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Abstract: Significance of the Pelecypod Shell Beds in the Guasare Formation, Maracaibo Basin, Venezuela

Elizabeth Hernandez, Alan Oldershaw, Federico Krause

Recent work has shown that the Guasare Formation consists of a mixed carbonate-terrigenous clastic succession dominated by nearshore deltaic processes. Pelecypod carbonate beds found in the sequence are disorganized accumulations of skeletal material. They lack a rigid biological framework and probably form aerially restricted bank-like deposits. The pelecypod beds are invariably interbedded with black mudstones forming a distinctive facies association. Environmental reconstruction indicates that such facies association resulted from fluctuations in sediment supply in a delta setting where the limestones represent chenier ridges formed during periods of reduced sediment influx.

This interpretation is supported by the recognition of specific diagenetic textures (flower spar, dissolution features, borings and mineralization) which indicate exposure to meteoric and phreatic processes in the vadose inter to supratidal settings.

The recognition that the peleypod banks represent near sea level positions in a dominantly muddy sequence is of critical importance in defining the architectural evolution of the deltaic complex.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela