58

In these soils roots and stumps of trees of modern growth are found, and along the margin of the lands thus subject to overflow there are numerous recent shells, chiefly of Bulimus.

Between the Gulf coast and Taylor's bayou, and extending north along the west coast of Sabine lake as far as Grigsby's Bluff, and thence in a narrow strip about two miles in width northward along Snow river to a point within four miles of the town of Beaumont, in Jefferson county, there is a tract of low, flat, marshy, sandy land, much broken by lagoons and bayous and smaller marine inlets. This region maintains a growth of marsh plants, and at Grigsby's Bluff as well as several other places along the river contains large deposits of shells of the genus Gnathadon, with occasional oysters.

This has already been referred to the Coast Clays in First Annual Report, page 63, but is here placed with the Recent as being similar to the alluvium of Hilgard and Lockett.

The general facies of the Quaternary deposits are orange, brown, red, yellow and gray sands and loams, occasional deposits of red and yellow clays and silts toward the north, and blue massive and laminated clays in the southeastern portion of the State, ferruginous and siliceous gravels, soft, much broken deposits of ferruginous sandstone, broken monolithic formed bowlders of white and gray sandstone, gravelly and ferruginous conglomerates and highly siliceous iron ores. The maxi- mum thickness of these deposits has been placed at ninety feet, but this thickness exists at only a few places. As a general thing the deposits here classed as Quaternary are thinly and irregularly deposited and rarely exceed ten feet in thickness.

Structurally these Quaternary sands and gravels show a very irregular deposition and many of the sections seen show them to have been subjected to great variations in the conditions under which they were deposited. In places the sands are broken by thin, irregularly deposited fine ferruginous gravel. These gravel deposits usually appear as filling rounded and steep-sided depressions in the finer white or brown sands. Where the iron ore deposits occur the coarser gravels and pebbles show large quantities of ferruginous material throughout them, but away from these points the siliceous pebbles and gravels are the prevailing characteristics of the deposits. The siliceous gravel is very irregular in both extent and thickness, at places reaching from one to two feet in thickness and at others showing no more than a few scattering "

* For other localities in which these shell mounds occur, see First Annual Report of Geological Survey of Texas, p. 64.

I Geol. of Miss., 1863, p. 201.

II Third Annual Report Geological Survey of Louisiana, p. 203.