The Volcanic Rocks and Minor Intrusions of the Cross Fell Inlier, Cumberland and Westmorland

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Abstract
The Cross Fell inlier consists mainly of Lower Palæozoic rocks and is situated on the eastern side of the Vale of Eden. It was first described in detail by Nicholson and Marr (1891) and has recently been the subject of a further study by Mr. F. W. Shotton (1935). The former authors considered the stratigraphy of the region, while Mr. Shotton has been concerned with the revision of the stratigraphy and the tectonics. The object of my work, which commenced in 1929 on the suggestion of Professor A. Gilligan, was to map the volcanic rocks and intrusions, describe their petrographical characteristics, and elucidate their stratigraphical relations. More than 300 thin sections of the volcanic, pyroclastic, and intrusive rocks have been made and studied in detail. The mapping is based upon initial field examination, microscopic diagnosis of specimens collected, and then re-examination in the field. This study has led me to conclusions which differ somewhat from those formed by Mr. Shotton (1935). In view of the many small intrusions in the Guns Fell area (Fig. 4), a distinction has been shown between the Skiddaw Slates of Ellergill type and those which have many interbedded sandstones (so thin as to simulate small intrusions). Mr. Shotton appears to have confused these sandstones with felsitic intrusions or tuff bands. Thin sections reveal them to consist of clastic quartz exhibiting strain shadows, with occasional fragments of hard slate. These sandstones reflect shallower conditions of deposition, a more littoral facies not met with elsewhere in the