III.—The Solent River

Abstract

At Portsea Island a change takes place in the character of the drift, the 5 to 6 feet of gravelly clay forming the “Head” on the Old Beach to the east, being replaced on the same level by a bed of gravel, which, according to Mr. T. Codrington, attains a thickness of 27 feet, and still contains some boulders similar to those of Hayling Island, together with blocks of sarsenstone. to the west of Gosport the ground rises and the low cliffs of Stubbington and Hill Head are capped by 10 to 15 feet of gravel of a somewhat different character. No foreign boulders are to be seeninit, though I have found pebbles of quartzite derived apparently from the Triassic strata of Devonshire, as also some small subangular fragments of granite and other old rocks, large blocks of Tertiary Sandstone, and a few worn fragments of a fresh-water limestone containing small Lymneæ. There are no shells either fluviatile or marine, and no beach underlies the gravel which rests directly on the Tertiary strata. It is intercalated with seams of sand and loam roughly bedded, and contains flint implements. It is evident, therefore, that we have here some important changes in physical conditions, and that a considerable alteration in the characters of the drift-beds likewise commences. This has led to the belief that the gravel on the coast from this point to Bournemouth and Poole is the Alluvium of an old river, which, before the removal of the Chalk ridge that extended across the bay of Christchurch, blocked the rivers flowing southward, and diverted them into a main stream flowing eastward, passing along the line of the present Solent and debouch in g in the area now occupied by Spithead.