Illustration of the Taconic orogeny

The Taconic orogeny was a great mountain building period that perhaps had the greatest overall effect on the geologic structure of basement rocks within the New York Bight region. The effects of this orogeny are most apparent throughout New England, but the sediments derived from mountainous areas formed in the northeast can be traced throughout the Appalachians and midcontinental North America. Download high resolution version (448x780, 28 KB)United States Geological Survey figure of the Taconic orogeny Source URL: http://vulcan. ... Download high resolution version (448x780, 28 KB)United States Geological Survey figure of the Taconic orogeny Source URL: http://vulcan. ... The New York Bight is a large gulf on the Atlantic Ocean along the coast of North America in the northeastern United States. ... Orogeny is the process of mountain building, and as such is both a tectonic structural event, a geographical event and a chronological event, in that orogenic events happen within a time frame, affect certain regions of rocks and crust, and cause distinctive structural phenomena and related tectonic activity. ... This article is about the region in the United States of America. ... The Appalachian Mountains are a system of North American mountains running from Newfoundland and Labrador, Canada to Alabama in the United States, although the northernmost mainland portion ends at the Gaspe Peninsula of Quebec. ...

Beginning in Cambrian time, about 550 million years ago, the Iapetus Ocean began to grow progressively narrower. The weight of accumulating sediments, in addition to compressional forces in the crust, forced the eastern edge of the North American continent to fold gradually downward. In this manner, shallow-water carbonate deposition that had persisted on the continental shelf margin through Late Cambrian into Early Ordovician time, gave way to fine-grained clastic deposition and deeper water conditions during the Middle Ordovician. Sometime during this period a convergent plate boundary developed along the eastern edge of a small island chain. Crustal material beneath the Iapetus Ocean sank into the mantle along a subduction zone with an eastward-dipping orientation. Partial melting of the down-going plate produced magma that returned to the surface to form the offshore Taconic island arc. By the Late Ordovician, this island arc had collided with the North American continent. The sedimentary and igneous rock between the land masses were intensely folded and faulted, and were subjected to varying degrees of intense metamorphism. This was the final episode of the long-lasting mountain-building period referred to as the Taconic Orogeny. The Cambrian is a major division of the geologic timescale that begins about 542 ± 1. ... The Iapetus Ocean was an Ocean that existed in the Southern Hemisphere between Scotland, England and Scandinavia between 400 and 600 million years ago. ...  Sediment  Rock  Mantle  The global continental shelf, highlighted in cyan The continental shelf is the extended perimeter of each continent, which is covered during interglacial periods such as the current epoch by relatively shallow seas (known as shelf seas) and gulfs. ... The Ordovician period is the second of the six (seven in North America) periods of the Paleozoic era. ... In plate tectonics, a convergent boundary (convergent fault boundary, convergent plate boundary, or active margin) is where two tectonic plates slide towards each other and usually collide forming either a subduction zone with its associated island arc or an orogenic belt and associated mountain range. ... Categories: Geology stubs | Plate tectonics ...

When the Taconic Orogeny subsided in the New York Bight region during Late Ordovician time (about 440 million years ago), subduction ended, culminating in the accretion of the Iapetus Terrane onto the eastern margin of the continent. This resulted in the formation of a great mountain range throughout New England and eastern Canada, and perhaps to a lesser degree, southward along the region that is now the Piedmont of eastern North America. The newly expanded continental margin gradually stabilized. Erosion continued to strip away sediments from upland areas. Inland seas covering the Midcontinent gradually expanded eastward into the New York Bight region and became the site of shallow clastic and carbonate deposition. This tectonically-quiet period persisted until the Late Devonian time (about 360 million years ago) when the next period of mountain-building began, the Acadian orogeny. Disambiguation: Devonian is sometimes used to refer to the Southwestern Brythonic language, and the people of the county of Devon are sometimes referred to as Devonians The Devonian is a geologic period of the Paleozoic era. ... The Acadian orogeny is a middle Paleozoic deformation, especially in the northern Appalachians, between Alabama and Newfoundland. ...

