PEÑAS BLANCAS, Formación

PEÑAS BLANCAS, Horizon

TERTIARY (upper Eocene)

State of Anzoátegui, Venezuela

Synonym of TINAJITAS Formation

Author of name: W. O. Dietrich, 1924.

Original reference: W. O. Dietrich, 1924, p. 186.

Original description: ibid.

W. O. Dietrich (1924, p. 186) and R. A. Liddle (1932, p. 175) first mentioned the Pefias Blancas limestone to designate a unit of massive reef limestone which outcrops some 6 Km. to the south of Boca de Unare, Distrito Peñalver, State of Anzoátegui. This limestone was considered of Oligocene age, on account of a Lepidocyclina identified by Dietrich as L. panamensis Cushman.

Hedberg (1937, p. 2002) discussing his Merecure formation, says that: "50 kilometers west of Barcelona, between Piritu and the Río Unare, sediments believed to be the time equivalents of the Merecure formation are exposed. They include conglomerates and coals similar to those of Naricual but also in part consist of massive orbitoidal reef limestones, which are particularly well exposed on Cerro Peñas Blancas and El Picacho a few kilometers east of the river. The Peñas Blancas limestone contains Lepidocyclina trinitatis H. Douvillé, Lepidocyclina (Pliolepidina) tobleri H. Douvillé, Lepidocyclina sp. (microspheric form of L. tobleri ?), Echinolampus ovumserpentis Guppy, Rotularia sp., and an abundance of Lithothamnium sp. It may be rather definitely correlated with the Upper Eocene limestone of Vista Bella quarry in Trinidad (Mount Moriah formation) and with Bed N° 6 of Soldado Rock, and it is probably equivalent to the Upper Eocene orbitoidal limestone of Woodring from the State of Zamora, Venezuela". Hedberg adds that the Peñas Blancas limestone is probably of Bartonian rather than Ludian age.

R. A. Liddle (1946, p. 337, 357, 385-86) refers to the Peñas Blancas limestone as Peñas Blancas horizon. He mentions a thickness of 300 to 400 ft. of orbitoidal reef limestone, lying over conglomeratic sandstones and shales and interbedded with coal layers, which he considers equivalent to the Naricual beds.

Among the orbitoids, Liddle (1946, p. 385-6) mentions a Lepidocyclina pustulosa forma tobleri H. Douvillé and a L. cf. L. crassimargo Vaughan and Cole, identified by T. W. Vaughan in Peñas Blancas and La Pedrera limestones (see) which he considered as definitely upper Eocene. In the present nomenclature, the Peñas Blancas horizon is generally considered as a synonym of Tinajitas formation of the Merecure group.

R. Laforest