EHRLICH, ROBERT N., and E. P. MOLDOVANYI, Amoco Production, Houston, TX; and A. J. NEDERBRAGT, Free University, Amsterdam, Netherlands

ABSTRACT: Drowning of the Late Albian Maraca Formation Carbonate Platform, Maracaibo Basin, Venezuela

Outcrop, core, and electric log data indicate that the shallow-water Maraca Formation carbonate platform of the Maracaibo Basin was rapidly drowned at the end of the Albian-earliest Cenomanian. No evidence of subaerial exposure is present at the platform's seaward end. This study shows that these high-energy, shallow-water carbonates grade abruptly, but conformably into low-energy, middle to outer shelf planktonic foram-dominated lime mudstones.

The mudstones are in turn gradationally and conformably overlain by the organic carbon-rich La Luna Formation (earliest Cenomanian-latest Santonian) outer shelf to upper slope planktonic foram limestones. The Tres Esquinas Member (latest Santonian), previously considered the basal part of the Colon Formation, is re-interpreted as uppermost La Luna, based on biostratigraphy and facies relationships. The unit consists of a 3-5m thick chert with interbedded fossiliferous phosphate-glauconite hardgrounds, interpreted as having been deposited as storm-generated shelf turbidites.

Deep-water sedimentation patterns in the basin changed during the Campanian. The Socuy Member (Colon Formation), deposited in a well-oxygenated middle to outer shelf environment, consists of a basal limy and glauconitic chert (originally considered the Tres Esquinas Member, Colon Formation), and an upper foraminiferal limestone. The 40 m thick Socuy spans the entire Campanian, and represents a prolonged episode of slow sedimentation beyond the distal end of the active, northward-prograding Colon delta.

The Maraca platform was one of many carbonate platforms of the Gulf and Caribbean region drowned during the early Albian through late Cenomanian. The diachroneity of these drowning events can be explained by local modulations of climate, oceanography, and tectonics.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.