MOSQUITO, Formation

TERTIARY (upper Oligocene or lower Miocene)

State of Falcón, Venezuela

Author of name: A. L. Payne, 1951.

Original reference: A. L. Payne, 1951, p. 1854.

Original description: ibid.

Payne (1951, p. 1854, 1857, 1859) wrote: "Mosquito formation (new name). This lower Miocene-upper Oligocene formation, called the Socorro formation in company reports and also by González de Juana, attains its greatest thickness in the area, about 3,300 feet, in the type section along the Quebrada El Mosquito, about 5 miles southwest of Cumarebo field. In that area the formation consists of clays and shales with some micro-and macrofossiliferous marry layers, and there the Dividive limestone member, a thin (0—30 feet) reef limestone marks the top of the formation. The reef dies out eastward. Farther toward the east, near Pueblo San Francisco, 5 kilometers (3 miles) southeast of Cumarebo field, the uppermost 300 feet of the formation consist of the soft, fine-grained San Francisco sand, which carries plant remains. The sand disappears westward and does not crop out at the same localities as the limestone, . . . ".

"Sand 15, the thickest and most prolific reservoir in Cumarebo field, . . . is, in whole or in part, the subsurface representative of the San Francisco sand. It is typically about 570 feet thick and has a hard dense calcareous cap with Operculinoides, this cap being regarded as the stratigraphic equivalent of the Dividive limestone and marking the top of the formation."

Most geologists now consider the Mosquito as the lowermost member of the Socorro formation (see) and place the San Francisco sand and the Dividive limestone as members in the middle of the Socorro formation in the Cumarebo region.

Leo Weingeist