), AB(Centre Eau Terre Environnement, Institut National de la Recherche Scientifique, Quebec-City, Québec G1K 9A9, Canada), AC(Geological Survey of Finland, FI-02151 Espoo, Finland), AD(Indiana University, Department of Geological Sciences, 1001 East 10th Street, Bloomington, IN 47405-1405, USA)Varve, Varve formation, Varve composition, Varve types (clastic varves, biogenic varves, endogenic varves), Varve counting, Calendar-year dating, Varve chronology, Human impact, Environmental variations, Climate reconstruction Downcore counting of laminations in varved sediments offers a direct and incremental dating technique for high-resolution climatic and environmental archives with at least annual and sometimes even seasonal resolution.
The pioneering definition of varves by De Geer (1912) had been restricted to rhythmically deposited proglacial clays.
We are the first group to undertake this work , and our ongoing research focusses on deposits that accumulated in Scotland where ice-dammed lakes were formed by the advance of glacier ice during the Loch Lomond or Younger Dryas Stadial (c.
12.9-11.5 ka BP), the last occasion when glaciers existed in the British Isles.
Varves are amongst the smallest-scale events recognised in stratigraphy.
An annual layer can be highly visible because the particles washed into the layer in the spring when there is greater flow strength are much coarser than those deposited later in the year. As with tree rings, errors may arise in a chronology based on varve counting, through occasional missing varves in poor years for deposition, occasional double (or even triple) varves in other years and mistakes in cross-correlating varve ...
Although records of varved sediments have been reported from sites in Britain, and a few examined quite closely, very feww robust varve chronologies have ever been developed for the period 16 to 8 ka BP.To undertake this work we combine comprehensive fieldwork using industrial-scale coring rigs alongside detailed analysis of sediments using: thin section micromorphology, micro-xrf core scanning, palaeoecology, grain size analysis, and Electron microscopy.Using these techniques, the CQR team able to identify, define and count annual sediment layers with very high precision, and to cross-validate the results obtained by different analysts.Subsequent to deposition of topmost laminae, the physical preservation of the accumulating varved sequence requires the sustained absence of sediment mixing, for example via wave action or macrobenthic bioturbation.Individual (sub)laminae in varved lake sediments typically express contrasting colours, always differ in terms of their organic, chemical and/or mineralogical compositions, and often also differ with regard to grain-size.
A varve is an annual layer of sediment or sedimentary rock.