PROCEEDINGS

OF THE GEOLOGISTS' ASSOCIATION.

EXCURSION TO OXFORD UNIVERSITY MUSEUM, ENSLOW BRIDGE, AND WOODSTOCK.

SATURDAY, MAY 21ST, I9IO.

Directors .. 1\1. M. ALLORGE, F.R.G.S., AND C. J. BAYZAND. Excursion Secretary .. MISS E. PEARSE.

(Report by THE DIRECTORS.)

THE party assembled at Paddington Station and proceeded by the 9.50 a.m. train to Oxford, where they were met by Mr. Allorge and were conducted by him to the University Museum, via Broad Street and Park's Road. The party had an opportunity of observing the atmospheric effect of weathering of the local Corallian Limestones from Headington which were once so extensively used as a building stone for the Sheldonian and Old Clarendon buildings and others, now giving them a somewhat dilapidated appearance. The members were received at the University Museum by Professors W. J. Sollas and H. L. Bowman, who described the arrangement of their respective departments. Professor Sollas explained in detail the great Cetiosaurus oxoniensis, one of the treasures of the Museum, together with an original drawing on the scale of r-r oth by Baron Von Huene of Tubingen, It is the largest example of an extinct reptile known in Europe, and one of the two or three largest in the world. The complete skeleton measures 66 ft. long, r z ft. high, and 6 ft. 6 in. broad. The members were also shown the remains of Megalosaurus bucklandi and Teleosaurus sp., also a large specimen of Mystrio­ saurus from the Upper Lias of Wurtemberg, recently obtained from Germany, together with the famous Jaws from the Stonesfield Slate, and also remains of the now extinct Dodo. The general arrangement of the stratigraphical series was PROe. GEOL. Assoc., VOL, XXII, PART I, 19I1.] 2 EXCURSION TO OXFORD. next explained, attention being more especially directed to the series illustrating the geology of the Oxford district. The arrangement of the Igneous, Metamorphic and Sedi­ mentary rocks was then explained. Professor Bowman next dealt with the Mineralogical Col­ lections, showing several exhibits of great interest, including a series of Moss Agates from the collection of the late Mr. John Middlemiss Luff, together with specimens arranged to illustrate the uses of minerals, in addition to Mr. E. W. Streeter's collection of precious and semi-precious stones in the cut and uncut state; also a series of forty-three crystals of diamonds, including a model of the celebrated Cullinan diamond. The case illustrating the method of obtaining the specific gravity of minerals by heavy solutions proved very interesting, as did also the fine collection of Corsi and British Marbles, the Professor concluding with a detailed description of the Meteorites. At the conclusion of the visit to the Museum Mr. Osborne White expressed the thanks of the members to Professors Sollas and Bowman, and the party, numbering fifteen, then drove to the quarries at Enslow Bridge on the Ban bury road, some six miles to the north of Oxford. The road runs across the low­ lying pasture lands characteristic of the Oxford Clay, on which the town is itself situated. At Station the junction of the Oxford Clay and the Cornbrash was traversed, and shortly afterwards notice was directed to a riverless valley along which the has been constructed. It was suggested that at one time the , instead of, as now, flowing into the River Ray at Islip, may have proceeded directly south to join the Isis at King's Weir. The party alighted from the brakes a quarter of a mile short of Enslow Bridge and proceeded to examine the valley of the Cherwell. The topography of the region as subordinate to its geological structure was pointed out. Oxford is situated at the point where the waters of the Upper Thames have succeeded in breaking through the escarpment of Corallian Rocks, the outworks of which, at Wytham and at Elsfield, were at the moment scarcely visible on account of the summer haze. North of this extends the belt of Oxford Clay which had just been traversed, and the party were now on the plateau of Great Oolite, gently rising toward Edge Hill. This plateau is threaded by several dip-streams which have succeeded in cutting winding valleys, on the floor of which they again describe a series of smaller meanders, inscribed, so to speak, in the broader ones. The valley of the Cherwell, as seen from the edge of the escarpment face (the place marked At PI. I, Fig. r) on which they stood, gave a very characteristic curve. This escarpment has been produced by the wearing away of the rocks on the PROC. GEOL. Assoc.• V OL. XXII. PLATE I.

