Earliest Cretaceous (late Berriasian) glendonites from Northeast Siberia revise the timing of initiation of transient Early Cretaceous cooling in the high latitudes

Abstract

The studies of past climatic changes form the basis for predicting our future anthropogenic world and are among the most prominent topics in current Earth sciences. Although the Cretaceous is generally considered as a greenhouse period in Earth's history, a number of significant cooling events based on an array of climatic proxies have been identified. Here we present the first data on Berriasian (Ryazanian) glendonite findings from the paleontologically well dated Lower Cretaceous succession of northeastern Siberia. Based on well calibrated Buchia and ammonite biostratigraphy, the stratigraphic interval across which the glendonites occur is restricted to the late Berriasian. Stable carbon isotope (d13C) values of the studied glendonites clearly suggest the precipitation of ikaite from marine water without any significant contamination from biogenic methane. Our results, when integrated with other available paleoclimatic proxies from elsewhere in the high latitudes, suggest a revision of the initiation of Early Cretaceous cooling in the high latitudes from the Valanginian to the late Berriasian. All known occurrences of Lower Cretaceous glendonites in both the northern and southern hemispheres are reviewed.