A Volcanic Ash Layer in the Nördlinger Ries Impact Structure (Miocene, Germany): Indication of Crater Fill Geometry and Origins of Long?Term Crater Floor Sagging

Since its recognition as an impact structure 60 years ago, no volcanics were anticipated in the circular depression of 14.8 Ma old Nördlinger Ries. Here, we describe for first time a volcanic ash-derived clinoptilolite-heulandite-buddingtonite bed within 330 m thick Miocene lacustrine crater fill. Zircon U-Pb ages 14.20 ± 0.08 point to source ash Pannonian Basin, 760 km east The diagenetically derived zeolite-feldspar occurs laminated claystones Ries soda-lake stage and represents unequivocal stratigraphic marker this basin, traceable from marginal surface outcrops 218 below center. These relationships demonstrate deeply bowl-shaped geometry fill sediments, not explainable by sediment compaction corresponding backstripping alone. most formed at shallow water depths, must reflect 134 +23/?49 sagging floor. We attribute closure dilatant macro-porosity fractured brecciated floor during basin sedimentation loading, process that lasted more than 0.6 Myr. As result, outcrop pattern lithostratigraphic crater-fill units present erosional plane forms concentric pattern. Recognition provides insights into temporal formation subsidence have implications impact-hosted lakes on Earth Mars.