Millenderdale

Also within

Ayrshire and Arran County

Condition (NatureScot)

Geology & landscape

Geological Period: Ordovician · Rock Type: Gabbro

Landscape processes: Volcanic / Igneous

Description

Millenderdale Millenderdale comprises two adjacent areas of rock outcrops some seven kilometres south of the town of Girvan. These outcrops reveal geological processes occurring during the Ordovician period. The sites contains the Ballantrae Complex, of Ordovician age, which consists of three belts of pillow lavas and associated sediments, separated from each other by ultramafic intrusive rocks. The Complex shows many of the features of an obducted ophiolite although geochemical studies indicate that the various igneous rocks were generated in a variety of tectonic settings and have since been tectonically juxtaposed. Beerbachite dykes intruded into foliated gabbro can be seen exposed in a series of small knolls 500m to the east of Millenderdale Farm. Although the dykes usually cross-cut the foliation, in places the foliation swings into parallelism with the dykes suggesting that the gabbros were still hot and plastic at the time of dyke injection. The exposures have been interpreted as a sheeted dyke complex although the proportion of dykes to gabbro is much lower than that found in more recent ophiolite complexes. For this reason the precise significance of Millenderdale dykes remains open to debate.