritic facies of the region and contain such time‑markers as Amphimorphina spp., Bulimina jacksonensis, Globigerina danvillensis, Hantkenina alabamensis, H. brevispina and Hastigerinella eocenica. The foraminiferal assemblage as a whole can be compared with the Chapapote of Mexico (Nuttall 1930), the Tranquilla of Panama (Coryell and Embich 1937), the Pauji of Venezuela (Nuttall 1935), the San Fernando of Trinidad (Renz 1942), the Gulf Coast Jacksonian (Cushman 1935) and parts of the Refugian of California and Oregon (Kleinpell 1938, etc.). The reefal layers of the Seca are characterized by Helicostegina soldadensis, first recorded from the Upper Eocene of Trinidad and mentioned by Frizzell in unpublished notes on the younger Eocene of Peru. By local zonation based on Radiolaria and Foraminifera the Seca shales and San Mateo tuffaceous shales fall within the Upper Eocene foraminiferal stage. The presence of Hastigerinella eocenica and Globigerina wilsoni in these units and the presence of a Zapallo‑type assemblage high in the San Mateo near Manta are substantiating evidence. Stichocassidulina thalmanni is useful in correlating the Seca and San Mateo with the Chira of Peru, where this species also occurs within the life range of Hantkenina. Thalmann (1946-b, p. 1285) has correlated the radiolarian faunas with the assemblages of the Upper Eocene Sidney and Kellog shales of California.

In its neritic facies the Playa Rica fauna is five‑sixths identical with the Zapallo assemblage, but the differences are significant and show that the Playa Rica falls within the early Oligocene stage. The Upper Eocene markers disappear and in their place occur Bulimina sculptilis, Rotalia mexicana mecatepecensis, Uvigerina topilensis, etc. Globigerina wilsoni becomes scarce but G. concinna, G. dissimilis, G. ‘triloculinoides” and Globorotalia centralis are plentiful. In the reefal facies Lepidocyclina undosa, L. yurnagunensis, Halkyardia sp. and Cibicides perlucidus are locally common. Presence of the Upper Eocene Lepidocyclina (Pliolepidina) tobleri is an unexplained anomaly. There is a clearcut resemblance to the Lower Oligocene Alazan of Mexico (Nuttall 1930, not Dorr 1933) and also to the younger San Fernando of Trinidad, the Finca Adelina of Cuba and the Ponce (part) of Porto Rico.

The Viche and Tosagua shales are represented by the Manta fauna of Galloway and Morrey, first assigned to the Upper Eocene but later placed in the Miocene by Cushman (1929). Currently the fauna is accepted as typical of the younger Oligocene foraminiferal stage, closely comparable to those of the Carapita and lower Agua Salada of Venezuela, the lower Brasso of Trinidad, the Bissex Hill of Barbados, the Ponce (part) of Porto Rico, the Cojimar of Cuba, the Zemorrian of California, the Papantla beds of Mexico (Dorr 1933), the Amoura of Costa Rica, unnamed beds in Nicaragua (Dorr 1933) and others. Distinction from the older Oligocene and early Miocene is based on the faunal criteria already discussed. It is noteworthy that in southern Ecuador and northern Peru the similarity of the younger Oligocene faunas to this Caribbean assemblage is not so pronounced and becomes remote towards the end of the Oligocene epoch.

The sublittoral Angostura is equivalent in age to the neritic Viche and Tosagua, but the benthonic Foraminifera are entirely different. The distribution of pelagic Foraminifera is the same in both facies, Globigerina dissimilis vanishing and Globigerinatella insueta appearing near the base, Globigerina digitata, Globigerinoides conglobata and Globorotalia barissanensis disappearing near the top. The benthonic assemblages of the Angostura most resemble those which began to appear in the Zemorrian and dominated the Saucesian of California. Typical species are Uvigerinella californica vars. and U. obesa vars. There is a distinct resemblance, which becomes even more pronounced in the overlying Onzole, to Recent faunas dredged in the cold water province along the western coast of America (Cushman 1927).

