II.

The Geology of Edge Hill.

he Geology of the Edge Hill region presents points of study to the student of the physical phases of the science rather than to the palæontologist, though it does not appear in either case that the conditions presented are difficult to read. Beginning with the low range of hills three miles N.W. of Kineton, forming the Trias outcrop, and fringed with a thin development of Rhætics, we cross the broad plain of the Lower Lias almost without undulation, save in the ridge which stretches from Gaydon to Butler’s Marston, until the foot of Edge Hill itself is reached. Fragments of Ammonites of the rotiformis type are occasionally ploughed up in the plain, and the railway cutting at North End has yielded specimens of Ammonites semicostatus. The hill slopes are in the main formed of the clays and shales of the Middle Lias, the Zone of Ammonites margaritatus with certain characteristic fossils, Cypricardia cucullata, &c., appearing in the old brickyard at Arlescot. There is no other exposure of the seleniferous shales of the zone; their course is masked by a rich belt of woodland. The natural terraces somewhat characteristic of this horizon in the midlands are roughly developed towards the Sun Rising, and are more perfectly shown at Hadsham hollow in the Hornton vale. At Shenington, four miles southward, there are some beautifully terraced fields, one locally known as Rattlecombe Slade recalling to mind the lynchets of the Inferior Oolite sands of Dorsetshire. They are in the main terraces of drainage, the step-like form of subsidence being due to the composition of the seleniferous marls and under waste. The terraces are of exceptional regularity, and run parallel to the lines of drainage; in one case, however (Kenhill), in the same locality, they form a bay or recess on the hill slope. A familiar instance of the last phase is to be seen at the Bear Garden, Banbury. The salient feature of the Edge Hill escarpment is the Marlstone rock-bed, the uppermost division of the Middle Lias. Several sections in this zone (Ammonites spinatus) may be seen near the Round House. It has three main divisions: The upper red layers the roadstone, the middle of several green hard beds called top-rag, and the lower courses of dark green softer stone, the best rag (used for building). Some of the quarries have been worked for centuries, and the grey green slabs of Hornton stone, its local name, are familiar on the hearths and in the homes of nearly the whole country-side. At this its N.W. outcrop, the rock thickens considerably, attaining a development of about twenty-four feet. The stone itself is a ferruginous limestone, greenish when unweathered, otherwise of a rich red brown colour. Good evidence of its durability as a building material is shewn in the fine fourteenth century churches of North Oxon, which are almost without exception built of the stone. Near the Beacon House on the Burton Dassett Hills, a good section is exposed in which fossils are found more freely. Amongst the brachiopod shells Waldhemia indentata, Terebratula punctata, T. Edwardsii occur, together with an abundance of the characteristic Rhynchonella tetraëdra: Spiriferinæ are rare. When the ironstone workings were extended, ten years or so since, large Pholadomya ambigua and other shells were obtainable from some sandy beds at the base of the series. Capping the “spinatus” beds are a few feet of Upper Lias Clay belonging to the zone of Ammonites serpentinus, and fragments of the Ammonites common to the horizon are scattered about; but these beds are not found along the escarpment east of Shenloe Hill.

By the roadside leading from Burton Dassett to Fenny Compton, a small quarry on the south side shows a patch of Inferior Oolite. A fault has preserved this the only remnant to prove the former extension of the Bajocian beds over the area of the Burton and Edge Hills. Tysoe Hill, four miles S.W. of the Round House, and the hills which fringe the borderland of Warwickshire and Oxon, are nearly all capped with sands or limestones of the Inferior Oolite, and occasionally with the marly limestones of the Great Oolite also.

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BANBURY CROSS.