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Lundberg J.,Carleton University | Lord T.C.,Lower Winskill | Lord T.C.,Lancaster University | Murphy P.J.,University of Leeds
Geosphere | Year: 2010

We present 23 new thermal ionization mass spectrometric U-Th dates for Victoria Cave, North Yorkshire, UK. Victoria Cave underwent repeated glaciation during the late Pleistocene and contains one of the longest Quaternary cave sequences in Britain. The dates reveal that speleothem formation began beyond the range of the dating technique (before 600 ka). Finite reproducible dates of 490-9/+10 ka confi rm speleothem deposition during marine isotope stage (MIS) 13, the oldest date we know of for this part of Britain. Further speleothem formation was dated to MIS 11, MIS 9, MIS 7, and MIS 5. The results are the basis for a new chronology of Quaternary events for the cave and greatly enhance our understanding of the factors affecting the formation of the sedimentary sequence. Cyclical climatic and environmental change throughout the late Pleistocene triggered cyclical sedimentation events in the cave. All the interglacial periods show calcite deposition but with growth phases postdating the warmest events of MIS 11 and MIS 5e. The position of the cave halfway up the side of a glacial trough resulted in very distinctive sediment during the more extreme glacial maxima: ice-dammed lakes formed inside the cave and deposited varvelike clay rhythmites. The dates inferred for these deposits suggest that this locality underwent signifi cant glaciation during MIS 12, MIS 10, MIS 6, and MIS 2, and that the ice was warm based. The absence of rhythmites during MIS 8 suggests minimal ice cover at that time. This is the most complete record for glacial events in the region; it is the only site where successive glacial maxima can be identifi ed and dated. The record of large faunal remains indicates that the cave was open to the surface, only for relatively short times, during MIS 13, MIS 12, MIS 5e, the Late Glacial Interstadial, and parts of the Holocene. It is inferred that at other times the cave was closed because scree formation blocked the entrance. The record of vertebrate remains is therefore controlled by geomorphological processes. The deteriorating state of this unprotected site remains a cause for concern. © 2010 Geological Society of America. Source

Wilson P.,University of Ulster | Lord T.C.,Lower Winskill
Cave and Karst Science | Year: 2012

Contrasting rates of limestone dissolution to account for the development of limestone pedestals beneath erratic boulders at Norber, North Yorkshire, have been proposed. Most of these estimates were made prior to reliable dates being available for erratic emplacement and prior to detailed knowledge of the pattern of regional 'post-glacial' climate change. The erratics were deposited c. 18 ka BP, and for a substantial part of the ensuing c. 4 ka a climate of Arctic severity prevailed until the abrupt warming at 14.7 ka BP, marking the onset of the Lateglacial Interstadial. We propose that nivation (snowrelated) processes operated for much ofthat time, and again during the Younger Dryas Stadial (12.9 - 11.7 ka BP), and made a contribution to the lowering of the limestone surface by both mechanical and chemical action. Similar processes are likely to have operated for short periods on several occasions during the Holocene when, according to proxy records, climate deteriorated. We question previous views that dissolution occurred in an entirely temperate sub-regolith environment and/or was achieved solely by rainfall. © British Cave Research Association 2012. Source

Wilson P.,University of Ulster | Lord T.,Lower Winskill | Schnabel C.,Scottish Enterprise | Vincent P.J.,Lancaster University
Proceedings of the Yorkshire Geological Society | Year: 2013

Four gritstone outcrops around the summit rim of Ingleborough in the Yorkshire Dales, northern England, have yielded early to mid-Holocene cosmogenic 10Be surface exposure ages, ranging from 10.61 ± 0.53 ka to 6.84 ± 0.35 ka. Taken at face value, the ages indicate that the outcrops became exposed to cosmic radiation at different times and consequently were not necessarily exposed as a result of the same single process at each site. Erosion of overlying gritstone debris during periods of climatic deterioration, during construction of a stone rampart, and during rock-slope failure may have all contributed to the exposure ages of these surfaces. Some of the ages may be compound in that a component of their isotope signal was acquired prior to the complete removal of the former debris cover. Although interpretation of the data set involves some speculation, the ages and topographic context of the samples indicate that the processes and timing of mountain top erosion may vary at small spatial scales. © The Geological Society of London 2014. Source

Wilson P.,University of Ulster | Lord T.C.,Lower Winskill | Telfer M.W.,University of Plymouth | Barrows T.T.,University of Exeter | Vincent P.J.,Lancaster University
Geology Today | Year: 2013

The Craven Dales of North Yorkshire contain some of the finest examples of limestone geology and landscape in the UK. The extensive limestone pavements with their clints, grikes and other water-worn features, are a key attraction for both scientists and recreational visitors. Likewise the cave systems attract attention with their remarkable sediment accumulations, some of which are in excess of 500 000 years old and others contain the bones of mammals that are either extinct or no longer present in the British Isles. The glacial erratic boulders at Norber and the loessic sediments that, in places, mask the limestone have also provided stimulus for investigation. Summarized below are the findings of several recent studies that focussed on establishing the age of various features. Whilst the reports answer some long-standing questions, they also demonstrate that there is still much that can be learned about this seemingly familiar territory. © 2013 Blackwell Publishing Ltd, The Geologists' Association & The Geological Society of London. Source

Wilson P.,University of Ulster | Barrows T.T.,University of Exeter | Lord T.C.,Lower Winskill | Vincent P.J.,Lancaster University
Earth Surface Processes and Landforms | Year: 2012

Determination of the rate and total amount of limestone pavement surface lowering is a critical issue in developing models of regional landscape change in limestone terrain. Erratic-capped pedestals have frequently been used for this purpose but problems concerning definition and measurement of pedestal height, and the absence of a secure timeframe for erratic emplacement, have resulted in conflicting interpretations. We have used cosmogenic ( 36Cl) to establish the emplacement age of erratic boulders and the total amount of pavement surface lowering at sites in northwest England. Since erratic emplacement at 17.9ka the limestone pavement has been lowered by 22-45cm (average: 33±10cm), assuming lowering was continuous. Although indicating some spatial heterogeneity, the results contrast with earlier reported values based on the measurement of pedestal heights and inferred age for deglaciation. We consider that changes in climate and the character and duration of regolith covers to have been important influences in promoting surface lowering. It is argued that nivation (chemical and mechanical snow-related processes) associated with several cool/cold periods is likely to have played an important role in surface lowering. Complicating factors associated with surface lowering (thickness and longevity of snow and regolith covers) are identified but as yet cannot be quantified. © 2012 John Wiley & Sons, Ltd. Source

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