Ejecta erosion, thermal and chemical lake evolution of the Ries impact structure

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The 15 Ma old Nördlinger Ries is one of the most important terrestrial analogue sites for impact structures and their sedimentary crater fills on other planets and moons. The precise reconstruction of its post-impact erosional and sedimentary history helps to understand aquatic sedimentation and climate evolution on planets such as Mars. With respect to the Miocene Ries crater basin, the hypothesis is that chemical changes in inflowing solutions, changes in hydrology, and the temperature decline of the crater floor were major controlling factors of sedimentation, while climatic changes are responsible for superimposed fluctuations. Therefore, the present proposal focuses on tracing the successive erosion of the primary and secondary ejecta layer and the thermal evolution of the crater floor by analyzing the 87Sr/86Sr, carbon and oxygen (d13C, d18O, D'17O) isotopic composition of post-impact carbonates throughout a well-preserved drill core of the central crater basin. In addition, present-day surface and subsurface waters are analysed as references for weathering solutions of different lithological units (crystalline basement rocks, suevite, Bunte Breccia, Triassic and Jurassic sedimentary rocks). Specifically, strontium isotopic ratios are used to reconstruct changes in the provenance of solutes and hydrological changes with time. Oxygen isotope ratios are used to reveal trends in water temperatures, especially in early parts of the sedimentary succession. The reason for anomalously high carbonate d13C values will be elucidated.The aim and expected outcome is a precise reconstruction of processes affecting the chemical evolution of the Ries crater lake, a model to distinguish external (climatic) versus intrinsic (erosion and crater floor temperature decline) factors in planetary crater fill successions.