CUMANA, Beds

TERTIARY (upper Miocene?)

State of Sucre, Venezuela

Author of name: A. von Humboldt.

Original reference: A. von Humboldt, 1801.

Original description: A. von Humboldt, 1823 ( ?), 1814-36.

The fossiliferous beds near Cumaná, like those near Cabo Blanco, have attracted the attention of geologists who have visited the region over since the time of Humboldt, but so far, neither the geology nor the fossils have ever been adequately described. Humboldt (1801) mentioned beds of "Floetzgebirge" near Cumaná and on Punta Araya, stating that they contained remains of various living genera (Pinna, Ostrea, "Venus''). In 1823, he thought that these beds and those at Cabo Blanco might be comparable with the "calcaire grossier" (actually middle Eocene) of the Paris basin. In his famous "Travels" (Humboldt, 1814-1836, 1816-1831) (which is readily accessible in the Spanish translation of Alvarado, 1941), he mentions "very recent formations" in the vicinity of the Castle of San Antonio in Cumaná and on the Peninsula of Araya (see Alvarado, 1941, p. 434-435).

Karsten (1886, p. 9) states that in Araya and in the hills of San Antonio, near Cumaná, there outcrops a porous limestone or shell breccia, covered by yellow or variegated marls which are locally gypsiferous and which contain shells belonging entirely to recent species (he gives a list, reproduced by Liddle, 1928, p. 353-354). A similar limestone (Karsten continues) is found in the regions of the coast near Clarines, Morro Unare, and Píritu; and a grey limestone, with fossils which indicate the same age, is found on the northern border of the Cumaná "massif", between the rivers Amana and Querecual; this limestone, he says, alternates with a grey sandstone containing impressions of plants and fragments of shells, and with clays which are locally gypsiferous. Similar beds, perfectly horizontal, are found on the Peninsula of Araya and the neighboring islands of "Guayguasa" and Alcatraz. He refers to all these beds as "Tertiary and Quaternary", without distinction.

According to Rutsch (1934), Etheridge published a list of fossils from Cumaná (in Wall and Sawkins), but apparently not fully identified.

In the numerous publications of R. J. L. Guppy, there are various lists or mentions of fossils from Cumaná but unfortunately it appears to be very doubtful whether the material described by Guppy as having been collected in Cumaná, really came from there or whether it may not have formed part of collections from the Bowden formation in Jamaica (see Woodring, 1928, p. 81). The publications in which Guppy mentioned fossils from "Cumaná" are listed at the end of this note (Guppy, 1866; 1866b; 1867; 1867b; 1874). Dall in his great work on the Florida mollusks (1890-1903), described two new species (Scapharca cumanensis and S. tolepia) said to occur in the "Oligocene" of Cumaná, but he also listed localitites in the Dominican Republic, so that again there is some doubt about the provenance of the species. According to Woodring, the type specimen of S. tolepia was collected in the Cercado formation of Santo Domingo, which is correlated as lower Miocene. Dall did not figure S. cumanensis. He also cited Pecten soror Gabb and Pitaria (Lamelliconcha) circenata Born as present in the Cumaná beds. The "Oligocene" of Dall was, as is well known, principally Miocene; the same holds true for the "Upper Oligocene" of Maury (1912, p. 35), who reported faunas of that age from "Cumaná, Trinidad and Jamaica".

P. I. Aguerrevere (1925) described the large pecten from Cumaná (which Karsten had mentioned as Pecten gigas, and considered as indicating a correlation between the Cumaná and Cabo Blanco beds) under the name of Pecten (Lyropecten) arnoldi Aguerrevere.

Maury (1925a) mentions some species from Cumaná, and gives a figure of Scapharca cumanensis Dall, but unfortunately, her figured specimen came from Santo Domingo. In another paper (Maury, 1925b), she refers the shell-bearing beds of Cumaná "at the coast" to the Pleistocene, but the "inland Cumaná beds, with Arca tolepia Dall and A. cumanensis Dall" are referred by her to the middle Miocene and considered correlative, with the formations of Cartagena in Colombia, the Gatún of Panamá, the Brasso of Trinidad and the Gurabo of the Dominican Republic.

