112lect28 - GY 112 Lecture Notes D. Haywick (2006) 1 GY 112...

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GY 112 Lecture Notes D. Haywick (2006) 1 GY 112 Lecture Notes The Appalachian Mountains Lecture Goals : A) Back to Newfoundland B) The major orogenies (eastern North America) C) Other Orogenies (Antler, Ouachita) Textbook reference: Levin 7 th edition (2003) Chapters 8 & 9; Levin 8 th edition (2006) Chapters 10 & 11 A) Back to Newfoundland When last we met, we discussed my old study area in Newfoundland. In the Stratigraphic sketch that I drew in class, I commented that the vertical succession recorded a relatively sharp transgression. The Lower Ordovician rocks that I was studying (the St. George Group) were deposited in shallow marine environments but they were overlain by deeper water limestones and shales. “ The bottom fell out of the depositional environment ” is how I explained the transgression. Well as it turns out, if you went north of my study area, you would find that atop the shales, there is a fault (a thrust fault for those of you who have already taken GY 111), and above the fault, there is an impressive “slab” of peridotite, gabbro and pillow basalts These are volcanic rocks and they do not belong in a sedimentary succession. They are actually a slice of oceanic crust which we call an ophiolite suite. The succession of Ordovician and older rocks that are visible in western Newfoundland are classic and reflect the onset of tectonics responsible for the Appalachian Mountains. There were at least 3 pulses of mountain building. That means 3 major orogenies. B) The Major Orogenies Boy, there was a lot going on during the Paleozoic in Laurentia. The Appalachian Mountains suffered 3 distinct pulses of mountain building (or orogenies). The first which was the one responsible for emplacing the ophiolites in western Newfoundland is called the Taconic Orogeny . It most affected the area from western Newfoundland down to about New York State, but recent work now shows that there are elements of the Taconic
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GY 112 Lecture Notes D. Haywick (2006) 2 Orogeny much further south (e.g., Georgia). In the south, Taconic events mostly involved intrusions (e.g., plutons composed of granite). In the north, there were also significant compressional events (e.g., thrust faulting). It is now believed that the Taconic Orogeny and the deformation that occurred with it was induced by the collision of an island arc complex with eastern Laurentia. The complex was produced through the subduction of
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This note was uploaded on 02/04/2012 for the course GLY 112 taught by Professor Haywick during the Spring '12 term at S. Alabama.

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112lect28 - GY 112 Lecture Notes D. Haywick (2006) 1 GY 112...

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