﻿Vol. 64.] THE BASIC INTETJSION OF BAETESTREE. 501 



27. The Basic Intrusion of Bartestree, near Hereford. By 

 Prof. Sidney Hugh Eeynolds, M.A., E.G.S. (Read June 

 17th, 1908.) 



[Plate LII— Microscope-Sections.] 



CoXTENTS. 



I. Introduction, and Field-Eelations .' 501 



II. The Altered Eocks 501 



III. General Eelations of the Intrusive Eocks 503 



IV. Description of the Intrusive Eocks 503 



V. Conclusion 510 



I. Introduction, and Field -Eelations. 



The field-relations of the basic intrusion of Lowe's -Hill Quarry 

 near Bartestree were fully described by Murchison,^ but, although 

 the dyke has been several times mentioned by later geologists ^ no 

 detailed account has yet been given of its structure. The dyke is 

 of considerable interest, both from its own character and from the 

 alteration to which it gives rise in the Old Eed Sandstone. It has 

 a thickness of about 35 feet, and strikes in an east-north-easterly 

 direction through the Old Red marls and sandstones which here lie 

 almost horizontally. As represented in the I-inch Geological- 

 Survey map, the dyke has a length of about half a mile, striking 

 across the road which leads southwestwards from Bartestree, and 

 extending from about the middle of Tidnor Wood on the south- 

 west to near Bartestree Convent on the north-east. At present, 

 however, the only exposures are at Lowe's-Hill Quarry and for a 

 short space immediately to the south-west. No trace of trap could 

 be found west of the road ; and, although fairly abundant debris 

 occurs in Tidnor "Wood, it appears to be derived entirely from 

 Old-Eed-Sandstone rocks. 



The Lowe's-Hill rock, though not now worked, has formerly 

 been largely quarried ; and a long cutting has resulted, the sides of 

 which are formed by Old Red sandstone and marl, while the trap is 

 exposed at the end. 



II. The Altered Rocks. 



(a) North of the trap. — On the northern side of the cutting, 

 an undulating line, fairly easily followed up the face of the cliff, 

 marks the edge of the intrusion. Against this strikes the Old 

 Red, consisting of alternating bands of sandstone and shale, both 



1 ' Silurian Svstein ' 1839, pp. 185-86. 



2 J. Phillips,' Mem. Geol, Surv. vol. ii, pt. i (1848) p. 180; H.E. Strickland, 

 Quart, Journ. Geol. Soc. vol. viii (1852) p. 384; E. Dixon, Trans. Woolhope 

 Nat. Field-Club, 1867 (1868) p. 180; & J. D. La Touche, ibid. 1891 (1892) 

 pp. 166-68, 



