Late Paleozoic-Mesozoic Evolution of Arctic North America

Ashton F. Embry

Correlation of the upper Paleozoic to Mesozoic successions of northern Alaska and the Canadian Arctic Islands has revealed close stratigraphic and tectonic links between these two petroliferous areas. Depositional and tectonic trends have been reconstructed for Arctic North America, and such interpretations can assist petroleum assessments of unexplored areas in the region.

Five regional unconformities are recognized, and these allow the succession to be divided into four tectonic sequences: Carboniferous-Lower Permian, Lower Permian-lowest Cretaceous, Lower Cretaceous, and Upper Cretaceous. The first sequence, Carboniferous-Lower Permian, developed during a phase of rifting when a series of pull-apart basins formed along the eroded Ellesmerian deformation belt. Fan deltas and shelf carbonates with equivalent basinal shales and evaporites characterize this sequence.

An episode of uplift and faulting terminated the first sequence. The second sequence, Lower Permian-lowest Cretaceous, developed under conditions of thermal subsidence over the rifted areas. Clastic sedimentation was dominant with alternating shelf and deltaic deposition. Significant uplift reflecting the initiation of the Amerasian basin by rifting began in earliest Cretaceous. Sequence three, Lower Cretaceous, was deposited during the rifting phase of the Amerasian basin and consists of thick, deltaic, clastic wedges derived from either the craton or the uplifted Brooks Range.

The onset of sea-floor spreading in the Amerasian basin in earliest Late Cretaceous resulted in widespread uplift. The fourth sequence, Upper Cretaceous, was deposited coincident with sea-floor spreading in the Amerasian basin. Initial deposits were bituminous shales which were followed by thick clastic wedges that prograded into the ocean basin. This sequence was terminated by uplift in latest Cretaceous-earliest Tertiary when sea-floor spreading switched to the Eurasian basin.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.