On some Sections of the Strata near Oxford

Abstract

T he value of exact records of the peculiarities of local sections is strongly felt by every geological reasoner who touches problems of the distribution of oceanic sediments, the boundaries of land and sea, the mixture or alternation of fresh and salt water, or the local origin and geographical diffusion of particular forms of life. This is specially found to be the case while considering the lines of contemporaneity in the mesozoic strata of England, in which the influences of diversified tracts of land and lines of shore, and of unequal sea-depth and varying currents, are complicated by inequalities in the duration of the several groups of organic remains. In the district immediately surrounding Oxford, sections illustrating these causes of local diversity may have more than ordinary interest at this juncture, since here some of the Oolitic strata are supposed to die out, while below them the Upper Lias, and above them the Cornbrash, continue unchanged in mineral character and unchanged in their organic contents; and others, as the Kimmeridge Clay and Coralline Oolite, are supposed to disappear, while either the Wealden takes a great northern development, or the Lower Greensand spreads out into an estuarine and fluviatile deposit. I propose to present, on the present occasion, sections showing the base and the top of the Great Oolite in the valley of the Cherwell. Hereafter I hope to offer similar data for the base of the cretaceous system, at Culham, in the valley of the Thames. No. 1. Junction of Lias