Paleontology and geology
The Precambrian: Precambrian rocks are exposed in the Adirondack region of New York. These rocks are mainly metamorphic and igneous and contain few fossils.
The Paleozoic: Paleozoic rocks are well represented in the state of New York. During the late Cambrian and Ordovician, sea level rose, covering the state with a shallow sea. Cambrian sedimentary rocks are preserved in patchy areas around the Adirondack Dome in northeastern New York. Ordovician rocks are more extensively exposed around the state. Fossils of trilobites, brachiopods, clams, and other marine organisms can be found in these rocks. Late in the Ordovician, an episode of mountain building (the Taconic Orogeny) buckled the crust and raised mountains in what is now southeastern New York. These mountains had eroded away by the Silurian, and sea level had dropped. The sea covering the western part of the state had become extremely shallow and salty, and rapid evaporation led to the formation of Silurian-age salt deposits. Marine fossils can be collected from Silurian rocks exposed between Lake Ontario and the Finger Lakes region.
Devonian-age sedimentary rocks are exposed in central and southern New York. Mountains formed by the Acadian Orogeny during this time eroded rapidly, providing huge amounts of sediments to rivers and streams. This sediment was deposited on the Catskill Delta and into the inland ocean to the west. Plant fossils indicate that some of the earliest forests flourished on the delta sediments. Erosion has removed all Carboniferous and Permian rocks in New York.
The Mesozoic: There are very few Mesozoic rocks exposed in New York. Rift basins formed along the margin of North America during the Triassic/Jurassic as the supercontinent Pangea broke apart. The reddish-brown sedimentary rocks and basalt resulting from these tectonic activities can be seen in a few localities in the far southeastern part of the state. Cretaceous sediments of the Coastal Plain Province can be seen on Long Island. Many Cretaceous deposits had not yet been cemented or compacted into rock and were eroded from highlands to the west and transported by rivers to the coast.
The Cenozoic: Most Tertiary sediments deposited from the newly uplifted Adirondacks were scraped up by Pleistocene glaciers and pushed south. Thus, the Cenozoic is represented in New York mainly by Quaternary sediments. A series of terminal moraines and other Quaternary glacial deposits across New York record the repeated advances and retreats of enormous ice sheets across the state. The ice sheets also helped to shape the topography and drainage characteristics of New York today, including the Finger Lakes. Recent Quaternary deposits also make up most of the sediment adjacent to modern estuaries and streams.