Hareheugh Craigs

Also within

Berwickshire County

Condition (NatureScot)

Geology & landscape

Geological Period: Carboniferous · Rock Type: Basalt

Landscape processes: Volcanic / Igneous

Description

HAREHEUGH CRAIGS Hareheugh Craigs SSSI lies 5 km south east of Gordon, and 7 km north west of Kelso, in Berwickshire, and forms a prominent feature in the local agricultural landscape. The site comprises the remains of a volcanic plug that is of geological interest due to the origin of the rock, the conditions in which the rock formed and its mineral composition. Volcanic igneous rocks and associated intrusions occur near the base of the Carboniferous System in both the Midland Valley of Scotland and in the Scottish Borders. Volcanicity in the Borders appears to have been related to the early development of the Northumberland Basin, and was therefore independent of the Midland Valley volcanism, which was occurring at the same time. In addition to the lavas in Berwickshire, known traditionally as the ‘Kelso Traps’, there are a number of intrusions, some of which are of rock types rarely represented in the lava sequences and are of unusual composition. Hareheugh Craigs exposes a fine example of such an intrusion, whose interest is enhanced because it is composite in nature, with two principal types of basalt present. Such intrusions give insight into the availability of magma with time, and the composite character can yield information on the processes which took place in magma chambers and the mechanisms by which intrusion took place. Although they do not constitute notified features, Hareheugh Craigs is of local importance for the flora and fauna present. The thin soils and base-rich rocks beneath support an assemblage of plants that is uncommon across the Borders. The assemblage includes species-rich grassland on the south-facing slopes, where maiden pink Dianthus deltoides, common rock-rose Helianthemum nummularium, meadow saxifrage Saxifraga granulata and moonwort Botrychium lunaria can be found. Species-rich grassland communities on the north-facing slopes include mountain pansy Viola lutea, with ferns, lichens, mosses and woodland plants present on rock outcrops and ledges. The locally important butterfly, northern brown argus Aricia artaxerxes is also found regularly at the site.

Species mentioned