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Reproduced from the Boletín de la Sociedad Geológico del Perú, T. XXVI, pp. 247-262, Lima, 1953

THE BASIS OF PALEOGENE CORRELATION
OF MIDDLE AMERICA [1]

(With 3 figures)

by

R. M. Stainforth [2]

Extracto:

Se presentan tablas que muestran la distribución regional de las tres clases de fósiles: foraminiferos grandes, foraminiferos pequeños y megafósiles (en su mayoría moluscos). Las dos tablas de foraminIferos muestran una ordenada sucesión de especies terciarias sobre toda la región centro americana, algo que no se puede establecer en los moluscos. Se recomienda por lo tanto que se dé primordial importancia a los foraminiferos guías en la correlación estratigráfica regional y que debería atribuirse un rol secundario a los fósiles de moluscos.

Abstract

Charts are presented showing the regional spread of index forms in the three categories of larger foraminifera, smaller foraminifera, and megafossils (mostly mollusks). The two foraminiferal charts show an orderly succession of Tertiary species over the whole mid-American region, but no such pattern could be established for the mollusks. It is therefore recommended that the key-foraminifera should be given primary consideration in regional stratigraphic correlation and that molluscan fossils should be given a secondary role.

As the sum of human knowledge has advanced, science has become more and more specialised. Geology is no exception and few indeed are the well-rounded geologists of today, individuals equally well versed in mineralogy and sedimentology, paleontology and tectonics, stratigraphy and geophysics. Even within the restricted field of paleontology there is a division — at times approaching a schism into megapaleontology and micropaleontology. Adherents of the former school concentrate on fossils such as the Mollusca, Echinoidea and Coelenterata. Exponents of micropaleontology specialise in minute forms such as Foraminifera, Ostracoda and Conodonta. For purposes of discussion the students of Mollusca and Foraminifera may he chosen as representative of the two schools.

The study of fossil mollusks occupies an honorable place in the history of stratigraphic investigations. In the midAmerican region pioneers such as Conrad, Lea, Aldrich and Gabb first demonstrated the Tertiary faunal succession in the Gulf Coast States. Later students extended their stratigraphic scheme through Central America and across the West Indies into South America. These studies have resulted in the niolluscan time-scale used for stratigraphic correlation on a regional scale. The specialised study of foraminifera is a relatively young branch of paleontology. Nevertheless, as a result of the intensified research induced by its practical value in exploration for petroleum, it already ranks equal in importance with molluscan paleontology. Detailed foraminiferal studies have been made of the Tertiary sediments in almost all the countries and islands of Middle America. As a result a regionally applicable foramniniferal time-scale has been developed.

The availability of two independent time-scales for regional geo-chronology might appear advantageous. For instance, certain sediments are rich in megafossils and poor in microfossils and vice versa: hence it would seem possible to make more complete correlations with the two time-scales than with only one. Unfortunately the two schools are not in agreement on the equivalence of their time-divisions with the standard subdivisions of the European Tertiary. Two examples may be cited, viz (1) Kleinpell has shown that in California the Miocene of the inolluscan time-scale includes beds, as old as the Middle Oligocene of the foraminiferal timescale; (2) In Peru the Upper Eocene to Middle Oligocene of the molluscan time-scale matches the Middle to Upper Eocene of the foraminiferal time-scale (see symposium, 1949)

Discrepancies between the molluscan and foraminiferal time-scales can lead to erroneous correlations. For instance, in a compilation on the Maracaibo Basin Sutton dated the Carbonera formation Middle Oligocene (by the molluscan time-scale) and the Paují formation Upper Eocene (by the foraminiferal time-scale). Actually it is reasonably certain that the two formations are of time same age but different facies. Errors such as this are not merely undesirable in themselves, but they can lead to grotesque distortions of paleogeographic maps and concepts.

Paleontologists are well aware of the shortcomings of the dual system, but many are content with a laissez-faire attitude or a biased support of either the molluscan or the foraminiferal time-scale. In the Antillean-Caribbean region few efforts have been made towards improving the situation, though the work of the Commitee on Stratigraphy of the U. S. National Research Council must he mentioned (cf. Cook, Gardner and Woodring, 1943). Corrective measures which might be taken are

(i)   replace the disputed terms (Eocene, Oligocene Miocene and their sub-epochs) by stage-names based on type-sections within the region, e. g. Jackson (-ian), Midway (-an).

