Page:VCH Berkshire 1.djvu/46

 A HISTORY OF BERKSHIRE during the continental period, for no remains have been found prob- ably any that existed were washed away when depression again set in and the sea waves advanced over Berkshire. In any case our next deposit, the Lower Greensand, is, in so far as this county is concerned, of marine origin, and owing to the earth movements which had taken place since the deposit of the underlying strata it rests upon them in an unconformable manner. The effect of this unconformity is an overlap which is very clearly indicated on the geological map, for it will be observed that the Lower Greensand does not cross the county in a band parallel to the older series but occurs in an irregular and patchy way. The largest patch extends from Uffington almost to Faringdon, and near that place are two small outliers. There is a narrow line between Bourton and Compton Beauchamp, a patch near Drayton, and three outliers near Wootton and Cumnor. The Lower Greensand of Faringdon is of great interest, indeed the sponge gravel found there is probably the most interesting geological deposit in Berkshire. In 1850 a party of geologists, Professor Edward Forbes, Mr. Sharpe, Mr. (afterwards Sir Joseph) Prestwich, Mr. Tylor, Mr. Cunnington, and Mr. R. A. C. Austen visited Faringdon, and the results of their investigation are given in a paper by the last named published by the Geological Society. 1 He remarks : ' What seemed to render this district more peculiarly interesting was the circumstance that it included the beds at Faringdon, so well known from their fossils, as far back as the catalogue of Llwyd, 1759, described by Dr. Fitton 2 as outlying masses of lower greensand, and considered by him to be especially deserving of notice ; also that published lists afforded indications of fossil forms peculiar to this portion of the Cretaceous series and limited to a few localities, and which seemed to present a wide departure from the ordinary conditions which influenced the Lower Cretaceous deposits, such as the numerous and perfect Amor- phozoa at Faringdon.' The late Mr. C. J. A. Meyer made a careful study of these beds and divided them into three divisions : 1. The lowest the calcareous sponge gravel. 2. Above it the red gravel. 3. At the top ferruginous sands with ironstone. The sponge gravel is seen in the pit known as the Windmill pit or Ballard's pit north of the village of Little Coxwell ; it is about 30 feet thick, is fairly well and evenly stratified, and is crowded with fossil sponges and shells. Portions of the beds are here and there consolidated into calcareous masses. The shells are mostly brachiopoda, both Rhynchonella and Terebratula are abundant and belong to several species. The valves are often united, but single valves are quite common, they have not however been at all rolled or waterworn. Many bryozoa are to be found and are in beautiful preservation, but it is the sponges which have made Faringdon celebrated, and they occur in vast abundance. 1 Q uart - 7un>- Geol. Sx. (1850), vi. 454. Geol. Tram. iv. part ii. ser. 2,271. 8