Establishing the T-R Sequence Record in the Initial Stages of Chukchi Sea Basin Analysis

Michael B. Mickey, Ashton F. Embry, Hideyo Haga

Five offshore exploration wells were drilled during 1989-91 in the Chukchi Sea, a previously untested frontier which lies west of the Alaskan North Slope. High resolution biostratigraphic analysis using mainly Foraminifera has been carried out on each of the wells, and also on a deep onshore well drilled by the U.S.G.S. The species present, the total numbers of forams, and the faunal diversity have all been used in combination with lithologic data to divide the succession of each well into T-R sequences. These sequences are mainly bounded by unconformities and range in age from Pliocene to Late Mississippian.

The recognized sequences have been correlated with the established 2nd and 3rd order sequences of the adjacent North Slope and the Sverdrup Basin of Arctic Canal. These areas and the Chukchi Sea region formed portions of a continuous seaway from Mississippian to earliest Cretaceous time and have many stratigraphic and tectonic features in common.

The sequences determined in the Chukchi Sea wells closely correlate in terms of age and lithology with the sequences of northern Alaska and the Sverdrup Base However, tide Chukchi sequences are relatively thin especially when compared with equivalent sequences in the Sverdrup Basin. Because the Chukchi Sea wells were drilled on large highs, it is probable that the sequences have undergone substantial erosion and truncation at these locations. In areas adjacent to the major highs it is possible that substantial intervals of reservoir and source rocks, like those encountered in the Sverdrup Basin, have been preserved.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995