Abstract

240 samples from Appin and Argyll Group carbonate rock units of the Dalradian of northeast Scotland have been analysed for 10 major oxides and 14 to 19 trace elements in order to classify and correlate them using geochemistry. The carbonate rocks are chiefly limestones, with some dolostones. Rocks with 0.38 > MgO/CaO > 0.03 are classed as dolomitic limestones; those with MgO/CaO > 0.38 are classed as dolostones. The data have approximately lognormal distributions at a high level of significance except for CaO, MgO and Sr. CaO and Sr have negatively skewed distributions. Median values for groups of sample analyses plotted on normalized multi-element variation diagrams and a nonlinear mapping (NLM) algorithm have been used to classify groups of samples. In the Appin Group, multi-element diagram patterns are distinctive for each unit, allowing correlations to be made. Though distinctive compositions do occur locally in Argyll Group carbonate rocks, correlation on a regional scale is not possible. The plot of NLM coordinates for suites of samples is consistent with the results from the spider diagrams; suites of Appin Group samples cluster closely whereas there is wide spread in samples from the Argyll Group. In several areas, most notably at Sandend Bay, the data have allowed reinterpretation of the stratigraphy. The data are consistent with other geological data in suggesting that crustal conditions were relatively stable during the deposition of the Appin Group, but not during the deposition of the Argyll Group.

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