(ii) achieve constructive cooperation between the molluscan and foraminiferal specialists with a view to forming a composite time-chart based equally on the two groups of fossils.

H. H. Renz deserves high credit for introducing the stage-concept in northern South America and the seed he has planted deserves to flourish. The value of certain foraminifera for long-range correlation in Middle America has been shown in compilations by Caudri, Grimsdale, Hedberg, Renz, Stainforth and others, but the writer is not familiar with any comparable papers in support of the molluscan time-scale.

The present paper began as an attempt to reconcile the differences between the molluscan and foraminiferal timescales as used in Middle America. The initial aim was to integrate the two time-scales by objective methods and to correlate them interdependently with the recognized timedivisions of the Gulf Coast Tertiary. The approach visualised was to prepare a composite chart showing the vertical and geographic ranges of the most useful index-fossils, regardless of phylum. The ideal index-fossil would be a species or genus of distinctive form, short vertical range, and wide geographic spread. As a start, individual charts would be prepared for the mollusks, the larger foraminifera and the smaller foraminifera. The writer's attitude at the start of the investigation may he expressed by a quotation from Weaver (1944, p. 571), written in reference to the dual timescale used in the Pacific Coast region: “…both schools of specialists are essential, each supplementing the work of the other, and the use of two independent schemes of classification in this province is natural if not inevitable. The two schemes can be integrated and arranged side by side (on a chart) so that any portion of either corresponds in time with the apposed part of the other. Thus a given formation would be placed in the same position in the chart by both schools…” This attitude was later modified by the results of the study, as will be shown below.

Figures 1, 2 and 3 are index-fossil range charts of separate phyla. Each chart shows ten columns for geographic sectors and seven horizontal time-divisions. The geographic divisions represent the Gulf Coast States, the West Indies, Central America, northern South America, Ecuador and Peru. California has been omitted as it has customarily been included in the Pacific Coast region, but many of the index fossils recorded on these charts occur at corresponding levels in California. The seven time-divisions are expressed in standard terms as usually accepted for the main Gulf Coast and West Indian Tertiary stages, i. e. Midway, Wilcox, Claiborne, Jackson, Vicksburg, Antigua and Anguilla. The Middle (Antigua) and Upper Oligocene (Anguilla) are less firmly established than the older sub-epochs: this is partly because of the paucity of Oligocene outcrops, partly because of non-marine and unfossiliferous sections, and partly because the available faunas are dated differently in the molluscan and foraminiferal time-scales. Selected index fossils are marked on the charts by large capital letters corresponding to the keys below the figures. Selection was based on the paleontological literature of the region, special attention being paid to the species stressed by authors in their attempts to date local sections. Individual annotations are not offered in this brief paper but all entries are covered by the appended list of references. In all cases of disputed age-assessment the foraminiferal time-scale has been used in order to be consistent.

Figure 1 shows the distribution of some of the larger foraminifera. The genus Ranikothalia ( = Miseellanea = Pellatispirella of authors) occurs in the Paleocene of several countries. In Florida Miscellanea sp. has been recorded in the Lower Eocene and this probably correlates with the presence of Miscellanea antillea in the Capdevila formation of Cuba. The form "Operculina" bermudezi is believed to be a Cretaceous species with allochthonous records in the Paleocene of Cuba. A community of Discocyclinas (s.s.) and conical Amphisteginas of the lopez-trigoi tribe (genus Tremastegina of Bronnimann) characterises the Middle Eocene of most mid-American countries. Later in the Middle Eocene the genus Helicolepidina makes its first appearance in several countries, though in others it has not yet been recorded below the basal Upper Eocene. The species Helicostegina soldadensis is a useful marker for the Upper Eocene of Trinidad, Venezuela, Ecuador and Peru but has not yet been noted farther north. The Oligocene is characterised by a group of Lepidocyclinas including L. supera, L. favosa ( = ephippioides, L. gurnagunensis, etc. The chart records the first appearance of these species near the Eocene/ Oligocene boundary. The genus Miogypsina appears abruptly in the late Middle Oligocene of the entire region. The only country in which it is not yet recorded is Colombia, but it occurs in Ecuador only a short way south of the Colombian frontier.

