Source to sink evaluation of sediment routing in the Gulf of Alaska and Southeast Alaska: A thermochronometric perspective

Abstract

AbstractIn this study, we present a source to sink evaluation of sediment routing at the glaciated convergent margin in Southeast Alaska. We investigate the efficacy of thermochronology to record spatial and temporal exhumation patterns in synorogenic sediment using Neogene strata drilled by Integrated Ocean Drilling Program Expedition 341 in the Gulf of Alaska. We present 1641 and 529 new detrital zircon and apatite fission track ages, respectively, from strata deposited on the continental shelf, slope, and deep‐sea fans. These data are compared to results from the proposed source terrains, including the St. Elias Mountains and new data from the Alsek River. We find that the offshore Bagley‐Bering sediment contains grains recording cooling ages much older (80–35 Ma) than those reported from the St. Elias syntaxis (3–2 Ma), indicating that extreme rapid exhumation does not extend west of the Seward‐Bagley divide. Data from the sediment on the continental shelf, slope, and proximal deep sea all yield similar results, suggesting the same general source region since 1.2 Ma and limited sediment mixing along this glaciated margin. Data from sediment in the distal deep sea show that extreme, rapid, and deep‐seated exhumation was ongoing at ~11–8 Ma. Overall, this study demonstrates the strengths and limitations of using detrital fission track thermochronology to understand sediment routing on a glaciated convergent margin and to record changes in exhumation rates over geologic time scales.