CUCHARO, Formation

TERTIARY (Oligocene to Miocene)

State of Guárico, Venezuela

Author of name: Geologists of creole Petroleum Corporation, 1938 (private reports).

Original reference: C. González de Juana, 1946, p. 31.

Original description: ibid.

Geologists of the Creole Petroleum Corporation first used the term Cucharo formation in 1938; however, González de Juana (1946, p. 31) first published and described the Cucharo formation, which derives its name from a small hill and a quebrada both known as Cucharo in the District of Infante east of the town of Socorro, State of Guárico, where the formation is well exposed. The formation is predominantly clay with a small amount of intercalated, fine to very fine-grained sand and with frequent lateral variation into argillaceous sands, mostly lenticular. Lignite is present and often associated with laminae of fine, micaceous sand. Clays are quite calcareous, almost constituting marl and include well-indurated nodules of the same clay, giving the formation the false aspect of a conglomerate, Based on fossil evidence, the age of the Cucharo formation is given as middle Miocene.

Hedberg (1950, p. 1204) includes the Cucharo formation in the Santa Inés group and states that the name has been applied by Creole Petroleum Corporation geologists to a "littoral" shallow marine to brackish facies of yellowish, cross-bedded sandstones, greenish calcareous claystones, sandy claystones and mottled claystones. Although the Cucharo formation underlies the Santa Lucía formation it is closely related to it; the boundary between them is indistinct. The Cucharo formation grades northward into the Quiamare formation of the Santa Inés group, from which it cannot clearly be separated.

(See also ZARAZA "Group").

Wm. K. MacFarquhar

ZARAZA, "Group"

TERTIARY (middle Miocene)

State of Guárico, Venezuela

Author of name: P. Christ (?) et al.

Original reference: H. G. Stehlin, 1938, p. 227.

Original description: ibid.

According to G. G. Simpson (1943, p. 55) the name Zaraza series was introduced in private reports by Christ and other geologists to designate Tertiary strata outcropping in the Zaraza region, State of Guárico. A mammalian jaw was found by P. Christ in a good outcropping area and was originally referred to as Astrapotherium christi Stehlin and later changed (Kraglievich, 1928) to Xenastrapotherium genus.

Stehlin (1928, p. 227-232) first published the name "Zaraza series" pointing-out as type-locality the Pozo Rendivú fossiliferous outcrops in the Quebrada Honda, affluent of the Tamanaco River, approximately 10 kilometers to the northeast of the town of Zaraza. The fossiliferous beds are made up of brownish concretioned sandstone. According to Stehlin (p. 231-232) the Astrapotherium indicates that the outcrops are more or less equivalent in age to those of the Santa Cruz formation of Patagonia; probably not older and perhaps slightly younger, but never post-Miocene.

H. D. Hedberg (1937, p. 2013) refers to Stehlin's "Zaraza series" indicating its equivalence with some part of the Santa Inés "formation" (today group).

In discussing the stratigraphy of the State of Guárico, M. Kamen-Kaye (1942, p. 33) mentions a Zaraza group of possible middle Miocene age which includes "strongly fossiliferous beds", but he did not refer to Stehlin's report.

New vertebrate fossils in a horizon probably almost equal to the Astrapotherium horizon were found by G. G. Simpson (1943, p. 54) who visited Stehlin's type-locality in Pozo Rendivú in 1939. The fossiliferous occurrence was described by the author as a brownish sandstone bed containing "numerous fragments of turtle shells, less frequent crocodile remains and relatively few Astrapotherium remains". he identified a turtle (Podocnemis) pertaining to the Pleurodia group, of scarce diagnostic value. Nevertheless, basing himself on the above mentioned presence of Xenastrapotherium, Simpson (p. 55) verifies Stehlin's opinion according to which the Zaraza horizon is "almost certainly, not older than Santacruzian which... (Stehlin) . . . considered lower Miocene and it is most probably younger. The Friasan is more or less lower Miocene". Simpson ends-up by assigning a middle Miocene age to the Rendivú bone horizon, saying that it might be lower or upper Miocene but it is very improbable that it would be as old as Oligocene or as young as Pliocene. According to some information received from Dr. R. Hoffstetter, the Santacruzian of Patagonia (Argentina) is considered of yower Miocene age by all modern paleontologists and geologists like Feruglio.

