MARINE BANDS OF ARNSBERGIAN AGE (NAMURIAN) IN THE SOUTH-EASTERN PORTION OF THE ASKRIGG BLOCK, YORKSHIRE

Abstract

Summary The Cockhill Marine Band of earliest Arnsbergian (E 2 ) age persists throughout the south-east quadrant of the Askrigg Block, and yields a large fauna, including the characteristic goniatite, Cravenoceras cowlingense; there is an increasing abundance of brachiopods towards the north. A new locality in the Mirk Fell Ironstone Series in Upper Swaledale yielding C. cowlingense is described. The Colsterdale Marine Beds of Arnsbergian age also persist throughout the area, two beds of shale being separated by the Colsterdale Limestone. The marine shales below the limestone vary locally in thickness, especially in the north where in Colsterdale thickening is accompanied by the appearance of a nuculid-gastropod fauna. Faunal characteristics of the marine beds are considered in terms of both lateral and chronological changes, and a case made out for a progressively deeper or more saline environment towards the southern margin of the Askrigg Block at the time of deposition of the upper part of the Colsterdale Marine Beds.