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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Emerson Fault (1)
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North America
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Appalachians
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Blue Ridge Mountains (5)
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Blue Ridge Province (2)
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Carolina slate belt (8)
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Piedmont (14)
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Southern Appalachians (13)
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Valley and Ridge Province (1)
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United States
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Alabama
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Cherokee County Alabama (1)
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Chilton County Alabama (6)
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Clay County Alabama (6)
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Cleburne County Alabama (3)
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Coosa County Alabama (6)
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Shelby County Alabama (2)
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Talladega County Alabama (5)
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Blue Ridge Mountains (5)
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Eastern U.S.
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Southeastern U.S. (1)
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Georgia
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Bartow County Georgia
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Cartersville Georgia (1)
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Cherokee County Georgia (2)
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Paulding County Georgia (1)
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Polk County Georgia (1)
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Great Smoky Fault (1)
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North Carolina
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Chatham County North Carolina (1)
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Cherokee County North Carolina (1)
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Moore County North Carolina (1)
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Pine Mountain Window (1)
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South Carolina (4)
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Talladega Front (18)
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Tennessee (3)
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commodities
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andalusite deposits (1)
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barite deposits (1)
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kyanite deposits (1)
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metal ores
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copper ores (3)
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gold ores (1)
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iron ores (1)
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manganese ores (1)
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molybdenum ores (1)
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polymetallic ores (1)
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pyrite ores (1)
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tungsten ores (1)
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zinc ores (2)
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mineral deposits, genesis (2)
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mineral resources (1)
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elements, isotopes
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isotope ratios (1)
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isotopes
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radioactive isotopes
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Sm-147/Nd-144 (1)
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stable isotopes
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Hf-177/Hf-176 (1)
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Nd-144/Nd-143 (1)
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Sm-147/Nd-144 (1)
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metals
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hafnium
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Hf-177/Hf-176 (1)
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rare earths
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neodymium
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Nd-144/Nd-143 (1)
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Sm-147/Nd-144 (1)
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samarium
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Sm-147/Nd-144 (1)
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fossils
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Invertebrata
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Archaeocyatha (1)
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Echinodermata
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Crinozoa
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Crinoidea (1)
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Porifera (1)
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microfossils
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Conodonta (1)
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Plantae
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Pteridophyta
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Lycopsida (1)
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geochronology methods
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Rb/Sr (1)
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U/Pb (5)
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geologic age
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Paleozoic
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Cambrian
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Lower Cambrian
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Chilhowee Group (2)
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Murphy Marble (2)
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Shady Dolomite (3)
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Carboniferous
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Mississippian (3)
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Pennsylvanian (1)
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Devonian
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Lower Devonian (1)
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lower Paleozoic (3)
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middle Paleozoic
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Hillabee Chlorite Schist (2)
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Ordovician (5)
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Permian (1)
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Silurian (3)
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Talladega Group (10)
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Precambrian
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Eocambrian (1)
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Great Smoky Group (1)
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upper Precambrian
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Proterozoic
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Neoproterozoic
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Walden Creek Group (1)
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igneous rocks
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igneous rocks
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plutonic rocks
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diorites
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quartz diorites (1)
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gabbros (1)
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granites (1)
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granodiorites (1)
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volcanic rocks
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basalts
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tholeiitic basalt (1)
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pyroclastics (2)
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metamorphic rocks
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metamorphic rocks
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metaigneous rocks
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metadacite (1)
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metasedimentary rocks
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metachert (1)
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metavolcanic rocks (8)
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phyllites (3)
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quartzites (1)
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schists
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greenstone (4)
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slates (1)
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turbidite (1)
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minerals
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silicates
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orthosilicates
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nesosilicates
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zircon group
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zircon (3)
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sheet silicates
