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摘要
We present a partial reconstruction of NE Atlantic climatic variability, the first based on stratigraphic evidence obtained from a vegetated dune system of the northern Scottish coast. The dune system at Dunnet Bay is fringed by prominent submerged peat deposits, exposed only at low tide, which record stable climatic periods when lower-energy wind regimes prevailed, allowing the formation of organic soils. By contrast, periods of sand influx, are associated with high-energy conditions. The majority of sand material tested had a narrow range of particle sizes and major element composition, supporting the interpretation of a common Aeolian origin. Sand layers were dated with optically stimulated luminescence (OSL) and peat layers were C-14-dated in four cores (C1-C4) and seven sample sections (S1-S7). The results from the two master sections S1 and S2 (I km apart) indicate synchronous episodes of climatic stability (7650-6310, 4340-4000, 2690-2290, 100-0 cal a BP) and instability (6310-4340, 4000-2690, 2290-2000, 170-100 cal a BP) in spite of very different mean accumulation rates at the two sites (1 mm a(-1) at S1 and 0.2 mm a(-1) at S2). Phases of sand deposition (i.e. Aeolian activity) at Dunnet tend to be associated with high average levels of chloride in the Greenland Ice Sheet Project 2 ice core (GISP2). Phases of peat development show a fairly good correspondence with low ice-rafting activity in the NE Atlantic and with indicators of wetness measured from a peat bog in SW Sweden. By contrast, comparison of the Dunnet depositional timeline with other regional studies (e.g. Hebrides and Orkney) shows little synchronicity. This suggests that (a) local scale variables have a strong effect on regional patterns of dune instability, and (b) the geological and geographic settings of Dunnet Bay mean that only large climatic regime shifts in the NE Atlantic are capable of triggering instability and being preserved in the depositional record.
- 出版日期2013-1-1
