Maastrichtian offshore carbonate sediments and transitional estuarian quartz arenite (primarily subarkosic/arkosic) deposited in N Germany, underwent indirect effects by end-Cretaceous plume volcanism (Caribbean Arc/Antilles, Amirante Arc/Seychelles, Deccan Traps) and by the Chicxulub impact during climate change. In addition, brines of local salt structures had increasing influence on pore water chemistry of siliciclastics deposited in rim synclines and sub-rosion bowls during the transition from salt pillow state (Upper Campanian/Maastrichtian) to diapirism since the KPgB (66.043 Ma) until end-Paleocene. As main drivers degassing (CO 2 , SO 2 et al.), temperature rise, acid rain/metal toxicity of both volcanic and impact origin caused kill effects by acidification (pH-drop) of sea water resp. dissolution processes on land initiated by complex acid mixtures onto both marine and continental sediments; all in all, leaving a remarkable reduction of the clastics' primary mineral content, accompanied by kaolinite in-situ neoformation (quartz, kaolinite). Furthermore, driving effects even controlled lithofacies and sequence-analytical patterns (LST, TST, HST). Around the Lower/Upper Maastrichtian B. (MFS) radiolarian ooze was deposited across flat estuarian mouth channels during an ingression (tsunami), originally as soft pebbles, then diagenetically slightly consolidated. Surprisingly, the radiolarian skeletons normally composed of opal or celestite, were identified as β-quartz and elementary silicon. The latter hitherto unknown in nature, demands extreme reducing conditions (in Industries: by elementary A1, Mg, C) in pore water as How to cite this paper: Schneider, W. and Salameh, E. (2020) End-Cretaceous Quartz Arenite Formation in an Estuarian Environment under Brine Influence, N. Germany; Linked to both Deccan Volcanism and Chicxulub Impact Degassing during Climate Change. Open Journal of Geology,