Jennifer Taylor , David Selby , Jeremy M. Lloyd , Craig Smeaton , James Bendle , Mathew Allison , Yuan Ling , Luca Podrecca , Bradley B. Sageman , William Austin , Sönke Szidat
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引用次数: 0
Abstract
Loch Sunart, a fjord in NW Scotland, UK, records Late Glacial to Holocene sedimentation preserving palaeoenvironmental changes associated with the deglaciation of the British-Irish Ice Sheet (BIIS). This study combines a multi-proxy approach (osmium isotope analysis, carbon, sulphur and nitrogen elemental and isotopic analysis together with X-ray fluorescence, alkenone biomarkers and benthic foraminifera) to contribute to our understanding of the regional nature of BIIS deglaciation and enable the reconstruction of palaeoclimate variations since the last glacial. The observed patterns in the applied proxies collectively suggest that between ∼18 and 12.9 cal ka BP as the BIIS retreated, Loch Sunart experienced increased glacial meltwater discharge. Throughout this period, 187Os/188Os values are more radiogenic than the contemporaneous open ocean waters (∼1.04–1.06), which are interpreted to reflect an increase in glacially eroded sediment flux directly associated with glacial retreat following the Last Glacial Maximum. During the Younger Dryas, the fjord experienced a pause in glacially derived sediment reflected by a minimum in 187Os/188Os (∼1.1), which was followed by an increase in 187Os/188Os to more radiogenic values (∼1.3) at the end of the Younger Dryas. Coincident with changes in 187Os/188Os values, alkenone-based %C37:4 values increase (40–60%), δ13Corg values decrease (−24‰) and foraminifera species indicative of restricted water renewal increased in abundance, suggesting a period of water stratification. A rapid shift in 187Os/188Os values toward a marine signature of ∼1 indicates that the basin experienced a breakdown in water stratification and renewed mixing from 5 cal ka BP. This interpretation is further supported by a coincident decrease in %C37:4 to <15%, and by distinct increases in wt% C, wt% N and δ13Corg. This multi-proxy approach, specifically integrating Os, provides additional insight to the BIIS in NW Scotland, in particular how such fjords can respond to glacial readvance during the Younger Dryas, which was not captured by previous studies.
期刊介绍:
Quaternary Science Reviews caters for all aspects of Quaternary science, and includes, for example, geology, geomorphology, geography, archaeology, soil science, palaeobotany, palaeontology, palaeoclimatology and the full range of applicable dating methods. The dividing line between what constitutes the review paper and one which contains new original data is not easy to establish, so QSR also publishes papers with new data especially if these perform a review function. All the Quaternary sciences are changing rapidly and subject to re-evaluation as the pace of discovery quickens; thus the diverse but comprehensive role of Quaternary Science Reviews keeps readers abreast of the wider issues relating to new developments in the field.