20 SMITHSONIAN INSTITUTION 



Ithaca division of the Upper Devonian. The writer was interested 

 chiefly in the Middle Devonian and the lower Upper Devonian, the 

 times during which the Hamilton Group and Tully formation were 

 deposited, the latter overlying the former. 



Although the structure of the Hamilton Group is simple the de- 

 tailed stratigraphy is more difficult. As a whole the group is a great 

 wedge of clastic rocks less than 300 feet thick at Lake Erie but in- 

 creasing to an unknown thickness, probably exceeding 2,500 feet in 

 eastern New York. In western New York much of the lower part is 

 a black shale denoting near-shore conditions of a peculiar kind and 

 containing a peculiar fauna. Toward the east these black shales are 

 replaced by mudstones and sands and the peculiar black shale fauna 

 gives way to large species which inhabited the active shore zone. In 

 other words, as one travels eastward in following the Hamilton across 

 the State, he leaves an old land on the site of the present Lake Erie and 

 approaches the shoreline of the old continent of Appalachia which 

 lay southeast of New York. Between the two lands was the open sea 

 which trapped the sediments. 



The village and township of Hamilton are in a critical geographical 

 position as regards the stratigraphy of the Hamilton Group, lying in 

 the area where there is a notable change from characteristic marine 

 conditions to the close-shore region. Still farther east, in the vicinity 

 of Albany and Catskill, the upper part of the Hamilton has been 

 replaced by continental beds. 



A fourfold division of the Hamilton rocks from the bottom up is 

 recognized : Marcellus, Skaneateles, Ludlowville, and Moscow. In the 

 region visited the first formation is composed of black shales which 

 cover the hilltops in the northeastern part of the Morrisville quad- 

 rangle and form the bottom of the Chenango Valley as far south- 

 ward as the village of Hamilton. The Skaneateles division underlies 

 the villages of Cazenovia and Morrisville, and in Chenango Valley 

 extend to the south margin of the Morrisville sheet. The succeeding 

 divisions cover the southern portions of Cazenovia and Morrisville 

 quadrangles and the northern one-third of the Norwich area. 



The numerous ravines and quarries around Cazenovia, Morrisville, 

 and Hamilton are delightful collecting grounds, yielding a great va- 

 riety of fossils. For the most part the entombed animals are inverte- 

 brates. Most numerous are the clams occurring in great numbers and 

 representing nearly 150 species. Second in point of numbers and 

 species are the brachiopods. Other divisions of the invertebrates are 

 present but less numerous. The fossils occur usually in the form of 

 external and internal impressions, as the actual substance of the shell 

 has been dissolved away by surface waters. 



