48 KEW" YORK STATE MUSEUM 



portion of the Adirondacks. But, after making every possible allow- 

 ance for the former extension of Ordovician strata (since removed 

 by erosion) into the Adirondack region, we are forced to conclude 

 that the central Adirondack area never became submerged under 

 the Ordovician sea. Furthermore, in northern New York there are 

 known to have been various oscillations of level bringing the dis- 

 tricts around the persistent central Adirondack dry land now above, 

 and now below, sea level on one side or another. Omitting such 

 details, however, we may say that, except for the Adirondack 

 island, northern Xew York was mostly below sea level during the 

 Ordovician period. 



Surrounding the Adirondacks, the principal Ordovician for- 

 mations include the Bcckniaiifozcn, Clia:::y, Black River and Trenton 

 limestones overlain by the Trenton {CaiiajoJiaric), Utica, Frank- 

 fort and Sclienectady shales and sandstones. It should be made 

 clear, however, that these formations are not all present in unbroken 

 succession all the way around the Adirondacks, because the oscilla- 

 tions of level above mentioned occasioned certain interruptions in 

 the deposition of the strata. These rocks are all typical marine 

 deposits, well stratified, in nearly horizontal position and rich in 

 organic remains. They are the old sea limes, muds and sands which 

 have merely been hardened. The fact that the earlier formations 

 are all limestones indicates relatively clearer ocean waters for that 

 time because the nearest lands were small and low, but in the later 

 Ordovician. muds and sands were washed in from higher, reele- 

 vated, adjacent lands. 



In the strata of Cambrian age in northern New York, animal or 

 plant remains (fossils) are comparatively rare, while the Ordo- 

 vician rocks throughout fairly teem with fossils. If any formation 

 deserves special mention, it is the Trenton limestone which is 

 exceedingly rich in fossilj. The type locality, at Trenton Falls in 

 Oneida county, is justly famous as a collecting place for Ordovician 

 fossils. As already stated. Trenton strata occur in the valley at 

 "Wells (Hamilton county) fully 15 miles within the southeastern 

 Adirondacks and the.^e rocks contain numerous fossils. Among 

 plants, none above very simple seaweeds are known to have existed. 

 Among animals, hundreds of species have been described as occur- 

 ring within the Ordovician strata of northern New York. These 

 species represent all the more important classes of animals below 

 the vertebrates. Especially prominent are corals, graptolites, 

 echinoderms (so-called star fishes), brachiopods. gastropods and 



