62

GENERAL GEOLOGY.

The geological section of the county shows great stretches of recent alluvial deposits extending along the rivers and covering an area along the Brazos from two to four miles in width. Small patches of quaternary sands and gravels are found overlying the higher lands among the ridges. In the south and southeast the greensands and marls of the Moseley ferry and Wheelock sections predominate, and in the central and northern areas the Eocene lignitic and basal beds constitute the characteristic strata.

The general section shows the following approximate thickness of the several deposits:

RECENT.

A considerable extent of Recent deposits occurs along the western border of the county, comprising the region lying between the two rivers, the Brazos and the Little Brazos, and occupying an area from two to four miles in width, extending from Brazos county on the south to Falls on the north. The structure of these deposits, where undisturbed, is to a great extent laminated. Deposits of brown clays and sands, in laminæ having an irregular thickness and no perceptible dip, form the great bulk of these beds. In close proximity to the Brazos river the clays are scarcely represented, and the alluvium is made up chiefly of brown river silts or fine sands, having occasional small pockets or thin sheets of a coarse sand or fine gravel.

The structure can best be seen in the sections obtainable at various places along the Brazos river. A section seen on the river six miles southwest of Calvert shows:

1. Brown sandy soil ............................................ 1 to 2 feet.

2. Old humus, showing thin seams of brown sand interlaminated with the black soil ........................................ ½ to 1 foot.