Early Holocene loessic colluviation in northwest England: new evidence for the 8.2 ka event in the terrestrial record? PETER J. VINCENT, TOM C. LORD, MATT W. TELFER AND PETER WILSON BOREAS Vincent, P. J., Lord, T. C., Telfer, M. W. & Wilson, P. 2010: Early Holocene loessic colluviation in northwest England: new evidence for the 8.2 ka event in the terrestrial record? Boreas, 10.1111/j.1502-3885.2010.00172.x. ISSN 0300-9483. Twelve new samples of loessic silts from widely spaced locations on the karst uplands of northwest England have yielded Optically Stimulated Luminescence (OSL) dates that fall within or overlap with (within uncertainties) the early to mid-Holocene period (11.7–6.0 ka), and support three already-published Holocene ages from similar sediment from this region. Nine of the 15 dates are coincident with the hypothesized climatic deterioration at 8.5–8.0 ka in the North Atlantic region and eight are coincident with the 8.2 ka event. These dates demonstrate that the silts are not primary air-fall loesses of deglacial/Lateglacial age (c. 18.0–11.7 ka) but have been reworked and now consist of loess-derived colluvial deposits; we consider the ages to be reliable as there is no compelling evidence to indicate that the samples are partially bleached. There is no substantive archaeological or palynological evidence for Late Mesolithic hunter-gatherers having had a major impact on the landscape, and it is considered highly unlikely that these people triggered colluviation. We estimate that during the 8.2 ka event there was a reduction in mean annual air temperature at these upland locations of 2.6–4.6 1C, and proxy evidence from other sites in- dicates a shift to wetter conditions. It is inferred that there was greater snow accumulation in winter, that the snowpack survived for longer periods, and that there was an increase in the magnitude and frequency of frost- related processes and meltwater flooding. Together, these changes in climate and their associated (sub)surface processes were responsible for the reworking of the loess. The OSL dates indicate climatically induced landscape dynamism in Great Britain during the latter half of the ninth millennium. Peter J. Vincent, formerly Department of Geography, University of Lancaster, Lancaster LA1 4YB, UK; Tom C. Lord, Lower Winskill, Langcliffe, Settle BD24 9PZ, UK and Centre for North-West Regional Studies, University of Lancaster, Lancaster LA1 4YB, UK; Matt W. Telfer, Oxford University Centre for the Environment, South Parks Road, Oxford OX1 3QY, UK; Peter Wilson (corresponding author, e-mail: p.wilson@ulster.ac.uk), Environmental Sciences Research Institute, School of Environmental Sciences, University of Ulster, Coleraine, Co. Londonderry BT52 1SA, UK; received 14th September 2009, accepted 28th May 2010. The most pronounced centennial-scale anomaly in Ho- locene proxy-climate records in the North Atlantic re- gion is the 8.2 ka event (Alley et al. 1997; Alley & A ´ gu´stsdo´ttir 2005; note that throughout this paper dates are given as b2k unless otherwise specified (Ras- mussen et al. 2007; Wolff 2007)). The event is especially prominent in oxygen isotope records of the Greenland ice cores (Johnsen et al. 2001; Muscheler et al. 2004; Rasmussen et al. 2007; Thomas et al. 2007) and in the lithic, petrologic and foraminiferal content of marine sediments (Bond et al. 1997; Ellison et al. 2006; Kleiven et al. 2008), but has also been recorded in numerous terrestrial proxy records (Klitgaard-Kristensen et al. 1998; Tinner & Lotter 2001; Magny et al. 2003; Nesje et al. 2006). The anomaly is characterized by an excur- sion towards cooler temperatures, peaking sometime between c. 8.5 and 8.0 ka, lasting 70–200 years, and often showing two distinct maxima (Nesje & Dahl 2001; Magny et al. 2003; Keigwin et al. 2005; Lutz et al. 2007). Some records also indicate that the 8.2 ka event punctuated a longer interval of climate downturn var- iously placed between c. 8.6 and 8.0 ka (Rohling & P ¨alike 2005) and c. 9.0 and 8.0 ka (Alley et al. 1997; Hu et al. 1999; Ellison et al. 2006). In northwest England, a phase of marked climate cooling identified in the sedi- mentary record of Hawes Water, north Lancashire (8 m a.s.l.; Fig. 1) occurred at 8.38 ka and lasted for 150 years (Marshall et al. 2007). A high-resolution (1–2 years) record based on oxygen isotope data along with speleothem ages from several caves in northwest England have confirmed the regional occurrence of the 8.2 ka event (at 8.2 ka) with a duration of 150 years (P. Hopley, pers. comm. 2008). There is a general con- sensus that the most likely cause of the 8.2 ka anomaly is disruption of the Meridional Overturning Circulation in the North Atlantic as a result of freshwater input from the final collapse of the North American ice sheet, with the two-stage nature of the anomaly possibly correlating with the drainage of the proglacial lakes Ojibway and Agassiz (Barber et al. 1999; Ellison et al. 2006; Wiersma & Renssen 2006; Kleiven et al. 2008). In this paper we report Optically Stimulated Lumi- nescence (OSL) dates from silt deposits at widely spaced (35–50 km) locations on the outcrop of the Carboniferous Limestone of northwest England. It has been known for some considerable time that thin (o1 m) deposits of aeolian silt are the parent materi- als for some of the soils on the limestone (Pigott & Pi- gott 1963; Bullock 1971; Furness & King 1972; Catt 1977; Vincent & Lee 1981). Bullock (1971), using mi- neralogical analyses, established that the silt deposits differed from underlying tills and were not weathered tills. On the limestone around Morecambe Bay, Vin- cent & Lee (1981) employed a variety of techniques DOI 10.1111/j.1502-3885.2010.00172.x r 2010 The Authors, Journal compilation r 2010 The Boreas Collegium