 

Fig. 1         DISTRIBUTION OF LARGER FORAMINIFERA IN THE TERTIARY OF MIDDLE AMERICA

 

GULF COAST

CUBA

WEST INDIES (VARIOUS)

TRINIDAD

VENEZUELA

MEXICO

PANAMA

COLOMBIA

ECUADOR

PERU

 

UPPER

OLIGOCENE

 

 

 

 

 

 

 

 

 

 

 

MIDDLE

OLIGOCENE

F

F

F

F

F

F

F

 

F

F

 

LOWER

OLIGOCENE

E

E

E

E

E

E

 

 

E

 

 

UPPER

EOCENE

C

 

 

D

C

D

C

 

C

C

D

C

B

D

C

B

 

MIDDLE

EOCENE

B

B

B

B

 

C

B

B

 

 

LOWER

EOCENE

A

A

 

 

 

 

 

 

 

 

 

PALEOCENE

 

?A

A

A

A

A

 

 

 

 

KEY

A: the genus Ranikothalia ( = Pellotispirella = Miscellanea of authors)

B: on association of Discocylcinas (sensu stricto) with conical Amphisteginas (= the genus Tremastegina of Bronnimann)

C: first appearance of the genus Helicolepidina

D: the species Helicostegina soldodensis

E: fret appearance of Lepidocyclinas of the species group L. supera,  L. favosa ( ephippioides), L. yurnagunensis, etc.

F: first appearance of the genus Miogypsina

Figure 2 shows the regional distribution of certain smaller foraminifera. A very distinctive fauna of arenaceous species, such as Rzehakina epigona vars., Spiroplectammina clotho, Trocliammina globigeriniformis, etc, marks the basal Tertiary of the more southerly countries. A recent paper by Bolli appears to establish this fauna as definitely Midway, although in the previous literature many authors referred it to pre-Midway Tertiary ("Danian") or to the late Cretaceous. Eventually the Paleocene Gioborotalias (G. velascoensis, G. crassata vars., etc.) will probably be recognized as key fossils for regional correlation, but they are omitted from the chart because at present authors are not fully agreed on their status. In the Lower and Middle Eocene the more primitive forms of Hantkenina appear, i. e. the subgenera Aragonelia and Applinella. These evolve into the more advanced forms which are widespread in the Upper Eocene, especially the group of H. alabamensis. The chart follows certain authors in extending the range of this species into the basal Oligocene of the Gulf Coast, but other equally competent authorities have asserted that the records in question are based on allochthonous specimens. In most countries just above the level of extinction of Hantkenina the cuneate species Bulimina jacksonensis evolves rather abruptly into the slender Bulimina sculptilis: the time-plane so marked is the Eocene/ Oligocene boundary. A pronounced faunal change coincides with the regional mid-Oligocene transgression. At this level the planktonic genera Orbulina and Globigerinoides appear in abundance and many distinctive benthonic species appear abruptly, such as Sipliogenerina trans versa vars., Uvigerina rustica, Uvigerina gallowayi, Pseudo glandulina comatula, and many others.

 

Fig. 2         DISTRIBUTION OF SMALLER FORAMINIFERA IN THE TERTIARY OF MIDDLE AMERICA

 

GULF COAST

CUBA

WEST INDIES (VARIOUS)

TRINIDAD

VENEZUELA

MEXICO

PANAMA

COLOMBIA

ECUADOR

PERU

 

UPPER

OLIGOCENE

 

 

 

 

 

 

 

 

 

 

 

MIDDLE

OLIGOCENE

E

E

E

E

E

E

 

E

E

E

 

LOWER

OLIGOCENE

C D

 

D

C

 

 

D

C

 

D

C

 

D

C

 

D

 

D

C

 

D

C

 

UPPER

EOCENE

C

C

 

MIDDLE

EOCENE

B

B

 

B

B

B

 

 

 

 

 

LOWER

EOCENE

 

B

 

B

 

B

 

 

 

 

 

PALEOCENE

 

 

 

A

A

A

 

 

A

A

KEY

A: a suite of arenaceous foromnifera including Rzehokino epigona vars., Spiroplectommina clotho, Trochommina globigeriniformis, and other very distinctive species.

