Ordovician to Silurian magmatism on the Utsira High, North Sea: implications for correlations between the onshore and offshore Caledonides A. M. Lundmark T. Sæther R. Sørlie 10.6084/m9.figshare.3453599.v1 https://geolsoc.figshare.com/articles/dataset/Ordovician_to_Silurian_magmatism_on_the_Utsira_High_North_Sea_implications_for_correlations_between_the_onshore_and_offshore___Caledonides/3453599 <p>The age and tectonic significance of two basement granitoids cored on the Utsira High, Viking Graben, North Sea, are constrained by zircon LA-ICPMS data. Syenite in well 25/10-2R is dated to 482±2 Ma, with εHf<sub>(482)</sub> values from −4.4 to −5.8, and granite in well 16/1-12 yields an age of 436±3 Ma with εHf<sub>(436)</sub> values from +3.7 to −0.5. The evolved Hf-signature of the syenite demonstrates 482 Ma reworking of Palaeoproterozoic–Archaean crust, interpreted to reflect Taconian–Grampian orogenesis. New and recently published data from the offshore Caledonides allow a first-order correlation of the Utsira High basement with the surrounding on- and offshore Caledonides. The Utsira High occupies a similar position with respect to Dalradian rocks as the Scottish Midland Valley terrane. Geophysical data indicate a volcanic arc beneath the East Shetland Basin, forming a northwards continuation of the Utsira High basement. We propose that the offshore volcanic arc segments represent the northeastern continuation of the Scottish Grampian orogen across the Mesozoic North Sea rift. A north-striking terrane boundary fault is proposed to separate the volcanic arc from the East Shetland Platform and merge northwards with the offshore extension of the Great Glen Fault–Møre Trøndelag Fault Complex. </p> 2016-06-21 11:32:33 Scottish Midland Valley terrane Utsira High Scottish Grampian orogen 482 Ma reworking basement granitoids cored Caledonide East Shetland Platform arc Mesozoic North Sea rift continuation East Shetland Basin data Hf northward North Sea Utsira High basement Fault correlation Geology