46i T. G. Brown — Shawangunk Conglomerate. 



Art. XXXIX. — The Shawangunk Conglomerate and Asso- 

 ciated Beds near High Falls, Ulster County, Neiv York ;* 

 by Thomas C. Brown. 



In several recent papers the Shawangunk conglomerate and 

 the overlying shales and sandstones (Longwoocl shale of New 

 Jersey and High Falls shale and Binnewater sandstone of New 

 York) have been described as continental, flood plain, or tor- 

 rential deposits, f While employed by the New York City 

 Board of Water Supply during the preliminary surveys and 

 early construction work for the Catskill Aqueduct across the 

 Rondout Yalley, the writer had exceptional opportunities to 

 studjr these beds in numerous diamond drill cores and in the 

 five shafts which penetrated them and exposed the section 

 complete in its natural unweathered condition. Several of the 

 observations made upon them under those conditions do not 

 agree with the published descriptions, nor do some of them 

 conform to the theory of continental origin. It, therefore, 

 seems advisable to publish these observations so that other 

 workers interested in this problem may study the above men- 

 tioned papers with these facts before them. 



Historical sketch. — The Shawangunk conglomerate of Ulster 

 county and the associated beds of red and green shale lying 

 between this and the limestones and cement beds of the Upper 

 Silurian were recognized and described by Mather in his 

 geology of the First New York District (pp. 353-355). He 

 even gives a detailed section with measurements of the beds at 

 " High Falls on the Rondout in Marbletown, Ulster county," 

 the exact location where the studies for this paper were com- 

 menced. Mather did not definitely correlate these beds with 

 their western equivalents. He closed his discussion thus : 

 " The observations made do not render it certain whether these 

 red rocks are equivalent to the Onondaga salt group or the 

 Medina sandstone ; but it is thought probable, from some of 

 the mineral characters, no fossils having been seen, that they 

 belonged to the epoch of the, Medina sandstone, and that the 

 subjacent Shawangunk grit is equivalent to the gray sandstone 

 [Oswego] instead of the Oneida conglomerate."^: 



* The writer is greatly indebted to J. Waldo Smith, Chief Engineer of the 

 New York City Board of Water Supply, for permission to use the figures 

 from the official records in this paper, and also to L. White, Division 

 Engineer, under whose supervision he was working while collecting these 

 data. 



fGrabau, A. W., Jour, of Geol., vol. xvii, pp. 245-246, 1909; Bull. Geol. 

 Soc. Amer. , vol. xxiv, pp. 472-496, 1913 ; Principles of Stratigraphy, pp. 

 377, 596, 636, 1913. 



X Geology of New York, First District, p. 355, 1843. 



