Uppermost Triassic to Lower Jurassic sediments of the island of Ireland and its surrounding basins

Abstract

The uppermost Triassic to Lower Jurassic interval has not been extensively studied across the island of Ireland. This paper seeks to redress that situation and presents a synthesis of records of the uppermost Triassic and Lower Jurassic from both onshore and offshore basins as well as describing the sedimentological characteristics of the main lithostratigraphical units encountered. Existing data have been supplemented with a re-examination and logging of some outcrops and the integration of data from recent hydrocarbon exploration wells and boreholes. The Late Triassic Penarth Group and Early Jurassic Lias Group can be recognised across the Republic of Ireland and Northern Ireland. In some onshore basins, almost 600 m of strata are recorded, however in offshore basins thicknesses in excess of two kilometres for the Lower Jurassic have now been recognised, although little detailed information is currently available. The transition from the Triassic to the Jurassic was a period of marked global sea-level rise and climatic change (warming) and this is reflected in the lithostratigraphical record of these sediments in the basins of Northern Ireland and offshore basins of the Republic of Ireland. In general, the sediments of this interval are thicker than those in Great Britain and have potential for detailed study of climatic and sea-level fluctuation.