B: the more primitive forms of Hantkenina i.e. the subgenera Arogonelia and Applinella

C: the more advanced forms of Hantkenina especially H. alabamensis

D: the level of evolutionary change upwards from Bulimina jacksonensis to Bulimina sculptilis

E: first appearance of the planktonic genera Orbolina and Globigerinoides and many distinctive benthonic species, including Siphogenerina transversa vars., Uvigerina rustico, Uvigerina gallowayi, etc., etc.

Figure 3 was intended to show the distribution of molluscan index-fossils, but it proved so difficult to find species of truly regional importance that certain non-molluscan megafossils have been included. The impression gained from the literature is that for any pair of adjacent countries (such as Venezuela and Trinidad or Colombia and Panama) numerous mollusks of restricted range are available for stratigraphic correlation, but the majority of these markers are only of local value. Species and genera with wide geographic spread tend to have long vertical ranges. The complex species-group of Venericardia planicosta vars. is widespread and confined to the Paleocene and Eocene, but the validity of its members for ident ification of sub-epochs is dubious. The peculiar gastropod Tubulostium has a wide distribution in the Upper Eocene and is recorded in the Middle Eocene of the Gulf Coast (also California). The gastropod Glyptostyla (Peruficus) is not a truly regional index but has assisted correlation of the Upper Eocene in Panama, Colombia and Peru. A group of cold-water pelecypods, especially Thyasira and Acila, has a reputation as an Oligocene index, but in Ecuador and Peru they occur in the Upper Eocene. Since their only records are in the Pacific Coast countries (where cold ex-polar currents have probably been a long-existing feature) and in the deep-water marls of Trinidad, it seems probable that their presence reflects ecologic factors as much as time factors. Another assemblage which appears to be partly facies-controlled in its distribution is the "Hannatorna fauna", an association of brackish-water mollusks (Hannatoma, Ampullinopsis, Pseudofaunus, etc.) found at scattered localities in the southerly countries. The latest published opinion is that this fauna is usually Upper Eocene but may range as high as the Middle Oligocene. In particular Hannatoma emendorferi appears to be confined to the Upper Eocene whereas the species H. gesteri and H. tumbezia may be Oligocene. At the end of the Oligocene the first appearances are noted of various molluscan genera which became abundant and widespread in the Miocene: Dosinia and Chione are representative. Non-molluscan megafossils marked on the chart are (1) coral assemblages typical of Middle Eocene, Middle Oligocene and Upper Oligocene (after Vaughan, 1919) and (2) barnacles of the Balanus group, of little intrinsic value but previously cited in discussion of the dual time-scale (Olsson and Pilsbry, 1949).

 

Fig. 3         DISTRIBUTION OF KEY MEGAFOSSILS IN THE TERTIARY OF MIDDLE AMERICA

 

GULF COAST

CUBA

WEST INDIES (VARIOUS)

TRINIDAD

VENEZUELA

MEXICO

PANAMA

COLOMBIA

ECUADOR

PERU

 

UPPER

OLIGOCENE

J

I

I

J

I

E

J

 

J

I   G

 

J

J

E

 

MIDDLE

OLIGOCENE

H

H

H

 

 

H

H  F?

F?

E  F

G

G  F?

 

LOWER

OLIGOCENE

 

 

 

 

 

 

 

 

G

 

 

UPPER

EOCENE

A

C

A  C

C

F   C

 

D

F  D

E  F

C

E F  G

D  A

 

MIDDLE

EOCENE

A,  C

 

B

 

 

A, B

 

 

 

A

 

LOWER

EOCENE

A

 

 

 

A

A

 

A?

 

A

 

PALEOCENE

A

 

 

A

A

 

 

A?