The base of the Miocene falls within the older Onzole or the younger Angostura according to locality. It is marked by the disappearance of Globigerina digitata, Globigerinoides conglobata and Globorotalia barissanensis and by the appearance of Globorotalia menardii, Sphaeroidinella dehiscens and, locally, Palmerinella thalmanni. The disappearance of benthonic species typical of the Tosagua and Viche shales is partly of regional significance but is also partly due to the complete elimination of the neritic facies in Ecuador at the end of the Oligocene, as in the cases of Siphogenerina multicostata and Uvigerina rustica. Regionally these changes in pelagic Foraminifera correspond to the Oligocene‑Miocene boundary in Venezuela, Trinidad, Colombia and possibly Cuba (see note above). True G. menardii has been recorded only from the Miocene in Jamaica, Haiti, Florida and Panama. In northern Ecuador the base of the Miocene is often marked on the surface by an assemblage with floods of Siphogenerina transversa, but this belongs to a specialized facies intermediate between foreset and topset beds and, like them, varies in age according to locality.

There is a general faunal similarity between the Onzole and Charapotó of Ecuador and the Saucesian‑Relizian of California. Species of Bolivina are numerous and might prove applicable to detailed correlation between the Californian and Ecuadorian Miocene. The abundance of Valvulineria spp. and Bolivina spp. is reminiscent of the Recent faunas dredged off the west coast of America (Cushman 1927) and supports the conclusion that a cool-water province was a long-standing feature of the West Coast Tertiary marine environment. This may account for faunal differences between the western fringe and the eastern part of the Caribbean region.

In sublittoral facies the younger Miocene Borbón silt of Ecuador contains an impoverished assemblage of Onzole type, with few new species. One of these is Bolivina cf. hughesi, a marker for the upper Mohnian in California (Kleinpell 1938, pp. 138, 273). C. D. Redmond (private communication) drew attention to this species at a similar level in southwestern Colombia. Of more general interest is the neritic younger Miocene, which in Ecuador carries a fauna reminiscent in a general way of the Viche and Tosagua, though differing considerably in species. The Bowden and Buff Bay (Manchioneal) beds of Jamaica are closely similar, and it is especially significant that multicamerate Globorotalia menardii vars. only appear in the younger beds of Jamaica (see Cushman and Jarvis 1930, p. 367, pl. 4, fig. 8 and D. K. Palmer 1945, pp. 8, 9, 70). This is also true of Ecuador. The Port-au-Prince beds of Haiti are closely similar, but contain only the normal form of G. menardii (Coryell and Rivero 1940, p. 336). The Bowden and Port-au-Prince beds are usually considered late Middle Miocene, the Manchioneal as Upper Miocene. The Pliocene Charco Azul of Panama (Coryell and Mossman 1942) carries a similar fauna, Pulleniatina obliquiloculata and Uvigerina peregrina parvula being only two of several species typical of the young neritic Miocene in Ecuador. The importance of comparison of these late Miocene Antillean and Ecuadorian faunas lies in their bearing on the time of closure of the Central American land barrier. The pronounced similarity indicates that the barrier was not closed in late Miocene time, or else had not been closed long enough for evolutionary divergence of Pacific and Caribbean stocks.

Bolivinita cf. quadrilatera appears only in the youngest neritic Miocene of Ecuador and except for B. angelina from the Lower Pliocene of California there seem to be no other records at comparable levels in the Caribbean region. It is not established whether the absence of the genus in the West Indian faunas is of age‑significance or whether this is yet another sign of a cool facies confined to the west coast of America. Molluscs closely associated include plentiful Lucinoma, according to a private communication from A. A. Olsson, who also states that this is a cold water genus.

