Abstract
In this study, we model the flexure of the Colville foreland basin in
northern Alaska and calculate the effective elastic thickness (Te) of
the Arctic Alaska terrane with a simple 3D flexural model. Previous
studies show that the elastic thickness of northern Alaska is 65 km;
however, the wavelength of the Colville foredeep is considerably shorter
for such an elastic thickness and indicates a thinner elastic thickness
for the area. Seismicity of crust, as a direct indicator of the
mechanical strength, reduces considerably at a depth of 25 km in
northern Alaska. We address these contrasting observations with a 3D
flexural model to better understand elastic thickness constraints for
the north of the Alaska lithosphere. We constrained Colville basin
geometry with a structural map of the foredeep, where the maximum depth
reaches 8 km towards the southwest of the basin. The flexural deflection
model of northern Alaska considers various parameters, and results are
compared to the observed data to obtain the best fit model. We applied
basin and topographic loads, including a crustal root load with a ratio
of 3.4-4.5 times to modern topography. Our obtained elastic thickness
value is 13-16 km, with less than a 3% average misfit between the model
and the observation. The results of this study indicate that the
Colville basin geometry is mainly controlled by loads of the Brooks
Range and basin deposits, and additional loads or density anomalies in
the crust are not required for the deflection of the basin.