Vol. 90, No. 6, November-December, 1953

The Miocene/Oligocene Boundary and the Use of the Term Aquitanian

By F. E. Eames[1]


It is considered that some fossils, e.g. Orbulina and Miogypsina, are good indicators that beds containing them are of post-Oligocene age, and that the ages of some beds in certain parts of the world require reconsideration; mention is made of successions in Morocco, Venezuela, and Peru. It is recommended that the use of the term “Aquitanian” be restricted to beds of basal Miocene age.

For many years it has been apparent that the term “Aquitanian” has been used in different senses and for rocks of different ages. Some writers use it for beds of basal Miocene age, and some for beds of Upper Oligocene age; to the latter school belong many Continental and American workers. Since the term has been applied to beds with either Miocene or Oligocene faunas, great confusion has arisen in literature. Furthermore, certain useful Miocene index-fossils have had their ranges unjustifiably extended down into the Oligocene, and much useful information is in danger of being lost.

Haug (1908-1911) showed that, in its type area, the beds constituting the Aquitanian form the basal component of the first Mediterranean transgression; the fauna is obviously related to the overlying Miocene beds (a number of significant species being in common), and is not to be grouped with the Oligocene. Durham (1944) suggests that an earlier use of the term applies to beds near Ajoie in Switzerland, which are now believed to be of Chattian age. Dehm (1949) and Rutsch (1951) cast doubt upon this interpretation. It seems to the writer that, just as the type section for the Bartonian must be in the Hampshire Basin and not in the Paris Basin (the sense in which some authors are prone to use it), so the type section for the Aquitanian must be in Aquitaine and not in Switzerland; it seems an ideal case for applying the palaeontological principle of “tautonymy”, and regarding the earlier (Oligocene?) use as a “nomen nudum”, especially as there appear to be doubts of interpretation.

Some authors, e.g. Gignoux (1950), place the Aquitanian in the Upper Oligocene on account of the nature of the vertebrate fauna in equivalent terrestrial beds. Quite apart from the facts that the evolution of the vertebrate faunas is not pertinent and that the stages of the Tertiary are primarily based on marine faunas, there can be no question that the type Aquitanian of Aquitaine must be regarded as basal Miocene.

A few cases of evident misinterpretation of age will now be considered.


Brönnimann has described species of Miogypsina from beds in Morocco called Chattian and Aquitanian (regarded as Upper Oligocene). A study of his paper reveals that, while his palaeontological descriptive work is excellent, he has made no analysis of the evidence, and accepts the age-indications given by Senn (1935) who wrote the earlier stratigraphical paper. Senn, without assessing the evidence, gives the following succession:

Age Suggested







Burdigalian (Lepidocyclina tournoueri, Miogypsina irregularis, M. sp., Amphistegina).



Aquitanian (Lepidocyclina tournoueri, Miogypsinoides [Miogypsina] complanata, Miogypsina irregularis).


Chattian (Nummulites—very small and rare, Operculina, Heterostegina, Amphistegina, Lepidocyclina tournoueri, L. tournoueri var. simplex, L. marginata var. praemarginata, L. dilatata, L. dilatata var. eodilatata, Miogypsinoides [Miogypsina] complanata, Miogypsina irregularis).



Rupelian (Nummulites—small striate forms, Operculina, Heterostegina, Amphistegina, Lepidocyclina tournoueri, L. tournoueri var. simplex, L. tournoueri var. praetournoueri, L. marginata, L. marginata var. praemarginata, L. partita, L. dilatata, L. dilatata var. eodilatata, L. raulini).



Lattorfian (Nummulites—small striate forms, N. cf. fichteli, Operculina, Heterostegina, Amphistegina, Lepidocyclina tournoueri, L. tournoueri var. simplex, L. marginata, L. marginata var. praemarginata, L. partita, L. dilatata, L. dilatata var. eodilatata).





(= Wemmelian)



Wemmelian (c) (Nummulitesincrassatus, N. fabianii, Hantkenina).

(b) (Nummulites—small, striate, N. cf. fabianii, Operculina, Heterostegina, Discocyclina pratti, D. nummulitica, D. strophiolata, Asterocyclina stellaris, Aktinocyclina cf. radians, Lepidocyclina tournoueri var. praetournoueri, Hantkenina alabamensis, Bulimina jacksonensis, Baculogypsinoides tetraedra.)

The uppermost Eocene age of the Wemmelian beds is perfectly satisfactory. The Discocyclinas, Nummulites fabianii, Hantkenina, Asterocyclina, and Aktinocyclina are a typical uppermost Eocene suite, with which small simple Lepidocyclina (Nephrolepidina)[2] are sometimes associated. There is a marked palaeontological break between the Wemmelian and the so-called “Lattorfian”, Discocyclina, Asterocyclina, and Hantkenina becoming extinct, and Nummulites, cf. fichteli and a new suite of Lepidocyclinas suddenly appearing. To the writer this strongly suggests that the Lattorfian (approximately) is missing, and that the so-called Moroccan “Lattorfian” is really Rupelian. The so-called “Rupelian, with small striate Nummulites but no reticulate forms is apparently Chattian.

It seems that the so-called “Chattian” and Aquitanian are both of Aquitanian (Lower Miocene) age, since both contain Miogypsina. It is my opinion that the “very small and rare” “Nummulites” from, the “Chattian” are almost certainly not Nummulites, but probably Operculinella.[3] The presence of Miogypsina in the beds referred to the Burdigalian is quite consistent with such an age.


Senn (1935) has recorded the following succession from north-west Venezuela:

Age Suggested



U. Miocene


U. Miocene La Vela Formation (Mollusca).

M. Miocene


M. Miocene Damsite Formation (many mollusca, Miogypsina, Amphistegina, Heterostegina, Sorites, Bolivina, Spiroloculina, Clypeaster).


L. Miocene Socorro Formation (Turritella abrupta).

U.U. Oligocene Cerro-Pelado Formation (Lepidocyclina, Miogypsina).


L.U. Oligocene Aguaclara Formation (Shales with local basal conglomerate) (Lepidocyclina, Miogypsina staufferi, Cristellaria calcar, C. clericii, Spiroclypeus, ? Lepidocyclina cannellei, Heterostegina, Amphistegina).

M. Oligocene San Luis Formation.

U. San Luis Formation (limestone) (Lepidocyclina sanluisensis, L. cf. antiguensis, L. cannellei, L. forresti, Miogypsina hawkinsi, Nummulites-rare and small, Heterostegina cf. antillae, Spirocylpeus).

M. San Luis Formation (shale) Lepidocyclina, Nummulites-rare and small, Miogypsina).

L. San Luis Formation (shale and limestone) (Lepidocyclina, L. cf. marginata, L. undosa, L. favosa, Miogypsina, Nummulites-rare and small, Spiroclypeus, Heterostegina).



L. Oligocene Churuguara Shales (Nummulites, Heterostegina cf. antillea, Lepidocyclina cannellei, L. falconensis, L. undosa, L. gigas, L. senni, Miogypsinoides [Miogypsina] cf. complanata, Miogypsina hawkinsi ?).

U. Eocene

U. Eocene-L. Oligocene Jarillal Shales (Raetomya schweinfurthi var. falconensis, Ectinochilus gaudichaudi var. alauda, Tellina, Mactra, Lutraria, Xanthopsis rathbuni, Falconoplax kugleri, Heterostegina, Nummulites, Raninoides rathbunae, Eoinachoides senni).

U. Eocene Santa Rita Conglomerates (Discocyclina flintensis, Asterocyclina georgiana, A. asterisca, Lepidocyclina adkinsi, L. trinitatis, Nummulites cf. parvulus, Operculina cf. cookei, Spiroclypeus, Bulimina jacksonensis, Raetomya schweinfurthi var. falconensis, Ectinochilus gaudichaudi var. alauda, Nuculana, Arca, Glycymeris, Pecten, “Cardium”, Clementia, Dosinia, Chione, Corbula, Architectonica, “Natica”, Turritella, Clava, Lyria, Oliva, Turns, Conus, nautiloids).

The Upper Eocene age of the Santa Rita conglomerates, with Discocyclina, Asterocyclina, Spiroclypeus, and Raetomya, is well-established. The Jarillal Shales, with Raetomya and the same Ectinochilus also appear to be of Upper Eocene age, there being no evidence of any Oligocene element in the fauna.

In the Churuguara Shales a different suite of Lepidocyclinas suddenly appears, and the queried occurrence of Miogypsina hawkinsi is to be disregarded. The presence of Miogypsinoides indicates an age not older than Middle Oligocene. It appears that there is a palaeontological and stratigraphical break above the Jarillal Shales, that the Lattorfian (L. Oligocene) is missing, and that the Churuguara Shales are of Rupelian age.

