Meso–Cenozoic evolution of the southwestern Chukchi Borderland, Arctic Ocean

Abstract

Abstract A regional stratigraphic framework is developed for the North Chukchi Basin and southern margin of the Chukchi Borderland based on a grid of 2D multi-channel seismic reflection profiles tied to exploration wells on the U.S. Chukchi Shelf. The northern flank of the North Chukchi Basin displays a 16 km succession of mainly Cretaceous and Cenozoic strata that progressively onlaps an unconformity (Au) on the southern margin of the Borderland. Rocks beneath the unconformity are inferred to represent (A) crystalline basement that may have affinity to the Peary terrane, (B) deformed growth strata that may be related to Carboniferous to Jurassic strata on the Chukchi Shelf, and (C) seaward dipping reflections (SDRs) likely related to oceanic igneous rocks or exhumed mantle beneath the North Chukchi Basin. The SDRs indicate that the southwestern margin of the Borderland is a rifted continental margin and loosely constrained age control suggests that rifting occurred between Middle Jurassic and earliest Cretaceous. Cretaceous through Cenozoic strata that fill the North Chukchi Basin are part of the Brookian megasequence deposited across the foreland of the Chukotka and Brooks Range orogens. These strata form a series of clinothems deposited by northward-migrating depositional systems that progressively filled the North Chukchi Basin and buried the southern flank of the Borderland. Onlap of the Au by bottomset facies indicates that deep water conditions prevailed along the northern basin margin during Aptian–Oligocene. Foreset and topset facies onlap and overtop the highest standing part of the Borderland and indicate that marine slope and shallow marine to deltaic environments reached the Borderland during the Oligocene and persisted thereafter.