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pyrophyllite (1)
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sulfides (3)
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Primary terms
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absolute age (5)
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barite deposits (1)
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crust (1)
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deformation (2)
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economic geology (3)
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faults (11)
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folds (4)
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foliation (1)
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geochemistry (7)
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geochronology (2)
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igneous rocks
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plutonic rocks
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diorites
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quartz diorites (1)
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gabbros (1)
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granites (1)
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granodiorites (1)
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volcanic rocks
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basalts
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tholeiitic basalt (1)
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pyroclastics (2)
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intrusions (2)
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Invertebrata
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Archaeocyatha (1)
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Echinodermata
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Crinozoa
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Crinoidea (1)
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Porifera (1)
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isotopes
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radioactive isotopes
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Sm-147/Nd-144 (1)
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stable isotopes
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Hf-177/Hf-176 (1)
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Nd-144/Nd-143 (1)
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Sm-147/Nd-144 (1)
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lineation (1)
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magmas (1)
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metal ores
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copper ores (3)
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gold ores (1)
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iron ores (1)
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manganese ores (1)
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molybdenum ores (1)
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polymetallic ores (1)
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pyrite ores (1)
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tungsten ores (1)
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zinc ores (2)
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metals
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hafnium
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Hf-177/Hf-176 (1)
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rare earths
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neodymium
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Nd-144/Nd-143 (1)
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Sm-147/Nd-144 (1)
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samarium
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Sm-147/Nd-144 (1)
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metamorphic rocks
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metaigneous rocks
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metadacite (1)
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metasedimentary rocks
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metachert (1)
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metavolcanic rocks (8)
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phyllites (3)
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quartzites (1)
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schists
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greenstone (4)
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slates (1)
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metamorphism (4)
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mineral deposits, genesis (2)
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mineral resources (1)
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North America
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Appalachians
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Blue Ridge Mountains (5)
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Blue Ridge Province (2)
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Carolina slate belt (8)
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Piedmont (14)
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Southern Appalachians (13)
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Valley and Ridge Province (1)
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-
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orogeny (8)
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Paleozoic
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Cambrian
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Lower Cambrian
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Chilhowee Group (2)
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Murphy Marble (2)
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Shady Dolomite (3)
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Carboniferous
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Mississippian (3)
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Pennsylvanian (1)
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Devonian
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Lower Devonian (1)
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lower Paleozoic (3)
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middle Paleozoic
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Hillabee Chlorite Schist (2)
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Ordovician (5)
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Permian (1)
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Silurian (3)
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Talladega Group (10)
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petrology (7)
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Plantae
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Pteridophyta
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Lycopsida (1)
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plate tectonics (8)
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Precambrian
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Eocambrian (1)
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Great Smoky Group (1)
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upper Precambrian
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Proterozoic
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Neoproterozoic
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Walden Creek Group (1)
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sea-level changes (1)
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sedimentary petrology (1)
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sedimentary rocks
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carbonate rocks
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clastic rocks
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argillite (1)
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graywacke (1)
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mudstone (1)
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sedimentary structures
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biogenic structures
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carbonate banks (1)
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soft sediment deformation
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olistostromes (1)
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sedimentation (1)
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stratigraphy (9)
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structural analysis (2)
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structural geology (9)
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symposia (1)
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tectonics (16)
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tectonophysics (2)
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United States
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Alabama
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Cherokee County Alabama (1)
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Chilton County Alabama (6)
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Clay County Alabama (6)
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Cleburne County Alabama (3)
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Coosa County Alabama (6)
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Shelby County Alabama (2)
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Talladega County Alabama (5)
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Blue Ridge Mountains (5)
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Eastern U.S.
