Early to mid‐Viséan shallow water platform buildups, north Co. Dublin, Ireland

Abstract

A number of carbonate buildups in north Co. Dublin, long assigned to the late Visean (Asbian), are shown on the basis of coral, foraminifera1 and algal evidence to be early to mid-VisCan (late Chadian to Holkerian) in age. They are equivalent in age to beds ranging from the upper part o f the Lane Formation to the top of the Holmpatrick Formation.The buildups are poorly exposed and relatively small, probably only a few tens of metres across at most. Buildup sediments are massive to crudely bedded and dominated by peloidal, clotted and dense uniform micrites displaying lime mudstone and bioclastic wackestone textures. Dasycladacean algae are cotiimon in the buildups and cryptalgal fabrics are locally important. Cavities in the buildups are generally small ( < 5 cm) and lined with inclusion-rich radiaxial calcite cements. Micritization of bioclasts and cements is ubiquitous. Enclosing off-buildup limestones are skeletal and intraclastic grainstones possessing sedimentary structures indicative of deposition in moderate to high energy environments. Fossil and petrographic evidence from the buildups also indicate a shallow water origin for the north Co. Dublin buildups.Compared with the slightly older Tournaisian (Courceyan to early Chadian) Waulsortian buildups which developed extensively in the Dublin Basin, these younger platform buildups are smaller and more isolated and possess a diverse suite o f algal components and cryptalgal fabrics. Nevertheless, components in the north Co. Dublin buildups most closely resemble the shallowest phase D Waulsortian buildups, particularly in the presence of abundant peloids and micri t ized cements.The north Co. Dublin buildups developed on a carbonate platform (the Milverton Platform), adjacent to the Dublin Basin, whereas the Waulsortian developed in a deeper ramp setting. Following the demise of the Waulsortian in early Chadian time carbonate buildups established themselves on the shallow platforms. It is suggested that the microbial communities responsible for these buildups may have 'evolved' from older phase D Waulsortian communities and that the north Co. Dublin platform buildups represent the shallow water end of a spectrum of Visean buildups.

Biostratigraphic zonation and correlation of Mississippian rocks in Western Europe: some case studies in the late Viséan/Serpukhovian

“…Moreover, although there are several studies in which algal genera are occasionally documented (e.g. Hallett 1971;Conil et al 1980;Somerville and Strank 1984;Somerville et al 1992aSomerville et al , 1992bSomerville et al , 1992cJohnson and Nudds 1996;Gallagher and Somerville 1997), they do not provide any additional data on their biostratigraphical range. Of special interest are the works of Mamet and Roux (1974, 1975a, 1975b, 1977 and Mamet (1991), who revised many Carboniferous calcareous algal genera, and described new genera and species, as well as documenting numerous stratigraphic ranges and palaeogeographic distribution of algal taxa.…”

“…This was recognized in cycles in the northern part of the platform (Burren; Figure 2), whereas at the southern end (south Cork), the cycles and total thickness of the sequence thicken, and the lower part of each cycle is much better developed (Gallagher and Somerville 2003). Conil and Lys (1964, 1965, 1966; Conil and Lees (1974);Conil (1976Conil ( , 1980; Conil and Naum (1977); Vachard (1977Vachard ( , 1988; Conil et al (1980Conil et al ( , 1986Fewtrell et al (1981);Strank (1981); Ramsbottom (1981b); Brenckle et al (1987); Loeblich and Tappan (1988);Vachard (1988); Strogen et al (1990Strogen et al ( , 1995; Gallagher (1992); Somerville et al (1992aSomerville et al ( , 1992bSomerville et al ( , 1992c; Somerville (1997, 2003), Somerville (2004, 2005a) (14), twice as many as in the Arundian (7) and Serpukhovian (7). The Asbian records the second highest level (11 genera).…”

Mississippian (Early Carboniferous) stromatolite mounds in a fore-reef slope setting, Laibin, Guangxi, South China

“…It is only just after the beginning of the early Viséan stage that there was a resurgence of skeletal metazoan in the reef biome (Adams 1984;Dix and James 1987;Bancroft et al 1988;Webb 1989Webb , 1998Webb , 1999Webb , 2005Horbury 1992;Mundy 1994;Ahr and Stanton 1994). Mississippian carbonate buildups are known in eastern Australia (Jull 1968;Webb 1989Webb , 1998Webb , 1999Shen 2002;Shen andWebb 2005, 2008), western Newfoundland of Canada (Dix and James 1987), Europe (Adams 1984;Bancroft et al 1988;Horbury 1992;Lauwers 1992;Somerville et al 1992Somerville et al , 1996Somerville 2003;Pickard 1992Pickard , 1996Mundy 1994;Bridges et al 1995;Kirkham 2005;Aretz and Chevalier 2007), North Africa (Pareyn 1959;Bourque et al 1995;Madi et al 1996); northern Arkansas, New Mexico, Virginia and Texas of USA (Webb 1987;Ahr 1989;Christopher 1990;Ahr and Stanton 1994), Urals of Russia (Antoshkina 1998;Skompski et al 2001), and Japan (Ota 1968;…”

A revised Mississippian lithostratigraphy of County Galway (western Ireland) with an analysis of carbonate lithofacies, biostratigraphy, depositional environments and palaeogeographic reconstructions utilising new borehole data

“…They are also similar to the Asbian mounds of Co. Sligo (Somerville, 2003;Somerville et al, 2009). They have affinity with shelf margin mounds described from the northern margin of the Dublin Basin near Loughshinny (Somerville et al, 1992;Somerville, 2003) which have locally developed boundstone frameworks.…”