In the San Luis Formation it is again my opinion that the “rare and small” “Nummulites” are almost certainly not Nummulites, but probably Operculinella. The presence of Miogypsina in all beds from the Lower San Luis Formation up to the Damsite Formation (except for the Socorro Formation, which contains gastropoda only) indicates that these beds range in age from Aquitanian (basal Miocene) to Middle Miocene; since the Aguaclara Formation contains Spiroclypeus (not ranging above Aquitanian), both it and the San Luis Formation are of Aquitanian (basal Miocene) age.

There are other cases in which similar confusion with regard to the Miocene-Oligocene boundary has arisen. A careful analysis of all the evidence has convinced the writer that there are a number of well known forms with worldwide distribution that are particularly useful for age-determination. Miogypsina (basal Miocene to Middle Miocene) is but one instance. Orbulina (Neogene) is another, and Le Roy’s recent paper (1948) on the worldwide range of Orbulina universa, which is shown to occur as low as “Oligocene” only in the Central American region, is an important and significant contribution to the study of Tertiary faunas.


One further example is that of Stainforth & Rüegg (1953) who, in discussing beds in Peru, write:

“However, a very important microfauna was discovered in one sample near the base” (of the Camana formation). “The assemblage consists of the two species Miogypsina (Miogypsina) gunteri and Miogypsina (Miolepidocyclina) ecuadorensis, together with less significant smaller Foraminifera. Drooger has lately demonstrated the evolutionary pattern of Miogypsina in the Caribbean region and it is clear from his records that the basal Camana fauna is late middle or earliest Upper Oligocene.”

To the writer it seems quite clear that this is a Lower Miocene transgression, not a mid-Oligocene transgression as suggested by the writers.

In conclusion it is recommended that the term “Aquitanian” be used in future only for beds and faunas known to be of basal Miocene age, the term Chattian being available for the Upper Oligocene. Furthermore, particular care should be taken in the analysis and assessment of previously published work in view of the incorrect use to which the term “Aquitanian” has been put and of the consequent exaggerated ranges of some useful index-fossils, both genera and species.


Brönnimann, P., 1940. Über die tertiären Orbitoiden und die Miogypsiniden von Nord-West Marokko. Schweiz. Pal. Abhandl., lxiii, 1-113.

Dehm, R., 1949. Zur Oligocän-Miocän-Grenze. N. Jb. Min. usw., Mh., Jg. 1949 (B), 141-6.

Durham, J. W., 1944. The Type section of the Aquitanian. Amer. Journ. Sci., ccxlii, 246-250.

Gignoux, M., 1950. “Géologie Stratigraphique,” 508-510, etc.

Haug, E., 1908-11. “Traité de Géologie,” ii(3), 1604, 1607, etc.

Le Roy, L. W., 1948. The foraminifer Orbulina universa d’Orbigny, a suggested Middle Tertiary time indicator. Journ. Pal., xxii, (4), 500-508.

Rutsch, R. E., 1951. Das Typusprofil des Aquitanien. Eclog. geol. Helvet., xliv, 352-5.

Senn, A., 1935. Die stratigraphische Verbreitung der Tertiären Orbitoiden. Eclog. geol. Helvet., xxviii, (1), 51-113.

Stainforth, R. M., and Rüegg, W., 1953. Mid-Oligocene Transgression in Southern Peru. Bull. Amer. Assoc. Petrol. Geol., xxxvii, No. 3, 568 -9.

Anglo-Iranian Oil Co.,


Vol. 91, No. 2, March-April, 1954

Comments on the Caribbean Oligocene

Sir,—Dr. Eames’s attempt (Geol. Mag., 90, 1953, pp. 388-392) to transfer half the Caribbean Oligocene into the Miocene is remarkable for the short list of references. The works of Caudri, Drooger, Grimsdale, Hedberg, Kugler, Olsson, Renz, Vaughan, and Woodring—to name but a few—should surely be considered before claiming flatly that Miogypsina indicates a Miocene age, regardless of other considerations.

A regional transgression can be recognized in the West Indies and in northern South America, Ecuador, and Peru. The transgressive beds are marked by the appearance of new faunal elements, which include Chattian-Rupelian molluscs (fide Olsson, Rutsch, Woodring, et al.), and Oligocene larger foraminifera (fide Vaughan and collaborators, Caudri, et al.). The genus Miogypsina appears in the basal transgressive beds in several countries (Drooger, et al.), and its early forms appear to be a direct development from the Lower Oligocene Rotalia mexicana. The basal Camana unconformity in Southern Peru is a local example of the regional transgression: the presence of Miogypsina (Miolepidocyclina) ecuadorensis establishes correlation with beds in Ecuador, which themselves underlie thick pre-Aquitanian shales. Hence the basal Camana beds are Oligocene and Eames’s claim (op. cit.) of a Miocene age is unacceptable.

Between the time of the mid-Oligocene transgression and the first appearance of faunas of Aquitanian type, the planktonic foraminifera show a well-defined pattern of change and evolution, consistent over the whole mid-American region. Globigerina dissimilis survived for a short time. Near its eve of extinction the genus Globigerinatella made a short-lived appearance. The Globorotalia fohsi clan appeared, with an evolutionary sequence of subspecies, but died out abruptly as G. menardii appeared. Orbulina universa was preceded by its ancestral form G. suturalis.

European paleontologists could make an invaluable contribution to transoceanic Tertiary correlation by following Colom, Grimsdale, and others in recording the ranges of these species in the European Tertiaries.

R. M. Stainforth.

c/o International Petroleum Co.,

Talara, Peru.

9th February, 1954.

Selected References

Barker, R. W., and Grimsdale, T. F., 1937. Studies of Mexican fossil foraminifera. Ann. Mag. Nat. Hist., ser. 10, xix, 161.

Bolli, H., 1950. The direction of coiling in the evolution of some Globorotaliidae. Contr. Cushman Found. Foram. Res., i, 82-9.

Brönnimann, P., 1951. The genus Orbulina d’Orbigny in the Oligo-Miocene of Trinidad, B.W.I. Contr. Cushman Found. Foram. Res., ii, 131-8.

Colom, G., and Gamundi, J., 1951. Sobre la extension e importancia de las “Moronitas” a lo largo de las formaciones aquitano-burdigalienses del estrecho nort-bético. Inst. “Lucas Mallada” Invest. Geol., Estudios Geológicos, xiv, 331-385. Madrid.

Drooger, C. W., 1952. Study of American Miogypsinidae. Thesis, Rijks-Univ. Utrecht. Vonk and Co., Zeist, Netherlands.

Grimsdale, T. F., 1951. Correlation, age-determination, and the Tertiary pelagic foraminifera. Proc. Third World Petr. Congr., sec. 1, 463-472.

Hedberg, H. D., 1937. Foraminifera of the Middle Tertiary Carapita formation of north-eastern Venezuela. Journ. Paleont., xi, 661-697.

Olsson, A. A., 1932. Contributions to the Tertiary paleontology of Peru: part 4, the Peruvian Oligocene. Bull. Amer. Pal., xix, no. 68.

Renz, H. H., 1942. Stratigraphy of northern South America, Trinidad, and Barbados. Proc. 8th Amer. Sci. Congr., iv, 513-571.

—, 1948. Stratigraphy and fauna of the Agua Salada group, State of Falcón, Venezuela. Geol. Soc. Amer., mem. xxxii.

Vaughan, T. W., and Cole, W. 5., 1941. Preliminary report on the Cretaceous and Tertiary large foraminifera of Trinidad, B.W.I. Geol. Soc. Amer., Special Paper xxx.

Woodring, W. P., and Thompson, T. F., 1949. Tertiary formations of Panama Canal Zone and adjoining parts of Panama. Bull. Amer. Ass. Petr. Geol., xxxiii, 223-247.


Vol. 91, No. 4, July-August, 1954

The Caribbean “Oligocene”

Sir,—Dr. Stainforth’s comments on my recent paper on the Miocene-Oligocene boundary, especially in so far as they affect the Caribbean region (Geol. Mag., 91, No. 2, pp. 175-6, 1954), suggest that he has missed the object of the paper. I am familiar with the selected references cited by Mr. Stainforth, as well as many more concerning the Central American region and many others dealing with marine Miocene and Oligocene faunas in other parts of the world: only a few selected recent papers having a fundamental bearing on the subject were quoted in my original paper probably for the same reason as Dr. Stainforth—because a comprehensive list would have been impracticable as it would fill a whole issue of this periodical.

