Thermal evolution of sedimentary basins in Alaska

The complex tectonic collage of Alaska is reflected in
the conjunction of rocks of widely varying thermal maturity.
Indicators of the level of thermal maturity of rocks exposed
at the surface, such as vitrinite reflectance and conodont color
alteration index, can help constrain the tectonic evolution of
such complex regions and, when combined with petrographic,
modern heat flow, thermogeochronologic, and isotopic data,
allow for the detailed evaluation of a region?s burial and uplift
history. We have collected and assembled nearly 10,000
vitrinite-reflectance and conodont-color-alteration index values from the literature, previous U.S. Geological Survey investigations,
and our own studies in Alaska. This database
allows for the first synthesis of thermal maturity on a broadly
regional scale.
Post-accretionary sedimentary basins in Alaska show
wide variability in terms of thermal maturity. The Tertiary
interior basins, as well as some of the forearc and backarc
basins associated with the Aleutian Arc, are presently at their
greatest depth of burial, with immature rocks exposed at the
surface. Other basins, such as some backarc basins on the
Alaska Peninsula, show higher thermal maturities, indicating
modest uplift, perhaps in conjunction with higher geothermal
gradients related to the arc itself. Cretaceous ?flysch?
basins, such as the Yukon-Koyukuk basin, are at much higher
thermal maturity, reflecting great amounts of uplift perhaps
associated with compressional regimes generated through
terrane accretion. Many sedimentary basins in Alaska, such
as the Yukon-Koyukuk and Colville basins, show higher thermal
maturity at basin margins, perhaps reflecting greater uplift
of the margins in response to isostatic unloading, owing
to erosion of the hinterland adjacent to the basin or to compressional
stresses adjacent to basin margins.