Molluscan Faunas

The time terms used in the foregoing portions of this paper are part of what may be called the foraminiferal time‑scale. Vaughan and others have given a concrete backing to this biochronologic framework with their studies of the evolutionary development of the larger Foraminifera. In a more empirical manner Hedberg, Kleinpell and many others have provided the base for an equivalent zonation based on smaller Foraminifera. The main purpose of the present paper has been to show that the Tertiary microfaunas of Ecuador conform with the accepted succession of foraminiferal stages. Parallel studies of molluscs have led to the recognition of a succession of key species, genera and assemblages applicable to the definition of different time-levels within the Tertiary. In Ecuador A. A. Olsson has made extensive studies of the molluscan faunas and within close limits his statements on local and regional correlation have matched the conclusions based on Foraminifera.

There is some divergence of opinion regarding the application of the standard European time terminology of the molluscan specialists and by the Foraminifera specialists. This dual chronology has been discussed elsewhere (e.g. in Schenck and Childs 1942, pp. 54-63; Weaver et al., 1944) and has arisen as a natural result of the difficulties of direct correlation between the European and American Tertiary. In general the molluscan faunas tend to be determined as slightly younger than synchronous foraminiferal assemblages, but no confusion need arise provided the duality and non-absolute nature of the time-terminology be recognized.

As mentioned above, equivalent molluscan and foraminiferal assemblages have been given closely similar age assessments in Ecuador. There is agreement, for instance, that the Playa Rica is early Oligocene, the uppermost Angostura Lower Miocene and the youngest neritic Borbón (at Punta Gorda) late Miocene. There is, however, one instance in which agreement has not been reached and the discrepancy needs to be clarified because the same molluscan fauna is the sole criterion of age of certain formations in Colombia and Venezuela. This is the assemblage first described from the Mancora of northern Peru and the equivalent Zapotal of Ecuador (Olsson 1931). More recently it has been referred to as the Hannatoma-fauna in the Barco Concession of Colombia (Notestein , et al. 1944, pp. 1199-1201). Olsson has consistently claimed a Middle Oligocene age for these molluscs, but in Ecuador they occur below shales which fall in the Upper Eocene foraminiferal stage. Put very briefly the cogent points raised in the contradictory age-assessments are:

Mollusca: In Peru the evolutionary development of Venericardia planicosta reached completion in the Saman. This is taken to mark the end of the Eocene epoch, hence the overlying Chira is Lower Oligocene (Olsson 1928, pp. 12-14; 1931, pp. 4, 6). The Mancora overlies the Chira: The Mancora-Zapotal fauna as first described was almost entirely new, but significance was attached to the presence of Ampullinopsis spenceri, previously recorded from the Antigua formation, and a Middle Oligocene age was claimed (Olsson 1931, p. 26). Unpublished notes by Olsson and J. G. Marks have since established that the species is nearer the Vicksburg A. mississippiensis.

Foraminifera: The Zapotal group is a complex of shallow marine to brackish sediments. In subsurface, sands correlative with the type Zapotal sands and carrying the same Mancora‑Zapotal molluscs are consistently present below shales with a rich foraminiferal fauna including such species as Bulimina jacksonensis, Globigerina danvillensis, Hastigerinella eocenica and, in one instance, Hantkenina alabamensis. This is direct evidence of an Upper Eocene age by accepted foraminiferal biochronology. Higher in the section, well above the youngest Mancora‑Zapotal molluscs, the Eocene‑Oligocene boundary is marked as usual by the evolutionary change from Bulimina jacksonensis to B. sculptilis. Stone (1946) mentioned Hantkenina in the Chira of Peru, as evidence that it is Upper Eocene in the foraminiferal time‑scale.

