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

15 Ma old Nördlinger Ries是其他行星和卫星上撞击结构及其沉积陨石坑填充的最重要的陆地模拟地点之一。精确重建其撞击后的侵蚀和沉积历史有助于了解火星等行星上的水生沉积和气候演化。对于中新世Ries陨石坑盆地，假设流入溶液的化学变化、水文变化和陨石坑底部的温度下降是沉积的主要控制因素，而气候变化是叠加波动的原因。因此，本研究拟通过分析撞击后碳酸盐的87Sr/86Sr、碳和氧（d13C、d18O、D’17O）同位素组成，追踪撞击后的初级和次级喷出层的连续侵蚀和陨石坑底部的热演化。此外，本文还分析了现今地表水和地下水，作为不同岩性单元（结晶基底岩、细橄榄岩、邦特角砾岩、三叠系和侏罗系沉积岩）风化溶液的参考。具体来说，锶同位素比值被用来重建溶质来源的变化和水文随时间的变化。氧同位素比值被用来揭示水温的变化趋势，特别是在沉积演替的早期。分析了碳酸盐岩d13C值异常高的原因。目的和预期结果是精确重建影响里斯陨石坑湖化学演化的过程，这是一个区分行星陨石坑填充序列中的外部（气候）与内部（侵蚀和陨石坑底部温度下降）因素的模型。

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.