A new age model for the Pliocene of the Southern North Sea Basin: evidence for asynchronous shifts of marine and terrestrial climate.

The mid-Pliocene Warm Period (mPWP, 3254-3025 ka) represents the most recent interval in Earth's history where atmospheric CO₂ levels were similar to today. The reconstruction of sea surface temperatures (SSTs) and modeling studies have shown that global temperatures were 2-4 °C warmer than present. However, detailed reconstructions of marginal seas and/or coastal zones that enable linking climate evolution in the marine realm to that on the continents are lacking. This is in part due to the absence of precise age models for coastal zones, as they are generally dynamic systems with varying sediment and fresh water inputs. Here, we present a multi-proxy record of Pliocene climate change in the coastal Southern North Sea Basin (SNSB) based on the sedimentary record from borehole Hank, the Netherlands. The marginal marine setting of the Hank borehole during the late Pliocene provides an excellent opportunity to correlate marine and terrestrial signals, due to continental sediment input mainly from the proto-Rhine-Meuse river. We improve the existing low-resolution palynology-based age model for the Hank borehole using oxygen stable isotope measurements (δ¹⁸O) of the endobenthic foraminifera species Cassidulina laevigata, integrated with biochrono- and seismostratigraphy. Identification of hiatuses and freshwater effects in the record allows us to accurately isolate glacial-interglacial climate signals that can be linked to a reference global benthic δ¹⁸O stack. In tandem with the biostratigraphic age control this results in an age framework for the SNSB for the Late Pliocene (~ 3200-2800 ka). Our multi-proxy reconstruction for the mPWP shows a strong agreement between lipid biomarker and palynology-based terrestrial temperature proxies, which suggest a stable climate, 1-2 °C warmer than present. In the marine realm, however, biomarker-based SSTs show a large range of variation (10 °C). Nevertheless, the fluctuation is comparable to other SST records from the North Atlantic and Nordic Seas, suggesting that a common factor, most likely variations in the North Atlantic Current, exerted a strong influence over SSTs in the North Atlantic at this time. [ABSTRACT FROM AUTHOR]