SANTA BARBARA, Sand Member

TERTIARY (upper Oligocene or lower Miocene)

State of Zulia, Venezuela

Author of name: J. B. Burnett, W. H. Spice, Jr., W. S. Hoffmeister and H. D. Hedberg, 1927 (private report).

Original reference: R. A. Liddle, 1928, p. 404.

See LA ROSA, Formation.

LA ROSA, Formation

TERTIARY (upper Oligocene or lower Miocene)

State of Zulia, Venezuela

Authors of name: J. B. Burnett, W.H. Spice, Jr., W.S. Hoffmeister and H.D. Hedberg, 1927 (private report)

Original reference: R. A. Liddle, 1928, p. 404.

Original description: ibid.

Maury (1925, p. 411) created an obsolete senior synonym of the La Rosa formation when she wrote: "Miocene". "Lower. -Los Quiros beds of eastern Zulia, east of Lake Maracaibo. Equivalent to the Manzanilla beds of Trinidad; the Cercado formation, Dominican Republic; and the Uscari formation". Los Quiros is a misspelling of Quiroz, a small village in the southeastern part of the District of Miranda in northeastern Zulia.

Garner (1926, p. 680) established two obsolete senior homonyms, the La Rosa coal measures and the La Rosa sandstone. These were later respectively referred to the Marcelina formation and the Misoa formation by Sutton (1946, p. 1664, 1669), who explained that the name La Rosa was in each case an error for Santa Rosa. Garner (1926, p. 682-683) also published two obsolete senior synonyms of the La Rosa formation. His Quirós (correctly Quiroz) formation is the same unit as the Los Quiros beds of Maury. His Río Chiquito formation is exposed along the river of that name in the northeast part of the District of Bolívar in eastern Zulia. Garner assigned both formations to the Miocene.

F. Hodson (1926) consistently gave the age of his Locality N° 6 as Oligocene-Miocene. This locality is at El Mene de Saladillo in Garner's Quiroz formation, 1,5 kilometers southwest of the village of Quiroz, and it is the most prolific fossil locality in the Quiroz formation.

J. B. Burnett, W. H. Spice, Jr., W. S. Hoffmeister and H. H. Hedberg (1927, private report) divided the La Rosa Series (1000-1900 feet thick) into the Lower La Rosa Series (100-800 feet thick), the Middle La Rosa Series (400-600 feet thick) and the Upper La Rosa Series (500 feet thick). The La Rosa Series was named after the subsurface section in the La Rosa oil field and was considered equivalent to the exposed on the surface at Quiroz. The Lower La Rosa series included the Santa Bárbara sands and the Intermediate sands, and was divided into the Cadulus zone and the Microdrillia zone in the Ambrosio field. The Middle La Rosa Series included the La Rosa sand, the Tar Sand zone and the Lignitic Series. The Upper La Rosa Series consisted of "gray to blue or brown soft clays with intercalated sands and was unfossiliferous. It seems probable that some of these names may have been employed prior to 1927, but, if that is the case, the writer has failed to find the evidence for it.

F. and H. K. Hodson (1927) again placed Locality N° 6 in the Quiroz formation at El Mene de Saladillo in the "Oligocene-Miocene".

Liddle (1928, p. 268-269) included the Quiroz fossil localities in the upper Oligocene Agua Clara formation. His description of the La Rosa field in the same publication (p. 404) contained the first published description of what is now the type La Rosa formation. The pertinent quotations are: "Local steep dip and faulting in Lower Miocene and Upper Oligocene sediments. Fossils from wells correlate with Quirós oil sands of Upper Oligocene age". "Producing horizon. - Original source in sands, shales and thin limestones of Upper Oligocene age". "Sands locally divided into an upper zone or La Rosa sand, and a lower zone or Santa Bárbara sand. Interval between two sands not uniform, but generally from 100 to 200 feet".

Hedberg (1928, p. 37-42) did not mention the La Rosa by name but described its heavy minerals and listed a few of its foraminifera and bryozoa by genera only. He assigned a Miocene age to these microfossils.

J. B. Burnett (1929, private report) likewise considered the La Rosa to be Miocene. He divided it into a Lower La Rosa series and an Upper La Rosa series, thus eliminating the Middle La Rosa Series. The La Rosa sand of the old Middle La Rosa Series was added to the Lower La Rosa series, while the Tar Sand zone and the Lignitic Series were put in the Upper La Rosa series. The strata, principally shales, between the top of the Santa Bárbara sand and the base of the La Rosa sand, and embracing the Intermediate sand, were termed the Intermediate shales.