A study of the more recent literature, referred to in part before, indicates that there is a growing school of workers who recognize that the upper part of the so-called “Oligocene” in the Caribbean region is probably of Lower Miocene age: this is the view that I fully endorse as a result of researches carried out in many parts of the world over a period of nearly thirty years. It is evident that two important and world-wide palaeontological changes are involved, one between the Eocene and the Oligocene, the other between the Oligocene and the Miocene, the latter occurring well below the so-called Miocene-Oligocene “boundary” as interpreted until recent years in the Caribbean region. Consequently, I am firmly convinced that the faunal succession in the latter region is not out of phase with that in all other parts of the world, and that beds with Miogypsina, Orbulina, Candorbulina (for example) and their associated faunas, as now known, are all unquestionably of Miocene age. The evolutionary succession of Miogypsina sensu stricto (see Drooger) lies entirely within the Miocene.

Finally, I would point out that Dr. Stainforth, throughout his writing, is using the terms “Oligocene”, “Miocene”, and “Aquitanian”—all the stages being defined in Europe—as if they were unquestionably used correctly in the Caribbean region. This I maintain is not the case. It is imperative that subscribers to this view should purge their minds of all preconceived ideas and review and assess the palaeontological evidence from the Caribbean region again and compare it anew with modern and up-to-date evidence from other parts of the world. My conclusions have been based on such studies. Not all those who study the Caribbean Tertiaries appear to have carried out such investigations and this is hindering the promotion of a sound and orderly understanding of the evolution of Tertiary faunas and of their world-wide correlation.

F. E. Eames.

Anglo-Iranian Oil Co., Ltd., Beaufort House, Gravel Lane,

London, E. 1.

21st May, 1954.


Vol. 91, No. 5, Sep-Oct, 1954.

The Miocene/Oligocene Boundary in the Caribbean Region

Sir,—The paper by F. E. Eames in this Magazine (vol. 90, No. 6, December, 1953), and the subsequent exchange of opinions between Drs. Eames and Stainforth (vol. 91, No.. 2 and 4), is of unusual interest to students of Caribbean stratigraphy.

Eames certainly demands drastic changes in the Upper Tertiary stratigraphy of the Caribbean region but there is no sense in trying to shirk the issue at stake. We are not in a position to contradict his contentions but it seems prudent and scientific to consider seriously his conclusions. Is it only a coincidence that almost all specialists in larger foraminifera with intimate knowledge of faunal assemblages in Europe, North Africa and the Near and Far East, were, and seemingly still are, inclined to attribute a younger age to post-Eocene larger foraminifera from the Caribbean region than is admitted by their colleagues in the Americas? Why the common reference of students of smaller foraminifera to the close relationship of Miocene-Pliocene assemblages of the Indo-Pacific with Oligocene ones of the Caribbean region? In the Paleocene and Eocene we accept without hesitation the fact that pelagic forms may be used as universal time markers. There is, therefore, no reason why the same or related genera should not have the same stratigraphic value in younger beds. At least until the end of the Oligocene there was free connection between Atlantic and Pacific provinces across the Darian isthmus (Woodring, 1954, p 728). This being the case these was nothing to stop free interchange between the two areas at this period, let alone between North Africa and the Caribbean region. It is, therefore, necessary to heed the advice of Eames and review and assess the palaeontological evidence of the Caribbean region without preconceived ideas.

Above all we have to agree with Eames who states that the type locality of the Aquitanian must be in the Aquitaine and nowhere else. Secondly, we must reconcile ourselves to the fact that European Tertiary stages are established essentially on the study of shallow water marine molluscs and therefore must disagree with Gignoux (1936, p.503), who—though tentatively only—places the Aquitanian in the Upper Oligocene on account of the Stampian aspect of a mammalian fauna of the lacustrine facies equivalent of the marine type section. Following from these two suppositions we have to place the Aquitanian in the Lower Miocene (see Rutsch, 1952, p. 354), as in fact is done by the U.S. Govt. Survey (Woodring, 1943, p. 1714). Many of the discrepancies found in attempts to make a worldwide correlation of the Upper Tertiary would disappear if universal agreement could be reached on this point.

The boundary between Oligocene and Miocene in Trinidad has recently been discussed (Kugler, 1953, p. 46), when it was pointed out that, in reality, the zone of Globorotalia fohsi belongs in the Lower Miocene and not in the Upper Oligocene as under the present classification used in the Island. If, however, “the evolutionary succession of Miogypsina sensu stricto lies entirely within the Miocene” (Eames, 1954, p. 327)[4], then hardly any sediments occurring in Trinidad could be assigned to the Oligocene, for in such case the Globigerinatella insueta, the Globigerina dissimilis, and the Globigerina cf. concinna zones would be of Miocene age. The Globigerina cf. concinna zone includes the oldest Miogypsina s. str. bearing sediments in Trinidad and at its type locality contains a rich orbitoid fauna (Stainforth, 1948, p. 1310). Although no Miogypsinae are recorded from the calcareous silts of the type locality, Vaughan and Cole (1941) report Miogypsina hawkinsi and gunteri from eleven different localities of lithothamnia limestone and interbedded marls with the same, or a very closely related, orbitoid fauna characterized by the Lepidocyclinas gigas, undosa, favosa assemblage. From three of these localities (Kapur, Morne Diablo, and Mejias) Drooger (1952) reports Miogypsina basraensis, tani, and bronnimanni. Tobler (1925) mentioned Miogypsina from Mejias and Erin Point in association with the above mentioned large Lepidocyclinae and attributed an Upper Oligocene (Aquitanian) age to this assemblage. Whereas the Orbitoid fauna of the type locality of the Globigerina cf. concinna zone occurs in situ all other post-Eocene occurrences mentioned from Trinidad are from slipmasses embedded with other allochthonous material in the Globigerina dissimilis, Globigerinatella insueta, and Globorotalia fohsi zones and even in the Karamat and Cruse formations. Trinidad is, therefore, not suitable for the study of the lineage of Miogypsinae. Antigua would serve this purpose better.

W. P. Woodring in his classical study of the Bowden formation in Jamaica considered the fauna to belong to the Vindobonian stage, or in terms of American stratigraphy, to the top of the Middle Miocene or to the base of the Upper Miocene. P. Brönnimann studied the foraminifera of ten samples from the type locality and in a private report assigned all of them to the Globorotalia mayeri zone which is confined to the lower Lengua formation of Trinidad and to a basal subzone of it which is known from Trinidad to occur at the base of the Tamana limestone formation. On this information one would expect the Middle and Lower Miocene to be represented by those Tertiary sediments that are found in the normal sequence of several thousand feet thickness below the Lengua formation

The Globorotalia fohsi Zone of the Cipero Formation unconformably underlies the Globorotalia mayeri zone. The neritic facies of the Globorotalia fohsi zone includes the Brasso Formation with a molluscan fauna which has been assigned to the Miocene by Guppy, Mansfield, Maury, and others.

Orbulina the Miocene marker, does not occur below the fohsi zone. The Pleurophopsis-Thyasira fauna mentioned by Stainforth (1948, p. 1311) from Freeman’s Bay, and placed by him in the Globorotalia fohsi zone, occurs in thin, nodular, calcareous mudstones and lenses of cavernous limestones, both embedded in calcareous clays of the Globorotalia mayeri zone of the Lengua Formation. There is no evidence that these coldwater bivalves are allochthonous, although the Lower Lengua Formation is known to carry submarine slipmasses and rubble of older Cipero beds.

The Globigerinatella insueta Zone of the Cipero Formation follows below the fohsi zone and in its shallow water facies is characterized by the reefal limestones of Ste. Croix and the Esmeralda calcareous silt member of the Brasso Formation. Rutsch (1934) studied the pteropods of these beds and pointed to their evident relationship to the Italian Burdigalian (Langhian) and Helvetian.[5] Schilder (1939), who studied the Cypraeaceae of the Adivinanza quarry (an impure limestone near the Ste Croix limestone and of the same age), attributes a Burdigalian age to them. The corals of these two reefs were considered to be Miocene by Vaughan and Hoffmeister.

The Globigerina dissimilis Zone of the Cipero Formation follows normally below the insueta zone with the Nariva Formation representing its muddy fore deep facies. The dissimilis zone is commonly contaminated with allochthonous material produced by submarine land-slides and turbidity flows. The Lepidocyclina gigas, undosa, favosa assemblage of orbitoids occurs together with Miogypsina in the limestone of Kapur, which, according to Brönnimann (private report) and Drooger (1952, p. 21), represents a shallow water facies of the Globigerina dissimilis zone. However, at this locality this zone also carries reworked material of Upper Eocene and Middle Eocene age, as well as foraminifera of the Globigerina cf. concinna zone.

