VOL. xvii. (2) EXCURSION— Y ATE & WICK ROCKS 159 



EXCURSIONS 



EXCURSION TO YATE AND WICK ROCKS 



Tuesday, May loth. 1910 

 Directors : B. A. Baker, F.G.S. and L. Richardson 



(Report by the Directors) 



The weather, with the exception of one short interhide of cold rain as 

 the Members were approaching Wick, was most favourable for this Excursion, 

 and, as on so many previous occasions, the opening field-work for the year 

 proved thoroughly enjoyable. Most of the Members travelled from Gloucester 

 by the 10.10 a.m. train, arriving at Yate at 11. 12 a.m. A brake was awaiting 

 them, and they drove to the workings for gypsum and celestite (or celestine) 

 near Goose Green Farm, distant about three-quarters of a mile to the north 

 of Yate Church. - 



Here, Mr Baker, F.G.S. , of Bristol, pointed out that they were inside 

 the Bristol coalfield. The ridge to the east of them was formed by the out- 

 crop of the hard Carboniferous Limestone ; beneath where they stood was 

 the Millstone-Grit, with a comparatively thin covering of Keuper Marl on 

 top ; while away to the west stretched the Coal Measures. While the Coal 

 Measures and underlying rocks belong to the Palaeozoic and Archaean Groups, 

 the Keuper Marls, Rhaetic, Lias and the Oolites of the Cotteswold escarpment 

 to the east appertain to the Neozoic Group. The Coal Measures were formed 

 under somewhat lagoon-like conditions, which were terminated by intense 

 crust-crumplings. Some areas were upheaved and others depressed, and for 

 a very long period indeed the disturbed strata were subjected to denudation. 

 Valleys were scooped out of the soft rocks ; but the harder rocks formed 

 hills, so that a land-relief of hill and valley was ultimately produced. In 

 time, this land-surface was lowered and the Keuper waters submerged all 

 except the higher hills. From the waters of the Keuper sea were precipitated 

 the layers of gjrpsum and celestite which constitute so valuable commercial 

 assets in the Bristol district. Rha;tic, Lias and Oolites were deposited 

 sequentially above, and in these rocks is chronicled the history of the transi- 

 tion from the inland sea conditions of Keuper times to the coral-reef-encum- 

 bered seas of the Oolite epoch. The Oolite of the Cotteswold Hills and the 

 Lias of the vale once extended much further west, as is obvious from out- 

 lying patches ; but they are being gradually removed, and as they are 

 removed the old land-surface of Palaeozoic rocks is revealed once more and 

 modified. Celestite is specially well seen in the Bristol district, occurring 

 as thin beds and irregular deposits in the Triassic marls, especially near the 

 boundary between the red marls and the tea-green m.arls. It is worked for 

 commercial purposes at many places, especially in the Yate and Wickwar 

 district. Starting from the Golden Valley, near Bitton, the exposures have 

 been followed through Wapley, Yate and Sodbury, near the south end of 

 the Wickwar tunnel, and Cowslip to Ashworthy. The mineral also occurs 

 near Charfield, to the north of the Carboniferous Limestone ridge, which 

 forms the edge of the Bristol coalfield. In all these places the celestite 

 is found in pockets. Often the deposit will run across several fields, but 

 not continuously, as there may be several breaks, and while from one 

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