NO. lO SECOND REPORT ON FOLSOM COMPLEX ROBERTS IT, 



of deposition by water. No information was obtained to indicate what 

 agency was responsible for the original scouring of the valley and 

 removal of material down to the Oligocene stratum or when such 

 action took place. After the abandonment of the location by its human 

 inhabitants, material from the higher levels was washed down across 

 the site. The first layer to be deposited consisted of stained sand and 

 earth, presumably occupation level material from the upper slopes. 

 This in turn was covered by sand, gravel, and boulders swept down into 

 the valley from its bordering hills. Then the alternating periods of 

 erosion and building up set in as demonstrated in the lower sections of 

 the trenches. As previously stated, all of this change could not have 

 been extremely rapid here because ridges which contributed to some 

 of the valley fill have since completely disappeared, being weathered 

 away in the opposite direction. Furthermore, there are good indica- 

 tions that the central portion of the valley, which lies to the north of 

 the ravine and the archeological site (map i), now consists of secon- 

 dary fill. The material which raised the old bottom to the level repre- 

 sented by that above the deep pit was subsequently washed away and 

 the area again built up with sand, gravel, and rocks carried down from 

 the ridges to the west and north of the site. That the original fill, 

 represented by the deposit above the deep pit and the artifact bearing 

 stratum in the area crossed by the trenches, was not disturbed may be 

 attributed to the fact that it was far enough up the opposite slope to 

 escape forces at work on the floor of the valley. This feature is one, 

 however, which belongs more properly in Dr. Bryan's discussion of the 

 geology of the site and will not be considered further at this point. 

 The geologic report will appear in a later publication on the work at 

 the site. 



THE BISON PIT 



The excavation where the bison bones were uncovered measured 

 20 feet (6.096 m) by 47 feet (14.326 m) (map i). Owing to erosion 

 by wind and water, as mentioned in an earlier paragraph, the deposit 

 was not as deep as in the area where the trenches were dug. The 

 bones ranged in depth from 1O7 inches (26.67 cm) at the upper side 

 of the pit to 3 feet (.914 m) below the surface along the lower side. 

 The position of the strata here differed slightly from that observed 

 in the main trenches. The object-bearing layer did not consistently 

 follow the clay substratum. It rested upon a l)ed of stained sand 

 and earth which in turn lay directly on the clay. A wholly satisfactory 

 explanation for this condition was not obtained from the digging. The 

 best suggestion which can be offered at this time is that the i)articular 

 2 



