Eastern Piedmont fault system: Speculations on its extent

Research Article| February 01, 2000 Evidence for a buried fault system in the Coastal Plain of the Carolinas and Virginia—Implications for neotectonics in the southeastern United States Ronald T. Marple; Ronald T. Marple 1Geosignal, 11111 Katy Freeway, Houston, Texas 77082 Search for other works by this author on: GSW Google Scholar Pradeep Talwani Pradeep Talwani 2Department of Geological Sciences, University of South Carolina, Columbia, South Carolina 29208 Search for other works by this author on: GSW Google Scholar Author and Article Information Ronald T. Marple 1Geosignal, 11111 Katy Freeway, Houston, Texas 77082 Pradeep Talwani 2Department of Geological Sciences, University of South Carolina, Columbia, South Carolina 29208 Publisher: Geological Society of America Received: 08 Aug 1998 Revision Received: 01 Jun 1999 Accepted: 15 Jun 1999 First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2000) 112 (2): 200–220. https://doi.org/10.1130/0016-7606(2000)112<200:EFABFS>2.0.CO;2 Article history Received: 08 Aug 1998 Revision Received: 01 Jun 1999 Accepted: 15 Jun 1999 First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Ronald T. Marple, Pradeep Talwani; Evidence for a buried fault system in the Coastal Plain of the Carolinas and Virginia—Implications for neotectonics in the southeastern United States. GSA Bulletin 2000;; 112 (2): 200–220. doi: https://doi.org/10.1130/0016-7606(2000)112<200:EFABFS>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Geomorphic, geologic, and geophysical data suggest the presence of an ∼600-km-long, north-northeast–trending buried fault system in the Coastal Plain of the Carolinas and Virginia, herein named the East Coast fault system. The East Coast fault system is expressed by anomalous changes in fluvial geomorphology that locally coincide with one or more of the following features: linear aeromagnetic anomalies, buried faults interpreted from seismic reflection data, surface faults offsetting Pliocene–Pleistocene surficial units, locally brecciated phyllites and argillites, gently upwarped sediments, topographic highs, and seismicity near Summerville, South Carolina.River anomalies where the rivers traverse unconsolidated upper Pleistocene–Holocene flood-plain sediments are evidence of deformation along the East Coast fault system during the past 130 to 10 k.y. which may be ongoing. The fault system traverses the epicentral area of the 1886 Charleston, South Carolina, earthquake and lies west of paleoliquefaction sites along the outer South Carolina Coastal Plain; thus, the fault system could be the source of the Charleston earthquake and other large prehistoric earthquakes. Therefore, confirmation and demarcation of the East Coast fault system and elucidation of its history will help better assess seismic hazards in the southeastern United States. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Understanding the evolution and destruction of past oceans not only leads to a better understanding of earth history, but permits comparison with extant ocean basins and tectonic processes. This paper reviews the history of the Early Paleozoic circum‐Atlantic oceans by analogy with the Pacific Ocean and Mesozoic Tethys. Rifting and continental separation from 620 to 570 Ma led to the development of passive margins along parts of the northern margin of Gondwana (the western coast of South America); eastern Laurentia (eastern North America, NW Scotland and East Greenland), and western Baltica (western Scandinavia). Meagre paleomagnetic data suggest that western South America and eastern North America could have been joined together to form facing margins after breakup. Although western Baltica is an apparently obvious candidate for the margin facing NW Scotland and East Greenland, the paleomagnetic uncertainties are so large that other fragments could have been positioned there instead. The Iapetus Ocean off northeastern Gondwana was probably a relatively wide Pacific‐type ocean with, during the late Precambrian to early Ordovician, the northern margin of Gondwana as a site of continentward‐dipping subduction zone(s). The 650‐500 Ma arc‐related igneous activity here and the associated deformation gave rise to the Cadomian, ‘Grampian’, Penobscotian, and Famantinian igneous and orogenic events. By 490‐470 Ma, marginal basins had formed along the eastern Laurentian margin as far as NE Scotland, along parts of the northern margin of Gondwana, and off western Baltica, but none are known from the East Greenland margin. These basins closed and parts were emplaced as ophiolites shortly after their formation by processes that, at least in some cases, closely resemble the emplacement of the late Cretaceous Semail ophiolite of Oman. This orogenic phase seems to have involved collision and attempted subduction of the continental margin of Laurentia, Gondwana and Baltica. In Baltica it gave rise to some eclogite facies metamorphism. Marginal basin development may have been preceded by arc formation as early as ca 510 Ma. A double arc system evolved outboard from the eastern Laurentian and western