GEOLOGY OF THE LUZERNE QUADRANGLE 39 



exposure probably occurs. Over the whole area there are a great 

 many angular fragments of gray sandstone and gray sandy dolomite 

 up to I and 2 feet in diameter. If none of the rock is not now 

 really in place it certainly was just before the Ice Age. In any 

 case the ledges were much broken up by the passage of the ice. 



Three small exposures of Upper Cambrian strata were observed 

 within the small area 2^4 miles northwest of Hartman. Two of 

 these occur by the roadside where the rock is seen to be well- 

 bedded, gray, sandy dolomite with a few intercalated layers of 

 light-gray sandstone a few inches thick. Each exposure shows a 

 thickness of only 5 or 6 feet. These outcrops lie at the base of a 

 steep slope of syenite, the dolomite having there been faulted down 

 against the syenite. Only one very small outcrop, showing a thick- 

 ness of about 2 feet was seen east of the road but its relation to 

 the other exposures makes it probable that a thickness of at least 

 20 to 25 feet of strata are represented in this area. 



Age and Significance of the Strata 



Although no fossils were observed in them, the sandstone and 

 dolomite strata of the three areas quite certainly belong to the Pots- 

 dam-Theresa series of Upper Cambrian age in northern New York. 

 According to Cushing : ^^ " Everywhere in New York where the 

 Potsdam sandstone formation occurs, it is united with the (Little 

 Falls) formation next above, usually a dolomite formation, by a 

 series of intermediate or passage beds (Theresa formation) which 

 consist of alternating sandstone, calcareous sandstone, and dolo- 

 mite. . . . The sandstone is in excess in the lower part of the 

 formation, and the dolomite in the upper. Deposition was appar- 

 ently continuous but physical conditions slowly changed, the sand 

 supply from the Adirondack land slowly diminishing and finally 

 being entirely cut off. Because of this it is impossible sharply to 

 delimit the (Theresa) formation, either at the base or summit." In 

 the largest of the three areas of the Luzerne quadrangle both the 

 Potsdam and Theresa quite certainly show in outcrop, but in the 

 two smaller areas Theresa only shows, though the Potsdam almost 

 certainly lies underneath. 



The three small bodies of early Paleozoic strata within the 

 Luzerne quadrangle are really outliers, that is, they represent 

 erosion remnants of a vast sheet of early Paleozoic strata which 

 once overspread the whole southeastern Adirondack region, includ- 

 ing the area of the Luzerne quadrangle. A few years ago the writer 



" N. Y. State Mus. Bui. 169, 1914, p. 35. 



