The lower carboniferous (dinantian) of the Swords area: Sedimentation and tectonics in the Dublin Basin, Ireland

摘要: The litho- and biostratigraphy of the Lower Dinantian succession in a deeper part Dublin Basin is described. sub-Waulsortian Malahide Limestone Formation (emended) described fully for first time, has proved to be very much thicker than was previously suspected, excess 1200 m. Succeeding ‘Lower Shale’ unit, which transitional from underlying Old Red Sandstone facies, following six new members are recognized: Turvey Micrite Member, Swords Argillaceous Bioclastic St. Margaret's Banded Huntstown Laminated Dunsoghly Massive Crinoidal Member Barberstown Nodular (top). The overlain by ‘Waulsortian’ limestones Feltrim (new name) form overlapping isolated mudmounds with complex relationships their enclosing non-mound facies. Though thicker, Courceyan comparable that elsewhere on south side Basin, Kildare Province (Strogen Somerville 1984). Isopach maps region show this province North Midlands separated deepest named ‘East Depocentre’, shale-dominant facies present. top early Chadian age. Formations younger dominated basinal calcareous shales (Tober Colleen Formation) storm deposits calciturbidites appreciable terrigenous input east (Rush Formation). The main shelf conodont biozones also greatly thickened area. Pseudopolygnathus multistriatus Biozone (> 300 m thick) succeeded thick 900 m) Polygnathus mehli Biozone. base considered occur below and, although equivocal, may diagnosed appearance problematic microfossil Sphaerinvia piai primitive alga Koninckopora. In late Courceyan, area gently sloping extending northwards into basin. During deposition there major deepening evidence initial break up faulting separate blocks. By time definitely subsiding fault displacements contain shallow water faunas littoral sand pebbles derived turbidite flows margins higher subsidence apparently pure flexure, but Visean fault-controlled, differing adjacent Shannon having both strongly faulted.