(I'''N_ /t.r C. 7. J,'l.),:.'JlI{. FIG. I. - R IVER CHERW ELL AT E NSLOW BRlf)GE.

rrlut/-' "." r. 7. Rn 'Y':f", f. FIG. 2. - S ECTI ON OF GREENHILL FARM Q UA RR\·. E XCURSIO N TO OXFORD . 3 co nvex sid e, while on the concave side of th e curve the ground ge ntly rises to th e right of th e picture, which demonstrates clearly the process of denudation, producing the valley as shown by th e photograph (see also th e section, Fig. r) to be river erosion. Several th eories have been advanced in order to account for -the " misfits " of the present stream. Prof. ' V. M. Davi s seeks their origin in th e shrinkage of th e present rivers produced by th e diversion of th eir head waters to the Avon-Severn. Prof. H er bertson suggests that the meand ers are a legacy of th e period when the stream flowed on the Oxford Clay, which a t" on e time probably extended over the limeston e. The Rev . E. C. Spicer suggests that som e of these valleys have originated by th e slow subsidence of th e gro und from above the windin g underground courses following a series of master-joints widened by solution. The Directors did not wish to dogmatise as to th e actual part played by these different processes; more exact observati on and measurements were needed before a solution cou ld be arrived at. They were of the op inion that all the agen cies had unit ed in contr ibuting to th e shaping of the present topography . The geological formations and zones of th e quarries which next formed th e subjec t of attention will be best understood from the photograp h (Plate II) and the acco mpany ing explanation. From the neigh bourhood of these quarries the large Saurian bones of Cetiosaurus oxoniensis togeth er with Megalosaurus and Teleosaurus were obtained. Fossils were numerous, speci mens of the following being fo und by memb ers of the party: Cervillea zoaltoni, Amberleya nodosa, A starte sp., Unicardiu J/l sp., and oth ers from the Forest Marble ; Terebratula maxillata, jJ:fodiola imbricata, Cypn'n a islipe nsz~f, C. lozoeana, Fibula variata, N erillea voltzH, N. eudesii , .and _iVa zdi/us baberi from the Great Oolite. Mr. Ll. Treacher was very fortunate in finding speci mens of th e Bryozoa, B erenicea arc/tiaci, Haime, an d B. dillt'lJialta, Lamx. (Plate III).• encrusting T. max illata. The " Cream Cheese " Bed as mentioned by Mr. G. Barrow in his report on the new G. W. Railway cutting from Ashendon to Aynho, can easily be identified in th e Enslow Bridge Quarry, as well as at Ki rtlington, as can also the N erinea-Bed, which forms a good hor izon for zoning purposes. In the joints of the Great Oolite several small caves were observed, no dou bt formed by the percolation of th e water through the limestone. I n a formation like limeston e, which is relatively soluble, conside rable quantities of material are fre­ quently dissolve d from a given place, and caverns are developed. In these small caves occurred miniature stalactites and stalagmites, and bet ween the joints sheets of calc sinter. After visiting the G ibraltar Q uarries the party proceeded to cross the river Cherwell 4 EXCURSION TO OXFORD.

to the Greenhill Farm Quarries (Plate I, Fig. 2). The Cornbrash and Forest Marble were here typi­ cally exposed (see Fig. I). Fossils from the Cornbrash were found to be very common, including: Terebratula obovata, ll:fyacites cunei­ formis, H011l01ll)'a liibbosa, Avicula eelzinata, Anabacia orbitoides, Aero­ -c= c- salenia lzemicidaroides, Ho/ectypus ~" depressus, and Pygurus, sp. Q:;". The party then rejoined the ~ brake and continued the journey to \.5 Kirtlington. Here attention was I drawn to a gravel-pit which rests on 7- c the Oxford Clay (Fig. I). Proceed­ f-< (J ing towards the Three Pigeons Inn, : a visit was made to the Oxford ~ Portland Cement IVarks, near Kirt­ lington, and the whole sequence of ::2 ~ 0 ~ the strata was explained; it consists f-< of the Cornbrash, Forest Marble ;.: e-, u ~" Limestone, showing false bedding, 0 '<>" f-< "~ U1 and the Great Oolite, characteristic­ § ~ ally even-bedded with clay partings. 0 .::" .::l Between the Forest Marble and E::: So Great Oolite occurs a well-defined Z bed of clay, from which fragments ;::C of Apiocrinus have been obtained. u ~ In clays of the same horizon at if] Islip there has been found Dictyo­ :E <: thyris coarctata, another zonal fossil '"(J of the Bradford Clay. s The joints in the Great Oolite 0 were very conspicuous, and it was ~ further observed that the joints, as g they approached the valley, were ~ inclined towards it, suggesting a marked surface creep. Looking westward across the valley one could perceive the deserted meander which seems formerly to have been followed by the Cherwell previous to a cut­ off which separates Whithill spur from the plateau on which Kirtling­ ton stands. Two points could be noticed: the presence in the main PROC, GEOL. Assoc., V OL. XX II. PLATE II

R ubbly marl ~ n d ma rb-tcne with A r'kula (.n.,,· a t a,

Compa ct :.:r e y lime stone• .\ hcrnati llJ: hect:- of lime-tone. :LUU days \\ ith Fcnu ·...'t-. O s 1"'('11 SMC/o :\t.\k IU .J·. ,,./1)'1.

