1	Regional Geology of Southeastern New York State A Pictorial Field Guide
2	Regional Geology of Southeastern New York State Although the crust at present is relatively stable in all of New York State, many areas of our state show dramatic evidence that this hasn’t always been true. Preserved in the rocks of New York is proof of a long and complex geological history.
3	Our trip route
4	Atlantic Coastal Plain Plainedge Middle School is located on an outwash plain deposited by 4 or 5 glacial advances during the 300,000 to 600,000 years of the Pleistocene Epoch. The last glacier left Long Island only about 20,000 years ago!!!
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6	As we head north for our journey, looking west across the Hudson River is a spectacular sight -- The Palisades Cliffs
7	Palisades Cliffs
8	"The Palisades are an igneous..." The Palisades are an igneous intrusion called a sill Sills form when magma cools between sedimentary rock layers All the fractures give the basalt sill a fence-like look
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11	View to the south from the top of Bear Mountain in the Hudson Highlands of the Hudson River
12	Bear Mountain State Park Storm King Granitic Gneiss
13	Bear Mountain was also glaciated. Chatter Marks indicating the flow of ice from the N-NW to the S-SE Chatter marks result when large boulders carried by the retreating ice mass, chip the surface. Years and years of weathering have failed to erase the geologic record left by glaciers.
14	Skunnemunk Conglomerate An ERRATIC carried by a glacier from Skunnemunk Mtn. located 30 miles north of Bear Mountain.
15	View of the Hudson River from the top of Bear Mountain Across the river is a Peak called Anthony’s Nose. Anthony’s Nose is composed of amphibole Gneiss – A metamorphic Rock.
16	The Hudson River was a U-shaped valley eroded by glaciers below sea level and then flooded by the Atlantic Ocean.
17	Mr. Orgonik and Mrs. Wells enjoying the view
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19	The Hudson-Mohawk Lowlands At the beginning of the Ordovician (about 458 mya) the Taconic Mtns to the east were formed. During the late Ordovician, as these mountains were weathered and eroded, sediments were deposited in horizontal layers Outcrop of Normanskill Shale
20	Normanskill Shale
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22	Shawangunk Ridge The SHAWANGUNK RIDGE is a narrow, steep cliff that is part of the Appalachian Fold Belt that extends from Georgia to New York. The shale layers forming the foundation were horizontally deposited during the Ordovician. Subsequent deformation, submergence, and then deposition of sand and quartz pebbles during the Silurian and early Devonian eventually formed the rock referred to as SHAWANGUNK CONGLOMERATE The layer of shale is over 2,000 ft. thick, while the overlying quartz conglomerate is only a few hundred feet in thickness.
23	Shawangunk Ridge Conglomerate
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25	Glaciers shaped the basin of Lake Minnewaska Cliffs of Shawangunk Conglomerate
26	Closer look at the quartz conglomerate layers that form beds
27	During the last 1million years, glaciers have advanced and retreated over the region several times leaving evidence of glacial polishing, striations, and chatter marks clearly visible on the quartz conglomerate of the Shawangunks
28	Pebbles in the quartz conglomerate No fossils are present in these Silurian Rocks
29	Awosting Falls Largest Falls in the Shawangunks Cross bedding of sandstone layers is evidence that an ancient river system carried sand along the bottom forming small ripples and dunes underwater
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31	Rosendale Cement Mines Traveling back through the Hudson-Mohawk Lowlands we stopped at an abandoned and flooded cement mine. New York’s architectural history was built with cement from Rosendale. The high-quality dolostone was processed into cement in local kilns. The cement was used to build the Brooklyn Bridge and the pedestal of the Statue of Liberty. The mines operated from l825 to the l950’s. The pillars are dolostone and the roof of the mine is limestone.
32	Entrance to Rosendale Cement Mine
33	Pillars - Dolostone, Roof - Limestone
34	Our trip route
35	Taconic Unconformity Law of Original Horizontality – layers of rock are deposited in a flat-lying position. When you see rock layers tilted, something must have disturbed them after they were deposited. (Taconic Orogeny) Rock layers of Ordovician age were deposited, tilted, then eroded. Subsequent deposition of Silurian age rock layers were deposited on top. The surface that separates the younger layers from the older layers represents a gap in time called an unconformity. Finally, the entire rock formation was tilted to its present position.
36	Formation of an angular unconformity
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41	A model of the Helderberg Escarpment at John Boyd Thatcher State Park
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43	Helderberg Escarpment at John Boyd Thatcher State Park
44	15 different formations of marine limestone laid down give the escarpment a layered look
45	"Many famous scientists studied the..." Many famous scientists studied the Helderberg Escarpment in the early 1800’s. Amos Eaton – father of American Geology Sir Charles Lyell – Uniformitarianism Louis Agassiz – coined the term “Ice Age” James Hall –father of American Paleontology
46	The Indian Ladder Trail constructed in l828 descends from the top of the escarpment to the base of the Devonian limestones and then back up Thick and more massive layers of Coeymans limestone that project outward from the cliff face above the thinner Manlius limestone layers.
47	"Another look at the Manlius..." Another look at the Manlius limestone showing the very thin, wavy beds of carbonate mud. The thicker Coeymans limestone represents a different environment of formation.
48	"Almost everywhere," Almost everywhere, bedrock is cut through by systems of fractures called JOINTS. Joints typically occur in parallel and intersecting planes, creating zones of weakness. Joints important weathering of rocks because they admit water to the rock. Almost everywhere, bedrock is cut through by fractures called JOINTS. Joints typically occur in parallel and intersecting planes, creating zones of weakness along which weathering can act. Joints are important to the physical weathering of rocks because they admit water to the rocks.
49	"Mr." Mr. Orgonik is trying to stop the physical weathering process.
50	Underground streams and caves form as slightly acidic rain water seeps into the joints of limestone eventually dissolving passages
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52	Minelot Falls
53	Tentaculitid fossils (.5 cms.) in Manlius Limestone – Devonian Age (400mya)
54	Tentaculites gyracanthus
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56	Coeymans Limestone containing crinoid stem fragment
57	Coeymans Limestone –younger than Manlius Limestone (Law of Superposition) containing many brachiopods and crinoids.
58	Mudcrack in Manlius Limestone – indicating a shallow environment that periodically dried out the carbonate mud.
59	"You have seen landscape features..." You have seen landscape features that span 2 extremes in Geologic History: from the Pleistocene Epoch only about 1 million years ago to the Precambrian 1.1 billion years ago Preserved in the rocks is the story of New York’s geologic record