TRACING CENOZOIC LOW-TEMPERATURE EVENTS IN SOUTHERN SWEDEN: THE APPLICABILITY OF FORWARD MODELLING APATITE (U-TH)/HE DATA

Southern Sweden is characterised by a Precambrian basement and occasional remnants of Phanerozoic cover rocks. A tentative reconstruction of the Mesozoic and Cenozoic thermotectonic development in southern Sweden has been made based on modelling of apatite fission track (FT) data in combination with studies of paleosurfaces. However, questions concerning the Cenozoic low-temperature history, less than 70°C, still remain: (1) Was there a variation in thickness of the Cretaceous-Paleogene deposits along the coastline and was central southern Sweden covered during the Paleogene? (2) Can the Cenozoic exhumation of southern Sweden be more precisely dated and hence be related to a regional tectonic process?

We aim to elucidate the Cenozoic low-temperature history of southern Sweden by performing (U-Th)/He measurements on a carefully selected subset of apatites from the coast and the interior of southern Sweden. Measured apatite helium ages will be compared with ages predicted using recently developed helium diffusion software. Tentative cooling histories, that have been obtained by modelling the FT results, are used as input data when modelling the obtained apatite helium ages. Where possible we aim to investigate the potential of utilising different grain sizes to better constrain thermal histories; grain size is a first order control on the temperature range of the He partial retention zone. As a result, we hope to reveal the accuracy and reliability of the low-temperature part of the thermal histories obtained from modelling of apatite FT data.