Identifying sediment discontinuities and solving dating puzzles using monitoring and palaeolimnological records

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  • Xuhui Dong, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Environmental Change Research Centre, Department of Geography, University College London, London, UK
  • ,
  • Carl D. Sayer, Environmental Change Research Centre, Department of Geography, University College London, London, UK, United Kingdom
  • Helen Bennion, Environmental Change Research Centre, Department of Geography, University College London, London, UK, United Kingdom
  • Stephen C. Maberly, Lake Ecosystems Group, Centre for Ecology & Hydrology, Lancaster, UK, United Kingdom
  • Handong Yang, Environmental Change Research Centre, Department of Geography, University College London, London, UK, United Kingdom
  • Richard W. Battarbee, Environmental Change Research Centre, Department of Geography, University College London, London, UK, United Kingdom
Palaeolimnological studies should ideally be based upon continuous, undisturbed sediment sequences with reliable chronologies. However for some lake cores, these conditions are not met and palaeolimnologists are often faced with dating puzzles caused by sediment disturbances in the past. This study chooses Esthwaite Water from England to illustrate how to identify sedimentation discontinuities in lake cores and how chronologies can be established for imperfect cores by correlation of key sediment signatures in parallel core records and with long-term monitoring data (1945–2003). Replicated short cores (ESTH1, ESTH7, and ESTH8) were collected and subjected to loss-on-ignition, radiometric dating (210Pb, 137Cs, and 14C), particle size, trace metal, and fossil diatom analysis. Both a slumping and a hiatus event were detected in ESTH7 based on comparisons made between the cores and the long-term diatom data. Ordination analysis suggested that the slumped material in ESTH7 originated from sediment deposited around 1805–1880 AD. Further, it was inferred that the hiatus resulted in a loss of sediment deposited from 1870 to 1970 AD. Given the existence of three superior 14C dates in ESTH7, ESTH1 and ESTH7 were temporally correlated by multiple palaeolimnological proxies for age-depth model development. High variability in sedimentation rates was evident, but good agreement across the various palaeolimnological proxies indicated coherence in sediment processes within the coring area. Differences in sedimentation rates most likely resulted from the natural morphology of the lake basin. Our study suggests that caution is required in selecting suitable coring sites for palaeolimnological studies of small, relatively deep lakes and that proximity to steep slopes should be avoided wherever possible. Nevertheless, in some cases, comparisons between a range of contemporary and palaeolimnological records can be employed to diagnose sediment disturbances and establish a chronology.
Original languageEnglish
JournalFrontiers of Earth Science
Volume10
Issue4
Pages (from-to)621-633
Number of pages13
ISSN2095-0195
DOIs
Publication statusPublished - 2016

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