Geological notes and local details for 1:10 000 sheet SD69NE (Westerdale), and parts of sheets SD69NW (Howgill), SD69SW (Firbank) and SD69SE (Sedbergh) : part of 1: 50 000 sheets 39 (Kendal) and 40 (Kirkby Stephen)

This report describes the bedrock and superficial deposits geology of the southern parts of Howgill Fells, a picturesque upland area located at the easterly extent of the Lake District Lower Palaeozoic inlier in Cumbria. The bedrock geology consists mainly of a thick succession of mudstone and sandstone assigned to the upper Ordovician and Silurian Windermere Supergroup. These rocks are partially overlain by a variable thickness of glacial and post-glacial deposits. This description and an earlier one by the same authors (Woodcock and Rickards, 1999) accompanies, and should be read in conjunction with, the 1:10 000 scale geological sheets SD 69 NW, NE, SW, SE. These maps are components of the 1:50 000 Geological Series sheets 39 (Kendal) and 40 (Kirkby Stephen). The first part of the report provides an extensive review of previous research into the Quaternary geology of the area, which complements a similar review of research into the bedrock geology of the area presented in Woodcock and Rickards (1999). Each of the Lower Palaeozoic bedrock units identified within the area are then described, along with the biostratigraphy and an outline of the depositional history. An account of the various dolerite, felsite and lamprophyre minor intrusions follows. The ?Upper Devonian and Carboniferous rocks around the margin of the area are described briefly for completeness. A description of the structures present and an analysis of the deformation history forms a major section. The final section describes the Quaternary deposits. The Howgill Fells lies immediately to the west of the Dent Fault, a major zone of east-northeast-trending faults which has the form of a positive flower-structure in cross-section and a contractional strike-slip duplex in map view. Associated with the fault zone, structural domes cored by Ordovician rocks were the result of westerly plunging Early Devonian, Acadian folds affected by interference from Late Carboniferous (‘Variscan’) east-north-east-trending folds. The Ordovician Dent Group here is represented by the Cautley Mudstone and Ashgill formations. The Silurian succession is similar to that found in the Lake District, though significant variations in thickness are recorded for some of the units. The lower part of the Bannisdale Formation comprises the youngest strata represented. The Windermere Supergroup here is up to 3400 m thick. Extensive till deposits overlie the bedrock in many of the upland valleys and alongside the River Lune. Alluvium and River Terrace deposits occupy most of the main streams. Peat blankets the flatter upland areas.