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Abstract: Tecto-Sedimentary Setting of the Upper Misoa-B Sandstone East of the Maracaibo Lake (Eocene, Western Venezuela)

H. Eichenseer, J. M. Ugolini, J. F. Ballard

Outcrop and subsurface data permit to redefine the depositional setting of the Upper Misoa-B sandstone to some extent. Regional sedimentologic analyses suggest the following evolution of the Misoa Sedimentary System:

-- Single estuarine channel sequences and/or complex tide-dominated incised valley fills are dominating to the Southeast. Tidal sand shoals and channels cover the littoral to inner-shelf zones in the central part. Storm-reworking of tidal sandsheets increases toward the North, in the inner-shelf domain of the Misoa System. Outer-shelf to basinal zones predominate northward. These zones are characterized by a change from distal storm sands to thin-bedded turbidites.

Sequence stratigraphic analyses document the following:

-- High-frequency sedimentary cycles of the Upper Misoa sandstone are highly asymmetric, with extremely thick transgressive facies tracts. Highstand intervals are rarely preserved, because of strong erosion at the level of the sequence boundaries. It is the southward propagating down-flexure of the Mid-Eocene Caribbean Foreland Basin which leads to incremental backstep of the Misoa-B sequences and the overall transgressive nature of the sedimentary facies.

This basin behaviour, in combination with the moderate sediment supply hampered the evolution of a true progradational delta.

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