556 MK. A. STRAHAN ON OVERTHRTTSTS OP [Nov. 1 895, 



interrupted by a curving fracture which cuts through Greensand, 

 Lower Chalk, and Middle Chalk, and then curving round again 

 intersects these beds, thus taking what may be called a ' bite ' out of 

 the Upper Cretaceous base. The Upper Greensand then runs 

 through Bincombe, but immediately west of the village is cut out 

 again, nor does it re-appear, except for a few yards east of Bidgeway, 

 for about 6 miles. The short outcrop at Bincombe is probably, 

 therefore, also faulted against the Oolitic rocks. Throughout all 

 the length of this disturbance the Upper Cretaceous rocks dip at a 

 steep angle (60° to 80°) near the line of fault, but quickly flatten 

 •out north of it. 



So far its irregular course, varying throw, and habit of keeping 

 at or close to the base of the Upper Cretaceous escarpment merely 

 suggest that the Bidgeway disturbance differs from a normal fault, 

 but in the underlying Oolitic platform complications occur that 

 cannot be explained on the theory of its being of this character. 

 The difficulty lies in the occurrence of Oxford Clay at Bidgeway, 

 and of an inlier of Oxford Clay, Cornbrash, and Forest Marble at 

 Bincombe, which was first detected and shown on the map by H. W. 

 Bristow. 



It will be noticed that a Bortland Stone outcrop commences at 

 the curving fault near Sutton Boyntz, the rock dipping at a high 

 angle northwards close to the fault, but becoming horizontal at a 

 short distance from it, so as to form the plateau of Chalbury and 

 the neighbouring hill. A similar structure prevails west of Bin- 

 combe, the outcrop of the steeply-inclined Bortland Stone forming 

 a straight scarp parallel to the fault. This scarp should join the 

 corresponding outcrop east of the village, instead of which it 

 abruptly terminates, and we step from it on to Cornbrash. We 

 follow the Cornbrash with Oxford Clay above it and Forest Marble 

 below it for about 400 yards, and then equally suddenly pass on to 

 nearly horizontal Kimmeridge Clay, surmounted by Bortlandian rocks 

 a few yards farther on. The Cornbrash, which here appears at the 

 surface, should in normal sequence occur at a depth of about 1900 

 feet. 



About a mile to the west occurs the well-known Bidgeway cutting, 

 in which the Oxford Clay is again seen in an altogether unexpected 

 position. The section was figured and accurately described by 

 Weston when the cutting was fresh, and enough can still be seen 

 to check his account. The main facts are these : — The Bortland, 

 Burbeck, and Wealden Beds occur in proper sequence, the first- 

 named dipping north at 20°, but the others increasing in inclination 

 up to 60° near the fault, and at the same time swinging round so 

 as to dip N.E. 1 The Chalk on the north side of the fault dips north 

 at 85°, and though its base has not been seen in the cutting, it must 

 lie at no great depth below it, for the Upper Greensand rises into 

 view 300 yards east of the railway. Between the Wealden Beds 

 and the Chalk lies a vertical rib or ' dyke ' of clay, containing 



1 The section runs here nearly along the strike, and therefore does not show 

 this high dip. 



