366 L. Richardson — Rhcetic Section at Wigston. 



hj'persthene, the highly zonal felspars may be considered as inter- 

 growths of various plagioclases, and the final product of crystallization 

 is an intergrowth of quartz and orthoclase. 



New synthetic data as to the products of the fusion of plateau 

 basalts or ultra-basic rocks with acid gneisses, schists, and sandstones, 

 under varying conditions of temperature and pressure, might possibly 

 throw some light on the problem. It is worthy of note in this 

 connection that the magma-reservoirs of many occurrences of grano- 

 phyric diabase may reasonably be supposed to be located in a highly 

 siliceous country rock. The rock is very common in areas of 

 fundamental gneiss, as in Scandinavia, Rainy Lake region of Canada, 

 the interior of British Guiana, and Southern India. In Scotland the 

 area is probably underlain by many thousand feet of Calciferous 

 Sandstone, Old Eed Sandstone, and perhaps the Dalradian gneisses 

 and schists. 



A 



VII. — The Rh^tic Section at Wigston, Leicestershiee. 



By L. Richardson, F.E.S.E., F.L.S., F.G.S. 



T the Glen-Parva Brickworks, AVigston, near Leicester, is the 

 finest section of the Rhsetic beds that is to be seen in the 

 Midlands. The large subcircular pit where the beds are displayed at 

 once arrests the attention of the traveller on the adjacent railway as 

 an excavation of more than usual size. 



At the base of the pit are the red and greenish -grey-zoned marls of 

 the Keuper, replete with layers of pink gypsum ; then come the tea- 

 green marls of the same series, well marked-off from the red rocks 

 below and the markedly black shales of the Rhsetic Series above ; 

 while at the top, at the western end of the pit, come reddish-stained 

 gravels, and at the eastern the pale-yellowish marls and limestones of 

 the Upper Rhaetic succeeded by the basal beds of the Lower Lias with 

 but a sprinkling of gravel here and there. 



Naturally so fine a section as this has not escaped attention. It has 

 been measured in detail by Edward Wilson and H. E. Quilter,' and 

 investigated later by Mr. Montagu Browne," who, in a report of an 

 excursion of the Leicester Literary and Philosophical Society, has given 

 pictures of the pit, diagrammatic sections, and criticisms on his prede- 

 cessors' work. Others have briefly referred to it,^ and Mr. C. Fox- 

 Strangways in the Geological Survey Memoir on " The Geology of the 

 Country near Leicester " (p. 16), has summarized the information that 

 had been published previous to his time of writing. 



The object, then, of this communication is obviously not to give 

 a record of an entirely fresh section, but merely to suggest a somewhat 

 different reading of a well-known one. 



Commencing at the base of the section, the 12 to 15 feet of 

 "Tea-green Marls" are very distinct, and the line of demarcation 

 between them and the JPteria-contortaShales is exceptionally sharply 

 defined. 



1 Geol. Mag., 1884, Dec. Ill, Vol. I, pp. 415-18. 



- Trans. Leicester Lit. and Phil. Soc, 1901, vol. vi, pt. i, pp. 32-8. 



3 Idem, N.Q.S., 1889, vol. i, pt. ii, p. 14 ; A. S. Woodward, idem, p. 22. 