Bt"d.. of marl)' I n l s e-b e d d e d limeston e and cia)'.., with Tone of 'l,,.t6"'(llul(l ma r morra ,

C I ~)'. probnb ly J:. ArH·o k" C',A"•

•,Cream-clree e ' bed , - (; . Ha r-

\\. h it e ool itic lime ..tone ev en - C p 1 lv bedded, With j ( ;'~' Zone of Hpi /lry. .,\ I YlS h .tl"",ka.

Xerin a bed , f /'It I, It) I. C. 1I., r / il' SE CTION OF E NSLOW BRIDGE QUARR\'.-C. ]. Baysand, EXCURSION TO OXFORD. 5 valleys of well-marked terraces which point to river erosion, and the absence of any well-marked terraces in the subsidiary valleys, which suggests that the main work there has been pro­ duced by solution. The party then drove to Woodstock, and the geo-morphology of the district was explained during the drive (Fig. I). On the right-hand side of the road, near to the cross-roads that lead to Sturges Castle, an " Ox-bow" was observed, and in the neighbour­ hood of Wooton several dry valleys, together with the Solution­ Valleys in Glyme area, were pointed out to the party (see Spicer, Quart. Journ. Geol. Soc., vol. lxiv, 190 8, p. 335). On reaching Woodstock the members alighted at the Marlborough Hotel for tea, after which the usual votes of thanks were proposed to the Directors, who, in their reply, remarked that the visit of the Association coincided with the appearance of Halley's Comet, and expressed the hope that the periodicity of their visits to Oxford would be of shorter duration than that of the comet. On the return to Oxford, a brief halt was made at Summertown to examine the exposure of Oxford Clay with the Second Terrace Gravel on top, and the members reached Oxford in time to catch the 7.20 train to London. REFERENCES. Geological Survey Maps, New Series, Special Sheet, Oxford. Geological Survey Map, Old Series, Sheet 45. S.W. 1859. HULL, E._H The Geology of the Country around Woodstock, ." Mem. Geol Surv. 1860. PHILLIPS, J._H The Great Oolite in the Valley of the Cherwell." Quart. Journ. Geol Soc., vol. xvi, p. 1I5. 1864. GREEN, A. H.-" The Geology of the Country round , Woodstock, , and Buckingham." Mem. Geol. Suru. 1871. PHILLIPS, .I.-HGeology of Oxford and the Valley of the Thames." 1871. PHILLIPS and EARWAKER.-HExcursion to Oxford." Proc. Geol. A ssoc., vol. ii, p. 243. 1881. PRESTWICH, Sir ].-" An Index Guide to the Geological Collections in the University Museum, Oxford." 1895. WALFORD, E. A.-" Excursion to Banbury, , Edge Hill, and ." Proc. Geol, Assoc., vol. xiv, p. 177. 1898. SOLLAS, Prof. .I. VV._H The Influence of Oxford on the History of Geology." Science Progress, vol. viii, reprinted in "The Age of the Earth and other Geological Studies," 1905. 1899. DAVIS,Prof. W. M.-" The Drainage of Cuestas.' Proc, Geol. Assoc., vol. xvi, p. 75. 1904. HEALEY, MAUD.-HNotes on Upper .IurassicAmmonites, with special reference to Specimens in the University Museum, Oxford." Quart. Jonnl. Ceol. Soc., vol. lx, p. 54. 1908. POCOCK, T. I._HThe Geology of the Country around Oxford." Mem. Ceol Suru, SPICER, Rev. E. C.-" Solution-Valleys in the Glyme Area, Oxford. shire." Quart. Journ. Geol. Soc., vol. lxiv, P: 335. 1909. VERNON, Dr. H. M.-" A History of the Oxford Museum," DOUGLAS, J. A._H The Oxford and Banbury District," "Geology in the Field," chap. vii.