l6 SMITHSONIAN INSTITUTION 



Stratigraphy is the study of the superposition of sedimentary rocks 

 and their contained organisms. Not less important to the modern 

 geologist than the sequence of rock layers is the interpretation of 

 sedimentary environments and paleo-ecology as indicated by the na- 

 ture of the rocks. Thick-shelled clams and brachiopods in ripple- 

 marked, often cross-bedded sands indicate a near-shore zone; plant 

 fragments, tree stumps, and fresh-water clams indicate land environ- 

 ments — deposits in rivers or estuaries. From Lake Erie eastward 

 the Hamilton sediments are those of a shallow sea, and from Unadilla 

 Valley eastward the character of the faunas and sediments alike indi- 

 cate close proximity to an ancient shore. Schoharie Valley is clearly 

 the shore region of the ancient Devonian sea. Here continental beds 

 alternate with strata laid in marine water. Variable east-west develop- 

 ments of the beds indicate an oscillating shore. In Schoharie Valley 

 the lower and middle Hamilton rocks arc of the two types, continental 

 and marine, but the upper Hamilton is mostly continental, containing 

 sizeable tree stumps in their original position of growth. East of 

 Schoharie Valley the upper two thirds of the Hamilton is composed 

 nearly completely of red rocks, the origin of which is a moot question. 



In order to ascertain the time of deposition of the red beds it was 

 necessary to bud fossils in them whose age could be definitely de- 

 termined. Fortunate was the writer to be able to trace a single marine 

 layer of the upper Hamilton from Susquehanna Valley to Durham, 

 into the midst of the red beds. Heretofore all red beds in eastern New 

 York were regarded as Upper Devonian in age, but the results of the 

 present studies prove that some 2,000 feet, at least, of the red beds of 

 the Catskill Mountains belong to the time of Hamilton deposition. 



The geography and stratigraphy of the Flamilton rocks of eastern 

 New York having been briefly described, the ancient conditions can be 

 pretty safely restored. In Devonian days the site of Schoharie Valley 

 was the shore region of the Devonian sea. Southeast of Schoharie 

 were forests of huge and peculiar types of ferns, and off to the west 

 of the site of the valley was the sea with its hordes of strange shelled 

 invertebrates. So far as known huge and bizarre types of fishes were 

 the only vertebrate life of the waters, and majestic crustaceans of 

 scorpionlike form were the rulers of forest and river. 



The stratigrapher, using fossils as the key to his vertical and geo- 

 graphic position in the rocks, is keenly interested in discovering a 

 maximum number of specimens. These Devonian field studies 

 brought to the United States National Museum a rich supply of 

 specimens, many new to our collections and some new to science. 