 

A

KEY

A: the molluscon species group of Venericardia planicosta vars.

B: Middle Eocene corals

C:  the molluscan genus Tubulostium

D: the molluscan genus Glyptostylo (= Peruficus)

E: the cold-water molluscs Thyosira, Pleurophopsis, Acila, etc.

F: molluscs of the brackish-water "Hannatoma fauna"

G: barnacles of the Balanus type

H : Middle Oligocene corals

I: Upper Oligocene corals

J : first appearance of the molluscan genera Dosinia and Chione

To comply with the original scheme of this paper the next step would be to integrate the three charts discussed above. However, the results of plotting the available data have compelled the writer to modify his original attitude. On the one hand we have the two foraminiferal charts, which independently or interdependently provide a clear-cut basis for accurate regional correlation. To avoid congestion the entries have been kept to a minimum but both charts could he supplemented by other well-known index fossils. Other larger foraminifera of regional spread and restricted range are Asterocyclina, Dictyoconus, Ferayina and the subgenera of Lepidocyclina and Miogypsina. Likewise the smaller foraminifera include various Globorotalias in the Paleocene and Eocene, the dominance of Globigerina dissimilis and G. ef. concinna in the Lower Oligocene planktonics and other shortrange planktonic species such as Globorotalia fohsi vars., Globigerinatella insueta and Globigerina grimsdalei for subdivision of the younger Oligocene. The empirical evidence of their orderly distribution on a regional scale is backed by our knowledge of well-defined evolutionary trends in the larger foraminifera and of the ocean-wide, facies-free distribution of the smaller planktonic foraminifera. In strong contrast, on the other hand, we have the chart of megafossil distribution. The only two entries with a regional status comparable to the index foraminifera are the Upper Eocene Tubulostium and the late Oligocene Chione-Dosinia association. The only evolutionary trend is in the Venericardia planicosta clan, but the family tree postulated by Gardner and Bowles for the Gulf Coast forms does not match the records of Olsson for the Peruvian varieties. Not entered on the chart are the Tertiary nautiloids: the records of Miller suggest an evolutionary development of species, but the pattern is not in accord with the age-assessments currently accepted.

Only one logical conclusion can be drawn from comparison of the distribution charts. It is that the foraminifera have a natural and empirical right to provide the basis for regional correlation. By reference to index-foraminifera direct correlations can be made between places as far apart as Florida and Peru or Mexico and Trinidad. Long-range correlations based on mollusks can seldom be based on direct evidence, but instead most be based on indirect and roundabout comparisons of faunas. The writer is therefore of the opinion that the most satisfactory approach to regional correlation is, firstly, to identify local sections as far as possible in direct terms of the regional foraminiferal timescale and, secondly, to utilise megafossils (and microfossils other than the index forms) for provincial correlations to fill in the remaining gaps on the correlation chart.

It remains to be stated that the writer of these comments is by experience a specialist in the smaller foraminifera. He has attempted to be completely objective in his approach but it is possible that, through lack of knowledge of molluscan synonymy or lack of important literature, he has failed to make the best case for the mollusks. If the molluscan experts should produce a chart to replace Figure 3, showing an orderly regional spread of index-mollusks, he would revert to his original view that the foraminiferal and molluscan charts should he integrated as a basis for mid-American Tertiary stages to replace the unsatisfactory European terms.

REFERENCES

The principal papers cited are listed below. Several of them are summaries and compilations with extensive lists of subsidiary references.

APPLIN, P. L. and APPLIN, E. R. 1944 Regional subsurface stratigraphy and structure of Florida and southern Georgia. Amer. Ass. Petr. Geol., Bull., vol. 28, no. 12, pp. 1673-1753.

BARKER, R. W. and GRIMSDALE, T. F. 1936 A contribution to the phylogeny of the orbitoidal foraminifera, with descriptions of new forms from the Eocene of Mexico. Jour. Pal., vol. 10, no. 4, pp. 231-247.

BERMUDEZ, P. J. 1949 Tertiary smaller foraminifera of the Dominican Republic. Cushman Lab. Foram. Res., Spec. PubI. no. 25.