F. and H. K. Hodson (1931) changed their age assignment of their Locality N° 6 at El Mene de Saladillo in the Quiroz formation from "Oligocene-Miocene" to "Upper Oligocene".

W. S. Hoffmeister (1933, private report) split the Microdrillia zone into the Bolivina subzone below and the Cibicides subzone above.

Hedberg and Sass (1937, p. 99-102) introduced the name La Rosa formation to replace the Lower La Rosa series and the name Lagunillas formation to replace the Upper La Rosa series. According to these authors, the type locality of the La Rosa formation is the La Rosa field on the east side of Lake Maracaibo in the District of Bolívar, State of Zulia. There the formation is some 180-250 meters thick and consists largely of greenish, more or less fossiliferous clay shale with a lesser amount of sandstone and interlaminated sandstone and shale. On the west side of the lake the formation varies in thickness from 0 to 125 meters and consists almost entirely of green fossiliferous clay shale with a very minor amount of sandstone. It "rests conformably on sediments of the Icotea or El Fausto formations and is overlain conformably by the Lagunillas formation. The La Rosa formation constitutes a tongue extending westward from the marine section of the State of Falcón into the essentially non-marine Neogene deposits of the Maracaibo basin. It thins westward from its type locality and in the western part of the District of Urdaneta grades laterally into the upper part of the El Fausto formation or the lower part of the Los Ranchos (Lagunillas) beds". The authors stated that the fauna from the west side of the lake is more limited in variety than that of the Bolívar Coastal fields but is otherwise identical; that fossils indicate that the La Rosa formation may be correlated with the upper part of the Agua Clara formation of the State of Falcón, and that the age of the fauna is near the border line between Oligocene and Miocene, corresponding approximately to the Aquitanian stage.

M. W. Haas and R. G. Hubman (1937, p. 119-127) were still using the terms Upper La Rosa Series and Lower La Rosa Series. Their chart of "formational nomenclature" showed the Upper La Rosa Series of Lago Petroleum Company equivalent to the Lagunillas Formation of Venezuelan Gulf Oil Company and the Lagunillas Series of Venezuelan Oil Concessions, Ltd.; and the Lower La Rosa Series of Lago Petroleum Company equivalent to the La Rosa Formation of Venezuelan Gulf Oil Company and the La Rosa Series, divided into Upper and Lower portions, of Venezuelan Oil Concessions, Ltd. It was not until 1943 that all three companies decided to use the terminology of the Venezuelan Gulf Oil Company, i. e., Lagunillas formation and La Rosa formation. For further description of the Upper La Rosa Series, see the article on the Lagunillas formation.

Haas and Hubman wrote: "The type locality for the Lower La Rosa Series sediments is in the Icotea Syncline. These sediments consist of hard, massive, occasionally micaceous and carbonaceous, fossiliferous, gray, bluegray, and green clays. Frequently black clays occur at the base of this series. Thin siderite beds are rather abundant". "In the northern areas, where this series of sediments is best developed, three bodies are present; a basal, an intermediate and an upper sand. The sands are soft, fine to coarse-grained, petroliferous and have an over-all thickness varying from a few feet to more than sixty feet".

"The marine section is abundantly fossiliferous, and, in general, it is discriminated from the younger marine horizon of the Upper La Rosa Series by (1) the presence of distinctive genera such as Archaias, Miogypsina and Sorites, (2) the presence of distinctive species of the genera Bolivina, Bulimina, Cassidulina, Robulus and Uvigerina, (3) a greater abundance of individual genera and species common to both horizons and (4) a distinctive preservation of the forms in the younger marine horizon of certain localities".

Haas and Hubman were the first authors to publish Hoffmeister's Cibicides subzone and Bolivina subzone, together with the foraminiferal genera found in each, and the statement that the maximum transgression of the Lower La Rosa sea took place during the position of the Bolivina subzone. Their "Barren Subzone" is a misnomer. It should have been termed the "Barren Zone", for it is the lateral equivalent of the Cadulus zone.

