REPORT OF THE DIRECTOR I9II 25 



.crystalline hills and on the correlation of the Paleozoic stratigraphy 

 with that of New Jersey. This region is one which has been pre- 

 viously studied both in its broader features and in some of its special 

 details but Doctor Kiimmel has brought to his examination of it 

 long and exact acquaintance with the geology of New Jersey along 

 the region of the Appalachian uplifts. Incidentally this work has 

 afforded very considerable data for the areal mapping of the region. 

 Doctor Kiimmel reports as follows : 



Overthriisting of the crystalline rocks. The region south of 

 Greycourt is characterized by a number of isolated masses of gneiss 

 which rise abruptly to notable heights above the surrounding shale 

 country. Northeast of Greycourt is another line of similar hills 

 but less massive and lower than the former. All of these larger 

 gneiss masses have certain topographic features in common which 

 are significant of the structural relations. Both eastward and west- 

 ward slopes are steep and in places even precipitous. On the west 

 the " Hudson River shale " extends part way up the slope and 

 usually forms a narrow shelf along the mountain face. This shelf 

 commonly attains its greatest elevation along the central portion of 

 the hill and declines gently toward the northern and southern ends. 

 Its inner (eastward) margin is marked by outcrops of gneiss usually 

 rising above the shelf as a low ledge, but sometimes forming cliffs 

 thirty or forty feet in height, above which the slope to the summit 

 is more gradual. Toward the northern and southern ends of the hill 

 the bordering gneiss ledge swings eastward as the shelf of '' Hudson 

 River shale " decreases in height. Viewed in profile from the north 

 or south, the contact of the gneiss on the shale and its descent to 

 the east as the end of the hill is approached is clearly shown by the 

 topography. 



The " Hudson River beds " within a quarter of a mile of the 

 contact, dip 30° to 50° to the southeast, i. e. toward the gneiss at 

 angles which accord fairly well with the inclination of the thrust 

 plane. Locally the shale beneath the gneiss is minutely crumpled 

 and contorted, even the finest laminae being closely folded as a 

 result of the lateral compression when it was overridden by the 

 crystalline rocks. The gneiss within several feet of the contact is 

 often greatly crushed and traversed by many minor thrust planes 

 which dip southeast at slightly varying angles. Many of these 

 thrust planes are polished and slickensided. 



The eastward swing of the contact between shale and gneiss with 

 decrease in elevation, the crushed and slickensided condition of the 