These are the most direct lines of argument, but there is indirect evidence which can be used to support either conclusion. For instance the sandstones at Ancon Point, Punta Mambra and elsewhere in the south are broadly correlated with the Zapotal on field evidence. They contain a molluscan suite of Thyasira, Acila, Pleurophopsis, etc. which can be considered Oligocene by reference to the Californian succession; but on the other hand shales interbedded with and overlying these sands contain Hastigerinella eocenica and Radiolaria locally diagnostic of the foraminiferal Eocene. In the subsurface at Manta a rich Hantkenina‑fauna appears at a much higher level than the local occurrence of the molluscs cited. Near Valdivia J. G. Marks has an unpublished record of Tubulostium sp. at a higher level than these molluscs.

To the extent that the units of the European time-scale are terms of convenience when applied in South America, the question of which age-determination is correct cannot be resolved; but it is essential for clarity that the terminology used in a regional correlation should be uniformly based on either the molluscan or the foraminiferal time-scale. In the excellent papers by Notestein et al. (1944) on the Barco Concession and by Sutton (1946) on the Maracaibo Basin, the upper Carbonera and the La Victoria formations are identified as Middle Oligocene on the strength of their contained Hannatoma-faunas. By field relations the almost barren Bebedero, Icotea and El Fausto formations are similarly referred. On the other hand the Pauji is assigned to the Upper Eocene by Sutton, on account of its foraminiferal fauna. The Pauji Foraminifera as described by Nuttall (1935) show it to be an exact equivalent of the Zapallo of northern Ecuador and other units mentioned earlier as characteristic of the neritic facies of the ‘Upper Eocene foraminiferal stage. The shales overlying the Zapotal molluscan sandstones belong to a shallower marine facies but are unequivocably placed also in the Upper Eocene foraminiferal stage. It is therefore anomalous to refer the upper Carbonera, etc. and the Pauji to considerably different zones. Some elasticity may be allowed because the Hannatoma‑fauna is largely facies‑controlled, indicative of semi-brackish conditions, and some of its components may be long‑ranging, but within close limits the Upper Eocene foraminiferal stage as generally accepted should be treated as synonymous with the Middle Oligocene of the Peruvian molluscan time‑scale.

References

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—, and Todd, R., 1941, Species of Uvigerina occurring in the American Miocene: idem, vol. 17, pp. 43‑52.

Detling, M. R., 1946. Foraminifera of the Coos Bay Lower Tertiary, Coos County, Oregon: Jour. Paleontology, vol. 20, pp. 348‑361.

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Garrett, J. B., 1939, Some Middle Tertiary smaller Foraminifera from subsurface beds of Jefferson county, Texas: Jour. Paleontology, vol. 13, pp. 575-579

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Journal of Paleontology

APPLIED MICROPALEONTOLOGY IN COASTAL ECUADOR

INTRODUCTION

AGE‑SIGNIFICANT FORAMINIFERA

Pelagic Species

Benthonic Smaller Foraminifera

LARGER FORAMINIFERA

Lower Middle Eocene

Upper Middle Eocene

Upper Eocene

Lower Oligocene

Middle and Upper Oligocene

Radiolaria

Facies Considerations

Neritic facies

Sub‑littoral facies

Reefal facies

Brackish facies

Radiolarian facies

TIME‑SPACE DISTRIBUTION OF BIOSTRATIGRAPHIC UNITS IN ECUADOR

Cretaceous

(?) Early Tertiary

Lower Middle Eocene

Upper Middle Eocene

Reef facies

Marine facies

Upper Eocene

Neritic facies

Sub‑littoral and brackish facies

Reefal facies

Radiolarian facies

Lower and Early Middle Oligocene

Normal marine facies

Brackish facies

Radiolarian facies

Mid-Oligocene

Late Middle and Upper Oligocene

Neritic facies

Sub‑littoral facies, including reef accumulations

Brackish facies

Radiolarian facies

Lower and Early Middle Miocene

Late Middle and Upper Miocene

Pliocene and Pleistocene

Regional Correlation

Molluscan Faunas

References

APPLIED MICROPALEONTOLOGY
IN COASTAL ECUADOR