Turbidite geochemistry and provenance studies in the Southern Uplands of Scotland

Abstract

AbstractRegional lithogeochemical data from the Southern Uplands have been used to characterize a distinctive stratigraphy across this region. A suite of 840 point-counted and petrographically classified greywacke samples were used to establish chemical fingerprints for a series of greywacke-dominated lithostratigraphical units. These fingerprints were then used to evaluate a further 1455 greywacke samples collected throughout the Southern Uplands and Longford Down and enabled a series of strike-parallel geochemical tracts to be defined.Four principal geochemical groups are recognized, relating to cratonic- and volcanic-derived greywacke provenances and both carbonate-rich and hydrothermally altered greywackes. Volcanic-derived units display higher Ti, Fe, Mg, Ca, Na, Mn, Cr, Ga, Ni, Sr, V and Zn values than their cratonic counterparts, which, with the exception of the carbonate-rich Hawick Group, display higher Si, K, La, Nb, Rb, Th and Zr. Volcaniclastic greywackes display REE patterns dissimilar to typical post-Archean upper crust, but similar to their andesitic components, whereas cratonic groups have REE patterns close to that of upper crust. Systematic strike-parallel geochemical variation in the Southern Uplands is controlled by petrographical differences which directly reflect provenance, with individual lithostratigraphical units derived from variable mixtures of ophiolitic, calc-alkaline, acid-igneous, low-grade metamorphic and carbonate-rich detritus.