Structural and Stratigraphic Correlations Across the Burro Negro Fault Zone, Northeastern Margin of the Maracaibo Supergiant Basin

David Contreras¹, Paul Mann¹, Alejandro Escalona², and Miguel Nunez^3
1Institute for Geophysics, University of Texas at Austin, Austin, TX
²University of Stavanger, Stavanger, Norway
³PDVSA Exploracion, Puerto La Cruz, Venezuela

The northwest-striking Burro Negro fault zone (BNFZ) can be traced as a surficial, linear, 0.5-1.0 km-wide fault zone for a distance of 100 km across western Venezuela. The BNFZ separates high-quality, Eocene fluvial and deltaic sandstone of the supergiant Maracaibo basin to the southwest from a poorly studied, belt of intensively deformed, deeper water, and shalier rocks to the northeast. Unlike the mature Maracaibo basin, the northeastern area is a frontier basin that is currently being explored. Previous interpretations for the Eocene motion on the BNFZ vary from a right-lateral, strike-slip fault with 100 km of offset; to a normal fault downthrown to the northeast and thrust fault downthrown to the southwest. We integrate 1350 km of 2D seismic data, 26 wells, and gravity data from both sides of the BNFZ to constrain the type of motion on the BNFZ and to improve stratigraphic correlations between the Maracaibo basin and the frontier basin to the northeast. On serial seismic lines crossing the fault, the BNFZ forms a wide zone of chaotic reflectors that can be traced to depths of 3-4 seconds TWT. The narrow BNFZ forms a major boundary in structural style from Eocene transtension in the Maracaibo Eocene platform to Eocene and early Oligocene folding and thrusting in the northeastern area. Folding and thrusting in the northeastern area occurs on different, sub-horizontal detachment layers and are accompanied by growth faulting and shale diapirism. Hydrocarbon plays associated with the shale-involved fold-thrust belt include slope channels and deep water fans derived from the Eocene proto-Maracaibo shelf edge delta system to the southwest. A proposed modern analog to this area is the shale-involved deformed zone in the Orinoco delta of eastern Venezuela and Trinidad.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas