I. INTRODUCTION A significant portion of New England was formed as a result of an accretionary orogen. Southeastern New England is marked by a series of terranes that accreted onto the Laurentian supercontinent during the Silurian and Devonian. The Terranes of Gander, Nashoba, Avalon, and Meguma are present from west to east in eastern Massachusetts and all of are Gondwanan provenance. Their modern-day juxtaposition suggests that the marginal Gondwanan micro-continents collided sequentially from west to east, expanding the Laurentian continent with each respective collision. As each subsequent plate collided, an intervening subduction zone died and a new subduction zone was created to the east. The oblique collision of the Avalon Terrane into Laurentia followed the accretions of the Gander and Nashoba Terranes and preceded the accretion of Meguma. The collision was marked by uplift, mylonitic metamorphism, and calc-alkaline Nashoba plutonism as the Iapetus Ocean subducted under the Nashoba and eventually the Avalon collided obliquely into the continental margin. The area composed of the Gander, Nashoba, Avalon, and Meguma Terranes has been extensively studied for many years. However, it was only recently that the terranes were recognized as distinct geologic entities with unique tectonic histories thus there is still much debate regarding the tectonic model which brought these terranes together (Hon et al., 2007). This paper will address the geology of the peri-Gondwanan terranes and propose a potential tectonic model for the accretional orogenic events. It will also primarily focus on the juxtaposition between the Nashoba and Avalon Terranes. II. TECTONIC SETTING Global Tectonics The most recent complete supercontinent cycl... ... middle of paper ... ...J.C. (2004) Mylonites and Brittle Shear Zones Along the Western Edge of the Avalon Terrane West of Boston, NEIGC Field Trip Guide. Marshak, S. (2009) Essentials of Geology, 3rd ed. New York: W.W. Norton & Company, ch. 11, p. 298-320. Skehan, J.W., Rast, N., Kohut, E., Hepburn, J.C., and Grimes, S.W. (1998) Precambrian and Paleozoic Mylonites of the Boston Avalon, NEIGC Field Trip Guide. Stroud, M.M., Markwort, R.J., and Hepburn, J.C. (2009) Refining Temporal Constraints on Metamorphism in the Nashoba Terrane, Southeastern New England, Through Monazite Dating. Lithosphere, vol. 1, p. 337-342. Van Staal, C.R., Whalen, J.B., Valverde-Vaquero, P., Zagorevski, A., and Rogers, N. (2009) Pre-Carboniferous, Episodic Accretion-Related, Orogenesis along the Laurentian Margin of the Northern Appalachians. Geological Society, London, Special Publications, vol. 327, p. 271-316.
The shelf-edge includes carbonate-to-clastic facies transition and tectonic uplift and erosion of the carbonates followed by deposition of the clastics. The Saint Peter Sandstone is a well-sorted, almost pure quartz arenite deposited during a major mid-Ordovician low stand. Clastics spread across an exposed carbonate platform by transportation. This is shown by the well-rounded, frosted texture of the quartz grains.
The site visited on this day was informally known as the Bedrock Knob (NTS grid reference: 120 342). It is in an area where patches of limestone and exposed bedrock are common. The bedrock is part of the Preca...
Ŝibrava, V., Bowmen, D.Q., and Richmond, G.M, 1986, Quaternary glaciations in the northern hemisphere; report of the International Geological Correlation Programme, Project 24 (International Union of Geological Sciences and UNESCO): Pergamon Press, Oxford, New York, 514 p.
...the only major geologic event in the history of the Appalachians. Several glaciers have covered parts of the Northern Appalachians over the last three million years. (Appalachian tales) The mountains have been there ever since and that is how they were formed.
Ehlen, Judy, and R.C. Whisonant. 2008. "Military geology of Antietam battlefield, Maryland, USA—geology, terrain, and casualties." Geology Today 20-27.
Although New England and the Chesapeake region were both settled largely by the people of English origin, by 1700 the regions had evolved into two distinct societies. The reasons for this distinct development were mostly based on the type on people from England who chose to settle in the two areas, and on the manner in which the areas were settled.
and Metamorphic rocks can be found. There are also a lot of crusted plates, and violent
The sharp differences in elevation between the Badwater Basin and the surrounding mountains that include the highest point in the continental US (Mt. Whitney at 14,494 feet) stand as a representation of the regions violent tectonic past. The mountains themselves are considered fault block mountain ranges meaning that they were formed when blocks of rocks were squeezed through the Earth's crust along parallel faults or were loosened from the crust when it separated at a fault. In the valley, both of these methods not only were the cause of the current mountains formation less than four million years ago, but also are causing the mountains to be uplifted while the valley floor drops even further. This phenomenon is one of the reasons why the lowest and highest points in the continental...
Morton, J. W. (n.d.). Metamorphosed melange terrane in the eastern piedmont of north carolina. Retrieved from http://geology.geoscienceworld.org/content/14/7/551.abstract
During the Jurassic period, Pangea began to break up and by the time of the Late Cretaceous, ~94 Mya, the Atlantic Ocean began to open and Pangea continued to break apart. Due to this breakage of continents, there were extreme volcanic activity and much evidence can be seen of this all around the world today. In Anglesey, there are many igneous dykes and sills that have intruded older rocks that have been dated back to this time. This movement of continents continued into the Cenozoic era which is the current and most recent geological era consisting of the past 65 million years. It was during this time that Anglesey reached its current, present day
Anatolian is a region in Turkey where vast amount of tectonic activity which was followed by magmatism took place during the Cenozoic era. The Anatolian microplate is bound to the north by the Mediterranean Sea, to the east by the Red sea and, to the south by the Aegean Sea. Ophiolites and suture zones seperate different pieces of continental blocks that came together to form the Anatolian microplate (Altunkaynak et al. 2012). Chorowicz (1999) defines Anatolia as a product of the African and Eurasian plate collision which formed mainly from lithospheric magma. A widespread of magmatism accompanied plate tectonism experienced in this region during the Cenozoic era. The late Eocene (37.3 ± 4.6, measure through K-Ar radiometric dating) marks the initial period where this magmatism in took place. This essay will establish if whether an East-west spatial control on the chemistry of Anatolian volcanics exists.
Miesse, Willian C. "Mount Shasta Geology and History." USGS: Volcano Hazards Program - Mount Shasta Geology and History. College of the Siskiyous Library, n.d. Web. 01 May 2014.
P.Wellman, Ian McDougal,(1974),Cainozoic igneous activity in Eastern Australia, Research School of Earth Sciences, ANU Canberra, Elsevier Scientific Publishing Company,pg 52
Smithsonian National Museum of Natural History (2014). Burgess Shale Fossil Specimens. Retrieved May 2014, from http://paleobiology.si.edu/burgess/burgessSpecimens.html
inferred for the reservoir (4). The magma ascent to the surface occurred through a conduit of possibly 70 to 100 m in diameter (5). A thermal model predicts that such a reservoir should contain a core of partially molten magma (6) that can be detected by high-resolution seismic tomography.