DALRADIAN  , in

geology, a series of metamorphic rocks, typically developed in the high ground which lies E. and S. of the Great Glen of Scotland . This was the old Celtic region of Dalradia, and in 1891 Sir A . Geikie proposed the name Dalradian as a convenient provisional designation for the complicated set of rocks to which it is difficult to assign a definite position in the stratigraphical sequence (Q.J.G.S . 47, p . 75): In Sir A . Geikie's words, " they consist in large proportion of altered sedimentary strata, now found in the form of mica-schist, graphite-schist, andalusite-schist, phyllite, schistose grit, greywacke and conglomerate, quartzite, limestone and other rocks, together with epidiorites, chlorite-schists, hornblende schists and other allied varieties, which probably mark sills, Sava-sheets or beds of tuff, intercalated among the sediments . The total thickness of this assemblage of rocks must be many thousand feet." The Dalradian series includes the " Eastern or Younger schists " of eastern Sutherland, Ross-shire and Inverness-shire—the Moine gneiss, &c.—as well as the metamorphosed sedimentary and eruptive rocks of the central, eastern and south-western Highlands . The series has been traced into the north-western counties of Ireland . The whole of the Dalradian complex has suffered intense crushing and thrusting . See PRE-CAMBRIAN; also J . B . Hill, Q.J.G.S., 1899, 55, and G .

Barrow, loc. cit., 1901, 57, and the Annual Reports and Summaries of Progress of the Geological Survey of the United Kingdom from 1893 onwards .