LOS JABILLOS, Formation

TERTIARY (upper Eocene)

State of Anzoátegui, Venezuela

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

Original reference: H. D. Hedberg and A. Pyre, 1944.

Original description: ibid. The name Los Jabillos sandstone was given by Hedberg and Pyre (1944, p. 15-17) to designate the basal portion of the Merecure formation on Río Querecual and Cerro Los Jabillos immediately east of the river. Here, the unit consists dominantly of pinkish-gray thick-bedded, medium to coarse-grained (and even pebbly) quartzitic sandstones about 600 feet thick. This resistant and topographically prominent sandstone extends across most of northeastern Anzoátegui and forms a very useful mappable lithostratigraphic unit. It is well developed in the ríos Areo, Amana, Orégano, Aragua, Teresín, Querecual and Capiricual, but westward in the vicinity of Naricual it divides into several sandstones separated by shales and in the Barcelona area grades into the Tinajitas member. In many of the river sections, the Los Jabillos sandstone interfingers with shaly fossiliferous intervals which are suggestive of Tinajitas facies.

Hedberg (1950, p. 1196-1197) raised the Merecure formation to the rank of group and its Tinajitas, Los Jabillos and Naricual members to formations. Although the stratigraphic relation between the Los Jabillos formation and the underlying Santa Anita group is not very clear, some geologists (Hedberg and Pyre, 1944, p. 17; Hedberg, 1950, p. 1195) consider that the contact appears to be transitional, especially in the ríos Aragua and Orégano. In this connection, Hedberg states that in the foothills of the Serranía del Interior from Río Querecual to Río Guarapiche, there was probably no break in deposition between the Merecure and Santa Anita groups, such as exists to the west and must be present farther south. However, another group of geologists are of the opinion that the Santa Anita-Merecure contact is characterized by an unconformity, with an intervening hiatus in deposition covering most of the lower and middle Eocene.

The interfingering character of the Los Jabillos formation with the upper Eocene Tinajitas formation suggests an upper Eocene age for the barren Los Jabillos formation (Hedberg and Pyre, 1944, p. 18-19).

Gustavo Feo-Codecido