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MARAIS-GILCHRIST, GIL, and ROGER HIGGS, Maraven S.A., Caracas, Venezuela

ABSTRACT: Sequence Stratigraphy of the Misoa Formation (Eocene) Lake Maracaibo, Venezuela

A preliminary sequence analysis of the Misoa Formation has been done in the Maraven concession area, Lake Maracaibo, using well logs supported by palynoloiigcal and seismic data.

The Misoa Formation is interpreted to comprise a lower transgressive unit containing at least four third-order cycles (lithostratigrpahic units C7 to C3, approximately), and an upper dominantly regressive unit consisting of six third-order cycles (approximately C2 to B1). A major flooding surface (gamma-ray log maximum) provides a marker near the top of the lower unit, almost coincident with the improtnat N-M local pollen zone.

A tentative correlation can be achieved with the Haq-Vail coastal onlap curves for the Tejas A 2.3 to 3.3 third-order cycles, 55 to 44 ma. The maximum flooding surface would correlate with the maximum Eocene onlap at 52.5 ma. These ages broadly agree with the local pollen zonation. Incised valley fill units interpreted on the basis of blocky log character in some wells could have accumulated during global Eocene sea level falls, particularly those between 55 and 54 ma.

The sequences gradually onlap onto the Paleocene unconformity, and converge in a sothwestward (landward) direction, although north-south-oriented high-angle sinusoidal events are evident on some seismic lines. These are thought to indicate rotated listric fault-bounded blocks formed during an extensional episode, possibly syn-Misoa.

The study should aid exploration for stratigraphic traps in the lake area.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.