Lithotectonic map of the Appalachian Orogen, Canada - United States of America

Hibbard, James P.; Staal, Cees R. van; Rankin, D W; Williams, Holly

doi:10.4095/221932

Cited by 97 publications

(111 citation statements)

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“…This suture was first located by the magnetic anomaly and seismic profiling that indicated a south-dipping contact (Daniels et al, 1983;McBride and Nelson, 1988;Chowns and Williams, 1983;Nelson et al, 1985a,b). Through a series of lithotectonic maps (e.g., Williams, 1978;Williams and Hatcher, 1983;Hatcher et al, 1990Hatcher et al, , 2007Thomas et al, 1990aThomas et al, , 1990bHibbard et al, 2006), numerous accreted terranes of various ages have been identified and their boundaries defined using geochronologic, thermal, and lithotectonic characteristics combined with potential field (e.g., gravity and magnetic) signatures.…”

Section: Introductionmentioning

confidence: 99%

The Grenville orogenic cycle of southern Laurentia: Unraveling sutures, rifts, and shear zones as potential piercing points for Amazonia

Bartholomew¹,

Hatcher²

2010

Journal of South American Earth Sciences

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Section: Introductionmentioning

confidence: 99%

The Grenville orogenic cycle of southern Laurentia: Unraveling sutures, rifts, and shear zones as potential piercing points for Amazonia

Bartholomew¹,

Hatcher²

2010

Journal of South American Earth Sciences

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“…The aeromagnetic signature of domain 23B thus is compatible with these surface relations, supporting the suggestion of Steltenpohl et al (2005a) that the Opelika Complex should be reassigned to the eastern Blue Ridge, and that the Dadeville Complex is a very thin allochthonous "scoop-shaped" klippe emplaced during an early stage of development of the Brevard fault zone. Future fi eld studies in this area will help to further constrain the tectonostratigraphy and structural confi guration of the southernmost Brevard fault zone, and mapping in Georgia is needed to delimit the extent and signifi cance of this Blue Ridge window beneath the Dadeville Complex that has been referred to as the Opelika belt (Hibbard et al, 2006) and the Dog River window ( Fig. 1; Higgins and Crawford, 2007;Hatcher, 2010;Steltenpohl et al, 2010aSteltenpohl et al, , 2011Higgins et al, 2011).…”

Section: Discussion and Directions For Future Studiesmentioning

confidence: 96%

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et al. 2013

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We dedicate this paper to the memory of coauthor Isidore (Izzy) Zietz, who died at age 93 while this paper was in review. After contributing to the early theoretical foundation for analysis of airborne magnetic surveys, Izzy became a leading advocate for aeromagnetic survey acquisition and interpretation throughout the U.S., combining surveys into regional, state, and national maps, and working with regional geologists in interpreting geophysical anomalies. Like many geologists, we have been energized by Izzy's contagious enthusiasm for using magnetic and gravity anomalies to delineate and characterize major tectonic features. Lessons from working with him on data from Alabama and elsewhere over the years will continue to infl uence our appreciation and understanding of aeromagnetic and gravity anomalies for interpreting the Earth's upper crust."Magnetics is never good, and gravity is even worse!" "…all of it can just be dashed." -Isidore Zietz ABSTRACT Aeromagnetic and gravity data sets obtained for Alabama (United States) have been digitally merged and fi ltered to enhance upper-crustal anomalies. Beneath the Appalachian Basin in northwestern Alabama, broad deep-crustal anomalies of the continental interior include the Grenville front and New York-Alabama lineament (dextral fault). Toward the east and south, high-angle discordance between the northeast-trending Appalachians and the east-west-trending wedge of overlapping Mesozoic and Cenozoic Gulf Coastal Plain sediments reveals how bedrock geophysical signatures progressively change with deeper burial. Highfrequency magnetic anomalies in the Appalachian deformed domain (ADD) correspond to amphibolites and mylonites outlining terranes, while broader, lower-amplitude domains include Paleozoic intrusive bodies and Grenville basement gneiss. Fundamental ADD structures (e.g., the Alexander City, Towaliga, and Goat Rock-Bartletts Ferry faults) can be traced southward beneath the Gulf Coastal Plain to the suture with Gondwanan crust of the Suwannee terrane. Within the ADD, there is clear magnetic distinction between Laurentian crust and the strongly linear, high-frequency magnetic highs of peri-Gondwanan (Carolina-Uchee) arc terranes. The contact (Central Piedmont suture) corresponds to surface exposures of the Bartletts Ferry fault. ADD magnetic and gravity signatures are truncated by the eastwest-trending Altamaha magnetic low associated with the Suwannee suture. Arcuate northeast-trending magnetic linears of the Suwannee terrane refl ect internal structure and Mesozoic failed-rift trends. Geophysical data can be used to make inferences on surface and subsurface geology and vice versa, which has applicability anywhere that bedrock is exposed or concealed beneath essentially non-magnetic sedimentary cover.

