THE TIMBER BELT OR SABINE RIVER BEDS. 27 



The base of the Tertiary part of this bluff is composed of black clay from 

 the water edge up to ten feet above it, and is overlaid by six feet of non-fos- 

 siliferous greensand marl. The Quaternary deposit lies unconformably on 

 the Tertiary strata. It is to be seen at many points along the river from 

 Falls County down, and is doubtless the representative of an old river silt 

 formation. For twelve miles below this point is seen a series of interbed- 

 ded and interlaminated clays and sands,* with occasional beds of lignite, and 

 some few small gray calcareous concretions. Frequently small fragments of 

 lignite are seen in the sand beds, showing that the swifter waters, which 

 changed the character of the bed from clay to sand, were also responsible for 

 the destruction of lignite beds, the fragments of which were deposited with 

 the sand. 



In the northern corner of Burleson County, and two and a half miles below 

 where the north boundary of the county crosses the Brazos, is seen the first 

 fossil- bearing stratum that has been met along the river below the Basal Clays. 

 Here is found a bluff, about thirty-five feet high, giving the following section: 



BURLESON SHELL BLUFF. 



1. Fossiliferous greensand marl 10 to 20 feet. 



2. Interbedded and interlaminated dark brown and black clays and sands... . 8 feet. 



3. Lignite 2 feet. 



4. Gray sand 3 feet. 



5. Interbedded and interlaminated dark brown and black clays and sands 



to water edge 4 feet. 



Dip of the above section, 3 degrees southeast. 



The greensand marl is rusty and indurated in places, and in others retains 

 its green color. It contains a few gray calcareous concretions, one to three 

 inches in diameter, and is often literally made up of fossils. One mile below this 

 point the same bed is seen dipping under the water level. For six miles be- 

 low this point is seen a series of interbedded and interlaminated sands and 

 clays, often much colored by lignitic matter, "and containing thin seams of 

 woody lignite. The sands are much cross-bedded, and contain considerable 

 quantities of iron pyrites. The dip is irregular and undulating, frequently 

 tending toward the north. Six miles below Burleson Shell Bluff we come to 

 Moseley's Ferry (San Antonio Ferry), where we again find glauconitic de- 

 posits rich in fossils. These are twelve feet thick and underlaid near the 

 water edge by a chocolate brown clay containing gray calcareous concretions. 

 The greensand marl is rusty and indurated in places, soft and green in others. 



*By this expression "interbedded and interlaminated clays and sands " is meant that some- 

 times the clays and sands are in alternating beds, several inches or several feet in thickness, 

 and at other times they are in thin laminae, ■£% to £ inch in thickness. This is a very common 

 occurrence in the "Timber Belt Beds." (See foot note, p. 24.) 



