Late Cretaceous−Paleogene burial and exhumation history of the Southwestern Basement Province, Svalbard, revealed by zircon (U-Th)/He thermochronology

We apply zircon (U-Th)/He low-temperature thermochronology to metasedimentary sequences of the Southwestern Basement Province of Svalbard to investigate the shallow crustal tectonics of Svalbard and the High Arctic. We resolve Cretaceous through Paleogene time-temperature histories for four areas of the province: Sørkapp Land, Wedel Jarlsberg Land, Oscar II Land, and Prins Karls Forland. Results indicate peak Late Cretaceous temperatures of ~175–185 °C in the south (Sørkapp Land, Wedel Jarlsberg Land) and >200 °C in the north (Oscar II Land) as a consequence of maximum burial and an elevated geothermal gradient (>40 °C/km). Late Cretaceous cooling affected all areas during regional exhumation related to initial rifting in the Eurasian Basin to the north. A subsequent heating event (recorded at Wedel Jarlsberg Land and Oscar II Land) from ca. 53–47 Ma is interpreted to result from tectonic burial during Eurekan deformation and development of the West Spitsbergen Fold- and-Thrust Belt. Our thermal models reveal a subsequent cooling event (47–34 Ma) corresponding to a shift in tectonic regime from compression to dextral strike-slip kinematics during Eurekan deformation; exhumation of the West Spitsbergen Fold- and-Thrust Belt coincided with strike-slip tectonism. Throughout Eurekan deformation, Prins Karls Forland resided at temperatures >200 °C and records cooling during post-34 Ma extension. Our models indicate 2.5–3.5 km of unroofing in Wedel Jarlsberg Land and Oscar II Land, and >4 km of unroofing of Prins Karls Forland, which is a deeper structural level of the West Spitsbergen Fold-and-Thrust Belt than other exposures on Spitsbergen. The results of this study document elevated heat flow in the Late Cretaceous, extend spatial resolution of Late Cretaceous crustal cooling documented across Svalbard, and illustrate the temporal and thermal evolution of the West Spitsbergen Fold-and-Thrust Belt, which is necessary for an improved understanding of Arctic geodynamics. © 2018 The Geological Society of America. All rights reserved.