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Southeastern U.S. (1)
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Georgia
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Bartow County Georgia
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Cartersville Georgia (1)
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Cherokee County Georgia (2)
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Paulding County Georgia (1)
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Polk County Georgia (1)
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Great Smoky Fault (1)
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North Carolina
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Chatham County North Carolina (1)
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Cherokee County North Carolina (1)
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Moore County North Carolina (1)
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Pine Mountain Window (1)
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South Carolina (4)
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Talladega Front (18)
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Tennessee (3)
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volcanology (1)
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rock formations
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Ocoee Supergroup (3)
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sedimentary rocks
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sedimentary rocks
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carbonate rocks
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dolostone (1)
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clastic rocks
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argillite (1)
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graywacke (1)
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mudstone (1)
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turbidite (1)
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sedimentary structures
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sedimentary structures
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biogenic structures
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carbonate banks (1)
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soft sediment deformation
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olistostromes (1)
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-
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sediments
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turbidite (1)
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New paleontological evidence for complex middle Paleozoic tectonic evolution in the Appalachian western Blue Ridge
Taconic suprasubduction zone magmatism in southern Laurentia: Evidence from the Dadeville Complex
Abstract Independent researchers working in the Talladega belt, Ashland-Wedowee-Emuckfaw belt, and Opelika Complex of Alabama, as well as the Dahlonega gold belt and western Inner Piedmont of Alabama, Georgia, and the Carolinas, have mapped stratigraphic sequences unique to each region. Although historically considered distinct terranes of disparate origin, a synthesis of data suggests that each includes lithologic units that formed in an Ordovician back-arc basin (Wedowee-Emuckfaw-Dahlonega basin—WEDB). Rocks in these terranes include varying proportions of metamorphosed mafic and bimodal volcanic rock suites interlayered with deep-water metasedimentary rock sequences. Metavolcanic rocks yield ages that are Early–Middle Ordovician (480–460 Ma) and interlayered metasedimentary units are populated with both Grenville and Early–Middle Ordovician detrital zircons. Metamafic rocks display geochemical trends ranging from mid-oceanic-ridge basalt to arc affinity, similar to modern back-arc basalts. The collective data set limits formation of the WEDB to a suprasubduction system built on and adjacent to upper Neoproterozoic–lower Paleozoic rocks of the passive Laurentian margin at the trailing edge of Iapetus, specifically in a continental margin back-arc setting. Overwhelmingly, the geologic history of the southern Appalachians, including rocks of the WEDB described here, indicates that the Ordovician Taconic orogeny in the southern Appalachians developed in an accretionary orogenic setting instead of the traditional collisional orogenic setting attributed to subduction of the Laurentian margin beneath an exotic or peri-Laurentian arc. Well-studied Cenozoic accretionary orogens provide excellent analogs for Taconic orogenesis, and an accretionary orogenic model for the southern Appalachian Taconic orogeny can account for aspects of Ordovician tectonics not easily explained through collisional orogenesis.
Overview of the stratigraphic and structural evolution of the Talladega slate belt, Alabama Appalachians
Abstract The allochthonous Talladega belt of eastern-northeastern Alabama and northwestern Georgia is a northeast striking, fault bounded block of lower greenschist facies metasedimentary and metaigneous rocks that formed along the margin of Laurentia at or outboard of the seaward edge of the Alabama promontory. Bounded by metamorphic rocks of the higher grade Neoproterozoic(?) to Carboniferous eastern Blue Ridge on the southeast and unmetamorphosed to anchimetamorphic Paleozoic rocks of the Appalachian foreland on the northwest, the Talladega belt includes shelf facies rocks of the latest Neoproterozoic/earliest Cambrian Kahatchee Mountain Group, Cambrian-Ordovician Sylacauga Marble Group, and the latest Silurian(?) to uppermost Devonian/earliest Mississippian Talladega Group. Along the southeastern flank of these metasedimentary sequences, a Middle Ordovician back-arc terrane (Hillabee Greenstone) was tectonically emplaced along a cryptic pre-metamorphic thrust fault (Hillabee thrust) and subsequently dismembered with units of the upper Talladega Group along the post-metamorphic Hollins Line fault system. Importantly, strata within the Talladega belt are critical for understanding the tectonic evolution of the southern Appalachian orogen when coupled with the geologic history of adjacent terranes. Rocks of the lower Talladega Group, the Lay Dam Formation, suggest latest Silurian–earliest Devonian tectonism that is only now being recognized in other areas of the southern Appalachians. Additionally, correlation between the Middle Ordovician Hillabee Greenstone and similar bimodal metavolcanic suites in the Alabama eastern Blue Ridge and equivalent Dahlonega Gold belt of Georgia and North Carolina suggests the presence of an extensive back-arc volcanic system on the Laurentian plate just outboard of the continental margin during the Ordovician and has significant implications for models of southern Appalachian Taconic orogenesis.