Manger (1938, p. 57-67) wrote: "The type locality for the La Rosa formation is in the La Rosa field, which is situated in the vicinity of the villages of Cabímas and La Rosa in the northern part of the District of Bolívar, State of Zulia. The formation reaches its maximum thickness of about 230 meters (750'), however, in the Icotea syncline, located about four kilometers to the north of the center of the La Rosa field At the type locality the formation consists of grayish green fissile shales frequently roughly interlaminated or interbedded with medium to fine-grained gray, very friable sandstones, greenish gray clay-shale locally with pockets of mediumto fine-grained sandstones, friable, coarse to medium-grained, thick-bedded sandstones, and a few blackish gray shales. Lenticular brown clay-ironstone concretions along bedding planes are common in the clay-shales. Fossils occur throughout the formation and macroscopic fossils are particularly abundant in some of the thicker-bedded argillaceous, calcareously cemented sandstones; in these latter rocks dark green glauconite pellets are common. Clusters of pyrite are common in the clay-shales".

"In the La Rosa area, i. e., from the Ambrosio field southward to Punta Benítez, the formation is frequently marine throughout, but often brackish water sediments form both the initial and final phases of the marine cycle of sedimentation. Outside the La Rosa area, the formation is characterized by an alternation of brackish water and marine sediments particularly at the upper and lower limits of the typical marine beds".

"The formation extends from its outcrop area several kilometers north of the village of Ambrosio southward along the coast to at least as far as southern Bachaquero; however, in the southern Lagunillas area and probably also over the Pueblo Viejo "high", the eastern boundary of the formation is several miles offshore".

"In the type locality the formation is divisible into four zones which are established principally upon difference of the composition of detrital mineral suites and to a minor degree upon Ethology and paleontology. In order of decreasing age these zones are the lower Santa Bárbara, the upper Santa Bárbara, the "Marine Green Claystone" and the "La Rosa Sand"; the first two and the last of these zones correspond to the oil bearing sand sections of this formation".

According to Manger, the type localities of both the lower and upper Santa Bárbara "zones" (actually members) are in the two Santa Bárbara leases of the Venezuelan Oil Concessions, Ltd., near the village of La Rosa in the La Rosa field. At the base of the lower Santa Bárbara the blackish gray shales occur. Above them are found grayish green fissile shales interbedded with friable sandstones. The detrital mineral glaucophane and clinozoisite are characteristic of this "zone", which has a maximum thickness in the Icotea syncline of 60 meters (200 feet). The upper Santa Bárbara consists of a lower unit of green fossiliferous shale with an average thickness of about 27 meters (90 feet), and an upper one of thick-bedded, poorly sorted sandstones from 9 to 18 meters (30 to 60 feet) in the thickness. The "Marine Green Claystone" overlies the upper Santa Bárbara and grades laterally and upward into the "La Rosa Sand", which consists mainly of thin-bedded medium-grained sandstones frequently irregularly interlaminated with greenish fossiliferous shales. These two "zones" have a combined maximum thickness of about 122 meters (400 feet). Throughout the Bolívar coastal area the La Rosa generally grades upward into the Lagunillas formation through some 3 to 9 mYeters (10 to 30 feet) of drab olive green clay-shale carrying micromollusks and foraminifera. The marine Agua Clara formation, the upper part of which is the equivalent of the La Rosa of the Bolívar coastal fields is much thicker to the east in the State of Falcón, hence the La Rosa sea transgressed from that direction.

Douglas (1938, p. 90) stated: "The La Rosa is believed to be of uppermost Oligocene or possibly Lower Miocene age".

Hoffmeister (1938, p. 103-110, 116-117) wrote: "Only described species found in outside areas and common to the La Rosa and Lagunillas formations are listed in this paper. The writer hopes at some future date to describe for publication the many new forms, both macro and micro, discovered in the material".

"Notwithstanding that some of the identifications are probably incorrect, close affinities are assured and therefore the faunal ltst is of value to the reader in securing an insight as to the age and character of the La Rosa and Lagunillas formations".

"The La Rosa formation may be defined as including those sediments of Lower Miocene age which were deposited on the Icotea beds of Oligocene age or on the old Eocene surface, and whose upward limits are marked by the termination of a favorable habitat for marine life. In 1928 the writer separated the La Rosa formation, according to the macrofaunal content, into a lower division, Cadulus zone, and an upper division, Microdrillia zone. On foraminiferal evidence this latter zone was divided into a lower horizon, Bolivina sub-zone, and an upper horizon, Cibicides sub-zone".

