CUBAGUA, Formation

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

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.