400 



Report of the State Geologist. 



gneiss forming Sugar Loaf mountain, and the areas t<> the northeast, is a 

 granulite gneiss with little or no mica or hornblende. 



Bodies of iron-ore are not uncommon and are not confined to any par- 

 ticular area or belt, although future detailed study of these rocks may show 

 that they belong to definite horizons. The ore-bodies are generally of small 

 size, and lens or pod-shaped, and the ore is, in most instances, lean. The two 

 important ore-bodies are those of Forest-of-Dean and Sterling. 



Limestones occur interbedded with the gneiss, but are rare. One bed is 

 found at Popolopen pond, and another at Fort Montgomery. 



The crystalline locks of this region often appear folded and sometimes 

 faulted ; the thin sections do not, however, afford as much evidence of dynamic 

 metamorphism as one might expect. The folds of these Pre-Cambrian rocks 

 frequently pitch to the northeast. Dikes are not infrequently met with. 



In view of the limited extent of our present knowledge, these rocks can 

 only be classed as Pre-Cambrian. This is also suggested by Van Hise. 

 (Bulletin United States Geological Survey, No. 86, p. 415.) 



Cambrian. The rocks of this age are light-colored, generally massively 

 bedded magnesian limestones. No fossils have been found in them, but their 

 age is based on: (1) the similarity of character of the several areas; (2) on 

 their relations to the . overlying formations, and (3) on the occurrence of 

 Cambrian fossils in the limestone of northern New Jersey*, of which they 

 are undoubtedly a continuation. Their greatest development is in the western 

 part of Warwick township, and in Lookout mountain, south of Goshen. The 

 limestones are normally light blue and finely crystalline, but sometimes 

 become coarsely granular, shaly or even brecciated, as east of Goose pond 

 mountain and south of Neelytown. Around Edenville they have been 

 changed by granite intrusions to a coarsely crystalline white limestone. 



In Bellvale and Skunneniunk mountains, the limestones underlie uncon- 

 formable the younger formations, while north of Greenwood lake and east of 

 Pine hill they are faulted against the gneisses, and the same relations hold 

 tine at Snake hill southwest of Newburgh. In the northeastern part of the 

 county they are faulted against the Hudson river slates. 



The thickness of the Cambrian limestones in ( ) range county can not be 

 determined with accuracy, but it is probably not less than 500 feet. In 

 Lookout mountain, south of Goshen, they have a thickness of about 200 feet. 



Trenton Limestone. There is a small, highly fossiliferous area of this 

 rock on the River road, about two and three-quarters miles north of Newburgh 



* A. F. Focrxte.— American Journal of Science, December 1H!I3, p. 435. 