BERMUDEZ, P. J. 1950 Contribución al estudio del Cenozoico cubano. Soc. Cubana Hist. Nat., mem., vol. 19, no. 3.

BOLLI, H. 1952 Note on the Cretaceous-Tertiary boundary in Trinidad, B. W. I. Jour. Pal., vol. 26, no. 4, pp. 669-675.

BRONNIMANN, P. 1950 The genus Hantkenina Cushman in Trinidad and Barbados, B. W. I. Jour. Pal., vol. 24, no. 4, pp. 397-420.

CAUDRI, C. M. B. 1944 The larger foraminifera of San Juan de los Morros, State of Guarico, Venezuela. Bull. Amer. Pal., no. 114.

DE CIZANCOURT, M. and FRIZZELL, D. L. 1949 Ferayina in the Middle Eocene of Venezuela. Jour. Pal., vol. 23, 5, pp. 496-497.

COLE, W. S. and GRAVELL, D. W. 1952. Middle Eocene foraminifera from Pañon Seep, Matanzas Province, Cuba. Jour. Pal., vol. 26, no. 5, pp. 708-727.

COOK C. W., GARDNER, J. W. and WOODRING, W. P. 1943 Correlation of the Cenozoic formations of the Atlantic and Gulf Coastal Plain and the Caribbean region. Geol. Soc. Amer., Bull. vol. 54, pp. 1713-1722 and chart.

CUSHMAN, J. A. 1935 Upper Eocene foraminif era from the southeastern United States. U. S. Geol. Surv., Prof. Paper 181.

CUSHMAN, J. A. 1946 Upper Cretaceous foraminifera of the Gulf Coastal region of the United States and adjoining areas. U. S. Geol. Surv., Prof. Paper 206.

CUSHMAN, J. A. 1951 Paleocene foraminifera of the Gulf Coastal region of the United States and adjacent areas. U. S. Geol. Surv., Prof. Paper 232.

CUSHMAN, J. A. and RENZ H. H. 1946 The foraminiferal fauna of the Lizard Springs formation of Trinidad, B. W. I. Cushman Lab. Foram. Res., Spec. PubI. 18.

DAVIES, A M. 1934 Tertiary faunas: Vol. II, The sequence of Tertiary faunas Murby and Co., London.

DROOGER, C. W. 1952 Thesis: Study of American Miogypsinidae Vonk and Co., Zeist, Netherlands.

DROOGER, C. W. 1953 Two species of Miogypsina from southern Peru. Bol. Soc. Geol. Peru, T. XXVI.

FRIZZELL, D. L. 1943 Upper Cretaceous foraminif era from northwestern Peru. Jour. Pal., vol. 17, no. 4, pp. 331-353.

FRIZZELL, D. L. 1949 Rotaliid foraminifera of the Chapmaninae: their natural distinction and parallelism to the Dictyoconus lineage. Jour. Pal., vol. 23, no. 5, pp. 481-495.

GARDNER, J. A. and BOWLES, E. 1939 The Venericardia planicosta group in the Gulf Province. U. S. Geol. Surv., Prof. Paper 189-f.

GIGNOUX, M. 1950 Géologie stratigraphique. (4e. edn.) Masson et Cie., Paris.

GRIMSDALE, T. F. 1951 Correlation, age determination, and the Tertiary pelagic foraminifera. Third World Petr. Congr., Proc. Sect. 1, pp. 463-475. Leiden, Netherlands.

HEDBERG, H. D. and PYRE, A. 1944 Stratigraphy of northeastern Anzoategul, Venezuela. Amer. Ass. Petr. Geol., Bull., vol. 28, no. 1, pp. 1-28.

HODSON, F. and H. and HARRIS, G. D. 1927 Some Venezuelan and Caribbean mollusks. Bull. Amer. Pal., no. 49.

LE ROY, L. W. 1948 The foraminifer Orbulina universa d'Orbigny a suggested middle Tertiary time indicator. Jour. Pal., vol. 22, no. 4, pp. 500-508.

LOWMAN, S. W. 1949 Sedimentary facies in Gulf Coast. Amer. Ass. Petr. Geol., Bull., vol. 33, no. 12, pp. 1939-1997.

