Tectonostratigraphy of the Southern Belt of the Southern Uplands

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Abstract
Synopsis: A revised stratigraphy is proposed for the Southern Belt of the Southern Uplands. The Southern Belt (Riccarton Group) comprises all rocks of Wenlock age and is divided into two formations — the Ross Formation and the Raeberry Castle Formation which can be recognised throughout the Southern Uplands. The Ross Formation of Cyrtograptus centrifugus to lower Monograptus riccartonensis Zone age comprises mainly classical turbidites and is everywhere tectonically fragmented/highly imbricated. The Raeberry Castle Formation of upper M. riccartonensis to C. lundgreni Zone age comprises diverse turbidite facies associations including channelised conglomerates containing limestone boulders and in the Kirkcudbright area comprises three fault-bounded, but internally coherent, units. The high quality of new biostratigraphic data obtained permits correlation of turbidite sequences across major strike faults between separate tectonic units for the first time in the Southern Uplands. The principal tectonic units identified probably correspond to packets of trench sediment which were sequentially accreted to the northwest margin of Iapetus during subduction during the mid-Silurian.