K. van Winkle Palmer (1927) mentions some Cumaná occurrences of species of the Veneridae.

Woodring (1928, p. 81) gives an extensive discussion of the Guppy collections in the U. S. National Museum, which are labelled: "Cumaná". He concludes that the species indentified by Guppy as "Janina soror Gabb" is the only one which can be accepted as unquestionably collected at Cumaná. He adds that various collections of fossils in the Museum, collected from a locality east of the castle of San Antonio in Cumaná, are almost exclusively pectens, especially P. arnoldi, and that the beds are probably of Pliocene age.

Liddle (1928, p. 352-354) describes the "Cumaná beds", which he refers to the Pleistocene. The sediments are described as deltaic or marine, intercalated with continental clastic sediments, which form low hills (the Cerro de Agua Santa and the "Colines" (sic) de San Antonio), along the coast near Cumaná. There are soft ferruginous sandstones, cross-bedded, and lenticular beds of sands, gravels and boulders, up to thirty feet thick, in which are intercalated variegated clay-shales "indicating deltaic conditions". The thickness in the neighborhood of Cumaná, he says, varies from a few feet to 400 or 500 feet. Some of the beds (he continues) are highly fossiliferous and many of the shells are of large size; the majority represent recent genera. The dip is said to be in general towards the north, but he believes that this is due in part to a regional elevation of about 500 feet. These beds are said to occur from the Manzanares river on the west to Point Morro Blanco on the east, and from the Gulf of Cariaco on the north as far as the foot of the Coast Range 2 kilometers to the south, where the beds rest on the Barranquín formation. On the peninsula of Araya (Liddle states), the beds cover an area of only about 3 square kilometers, to the east (sic) of the smaller settlement of Manicuare, where they rest on schists. Similar beds, Liddle states, are found near Clarines, Morro de Unare, and Píritu, all representing the Pleistocene.

Rutsch (1934, p. 116) mentions the Cumaná fauna, giving citations of all the earlier publications. He considers the age uncertain.

Senn (1940, p. 1850) shows in a correlation table, the "Manicuare-Cubagua beds" as upper Miocene.

Liddle (1946, p. 529-531) repeats his earlier description of the "Cumaná beds", but here he refers them to the upper Miocene, which agrees with his revised correlation of the Cabo Blanco beds.

In the geologic-tectonic map of Venezuela prepared by Bucher (1950), a small area of "upper Miocene/Pliocene" (symbol Tpm) is shown in the vicinity of Cumaná, surrounded by Quaternary; in contrast with Liddle's map, the western end of the Peninsula of Araya is shown as also made up of the same formation. Bucher (1952) does not discuss these formations. The Cumaná beds do not appear either in the correlation table of Mencher et al. (1953).

Woodring (1954, p. 729) refers the "marine beds near Cumaná" to the lower Pliocene, together with the Cabo Blanco "formation".

In 1949, second-year students of the geology department of the Central University made a reconnaissance study of the Agua Santa hills, east of Cumaná and south of Caigüire, in which region the Tertiary beds of Cumaná are well exposed. These hills are about 5 kilometers long from east to west and about a kilometer and a half from north to south, contrasting sharply with the coastal salt-flats that surround them, and reaching heights up to 120 meters towards the east. The general structure is that of a syncline plunging slightly towards the west, but with numerous secondary folds in which the dips may be very steep. The thickness of the formation was estimated by the students as about 50 meters. Fossils are frequent, and indicate a correlation with the Playa Grande formation of the Cabo Blanco group (see CABO BLANCO, Group), as suggested by various authors. The collections also yield specimens of a large Arca (A. (Larkinia) grandis Broderip and Sowerby, or a related variety), which has not been found in the Cabo Blanco beds; this species apparently came from the lower part of the Cumaná beds, and probably indicates a locally brackish-water environment, which in the upper part of the beds changes to marine, where the beds contain numerous species of Pecten (especially arnoldi), Strombina, Conus, Architectonica and numerous others. Specialists who saw the collections of foraminifera from the beds were divided in opinions as to the age, whether upper Miocene or Pliocene. The ostracods were said to suggest upper Miocene. Much more thorough studies of the stratigraphy and paleontology are desirable.

