Marine and terrestrial records of Toarcian (Early Jurassic) climate and environmental change - Phase 2: Evolution of Early Jurassic Environment in NE-Germany

• Applicant: Professor Dr. Lorenz Schwark
• Subject Area: Palaeontology ; Mineralogy, Petrology and Geochemistry
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 421920356

In the first phase of this project, we investigated environmental perturbations during the Pliensbachian/Toarcian and Toarcian environmental crisis formulating three hypothesis to be tested, all of which could be proven. 1) Toarcian warming was associated with a demise of a continental cryosphere. Ice melting impacted on 18O values of Tethyan shelf water and obscured the oxygen isotope temperature signal stored in biocalcifiers. Independent proof was achieved by establishment of a paleotemperature record based on ice volume-independent molecular paleothermometry using the TEX-86 proxy. 2) We postulated that Pliensbachian and early Toarcian climate events equally affected terrestrial as well as marine environments, proven by investigation of isotopic signatures in marine and terrigenous photosynthate. 3) Marine primary producer communities directly suffered from rising seawater temperatures and ocean acidification via rising atmospheric CO2 concentration. We identified six biotic events reflecting changes in primary producer associations (red versus green clades) in the Early Toarcian using triterpenoidal biomarker compositions of Toarcian sediments from Luxembourg.We now aim to extend the research on early Jurassic paleoenvironment evolution by extending the study objectives in both the spatial and temporal domain. Investigations addressing Pliensbachian/Toarcian environmental change were preferentially conducted in anoxic/euxinic basins with “bituminous facies”. Severe oxygen depletion affected carbon cycling in those basis and affords a separation of first-order global drivers from second-order regional drivers. Non-bituminous sections, particularly from the north Gondwana margin and Ibera that developed on carbonate platforms lack continuous sedimentation and a detailed record of environment change in the molecular and isotopic composition of organic material is difficult to achieve, due to erratic sedimentation/erosion and degradation of organics in oxygenated environments. We propose to study early Jurassic environmental change in the NE-German Basin, where sediments were deposited in a continuous and stratigraphically well-constrained marginal basin of the Toarcian shelf not subject to severe anoxia and development of bituminous facies. First order global drivers on pCO2 and carbon isotopes can thus be identified by means of molecular biomarker and isotope geochemistry.The Toarcian paleoenvironmental evolution occurred in the wake of the Gondwana break-up initiated by CAMP volcanism some 200 Ma ago. We will follow the entire succession of Rhaetian to Aalenian paleoenvironmental change employing two cores available in the NE-German Basin that have not been studied previously and will establish a chemostratigraphic and biostratigraphic framework for interpretation of early Jurassic paleoenvironmental change over a period of 30 Ma culminating in the Toarcian oceanic anoxic event.

• DFG Programme: Research Grants
• Co-Investigators: Dr. Matthias Franz; Dr. Karsten Obst