Baltica margins, analogous to some of the arc systems in the present‐day western Pacific. At 480‐470 Ma, there was a second phase of breakup of Gondwana, affecting the active Gondwanan margin. Eastern and Western Avalonia, the Carolina Slate Belt, Piedmont, and other North American exotic continental blocks rifted away from Gondwana. Farther east, Armorica, Aquitainia, Iberia and several European exotic continental blocks also rifted away, though it is unlikely that they all rifted at the same time. Between 460‐430 Ma, peaking at ca 450 Ma, orogenic events involved continuing arc‐continent collision(s). From 435‐400 Ma the remaining parts of the Eastern Iapetus Ocean were destroyed and the collision of Baltica with Laurentia caused the 430‐400 Ma Scandian orogeny, followed by suturing of these continents during the Siluro‐Devonian Acadian orogeny or Late Caledonian orogeny to 380 Ma, leaving a smaller but new ocean south of the fragments that had collided with the Laurentian margin farther south. The Ligerian orogeny 390‐370 Ma collision of Gondwana‐derived Aquitaine‐Cantabrian blocks with Eastern Avalonia‐Baltica and removed the part of the Iapetus south of Baltica.Prior to any orogenic events, the Eastern Iapetus Ocean between Baltica and Laurentia may have resembled the present‐day central Atlantic Ocean between Africa and North America. The ocean appears to have closed asymmetrically, with arcs forming first outboard of the western margin of Baltica while the East Greenland margin was unaffected. The Western Iapetus Ocean between Laurentia and Gondwana also closed asymmetrically with a dual arc system developing off Laurentia and an arc system forming off the northern margin of Gondwana. Like the Pacific Ocean today, the Eastern Iapetus Ocean had a longer and more complex history than the Western Iapetus Ocean: it was already in existence at 560 Ma, probably developed over at least 400 million years, by mid‐Cambrian time was many thousands of kilometres wide at maximum extent, and was associated with a &lt; 30 million year phase of marginal basin formation. In contrast, the Western Iapetus Ocean appears to have been much narrower, shorter lived (probably &lt; 100 million years), and associated with the rifting to form two opposing passive carbonate margins, analogous to the Mesozoic Tethys or the present‐day Mediterranean.

Interblock zones in the crust of the southern regions of East Siberia: tectonophysical interpretation of geological and geophysical data

Research Article| May 01, 2001 Neotectonics of the southeastern Reelfoot rift zone margin, central United States, and implications for regional strain accommodation Randel Tom Cox; Randel Tom Cox 1Department of Geological Sciences, University of Memphis, Memphis, Tennessee 38152, USA Search for other works by this author on: GSW Google Scholar Roy B. Van Arsdale; Roy B. Van Arsdale 1Department of Geological Sciences, University of Memphis, Memphis, Tennessee 38152, USA Search for other works by this author on: GSW Google Scholar James B. Harris; James B. Harris 2Department of Geology, Millsaps College, Jackson, Mississippi 39210, USA Search for other works by this author on: GSW Google Scholar Daniel Larsen Daniel Larsen 3Department of Geological Sciences, University of Memphis, Memphis, Tennessee 38152, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Randel Tom Cox 1Department of Geological Sciences, University of Memphis, Memphis, Tennessee 38152, USA Roy B. Van Arsdale 1Department of Geological Sciences, University of Memphis, Memphis, Tennessee 38152, USA James B. Harris 2Department of Geology, Millsaps College, Jackson, Mississippi 39210, USA Daniel Larsen 3Department of Geological Sciences, University of Memphis, Memphis, Tennessee 38152, USA Publisher: Geological Society of America Received: 26 Sep 2000 Revision Received: 23 Jan 2001 Accepted: 29 Jan 2001 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2001) 29 (5): 419–422. https://doi.org/10.1130/0091-7613(2001)029<0419:NOTSRR>2.0.CO;2 Article history Received: 26 Sep 2000 Revision Received: 23 Jan 2001 Accepted: 29 Jan 2001 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Randel Tom Cox, Roy B. Van Arsdale, James B. Harris, Daniel Larsen; Neotectonics of the southeastern Reelfoot rift zone margin, central United States, and implications for regional strain accommodation. Geology 2001;; 29 (5): 419–422. doi: https://doi.org/10.1130/0091-7613(2001)029<0419:NOTSRR>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The northeast-striking New Madrid fault system of central North America has been described as a right-lateral strike-slip system with a left-stepping restraining-bend thrust. The fault system has one of the highest rates of seismic energy release in an intraplate setting, and it has been regarded as a zone of significant earthquake hazard. The New Madrid fault system is the central part of the wider Reelfoot rift fault system, a northeast- striking basement fault zone. Although component faults of the New Madrid system are well defined by microseismicity, recent geodetic surveys suggest that little if any strain is accumulating on the principal (southern) strike-slip arm of the fault system. Seismicity and geologic data show that the "restraining-bend" thrust continues past the southern strike-slip arm to the southeastern Reelfoot rift margin. Thus, we suggest that earthquakes defining the southern arm of the New Madrid fault system are primarily aftershocks of an earthquake on that arm during the last sequence of great earthquakes (A.D. 1811– 1812), and it is the southeastern rift-margin fault system that is currently accommodating right-lateral strain along the boundary of the thrust block. This interpretation is consistent with recent geodetic results. The southeastern rift margin coincides with a 150-km-long linear topographic scarp from near Memphis to the Tennessee-Kentucky line, and S-wave reflection profiles, auger data, and a trench excavation reveal late Wisconsin–early Holocene surface faulting and late Holocene liquefaction associated with this fault-line scarp. Variation in sense of throw along strike and flower-structure geometry suggest that this is a strike-slip fault. Recognition of this rift margin as an important element of active tectonism in the Mississippi embayment has broad implications for assessment of the seismic hazard of this and similar intraplate settings. Temporal shifts in strain accommodation may give rise to short-term seismicity patterns and/or geodetic velocities that do not reveal long-term tectonic patterns. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Research Article| December 01, 1980 Pre-Cenozoic normal faulting in the Osgood Mountains, Humboldt County, Nevada Byron R. Berger; Byron R. Berger 1U.S. Geological Survey, Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Bruce E. Taylor Bruce E. Taylor 2Department of Geology, University of California, Davis, Davis, California 95616 Search for other works by this author on: GSW Google Scholar Author and Article Information Byron R. Berger 1U.S. Geological Survey, Federal Center, Denver, Colorado 80225 Bruce E. Taylor 2Department of Geology, University of California, Davis, Davis, California 95616 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1980) 8 (12): 594–598. https://doi.org/10.1130/0091-7613(1980)8<594:PNFITO>2.0.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Byron R. Berger, Bruce E. Taylor; Pre-Cenozoic normal faulting in the Osgood Mountains, Humboldt County, Nevada. Geology 1980;; 8 (12): 594–598. doi: https://doi.org/10.1130/0091-7613(1980)8<594:PNFITO>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The Getchell fault system consists of several major faults extending for more than 25 km along the eastern side of the Osgood Mountains. Movement on the fault system has been complex and largely dip slip in character. The emplacement of igneous rocks and subsequent gold deposits was controlled by the fault system; dating of the igneous rocks indicates that the fault system existed in Late Cretaceous time. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Reply| December 01, 1988 Reply to Kenneth W. Campbell's “comment on ‘an investigation into earthquake ground motion characteristics in Eastern North America’” G. R. Toro; G. R. Toro Risk Engineering, Inc.5255 Pine Ridge Road Golden, Colorado 80403 Search for other works by this author on: GSW Google Scholar R. K. McGuire R. K. McGuire Risk Engineering, Inc.5255 Pine Ridge Road Golden, Colorado 80403 Search for other works by this author on: GSW Google Scholar Author and Article Information G. R. Toro Risk Engineering, Inc.5255 Pine Ridge Road Golden, Colorado 80403 R. K. McGuire Risk Engineering, Inc.5255 Pine Ridge Road Golden, Colorado 80403 Publisher: Seismological Society of America Received: 11 Jul 1988 First Online: 03 Mar 2017 Online Issn: 1943-3573 Print Issn: 0037-1106 Copyright © 1988, by the Seismological Society of America Bulletin of the Seismological Society of America (1988) 78 (6): 2102–2104. https://doi.org/10.1785/BSSA0780062102 Article history Received: 11 Jul 1988 First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation G. R. Toro, R. K. McGuire; Reply to Kenneth W. Campbell's “comment on ‘an investigation into earthquake ground motion characteristics in Eastern North America’”. Bulletin of the Seismological Society of America 1988;; 78 (6): 2102–2104. doi: https://doi.org/10.1785/BSSA0780062102 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of the Seismological Society of America Search Advanced Search This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Research Article| June 01, 1999 Implications of Jurassic, Cretaceous, and Proterozoic piercing lines for Laramide oblique-slip faulting in New Mexico and rotation of the Colorado Plateau Steven M. Cather Steven M. Cather 1New Mexico Bureau of Mines and Mineral Resources, Socorro, New Mexico 87801 Search for other works by this author on: GSW Google Scholar Author and Article Information Steven M. Cather 1New Mexico Bureau of Mines and Mineral Resources, Socorro, New Mexico 87801 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1999) 111 (6): 849–868. https://doi.org/10.1130/0016-7606(1999)111<0849:IOJCAP>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Steven