Changes in palynofacies and organic geochemistry as indicator for marine ingressions in the German Wealden

New palynological and geochemical data from the KB Rehburg-2 core covering the German Wealden (W1-4) illustrate the unique development of this depositional setting. Despite the temporary isolation of the Lower Saxony Basin (LSB) from the open ocean, several marine flooding events into the basin were detected. Marine ingressions are suggested to have entered from the west via the East Netherlands High, supporting the existence of an - at least temporary - seaway to the Boreal Realm. In the central and eastern parts of the LSB, indicators of marine influence are less prominent. In this study, we use a combined approach including palynofacies analysis, sedimentological and geochemical data in order to improve the understanding of the highly variable German Wealden depositional environment. The new data provides evidence for marine ingressions into the isolated LSB, insights into vegetation dynamics and palaeoenvironmental conditions.

A total of five different types of palynofacies were distinguished, which indicate changes in the oxygenation state of the water column as well as variations in salinity. Based on changes in continent-derived particle abundance, the proximity to the Deister-Hils Delta can be estimated. The most proximal palynofacies type stems from palaeosols, which are described for the first time in the German Wealden. Marine ingressions were identified using ecological preferences of aquatic palynomorphs (dinoflagellates, acritarchs, prasinophytes, Botryococcus) across the studied sedimentary sequence. Based on changes in palynofacies and geochemical proxies, ingressions already postulated in other studies were identified and a new, previously unknown ingression is observed.