CITATION ERIBOLL SITE OF SPECIAL SCIENTIFIC INTEREST Highland (Sutherland) Site code: 612 NATIONAL GRID REFERENCE: NC 445570, NC 435568 (Lochan an Druim) OS 1:50,000 SHEET NO: Landranger Series 9 1:25,000 SHEET NO: Explorer Series 446, 447 AREA: 1779.53 hectares NOTIFIED NATURAL FEATURES Geological Stratigraphy: Cambrian Structural and metamorphic geology: Moine Quaternary geology and geomorphology: Quaternary of Scotland Biological Upland habitats: Dryas heath Woodlands: Upland birch woodland Fens: Open water transition fen DESCRIPTION Eriboll Site of Special Scientific Interest (SSSI) is located in the north of Sutherland, 11km southeast of Durness. This is a two part site. The main part of the site has been notified for the nationally important Cambrian and Moine geology, woodland and heathland. The smaller part of the site at Lochan an Druim has been notified for the nationally important Quaternary sediments and fen vegetation. Cambrian (geology) Internationally important features of the northwest Highland Cambrian rock sequence (around 500 million years old) are well exposed, particularly around An t-Sron. The rocks here include false-bedded quartzite, pipe rock, Fucoid beds and Salterella grit, overlain by Durness limestone. The Fucoid beds and Salterella grit contain a range of fossils including olenellid trilobites which show that the rocks were formed during the Lower Cambrian period (ca.542-513 million years ago). The transitions between the various rock types contribute to our understanding of the local environment during the Cambrian period. Moine (geology) Eriboll SSSI includes the most important section of the Moine Thrust Zone, a feature that has significantly contributed to the scientific understanding of geological processes. There are internationally important exposures of the geological structures that were formed during continental collision and mountain building events around 430 million years ago. The crags on Ben Arnaboll contain excellent exposures of the Arnaboll Thrust, one of the major thrust faults in the Moine Thrust Zone. At Heilam, there are magnificent exposures of Cambrian and Ordovician rocks (around 500 million years old) that are cut by numerous small thrusts. These thrusts produce an upright stack of rock slices known as an imbricate structure. The significance of imbricate structures and the nature and magnitude of overthrusting were first appreciated here. This brought about major advances in the study of mountain building processes. Quaternary of Scotland (geology) Lochan an Druim is the only place where detailed evidence has been found of the vegetation history of the extreme northwest of Scotland during the Devensian late-glacial and Holocene (part of the Quaternary geological period). It is a key part of the national network of such sites. The clay and mud at the bottom of Lochan an Druim are about 9m thick. The pollen and plant macrofossils within these layers of sediment provide a record of environmental conditions and vegetation development in the area during the 14,500 years since the end of the last ice sheet glaciation. During the Holocene (the last 11,500 years), birch and hazel woodland developed in the area, but oak did not extend this far north, and pine was probably only locally present. Dryas heath The calcareous soil that has formed near outcrops of limestone has created a suitable environment for Dryas heath. Calcareous soil is unusual in Sutherland because there is very little limestone here. There is exceptional development of a very local type of heath vegetation that is dominated by two nationally scarce species: mountain avens Dryas octopetala and rock sedge Carex rupestris. This is considered the finest example of this type of heath in the Highlands. Herb-rich grasslands dominated by Agrostis/Festuca grasses are also commonly found in these areas. Upland birch woodland The woodland at Arnaboll contains predominantly birch Betula pubescens and rowan Sorbus aucuparia. Locally enriched areas with calcareous flushes support hazel Corylus avellana and a diverse ground flora. The flushes themselves contain remote sedge C. remota and the uncommon Mackay’s horsetail Equisetum x trachyodon. Open water transition fen Lochan an Druim fen is of particular interest because fens that are fed by calcium-rich water are unusual in northwest Sutherland. Species found in this community include greater tussock-sedge C. paniculata and mare’s-tail Hippuris vulgaris. Hairy sedge C. hirta which is very uncommon in north Scotland is also found here. NOTIFICATION HISTORY First notified under the 1949 Act: 1963 and 1975 Re-notified under the 1981 Act: 17 March 1987 with a 1ha net increase in area Notification reviewed under the 2004 Act: 19 August 2010 REMARKS Measured area of site corrected from 1770ha. .