Notice of some Sections of the Strata near Oxford

Abstract

I n England, unconformity between the Cretaceous and the Oolitic strata is discoverable at almost every part of the range of the junction of deposits, from the coast of Yorkshire to the cliffs of Dorsetshire. Everywhere evidence can be found of the wasting action of the sea on the Oolitic strata before the deposition of the superincumbent rocks, and sometimes evidence of the movement of the sea-bed (to which, perhaps, the watery agitation was due). In the country near Oxford, and from this point south-westward, the Portland Oolite has been thus greatly wasted, so as to remain in only a few detached masses. There seems reason to suppose that movements of the sea-bed of considerable extent followed the deposition of the Oxford Clay; for the Coralline Oolite fails, and the Kimmeridge Clay grows thin, and hardly traceable far from the Shotover Hills, in a direction towards the north-east. The deposition of the Cretaceous series on the wasted Oolites was thus inevitably irregular; but in addition we have the varieties of littoral, estuary, and fluviatile deposits on the boundary-surface of the Oolites; great surface-waste, referable to the Postpliocene age; and faults which seem to be of great effect, but are not yet traced out. Under these circumstances, it is at once a very interesting and a very perplexing problem of field-geology to trace out the detached, unconformed and wasted cappings of sand and ferruginous stone which, in several places, lie on the Kimmeridge Clay, and are not themselves covered by strata of