GUACHARACA, Sand

See GUACHARACA, Formation

GUACHARACA, Formation

TERTIARY (upper Eocene to Oligocene)

State Falcón, Venezuela

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

Original reference: H. H. Suter, 1947, p. 2195, 2196.

Original description: ibid.

The formation was named by H. H. Suter and H. H. Renz in 1945 (private report) and first described by H. H. Suter (1947, p. 2195, 2196) who states that the Guacharaca formation overlies unconformably the upper Eocene Cerro Misión and is of Eocene to Oligocene age. The formation consists of an upper zone of sands, also termed the Guayaval, Guacharaca or La Danta sands, and a lower zone of dark gray shales; the transition shale to sand is gradual. "...The sands are rather impure, fairly well consolidated and commonly glauconitic. Lenticularity is not excessive but individual layers are thin (5-20 feet). Overlying these with a gradual transitional contact are the El Salto sands of the Oligocene San Lorenzo formation".

H. H. Renz (1948, p. 8, 11) indicates that the type locality of the Guacharaca formation, although incompletely exposed, lies in the south flank of the Guacharaca uplift, about 10 kilometers north-northwest of the Pozón trigonometric station, District of Acosta, Eastern Falcón. Here, the lower part of the formation contains orbitoidal limestone lenticles of the Cerro Campana limestone type. In the El Mene de Acosta wells nos. 7 (2734-3463') and 47 (1140-1960') the Guacharaca formation was completely penetrated showing a stratigraphic thickness of about 235-250 meters and consisting of a sequence of calcareous and noncalcareous shales and silty shales with occasional sandstone layers in the upper part. The contact with the underlying Cerro Misión formation and overlying El Salto sand member of the San Lorenzo formation (Agua Salada group) appears to be transitional. Renz (1948, p. 30, 38) lists some foraminifera occuring in the Guacharaca formation at El Mene de Acosta and comes to the conclusion that the age is predominantly lower Oligocene (Vicksburg). In the Guacharaca area, however, the Eocene-Oligocene boundary lies within the lower part of the Guacharaca formation.

The Guacharaca formation is partly synonymous with the now obsolete Guayaval serie of Wiedenmayer (1924, p. 510) and also with the lower part of Senn's El Mene-Sand formation (1935, p. 77) which is also an invalid name. The Cerro Campana-Schichten of Senn (1935, p. 68) are also considered largely synonymous with the Guacharaca formation.

Local lithological facies variations within the Guacharaca formation have been described under various stratigraphic names such as the Cerro Campana limestone (Wiedenmayer, 1924, p. 511; Senn, 1935, p. 68; Liddle, 1946, p. 299, 370, 381), the Guayaval marls (Senn, 1935, p. 69; Liddle, 1946, p. 372), the Tacamire shales (Senn, 1935, p. 69) in the lower part of the formation and the Tacamire sandstone (Senn, 1940, p. 1580; Liddle, 1946, p. 373), the Guayaval sands and La Danta sands (Suter, 1947, p. 2195) in the upper part of the Guacharaca formation.

H. H. Renz