MILLER, A. K. 1947 Tertiary nautiloids of America Geol. Soc. Amer., Mem. 23.

MILLER, A. K. and DOWNS, H. R. 1950 Tertiary nautiloids of the Americas: a supplement. Jour. Pal., vol. 24, pp. 1-18.

MUIR, J. M. 1936 Geology of the Tampico region, Mexico. Amer. Ass. Petr. Geol., special publication.

NOTESTEIN, F. B., HUBMAN, C. W. and BOWLER, J. W. Geology of the Barco Concession, Republic of Colombia, S. A. Geol. Soc. Amer., Bull., vol. 55, no. 10, pp. 1165-1216.

OLSSON, A. A. 1928-1931 Contributions to the Tertiary paleontology of northern Peru. Bull. Amer. Pal., nos. 52, 57, 62, 63.

OLSSON, A. A. 1942 Tertiary deposits of northwestern South America and Panama. 8th Amer. Sci. Congr., Proc., vol. 4 (was not available to the writer).

OLSSON, A. A. and PILSBRY, H. A. 1949 Balanus in the Oligocene of northern Peru and western Ecuador. Soc. Geol. Perú, Bol., vol. jubilar, part 2, fasc. 6.

RENZ, H. H. 1942 Stratigraphy of northern South America, Trinidad and Barbados. 8th Amer. Sci. Congr., Proc., vol. 4, pp. 513-571.

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

RUTSCH, R. 1939 Die Gattung Tubulostium im Eocaen der Antillen Eclog. Geol. Helv., vol. 32, nr. 2, pp. 231-244.

SENN, A., 1948 Die Geologie der Insel Barbados, B. W. I. (Klelne Antillen) und die Morphogenese, der umliegenden marinen Grossformen. Eclog. Geol. Helv., vol. 40, nr. 2, pp. 199-222.

STAINFORTH, R. M. 1948 Applied micropaleontology in coastal Ecuador. Jour. Pal., vol. 22, no. 3, pp. 113-151.

STAINFORTH, R. M. 1948 Description, correlation and paleo-ecology of Tertiary Cipero marl formation, Trinidad, B. W. I. Amer. Ass. Petr. Geol., Bull., vol. 32, no. 7, pp. 1292-1330.

SUTTON, F. A. 1946 Geology of the Maracalbo Basin, Venezuela Amer. Ass. Petr. Geol., Bull., vol. 30 no. 10, pp. 1621-1741.

SYMPOSIUM 1949 The age of the Hannatoma fauna of South America. Jour. Pal., vol. 23, no. 2, pp. 145-160.

THALMANN, H. E. 1942 Foraminiferal genus llantkenina and Its subgenera. Amer. Jour. Sci., vol. 240, pp. 809-820.

WEAVER, C. E. et al. 1944 Correlation of the marine Cenozoic formations of western North America. Geol. Soc. Amer., Bull. vol. 55, pp. 569-598 and chart.

VAUGHAN, T. W. 1918 Geologic history of Central America and the West Indies during Cenozoic time. Geol. Soc., Amer., Bull. vol. 29.

VAUGHAN, T. W. 1919 Fossil corals from Central America, Cuba and Porto Rico with an account of the American Tertiary, Pleistocene and Recent coral reefs. U. S. Nat. Mus., Bull. 103.

VAUGHAN, T. W. 1945 American Paleocene and Eocene larger foraminifera. Geol. Soc., Mem. 9, pt. 1.

WOODRING, W. P., BROWN, J. E. and BURBANK, W. S. 1924 Geology of the Republic of Haiti, Rep. of Haiti, Dept. of Public Works.

WOODRING, W. P. and THOMPSON, T. E. 1949. Tertiary formations of Panama Canal Zone and adjoining parts of Panamá. Amer. Ass. Petr. Geol., Bull., vol. 33, no. 2, pp. 223-247.



[1] The International Petroleum Company is thanked for providing library facilities and permitting publication of this paper.

[2] Chief paleontologist International Petroleum Company, Talara, Peru. This paper discusses one regional facet of a worldwide problem in stratigraphy.