GUADIMIA, Sands

See OJO DE AGUA, Formation

OJO DE AGUA, Formation

TERTIARY (predominantly upper Miocene)

State of Falcón, Venezuela

Author of name: H. G. Kugler and L. Vonderschmitt, 1925 (private report).

Original reference: A. Senn, 1940, p. 1580.

Original description: none published.

It appears that this stratigraphic unit was named by H. G. Kugler and L. Vonderschmitt in 1925 (private report), who termed it Ojo de Agua series. A. Senn and H. H. Suter in 1932 (private report) called it Ojo de Agua beds. A. Senn (1940, p. 1580) first published the name Ojo de Agua formation which overlies conformably his Agua Salada clays, zone A1c and an upper Miocene age is assigned to it.

The type locality of the Ojo de Agua formation is at Cerro Ojo de Agua de Pozón, District of Acosta, State of Falcón. The type section is a southward continuation of the Loma Luca type section of the Pozón formation (Ague Salada group) as defined by Renz (1948, p. 20). It consists predominantly of micaceous sandstones, interbedded with clays, conglomerates and sandy and knobby limestones with oysters and other mollusks. The clays contain locally abundant Streblus beccarii (Linné) and Chara seeds. The formation was deposited in a brackish to very shallow marine environment, not far from the coast.

The Ojo de Agua formation is in conformable contact with the underlying Pozón formation and the boundary is placed at the base of the first massive sandstone. However, the boundary between the Pozón and the overlying Ojo de Agua formations in the Pozón-El Mene de Acosta anticline is not a time-line as toward the west, the Ojo de Agua formation interfingers with and gradually replaces the Huso clays (Pozón formation), whereas towards the east, the Huso clays become thicker by replacing the lower Ojo de Agua sands. Thus, the Pozón-Ojo de Agua boundary is oldest in the west and gets gradually younger toward the east, and a similar change takes place toward the south of Pozón, in the direction of Riecito (Renz, 1948, p. 26). The Ojo de Agua formation is unconformably overlain by Quaternary deposits and this unconformable overlap produces a great variation in thickness of the formation, ranging from 0 to about 200 meters.

The mollusk fauna of the Ojo de Agua formation indicates a predominantly upper Miocene age for this unit.

C. Wiedenmayer (1924, p. 510) included the deposits which are now known as Ojo de Agua formation, into the obsolete Capadareserie.

The Ojo de Agua formation, south and southwest of Riecito is sometimes referred to as Guaidima sands (Mencher et al., 1951, Correlation Chart) which, however, do not overlie the Ojo de Agua formation but are probably equivalent to it.

H. H. Renz