Miogypsina complanata is reported by Drooger (1951, p. 363) from Trinidad. According to Brönnimann (private report) this form occurs in the Globigerina dissimilis zone and Caudri (in Stainforth, 1948, p. 1312) reports it from the limestone and marl of Mejias Quarry. The Mejias limestone slipmass is found embedded in the Globigerina fohsi zone.

The Globigerina cf. concinna Zone[6] follows normally below the dissimilis zone and, as already mentioned, at the type locality carries an orbitoid fauna of the Lepidocyclina gigas, undosa, favosa assemblage which Vaughan and Cole (1941, p. 28) consider to be of Upper rather than Lower Oligocene age. The poor molluscan fauna of seven species was studied by Rutsch (Stainforth, 1948, p. 1310) and the age was determined tentatively as either Rupelian or Chattian. The most common species is Propeamussium bronni pennyi (Harris) which is also found in younger beds. In addition, J. W. Wells (private letter) mentions the coral Trochocyathus (Aplocyathus) obesus (Michelotti) from the type locality. The orbitoid fauna of the type locality shows great similarity in composition to that of Mejias, Kapur, and other limestone slipmasses of South Trinidad. This assemblage is closely related to that of the type locality of the Antigua limestone in Antigua and the San Luis limestone in the State of Falcón (Venezuela). J. W. Wells who studied the coral fauna of the Antigua limestone mentions in a private letter thirty-three different species. Of these he noted six species amongst the fourteen listed from Kapur Quarry. Three of the species from Kapur also occur amongst the twenty-five species of the San Luis limestone. The coral fauna of Antigua is considered to be Oligocene. The Antigua limestone rests unconformably on stratified tuffs with cherts bearing a typical fresh-water molluscan fauna and beautifully preserved silicified wood of a comparatively rich flora. At San Fernando (Trinidad) the orbitoid assemblage of Lepidocyclina gigas, undosa, favosa rests directly on the Upper Eocene (Stainforth, 1948, p. 1309). In reality, one observes at the type locality of the San Fernando Formation, at Mt. Moriah, well-bedded, calcareous glauconitic sands of Upper Eocene age superimposed on Middle Eocene Navat Formation, Paleocene Chaudiere shale, and Upper Cretaceous Naparima Hill Formation. These glauconitic sands are unconformably overlain by a block conglomerate, about 20 feet thick, dominantly composed of Upper Cretaceous blocks. This conglomerate changes rapidly upwards into sand and silt of apparently Upper Eocene age, including bioherms of Upper Eocene orbitoidal lithothamnia limestone rich in echinids (Echinolampas) and a few molluscs. A few large blocks of Maestrichtian glauconite sand, blocks of Paleocene Soldado Formation and of Senonian Naparima Hill Formation are embedded in these sands and silts. These Upper Eocene beds grade upwards into the Globigerina cf. concinna zone.

Up to now no definite Lower Oligocene sediments have been established in Trinidad, although it is known that foraminiferal calcareous sediments exist between the cf. concinna zone and the Upper Eocene. Similar uncertainties are known from Venezuela where the Guacharaca Formation of the Agua Salada Group (Renz, 1948, p. 30) might belong to it.

There is obviously every reason to expect the presence of sediments of the entire Oligocene time where carbonate deposits were being laid down from Upper Eocene times into the Oligocene.

Woodring (1954, p. 727) states that in the Caribbean region “an early Oligocene part has not yet been faunally defined.” It appears that one of the first steps to be taken is to define the age of the Antigua limestone with its rich assemblage of larger foraminifera, corals, echinoids, and a few molluscs. Such definition of age has, however, only a meaning if palaeontologists and stratigraphers can arrive at an agreement regarding the top of the Oligocene and cannot be solved by coining new stage names based on foraminiferal assemblages; a procedure that can only lead to chaos in stratigraphic nomenclature. Agreement has generally been reached as regards the base of the Oligocene inasmuch as the top Eocene pelagic foraminifera are universally widespread and well-defined. The definition of the top of the Oligocene is of sufficiently great importance to deserve the attention of the International Geological Congress and it is hoped that this question may be taken up in 1956. In Mexico, geological conditions for the solution of this problem are amongst the best to be found. A world-wide correlation of Tertiary marine sediments based on pelagic foraminifera is the ardent desire of most micro-paleontologists and geologists.

Until more compelling evidence is available, and the whole matter is discussed at an international meeting, I consider that the base of the Caribbean Miocene should be placed temporarily at the base of the Globorotalia fohsi zone.

H. G. Kugler.

Trinidad Leaseholds, Ltd.,

Pointe-a-Pierre, Trinidad.

24th September, 1954.


Beckman, J. P., 1953. Die Foraminiferen der Oceanic Formation (Eocaen-Oligocaen) von Barbados, Kl. Antillen. Ecl. Geol. Helv., lxiv. 301-412.

Bolli, H., 1954. Note on Globigerina concinna Reuss, 1850. Contrib. Cushman Found. Foram. Res., v, 1-3.

Cooke, C. W., J. Gardner, and W. P. Woodring, 1943. Correlation of the Cenozoic Formations of the Atlantic and Gulf Coastal Plain and the Caribbean Region. Bull. Geol. Soc. Amer., liv, 17l3-1724.

Drooger, C. W., 1951. Notes on some representatives of Miogypsinella. Proc. Konink. Nederl. Akad. Wetensch., liv, 357-365.

—, 1952. Study of American Miogypsinidae. Diss. Utrecht University.

—, 1954. Miogypsina in Northern Italy. Koninkl. Nederl. Akad. Wetensch., lvii, 228-249,

Gignoux, M., 1936. Géologie stratigraphique. Paris.

Kugler, H. 0., 1953. Jurassic to Recent Sedimentary Environments in Trinidad. Bull. Ass. Suisse Géol. et Ing. Petrole, xx, 27-60.

Leriche, M., 1938. Contribution a l’étude des Poissons fossile des pays riverains de la Méditerranée americaine. Mem. Soc. Pal. Suisse, lxi, 1-43.

Renz, H. H., 1948. Stratigraphy and fauna of the Agua Salada Group, State of Falcón, Venezuela. Geol. Soc. Amer. Mem., 32.

Rutsch, R. F., 1952. Das Typusprofil des Aquitanien. Ecl. Geol. Helv., xliv, 352-5.

Rutsch, R., 1934. Pteropoden und Heteropoden aus dem Miocaen van Trinidad. Eclog. Geol. Helv., xxvii, 299-326.

Stainforth, R. M., 1948. Description, Correlation, and Paleoecology of Tertiary Cipero Marl Formation, Trinidad, B.W.I. Bull. A.A.P.G., xxxii, 1292-1330.

Tobler, A., 1925. Miogypsina im untersten Neogen von Trinidad und Borneo. Eel. Geol. Helv., xix, 719-722.

Vaughan, T. W., and W. S. Cole, 1941. Preliminary Report on the cretaceous and Tertiary larger Foraminifera of Trinidad, British West Indies. Geol. Soc. Amer. Special Paper No. 30.

Woodring, W. P., 1954. Caribbean Land and Sea Through the Ages. Bull. Geol. Soc. Amer., lxvi, 719-732.


Vol. 91, No. 6, November-December, 1954

The Oligocene-Miocene Boundary on both sides of the Atlantic



The sequence of Miogypsina species in the type region of the Aquitanian-Burdigalian offers a good basis for correlation. Early Aquitanian corresponds to the range of M. gunteri, early Burdigalian to those of M. irregularis and M. burdigalensis, early Vindobonian to that of M. cushmani. In the western Mediterranean area application of this sequence is considered justifiable. Comparison with the similar sequence in America shows a much older occurrence of equivalent species in the western hemisphere than in Europe. A correction of the American time scale is considered premature when made on the Miogypsinidae alone.

FOLLOWING the recent discussion of the interpretation of the Aquitanian and connected problems by Drs. Eames and Stainforth, I would like to add some comments and new data.

The ascending succession of Rupelian-Chattian-Aquitanian-Burdigalian-Vindobonian is commonly considered to cover the time range from Middle Oligocene to Middle Miocene. It is generally assumed that the individual time ranges fit nicely together, without leaving gaps or showing overlap. On closer examination, however, this appears to be an over-simplified view; but discrepancies are difficult or impossible to tackle with our present means. Type localities of successive stages are mostly irregularly scattered on the map of Europe, so that the law of superposition cannot be applied. We must therefore look for index fossils, but in this we are severely hampered by facies differences of the various type sediments. Moreover, migration times of such organisms, different survival periods, and somewhat different evolution rates in separate regions, tend to complicate matters still further. The exact relations between the components of our time scale may remain obscure, especially because of the relatively small amount of errors. Consequently, we must accept the idealistic picture of the time scale. A possible time-stratigraphic gap between two successive type sections, once proved, must be considered to belong to one of the stages, if it is not wide enough to create a new name for it. On the other hand, in the case of overlapping, one of the stages must be corrected in order to get rid of the part twice accounted for.

