Brooks Range of Alaska and East-Venezuelan Cordillera: Comparative Petroleum Geology

By

D.H. Roeder (Murnau Geodynamics Inc.), C.G. Mull (Alaska Division of Oil and Gas), M. Morales, and E. Hung (PDVSA Guaraguao)

The Brooks Range and east-Venezuelan segments of the Cordillera both contain fold-thrust belts of mid-Tertiary completion age, and both contain piggybacking terranes that record earlier obduction of ophiolite and exotic shards. Both involve marine passive-margin series (2 and 5 km thick) and foredeep fill (12 and 6 km thick), and both enjoy the incentive of aging world-class petroleum reserves nearby. Both areas, however, must face deep-basin uncertainties, depth limits to drilling, and environmental restrictions. A comparison of two sets of seriated structure cross sections (Brooks Range set planned, Venezuela set presented) will contribute to strategic clarity for both belts. In both fold-thrust belts, the key objectives, known or unknown, are located near the mountain front. They consist of late structural traps in subthrust position beneath piggybacked tectonic surface units, and involve hydrocarbon systems of the passive margin and/or the foredeep fill. In the east-Venezuela belt, deep mountain-front antiforms are clearly outlined and perhaps detached at the basement top (-14 to -18 km), but there is no known reservoir in the passive-margin series. In the Brooks Range, a series of upper-crustal antiforms suggests thick-skinned compressional bulk strain of at least 45 km, detachment at the brittle-ductile interface, and emplacement onto the foreland crust (-14 to -16 km).

AAPG Search and Discovery Article #90008©2002 AAPG Pacific Section/SPE Western Region Joint Conference of Geoscientists and Petroleum Engineers, Anchorage, Alaska, May 18–23, 2002.