Tectonic Evolution of the Bristol Bay basin, southeast Bering Sea: Constraints from seismic reflection and potential field data

Abstract

We interpret the tectonic evolution of the Bristol Bay basin, also known as the North Aleutian basin, on the basis of a deep seismic reflection profile, lithologic data from a well, unreversed seismic refraction profiles, a bathymetry profile, a magnetics profile, forward modeling of a gravity profile, and flexural modeling of a basin‐wide paleosurface. We present evidence that (1) an early or middle Eocene through late Miocene phase of extension led to fault‐controlled subsidence; (2) a late Eocene through early Miocene phase of volcanic‐arc loading led to flexural subsidence, which was amplified by additional factors possibly including lithospheric cooling, tectonic compression, reverse or thrust faulting, or small‐scale intrusions of dense magma; and (3) a late Miocene through Holocene resurgence of arc volcanism and a northward prograding delta continued (or possibly increased) flexural subsidence in the back arc region. Our interpretations imply that the fault‐controlled subsidence in the Bristol Bay basin is genetically linked to that found in the other outer Bering Shelf basins, but the subsequent flexural subsidence of these basins is not related. More fundamentally, our observations suggest that the basin's evolution is unusual and has components typically found in both back arc (extension) and retroarc foreland (flexure) basins.