On this theoretical basis, I consider the time directly preceding the fairly well-defined Aquitanian as Chattian, though we do not know as yet the level that corresponds to the upper limit of the type Chattian in the Aquitaine basin. The same reasoning is applied to the Burdigalian-Vindobonian boundary.

As regards the Oligo-Miocene stages, Aquitanian and Burdigalian offer a good starting point, since in them we have at least two stages that have been defined with clear interrelation in a single area. For their interpretation in other regions I am inclined to give special weight to certain groups of Foraminifera, though this opinion may not be free from the bias of a micropaleontologist. The “orbitoidal” larger Foraminifera and the pelagic smaller ones are important not merely because of their usually world-wide distribution, but especially their distinct evolutionary trends and their capacity for rapid dispersal respectively.

As to the Oligocene-Miocene type sections, only those of the Aquitanian and Burdigalian contain “orbitoidal” larger Foraminifera. Unfortunately their deposits of fore-reef facies contain hardly any planktonic species. Mr. Kaasschieter only found some scattered individuals of Globigerina bulloides and Globigerinoides trilocularis in the sediments of both stages.

The type deposits of the Aquitanian near Bordeaux overlie Oligocene beds that contain no larger Foraminifera. At the type locality (Moulin de Bernachon, near Saucats) the lowermost Aquitanian of lacustrine to brackish-water fades is also devoid of these organisms, but Miogypsina (Miogypsina) gunteri was found in equivalent beds some kilometres away (railway cutting of Labrède). The younger part of this stage is characterized by M. (Miogypsina) tani.

The more primitive M. (Miogypsinoides) complanata, met with in the southern part of the Aquitaine basin, is considered to be of pre-Aquitanian age (Chattian and possibly younger Rupelian). At the localities involved (Saint-Etienne-d’Orthe, Saint-Géours, Christus, Abesse) it is always accompanied by Lepidocyclina (Nephrolepidina) tournoueri.

The Aquitanian is separated by a short hiatus from the overlying Burdigalian. In the older Burdigalian, the Miogypsina sequence continues with M. (Miogypsina) irregularis, followed by M. (Miogypsina) intermedia in the younger part. In the oldest beds Miogypsina (Miolepidocyclina) burdigalensis also occurs, but this species evidently entered the Aquitaine basin as an immigrant, and soon disappeared again.

Text-fig. 1. Tentative correlation-chart of the Miogypsinidae in the Western Mediterranean area and America. For each geographic area the representatives of the subgenera Miogypsinoides, Miogypsina, and Miolepidocyclina (with Miogypsinita) are given on separate levels from top to bottom.
(1) Not autochthonously observed; (2) traces only.

The beds overlying the Burdigalian in S.W. France, which are placed in the Vindobonian (Helvetian), contain no more larger Foraminifera. But more highly developed species of the Miogypsina s. str. series have been found further south in Morocco M. (Miogypsina) cushmani and M. (Miogypsina) mediterranea. These species I regard as of Vindobonian age.

These data from the Aquitaine basin allow of the following conclusions. The Rupelian-Chattian boundary cannot yet be found with the help of the Miogypsinidae. M. gunteri begins its range with the oldest Aquitanian. The Aquitanian-Burdigalian boundary coincides with that between M. tani and M. irregularis, while M. burdigalensis also marks early Burdigalian. The boundary between Burdigalian and Vindobonian can best be placed between M. intermedia and M. cushmani.

For correlation within the western Mediterranean area the Miogypsinidae appear to be very useful. The sequence of Miogypsina species in northern Italy is similar to that in S.W. France. In Italy the Miolepidocyclina lineage developed from M. gunteri, but it was later on replaced by Miogypsina s. str. The latter ended here at the same morphological level as it did near Bordeaux (M. intermedia). Correlation of the strata of both areas is strengthened by the migration of M. burdigalensis from Italy in a western direction to the Aquitaine basin and also to Morocco.

A comparable sequence of Miogypsinidae occurred in Morocco. Unfortunately it is nearly entirely obscured in the faunas described by Senn and Brönnimann, for they described associations that contain up to 90 per cent of drifted elements, a fact which could not at that time be appreciated by these authors. Probably the Miogypsina-bearing beds are of Aquitanian to Vindobonian age, containing the autochthonous series M. tani to M. mediterranea.

From these data on the larger Foraminifera of this side of the Atlantic it may be seen that the sequence advanced in the beginning of this century by Lemoine, R. Douvillé and others was erroneous in several of its details, and this accounts for many wrong correlations in other parts of the world.

Turning our attention now to the other side of the Atlantic, we find a Miogypsina sequence closely resembling that of France, though less well-founded because of the lack of a sufficient number of long, Miogypsina-bearing, stratigraphic sections. Comparison of the sequences clearly shows that corresponding species are estimated to be much older in America than they are in Europe. So, if other data are found that corroborate this picture, the American time scale must be considered to be wrong to a considerable extent. However, such data on other Foraminifera are still very scarce this side of the Atlantic. Planktonic Foraminifera may indicate a divergence in the same direction, but in Europe, exact details concerning these fossils in the Miogypsina sequence are unknown to me. I am completely at a loss for instance to know where exactly Orbulina begins its range on our side of the Atlantic. The stratigraphic distribution of Lepidocyclina is also a warning against placing too much reliance on the Miogypsinidae alone, as index fossils for trans-Atlantic correlation. Both in France and Italy the last Lepidocyclinae are found accompanying Miogypsina complanata, but in America they are found at least up to the level of M. intermedia. This may be due to a longer survival of the Lepidocyclinidae in the western hemisphere, but such is merely a hypothesis at the moment.

As a result, change of the American Oligo-Miocene time scale and so of the place of the Oligocene-Miocene boundary is looked upon as premature on the basis of the Miogypsinidae exclusively. However, they certainly suggest a considerable shift, the exact extent of which must be determined by additional detailed data on other Foraminifera.

A final remark may be made about the placing of the Aquitanian in either Oligocene or Miocene. So far I have placed it in the latest Oligocene. However, with regard to its microfauna at the type locality, there is but slight difference from that of the type Burdigalian. Though of course for the greater part based on facies resemblance, this fact favours a grouping with the Miocene. In that case the natural limit suggested by the Miogypsinidae is doubtful some species of Miogypsina s. str. (M. thalmanni, M. basraensis) are likely to be pre-Aquitanian so that the change from Miogypsinoides to Miogypsina s. str. does not mark the Oligocene-Miocene boundary. Lepidocyclina may be no more helpful either, in my opinion the placing of the Aquitanian is not so important, so long as it is correctly interpreted.


Brönnimann, P., 1940. Über die tertiären Orbitoiden und die Miogypsiniden von Norwest-Marokko. Schweiz. Pal. Abh., lxiii.

Drooger, C. W., 1952. Study of American Miogypsinidae. Acad. Thesis Utrecht.

—, 1954. Miogypsina in northern Italy. Proc. Kon. Ned. Ak. Wetensch., set. B, lvii, 227-249.

—, 1954 or 1955. Miogypsina in north-western Morocco. idem. (in press).

Kaaschieter, J. P. H., and A. J. Key, 1954 or 1955. The microfauna of the Aquitanian-Burdigalian of south-western France. Verh. Km. Ned. Ak. Wetensch. (in press).

Eames, F. E., 1953. The Miocene, Oligocene Boundary and the use of the Term Aquitanian. Geol. Mag., xc, 388-392.

—, 1954. The Caribbean Oligocene. idem., xci, 326-7.

Lemoine. P., and R. Douvillé, 1904. Sur le genre Lepidocyclina. Mém. Soc. Géol. Trance, Paléont, xii.

Senn, A., 1935. Die stratigraphische Verbreitung der tertiären Orbitoiden mit spezieller Berücksichtigung ihres Vorkommens in Nord Venezuela und Marokko. Ecl. geol. Helv., xxviii, 51-113, 369-373.

Stainforth, R. M., 1954. Comments on the Caribbean Oligocene. Geol. Mag., xci, 175.

Geol. Instituut, Oude Gracht 320,


The Netherlands.


