28 ROLLIN T. CHAMBERLIN 



with the scattered bones of many extinct vertebrates, as main- 

 tained in the previous paper. It is, therefore, the critical formation 

 of the section, and upon its age and mode of origin the case of 

 Pleistocene man stands or falls. 



Above formation No. 2, and, at most points, sharply separated 

 from it by a clear-cut line of erosion, is an alluvial deposit, forma- 

 tion No. 3 of Sellards. This is composed of swamp muck in many 

 layers, interstratified with layers and lenses of coarse sand. Its 

 top is the present flood-plain surface of Van Valkenburg's Creek. 



INTERPRETATION OF THE CREEK SECT [ON 



Following the deposition of the marine coquina, a withdrawal 

 of the sea gradually brought this region into the horizon of terres- 

 trial action. In the transition, beach conditions prevailed, result- 

 ing in sandy deposits, partly marine, partly terrestrial. These 

 finally gave way to eolian sands. An interval of unknown duration 

 followed. At some later time a stream occupying essentially the 

 same course as that which, just prior to the construction of the 

 canal, was followed by Van Valkenburg's Creek excavated a 

 channel which, in some places, was cut through into the coquina. 

 The notable width of this channel in proportion to its very shallow 

 depth — which was limited by sea-level — -suggests that erosive 

 action was in progress for a considerable time at least. But as 

 Dr. Sellards has remarked, tidal scour may have been an acces- 

 sory factor in the development of the breadth of the channel. 

 There are today in the strip of coast between Sebastian and Eau 

 Gallie several such broad, shallow channels up which the tide runs. 

 But if tidal scour is appealed to, it must be interpreted so as to 

 be consistent with the fact that there were deposited in the Vero 

 channel, not only muck and washed sands, but also human bones, 

 together with many scattered bones from a variety of extinct 

 vertebrates. The interpretation must also be in harmony with the 

 specific fact that the human bones were found to be notably less 

 scattered and fragmentary than the bones of the extinct verte- 

 brates. 



Some erosion of the surface of this No. 2 formation seems 

 clearly to have occurred, since its upper surface is a sharp line, 