Aftermath of the Taconic Orogeny

As the Taconic Orogeny subsided in early Silurian time, uplifts and folds in the Hudson Valley region were beveled by erosion. Upon this surface sediments began to accumulate, derived from remaining uplifts in the New England region. The evidence for this is the Silurian Shawangunk Conglomerate, a massive, ridge-forming quartz sandstone and conglomerate formation, which rests unconformably on a surface of older gently- to steeply-dipping pre-Silurian age strata throughout the region. This ridge of Shawangunk Conglomerate extends southward from the Hudson Valley along the eastern front of the Catskills. It forms the impressive caprock ridge of the Shawangunk Mountains west of New Paltz (town), New York. To the south and west it becomes the prominent ridge-forming unit that crops out along the crest of Kittatinny Mountain in New Jersey. The Silurian is a major division of the geologic timescale that extends from the end of the Ordovician period, about 443. ... For the magazine, see Hudson Valley (magazine). ... Severe soil erosion in a wheat field near Washington State University, USA. For erosion as understood by materials science, see Erosion (materials science) For erosion as an English analogy, see Erosion (figurative) Erosion is the displacement of solids (soil, mud, rock and other particles) by the agents of wind, water... Red sandstone interior of Lower Antelope Canyon, Arizona, worn smooth due to erosion by flash flooding over millions of years Sandstone is a sedimentary rock composed mainly of sand-size mineral or rock grains. ... A conglomerate with iron oxide cementing material A conglomerate (IPA: ) is a rock consisting of individual stones that have become cemented together. ... There is a billion year gap in the geologic record where this 500 million year old dolomite lies on 1. ... Goldenville Strata exposed at a quarry in Bedford, Canada. ... Catskill State Park as seen from Overlook Mountian The Catskill Mountains are an extension of the Appalachian Mountains into New York State. ... Shawangunk Ridge from south of New Paltz, N.Y. The Shawangunk Ridge (also known as the Shawangunk Mountains, or The Gunks; pronounced by some locals as SHONG-gum, (/ˈʃɑŋgʌm/)) is a ridge of mountains in Ulster County, Sullivan County and Orange County in the state of New York, extending... New Paltz is a town in Ulster County, New York, USA. The population was 12,830 at the 2000 census. ... Delaware River Valley and Kittatinny Mountain Region The Kittatinny Mountains are a long ridge across northwestern New Jersey and eastern Pennsylvania. ...

Through Silurian time, the deposition of coarse alluvial sediments gave way to shallow marine fine-grained muds, and eventually to clear-water carbonate sediment accumulation with reefs formed from the accumulation of calcareous algae and the skeletal remains of coral, stromatoporoids, brachiopods, and other ancient marine fauna. The episodic eustatic rise and fall of sea level caused depositional environments to change or to shift laterally. As a result, the preserved faunal remains, and the character and composition of the sedimentary layers deposited in any particular location varied through time. The textural or compositional variations of the strata, as well as the changing fossil fauna preserved, are used to define the numerous sedimentary formations of Silurian through Devonian age preserved throughout the region. Alluvium is soil land deposited by a river or other running water. ... Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. ... Marine is an umbrella term for things relating to the ocean, as with marine biology, marine geology, and as a term for a navy, etc. ... Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. ... A reef surrounding an islet. ... Subclasses Alcyonaria Zoantharia See text for orders. ... Families See text. ... Subphyla and classes See Classification Brachiopods (from Latin bracchium, arm + New Latin -poda, foot) make up one of the major animal phyla, Brachiopoda. ...

See also

• Ebenezer Emmons, the geologist who first described the Taconic system

Ebenezer Emmons (1800-1863), American geologist, was born at Middlefield, Massachusetts, on the 16th of May 1800. ...

External links

• http://3dparks.wr.usgs.gov/nyc/valleyandridge/valleyandridge.htm (public domain source)
• http://3dparks.wr.usgs.gov/nyc/highlands/highlands.html (public domain source)