From the Coleen-Old Crow highlands south to the Yukon River, Alaska's eastern interior is a geologic collage of northeast-trending slivers which have been displaced in conveyer-belt fashion since the Jurassic along a trans-Arctic shear system which extends to the eastern end of the Arctic archipelago. Rock sequences of the region have remarkable affinities with the North Slope and Arctic island assemblages, suggesting a common origin in the Arctic Ocean region.

Pre-Cretaceous rocks can be attributed to four successive paleotectonic phases: (1) Cambrian through Lower Devonian carbonate rocks and shales are shelf-slope-basin sequences recording passive subsidence of an Atlantic-type shelf margin; (2) Middle through Upper Devonian siliceous black shales and turbidites document trench development and associated folding, uplift, and reworking of deep-sea sediments, a dramatic change ascribed to oceanic plate subduction; (3) Upper Paleozoic rocks are extremely varied and include acid intrusives and metamorphic rocks, as well as a spectrum of sedimentary deposits ranging from deep marine to fluvial. Collectively, they are attributed to a major period of orogenic uplift; and (4) early Mesozoic rocks are dominantly post-orogenic molassoid clastics. >

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The transcurrent movements which transported these sequences into Alaska and contiguous Yukon probably began in the Cretaceous as a result of southwesterly Arctic plate motion. Simultaneously, however, northwesterly translation of cordilleran elements interfered with this movement, causing complex dovetailing of geologic blocks and the evolution of a curious, but systematic pattern of orogenic uplifts. Thermal activity associated with these uplifts has locally reduced the originally high petroleum potential of the region.

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