Vol. 92, No. 1, January-February, 1955

The Miocene/Oligocene Boundary in the Caribbean Region

Sir,—The contribution by Dr. H. G. Kugler (Geol. Mag., xci, 1954, 410-413) on the above subject is very welcome, as it summarizes much evidence bearing on the question. To the writer it seems that much of the information required has now been brought forward, either explicitly or indirectly, and it is only in the interpretation that opinions differ. Much emphasis has been placed upon the evidence of pelagic foraminifera, but world-wide correlation must be based upon the sum total of all palaeontological evidence and not upon them alone; even so, the study of such pelagic faunas shows that their evidence really does fall closely into line with that from other sources. On this basis probably all the Cipero formation is of Lower Miocene age.

The writer does not consider it prudent “to expect the presence of sediments of the entire Oligocene time where carbonate deposits were laid down from Upper Eocene times into the Oligocene.” The amount of Oligocene present must surely be deduced from an impartial consideration of all palaeontological evidence ab initio. In a region such as the Caribbean, there is no reason why Lower and Upper Oligocene should not be missing in many areas, as is, indeed, the case in a number of other parts of the world, where only the Rupelian (Middle Oligocene) is developed.

Finally, I would question whether the definition of the top of the Oligocene merits the attention of the International Geological Congress, except, perhaps, to confirm that it occurs between the Chattian and Aquitanian.

F. E. Eames.

The British Petroleum Co., Ltd.,

Beaufort House,

Gravel Lane,

London, E. 1.

3rd January, 1955.

(Reprinted from Nature, Vol. 185, No. 4711, pp. 447-448, February 13, 1960)

Mid-Tertiary Stratigraphical Palaeontology


In the course of extensive economic palaeontological researches based on world-wide investigations, it has been found necessary to review and re-assess the bases of mid-Tertiary correlation arid dating. We confirm the validity of the five-fold subdivision of the Oligocene and Lower Miocene as represented by the faunas of the type localities of the Lattorfian, Rupelian, Ohattian, Aquitanian and Burdigalian. These five faunal assemblages can readily be correlated through to Southern Europe, the Mediterranean, the Middle East, East Africa, Pakistan and India, and the Far East as a whole.

Although the classical type assemblages are mainly developed in a molluscan-echinoid facies we confirm that it is possible to correlate these facies with beds in Southern Europe, which also contain important and characteristic foraminiferal faunas which can readily be followed through to the Far East, notwithstanding that minor stratigraphical and taxonomic revisions of older work are necessary.

In brief, beds equivalent to the Lattorfian are characterized by Nummulites intermedius and N. vascus without Eulepidina; the equivalents of the Rupelian are characterized by the persistence of Nummulites intermedius and N. vascus and the appearance of Eulepidina; the equivalents of the Chattian (where confirmed) are characterized by the persistence of Eulepidina and other Rupelian Foraminifera, but all true Nummulites had become extinct. Following the mid-Tertiary stratigraphical break, the equivalents of the Aquitanian (forming the lowest beds of the Miocene) are characterized by the persistence of Eulepidina, Spiroclypeus and Miogypsinella complanata, and the incoming of many forms, such as Miogypsina s. str., Meandropsina anahensis and Miolepidocyclina, which constitute part of the Neogene evolutionary surge; the Burdigalian equivalents are characterized by such forms as Ostrea latimarginata, Borelis melo curdica, Flosculinella bontangensis and Taberina malabarica, by the persistence of Miogypsina and Austrotrillina howchini, and by the appearance of Borelis melo, but Eulepidina and Spiroclypeus had become extinct.

It can be evaluated from the above that in the Far East the ‘c’ stage is probably Lattorfian, the ‘d’ stage is Rupelian. the ‘e’ stage is Aquitanian, and the ‘’ substages are Burdigalian; the presence of the Chattian is not proved. Besides the fossils mentioned above there are many others which substantiate the above conclusions.

Within the equivalents of the five classical stages there is a succession of planktonic foraminiferal faunas (Globigerinaceae) which appears to be constant wherever found and studied. These planktonic successions can be firmly dated in terms of the classical stages by their associated faunas; they permit accurate age determination of marine faunas in the western hemisphere, where, because of relative isolation, few benthonic fossils are in common with their Eurasian and African equivalents.

It has been possible to demonstrate the equivalence of the Caribbean zones of Globorotalia fohsi fohsi, G. fohsi lobata and  G. fohsi robusta to the Burdigalian. The Aquitanian seems to be equivalent to all the planktonic foraminiferal zones erected by Bolli (1957) for the Cipero formation of Trinidad below the G. fohsi fohsi zone; consequently, all the Vicksburgian and its equivalents are Aquitanian. The evolution of Orbulina, known to occur in the upper part of the Globigerinatella insueta zone of the Caribbean, also occurs in the highest Aquitanian of the Mediterranean and Australia; this correlates with the first appearance of Orbulina in the upper ‘e’ stage of the Far East.

It seems to be very important to note that, on the basis of the succession of planktonic foraminiferal faunas, no Oligocene can be recognized in the marine sediments of the western hemisphere, as far as published records show. This absence of Oligocene has now been confirmed by the discovery of a planktonic foraminiferal fauna associated with true Oligocene larger foraminifera such as Nummulites intermedius and N. vascus in East Africa. This planktonic foraminiferal fauna is being described elsewhere; it is noted here as having common elements with similar faunas seen in the Rupelian of south Germany and that described by Russian workers. This fauna has never been recorded or observed by us in Central American areas, and is missing precisely where we place the major stratigraphical break in that region.

The absence of marine Oligocene in the Central American region is again confirmed by the presence of Miogypsina a. str. associated with Eulepidina and of Pliolepidina in the lowest post-Eocene of the well-known southern Trinidad succession, which contains the oldest known post-Eocene planktonic zone of the Caribbean. True Nummulites (as distinct from Palaeonummulites) is absent above the Eocene in the Caribbean.

Palaeonummulites Schubert 1908 (type species Nummulina pristina Brady 1874) is regarded as a prior synonym of both Operculinella Yabe 1918 and Operculinoides Hanzawa 1935. The lectotype of Palaeonummulites pristina (Brady) has been isolated and it will be described elsewhere, together with an emendation of the genus.

The genus Pliolepidina H. Douvillé 1915 is now regarded as a prior synonym of Multicyclina Cushman 1918, Multilepidina Hanzawa 1932, Cyclolepidina Whipple 1934, and Pliorbitoina Van de Geyn and Van der Vlerk 1935. It is believed that all species referable to this genus, whether originally recorded from the Far East, the Mediterranean region, East Africa, or Central America, are of Miocene age. The large and significant unconformity present in the Central American region is marked by the presence of much re-working of material into the basal Miocene and this has given rise to much stratigraphical confusion as to the age of the beds in question. Indeed, many of the lowest Miocene beds present have been dated as Eocene, purely on the presence of re-worked Eocene fossils, but the occurrence of Pliolepidina often shows that they are of lowest Neogene age; examples are the San Fernando formation of Trinidad and part, at least, of the Gatuncillo formation of Panama.

Full details of our work will be published in the near future elsewhere, together with a full bibliography.


British Petroleum Co., Ltd.,
Exploration Division,
B.P. Research Centre,
Chertsey Road,
Sunbury-on-Thames, Middlesex.

From Nature, August 20, 1960


The American Oligocene

Eames et al.[7], claim that the Oligocene is not represented in the marine sediments of the western hemisphere. This claim seems to conflict with the palaeogeographic status of the region.

The Eastern Venezuela Basin may be taken as representative. In Trinidad the Lizard Springs, Navet, Cipero and Lengua formations form a continuous sequence of Palaeocene to Miocene age. They are deep-sea deposits, essentially Globigerina-ooze, which accumulated along the axis of the basin.

If any appreciable time-interval is not represented in this sequence, its absence must be explained in one of three ways, namely: (1) sedimentation ceased temporarily; (2) sediments were deposited but were eroded subaerially; or (3) sediments were deposited but were removed by subaqueous processes.

Cessation of deep marine sedimentation scarcely merits consideration. The joint accumulation of fine terrigenous material and foraminiferal tests continues in basinal deeps regardless of orogenic and epeirogenic modifications of the peripheral land areas.

A prerequisite for subaerial erosion would be uplift and emergence of the sea-floor. If this had occurred there would be abundant evidence of orogeny and regional unconformity. Even if the uplift had been epeirogenic, leaving few physical signs of unconformity, the subsidence which followed would have the unmistakable evidence of shallow marine beds grading up into deep marine marls. The only such interruption of the deep marine sequence in Trinidad is the San Fernando formation, which is firmly correlated with the Upper Eocene (Jacksonian stage) of the region. The upper beds transitional from the shallow marine San Fernando formation to the deep marine Cipero formation are post-Eocene (G. ampliapertura zone).

