PLEISTOCENE MARINE SUBMERGENCE ' 33 



The southern part of Newburgh Hes on the delta of Quassaic 

 creek. The summit plain of the delta is well shown, both on the 

 map and in the field, on both sides of the creek, with an elevation 

 of i6o feet. The broader part of the delta plain is on the south 

 side of the creek, underlain with scores of feet of blue clay. This 

 clay has been extensively excavated along the river south of New- 

 burgh and at New Windsor, and shows the usual succession ; glaci- 

 ated rock and compact till at the bottom, then the thick deposit of 

 finely laminated blue clay becoming yellow toward the top, and a 

 capping of sand and gravel. This will serve as an example of the 

 valley deposits and the record of the succession of events since the 

 ice occupation. The occurrence of huge boulders in the clays is 

 evidence of waters laving the receding ice front. 



Opposite Newburgh is the delta of the Fishkill, the larger part 

 showing on the West Point sheet. The summit plain is on the 

 Poughkeepsie quadrangle and carries the part of Beacon formerly 

 called Fishkill. The altitude of the main street of Beacon is about 

 150 feet, at the west end. The map is wrong in showing the east 

 end higher. 



From Newburgh, or from the river steamers, the plain and 

 terraces of the Fishkill delta are plainly seen. South of Beacon 

 the delta stretches for 3 miles, and at Dutchess Junction and below 

 are extensive brick works. Apparently the southward drift of the 

 waters, aided by exposure to the northerly winds, swept the stream 

 detritus southward. Denning point is a little remnant of the delta, 

 a small imitation of Croton point. 



Poughkeepsie sheet. Northward from Newburgh terraces of 

 gravel and excavations in clay occur at several places. Woodworth 

 indicates them as far as Marlboro (82, plate 5). The terraces have 

 been so mutilated that their original form is uncertain. The ter- 

 race at Roseton, like many that will not be noted, was inferior in 

 altitude, about 100 feet. At New Hamburg is the delta of Wap- 

 pinger creek; but only the lower terraces lie here, for the reason 

 that the summit level of the delta head forms the broad flats extend- 

 ing 2 to 4 miles above Wappinger Falls. A fair terrace and beach 

 along the highway a mile south of New Hamburg, at 175 feet by 

 the map, marks the summit level of the estuary. The smoothing 

 effect of the waves is seen on the weak shales and the silt filling of 

 the hollows west of Wappinger Falls, at about 170 feet. 



East of Marlboro are flat-topped sand hills not properly shown 

 by the map, but of inferior altitude. Northwest of the village, and 

 north of the creek, by the railroad station, is an extensive gravel 



