High Resolution Arctic Lake Sediments
We expect that all the sediments we recover from the lakes will be of Late Holocene age. However, absolute dating of sediments from High Arctic lakes is problematical. Organic carbon levels are low, contamination by Tertiary wood is possible and macrofossils are rare. We are explicitly addressing these problems, with a five-fold strategy for dating:1. Varve counting along multiple transects and in duplicated cores from each lake.
2. 210Pb and 137Cs dating of the uppermost sediments to confirm the annual nature of sedimentation and verify the sedimentation rates over the last 100-150 years based on varve counts.
3. Luminescence dating of sediments (optically stimulated and infra-red stimulated luminescence) in association with in situ studies of sediments from rivers and the water column of each lake, to investigate the level of bleaching in the present study. This effort is being undertaken in collaboration with the Luminescence Dating Laboratory in Aberystwyth.
4. AMS 14C dating, where reliable results seem possible (i.e. on microscopically-identified macrofossils)
5. Stratigraphic correlation of varve thickness records with melt data from the Agassiz & Devon Island ice cores, as summer temperatures provide similar controls on melting and sediment flux, leading to broadly similar time series. This relative dating technique will provide further confidence in the chronology established by other means.
These different approaches will provide some opportunity to cross-check and validate the sedimentary chronology. Once this is confidently known, we will embark on a detail studies of the paleomagnetic record in each core, to establish a secular paleomagnetic time series for each lake. In particular, we will examine inclination, declination and normalised intensity with depth in the cores. Additional mineral magnetic measurements of susceptibility, SIRM and ARM will be done to aid in correlations. The paleomagnetic parameters will provide a regional template which can then be used with other sedimentary records (where independent dating may not be extensive) to establish or confirm the chronology in those records.
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Climatology Lab | Department of Geosciences | University of Massachusetts
Last revised: 15 July 1998