"The Cadulus zone represents the first invasion of the Lower Miocene sea upon the Eocene, and in places of low relief, upon the Icotea beds of Oligocene age. Its greatest thickness is found in southern Ambrosio and northern La Rosa, where 100 feet of section have been measured. From this area, like the overlying Microdrillia, zone, the Cadulus sediments thin to the south, . . . "

"The zone comprises about the lower one-fourth of the La Rosa formation. It is composed of sediments so poor in fossil content that it can be regarded in most sections of the Bolívar Coastal Fields as a barren interval between the overlying Microdrillia zone and the underlying Icotea beds or Eocene".

"This first invasion of the Lower Miocene sea was decidedly unfavorable for a good marine habitat. Shallow water prevailed as shown by the aspect of the fauna".

"At Ambrosio, where the Cadulus zone was first studied by the writer, a few poorly preserved mollusks were encountered among which was Cadulus (Gadilopsis) dentalinus Guppy, from which the sediments received their name. This species is perhaps the most persistent of the macrofossils found in the zone".

After listing 12 species of macrofossils found in the Cadulus zone, Hoffmeister continued: "Microdrillia zone. This zone received its name from a very small gastropod Microdrillia trina Mansfield, which, although not prolific, is generally found unmarred because of its small size. . . "

"Like the underlying Cadulus zone the Microdrillia faunal zone reached its greatest development in the northern part of the Bolívar Coastal Fields where a thickness of over one thousand feet has been measured. Southward the zone thins, . . . "

Hoffmeister then listed 83 species of macrofossils identified from the Microdrilfia zone. He continued:

"By definition the base of the Lagunillas formation is placed at the top of the marine fossils encountered in the underlying La Rosa. This contact is not always a true stratigraphic unit throughout the Bolívar Coastal Fields. Local unconformities undoubtedly separate the two formations in various parts of the area".

"In the Punta Benítez and Tía Juana fields, the upper part of the La Rosa is missing. Whether these sediments have been eroded or were never deposited in regions of high relief is problematic".

"Another proposed explanation for the disappearance of the upper part of the fossiliferous La Rosa may be advanced; that during deposition of these sediments in other regions of the Bolívar Fields where true marine conditions existed, material of brackish to fresh-water origin, as evidenced by the presence of Rotalia beccarii, were being laid down in areas of high relief. This would call for an interfingering of the marine Cibicides subzone with the brackish to fresh-water sediments typical of the lower part of the Lagunillas formation".

Hoffmeister then listed the fossils described from middle and lower Miocene formations of the Caribbean region that also occur in the La Rosa and Lagunillas formations. He showed the La Rosa and Lagunillas macrofaunas to be typical shallow marine waters and discussed the age and correlation of the La Rosa formation in these words: "There is still controversy among paleontologists regarding the age of the La Rosa formation. One group favors placing these sediments in the Upper Oligocene, while another group, including the writer, adheres to a Lower Miocene age. Arguments for both sides could be given at length but this would defeat the purpose of the paper. The close affinity of the La Rosa fauna to the classic Lower and Middle Miocene faunas of the Caribbean region testifies against an Upper Oligocene age".

"It is the writer's contention that the La Rosa formation can be correlated with the Upper Agua Clara formation of the State of Falcón".

"The sediments associated with the oil seepages at Quir¢s in the Miranda district, State of Zulia, furnished a good macrofauna which undoubtedly may be referred to the La Rosa. Woodring assigned a Lower Miocene age to this faunal assemblage".

Woodring (1928, p. 80-82) had mentioned that: "Some of the Turritellas described by Hodson (hubbardi, larensis, and gilbertharrisi) resemble species that elsewhere are found in beds now regarded as representing the lowermost Miocene zone (Anguilla horizon) ".

"Another collection from the Miranda District, Zulia, in the Maracaibo Basin (U. S. G. S. station 1/293), which contains the striking species Turritella zuliana Hodson, and also T. venezuelana Hodson ( ? T. tristis Brown and Pilsbry) and an Alveinus like the Chipola species A. rotundus Dall, represents about the same horizon".

Liddle (1946, p. 425-426, 434) again included the Quiroz oil sands in the upper Oligocene, Agua Clara formation but in addition mentioned Hoffmeister's correlation of the Quiroz with the La Rosa and Woodring's assignment of a lower Miocene age. Later (p. 453-455) he placed the La Rosa in the "Aquitanian, Upper Oligocene or Lower Miocene", and correlated it with the Cerro Pelado formation. He mentioned that: "Some geologists refer to the section as La Rosa formation; some refer to it as Lower La Rosa or Santa Bárbara series, reserving the Upper La Rosa series for beds which are referred to by others as Lagunillas formation." This sentence seems to be the result of Liddle's confusion of Lago Petroleum Company's Lower La Rosa series, which was the equivalent of the La Rosa formation, with Venezuelan Oil Concession's Lower La Rosa series, which was equivalent to the Santa Bárbara sand plus the overlying shale member. Nevertheless, the product is a new name, the Santa Bárbara series, equivalent to the La Rosa formation and an invalid unused synonym thereof.

