Facies and sequential organisation of a mudstone-dominated slope and basin floor succession:the Gull Island Formation,Shannon Basin,Western Ireland

摘要

The lower part of the Carboniferous Shannon Basin of Western Ireland contains a deep-water succession which exceeds 1200 m in thickness that comprises five lithologically different units deposited within a confined,relatively narrow basin:(i) a calciclastic debris-flow and turbidite unit formed by resedimentation from nearby carbonate platforms,(ii) a siliciclastic black shale succession with former source potential which onlaps basin margins (Clare Shales),(iii) a sandstone-dominated turbiditie formation,controlled by ponded accommodation and deposited axially in the basin (Ross Formation),(iv) a mudstone-rich turbidite-bearing succession,which onlaps basin margins (lower Gull Island Formation),and (v) a mudstone-domianted prograding slope succession (upper Gull Island Formation and lower Tulling Cyclothem),which grades transitionally upwards into deltaic deposits.