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  

作　　者：Markus Pracht Ian D.Somerville 

机构地区：[1]Geological Survey of Ireland,Beggars Bush, Dublin 4, Ireland [2]UCD School of Geological Sciences,University College Dublin,Belfield, Dublin 4, Ireland

出　　处：《Journal of Palaeogeography》2015年第1期1-26,共26页古地理学报（英文版）

摘　　要：An integrated study of borehole data and outcrop of Mississippian （late Tournaisian to late Visean） rocks in Co. （County） Galway, western Ireland has enabled a more detailed geological map and lithostratigraphy to be constructed for the region. Several carbonate formations have been distinguished by microfacies analysis and their precise ages established by micropalaeontological investigations using foraminifers and calcareous algae. In addition, palaeogeographic maps have been constructed for the late Tournaisian, and early to late Visoan intervals in the region. The oldest marine Mississippian （late Tournaisian） deposits are recorded in the south of the study region from the Loughrea/Tynagh area and further south in the Gort Borehole; they belong to the Limerick Province. They comprise the Lower Limestone Shale Group succeeded by the Ballysteen Group, Waulsortian Limestone and Kilbryan Limestone Formations. These rocks were deposited in increasing water depth associated with a transgression that moved northwards across Co. Galway. In the northwest and north of the region, marginal marine and non-marine Tournaisian rocks are developed, with a shoreline located NW of Galway City （Galway High）. The central region of Co. Galway has a standard Visdan marine succession that can be directly correlated with the Carrick-on- Shannon succession in counties Leitrim and Roscommon to the northeast and east as far as the River Shannon. It is dominated by shallow-water limestones （Oakport, Ballymore and Croghan Limestone Formations） that formed the Galway-Roscommon Shelf. This facies is lat- erally equivalent to the Tubber Formation to the south which developed on the Clare-Galway Shelf. In the southeast, basinal facies of the Lucan Formation accumulated in the Athenry Basin throughout much of the Visean. This basin formed during a phase of extensional tectonics in the early Visean and was probably connected to the Tynagh Basin to the east. In the late Visean, shallow-water limestones of the Burren FormatioAn integrated study of borehole data and outcrop of Mississippian （late Tournaisian to late Visean） rocks in Co. （County） Galway, western Ireland has enabled a more detailed geological map and lithostratigraphy to be constructed for the region. Several carbonate formations have been distinguished by microfacies analysis and their precise ages established by micropalaeontological investigations using foraminifers and calcareous algae. In addition, palaeogeographic maps have been constructed for the late Tournaisian, and early to late Visoan intervals in the region. The oldest marine Mississippian （late Tournaisian） deposits are recorded in the south of the study region from the Loughrea/Tynagh area and further south in the Gort Borehole; they belong to the Limerick Province. They comprise the Lower Limestone Shale Group succeeded by the Ballysteen Group, Waulsortian Limestone and Kilbryan Limestone Formations. These rocks were deposited in increasing water depth associated with a transgression that moved northwards across Co. Galway. In the northwest and north of the region, marginal marine and non-marine Tournaisian rocks are developed, with a shoreline located NW of Galway City （Galway High）. The central region of Co. Galway has a standard Visdan marine succession that can be directly correlated with the Carrick-on- Shannon succession in counties Leitrim and Roscommon to the northeast and east as far as the River Shannon. It is dominated by shallow-water limestones （Oakport, Ballymore and Croghan Limestone Formations） that formed the Galway-Roscommon Shelf. This facies is lat- erally equivalent to the Tubber Formation to the south which developed on the Clare-Galway Shelf. In the southeast, basinal facies of the Lucan Formation accumulated in the Athenry Basin throughout much of the Visean. This basin formed during a phase of extensional tectonics in the early Visean and was probably connected to the Tynagh Basin to the east. In the late Visean, shallow-water limestones of the Burren Formatio

关 键 词：Carboniferous MISSISSIPPIAN western Ireland carbonate microfaciesbiostratigraphy FORAMINIFERS shelf and basin environments palaeogeography 

分 类 号：P531[天文地球—古生物学与地层学]