Climatic and environmental changes in the North Sea Basin during the Early Miocene

The Miocene Climatic Optimum (~17 to 14 Million years ago) has recently gained attention as a
future climate analogue. However, the number of climatic records from the northern high and
middle latitudes is very limited, so the global impact across this climatic transition is still poorly
understood. The most northernly located site penetrating a nearly complete Miocene succession is
located in the eastern North Sea Basin (Sdr. Vium borehole, Denmark). This research provides a
multi proxy investigation performed on the Lower Miocene part of the succession. The studied
interval corresponds with the time leading up to the onset of the Miocene Climatic Optimum.
A total of 44 samples have been studied for their relative abundances of major palynological
groups (dinocysts, acritarchs, spores, non-saccate pollen, saccate pollen and freshwater algae) and
for the dinocyst/pollen ratio. In addition, 11 selected palynological samples were studied for their
content of dinocyst and acritarch taxa (counting a minimum of 200 specimens per sample).
77 samples constitute the basis of a HH-XRF based chemical analysis. Furthermore, the n-alkanes
of 8 samples have been analysed in order to assess their potential within a paleoenvironmental
context.
This study provides an updated age model (derived from dinocysts) and sequence stratigraphy of
the Burdigalian (Early Miocene) succession of the Sdr. Vium core. The studied interval belongs to
the Sumatradinium hamulatum Zone, the Cordosphaeridium cantharellus Zone and the
Exochosphaeridium insigne Zone.
XRF analysis combined with palynology improved the existing sequence stratigraphical framework
of the studied site. Furthermore, the low resolution record of the n-alkanes show a good
correlation between high content of the C23-25 and position of sequence boundaries.
The changes in the relative abundance of warm-water dinocysts as well as alkenone-derived sea
surface temperature suggest a brief interval of colder sea surface conditions just prior to the onset
of the Miocene Climatic Optimum.