140 ir. B. Dwight — Recent Explorations in the 



miles north, of Poughkeepsie. It is the object of this paper to 

 present a few of the prominent results of my more recent 

 researches in the Cambrian and associated strata in that part of 

 the county adjacent to Stissing Mountain. 



The particular aim of these later investigations has been to 

 ascertain the position and extent of the Olenellus strata, and 

 their stratigraphic relations to the Hudson River shales of the 

 region, and to the higher Cambrian strata whose presence a 

 few miles to the southward had been already demonstrated. 



The Olenellus quartzite and the overlying Olenellus lime- 

 stone, rest upon the gneiss of Stissing .Mountain around the 

 entire circuit of its southern extremity and so continue north- 

 eastward for several miles along both its eastern and western 

 flanks. At the southern extremity, about 21 miles northeast- 

 erly from Poughkeepsie, these strata cover the basal slopes of 

 the mountain at an elevation of about 275 feet above the 

 adjoining valleys and, conforming to these slopes, lie with 

 a very gentle inclination to the south. On descending the slopes 

 in southerly directions, the upper layers of the Olenellus lime- 

 stone are found to run frequently into red shales which have 

 not proved fossiliferous. In the fields which stretch southward 

 and southwestward from the mountain, the rocks are to a great 

 extent concealed by drift ; but there are a sufficient number of 

 outcrops to permit a continuous tracing of the limestones and 

 calcareous shales (of whatever horizon they may be) for several 

 miles, and to show that the dip rapidly increases, and the strike 

 soon becomes the prevailing one of about N. 20° to .30° E. 

 On account of the cover of drift, and the scarcity of fossils, it 

 is at present impossible to determine exactly, along what lines 

 the Olenellus group is succeeded by strata of later periods. 



This mass of limestones of the Olenellus and to the south- 

 ward probably of higher groups, which extends in the line of 

 strike southwestward, is abruptly cut off on the west by a fault 

 caused by the uplift of a belt of Olenellus quartzite, overlain 

 on the west by a strip of limestone of the same age. West of 

 this limestone are the shales of the Hudson River group. This 

 fault begins at a point between two and three miles southwest 

 of Mt. Stissing, where, however, only the limestone at first 

 appears, faulting on the east (as well as the west) against Hud- 

 son River shale. This line of fault extends in a direction a lit- 

 tle east of north to western flank of the mountain. One of the 

 best places to observe it is one mile west from Stissing Station, 

 on the road leading west beyond the corner of the Mclntyre road, 

 near Mr. Elias Turner's house. At this point the quartzite 

 comes in, as a bold conspicuous ledge of white unfossiliferous 

 rock. From this point northeastward, the quartzite faults 

 against the Olenellus and associated limestones on the east, while 