In a few places, vestiges of a conglomerate, believed to represent the Pleistocene, are found lying on the Tertiary sediments.

See also CUBAGUA Formation.

Frances de Rivero

CUMANA, Series

TERTIARY? (upper Miocene?)

State of Sucre, Venezuela

Author of name: L. V. Dalton, 1912.

Original reference: L. V. Dalton, 1912, p. 42.

Original description: ibid.

Dalton (1912, p. 42) in his generalized description of the geological history of Venezuela, mentions some sandstones and fossiliferous shales that underlie the Los Llanos beds and outcrop along the coast and surround the Maracaibo Lake. He suggests the name Cumana Series for the beds, since they are very well exposed at the town of Cumaná.

The description is too vague for the indentification of the unit in the stratigraphic frame of the present nomenclature. Nevertheless, Dalton probably meant to name "Cumana Series" the same rocks named by Liddle (1928) Cumana "beds" (see).

The name is obsolete.

E. Von Der Osten

CUBAGUA, Formation

VALIDO

TERTIARY (upper Miocene and/or Pliocene)

Dependencias Federales, Venezuela

Author of name: L. V. Dalton, 1912.

Original reference: L. V. Dalton, 1912, p. 42.

Original description: none.

The "Cubagua beds" were originally named by Dalton. The type locality is the Island of Cubagua, a Federal Dependency located between the Island of Margarita and the northern coast of the State of Sucre.

2) The Navay facies, predominantly cherty-argillaceous rich in fish remains; of plant material. The Santa Bárbara facies contains, Siphogenerinoides ewoldi. The unit was correlated by Senn, 1939 (1940), ("Stratigraphical Correl-Caribbean Region" ) with beds outcropping at Manicuare, to the west end of the Araya Peninsula. In this Correlation Chart, Senn uses the name "Manicuare-Cubagua beds", under his "Eastern Venezuela" column, to designate sediments which he considers of upper Miocene age and places them stratigraphically above the Santa Inés formation. Liddle (1946, p. 531) refers to the Cumaná beds as sediments which occupy a relatively small area (3 km²) to the east of the small fishing town of Manicuare. These sediments lie in marked unconformity above the Caribbean series.

González de Juana (1947, p. 693, Table I) correlates the Cubagua formation with the Oligo-Miocene Quiamare member of the Santa Inés formation. He places the Cubagua formation below an "Araya formation" (undes-cribed) equivalent to Sacacual, and above an Oligocene? section of mottled clays, equivalent to Merecure (p. 698). González de Juana (1947, p. 699-700) mentions that "a quartzous gravel bed, exposed on the northern side of the Island of Cubagua, at the locality named Las Calderas, does probably represent the Mio-Pliocene boundary". According to this author, the over and underlying formations appear to be conformable. The writer of the present article considers it difficult to establish time boundaries based on such facts, since there are prominent lateral variations in the lithofacies.

According to the observations carried-out by the writer and F. A. Balda, the best surface section of the Cubagua formation ("beds") is exposed typically in the Las Calderas Canyon, the vertical extension of which goes from sea-level to the island top elevation. Said section, with an approximate total thickness of 70 m, is constituted by an interbedding of the following main two lithologic types: coquinoid sandstones, rich in quartz, containing abundant mollusca, and a somewhat arenaceous claystone, containing foraminifera. The basement of the formation does not appear on the surface.

An abundant microfauna, predominantly bentonic and of open marine environment, indicating a uppermost Miocene or perhaps a lower Pliocene age was identified by Sellier de Civrieux (private report) on samples from the Las Calderas Canyon.

Foraminifera: Amphistegina gibbosa, Cibicides americanus, Cribroeponides caribaea (d'Orbigny), (syn. Eponides repandus of some authors, not of Fichtel and Moll), Cibicides isidroensis, Cibicides sinistralis, Elphidium sp. cf. E. poeyanum, Siphonina pozonensis, Nonion grateloupi, Nonion sp. cf. incisum, Streblus becarii var. sobrina, Streblus becarii var. tepida, Streblus sarmientoi, Orbulina universe, Globigerina trilocularis, Globigerinoides triloba, Globigerinella aequilateris, Robulus sp. aff. R. orbicularis, Bolivina subaenariensis var. mexicana, Uvigerina - hispido costata, Uvigerina rutila ?, Cassidulina crassa.

