Early Cretaceous lignites from inner-continental Asia as paleoclimate archive

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Records documenting the climatic and environmental conditions prevailing in inner-continental paleo-Asia during the Early Cretaceous greenhouse phase are sparse, fragmentary and often contradictory. For the Aptian-Albian interval, a small set of proxy-derived continental paleotemperature estimates shows comparatively cool mean air temperatures, which contrast with exceptionally warm sea-surface temperatures obtained from the marine realm. The continental Choir-Nyalga Basin of central Mongolia contains thick, lignite-rich successions, which host an exceptionally well-preserved conifer-dominated flora representing a mid-latitude wetland ecosystem. This research proposal aims at studying these lignite-bearing deposits by combining brGDGT-based paleothermometry and coal petrology with palynological analyses. Investigations will focus on material from three open-cast lignite mines and a drill core studied and sampled during a previous field expedition. Preliminary organic geochemical and palynological results demonstrate that the low-mature coals and clastic interbeds are well suited for the chosen approach. The existing temporal framework will be improved by combining terrestrial carbon-isotope stratigraphy and palynostratigraphy with radiometric U/Pb chronology from tuffaceous horizons. The project will deliver new and important paleotemperature and paleovegetation data, which will help to better constrain the climate and ecosystem dynamics of continental interiors during times of exceptional global warmth.