John Decker, Jeff Corrigan, and Steve Bergman
Quantifying the timing and magnitude of syn- and post-orogenic loading and unroofing within fold and thrust deformation belts and adjacent foreland basins is critical for evaluating reservoir quality, the timing and degree of source rock maturation, and the timing of trap development. The present day subsurface thermal structure and the timing and amount of eroded section during the Brookian Orogeny in North Alaska have been quantified by integrating DST and log temperature, apatite fission track, vitrinite reflectance, and sonic velocity data. Constraining the present-day thermal structure is particularly important for interpretation of thermal indicator data in this area, because thermal gradients systematically vary within the range 25-55 °C/km with the highest gradients present along the crest of the Barrow Arch. Erosion estimates range from 0-0.6 km in the Prudhoe Bay/East Beaufort Sea area, and increase to the west and south, reaching ~1.8 km the Point Barrow area, and >3.7 km along the Brooks Range mountain front. The spatial and temporal distribution of erosion reflects contributions from short-term compressional and long-term isostatic processes. Significa erosion (>2-3 km) during short periods (<5 Ma) is localized along thrust sheets in-board of the deformational fronts and was responsible for synchronous deposition of clastic wedges outboard of the deformational fronts. Surface fission track data delineate the culmination of several discrete Brookian thrust belts (ca. 60, 45, 20 Ma), the latter two of which are localized in the NE Brooks Range. Protracted post-orogenic erosion west of the Shaviovik Front since 60 Ma is due to flexural tilting of the foreland and represents an isostatic response to unroofing of the orogen.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California