H. T. CRESSON A BURIED FOREST IN DELAWARE. 641 



At Philadelphia the Trenton gravel lies near the Delaware river, enveloped by older 

 gravels rising but a few feet above its waters. It is not so coarse as at Trenton, and 

 south of Philadelphia forms a fine river gravel and sand, difficult to trace in places, 

 and often reappearing in deposits of considerable thickness. It will not be necessary 

 to say an3'thing more upon the geological disposition of the aqueous gravel at Phila- 

 delphia and Trenton, already so well described by competent authorities upon the sub- 

 ject, but special attention is directed to a point just across Mason and Dixon's line, on 

 the headwaters of Naaman's creek, near Claymont, Delaware. 



It is not our intention to enter into a controversy in regard to the age of the geo- 

 logical deposits lying around the site of the prehistoric stations in northern Delaware, 

 but rather to call the attention of scientists to interesting facts in regard to the super- 

 position of the ancient aqueous deposits in that vicinity. Along the Delaware river 

 at Claymont, in Newcastle county, we find extending backward in a northwesterly 

 direction toward Elam and the hills on the Bradywine creek a series of enormous 

 benches marking diflferent periods of erosion ; and these are thinly covered by old 

 river gravels and clays resting upon pre-glacial deposits, supported by beds of decom- 

 posed schistose rock. These aqueous deposits are the Philadelphia red gravel and 

 brick-clay of Lewis and Wright, similar to those underlying the city of Philadelphia 

 and its immediate vicinity, classed by McGee as part of the Columbia formation. It 

 is in all probability an aqueo-glacial formation of an earlier date than the Trenton 

 gravels, and has been connected (by Professor G. F. Wright) with the ice when at its 

 maximum extension and the level of the region was depressed one hundred feet or 

 more. Authorities upon the subject who have examined this deposit agree that it is 

 evidently older than the deposits farther up the valley at Trenton, New Jersey. 

 Since, as already suggested, implements of stone worked by early man have been 

 found in the gravels covering these benches, their relation to the Trenton gravels will 

 be an exceedingly interesting study. 



Eastward toward the Delaware river, on the lowest bench, we find that the Phila- 

 delphia brick-clay predominates in thickness over the red gravel, and that the bowlder 

 clay in certain places rests upon a gray plastic clay, probably of lower Cretaceous or 

 Wealden age, as we find it further northward. Six to twelve miles further south- 

 ward beyond Wilmington the trend of the Cretaceous may be marked as it cuts 

 across Delaware in a southwesterly direction from the state of New Jersey toward the 

 Maryland line. 



Interspersed between layers of Philadelphia red gravel and brick-clay at various 

 depths are organic remains, consisting of branches of oak, sycamore, willow and pine 

 trees, which I have designated as the " fallen forests and peat layers." Within a 

 radius of several miles from Carpenter station, east, west, north and south, we have 

 this peculiar evidence of a quite recent disturbance. Some of the organic material is 

 well preserved ; even the leaves of the trees composing it can be recognized. In 

 places the peat layer comes to the surface of the ground, as at Lobdell's car-wheel 

 works, near the mouth of Christiana river toward the southwest, but this may be the 

 result of the disappearance by erosion of formerly overlying layers. Excavations at 

 Lobdell's works indicated that the peat layers also dip beneath clay and alluvial de- 

 posits from the Delaware ; and in this connection it may be stated that traces of man's 

 presence were found beneath the alluvial deposits, intermingled with and on top of 

 the peat bed. At liichmond's brick yard, mouth of Naaman's creek, we find this 

 same peat layer, rising to the surface on one side of the creek ; and on the north side 

 it is found beneath 10 to 18 feet of Philadelphia brick-clay rcsling on red gravels 



