The geology of Castle Rock, Johnston Terrace, Edinburgh

This report describes the geology of the section of Castle Rock, Johnston Terrace, Edinburgh. Castle Rock is a classic ‘crag-and-tail’ feature, of which Edinburgh Castle sits on the ‘crag’ whilst the Royal Mile has been built on the ‘tail’. The site comprises basalt as part of a suite of igneous rocks related to Arthur’s Seat Volcano and a series of strata sandstone/calcareous mudstone strata of the Ballagan Formation (Lower Carboniferous). The section studied displays the contact between the basalt on which Edinburgh Castle sits and the sandstone/mudstone strata on which the Royal Mile rests. The report particularly highlights the extent to which this contact and the adjacent sedimentary strata are faulted.