Southern Appalachian Laurentian margin initial drift-facies sequences: Implications for margin evolution
In the Appalachian orogen, the Neoproterozoic(?)–Lower Cambrian Chilhowee Group represents the initial drift-facies deposits along and across the eastern Laurentian continental margin following rifting. In the Southern Appalachians, this group forms thrust sheets along the west flank of the Talladega–Blue Ridge belt. Where the base is unfaulted, it lies depositionally above Ocoee Supergroup rift-facies rocks or Grenville basement. Regionally, the Chilhowee grades up into the Lower Cambrian Shady Dolomite, the initial deposits of the marginwide Cambrian–Ordovician carbonate bank. Sequences more interior to the orogen, including the Kahatchee Mountain Group (Talladega belt), the Nantahala and Brasstown Formations (western Blue Ridge), and the Hollis Quartzite (Pine Mountain belt), are considered to be correlative with the Chilhowee based upon similarities in lithostratigraphic sequence, sequence stratigraphy, sandstone provenance, and paleocurrent studies. Assuming an autochthonous Pine Mountain window, palinspastic restorations of foreland thrusts suggest that the Chilhowee Group restores essentially astride that window, and Chilhowee-equivalent units in the Talladega–Blue Ridge belts, in turn, restore farther southeast. This places the respective sequences southeastward in the order of increasing thickness and depth to basement from the base of the carbonate bank facies, with units restored farthest southeast having the most distal marine characteristics. Retro-deformation of thrust belt structures and the Pine Mountain cover sequence restores the Kahatchee Mountain Group at least to the subsurface position of the Wiggins-Suwannee suture, the southeastern limit of Laurentian continental crust, indicating that this group's basement was subducted beneath Gondwanan or peri-Gondwanan crust, and that the basement of even more outboard Laurentian sequences (e.g., eastern Blue Ridge) was overridden even farther.
Volcanic arc emplacement onto the southernmost Appalachian Laurentian shelf: Characteristics and constraints
Rifted-margin architecture, cover stratigraphy, and structure of basement culminations, frontal Appalachian Blue Ridge, Georgia, USA
The three southernmost external Appalachian Grenville basement massifs occur in the Georgia western Blue Ridge, where they core map-scale, inclined-to-recumbent, west-vergent isoclinal anticlinoria formed during peak greenschist-facies Paleozoic metamorphism. The massifs are in thrust contact with Cambrian rocks of the adjacent foreland thrust belt. The basal cover unit of each massif, the Pinelog Formation, is likely correlative with the Late Proterozoic Snowbird Group of the Ocoee Supergroup. This sequence was deposited in fluvial-alluvial to shallow-water deltaic to intertidal environments adjacent to sharp basement uplifts, most probably along extensional fault scarps during initial Late Proterozoic rifting of Laurentia. A second phase of more extensive continental rifting and subsidence followed with deposition of the Great Smoky Group, a mostly deep-water turbiditic sequence. During the second rift cycle, a large (>2000 km 2 ) block, which included much of the Georgia western Blue Ridge and contained the deposits of the earlier rift basin, was tilted westward with the underlying basement along a southeast-dipping extensional fault system (stratigraphic offset >1 km) flanking the western margin of the Blue Ridge. Great Smoky units lie unconformably above this block and progressively cut deeper into the underlying cover sequence and then into the basement toward the east. This northwest-border fault system was bounded to the southwest by a large continental transfer (transform) fault, which marked the southern limit of the Ocoee basin, and across which the polarity of faulting along the rifted margin was reversed. Internal thrusts associated with Alleghanian continental collision, e.g., the frontal Blue Ridge thrust, were likely rooted below the basement massifs because the massifs had been previously detached from autochthonous basement by the two earlier cycles of rift-related faulting.
Structural evolution of a major Appalachian salient-recess junction: Consequences of oblique collisional convergence across a continental margin transform fault
Southeastern margin of the middle Paleozoic shelf, southwesternmost Appalachians: Regional stability bracketed by Acadian and Alleghanian tectonism
Laurentian magmatism of the southern Appalachian Blue Ridge: Post-Iapetan rifting
Analysis of a regional middle Paleozoic unconformity along the distal southeastern Laurentian margin, southernmost Appalachians: Implications for tectonic evolution
Appalachian Blue Ridge cover sequence ranges at least into the Ordovician
Nested Paleozoic "successor" basins in the southern Appalachian Blue Ridge
The Acadian orogen
Abstract An orogenic cycle (Wilson, 1963) in simplest form may be of long duration, and it includes rifting, subduction, and final closure by which an ocean basin is initiated and ultimately destroyed. In real orogens the cycle must be more complicated, being punctuated, possibly at several intervals, by such things as cessation of subduction, collision of microplates, or by obduction. The Acadian orogeny probably represents such a punctuation in an orogenic cycle that lasted through Paleozoic time. Where the Acadian orogeny is recognized in the Appalachians, it was in some places preceded by earlier punctuations (Penobscottian, Taconian), and was followed by a final collisional event (Alleghanian). In the context of the Acadian orogeny, only those geologic features that have a causal relationship to the Acadian will be considered in this chapter.
