Tectonic Implications of Para- and Orthogneiss Geochronology and Geochemistry from the Southern Appalachian Crystalline Core
Author | : Brendan Richardson Bream |
Publisher | : |
Total Pages | : 592 |
Release | : 2003 |
Genre | : Crystalline rocks |
ISBN | : |
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Author | : Brendan Richardson Bream |
Publisher | : |
Total Pages | : 592 |
Release | : 2003 |
Genre | : Crystalline rocks |
ISBN | : |
Author | : Richard P. Tollo |
Publisher | : Geological Society of America |
Total Pages | : 972 |
Release | : 2010 |
Genre | : Science |
ISBN | : 0813712068 |
"The Appalachians constitute one of Earth's major tectonic features and have served as a springboard for innovative geologic thought for more than 170 years. This volume contains 36 original papers reporting the results of research performed throughout nearly the entire length and breadth of the Appalachian region, including all major provinces and geographical areas. Memoir 206 was designed to commemorate the (near-)fortieth anniversary of the publication of the classic Studies of Appalachian Geology volumes that appeared just prior to the application of plate tectonic concepts to the region. Contributions concerning structural evolution, sedimentation, stratigraphy, magmatic processes, metamorphism, tectonics, and terrane accretion illustrate the wide range of ongoing research in the area and collectively serve to mark the considerable progress in scientific thought that has occurred during the past four decades."--pub. desc.
Author | : Crystal Gayle Wilson |
Publisher | : |
Total Pages | : 219 |
Release | : 2006 |
Genre | : Amphibolite |
ISBN | : |
Author | : Peter J. Berquist |
Publisher | : |
Total Pages | : 182 |
Release | : 2005 |
Genre | : Geological time |
ISBN | : |
Author | : Denny N. Bearce |
Publisher | : Geological Society of America |
Total Pages | : 171 |
Release | : 1982 |
Genre | : Science |
ISBN | : 0813721911 |
Author | : Ann E. Holmes |
Publisher | : Geological Society of America |
Total Pages | : 276 |
Release | : 2015-03-09 |
Genre | : Science |
ISBN | : 0813700396 |
"This volume contains field guides to the 2015 GSA Southeastern Section Meeting's field trips. The guides explore geologic history and visit four regional geologic provinces--the Nashville dome, Blue Ridge, Valley and Ridge, and Cumberland Plateau"--
Author | : Mary Grace Varnell Jubb |
Publisher | : |
Total Pages | : 308 |
Release | : 2010 |
Genre | : Geology, Structural |
ISBN | : |
The Tugaloo terrane in the eastern Blue Ridge, located in the high-grade southern Appalachian crystalline core, contains small internal basement massifs, the Neoproterozoic Tallulah Falls Formation, and Paleozoic granitoid plutons. Detailed geologic mapping in the Lake Toxaway and eastern Big Ridge quadrangles was done to better understand the regional tectonic history. Whole-rock geochemistry was used to determine similarities between the augen phase of the 1.15 Ga Toxaway Gneiss and the 1.15 Ga Wiley Gneiss of northeastern Georgia. The study found that all eastern Blue Ridge orthogneisses are similar and probably share a source. The previously identified Whiteside, Looking Glass, and Pink Beds plutons, and the newly identified Horseshoe Rock and Round Mountain plutons were also characterized. All plutons are low-K, catazonal granodiorites and trondhjemites that plot as volcanic arc or syn-collisional granites on tectonic discrimination diagrams. The Looking Glass, Pink Beds, and Round Mountain plutons were dated using U-Pb SHRIMP zircon geochronology, and their ages are 333 " 16 Ma, 371.3 " 4.2 Ma, and 342.5 " 2.4 Ma, respectively. Zircon saturation temperature estimates for these plutons, and a Whitney and Stormer two-feldspar estimate for the Round Mountain pluton, indicate that they intruded at 700-800° C. Whole-rock geochemistry was used to constrain the origin of amphibolites and hornblende gneisses around the Toxaway dome. One sample was a metabasalt with MORB composition, like other eastern Blue Ridge samples. Two other samples have a metasedimentary protolith. Migmatitic aureoles found in the amphibolite facies rocks around the Whiteside, Looking Glass, and Horseshoe Rock plutons are syn-intrusional and represent a zone of contact metasomatism. The new pluton ages constrain the regional deformation history. At least 6 deformations are recognized in the eastern Blue Ridge. Dominant regional foliation is traditionally attributed to the second event (~466 Ma). However, foliations measured within all plutons are identical to foliations measured in the surrounding rock, indicating that foliations had to form after the youngest pluton intruded (~333 Ma), and that Alleghanian deformation was dominant in this region. These observations do not explain cross-cutting relationships observed around older plutons and raise new questions about southern Appalachian tectonics.
Author | : Benjamin Lee Davis |
Publisher | : |
Total Pages | : 0 |
Release | : 2021 |
Genre | : Geology |
ISBN | : |
Taconic orogenesis along the eastern Laurentian margin was a dynamic tectonic event during the Ordovician that has been difficult to reconcile until as of late. The record of the Taconic orogeny is complex, and each section of the Appalachians has different geologic attributes that are unique to that specific section. In the northern and central Appalachians, the record of Taconic orogenesis is well preserved and understood, but in the southern Appalachians there are discrepancies in subduction style that suggest a different manor of tectonic evolution occurred. The probable model for the southern Appalachians suggests a B-type subduction system, where the Dadeville complex represents a marginal volcanic arc, due to a subduction polarity reversal north of the Virginia promontory, relative to the northern Appalachians during the Taconic orogeny, causing Laurentian continental lithosphere to override subducting Iapetan oceanic lithosphere. This model depicts the fringing Dadeville complex arc and associated Wedowee-Emuckfaw-Dahlonega back-arc basin originating on distended Laurentian crust, fueled by extensional rather than convergent tectonics.The Dadeville complex is a large klippe located in the Alabama and Georgia Inner Piedmont of the southern Appalachian orogen lying immediately above rocks of the eastern Blue Ridge, Brevard Zone, and Opelika Group in the core of the Tallassee/Newnan-Tucker synform. The Dadeville complex consists of an array of metaigneous, metaplutonic, and metasedimentary rocks including the Ropes Creek Amphibolite, a bimodal metabasalt/metatuff, metadacite at the base, overlain by the Agricola Schist, a metaturbidite consisting of metapelite, metagreywacke, and minor metabasalt. The Chattasofka Creek Gneiss (granite) is intrusive into the Agricola Schist, Ropes Creek Amphibolite, and a mafic-ultramafic suite. The Camp Hill Gneiss (tonalite) is intrusive into the Ropes Creek Amphibolite. Also intrusive into the Agricola Schist is a mafic-ultramafic suite consisting of the Doss Mountain and Slaughters Gabbro units. There are a multitude of mafic-ultramafic suites and felsic plutonic rocks in the Dadeville complex that span from Camp Hill, Alabama to southeast Atlanta, Georgia that have been identified over the course of this research. Distinctive major and trace element geochemical signatures of the felsic intrusives, Ropes Creek Amphibolite, and various mafic-ultramafic suites all suggest formation within a volcanic arc environment. U/Pb dating of detrital zircons in the Agricola Schist, and equivalent metasedimentary rocks, as well as igneous zircons in the Chattasofka Creek Gneiss, Camp Hill Gneiss, and Ropes Creek Amphibolite yield Middle Ordovician ages, with the Agricola Schist also containing a subordinate fraction of Grenville and Granite-Rhyolite Province ages. Additionally, the Camp Hill Gneiss, Chattasofka Creek Gneiss, and Doss Mountain and Slaughters Gabbro suites all exhibit negative initial epsilon Nd (ENdi) values indicative of a continental origin. These relationships suggest that the Dadeville Complex volcanic arc, and the associated Wedowee-Emuckfaw-Dahlonega back-arc basin, resulted from a B-type suprasubduction system where Iapetan oceanic lithosphere subducted beneath a distended Laurentian continental plate, and that there could be other Taconic arc fragments in the southern Appalachians, akin to or apart of the Dadeville complex, that have yet to be identified.