Evolution of the Northern Belt, Southern Uplands: implications for the Southern Uplands controversy

Abstract

Conodont and graptolite dating provide a high resolution biostratigraphical framework for correlation across the Southern Upland Fault. The establishment of an early Caradoc age for the red chert and volcanic sequences within the Northern Belt of the Southern Uplands confounds the accretionary prism model. and our data support the view that following the obduction of the Ballantrae ophiolite, fan complexes prograded southeastwards across a narrow, fault-bounded shelf into the deep basin of the Northern Belt. The fan complexes were initiated by uplift in the hinterland, caused by the intrusion of plutons into the Midland Valley Terrane. Sedimentation was controlled by regional extension, subsidence and eustasy through the Llanvirn and Caradoc. Basic lavas, with attenuated within-plate geochemical signatures, were erupted during the early Caradoc peak of extension and may have just post-dated the initiation of southwards subduction beneath the Lake District.