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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 68 (1984)

Issue: 4. (April)

First Page: 479

Last Page: 479

Title: A Shallow Water Eocene Turbidite Sequence From Venezuelan Andes: ABSTRACT

Author(s): Santosh Kumar Ghosh


Part of the Eocene sequence in Trujillo State, overlying the sublittoral marine Valle Hondo Formation, reveals a turbiditic mode of origin in a prodeltaic setting. The exposed basal fining- and coarsening-upward cycle implies a gradual abandonment phase and a subsequent progradational pulse of a suprafan channel respectively. The upper unit, in a separate exposure, is a thick coarsening-upward sequence of deltaic progradation origin.

The fining-upward (and thinning-upward) sequence, resting on a prodeltaic shale, consists of: (a) basal stacked conglomeratic arenites (supra-fan channel) with graded beds, imbricate clasts and transported shells; (b) a sandy/shale unit (channel margin/inter-channel) with flame structure, lenticular bedding, infrequent Tb-d sequence, rippled flats, and rare Planolites; and (c) a dark shale (prodelta-platform) with scarce Chondrite and Sclarituba (?) traces. The overlying coarsening-upward sequence consists of thickening-upward sandy/shaly facies and lenticular stacked pebbly arenites.

The upper unit is a typical deltaic progradational sequence with a basal prodelta shale with Tb-d and Tb-e sequences in thin intercalated sandstones; a delta-front heterolithic facies with flute and groove casts, Planolites/Thalassinoides; and a thick cross-stratified coastal marine sandstone.

Considerations such as maturity of the turbiditic arenite, its inferred proximity to the paleoshoreline, and facies relationship with the Valle Hondo deposits suggest deposition at the toe of delta-front slopes and seaward. It is likely that this flyschoid sequence may be part of a mixed-type fan as it merges northward and basinward into the deep-sea fan sequence of the coeval Trujillo Formation.

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