CORO, Conglomerate

TERTIARY (Pliocene)

State Falcón, Venezuela

Author of name: R. Arnold, 1911 (private report).

Original reference: R. A. Liddle, 1928, p. 346-348.

Original description: ibid.

Liddle (1928, p. 346-348) stated that the Coro conglomerate receives its name from Río Coro, where it is typically exposed, especially to the north of the old Spanish irrigation dam. Liddle described the unit as composed of highly conglomeratic, cross-bedded sandstone, which on freshly exposed surfaces has a speckled appearance from black and white quartz pebbles in a brown, sandy matrix. It varies from fine, sandy conglomerate to coarse conglomerate containing quartz pebbles two centimeters in diameter. Liddle stated that the thickness of the Coro conglomerate varies from a few inches to 600 feet, the greatest amount having been measured at the type locality. According to Liddle the conglomerate lies with distinct unconformity on the La Vela and Caujarao formations at the type locality. The Coro conglomerate was given a probable Pleistocene age by Liddle.

González de Juana (1937, p. 191) mentioned that Pliocene sediments crop out south of La Vela de Coro and in the north flank of the La Vela anticline in north-central Falcón and that these beds are equivalent to the Coro conglomerate. He described these sediments as composed of yellow sandy clay, with interbedded coarse-grained, conglomeratic sandstones and fine to coarse conglomerates made out of iron coated pebbles, chiefly quartz and chert, in a yellow cement. González de Juana pointed out that on the north flank of the Cumarebo anticline, in north-eastern Falcón, the Plio-Miocene contact is marked by terrestrial conglomerates, similar to the Coro conglomerates. In higher horizons there are also conglomerates interbedded with impure sands, and clays with marine shells, chiefly Pecten and Ostrea. González de Juana cited a maximum thickness of 500 meters for the Coro conglomerates.

Liddle (1946, p. 539-540) stated that the age of the Coro conglomerate is probably Pliocene. On his correlation chart he showed the Coro conglomerate unconformably overlying the El Veral formation in his column for western Falcón, and unconformably overlying the "Upper Codore" in his column for central Falcón.

The "terrestrial conglomerates" (actually marine conglomerates) mentioned by González de Juana (1937, p. 191) on the north flank of the Cumarebo anticline represent the basal conglomerate of the Tucupido formation of Payne (1951, p. 1861). The "Coro conglomerate" of Liddle (1928, p. 346-348) González de Juana (1937, p. 191) and Liddle (1946, p. 539-540) is synonymous with the San Gregorio formation of enlarged usage, i. e., including the Río Seco as its upper member.

Leo Weingeist