The stratigraphical setting of the Cairnsmore of Fleet Pluton, Galloway

Abstract

Synopsis The granitic pluton of Cairnsmore of Fleet was intruded into the Moffat Shales (Caradoc-Fronian) and an overlying flysch facies. The flysch is divisible into two formations: the Craignell Formation, in the NW of the area, and the Knockeans Formation, to the SE. Within the Craignell Formation, an evolution of greywacke facies from basic through lithic to silicic is recognized, the base being diachronous from Idwian in the SE upwards to early Fronian in the NW. The Knockeans Formation, deduced to be the youngest unit, completes the evolutionary sequence of the greywackes from basic to a silicic facies, and is correlated with the Hawick Group (Telychian or later). The anomalous NW encroachment of flysch over pelagic facies may relate to a sedimentary source within a ridge located along the Iapetus oceanic suture.

The Northern Belt of the Longford-Down Inlier, Ireland and Southern Uplands, Scotland: an Ordovician back-arc basin

“…Metamorphic detritus is not particularly abundant in any of these facies at this locality, but in the Cairnsmore area ( Fig. 1) such detritus is common in the IP equivalent and even more so in succeeding greywackes (of the Craignell Formation Silicic Division) which contain commensurately less granitic detritus (Cook & Weir 1980). Together with the PP equivalent, a trend towards increasing compositional maturity stratigraphically upward and to the SE is evident in this latter area.…”

“…Inferred source directions for the IP equivalent and Craignell Formation Silicic Division in the Cairnsmore area are somewhat ambiguous, Cook & Weir (1980) arguing that the northward thinning of both indicates a southerly source although a northwesterly source is indicated in their palaeogeographic reconstruction (their fig. 4).…”

Refined model of incremental emplacement based on structural evidence from the granodioritic Newry igneous complex, Northern Ireland

“…It is now recognized that many intrusions were emplaced incrementally via distinct magma pulses (Richey, 1927;Harry and Richey, 1963;Cook and Weir, 1980;Pitcher, 1997;Hecht and Vigneresse, 1999;Kryza et al, 2014;Anderson et al, 2016). Much of the compositional varia tion observed in such intrusions will not have been produced in situ and instead relates to pro cesses operating within a source region or inter mediate staging chamber (Pitcher, 1997;Cole man et al, 2004;Lipman, 2007;Miller, 2008;Farina et al, 2012;Anderson et al, 2016).…”