Thermal Maturity, Tectonostratigraphic Terranes, and Regional Tectonic History: Example from Kandik Basin, Alaska: ABSTRACT

Abstract

The Kandik basin region of east-central Alaska provides an excellent example of how thermal-maturity data can be used in the analysis of tectonostratigraphic terranes. The northeast-trending Glenn Creek fault system marks the most fundamental structural break in the section. In the past, stratigraphic correlations have been extended across the fault zone. Their analyses prove that the thermal histories of the respective fault blocks are completely different; thus, the Glenn Creek fault zone is a terrane boundary. Northwest of the fault zone (Kandik River terrane), strata are mostly Early Cretaceous in age, and these rocks yield values of mean vitrinite reflectance (R{sub m}) ranging from 1.6 to 4.2%. In contrast, all but one of the Devonian shales analyzed from the southeast side (Tatonduk terrane) range from 0.6 to 1.2% R{sub m}. Analyses of illite crystallinity also show that the older Tatonduk terrane is within the zone of diagenesis, whereas much of the younger Kandik River terrane is within the anchimetamorphic zone. The authors infer that 7-10 km of overburden were eroded from the Kandik River terrane; rapid denudation, together with the dramatic paleothermal inversion across the terrane boundary, probably were accomplished through southeast-directed overthrusting. The geographic setting, thermal source, tectonic regime,more » and overburden required for the metamorphic event, however, all remain unidentified.« less