MIRELES, Formation

LOWER CAMBRIAN

State of Cojedes, Venezuela

Author of name: E. Rod, 1955.

Original reference: E. Rod, 1955, p. 1865.

Original description: ibid., p. 1865-7.

During a reconnaissance survey, E. Rod encountered some fossil-bearing beds in the area of the El Baúl uplift (Rod, 1955, p. 1865 etc.).

"The rock unit which consists of dark greenish gray argillites with a few interbedded quartzitic sandstones, and which in the southernmost quebrada of Cerro Mireles yielded a trilobite fauna, is here defined as the Mireles formation" (Rod, 1955, p. 1867). The formational boundaries below and above are not yet known.

The southernmost quebrada of Cerro Mireles, about 14 kms. northwest of El Baúl, State of Cojedes, was designated as type locality.

The following trilobites could be identified in greenish-gray, pinkish weathering siltstones of the Mireles formation: Olenellus thompsoni (Hall), Paedeumias sp., and ? Wanneria sp. (det. Dr. Ch. E. Decker, Oklahoma University).

Thus there is no doubt that these beds of the Mireles formation are Cambrian, probably Lower Cambrian, in age.

The so-called metamorphic rocks in the El Baúl area, composed of reddish, purplish weathering phyllites, slates, quartzitic sandstones etc., have previously been compared with the Carrizal and Hato Viejo formations of Guárico (riddle, 1946, p. 100; Bucher, 1952, p. 93; Feo-Codecido, 1955, p. 114) and were considered to represent a shallow-marine facies of the La Quinta formation (Triassic-Jurassic). On the other hand, they have also been correlated with the Paleozoic (Upper Devonian-Carboniferous) part of the Sabaneta series of the Andes.

On the Geologic-Tectonic map of the United States of Venezuela (1950), compiled by Walter H. Bucher, the El Baúl metamorphics are mapped as "basic igneous rocks" and "metamorphic rocks, in El Baúl probably Paleozoic or even younger". The Geologic Map of South America, published by The Geological Society of America (1950), indicates the metamorphic region north of El Baúl to include "Paleozoic intrusive" and "Paleozoic undivided".

Wolf Maync