The age and composition of the Whin Sill and the related dikes of the north of England

Abstract

The system of intrusive sheets in the Lower Carboniferous formations of the north of England, familiar to geologists throughout the world as the Great Whin Sill, has a voluminous early literature which it is unnecessary to summarize here. It will be sufficient to refer to the classical papers by Topley and Lebour on the field relationships (1) and by Teall on the detailed petrography (4), each of which contains an ample bibliography of the earlier literature. The most recent general account is by Prof. E. J. Garwood (9), who contributed a careful discussion of the evidence bearing on the period of intrusion.Teall's great paper closely followed on one devoted to some of the dikes of the north of England (3), and in it he drew attention to the remarkable petrographical Similarity between the rocks of the Heft and High Green dikes and that of the Whin Sill (4, p. 656).

Intrusive Phenomena of the Whin Sill, East of the R. North Tyne

“…This agrees with the conclusions reached by Holmes and Harwood (1928) after a consideration of the Whin Sill and its relation to the structure of North Northumberland.…”

Emplacement of the Great Whin Dolerite Complex and the Little Whin Sill in relation to the structure of northern England

“…The E-W St. Oswald's Chapel and Hett-Ludworth dyke echelons to the north and south of the Alston Block have been described as feeders for the sills on the block, but no field evidence to support this has been presented (Holmes & Harwood 1928;Anderson 1951;Francis 1982). Two similar E-W dykes cross Northumberland.…”

“…From the preceding discussion, the time of emplacement of the Whin dolerite complex can be narrowed to the interval between the WSW-ENE directed folding, that produced the Burtreeford Disturbance, Holburn and Lemmington folds, and the uplift event that formed the Teesdale and Cheviot domes. (Holmes & Harwood 1928;Dunham 1932). Determination of the absolute age of the Whin by isotopic analysis using the helium method began in the 1920s and produced a low figure of 196 Ma (Dubey & Holmes 1929).…”

“…Starting in the 1920s, the broad sequence of subsidence and deposition, uplift, folding and erosion has been recognized and successive workers have confirmed the pattern of change and added new findings. Notable contributors to this work include Holmes & Harwood (1928), K. C. Dunham (1933Dunham ( , 1948Dunham ( , 1990, A. C. Dunham & Kaye (1965) and Fitch & Miller (1964,1967. Our summary diagram (Fig.…”

The relationship of orthopyroxene to pigeonite

“…Such conditions prevailed in the Palisade sill (Walker, 1940), the Whin sill (Holmes and Harwood, 1928), the Hangnest sill (Walker and Poldervaart, 1941) and the Sedgewick laccolith (Edwards, 1942). These intrusions all carry pigeonite in their upper portions, while orthopyroxene occurs in the lower parts.…”