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“…1; Gerbi and West, 2007;Hibbard et al, 2006;Hussey et al, 2010;Tucker et al, 2001;van Staal et al, 2009). Siluro-Devonian subduction-related shortening led to early thrusts and recumbent folds followed by later upright, isoclinal folds (Tucker et al, 2001).…”

Section: Regional Geologymentioning

confidence: 97%

Recrystallization fabrics of sheared quartz veins with a strong pre-existing crystallographic preferred orientation from a seismogenic shear zone

et al. 2016

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Microstructural investigations were carried out on quartz veins in schist, protomylonite, and mylonite samples from an ancient seismogenic strike-slip shear zone (Sandhill Corner shear zone, Norumbega fault system, Maine, USA). We interpret complexities in the microstructural record to show that: (1) pre-existing crystallographic preferred orientations (CPO) in the host rock may persist in the new CPO patterns of the shear zone and (2) the inner and outer parts of the shear zone followed diverging paths of fabric development. The host rocks bounding the shear zone contain asymmetrically-folded quartz veins with a strong CPO. These veins are increasingly deformed and recrystallized with proximity to the shear zone core. Matrixaccommodated rotation and recrystallization may position an inherited c-axis maximum in an orientation coincident with rhomb baN or basal baN slip. This inherited CPO likely persists in the shear zone fabric as a higher concentration of poles in one hemisphere of the c-axis pole figure, leading to asymmetric crossed girdle or paired maxima c-axis patterns about the foliation plane. Three observed quartz grain types indicate a general trend of localization with decreasing temperature: (1) large (N 100 μm), low aspect ratio (b~5) and (2) high aspect ratio (~5-20) grains overprinted by (3) smaller (b~80 μm), low aspect ratio (b~4) grains through subgrain rotation-dominated recrystallization. In the outer shear zone, subgrain rotation recrystallization led to a well-developed c-axis crossed girdle pattern. In the inner shear zone, the larger grains are completely overprinted by smaller grains, but the CPO patterns are relatively poorly developed and are associated with distinctively different misorientation angle histogram profiles ("flat" neighbor-pair profile with similar number fraction for angles from 10 to 90°). This may reflect the preferential activation of grain size sensitive deformation processes in the inner-most part of the shear zone where transient deformation associated with the seismic cycle may have localized.

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Lithotectonic map of the Appalachian Orogen, Canada - United States of America

Cited by 97 publications

References 0 publications

The Grenville orogenic cycle of southern Laurentia: Unraveling sutures, rifts, and shear zones as potential piercing points for Amazonia

The Grenville orogenic cycle of southern Laurentia: Unraveling sutures, rifts, and shear zones as potential piercing points for Amazonia

Untitled

Recrystallization fabrics of sheared quartz veins with a strong pre-existing crystallographic preferred orientation from a seismogenic shear zone

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