ON STONESFIELD SLATE. 305 



consisted in scarping the bank for 33 feet, and in continuing the section 

 by carrying a shaft of 20 feet in depth through the lower bank. The 

 purpose of the work has been so far successfully carried out by showing the 

 existence of 30 feet of rock with some thin clay courses below the Slate. 

 These limestones and clays (see accompanying section on p. 306) are of Great 

 Oolite type. To reach the Clypeus grit will need an extension of time. 



Your Secretary has, by the discovery of numerous species of corals on 

 the ploughed fields on the bank top, been able to define the coral bed 

 (Rift bed) ' so prominent a feature in the near section at Ashford Bridge. 

 Seventeen feet below the coral bed a course of Slate is met with, almost 

 thinned out at that point, and only from 5 to 7 inches in thickness ; 

 the total thickness of it and the associated beds (10, 12, 13 of the section) 

 being about 5 feet. The usual fossils, Trigonia impressa, <fec., occur. In 

 the lower limestones, 15 and 17, are greenish clay inclusions. 



The great mass of buff limestone below the slate is almost unfossiliferous, 

 and neither its mineralogical character nor its few fossils give sure evi- 

 dence of its relationship to neighbouring beds. 



Prominent in the lower half of the section is the breaking up of the cal- 

 careous series by small clay beds, and of these No. 23, with its dark compact 

 clays, is in part made up of oyster-shell fragments. It contains numerous 

 compressed shells, Perna quadrata, Nucula, &c., but washings of the beds 

 yield hardly any microzoa. The limestone above the clay yields well- 

 known Great Oolite shells, Mytilus Sowerhyanns, Rhynchonella concinna, 

 and Ostrea Sowerbyi. The shelly limestone below the clay is in part an 

 Oyster iumachelle, and passes into a blue-hearted limestone with Perna 

 quadrata, large Cyprince, Corbtila, and Macrodon. Here, again, both 

 petrological facies and fauna are dissimilar to any of our known Oxford- 

 shire Oolitic rocks, and, like each of the succeeding lower beds, should be- 

 classed as Great Oolite ; one of the latter, a hard very oolite freestone, 

 has also as distinctive a character. 



In conclusion, it should be stated that though, when Professor Ed. 

 Hull reported to your Association at its Oxford meeting, thirty-four years 

 ago (1860), the presence of seventy feet of Great Oolite limestone under 

 the Stonesfield Slate, it seemed to be an over-estimate, yet the result of 

 the present investigation has been to prove the presence of an important- 

 and overlooked section of the Great Oolite, and to entitle place for it ir^ 

 future accounts of that subdivision. That Professor A. H. Green doubted 

 the existence of so great a series of beds as those quoted by Professor 

 Hull is proved by the absence of any account of them in his excellent 

 memoir ' On the Geology of the Country round Banbury, Woodstock, 

 Bicester, and Buckingham,' published in 1864. 



Mr. James Windoes, Mr. Wilfred Hudleston, Mr. H. B. Woodward, 

 and your Secretary have also worked in later years at the determination 

 of the equivalent of these lower Bathonian beds in the neighbourhood of 

 Chipping Norton. 



To his Grace the Duke of Marlborough, to the Right Hon. Lord! 

 Dillon, to Mr. John Barrett of Stonesfield, and to Mr. S. Shilson of 

 Charlbury, the thanks of your CoE^.mittee are due for aid in this and other 

 relative work.- 



The probable extension of a lower division of the Great Oolite below 



• E. A. Walford, Q.J.G.S., vol. xxxix. p. 230. 



* Mr. U. F. Tomes has kindly named the corals. 



1894. X 



