A δ13CORG STACK AND CLAY MINERALOGICAL PROXY RECORD OF CLIMATE CHANGE THROUGH THE LATE JURASSIC–EARLY CRETACEOUS OF NORTH-WESTERN EUROPE: AN INTEGRATED INTER-REGIONAL CORRELATION

The latest Jurassic–Early Cretaceous interval was characterised by a number of carbon cycle perturbations and a climatic shift in north-western Europe from humid to semi-arid conditions. However, the temporal and geographic extent of these events are poorly understood. This is due to a scarcity of high resolution records and difficulties in correlation because of faunal provincialism and insufficiently constrained chronostratigraphy. We identify and correlate a number of isotope excursions from several biostratigraphically-constrained organic carbon-isotope records from the Norwegian Continental Shelf with the Kimmeridgian‒Tithonian (Upper Jurassic) Kimmeridge Clay Formation of the Dorset type area, and with late Tithonian‒Berriasian (Upper Jurassic‒Lower Cretaceous) records of Svalbard and Siberia. Our regional-scale correlation reflects the consistency of the C-isotope signal in the seas of north-western Europe at the time of deposition, and a high correlation potential across significant distances. In particular, correlation of C-isotope signals in the Early Cretaceous attests to sufficiently open marine conditions in the Greenland-Norwegian Seaway to record global carbon cycle variations despite a sea level lowstand.

Precise correlation is critical for stratigraphic fidelity and for assessing the nature of widespread organic matter deposition. Whereas physical properties or biostratigraphic data alone usually do not allow precise correlation, our integrated approach enables us to identify and correlate synchronous events amongst inter-regional sections. Time series analyses of TOC records from two wells reveal cycles that strongly resemble those of the 405-kyr and 100-kyr eccentricity components recorded in Dorset. Correlation to the cyclostratigraphic framework of Dorset provides independent support of our age model, which provides a basis for understanding the timing and extent of Late Jurassic climate change. As the clay mineral kaolinite is deposited in humid environments, the Late Jurassic climatic shift from warm–dry conditions is suggested by its abundance. Tracing this shift across a Boreal–High Boreal transect may show a broad perspective of the timing of this event, and the relationship to a presented 𝛿¹³C_org stack of the studied wells.