Impact of Late Cretaceous to Neogene plate tectonics and Quaternary ice loads on supra-salt deposits at Eastern Glückstadt Graben, North German Basin

Abstract

In this study, we investigate the impact of Late Cretaceous to Neogene plate tectonics and Pleistocene ice load on the post-Jurassic strata above the Waabs salt wall within the Eastern Gluckstadt Graben by integrating reflection seismic, parametric sub-bottom profiler and well data. Previous studies showed that a collapse graben developed above the salt during several tectonic pulses. However, due to the lack of age constrains, the relationship between local salt tectonics and variations of the regional stress field caused by plate tectonics was just little constrained. Here, we introduce an inter-Cenozoic stratigraphy enabling us to infer and date three major salt tectonic phases. During the Late Cretaceous to Eocene, Africa–Iberia–Europe convergence and subsequent Pyrenean orogeny strata above the salt wall were pushed upwards and faulted. Thickness variations of the Upper Cretaceous and Eocene strata imply at least two pulses for this upward push. The second phase includes the major graben collapse in the Neogene, when the stress regime changed from a compressional to an extensional regime. The third phase is a period of locally differing tectonic reactivation likely caused by ice sheet loading and unloading during the Quaternary. Based on time-isochore and time-structure maps, we elucidate how this last glacial phase of salt tectonic movement likely formed the present day Mittelgrund shoal within the Eckernforde Bay. The spatial correlation between shallow faults and freshwater seepage implies further a causal relationship between fluid migration and faulting.