Howarth, RJ; (1971) The Portaskaig Tillite succession (Dalradian) of Co. Donegal. Proceedings of the Royal Irish Academy , 71 (1) pp. 1-35.

Text Portaskaig_Tillite_succession_of_Co_Donegal.pdf - Published Version Access restricted to UCL open access staff Download (9MB)

Abstract

The (? Eocambrian) succession of metasediments includes the Glencolumbkille Dolomite, Portaskaig Tillite (Boulder Bed of earlier literature), Kiltyfanned Schist, and Slieve Tooey Quartzite, and is particularly well exposed and complete at Glencolumbkille, Kiltyfanned and Fanad in Co. Donegal. Following serious questioning of the origin of late Pre-Cambrian till-like rocks elsewhere, detailed re-examination of the succession, and of the Portaskaig Tillite in particular, suggests that this formation originated from the subaerial movement of supraglacial flow tills into a high-energy beach, or shallow marine environment. Comparison with similar deposits forming at the present time in Vestspitsbergen (Boulton 1967, 1968) accounts for 22 out of 24 of the principal features of the Portaskaig Tillite. Systematic variation of the mixtite matrix composition with stratigraphic height is confirmed by 63 modal analyses and 48 X-ray fluoresence analyses for 21 elements. The source area was probably a granitic-metamorphic basement complex overlain by blanket carbonates and quartzose sandstones, possibly lying to the south-east of the basin of deposition.

Download activity - last month

Export as CSVXMLJSON

Download activity - last 12 months

Export as JSONCSVXML

Downloads by country - last 12 months

Export as CSVXMLJSON

Archive Staff Only

View Item