RAMILLETE, Sands

TERTIARY (Eocene)

State of Zulia, Venezuela

Author of name: Staff of Caribbean Petroleum Co. 1948.

Original reference: Staff of Caribbean Petroleum Co. 1948, p. 588.

See CONCEPCION, Formation.

CONCEPCION, Formation

TERTIARY (Eocene)

State of Zulia, Venezuela

Author of name: Staff of Caribbean Petroleum Co., 1948.

Original reference: Staff of Caribbean Petroleum Co., 1948, p. 588.

Original description: ibid.

The Concepción formation, a name derived from the La Concepción field, Maracaibo district, state of Zulia, is a rather monotonous series of dark grey shales, dark grey micaceous, carbonaceous sandy shales, grey sandstones and some coal beds. The sandstones occur in irregular lenses and beds varying in thickness from several millimeters to several meters throughout the section. Grain size varies from very fine to coarse. Two better defined sandstone bodies are called the Punta Gorda sands and Ramillete sands after structural units of the La Concepción fields in which they are the main producing beds. The Punta Gorda sands are lower in the section than the Ramillete sands.

The Eocene perforated at La Concepción is subdivided into upper and lower Concepción formation. The division between the two is rather indeterminate and is placed arbitrarily in the shale between the Punta Gorda sands and Ramillete sands. Characteristics of the upper Concepción formation are the common presence of a foraminiferal fauna of brackish-water type composed of several Trochammina and Agathammina species, and of pebbled garnet, while etched garnets are predominant in the faunally poor lower Concepción formation. It seems probable that the Concepción formation corresponds with the lower "Micaceous sandstone" in the Bolivar district and to part of the Paso Diablo and Mostrencos formations in the Dibujo synclinorium. The Concepción formation is unconformably overlain by post-Eocene beds and underlain by the Paleocene Guasare formation. According to Fichter and Renz in Mencher et al. (1953, p. 723, fig. 10) the Concepción formation in the Mara-Maracalbo region is about 2,000 feet thick.

W. A. Mohler