Tectonic setting of olistostromal units and associated rocks in the Talladega slate belt, Alabama Appalachians
Olistostromal deposits are extensive in the Silurian(?) to Lower Devonian Lay Dam Formation in the Talladega slate belt of central Alabama. These rocks form part of a thick (2 to 3 km) clastic sequence deposited unconformably above the upper Precambrian(?) to Lower Ordovician Appalachian miogeocline displaying a rifted to passive margin, clastic and carbonate bank facies. The Talladega belt is a far-traveled Alleghanian thrust sheet metamorphosed to lower greenschist facies during the Acadian orogeny and thrust above the foreland fold-and-thrust belt. The olistostromes are commonly several hundred meters thick and extend laterally for tens of kilometers. They are unsorted, unbedded, polymictic, matrix-supported and matrix-dominated units containing clasts of diverse provenance, including sedimentary clasts (carbonate rocks, sandstone, chert, and shale) and igneous and high-grade metamorphic clasts (granite, granitic gneiss, anorthosite, gabbroic gneiss, and garnet mica schist). The source of the clastic sequence was uplifted along fault scarps to the south, and included a Grenville basement terrane and its cover of clastic and carbonate sedimentary rocks, probably equivalent to that found unconformably below the Lay Dam Formation. Rapid erosion (caused by differential uplift and extreme relief of the source area), and relatively short transport distances to the Lay Dam basin resulted in little modification of the Lay Dam’s chemically and mechanically unstable mineral and rock fragment suite. The basin thus became characterized by heterogeneous, mineralogically unstable rock fragment compositions. The olistostromes and associated rocks are interpreted as resedimented deposits formed in relatively deep water by gravity-flow mechanisms, such as debris flow and turbidity currents, in a submarine fan–like environment. These rocks are overlain by shallow-water sequences, including the Butting Ram and Cheaha sandstones and the Jemison Chert. The Lay Dam basin is interpreted as an ensialic foreland successor basin formed in response to back-arc extension during initial stages of the Acadian orogeny.
New paleontologic evidence constraining the age and paleotectonic setting of the Talladega slate belt, southern Appalachians
Mitchell Dam amphibolite along Alabama Highway 22, east-central Chilton and west-central Coosa Counties, Alabama
Abstract The Mitchell Dam Amphibolite is located along the Coosa River 9 miles (14.5 km) east of Clanton near the center of the Mitchell Dam 7½-minute quadrangle, Chilton and Coosa Counties, Alabama (Fig. 1). Two excellent outcrops illustrate the mineralogical, textural, and structural complexity of the amphibolite. Both exposures are easily accessible, located near the shoulder of Alabama 22.
Olistostromal unit of the Silurian-Lower Devonian Lay Dam Formation, Talladega Slate Belt, Chilton County, Alabama
Abstract One of the better exposures of an olistostromal sequence (metadiamictite facies) in the Lay Dam Formation lies immediately west of the Coosa River Bridge on Chilton County Road 55, approximately 12 mi ( 19 km) east of Jemison, Alabama (Fig. 1). To reach the site from the Lay Dam Exit on I-65, proceed north on Alabama 145 approximately 2 mi (3.2 km) to Chilton County Road 55. Turn right (east) and proceed approximately 6 mi ( 10 km) to the new Coosa River Bridge at Mire's Ferry. All access roads are improved and readily accessible. The stop is located in the SE¼ of Section 24, T 23 N, R 15 E, Chilton County, Alabama, and may be found on the Lay Dam, Alabama 7½-minute quadrangle. The metadiamictite is exposed on both sides of the highway. Good exposures of the metadamictite also may be found on the east side of the bridge and at the old Mire's Ferry Landing south of the bridge.