Middle to Late Jurassic palaeoclimatic and palaeoceanographic trends in the Euro-Boreal region: Geochemical insights from East Greenland belemnites

Abstract

During the Middle and Late Jurassic, Europe and the Boreal regions formed a network of semi-restricted, relatively shallow marine basins. Consequently, stable oxygen (δ18O) and carbon (δ13C) isotope records from belemnites were strongly influenced by changes in palaeoceanography and climate. New data from eastern Greenland, which formed the western margin of the critical Viking Corridor (the narrow seaway that linked the Tethys to the Boreal realm), and compiled data from the Subboreal Province and Tethys Realms are examined together. In both territories, increases in δ18Obel across the Lower and Middle Jurassic boundary indicate that cooling occurred, although this appears to be temporally offset and of variable magnitude across the western Subboreal Province and Tethys Realm. This suggests that changes in ocean current patterns played a major role in governing the δ18Obel signal. The Middle to Upper Jurassic transition is characterised by relatively heavy δ18Obel values in the Subboreal Province, but is less pronounced in the northwest Tethys, suggesting that this trend may have been caused by a strengthening of a southward current bringing colder Boreal waters southwards. The uppermost Jurassic shows increases in both δ18Obel and δ13Cbel, consistent with the observed VOICE event as recorded in Boreal terrestrial organic matter δ13C, and supporting this evidence that the Boreal realm become isolated from the lower latitudes across the Jurassic – Cretaceous boundary.