THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE II. VOL. IX. 



No. II.— FEBRUARY, 1882. 



a:RXC3-xi>rj^iL, j^i^tioles. 



I. — On the Occetrrenoe of the Ctrena fluminalis at Summer- 

 town, NEAR Oxford. 



By Professor J. Pkestwich, M.A., F.E.S., F.G.S. 



A CONSIDERABLE length of section of the river valley-gravel 

 has recently been laid open in the grounds of St. Edward's 

 School, Summertown It is only 200 or 300 yards distant from the 

 Summertown brick-pit, where the same gravel is exposed, and which 

 is there close on the edge of the Thames valley ; nevertheless, this 

 section presents features which have not been observed there or 

 at any other place, numerous as are the sections of the superficial 

 gravel and sand in the neighbourhood of Oxford. 



Section exposed in digging the foundations for new buildings, St. 

 Edward's School, Summertown, Oxford : — ,^ . 



' ' ft. in. 



1. — Soil -with a few fragments of the underlying gravel ] 



2. — Light -coloured, fine gravel (with irregular black and ferruginous veins) 

 composed of water-worn fragments of the Great and Inferior Oolites, 

 Forest Marble and Cornbrash, with specimens of the Gryphea dilatata 

 from the Oxford Clay, and of older rock pebbles (quartzites, etc.) and 



Chalk flints from the Glacial Drift 3 2 



3. — Fine yellow sand with land and freshwater shells, and fossil remains 



of Elephant, etc., in the lower part 3 6 



Under this by digging I found three feet more of sand, and then 

 some hard gravel, which rests probably on the Oxford Clay. 



In the Oxford district, this gravel occupies a level or terrace about 

 20 to 25 feet above the level of the Thames and Cherwell, and small 

 patches of the same gravel are met with on the same level at the foot 

 of the hills on the other side of the valley at Wytham and North 

 Hincksey, having once extended across the valley at that level, and 

 the valley below that level having since been excavated by prolonged 

 river-action to its present depth. After that the valley received the 

 alluvial deposits which now form the flat river lands such as Port 

 Meadows, and which contain the remains of the Eed Deer, Roebuck, 

 Wolf, Wild Boar, Horse, Ox, etc. 



The gravel consists of water- worn fragments of various Oolitic 

 rocks belonging to strata over which the Thames and its tributaries 

 flow above Yarnton and Eynsham, that is to say, strata which form 

 the hills about Handborough and Charlbury, and the slopes of the 

 Cotswold Hills bej'ond Witney, together however with the harder 



DECADE II. — VOL. IX. — NO. II. 4 



