The Boltysh meteorite impact crater, Ukraine, formed at the Cretaceous-Paleogene boundary at c. 65.2 Ma. A borehole drilled in the central part of the crater cored a 400 m thick high-resolution lacustrine succession that covers the Dan-C2 hyperthermal event associated with a negative carbon isotope excursion (CIE). Continuous terrestrial records of past hyperthermals are of limited availability, which makes this record a unique case study of the continental impact of rapid climate warming. Here, we use high-resolution sedimentological core log data together with thin section, X-ray diffraction, microprobe and palynological analyses to 1) reconstruct lake sedimentological and ecological development across the CIE and 2) assess the environmental effect of hyperthermals on terrestrial ecosystems. Based on detailed facies analysis, 5 gradual stages of lake evolution are identified, which show a strong relationship to carbon isotope shifts and associated climatic trends. Initially, sediment supply into the Boltysh lake was controlled by crater morphology. During later lake stages sediment supply was increasingly controlled by changes in inflow-evaporation ratios which affected seasonal stratification patterns and longer-term lake levels. An inferred increase in atmospheric pCO2 related to the carbon isotope excursion, together with increasing mean annual temperatures, was likely responsible for periodic increases in biological activity of photosynthesising organisms and biomass production. These fluctuations in facies and lake settings largely correspond to orbital-paced moisture availability oscillations. The gradual reduction in sediment supply commencing during early lake evolution prior to CIE inception suggest that the Dan-C2 event did not initiate sedimentary changes, but intensified sedimentary response to orbital controlled climate change.
Initial drilling of the Boltysh meteorite crater was funded by Natural Environment Research Council (NERC) grant NE/D005043/1. The authors are extremely grateful to the valuable scientific contributions of S. Kelley and I. Gilmour. The constructive and critical reviews by M. Schuster and an anonymous reviewer greatly helped to improve this manuscript.
- Boltysh crater
- Early Danian Dan-C2 CIE
- lacustrine facies
- lake formation