Late Triassic miospores from Gribun, western Mull

Abstract

The presence of the “Rhaetic”, now the Penarth Group ([Warrington et al. 1980][1]), in the Gribun district of western Mull was established in 1920 ( Summ. Prog. Geol. Surv. for 1920 ; Summ. Prog. Geol. Surv. for 1921, p. 35 ) following the discovery of a bivalve fauna including Rhaetavicula ( Pteria ) contorta (Portlock) and Chlamys ( Pecten ) valoniensis (Defrance) in beds exposed principally in the vicinity of Balmeanach Farm [NM 448 330]. The Penarth Group is approximately 12 m thick in the Gribun area (Lee and Bailey 1925) and comprises dark grey sandy limestones and calcareous sandstones and siltstones with some beds of yellow calcareous sandstone and dark grey and black shales. The principal section is to the east-north-east of Balmeanach Farm in the course of Allt na Teangaidh, above its confluence with the Allt Ruadh, where up to 9 m of the sequence is seen in discontinuous exposures. The base and top of the group are not exposed. The beds were assigned to the “zone of Pteria contorta” on the basis of the bivalve fauna recovered largely from exposures in that section (Lee and Bailey, op. cit.; Bailey and Anderson 1925; Lee and Pringle 1932). No further palaeontological work on the Penarth Group of Gribun has been published and the study reported here was carried out with the object of enhancing the palaeontological documentation and the biostratigraphic interpretation of those beds. Palynology Samples were collected by one of us (J.E.P.) from exposures of the Penarth Group in Allt na Teangaidh (Fig. 1) and were processed by the British . . . [1]: #ref-10