Abstract
AbstractThe Lough Muck Formation (Wenlock) is part of the Silurian succession of North Galway, western Ireland. The formation had originally been interpreted as a transitional sequence between shelf and basinal facies in the succession. Its three members (1, 2, and 3 of Laird and McKerrow 1970) were envisaged as representing deposits of the continental rise, slope, and shelf respectively. A subsequent interpretation suggested that the two upper members were of shallow marine origin and that the proposed major Wenlock regressive event was already extant by the time of deposition of Member 2. In this paper we examine Member 1 to ascertain its environment of deposition and thus refine the sea level curve for this element of the Silurian.Member 1 may be divided into five lithofacies A to E. Facies A comprises amalgamated sandstones with low‐angle cross‐stratification. Facies B consists of couplets of erosively based coquinas containing a low‐diversity parautochthonous fauna and graded, laminated sandstones. These couplets are interbedded with thin laminated siltstones. Facies C is characterized by parallel laminated siltstones and discontinuous, erosively based sandstones. Facies D consists of fossiliferous siltstone and Facies E of thin sandstones with low‐angle cross‐lamination. Facies A and B are interpreted as shoreline deposits based upon comparison with published descriptions of such deposits elsewhere. Facies, C, D, and E, lateral equivalents of the first two facies, are interpreted as deposits which accumulated further offshore. The presence of couplets consisting of a coquina and overlying laminated sandstone, and fossil distribution, the presence of amalgamated beds and low‐angle cross‐stratification suggest the influence of storms on this shallow‐water sequence. A palaeoreconstruction is proposed which envisages a shelf deepening to the southeast off a shoreline which had an approximately northeasterly orientation.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call