REPORT OF THE STATE PALEONTOLOGIST 1002 



1033 



picted in their proper relation, he having added to those recog- 

 nized by Davis, the Schoharie, the Port Ewen and the Oriskanv, 

 the latter formation having been discovered by Beecher and 

 Smock at Becraft in 1890. 1 



No attempt was made by Clarke to depict the minute details 

 of the distribution of the formations, nor to map the compli- 

 cated structure. The latter could be worked out only by a 

 minute following of the outcrops over the entire field, and by 

 a careful determination of the beds in isolated outcrops. For 

 the latter work, paleontologic data had to be relied on fully 

 as much as lithic characters, since the latter are often nearly 

 identical in distinct horizons. 



The desirability of a carefully constructed map of Becraft 

 mountain has long been felt, not only on account of the inter- 

 esting stratigraphic as well as tectonic features, which throw 

 light on the problem of Appalachian stratigraphy and struc- 

 ture, but also on account of the fact that Becraft mountain 

 forms an ideal region for field work with students in geology. 

 Being isolated from the rest of the Helderbergs and of conveni- 

 ently small size, it presents a problem of proper circumscrip- 

 tion to enable something like completion to be attained by the 

 students in the field. Its range of strata, with their well pre- 

 served fossils, most of which are limited to few or only one 

 of the horizons; the various complications by folds and faults 

 of several ages, together with all the more prominent tectonic 

 features accompanying them, and the interesting stream ad- 

 justments and other physiographic features, make this an 

 almost unrivaled field for classwork. Recognizing this fact, 

 Dr John C. Smock, of Hudson, had constructed a detailed 

 topographic map of the region, on the scale of 6 inches to the 

 mile, and with contour intervals of 10 feet. This map has 

 served as the basis of the accompanying geologic map, which 

 was prepared under the auspices of Prof. John M. Clarke, the 

 state paleontologist, and with the partial cooperation of stu- 



1 Beecher, C. E. Xotice of a New Lower Oriskanv Fauna in Columbia County, 

 New York, with an annotated list of fossils by J. M. Clarke. Am. Jour. Sei. 

 1897. 44:410-14 



