C-14 DATING OF LAMINATED SEDIMENTS FROM LOCH-NESS, SCOTLAND

Radiometric and AMS radiocarbon dating of a 6-m sediment core from Loc h Ness, Scotland, indicates that it represents perhaps the very end of the Late Pleistocene, and the first ca. 7500 yr of the Holocene. Coun ts of laminations observed in the Holocene section of the core suggest that they are present in sufficient number to constitute annual lamin ations (varves), an hypothesis consistent with the pollen record, whic h contains a sequence of zones representative of the Early, Middle and part of the Late Holocene regional vegetation history. On the basis o f BSEM and X-ray studies of sediments, and modern seston trap data, th e laminations are believed to be produced by winter floods, which intr oduce increased silt loading into the Loch. Sediment for the rest of t he year is mostly composed of clay-sized material. This hypothesis is being further tested, however, by continuing sedimentological and micr ofossil studies. Time-depth relations for the core based on calibrated C-14 dates and lamination counts, respectively, illustrate the close correspondence between the two sets of data. The latter are therefore now being used to develop a varve chronology for the Holocene for Loch Ness. This will then in turn be used for further chronological studie s, and for investigations of palaeoclimatic variations over the easter n North Atlantic, to which the signal of lamination thickness in the s ediments is thought to be particularly sensitive. They may also eventu ally be used for calibration studies, employing C-14 dating of specifi c carbon compounds, or groups of compounds extracted from the sediment using modern organic geochemical methods.