Sutton (1946, p. 1692-1697) divided the La Rosa formation of the Bolívar Coastal field subsurface into (1) the basal Santa Bárbara sand member, composed of brackish-water to marine poorly consolidated sandstone, much of it highly argillaceous with common intercalations of gray or brown clay shale, (2) "a deeper-water, marine member composed chiefly of grayish green clay shale, interbedded with a few sandy shales and gray, thin, soft, commonly fossiliferous sandstones", (3) the Intermediate sand in the northern end of the Bolívar Coastal field, (4) "a section of interbedded gray clay shales, sandy shales and soft sandstones", (5) the La Rosa sand member, composed of "soft, poorly consolidated sandstones and sands", and (6) a few feet of overlying sandy shale and gray clay shale, normally highly fossiliferous, at the top of the formation. He included in the La Rosa formation the equivalent fossiliferous beds in the subsurface of the District of Urdaneta on the west side of Lake Maracaibo, in the surface in the Guanábana syncline in the northern part of the District of Bolívar, on the Cueva del Tigre anticline of the eastern part of the District of Miranda and on the Quiroz structure in southeastern Miranda.

According to Sutton, the La Rosa rests unconformably upon beds of the middle Oligocene Icotea formation or, where these are missing, on upper Eocene formations. Its upper boundary is conformable and gradational with the overlying Lagunillas f ormation. The southward and southeastward thinning and disappearance of the La Rosa in the southern Tía Juana and northern Lagunillas offshore areas of the Bolívar Coastal field, formerly thought due to erosion at an unconformity between the La Rosa and Lagunillas, is now known to be caused by an interfingering and lateral transition of the La Rosa with the lower part of the basal member of the Lagunillas. "The sandier parts of the La Rosa make the transition from fossiliferous marine to brackish water deposition first, thus allowing the fossiliferous green clay shale member to extend farther south than the remainder of the formation. It is very possible that a similar lateral transition may take place in the District of Urdaneta toward the west. The La Rosa formation constitutes a marine tongue extending from Falcón into the essentially non-marine Miocene of the Maracaibo basin".

Sutton followed Hoffmeister in assigning the La Rosa of the Bolívar Coastal field and the Quiroz area to the lower Miocene, and in dividing the La Rosa of the former region into faunal zones and subzones. He mentioned that the Cadulus zone corresponds to the Santa Bárbara sand, the Bolivina subzone of the Microdrillia zone to the overlying green clay shale member, and the Cibicides subzone to the remainder of the La Rosa, extending from the top of the green clay shale member to the base of the Lower Lagunillas sand. The type species of the subzones were identified for the first time as Bolivina marginata Cushman and Cibicides americanus (Cushman). "It should be noted that Cadulus dentalinus also occurs in the Microdrillia zone and that Cibicides americanus may be found in both the Bolivina subzone below and the Lithophaga zone of the Lagunillas formation above." Sutton then appended Hoffmeister's list of macrofossils with some additions and corrections by Dusenbury. These macrofossils "indicate a shallow, warm-water marine habitat of Lower Miocene (Burdigalian) age". "In the opinion of A. A. Olsson the fauna can be correlated with that from the Lower Miocene Cercado formation of the Dominican Republic".

Sutton considered Garner's Río Chiquito formation, the lower part of Garner's Quiroz formation and the "El Mene marine series" of Williston and Nichols (1928, p. 449) in the El Mene de Mauroa oil field in the western part of the District of Buchivacoa, western Falcón, to be obsolete synonyms of the La Rosa formation.