(Eames et al. consider the rich Eocene faunas of the San Fernando formation re-worked in the basal Miocene. In more regional terms they imply that the “Jacksonian transgression” was an early Miocene event. The only reason given is their belief that the genus Pliolepidina is a Miocene index. It deserves note that in the Eastern Venezuela Basin there are extensive algal-orbitoidal reef limestones which contain Pliolepidina in association with such Eocene indices as Tubulostium, Echinolampas, Oligopygus and Asterocyclina. These are purely organic limestone with no clastic content except the finest of silt. The Pliolepidinas are definitely not re-worked, therefore this genus is unacceptable as a Miocene index in this region.)

Large-scale slumping is recognized throughout the sedimentary column in Trinidad. It is feasible, and even probable, that at any given locality some part or other of the sequence is missing by reason of submarine slumping, but it is scarcely feasible that one particular interval should be missing in this manner over the whole area. Even if this odd situation did exist on the basinal flanks the displaced beds would presumably be recognized in an allochthonous position towards the axis, and their true stratigraphic status would be established by faunal study.

In more regional terms the sequence of Upper Eocene overlain by the G. ampliapertura zone is known in a variety of facies ranging from shallow to deep marine. In all cases the same uniform change in the planktonic fauna defines the contact. This implies that, if there is a major hiatus between the two units, it is no more pronounced around the old land masses than in the basinal deeps, a conclusion contrary to the normal precepts of palaeogeography. The Eocene top usually falls within a lithologically uniform sequence. Faunally the contact is mainly defined by extinction of a few Eocene species, not by a wholesale change of fauna. No fauna has been recorded which might fit between the suites of the Upper Eocene and the G. ampliapertura zone, themselves closely interconnected by evolutionary bonds. It is not realistic to postulate extensive re-working of the Eocene faunas, which are homogeneous except for an appreciable facies-variation consistent with basinal position. This latter remark applies to Trinidad, where the Upper Eocene faunas are certainly not re-worked in the ordinary usage of that word, though the type San Fernando formation might prove to be an enormous slumped mass. I have studied this interval in Ecuador, Colombia, Venezuela, Trinidad and Barbados in the New World, as well as in Egypt and France in the Old World, and have seen no significant variation from the pattern described. Published records confirm that the same is true in other countries. The one exceptional case is in Antigua, where the G. ampliapertura zone rests unconformably on volcanic rocks. The natural conclusion to be drawn is that sedimentation was regionally continuous from the Eocene into the G. ampliapertura zone, in which case the latter must be Oligocene.

This palaeogeographic reasoning makes regional absence of the Oligocene unlikely in the marine sediments of the western hemisphere. Therefore an alternative explanation would be preferred for any palaeontological argument which seems to point to that conclusion. In particular, Eames et al. note a new suite of planktonic foraminifera in the Oligocene of East Africa and infer absence of the Oligocene in America because this suite is not known there. An alternative inference is that the new fauna reflects climatic segregation of planktonic suites. Preference of certain species for certain latitudes is well established among the Recent planktonic foraminifera. The marine mid-Tertiaries in the region encompassed by Ecuador, the Gulf Coast States and Trinidad are readily correlated by the planktonic zonation of Bolli (1957) and earlier workers, but both south and north of this tropical belt the scheme tends to break down because the marker-species are scarce or absent. Likewise in the Mediterranean region almost the same zones are recognizable, but attempts to apply the zonation in northern Europe have failed because a different, boreal suite of plankton is present. It seems that a similar situation might well exist in the southern parts of Africa and South America. The observed affinities of this new fauna to Oligocene plankton in Germany and Russia, but apparently not in the Mediterranean countries, give some support to the concept of distinct tropical-subtropical and boreal-austral suites of planktonic foraminifera in the Oligocene.

No detailed comments are offered here on the status of larger foraminifera in this problem, but I opine strongly that the palaeogeographical evidence for the presence of the Oligocene in America should outweigh strictly faunal evidence pointing to the contrary. The case of Pliolepidina, already cited, shows that like forms were not precisely coëval over the entire world. Regarding the Miogypsinidae, doubt is expressed as to their presence in the G. ampliapertura zone as I have never encountered them in situ below the G. dissimilis zone. Kugler (1954) has referred to them in the older zone, but specifies that he is writing of allochthonous material slumped into Miocene marls. The presence of the ancestral Rotalia mexicana-group in the G. ampliapertura zone in Ecuador, Colombia, Mexico and Puerto Rico makes the presence of Miogypsinidae at that level improbable.

Extensive bibliographical references to these matters are included in a paper about to be published.[8]


Jusepín, Venezuela.

Following from Dr. R. M. Stainforth’s comments on our communication, we would direct attention to the fact that it contained merely some of the conclusions reached in our study of “Mid-Tertiary Stratigraphical Palaeontology”, which will be published as an entire, illustrated book, and it is obvious that we could not give the full background in such a short space. However, the following is a very brief outline of part of the picture which has emerged from our studies.

The standard European stages of Upper Eocene, Oligocene and Lower Miocene ages may be traced from the European molluscan facies into the Mediterranean region, where they can be defined in terms of planktonic and benthonic foraminifera; these divisions can be recognized throughout the Middle East to the Far East, where the ‘letter-stages’ proposed by van der Vlerk for the Tertiary of Indonesia can be readily correlated with the European standard, and both may be correlated with the series of planktonic-foraminiferal zones erected by Bolli and others in the Caribbean. It is an inescapable fact that if the popular age-determinations of Central American middle Tertiary marine sediments are accepted, then that area is palaeontologically out of step with the rest of the world. If sedimentation in Trinidad, for example, were really continuous from the Eocene to the Miocene (and the lower Cipero formation be regarded as Oligocene), then one can only conclude that the larger foraminifera (for example, Miogypsina s.s.), the planktonic foraminifera (for example, all species of the Globigerinidae which are stratigraphically relevant) and Mollusca (for example, by regional correlation, Anadara, Chione, Timoclea) occur at stratigraphically older horizons in America than anywhere else in the world. As there is no satisfactory evidence to the contrary, we believe that the occurrences of these fossils were isochronous, and that there occurred a major hiatus in the Caribbean sequence, a hiatus including at least the equivalent of the Nummulites fichteli beds of Europe (‘c’ and ‘d’ stages of the Far East), which contain (in Africa) a rich and distinctive assemblage of planktonic foraminifera, unrepresented in America. We have been able to trace the evolutionary history of many lineages of Globigerinaceae from the Upper Eocene to the Aquitanian in richly fossiliferous and well-dated sediments in East Africa; we have found that the Oligocene stages of these lineages are present in sediments of areas as far removed as western European and Indonesia-Australasia, but that these stages are conspicuously absent in America, between the Jacksonian and the Vicksburgian.

It has been known for decades that the Vicksburg formation rests disconformably on the Jackson, and that it contains in its lower beds (for example, the Red Bluff Clay) abundant re-worked fossils of the Eocene. It has been common knowledge that the sediments of Trinidad, far from constituting a “lithologically uniform sequence” as stated by Dr. Stainforth, have been repeatedly reported to contain boulder beds (with some ‘boulders’ up to 3,500 cu. ft. in volume), rubble beds with Pholas-bored pebbles, and re-worked fossils of Upper Cretaceous, Palaeocene, Lower, Middle and Upper Eocene ages immediately above the horizon where we, on quite other (purely palaeontological) grounds, would place the Miocene/Eocene unconformity. The San Fernando ‘formation’ we believe to be the basal bed of the Miocene transgression; far from being “firmly correlated with the Upper Eocene,” as Dr. Stainforth suggests, our world-wide studies suggest that its fossil content is a mixed one, and that its youngest elements are characteristic of the Miocene. This does not conflict with the well-known fact that the lithology of the San Fernando ‘formation’, surrounding the re-worked boulders, is very close to that of the succeeding Cipero (into which it grades) but quite different from the underlying Navet; it is confirmed by our recognition of the lowest planktonic foraminiferal zones of the Cipero in acknowledged Aquitanian deposits elsewhere in the world.

It should be realized that many other widely held and long-established assumptions fundamental to mid-Tertiary dating in Central America (for example, the supposed Oligocene age of the Antigua Limestone coral fauna), when critically re-examined, prove to have little or no foundation in fact. The ages assigned to some species of several other groups of marine fossils (for example, Echinoidea, Bryozoa, Decapoda, etc.) from the Central American region will need revision in view of the evidence we shall present.

