Structures deforming Llandovery turbidites of the Gala Group in the Southern Uplands
terrane are spectacularly exposed in the Berwickshire coastal section, southeastern Scotland. The
upward-facing, upright to NW-vergent folds and associated structures appear to record a single
regional phase of subhorizontal NW–SE contractional deformation, with a steeply dipping direction
of bulk finite extension. These structures are markedly different from those developed in rocks correlated
with the Upper Llandovery Hawick Group exposed some 5 km to the south in the
Eyemouth–Burnmouth coastal section. Here a highly domainal system of sinistral transpressional
strain occurs, with zones of steeply plunging curvilinear folds, clockwise cleavage transection and
bedding-parallel sinistral detachment faults. The markedly different bulk strain patterns in the
Berwickshire coastal sections are thought to reflect the regionally diachronous nature of transpressional
deformation in the Southern Uplands terrane. There are striking similarities in the structures
recognized in the Berwickshire coastal sections and those developed in stratigraphically equivalent
units along strike in southwestern Scotland and Northern Ireland. This confirms the lateral structural
continuity and correlation of tracts and tract boundaries along the entire length of the Southern
Uplands terrane. The regional structure suggests that a phase of top-to-the-NW backthrusting and
backfolding associated with the southern margin of the Gala Group outcrop marks the transition
from orthogonal contraction to sinistral transpression in the Southern Upland thrust wedge during
late Llandovery times.