Significant changes in global climate and carbon cycling occurred during the Early Cretaceous. This study examines the expression of such climatic events in high-latitude Svalbard together with the stratigraphic utility of carbon-isotope stratigraphies. Isotopic analysis of fossil wood fragments (from the Rurikfjellet, Helvetiafjellet, and Carolinefjellet formations, Festningen, Spitsbergen) record a distinctive pattern including a negative isotope excursion preceding a positive event, correlatable with the global early Aptian isotope event. Our carbon-isotope profile improves the stratigraphic correlation and relative dating of the succession. We show that the upper part of the Helvetiafjellet Formation was deposited during the early Aptian, and not the late Barremian, as previously thought. Furthermore, we estimate an age for the abrupt contact of the Rurikfjellet Formation with the overlying Helvetiafjellet Formation (associated with a pulse of igneous activity) to be ca. 129 Ma or ca. 124 Ma, depending on which age model for the Early Cretaceous is used.

The well-known dinosaur footprints of the Helvetiafjellet Formation at Festningen are constrained to the middle Barremian and, coupled with floral data, support a warm late Barremian prior to the Aptian carbon-isotope event. The appearance of glendonites at 655 m in the Carolinefjellet Formation is consistent with global cooling in the late Aptian–early Albian.