The Staff of the Caribbean Petroleum Company (1948, p. 536, 538-539), of which Venezuelan Oil Concessions, Ltd. was a subsidiary, divided the type La Rosa formation into the lower La Rosa and the upper La Rosa with the contact between these units of unspecified stratigraphic rank set at the base of the Intermediate sand. The lower La Rosa included the lower and upper Santa Bárbara sands with their intervening wedge of shale and the overlying shale up to the base of the Intermediate sand. The upper La Rosa contained the Intermediate sand, an unnamed shale section and the La Rosa sand, the top of this last sand corresponding to the top of the La Rosa formation. It was observed that: "Formerly, some controversy reigned regarding the age of the La Rosa formation, which was placed alternately in the lower Miocene or the upper Oligocene but today the Miocene age of the formation seems to be generally accepted." "The type locality of the La Rosa formation is the Cabimas field (formerly La Rosa field), where the formation reaches its maximum thickness (750 feet) in the Icotea syncline. It decreases in a short distance southward to approximately 130 feet and less in Tía Juana.... and approximately 90 feet in Bachaquero".

"The formation lies conformably on the Icotea formation where this is present, but it extends much farther than the Icotea and transgresses into the Eocene. The sharp lithological change from the Icotea to the La Rosa indicates some interruption in sedimentation, which is confirmed by the presence of a coaly shale at the top of the Icotea in the Cabimas field."

"The La Rosa formation is absent over many areas of the fields and apparently was deposited only in the lower parts of the region. In Cabimas it can be subdivided on paleontological evidence into upper and lower La Rosa, but this subdivision can be followed only as far as Tía Juana. Farther south the lower La Rosa seems to be absent, probably on account of progressive transgression".

According to Mencher et al. (1951, p. 26-27), the La Rosa thickens to about 1,000 meters at Quiroz. These same authors placed the La Rosa in the Oligo-Miocene (p. 47, correlation chart) and showed it resting unconformably upon the Icotea formation but conformably beneath the Lagunillas formation. It was indicated that the La Rosa sea was transgressive throughout the upper Oligocene and the lower part of the lower Miocene, and that it never became regressive.

It is now generally agreed that the type locality of the La Rosa formation is in the subsurface of the old La Rosa oil field. The names Santa Bárbara sand, Intermediate sand and La Rosa sand are all well intrenched in usage despite drawbacks in each case. The name Santa Bárbara sand (Liddle, 1928, p. 404) is burdened with several homonyms, the Santa Bárbara series of Christ (1927, p. 406), the Santa Bárbara beds of Liddle (1928, p. 354-355), later renamed the Santa Bárbara de Zamora beds by the same author (1946, p. 532-533), the Santa Bárbara facies of Kehrer (1938, p. 49), and the Santa Bárbara conglomerate of Blumenthal quoted by Tash (1937, p. 162). The name Intermediate sand should be replaced by a name of geographic derivation. The name La Rosa sand is all too easy to confuse with its homonym, the La Rosa formation, of which it is a member, and should also be renamed. The question as to whether the La Rosa formation rests conformably or unconformably upon the Icotea formation is still in dispute. The writer considers that the La Rosa grades laterally westward into the Macoa formation, southward into the Palmar formation and eastward into the Agua Clara formation. The La Rosa sea was not continually transgressive as depicted by Mencher et al. (1951, correlation chart). It was transgressive during the deposition of the Santa Bárbara sand, reaching a maximum area during the deposition of the overlying clay shales of the Bolivina subzone, and was regressive generally in the upper part of the formation, although with important fluctuations.

The controversy as to whether the age of the La Rosa formation is upper Oligocene or lower Miocene still continues in full force. Some paleontologists, chiefly specialists on mollusca, insist upon a lower Miocene age, upper Oligocene age. The writer believes that Hedberg and Sass (1937, p. 100) were probably correct in stating that the age of the La Rosa fauna corresponds approximately to the Aquitanian stage, and thinks that therefore the age of the La Rosa formation will never be settled until general agreement can be reached on whether the Aquitanian stage is upper Oligocene or lower Miocene. The Tampa formation of Florida, the Anguilla formation of the island of Anguilla in the Leeward Islands, the upper part (Globorotalia fohsi zone) of the Cipero formation of Trinidad, the upper part of the Carapita formation of eastern Venezuela, the Cojimar formation of Cuba, the Uscari formation of Costa Rica, the Globorotalia fohsi and Siphogenerina transversa zones of the Agua Salada group in eastern Falcón, the upper part of the Agua Clara formation of central and western Falcón are all placed in the Aquitanian by the writer, along with the La Rosa of Quiroz and the Bolívar Coastal field. Of the formations and zones mentioned, those determined as to age by mollusca have been called lower Miocene as a general rule, while those determined by foraminifera have been called upper Oligocene by most authors.

A. N. Dusembury, Jr.