Ostracods: Cythereis vaughani

Sellier de Civrieux says (ibid.): "the sandy and coquinoid formation exposed at Cubagua represents only the younger interval of a 4.000 meters thick Oligo-Mio - ? Pliocene subsurface section, apparantly continuous, which, according to González de Juana (1947, p. 598) comprises, downward, a silty-argillaceous greenish gray, homogenous and compact formation, containing claystone layers, and further down a mottled unit, typically continental. The upper formation of the cycle, typically arenaceous, macro and microfossiliferous (Cubagua, formation), appears to be the only part of the section to be equivalent with the beds observed to the south (Punta Araya and San Antonio at Cumaná) and east (southern part of Margarita) and which G. P. Wall (1860) referred to as a lower calcareous series of his younger Parian System. These beds overlie with marked unconformity, formations of different ages which indicates a marine overflow in the upper Miocene or/and Pliocene, from Cubagua to the areas above mentioned. (See also CUMANA, Beds)

G. Rivero N

CABO BLANCO, Group

TERTIARY (Mio-Pliocene) to QUATERNARY (Pleistocene)

Distrito Federal, Venezuela

Author of name: A. von Humboldt, 1801.

Original reference: A. von Humboldt, 1801.

Original description: A. von Humboldt.

The first allusion to the beds exposed in Cabo Blanco and its vicinity appears to have been that by Humboldt in a geologic map (Humboldt, 1801), in which the beds were referred to the "Floetzgebirge", an inclusive term then used for relatively unconsolidated formations. In 1823, Humboldt compared the formations of Cabo Blanco, Cumaná, etc., with the "calcaire grossier" of Paris (middle Eocene). Apparently the first description appears in Humboldt's famous work on his travels in the New World, the first edition of which appeared in Paris between 1814-1825. This is not available to us, but the second edition (13 volumenes, published in Paris, between 1816 and 1831; Spanish translation by L. Alvarado, 1941), we may quote:

" . . . On the west slope of the Cabo Blanco hill the gneiss is covered by a very recent formation of sandstone or agglomerate. This sandstone contains angular fragments of gneiss, quartz and calcite, magnetic sand, corals, and petrified bivalve shells. Is this formation perhaps the same age as that of Punta Araya and Cumaná?" (Humboldt, trans. Alvarado, 1941, vol. II, p. 282-283).

The next important mention appears in Karsten (1886), who in connection with the presence of geologically young sediments along the coast mentions that:

" . . . only locally is there found a marginal zone of more modern beds, for instance at Cabo Blanco near La Guaira, which is formed by Tertiary sediments of marls with shells (Pecten gigas), sands, gravels and shellbearing breccias, which together dip 45 degrees S. In addition, very recent sediments here and there covers the metamorphic crystalline schists, up to an elevation of 20 meters, for example in Punta Araya and La Guaira, evidencing a slight uplift of the coast, which must have taken place at a very recent date." (Karsten, 1896, p. 8). Karsten compares the Cabo Blanco beds with a "Tertiary... or perhaps Quaternary" limestone, which outcrops in the San Antonio hills, near Cumaná. He gives a list of species found at Cumaná, but does not list any from Cabo Blanco.

K. Martin visited Cabo Blanco prior to 1887, and collected fossils which were studied by M. M. Schepmann; a list of Schepmann's identifications appeared in Martin's publication (1887). Meantime, it appears that J. Lorié independently studied the collections and published an article (Lorié, 1887). According to Rutsch, the identifications made by Schepmann and by Lorié were considerably different. Martin referred the beds to the Pleistocene. A. Jahn (1921) quotes extensively from Martin's work. Martin distinguished in his collections two horizons, both in beds said to be flat-lying.

A Pleistocene age for the Gabo Blanco beds was accepted by Jahn (1921), Maury (1925), and Liddle (1928, p. 351), who gives a rather vague description of the beds. Rutsch (1930; 1934, p. 144-145; 1937, p. ?) and Senn (1935, p. 84) also accept the Pleistocene correlation; Senn adds that the beds are "strongly dislocated".

