REPORT OF THE STATE GEOLOGIST. XXXvii 



fication of the surrounding beds is seemingly repeated in them, and 

 they gradually blend into the soft encircling sand. In places they ap- 

 pear as detached masses, at others form almost a solid stratum. This 

 calcareous cement is occasionally replaced by a firm impalpable white 

 clay, which when wet renders the beds highly plastic, but dries into a 

 firm and solid mass. From the manner of their formation, the sand 

 beds themselves lack that continuity and persistency which we find in 

 the similar rocks of the older formations, and there is every evidence that 

 they were deposited under very similar conditions to those which exist 

 to-day upon the Gulf coast. Indeed, the entire series of Tertiary and 

 Post-Tertiary strata may well be called littoral or shore deposits, show- 

 ing in their variations changes from open sea shore to bays and lagoons, 

 with alternations of tide and flood and standing water, of peat bog and 

 dry land. Not only are these conditions shown by the character of the 

 sediments themselves, but the extensive deposits of fossil shells found 

 here and there in them, often separated by beds of lignite, furnish ad- 

 ditional evidence that such were the conditions of their deposition. 

 For this reason the graduations from sand to clays, and to sands again, 

 both vertically and laterally, prevent the correlation of the beds at any 

 distance, and render it difficult even when they are close to each other. 



The clay beds which appear in the Timber Belt differ greatly in 

 purity and color. Some are pure white, from which they are found in 

 all colors, to brown and even black when the quantity of lignitic mat- 

 ter they contain is sufficiently great. They rarely appear massive, as 

 in the upper beds, but are more usually thinly laminated, and often 

 contain lenticular masses of sand scattered through them with consid- 

 erable regularity of deposition. 



The lignite is not in continuous beds, as is the case with the coal of 

 the Carboniferous Period, but in lenticular beds of greater or less ex- 

 tent. It varies from a lignitic clay to a quality closely approaching a 

 bituminous coal. In places it carries little or no sulphur, in others the 

 amount of pyrites contained in it entirely unfits it for any use. The 

 quantity of good lignite, however, is very great, although little effort 

 has as yet been made to use it. 



Iron is found in three forms throughout the Timber Belt Beds — -com- 

 bined with sulphur, in the form of pyrites, it is found in larger or 

 smaller quantities in all parts of the beds, and thus has had its share in 

 producing the workable iron ores of Eastern Texas, as will be stated later. 

 Carbonate of iron, or clay-iron stone, occurs in masses under similar 



