EL MILAGRO Formation

TERTIARY (Pliocene) - QUATERNARY (Pleistocene)

State of Zulia, Venezuela

Author of name: R. A. Liddle, 1928.

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

Original description: ibid.

The name El Milagro beds was published first by Liddle (1928, p. 348) and is derived from a parish of the city of Maracaibo called El Milagro, where the formation is exposed in cliffs along the lake of Maracaibo, state of Zulia. Hedberg and Sass (1937, p. 107) changed the name into El Milagro formation.

Sutton (1946, p. 1711) gives the following description of the El Milagro formation: in its upper part the formation comprises light yellow-brown, fine-to medium-grained, micaceous sands and friable sandstones; light gray silts, and light brownish gray, coarse-grained, micaceous, friable sandstones. Some thin layers of dark brown ferruginous sand and buff claystones are present. Thin layers of hard clay ironstone locally provide sufficient resistance to erosion to permit the development of cliffs. The lower part of the formation is dominated by light greenish gray, fine - to coarse - grained and gritty, micaceous, friable sandstones, shaly sandstones, and siltstones. The latter contain locally some light yellow calcareous seams.

The type of sedimentation denotes shallow fresh-water deposition at a considerable distance from the source area.

The El Milagro formation varies in thickness from 0 to 150 meters.

The El Milagro lies unconformably on all older formations, and is covered only by recent alluvium.

The formation is restricted to the northern part of the Maracaibo basin. It has not been reported south of the La Rosa district of the Bolívar Coastal field on the east side of the lake. It is probably present for a considerable distance north, west, and southwest of the type area at Maracaibo.

The true age of the El Milagro is not definitely known but is probably Pleistocene. No fossils are present except silicified wood, which is very common at the base of the formation.

The El Milagro is equivalent to the Carvajal formation of the Mérida Andes region and the Mesa formation of eastern Venezuela. An obsolete synonym for the El Milagro is the Maracaibo formation of Garner.

According to Hedberg and Sass (1937, p. 108) and González de Juana (1952, p. 328) the thickness of the El Milagro formation may be as much as 100 meters. The formation grades vertically and laterally into the underlying Onia formation, with an interfingering of the sediments of these two formations (Manger, 1938, p. 77-78).

W. A. Mohler