On the other hand, a glyptodont (Asterostemma venezolensis) was described by Simpson (1947, p. 1-10) who based himself on J. H. Todd's field information. The fossiliferous outcrop is found in the valley of the Güere River, in the near vicinity of the village of San Francisco, located to the southeast of Clarines, State of Anzoátegui. Simpson points out its probable correlation with the section exposed near Zaraza. According to the same author, the glyptodont found in the Güere River could be middle Miocene (Chasicoanian); there is the possibility that it would be much younger than middle Miocene.

It would be very interesting to determine with more precision the age of the Zaraza beds, a part of the sequence in Guárico where there are scarce faunal guides; it would be desirable to make a careful comparison between their saurian, chelonian and mammalian skeletons and those of the Urumaco bone bed, Distrito Democracia, State of Falcón, which is located almost at the top of the Urumaco formation and is of proved upper middle Miocene age, (molluscan assemblage). The material containing Xenastrapotherium in the Pozo Rendivú might perhaps be compared also with the Prepotherium level, Tucupido River, State of Portuguesa, located in the lower part of the Río Yuca formation.

The author of the present article believes it possible that the beds studied by Stehlin represent a continental facies included somewhere in the Cucharo formation, (see) considered of approximate middle Miocene age and equivalent to the Yucales formation; another lateral facies generally considered as a northern equivalent of the Cucharo formation is the lower part of the Quiamare formation (see); the Zaraza bone beds could also be compared with beds pertaining to the middle or upper part of the Chaguaramas formation (sensu lato) (see) as it was defined by Patterson and Wilson (1953). If, on the contrary, the restricted definition of the Chaguaramas formation, (proposed by Evanoff (1951) and used by the author of the present article in the redefinition of the Guarumen group (see), is accepted, the Zaraza "group" represents, or is a part of, a post-Chaguaramas unit, and therefore post-Guarumen. On the other hand, the Zaraza "group" is older than the Freites formation of the subsurface, the Punche formation of the surface, the "Aragua", Santa Lucía, Zuata, and middle and upper Quiamare formations (see). According to this, it seems rather improbable that the latter formations include Oligocene beds, as it was suggested by some geologists.

The formational nomenclature of what is considered as probable Miocene in eastern Guárico is not yet firmly established; on the other hand, the published descriptions of the type-sections are somewhat unprecise and the understanding of the stratigraphic relations between the brackish water, paludal, fluvial, deltaic and marshy formations with frequent and rapid lateral variations in the facies, present problems not yet solved. The scarcity, or lack, of fossils, increases the confusion. The disputable redefinition of the Santa Inés group, by Hedberg (1950, p. 1199-1205) suffers from those confusions. For instance, Hedberg places the Peña de Mota conglomerate above the Caño Dulce formation and below the Bruzual formation, and correlates this last one with the Roblecito formation. Today (see GUARUMEN, Group) it seems evident that the Caño Dulce formation is equivalent to the Batatal formation and that the Peña Mota facies constitutes a transgressive marginal conglomerate in the base of the Chaguaramas. Therefore, the normal sequence, from base to top, should be: Caño Dulce, Bruzual, Peña Mota. The latter represents the lowermost Miocene.

In synthesis, it is here believed that only future investigations on this complex of facies that Hedberg proposed to include in his Santa Inés group, considerably enlarged in 1950, would permit to decide the best name for the small part of the section discussed by Stehlin, which certainly does not deserve the rank of a formation and much less of a group, and the Miocene age of which, (probably middle Miocene), has been suggested by Stehlin and by Simpson.

(See also CUCHARO and CHAGUARAMAS, Formations).

J. M. Sellier de Civrieux