Late Dinantian (Lower Carboniferous) platform carbonate stratigraphy of the Buttevant area North Co. Cork, Ireland

Abstract

A thick sequence of late Dinantian (Asbian±Brigantian) carbonates crop out in the Buttevant area, North Co. Cork, Ireland. A mud-mound unit of early Asbian age (the Hazelwood Formation) is the oldest unit described in this work. This formation is partly laterally equivalent to, and is overlain by, over 500 m of bedded platform carbonates which belong to the Ballyclogh and Liscarroll Limestone Formations. Four new lithostratigraphic units are described within the platform carbonates: (i) the early Asbian Cecilstown Member and (ii) the late Asbian Dromdowney Member in the Ballyclogh Limestone Formation; (iii) the Brigantian Templemary Member and (iv) the Coolbane Member in the Liscarroll Limestone Formation.The Cecilstown Member consists of cherty packstones and wackestones that are inferred to have been deposited below fair-weather wavebase. This unit overlies and is laterally equivalent to the mud-mound build-up facies of the Hazelwood Formation. The Dromdowney Member is typi®ed by cyclic-bedded kamaenid-rich limestones possessing shell bands, capped by palaeokarst surfaces, with alveolar textures below and shales above these surfaces. The carbonates of this unit were deposited at or just below fair-weather wavebase, the top of each cycle culminated in subaerial emergence. The Templemary Member consists of cyclic alternations of subtidal crinoidal limestones capped by subtidal lagoonal crinoidpoor, peloidal limestones possessing coral thickets. Intraclastic cherty packstones and wackestones characterize the Coolbane Member, which is inferred to have been deposited below fair-weather wavebase but above storm wavebase.The early Asbian Cecilstown Member has a relatively sparse micro-and macrofauna, typi®ed by scattered Siphonodendron thickets, archaediscids at angulatus stage and common Vissariotaxis. Conversely, macro-and microfauna is abundant in the late Asbian Dromdowney Member. Typical late Asbian macrofossils include the coral Dibunophyllum bipartitum and the brachiopod Davidsonina septosa. The base of the late Asbian (Cf6g Subzone) is recognized by the ®rst appearance of the foraminifers Cribrostomum lecompteii, Koskinobigenerina and the alga Ungdarella. The Cf6g Subzone can be subdivided into two biostratigraphic divisions, Cf6g1 and Cf6g2, that can be correlated throughout Ireland. Relatively common gigantoproductid brachiopods and the coral Lonsdaleia duplicata occur in the Brigantian units. The base of the Brigantian stage (Cf6d Subzone) is marked by an increase in the abundance of stellate archaediscids, the presence of Saccamminopsis-rich horizons, Loeblichia paraammonoides, Howchinia bradyana and the rarity of Koninckopora species.Changes in facies at the Cecilstown/Dromdowney Member and the Ballyclogh/Liscarroll Formation boundaries coincide closely with the changes in fossil assemblages that correspond to the early/late Asbian and the Asbian/Brigantian boundaries. These facies changes are believed to re¯ect major changes in relative sea-level on the Irish platforms. The sealevel variations that are i...

Stratigraphy of upper Viséan carbonate platform rocks in the Carlow area, southeast Ireland

“…This fauna is representative of coral assemblage zone H of Mitchell (1989) and Jones and , and can be equated with the RC8 Rugose Coral Zone of Poty (1985), Poty in Conil et al (1991). It is comparable with Brigantian coral assemblages recorded in the north Cork region of southern Ireland (Liscarrol Formation; Gallagher and Somerville 1997) and in the Burren, western Ireland (Slievenaglasha Formation; Gallagher and Somerville 1997).…”

“…This late Asbian assemblage is representative of coral assemblage zone G of Mitchell (1989) and Jones and , and can be equated with the RC7 Rugose Coral Subzone of Poty (1985), and Poty in Conil et al (1991). It is comparable with late Asbian coral assemblages recorded from the Dromkeen Limestone Formation in the Limerick area , from the Ballyclogh Formation in the north Cork region of southern Ireland (Gallagher and Somerville 1997), and from the Mullaghfin Formation, Kingscourt Outlier (Strogen et al 1995).…”

Icehouse world sea‐level behaviour and resulting stratal patterns in late Visean (Mississippian) carbonate platforms: integration of numerical forward modelling and outcrop studies

“…The severity of this marine flooding event and its proximity to the onset of the late Palaeozoic glaciation serve to qualify it as a candidate locus for a Mississippian GSSP (Riley, 1999). Gallagher & Somerville (1997) suggest that the Asbian–Brigantian boundary is also suitable for the international correlation and division of the Mississippian. As expected, these flooding events have a prominent lithological expression and correspond with marked lithostratigraphic changes, both in the platform interior (e.g.…”

“…exposure surface development) and in the light of considerable advances in biostratigraphy, the sequence boundaries closely coincide with those of Ramsbottom (1977). The mid‐Asbian and Asbian–Brigantian boundaries have also recently been proposed as sequence boundaries in the Buttevant and Burren areas of southern Ireland by Gallagher & Somerville (1997). While the simple model invoked here appears to be most appropriate for the Asbian–early Brigantian, it is known from studies of Pennsylvanian cycles (Heckel, 1977; Klein 1994) and estimates of ice‐sheet volume (Crowley & Baum, 1991) that the amplitude of glacio‐eustatic sea‐level oscillations increased through the Carboniferous.…”

Basaltic maar-diatreme volcanism in the Lower Carboniferous of the Limerick Basin (SW Ireland)

“…The overlying lithofacies 4 is typically interbedded with fines-poor material. Here, lapilli are sparse within the wackestones proposed by Wood (1957), Riding (1975) and Gallagher and Somerville (2003) for foram and algae (taxa Draffa-690 nia and Girvanella) observed in the Lough Gur beds by 691 . The lower depth limit is based on the lack of ooids in the Limerick upper Waulsortian that have been observed in other areas where this Formation has reached depths <120 m (Lees and Miller 1985), and also reflects the underlying carbonate bathymetry seen in Fig.…”