GEOLOGY OF THE PORT LEYDEN QUADRANGLE 25 



Lowville limestone 



The Lowville limestone formation takes its name from the 

 type locality at Lowville a few miles beyond the map limits to 

 the northward. It was formerly called the Birdseye limestone 

 because of the spotted character of the surfaces due to the emer- 

 gence of the calcite-filled tubes so characteristic of the formation. 

 These calcite-filled tubes stand perpendicular to the stratifica- 

 tion planes and were first thought to have been caused by a 

 seaweed of the Fucoid type, but they are now referred to the 

 genus Tetradium of the branching corals. Not all of the Low- 

 ville beds contain the Tetradium. 



In the old State report by Vanuxem everything below the 

 Trenton, in this region, was described under the heading '' Black 

 River limestone," but the following quotation shows that, on 

 lithologic grounds, he recognized three divisions of the forma- 

 tion : " The clifif shows several distinct kinds of limestone, not 

 being a homogeneous mass. The upper part is mixed irregularly 

 with black shale. . . The second division is of a lighter 

 color, with less shale or impurities, more brittle, and contains 

 the Fucoides demissus (Tetradium), etc. . . The third 

 division, and which therefore forms the base of the cliff . . . 

 is light colored, and the surface of some of the layers present mud 

 cracks, showing the presence of shale. It is in these layers that 

 the stone exists which is burnt for waterlime at Lowville." ^ His 

 upper division corresponds to our Black River limestone, the middle 

 one nearly to our Lowville, and the lower one nearly to our Pamelia. 



AVithin the map limits the Lowville, together with the Pam- 

 elia, is present, except at the extreme south, as an almost con- 

 tinuous surface exposure or ledge facing the railroad. In spite 

 of its considerable thickness its areal extent is small because 

 of its outcrop along this steep slope. The Lowville beds are 

 mostly bluish dove-colored, pure limestones in beds varying 

 from a few inches to 2 feet thick. Some of the beds are mud 

 cracked, others are shaly, while still others are fossiliferous 

 commonl}' with the Tetradium. A notable feature is the pres- 

 ence of limestone conglomerate at several horizons. In passing 

 downward this conglomerate is prominent where the pure dove 

 limestones give way to the more impure bluish gray to whitish 

 gray limestones and it is here where the line between the Low- 

 ville and Pamelia has been drawn. Within the quadrangle this 

 line is a difficult one to draw with any great degree of accuracy. 



'Geol. N. Y. 3d Dist. 1842. p. 42. 



