Hershey.] The River Terraces of the Orleans Basin 



441 



the channel at a height of at least 260 feet above the river. 

 There is from five to fifteen feet of moderately fine river gravel, 

 overlaid by twenty feet of finely stratified, non-pebbly sandy 

 silt bed contained driftwood, flattened by pressure. Some 

 of this was secured and forwarded to Mr. Diller, and ultimately 

 reached Professor Penhallow. Mr. Wilder states that he found 

 many fine impressions of leaves on the thin layers of silt, 

 particularly in a light colored stratum. He identified the leaves 

 of alder and a tree locally known as pepperwood. Mining has 

 destroyed this fossiliferous bed, and no specimens of the leaf 

 impressions could be secured. Over the silt there is at least 150 

 feet of light gray stratified slate debris, a remnant of an alluvial 

 cone formed at the mouth of a neighboring gulch. The strata 

 as well as the surface slope distinctly toward the river. The 

 nearly flat surface has an extent of four or five acres, but the 

 channel remnant is known to be much larger. 



The characteristics of this Wilder Mine are almost identical 

 with those of the Ferris Mine, and I would not hesitate to class 

 them as remnants of the same channel and its deposits if it were 

 not for the superior height of the former. I will later develop 

 the probability of a differential uplift of the region, but the 

 difference of level between the two mines is so great that I 

 am constrained to consider the Wilder channel as a slightly 

 earlier member of the same group as the Ferris channel. 



Opposite the Wilder Mine a long narrow strip has been mined 

 off as the Yellow Jacket Mine. The bed-rock floor seems to be 

 of sufficient height above the river to indicate the lower of 

 the two main channels buried under the "120-foot terrace." 



The 70-Foot Terrace.— Outside of the 120-foot terrace of the 

 Markusen Mine there may have been a lower terrace which has 

 been practically mined off and the original surface nowhere 

 remains. The rim of the channel has a level of seventy-five feet 

 above the river and the channel behind may be fifteen feet 

 deeper. It is possible that this belonged to the 120-foot terrace. 

 Outside of the rim there is a narrow strip of gravel resting on 

 bed-rock at forty to forty-five feet above the river, and this 

 probably represents the seventy-foot terrace. In proceeding 

 downstream it becomes a distinct channel remnant several acres 



