Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/122

 country in those directions only where the inlets opened to the sea (the gravel within the inlets remaining comparatively undisturbed), the Hampshire high-brow gravels are everywhere so cut off in the direction of the chalk country — as they would be, supposing them, as I do, to be a remnant of the open sea-bottom of the period. All the numerous sections given by Mr. Codrington present this feature ; and though they omit the delineation of the older Tertiaries upon which the gravels rest, an examination of the distribution of these tertiaries as delineated in the Hampshire maps of the Geological Survey will show, by comparison with the sections of Mr. Codrington, that the gravels here have partaken, along with the tertiaries upon which they rest, of that denudation which was consequent upon the upcast of the chalk country. Mr. Codrington regards these gravels as the deposit of an estuary of the sea, some twenty miles wide, that was bounded by the chalk country to the north as land ; and so I agree they were, but not at that early stage when the gravel capping the brows of elevation (to altitudes of 400 feet and upwards) rose out of the sea. At that time the gravel of the Hampshire high brows stretched, I conceive, across the chalk country into connexion with those gravels of the Thames, East-Essex, and Canterbury sheets which now occupy similar brows of denudation, the conditions of land and water being those represented in Map No. II., save that there may have been many islands of chalk over Hampshire that I have not ventured to represent. The marine denudation, consequent upon the upcast of the chalk country, swept off this continuous gravel sea-bottom from the parts subjected to the principal elevatory movements, and cut back the older tertiary outcrops, with their gravel covering, into the condition of brows just discussed, such brows being lifted above the sea. To the south, towards the Southampton water, the but little disturbed sea-bottom continued to receive and preserve gravel accumulations, which formed a more or less continuous sheet with the gravel which had become land on the brow- tops ; while to the north, in the Thames valley, the waters, now converted into the fluviatile condition, continued to deposit gravel and brickearth, which inosculated with those portions of the earlier or marine deposits that had remained undisturbed, but formed terraces beneath the earlier-deposited gravel where this had been elevated*.

I here reproduce a reduction of section 10 of my paper in the 23rd volume of the Society's Journal†, placing beside it one taken from Mr. Codrington's section 6, but extended so as to reach the chalk country, and having the older Tertiaries inserted in it — in order that the identical features which the gravel brows of either area present

Map No. I., and the lower terrace deposit indicated by a different set of dots and lines from the main-sheet gravel. Where no such marked terrace exists, the older and newer portions of the Thames gravel are shown necessarily under the same kind of dotting.
 * These marked terraces, where they exist in the Thames area, are shown in

† In the original section the denuded shelf separating, along the line of section, the gravel on the brow from that at lower level (with which, however, it inosculates in other directions) was not shown ; but it is corrected in the present section.