306 THE IRON ORE DISTRICT OF EAST TEXAS. 



TERTIARY. 



With the exception of the ores the highest bed of the Tertiary which is 

 exposed here is the bed of the greensand immediately underlying the iron 

 ore beds. This varies in thickness from ten to forty feet, and "is composed 

 of glauconitic grains with more or less green clay, the latter often occurring 

 in the form of interbedded seams or lenticular patches. This bed is usually 

 rusted upon the surface from the combined decomposition of the glauconite 

 and iron pyrites which it contains, but the interior preserves its green color. 

 It contains many fossils of the Claiborne forms, generally as casts, but some- 

 times well preserved Oblong and kidney-shaped calcareous nodules, varying 

 in size from one-half inch to three inches in diameter, are sometimes found, 

 but are somewhat rare." This bed forms the divide between the Trinity and 

 Neches rivers, and occupies some of the highest points in the northern part 

 of the county. Immediately underlying this bed there is a series consisting 

 of interbedded and interlaminated sands and clays, often cross-bedded, 

 stained by decomposed iron pyrites, and containing numerous small beds of 

 lignite. "These sands are frequently indurated by a ferruginous or siliceous 

 cement into beds of sandstone varying very much in hardness, color, and 

 thickness. Such beds vary from one to twenty feet in thickness and are of 

 very limited extent. They generally cap knolls and hills, and forms a pro- 

 tecting cover which saves the underlying strata from erosion." 



At the base of these sands are found purplish and chocolate colored sands, 

 stratified horizontally, and containing specks of mica and gray sandy clays 

 with fragments of lignite. Crystals of selenite are found in many parts of 

 them. These beds are exposed by erosion of the upper greensands and by 

 various wells that have been dug or bored on the east and south, and cor- 

 respond in their general features very closely with the beds of the same hori- 

 zon described in other localities of this East Texas region. 



One peculiarity worthy of note in the greensand marl is the occurrence of 

 lines of the material in indurated concentric nodules. These are present in 

 many places, and an analysis shows a much larger percentage of ferric oxide 

 in them than in the massive material in which they occur, and they are seem- 

 ingly continuations of the processes by which some of the iron, ores have 

 been formed. 



The following special sections will serve to illustrate more fully the general 

 stratigraphy of the Tertiary. 



The Oil Wells Section. — Ten miles east of Palestine, in the neighborhood 

 of Still's Creek, several borings were made for oil in 1887. The road from 

 Palestine to the wells shows, first the greensand bed underlaid by the white, 

 red, and other lignitic sands and clays. Below these were found purplish and 

 chocolate colored sands, stratified horizontally, and containing mica. These 



