BRUZUAL, Claystone

TERTIARY (Oligocene)

States of Anzoátegui and Guárico, Venezuela

Author of name: A. Birketvedt, 1943 (private report).

Original reference: H. D. Hedberg, 1950, p. 1203.

Original description: ibid.

A. Birketvedt (1943, private report) named the Bruzual beds for a series massive mottled claystones, with ocassional thin beds, to pockets, of gravel or soft conglomerate, outcropping some 10 kilometers north of Clarines (San Antonio anticline).

H. D. Hedberg (1950, p. 1203) was the first to desbribe in publication the Bruzual claystone, forming part of the Santa Inés group. Its name is derived from the Districts of Bruzual, State of Anzoátegui, where it is typically developed. Geographically, the formation extends wesward some 130 kilometers along the south flank of the Serranía del Interior, from the vicinity of Río Unare to Altagracia de Orituco. Its outcrops are characterized by a low, nearly featureless relief with bad-land topography.

Lithologically, the formation, consists of a sequence of red, brown, purple, greenish and gray mottled claystones, weathering to a tan color with bands of red. Ocassionally it contains some beds of friable, gravelly conglomerates and thin gray to purple, fine-grained to coarse grained sandstones. The top and the base of the Bruzual claystone are not as yet defined; howerer, its thickness is estimated at some 5000 feet. The formation, which is predominantly a fresh to brackish-water deposit, contains only a few brackish-water foraminifera, such as Streblus beccarii (Linné), Milliammina fusca (Brady), Ammobaculites sp. The Bruzual claystone appers to be a lateral equivalent to some part Capiricual formation and to the Carapita formation further east.

José Luis Padrón