GLOBOTRUNCANA APPENNINICA, Zone

CRETACEOUS (Cenomanian)

State of Anzoátegui, Venezuela

Author of name: W. Maync, 1952 (private report)

Original reference: E. Rod and W. Maync, 1954, p. 277 etc.

See BOQUERON, Formation

BOQUERON, Formation

CRETACEOUS (Cenomanian)

State of Monagas, Venezuela

Author of name: E. Rod, 1952, (private report).

Original reference: E. Rod and W. Maync, 1954, p. 228, etc.

Original description: ibid.

H. D. Hedberg and A. Pyre reconognized a zone of transition between the greensands of the upper Chimana formation and the Upper Cretaceous Querecual formation. This 50 feet thick zone is composed of gray yellowish weathering, fissile shale and sandy shale with hard sandy calcareous lenses (Hedberg and Pyre, 1944, p. 9). H. D. Hedberg called it "Transition Shale Zone" (Hedberg, 1950, p. 1189): E. Rod (1952) raised it to formation rank and proposed the name Boquerón formation (Rod y Maync, 1954, p. 251). Boquerón, near the village of Periquito on the San Francisco-Caripe highway, Monagas, was chosen as type locality; the best exposed section is displayed at the west end of Chimana Grande Island, Anzoátegui.

The Boquerón formation consists of gray laminated, sandy or marly fossiliferous limestones, sandy shales and purplish silty Globigerina marls. On Chimana Grande Island, a thickness of 40 to 95 meters measured. At the type locality, Boquerón, the formation attains 40 meters in thickness, Locally, the Boquerón formation may be very reduced or is competely missing (truncation of folds before the ingression of the Querecual sea). At such places, the contact is, accordingly, an unconformity. Fauna and age: Mariella bergeri (Brogn.), fornd in the lower Boquerón formation, is indicative of a Vraconian-lower Cenomanian age. Globotruncana (Ratalipora) appenninica Renz, occuring near the top of the formation, viz. about 10 meters below the base of the Querecual formation, proves a Cenomanian age.

This bioestratigraphic term, Globotruncana appenninica zone, was introduced in 1954 (Rod and Maync, p. 279).

Wolf Maync