GYROIDINA-BULIMINA, Zone

UPPER CRETACEOUS

State of Anzoátegui, Venezuela

Author of name: H. D. Hedberg and A. Pyre, 1944.

Original reference: H. D. Hedberg and A. Pyre, 1944, p. 13-14.

See VIDOÑO, Formation

VIDOÑO, Formation

UPPER CRETACEOUS to ?TERTIRY (Paleocene? )

State of Anzoátegui, Venezuela

Author of name: H. D. Hedberg and A. Pyre, 1944.

Original reference: H. D. Hedberg and A. Pyre, 1944, p. 12-15.

Original description: ibid.

The Vidoño shale, the middle member of the Santa Anita formation, was named by Hedberg and Pyre (1944, p. 12-14) after the village of Vidoño, 6 kilometers east of Barcelona. A good reference section is exposed in Río Querecual where the unit includes the interval from the top of the underlying San Juan sandstone, at the Paso Santa Anita, to the base of the overlying Caratas member, at about 300 meters downstream. Here, it is about 900 feet thick and is composed largely of dark foraminiferal shale with minor beds of sandstone and calcareous siltstone, all of which are commonly very glauconitic. The unit is in conformable stratigraphic contact with both the underlying and the overlying members.

According to Hedberg and Pyre (1944, p. 12-14), westward in the vicinity of Barcelona, the Vidoño shale thickens at the expense of the San Juan and Caratas members. It forms the Vidoño valley and is well exposed on the Puerto La Cruz-Oficina highway on the crest and south slope of Cerro Pele el Ojo. It also crops out in the vicinity of Puerto La Cruz and on the La Borracha Island. East of Río Querecual, the member gets thinner and grades into sandstones and siltstones of the San Juan and Caratas members.

The Vidoño shale contains a rich foraminiferal fauna which has been provisionally divided into the following faunizones, given from base to top: (1) "Gümbelina-Siphogenerinoides zone"; (2) "Gyroidina-Bulimina zone"; (3) "Rzehakina-Spiroplectammina zone"; (4) "Dorothia-Cyclammina zone". The foraminiferal fauna of the Vidoño shale was described by Cushman (1947). On the basis of the paleontologic evidence (Hedberg and Pyre, 1944, p. 14-15; Cushman, 1947), the lower part of the Vidoño shale is approximately of Upper Senonian age, whereas its upper part carries a fauna of Cretaceous aspect, but lacking in species definitely known to be limited to the Cretaceous; in this connection, and due to the transitional character of the Vidoño shale into the overlying Caratas member, its upper part may be as young as Paleocene.

The term Vidoño was originally used as a member of the Santa Anita formation; later, the Santa Anita formation was raised to group rank (riddle, 1946, p. 280) and its respective members (San Juan, sandstone, Vidoño shale and Caratas member) to formation rank (Hedberg, 1950, p. 1193).

The Vidofio formation and its lateral variations have a very wide geographic distribution along the south foot of the Serranía del Interior and can be followed from the State of Monagas in the east to the State of Portuguesa in the west, for a distance of about 750 kilometers. In the west it grades laterally into the Colón formation

Gustavo Feo-Codecido