EL MENE, Formation

TERTIARY (middle to upper Eocene)

State of Zulia, Venezuela

Author of name: H. D. Hedberg, 1927 (private report).

Original reference: H. D. Hedberg and L. C. Sass, 1937, p. 93.

Original description: none published.

Originally applied by Hedberg in 1927 (private report) to the formation exposed along the shore of Lake Maracaibo north of El Mene de Ambrosio, District of Bolívar, the name was readily adopted for the Eocene sediments underlying the Ambrosio formation and the pre-Oligocene unconformity surface in the subsurface of the northern Bolívar Coastal Fields. The name El Mene was in general usage after 1928 but was not introduced into print until Hedberg and Sass (1937, p. 93) mentioned the correlation and equivalence to the Mostrencos formation of Mara. Douglas (1938, facing p. 102) on a cross-section of the Bolivar Coastal Fields, showed the stratigraphic position of the El Mene under the unconformity and the relationship to the Paují formation. Sutton (1946, p. 1681-1682) again referred to the El Mene formation as the equivalent of the combined Las Flores and Potreritos formations.

Hedberg (1938, p. 272) declared that the name was undesirable because it has been used for three other distinct formations; however, since that time the other uses of the name have been discarded and replaced, leaving the name expurgated for publication.

Following the work of Hedberg (1931, private report) and G. E. Manger (1940, private report), the El Mene formation was divided into an upper and lower member: the lower member is composed almost entirely of dark gray, carbonaceous, hard shale with occasional gray, hard, thin-bedded, calcareous sandstone. Foraminifera are rare, and usually belong to the genera of Haplophragwaides, Ammobaculites and Trochammina. Heavy mineral determinations are characterized by the absence of staurolite. Thickness varies from 2500 to 3000 feet. The upper member is predominantly a sandstone section, composed of medium-hard, thick to thin-bedded, greenish-gray and brownish-gray sandstones, and interlaminated greenish-gray sandstone and brownish-gray shale. Shaly portions are fossiliferous and glauconitic. The sandstones and shales of the basal 1000 feet are harder than those above, which are characterized by being softer, friable, the light brown color, and an increase in carbonaceous material. Foraminifera are common, the most common being Haplophragmoides, Ammobaculites, Trochammina, Anomalina; a few species of those similar to forms of the Ambrosio formation are found in the uppermost El Mene. Heavy minerals are characterized by the presence of staurolite. The thickness of the upper member varies from zero to over 3000 feet, depending upon the amount of truncation by the unconformity surface. The well-known B-6-72 sand (Mencher et al., 1951, p. 47) occurs about 1200 feet above the base of this member.

The outcrop areas of the El Mene formation are limited to scattered outcrops north of El Mene de Ambrosio, the Curazeo anticline and the La Pava anticline (East Lagunillas uplift). In the subsurface, it is distributed under Lake Maracaibo, through the District of Bolívar and parts of the Districts of Urdaneta, Maracaibo and Mara.

The El Mene formation conformably overlies the Misoa formation and is overlain, with a vertical and lateral gradational contact, by the Ambrosio formation. Toward the south, the formation grades laterally into the Paují and Río Caús formations; toward the east, the upper part grades laterally into the Paují; and toward the west, it is equivalent to the Mostrencos and the lower part of the Orumo formation.

Gordon A. Young