The known stratigraphical distribution of Pliolepidina depends on the interpretation of the morphology of that genus; we suspect that Dr. Stainforth has been led astray by W. Storrs Cole’s misconceived treatment of Lepidocyclina and related genera. We redefine the relevant genera and restrict Pliolepidina to forms congeneric with Multilepidina, which is not known beneath the Miocene. It should be remembered in this context that no true Nummulites have ever been recorded above the Eocene in America, American post-Eocene Nummulites-like forms being referable to Palaeonummulites (which includes Operculinella and Operculinoides.) With regard to the occurrences of Echinolampas and Oligopygus, Echinolampas ranges from Eocene to Recent, and Oligopygus occurs in the Eocene and also at levels at which Lower Miocene planktonic foraminifera occur, so that Dr. Stainforth’s implication that they are Eocene indices does not seem wise. We should also like to place on record that the ‘Rotalia’ mexicana group occurs as high stratigraphically as the Aquitanian in the Mediterranean region, and we believe it to range equally high in Central America. Also, it is mere hypothesis that this group (or even the genus Neorotalia to which it probably belongs) was ancestral to any of the Miogypsinidae, and even if this were found to be so, there would be no a priori reason to assume that the ancestral group would become extinct at the advent of its descendants.

The references for this study are so extensive, interrelated and mutually inconsistent (any brief selection would be misleading) that we can only refer the reader to the full discussion in our book, which contains a fully comprehensive bibliography, and which will soon be published.

F E Eames
F. T. Banner
W. H. Blow
W. J. Clarke

The British Petroleum Co., Ltd.,
Exploration Division,
B.P. Research Centre,
Chertsey Road,
Sunbury-on-Thames, Middlesex.

Proceedings of the First International Conference on Planktonic Microfossils







In view of past public disagreements, both in print and verbally at the last two Caribbean Geological Conferences, I take this opportunity to state that I am now in good general agreement with BLOW’S scheme of zonation.

For the past ten years I have been more concerned with broad aspects of regional stratigraphy than with the fine faunal details of planktonic zonation. From this point of view I was antagonistic to the concept postulated by EAMES and his colleagues, when they claimed that the Oligocene was absent, or feebly represented, over most of the mid-American region. From personal studies in many parts of the Andean geosynclines of Peru-Ecuador-Colombia-Venezuela-Trinidad I had concluded that the boundary between Eocene and post-Eocene beds fell, regionally, at the mid-level of a well-defined diastrophic/sedimentary cycle. To postulate a regional “break” in sedimentation at this level seemed to me illogical: on the contrary, sedimentation must generally have continued unbroken, hence the lowest post-Eocene beds must represent the Oligocene.

The crucial point of difference boiled down to the age assigned to Pliolepidina; for me, especially on evidence in Trinidad and Venezuela, P. tobleri was unequivocally upper Eocene: for the BP-group, on evidence from the Far East, the genus was Miocene (Aquitanian).

Finally, after study of the Pliolepidina-rich Peñas Blancas limestone and overlying Roblecito shale of Eastern Venezuela, agreement was reached that this is a late Eocene-to-Oligocene sequence. For my part, I have conceded that the top of the Oligocene could be lower than the level I preferred (“N.4” or “kugleri” level, defined by the Globigerinoides datum”), and on evidence of Miogypsina and Cupuladria could fall at the “N.2” or “opima” level. This point must be left pending until current work on European stratotypes is completed, and a firmer international agreement is reached on the stage-equivalence of the Oligocene-Miocene boundary.

From the practical point of view of an oil company stratigrapher, concerned with precise correlations between wells and/or surface sections, I have not found the P.18/P.19 zones useful. It is my own experience in Venezuela, and seems to be confirmed by colleagues elsewhere in South America that, even though the markers are occasionally encountered, the limits of these zones can seldom be fixed. Consequently a more practicable approach is to use the “ampliapertura zone” in a broad sense for an interval above disappearance of undeniable Eocene faunas (e.g. Hantkenina spp., Globorotalia centralis, G. cerroazulensis, Asterocyclina).

BLOW admits that this is a “twilight zone”, seemingly missing or difficult to recognise at many localities. As reason, he suggests widespread orogenic disturbances—which is a relic of EAMES’ proposal of a major worldwide orogeny between late Eocene and early Miocene time. At least in South America, I do not agree with this concept. I believe slumping out of beds, unconformities at the base of a slowly onlapping sequence, unfavorable facies and comparable explanations exist. Possibly, also, the species which best define these zones were to some extent provincialized by climatic (temperature) belts, and in their absence the P.18/ P.19/N.1 zonal sequence is not readily subdivided.

W. H. BLOW (Reply to R. M. Stainforth):

Mr. STAINFORTH’S comments are most welcome and it is pleasant to record that many of the areas of disagreement concerning the later Palaeogene—earlier Neogene successions have now been resolved or reduced for the major episodic history of the Caribbean-Central American Region. The writer considers that the work of EAMES et al., published in 1962, and the lively controversy it provoked, has done a great deal to place into proper perspective the position of the Oligocene in the Caribbean and on the Gulf Coast as well as in Europe. It will be seen from the here published work that I now accept the recommendation of the Comité du Néogène for considering the base of the Miocene at a level near the “Globigerinoides-datum” (base of Zone N.4) but, as STAINFORTH rightly points out, some faunal elements in the Zone N.3/Zone N.2 interval do show Neogene affinities rather than Palaeogene ones.

The writer must still take issue with STAINFORTH concerning his concept of a broad “ampliapertura zone” and would consider the evidence from the Roblecito shale of Venezuela as strongly supporting the need for the recognition of, at least, the combined Zone P.19/Zone P.18 interval as distinct from the Globigerina ampliapertura zone sensu BOLLI and, indeed, sensu Zone N.1 (= P.20). In this regard the writer would draw attention to figure 20 of the published work and point out that the average duration of the zones for the Zone N.4 to Zone N.8 interval seems to be about 1.2 x 106 years whilst the best available figures indicate that the zones within the Zone P.18 to Zone N.3 interval seem to be in the order of about 2.0 x 106 years. Consequently, Zones P.18/P.19 together make up an interval significantly longer than any two younger adjacent zones in the post-Zone N.3 Aquitanian-Burdigalian.

Many of STAINFORTH’S comments are answered in the full published version of my work but I feel STAINFORTH may have misunderstood my verbal comment concerning a “twilight zone” over the interval of the latest Eocene/earliest Oligocene. My comments referred to difficulties of faunal assessment of this interval (and indeed of the Zone N.4/Zone N.2 interval as well) and, therefore, the strongly subjective element in placing beds either as Eocene or Oligocene; this will be obviated eventually by a better assessment of the stratotypes for the stages involved and international agreement on which stages are to be best used.

Finally, there is no evidence to show that the zonal indices (or zonal combinations of secondary biostratigraphic markers) for the Zone N.1/Zone P.18 interval are any more provincialized than the indices or combination-markers for any of the subsequent zones. On a world-wide basis, local facies exclusions also occur at various levels and areas in the post-Eocene successions but the writer has indicated a method for dealing with these which he believes will prove useful. Probably, the Roblecito formation of Venezuela, with its included extensive sand-bodies, does not represent an environment of fully unrestricted oceanic access and is, therefore, highly likely to be subject to facies-exclusions in a local nature. The writer considers that once a maximum practical planktonic foraminiferal biostratigraphic subdivision has been achieved for the most favourable areas, a “yard stick” is available for the comparison of local successions in the context of the known complete sequence of planktonic foraminiferal phylogeny.

[1] Published by permission of the Chairman and Directors of the Anglo-Iranian Oil Co., Ltd.

[2] L. tournoueri belongs to the subgenus Nephrolepidina.

[3] Using the term Operculinella for miniature Nummulites-like forms, of small size, with a very small megalospheric nucleoconch, with little difference in size between the two generations, with or without a tendency to flare in old age. It seems very necessary to retain the name Nummulites only for those forms, such as N. atacicus, N. obtusus, N. laevigatus, N. millecaput, N. intermedius, and N. vascus, which characterize the Palaeogene.

[4] Again indirectly suggested by Drooger (1954, p. 246).

[5] Drooger (1954) correlates the “Langhiano” and “Elveziano” of the piedmont area of Turin with the upper part of the Aquitanian of the Bordeaux area.

[6] Bolli (1954) described Globigerina cf. concinna as Globigerina ciperoensis and in future the zone has to be called accordingly.

[7] Eames, F. E., et al. Nature, 186, 447 (1960).

[8] Stainforth, R. M., Rev. Micropaléont. (in the press).