640 TROCEEDINGS OF WASHINGTON MEETING. 



A FALLEN FOREST AND PEAT LAYER UNDERLYING AQUEOUS DEPOSITS 



IN DELAWARE. 



BY HILBORNE T. CRESSON. 



Since the announcement that paleolithic implements have been discovered in post- 

 glacial deposits at Trenton, New Jersey, by Dr. C. C. Abbott and other distinguished 

 scientists, the attention of geologists has been drawn to these gravels, and they have 

 endeavored to ascertain approximately the relative geological time in which they 

 were deposited. It is not the intention of the author of this paper to make more than 

 a brief allusion to archeological details, simply referring to those indications of early 

 man's piesence that have an intimate relationship with the various geological deposits 

 which are to be discussed. Further southward, in the lower portion of the Delaware 

 valley, aqueous deposits of a less recent origin than those of Trenton have also yielded 

 rude stone implements of quartz, quartzite, and argillite, the two former materials 

 predominating over the latter. In this connection, it must be said that Dr. Abbott 

 and his son, Richard Abbott, since the discovery of paleoliths at Carpenter station, 

 on the Baltimore and Ohio railroad, near Wilmington, Delaware, have likewise found 

 implements of stone flaked by the hand of man in the older geological deposits at 

 Trenton, upon which lie the post-glacial gravels in which their first important finds 

 were made. 



A few remarks upon the aqueous deposits at Trenton will be necessary, together 

 with a brief description of the somewhat older formations at and for some distance 

 south of Philadelphia, so that the exact geological position of the organic remains 

 denominated the "fallen forest and peat layer," underlying the Philadelphia brick- 

 clay and gravels on Naaman's creek, may be more easily understood. 



It will hardly be necessary to recall that at Trenton we find a well known glacial 

 deposit bearing the name of that place, and that it is generally a horizontal deposit of 

 sand and gravel confined to the flat borders of the Delaware river, resting within 

 channels cut through the Philadelphia brick-clay, lying upon a narrow belt of steeply 

 inclined gneissic rocks, Triassic shales, and Cretaceous plastic clay. Overlooking the 

 level plain are hilltops on which appear older yellow and red gravels and the brick- 

 clay just referred to. The yellow gravel of these hilltops, probably the remains of 

 some old Tertiary sea, covers nearly the whole of southern New Jersey and a portion 

 of Pennsylvania, and may even, we think, be traced into certain portions of northern 

 Delaware. It is composed of water- worn pebbles of quartz and quartzite, with occa- 

 sional pebbles of flint and a fossiliferous hornstone and chert. Resting upon this 

 yellow deposit is a more recent gravel, the Philadelphia red gravel, generally confined 

 to the immediate vicinity of the Delaware valley. Highly colored by rich peroxides 

 of iron, it forms a striking contrast to the more clayey yellow gravel just mentioned. 

 It lies at a lower level than the other gravel, is stratified, and contains smooth, water- 

 worn pebbhs. Resting upon the red gravel is the Philadelphia brick-clay already 

 referred to, generally of a yellow color, but varying somewhat in this respect at 

 places as we approach Mason and Dixon's line. It is a bowlder clay lying within a 

 fixed limit of 150 to 180 feet above the Delaware river. Where the clay and gravel 

 are present it rests upon the red gravel in depressions and on slight elevations. In 

 northern Delaware it is much less stony than at Trenton, and still further northward, 

 near the terminal moraine, it contains so many stones that it might readily be mis- 

 taken for true glacial till. 



