GNEISSES IN THE HIGHLANDS OF NEW JERSEY 6ii 



injection along parallel layers, and second, by a process of absorp- 

 tion exerted by the original rock upon the injected magma. The 

 latter process will be discussed a little later. 



The nature of the original rock does not appear at all certain. 

 The laminated character might as well be considered as represent- 

 ing bedding planes in a sedimentary series or shear planes in a schist 

 of either sedimentary or igneous origin. The prevalence of ferro- 

 magnesian minerals in many of the bands might be supposed 

 to imply a derivation from a basic igneous rock, but there is a 

 question as to how far the present composition represents that of 

 the original material. The French geologists mentioned have 

 directed special attention to the profound changes wrought in the 

 composition of the original sediments by "imbibition" of material 

 derived from the igneous mass. Sederholm also has described 

 similar phenomena accompanying the process of granitization, and 

 the work of Adams and Barlow' in the Haliburton and Bancroft 

 areas of Ontario is of great importance in this connection. The 

 last-named geologists present evidence of the metamorphism over 

 large areas of the pure, non-magnesian limestones of the Hastings- 

 Grenville series into amphibolites and pyroxene-gneisses by trans- 

 fusion of material from invading batholiths of granite. 



There is some evidence not far distant from the quarries 

 described that not all of the original rocks of the region could have 

 been of a basic igneous character. About two miles (35 kilometers) 

 to the north, a little west of the railway station at Haskell, a bed 

 of crystalline limestone or dolomite occurs in the gneissic series. 

 The thickness is somewhat uncertain but appears to be 20 feet 

 or more. In places the amount of carbonate minerals is large, 

 though tremolite, phlogopite, and a pale-green pyroxene are 

 extensively developed, as well as secondary serpentine. Elsewhere 

 along the same belt carbonates appear to be wholly absent and the 

 rock consists almost entirely of the greenish pyroxene or a mixture 

 of pyroxene and quartz. The belt can be traced by occasional 

 outcrops for several hundred feet. In one place a gneiss com- 

 posed of feldspar, quartz, biotite, and much garnet occupies a 



' Adams and Barlow, "Geology of the Haliburton and Bancroft Areas," Memoir 

 No. 6, Canadian Geological Survey (1910); see especially pp. 87 and 157. 



