Controls on the evolution and demise of Lower Carboniferous carbonate platforms, northern margin of the Dublin Basin, Ireland

Abstract

Shallow water platform limestones of the Chadian-Asbian Milverton Group are restricted to the north-eastern part of the Lower Carboniferous (Dinantian) Dublin Basin. Here, they are confined to two granite-cored fault blocks, the Kentstown and Balbriggan Blocks, known to have been active during the late Dinantian. Three areas of platform sedimentation are delimited (the Kentstown, Drogheda and Milverton areas), although in reality they probably formed part of a single carbonate platform. Resedimented submarine breccias and calciturbidites (Fingal Group) composed of shallow water allochems and intraclasts sourced from the platform accumulated, along with terrigenous muds, in the surrounding basinal areas.Sedimentological evidence suggests that the Kentstown and Balbriggan Blocks possessed tilt-block geometries and developed during an episode of basin-wide extensional faulting in late Chadian time. Rotation of the blocks during extension resulted in the erosion of previously deposited sequences in footwall areas and concomitant drowning of distal hangingwall sequences. Antithetic faults on the northern part of the Balbriggan Block aided the preferential subsidence of the Drogheda area and accounts for the anomously thick sequence of late Chadian platform sediments present there. Continued subsidence andor sea-level rise in the late Chadian-early Arundian resulted in transgression of the Kentstown and Balbriggan Blocks; carbonate ramps developed on the hangingwall dip slopes and transgressed southward with time. Subsequent progradation and aggradation of shallow water sediments throughout the Arundian to Asbian led to the development of carbonate shelves. Several coarse conglomeratic intervals within the contemporaneous basinal sequences of the Fingal Group attest to periodic increases of sediment influx associated with the development of the shelves.Sedimentological processes controlled the development of the carbonate platforms on the hangingwall dip slopes of the Kentstown and Balbriggan Blocks, though periodic increases of sediment flux into the basinal areas may have been triggered by eustatic falls in sea level. In contrast, differential subsidence along the bounding faults of these blocks exerted a strong control on the margins of the late Dinantian shelves, maintaining relatively steep slopes and inhibiting the progradation of the shelves into the adjacent basins.Tectonically induced collapse and retreat of the platform margins occurred in the late Asbian-early Brigantian. Platform sediments are overlain by coarse-grained proximal basinal facies which fine upwards before passing into a thick shale sequence, indicating that by the late Brigantian carbonate production had almost stopped as the platforms were drowned.

The value of a combined approach: Innovative mineral exploration techniques in the Irish Zn-Pb orefield

“…The Tober Colleen Event began during the latest stages of Cruicetown Group deposition (during Supra-Waulsortian deposition) and was dominated by strong subsidence (rather than faulting). Previous tectonic interpretations of the Dublin Basin suggest that the Tournaisian was dominated by gentle subsidence and sagging, while most faults were produced as a result of Lower Viséan tectonism (Nolan, 1989;Strogen et al, 1990;Andrew, 1992;Pickard et al, 1992;Pickard et al, 1994;Strogen et al, 1995;Nagy et al, 2005).…”

Sedimentation in an actively tilting half‐graben: sedimentology and stratigraphy of Late Tournaisian–Viséan (Mississippian, Lower Carboniferous) carbonate rocks in south County Wexford, Ireland

“…Long-term tectonic control over facies development was a feature of those basins during the Late Chadian and Late Asbian, e.g. Dublin Basin (Nolan, 1989;Philcox, 1989;Pickard et al, 1994;Strogen et al, 1996) and the northern England basins (Gawthorpe,Fig. 9.…”

“…These basins are rooted in Caledonian structures, which were reactivated during the Lower Carboniferous (Ashton et al. , 1986; Phillips & Sevastopulo, 1986; Nolan, 1989; Pickard et al. , 1994; Strogen et al.…”

“…1) is one of several sedimentary basins, which formed during the Lower Carboniferous in Ireland (see Table 1 for definition of terms). These basins are rooted in Caledonian structures, which were reactivated during the Lower Carboniferous (Ashton et al, 1986;Phillips & Sevastopulo, 1986;Nolan, 1989;Pickard et al, 1994;Strogen et al, 1996). Lowe & Jacob (1989) observed crustal heterogeneity to the south of the Iapetus Suture (Fig.…”

Tectonic Influences on SE Asian Carbonate Systems and their Reservoir Development

“…Tectonics may directly influence these systems through plate tectonic movement, differential subsidence and faulting, and indirectly through its influences on a variety of processes including uplift, climate, runoff, and oceanography. The response of many individual carbonate formations to tectonic activity has been evaluated in Europe (Gawthorpe et al, 1994;Pickard et al, 1994;Rosales et al, 1994), the Middle East (Burchette, 1988;Cross et al, 1998) and Australasia (Davies et al, 1989;Wilson et al, 2000). Models of syntectonic carbonate platform sedimentation are being developed for a range of different tectonic settings (Bosence, 2005), including extensional (Gawthorpe et al, 1994;Bosence et al, 1998), convergent (Dorobek, 1995), and volcanically active (Soja, 1996;Dorobek, 2008).…”