Aguerrevere and Zuloaga (1937, p. 21) state that "in Cabo Blanco there is a series (probably two series) of marls, clays and calcareous sands, highly fossiliferous, which have been correlated as Miocene or Pliocene" and which dip southward.

Kamen-Kaye, (1938, p. 1230), although he does not mention the Cabo Blanco beds by name, refers to "sharply upturned Quaternary molluskbearing beds, on the Caribbean coast." L. Kehrer (1939, p. 699) states that the Cabo Blanco beds are middle Miocene, on the base of studies of the mollusks and foraminifera. Kamen-Kaye (1939, p. 704) was not convinced, and Kehrer countered with a second note on the age of the Cabo Blanco beds (1939b). In this paper, Kehrer notes that a distinction should be made between the 'typical Cabo Blanco beds", which dip steeply southward, and other beds almost horizontal, which overlie the former. The former (Kehrer states), contain mollusks (identified by Woodring) and foraminifera (identified by Tash) as middle Miocene; whereas the horizontal beds, which contain the fauna described by Schepmann in Martin, represent a Quaternary marine terrace.

Liddle (1946, p. 582), following Kehrer, changed the age assignment of the Cabo Blanco beds to middle Miocene, although he stated that he himself would prefer to consider them as no older than upper Miocene, and suggested a correlation with the "Capadare horizon" (which he did not define). For the beds from which Martin collected his fossils, he proposed the name "La Guaira beds". His description of the "La Guaira beds" is identical with the description he gave in 1928 for the "Cabo Blanco beds".

Dengo (1951) was the first to publish a map of the Cabo Blanco region on a sufficiently large scale (1:50,000) to show any detail. He refers the beds, here called "Cabo Blanco group", to the Miocene-Pleiocene (following Aguerrevere and Zuloaga) and considers that there are at least three divisions represented within the group: "The lower (beds) are cross-bedded sandstones which dip 50 degrees S., above this there is another sandstone, cross-bedded and with conglomerate beds, which also dips south, but at angles around 20 degrees. In the upper part, there is a conglomerate with large boulders". (Dengo, 1951, p. 68). In the English version of his paper Dengo, (1954, p. 18) he remarks that there are least three divisions, possibly a fourth, but does not discuss them.

R. J. Smith (1952, p. 385) suggested a correlation between the Cabo Blanco beds and formations in the Tuy valley, but without details.

Bucher (1952, p. 48) accepts the interpretation of the structure of Cabo Blanco as indicated by Kehrer (1939), that is, that there is a thrust fault between the metamorphics and the Cabo Blanco beds. He adds that Kehrer now believes the beds to be upper Miocene, and that Mencher considers that at least a part is not older than the Punta Gavilán formation of Falcón, that is, Pliocene.

In the correlation table of Mencher et al. (1935), "Cabo Blanco" appears as Pliocene.

Woodring (1954, p. 729) refers the "Cabo Blanco formation", to the lower Pliocene, assigning to the same age the Cumaná beds and the Matura formation of Trinidad.

Studies in 1954 by professors and students of the Department of Geology and Mines of the Central University indicate that in the region of Cabo Blanco it is possible to distinguish three distinct formations, two certainly Tertiary, and the third possibly Quaternary. In addition, three raised beaches or marine terraces are recognizable, two Pleistocene (at elevations of 6070 and of about 20 meters respectively) and a still lower, very recent one (Holocene). (See also the article, QUATERNARY).

We believe that it is convenient to retain the term Cabo Blanco, with the rank of a group, to designate the complex of geologically young, relatively unconsolidated sediments which, in that region, contrast so notably with the metamorphic of the Caracas group. Such a group name (though it includes beds of different origin and probably of different ages) is convenient, since the "Cabo Blanco beds" or "formation", as used by different authors, may refer to one or more of these divisions, and an attempt to restrict the name to any one of them would lend itself to further confusion. For example, the references to strongly southward-dipping beds, are true only of the lowermost formation, which is not fossiliferous, and which has not so far been distinguished from the upper horizons in the literature. Again, citations of fossils may refer in some cases exclusively to the uppermost formation (for example, Martin's lists, the allusions by Senn and Rutsch), or fossils from the two upper horizons (probably so for the mentions by Kehrer and Woodring.) Karsten, Kehrer and Liddle have recognized the upper fossiliferous horizon as a distinct entity, but the name of "La Guaira beds" proposed for it by Liddle is so inexact, geographically, as well as so poorly defined, that we have thought better to suppress it. We proposed to define the Cabo Blanco group as composed of three formations (separated by unconformities), in ascending order: Las Pailas, Playa Grande and Mare. (The name "Mare" takes the place of the "La Guaira beds" of Liddle, 1946).

