BROOKS RANGE OF ALASKA AND EAST-VENEZUELAN CORDILLERA: REVISED COMPARISON
ROEDER, Dietrich H., Murnau Geodynamics Inc, 9225 West Jewell Place No. 107, Lakewood, CO 80227, [email protected] and HUNG, Enrique J., Venezuela Offshore Trinidad and Tobago, Chevron Global Technology Services Company, Puerto La Cruz, 6001, Venezuela, [email protected]
The Brooks Range and east-Venezuelan segments of the Cordillera both contain
fold-thrust belts of mid-Tertiary completion age, and both contain cover sheets
of pre-emplaced ophiolitic, basaltic, and metasedimentary composition. Both
involve marine passive-margin series (2 and 5 km thick) and foredeep fill (12
and 6 km thick), and both are associated with aging world-class petroleum
reserves. Both frontal fold-thrust belts contain late structural
traps beneath
piggybacked tectonic surface units. Both involve hydrocarbon systems of the
passive margin and/or the foredeep fill. Both areas face deep-basin
uncertainties, limits to drilling, and environmental restrictions.
In the Macal area (East Venezuela), two deep exploration wells re-define a
narrow Dahlstromian imbricate zone within a section of older detached folds.
This limits the prospectivity of the frontal belt mountainward. Based on surface
geology, well data, and 2D seismic data, the frontal belt has been described in
8 new structure cross
sections
.
Juxtaposing the Venezuelan Cordillera with the TACT model of the Brooks Range displays similarities in geology and in data coverage. Both zones of seismogenic coupling between lower crust and subducting slab are implied, but not documented. Reflection-seismic events suggest a 10 to 20 km thick layer of mobilized lower crust transmitting and strain-partitioning subductive shear to the surface. Both Cordilleran main bodies are vast terranes highlighted by active lineaments.