HUSITO, Marly Clay Member

TERTIARY (upper Oligocene to lower Miocene)

State of Falcón, Venezuela

Author of name: H. H. Renz, 1945 (private report).

Original reference: H. H. Suter, 1947, p. 2195.

See: POZON, Formation.

POZON, Formation

TERTIARY (upper Oligocene to middle Miocene)

State of Falcón, Venezuela

Author of name: H. H.. Renz, 1945 (private report).

Original reference: H. H. Suter, 1947, p. 2195.

Original description: H. H. Renz, 1948, p. 19-27.

Although mentioned for the first time in publication by H. H. Suter (1947, p. 2195), the Pozón formation was named by H. A. Renz in 1945 (private report) who described it (1948, p. 19-27) as part of the Agua Salada group. The formation is named from the area of Pozón, District of Acosta in eastern Falcón, and the type section lies between the Policarpio trigonometric station and the Cerro Ojo de Agua, running north-south along the watershed ridge of Loma Luca, between sidebranches of the Quebrada Agua Salada in the west and Quebrada Araguata in the east. Structurally, it lies on the south flank of the east-striking Pozón anticline. In the Pozón type section and all along the Pozón-El Mene anticline over a distance of 60 kilometers, the Pozón formation overlies the San Lorenzo formation disconformably or with a slight angular unconformity (0-7° in dip and 0-5° in strike). Toward the coastal regions in the north, the San Lorenzo and Pozón formations are in accordant and conformable contact. The top of the formation is in conformable stratigraphic contact with the overlying Ojo de Agua formation. The Pozón formation is present over the greater part of the Agua Salada basin. Paleontologic evidence suggests that the age of the Pozón formation extends from the upper Oligocene (Aquitanian) to the middle Miocene (Tortonian), covered by the upper Acostian stage (upper part of the Siphogenerina transversa zone), the Araguatian stage and the Lucian stage.

The lowest litho-stratigraphic unit of the Pozón formation is the Policarpio greensand member, which receives its name from the Policarpio trigonometric station near the north end of the Pozón type section. It overlies the San Lorenzo formation with a very slight angular unconformity, and can be followed for more than 60 kilometers. The Policarpio greensand member is about 10 meters thick and consists in its lower part of about 6 meters of irregularly indurated badly bedded fossiliferous clay, marly clay and greensand, interspersed with red glauconitic ironstone and white marlstone concretions, followed by about 4 meters of brown-weathering calcareous and gypsiferous greensand with yellow marlstone concretions.

Conformably overlying the Policarpio greensand member follows the Husito marly clay member which is named from Husito, a locality near the junction of the east and west branches of the Quebrada Agua Salada. In the type area it consists of 536 meters of yellow-brown, weathering, gray-brown to chocolate-brown marly clays with numerous intercalations of foraminiferal marls, which become more frequent towards the top. A horizon of white-yellow marlstone concretions occurs in the lower third of this member. Scattered grains of glauconite occur in the marly clays and the associated gray-brown clays. The soils are khaki-brown in the marly clays and bright yellow in the foraminiferal marls.

The Huso clay member is the highest lithological unit of the Pozón formation, overlies the Husito marly clay member conformably and transitionally, and is in conformable contact with the overlying Ojo de Agua formation. The member is named from a locality called Huso, west of the Pozón type section. It consists of 496 meters of red weathering, gray, noncalcareous, well jointed clays with intercalations of yellow-weathering, browngray marls and marly clays. Some individual marl beds are as much as 20 meters thick. Toward the top, there are sometimes thin lenses of finegrained, yellow-brown calcareous sand; grains of glauconite are rare. In the Pozón type section, the top of this member (top of the Pozón formation) is placed at the base of the first massive sandstone which forms the base of the Ojo de Agua formation.

H. H. Renz