Las Pailas formation. -This, the lowermost formation, consists of nonmarine, unfossiliferous conglomerates and sandstones, with conspicuous crossbedding, which dip strongly to the south (around 45 degrees). Locally it contains some carbonaceous beds. In the exposures, the generally whitish color of the beds contrasts strongly with the yellowish-brown color of the Playa Grande outcrops. The name Las Pailas is proposed since the beds are well exposed on the north side of the Quebrada Las Pailas near its mouth, a little way back from the beach. The Las Pailas beds are overlain discordantly by younger beds; the base of the section and hence the lower eontaet, are not exposed, but the formation may be presumed to lie uneonformably on the metamorphies of the Caraeas group. The thickness of the exposed section is of the order of 430 meters. The Las Pailas formation outcrops only between the Las Pailas quebrada westward to the vicinity of the large quebrada east of the Playa Grande real-estate development, where the Las Pailas beds disappear beneath a steep west-dipping fold in the overlying Playa Grande formation (possibly there may also be a fault at greater depth). Due to its unfossiliferous character, the age of the Las Pailas formation could not be directly determined; obviously it is older than the Playa Grande formation below described. Possibly it' is Miocene or even Oligocene.

Playa Grande formation. -This name is proposed for the marine fossiliferous formation, sandy, calcareous and conglomeratic, which forms the upland on which the Playa Grande real-estate development is located; although the beds are not well exposed on the surface of the upland, they are well exposed in the cliffs just back of the beach and in the large gullies which limit the upland on the east side. Here the lower contact is not visible, but on the east side of the large gully just mentioned, the Playa Grande beds form the upper part of the cliffs along the coast as far as the Las Pailas quebrada, lying unconformably on the Las Pailas formation. In the region of the Las Pailas quebrada, there is a fault striking about 75 E., with the southern side downthrown, so that to the south and east of the quebrada the Las Pailas formation is not visible, and the Playa Grande is represented only by a reduced section, overlain unconformably by the third and youngest formation, the Mare formation. In the large quebrada east of Playa Grande, a section of 78 meters of the Playa Grande formation was measured. The beds are more conglomeratic towards the western part of their extent, where they contain banks of conglomerate and of fossiliferous limestone, containing Pecten arnoldi Aguerrevere and other species of pectens, Ostrea cf. O. haitensis Sowerby, and various other fossils. A considerable microfauna of foraminifers and ostracods has also been collected from these beds. The age is thought to be probably upper Miocene.

Mare formation. -This name is proposed for the youngest formation, which so far has been identified only in the small area between the Las Pailas quebrada and the next large quebrada to the east, which is just back of the small settlement called Mare Abajo. (We have called this quebrada the Quebrada Mare.) These beds are fine micaceous sands crowded with mollusk shells. They are about 10 meters thick, and terminate above in a conglomerate, which occurs at about 20 meters above sea level (the level of the Maiquetía international airport); this level corresponds to a raised beach. The most abundant species in the bed is Macrocallista maculata (Linné), followed by Oliva reticularis Lam., but species of Architectonica, Conus, Terebra, Glycymeris, Strombina, Venericardia, Trigoniocardia, Pinna and various other genera are abundant. These are evidently the beds from which Martin made his collections. The age is possibly Pleistocene, but there are various species which suggest a possibly slightly older age. The writer is at present engaged in an intensive study of the fauna.

At the extreme eastern edge of the Playa Grande upland, there is a very small exposure of marine sands, believed to date from the formation of the Pleistocene raised beach which now is found at 60-70 meters above sea level. These sands are crowded with shells of small gastropods of very recent appearance. The thickness of this bed is negligible.

Frances de Rivero