34 ROLLIN T. CHAMBERLIN 



CORRELATION OF CREEK-BOTTOM SECTION WITH UPLAND SECTION 



For the complete history of the district it is necessary to cor- 

 relate the creek-bottom section with the upland, pr country, 

 section. The coquina is common to both and serves as a base of 

 reference. If we turn to the upland section as it is developed just 

 west of the junction of the two forks of Van Valkenburg's Creek, 

 we observe that the most striking feature there shown is the almost 

 perfectly black, indurated sand bed, or sandstone, which forms 

 a persistent layer, in places capped by peat, beneath the surficial 

 wind-blown sands. If the creek deposits were younger than 

 the induration of this sandstone, evidence of such relative age might 

 well be found in the incorporation of derivatives from the black 

 sandstone in the creek deposit, for, if the age and induration were 

 considerable, the sandstone should have been of sufficient hardness 

 to supply the two forks of the creek with pebbles and cobbles of 

 this very easily recognizable material. Now an inspection of the 

 freshly cleaned face of Dr. Sellards' formation No. 2 — the critical 

 formation — reveals the presence in it of many small pebbles, and 

 not a few round "cannon balls," of this black sandstone (see Fig. 

 8). The latter range up to 5 inches in diameter. They are not 

 confined to any one layer, but are scattered through No. 2 forma- 

 tion from top to bottom. Thus the formation in which the human 

 bones and the extinct vertebrate remains were found also contains 

 numerous pebbles and cobbles of black sandstone from the older 

 formation! The stream which deposited formation No. 2 formed 

 these pebbles of black sandstone by erosive action on stratum b of 

 the upland section, through which both the north fork and the 

 south fork of Van Valkenburg's Creek have obviously cut their 

 stream channels. This black layer underlies apparently all the 

 country immediately to the west of the spillway; it is a continuous, 

 persistent layer; it was traced in situ to within 150 feet of where 

 the human remains were found, and with further digging it could 

 probably be traced still nearer. There is no other known source 

 for the pebbles of black sandstone. The conclusion seems, there- 

 fore, inevitable that Dr. Sellards'' formation No. 2 is younger than 

 stratum b of the upland section — the old bog surface upon which the 

 peat accumulated. Furthermore, it would seem to be considerably 



