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The Jurassic-Cretaceous boundary interval in northwest Europe is characterised by a distinctive climatic change from pronounced aridity toward more humid conditions. In order to better understand the timing and evolution of the environmental dynamics related to this climatic change, terrestrial and aquatic palynomorphs (spores, pollen, dinoflagellate cysts, freshwater algae) have been studied from two recently drilled cores. The cores, which are both located in the Lower Saxony Basin (northern Germany), provide two 139 m and 134 m thick non marine successions embedded in a high-resolution biostratigraphic framework. The lower part of the cores can be attributed to the Winder Formation (upper Tithonian-middle Berriasian), the upper part to the Buckeberg Group (middle-upper Berriasian). For reconstructing the arid to humid climate transition 110 samples have been analysed for their palynological content.

In the Lower Saxony Basin, the late Jurassic-earliest Berriasian vegetation was dominated by cheirolepidiacean conifer forests growing under arid conditions along a coastal belt. A marked decline in cheirolepidiacean pollen and the spread of pioneering plants records an increase in seasonal humidity in the early-mid Berriasian. In the mid-late Berriasian the presence of highly diverse floras reflects even more humid and warm conditions. Fluvio-deltaic mixed swamp forests, which grew landwards behind the coastal belt were composed of conifers, ferns, lycopods, horsetails, bryophytes, ginkgos, cycads and Bennettitales. Cheirolepidiaceans, probably forming part of mangrove-type plant communities, remained an important component of the coastal flora. The climatic shift correlates to the upper Subcraspedites lamplughi-middle Heteroceras kochi ammonite zones of the marine Boreal zonation scheme and is synchronous to the early-mid Berriasian shift from arid to humid recorded from southern England. (C) 2018 Elsevier B.V. All rights reserved.