Stratigraphy and depositional evolution of the uppermost Oligocene –Miocene succession in western Denmark

Abstract

The uppermost Oligocene – Miocene succession in Denmark is subdivided into six depositional sequences. The development of the succession was controlled both by tectonic movements and eustatic sea-level changes. Tectonic movements generated a topography, which influenced the depositional pattern especially during low sea level. This resulted in sediment by-pass on elevated areas and the confinement of fluvial systems to structural lows. Structural highs further created restricted depositional environments behind the highs during low sea level. The structural highs were also the locus for sandy spit deposits during transgression and high sea level. Initially sediment supply was from the north and north-east but shifted within the Middle Miocene to an easterly direction indicating a significant basin reorganisation at this time. Eustatic sea-level changes mainly controlledthe timing of sequence boundary development and the overall architecture of the sequences.Consequently, the most coarse-grained sediments were deposited within the forced regressive wedge systems tract, the lowstand systems tract and the early transgressive systems tract. The most distinct progradation occurred in the Aquitanian (Lower Miocene) and was associated with a cold period in central Europe.The subsequent rise of sea level until the Serravallian (Middle Miocene) resulted in an overall back-stepping stacking pattern of the sequences and in decreasing incision.