The south-east limit of the Moffat Shales in the upper Ettrick Valley region, Selkirkshire

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Abstract
Synopsis: The south-east limit of the Moffat Shale inliers in the Llandovery greywackes of the Moffat area is shown to be a major NE.-SW. dislocation, the Ettrick Valley Fault. This thrusts the tightly folded Moffat terrain over younger ( turriculatus and crispus Zones) greywackes to the south-east which dip, and young, consistently north-west. Contrary to previous opinion (Walton 1963) there is no evidence, in the Moffat area, for any south-eastward passage of the Birkhill Shales into greywackes. The most south-eastern exposures of the Moffat Shales, and particularly the Birkhill Shales, in the Upper Ettrick Valley, show the same thicknesses and lithologies as at the typical locality of Dobb’s Linn. The structure of the Upper Ettrick Valley is shown to be of an imbricate type caused by the shearing out of inverted limbs of isoclines, thus causing the repetition of Moffat Shales across the strike of greywackes which dip and young consistently north-west. High angle reverse faults in the greywackes SE. of the Ettrick Valley Fault may offset the north-westerly younging and cause the succession to become younger south-east towards the Hawick Rocks.

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