M. Cather; Implications of Jurassic, Cretaceous, and Proterozoic piercing lines for Laramide oblique-slip faulting in New Mexico and rotation of the Colorado Plateau. GSA Bulletin 1999;; 111 (6): 849–868. doi: https://doi.org/10.1130/0016-7606(1999)111<0849:IOJCAP>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Regional isopach patterns and pinch-out data for nine stratigraphic units of Jurassic and Cretaceous age are either permissive or supportive of significant dextral slip of Laramide age along the eastern Colorado Plateau boundary in New Mexico. The best-constrained dextral offset estimates are for the Sand Hill–Nacimiento fault system (20–33 km) and the previously published 13 km estimate for the Defiance monocline, which together yield a cumulative offset of 33–46 km. Mesozoic stratigraphic constraints for other Laramide fault systems are less precise, and typically provide only maximum limits for possible dextral offsets because of widely spaced control points and broad areas of Tertiary erosion. These less precise constraints allow as much as 40–60 km of Laramide dextral slip along what is now the Rio Grande rift and as much as 110 km across the entire breadth of the Laramide deformed zone in central and northern New Mexico.Well-documented dextral offsets of Proterozoic lithologies and structures across the Tusas-Picuris fault system (15 km) and Picuris-Pecos fault (37 km) probably represent minimum Laramide displacements because of the need to account for sinistral components related to other deformations. These displacements, when combined with dextral offsets along Sand Hill–Nacimiento and Defiance structures, yield a minimum dextral offset of ∼85 km for Laramide structures in northern New Mexico. This minimum dextral offset is approximately equivalent to the amount of Laramide crustal shortening on and northward of the Colorado Plateau, a result that argues against nearby Euler pole locations for Laramide rotation of the Colorado Plateau relative to cratonic North America. Geological constraints allow ∼0° to 3° of Laramide clockwise rotation of the Colorado Plateau. Additional clockwise plateau rotation during late Cenozoic development of the Rio Grande rift was 1° to 1.5°. Geological constraints thus indicate that clockwise rotation of the Colorado Plateau from combined Laramide and Rio Grande rift deformations was between about 1° and 4.5°. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The area of study is located to the south east of Aswan occupying part of Nasser Lake in its western section. Nasser Lake is contemplated as a source of tectonic instability and earthquake activities in Aswan region. Most of this activity was recorded in the western side of the lake, coincides with the intersections of the two major fault systems, trending in the NS and EW directions. Therefore, mapping the subsurface structures in the study area can shed more light on the structural setting of this zone of the lake and its relation to tectonic instability. This study presents the analysis and interpretation of aeromagnetic data to map the subsurface structural framework of the area around the Lake. Structural interpretation of the magnetic data was achieved through applying advanced interpretation techniques that provide automatic delineation and depth estimation of the magnetic structures. These techniques include Horizontal Gradient, Euler deconvolution and Local wave number. The structure locations and depths obtained from these methods were integrated to delineate the tectonic framework of the area. The mapped structures reveal that the area is affected by a set of faults trending mainly in the NW-SE, EW, NS and NE-SW directions. Moreover, the area is dissected by basement uplifts and troughs controlled mainly by the NW-SE faults.

Abstract Seismic refraction studies have been carried out along several profiles through the Caledonian front in Jämtland in order to investigate the configuration of the Precambrian crystalline basement beneath the Caledonian sedimentary cover. The seismic sections were calculated according to the time-delay method and by assuming a linear increase of velocity with depth. Recordings from each of the 3 shotpoints along the profiles allowed the construction of continuous profiles. A method was applied whereby the basement velocity and the velocity gradients were varied until the best fit with respect to the calculated depths from different shotpoints was obtained. The seismic models are compared with drill-hole data, interpretation of aeromagnetic data and surface geology. Depths calculated from the seismic data compare well with the information from the few deep drillholes that reach down to the autochthonous basement. The magnetic and seismic models concur well along most of the profiles but differ greatly locally, thus demonstrating the importance of the application of various geophysical techniques, particularly when investigating complex stratigraphies, as in the Caledonides. Both the seismic and the magnetic models, suggest the existence of an undulating basement surface in the Caledonian front that coincides with some of the major folds in the sedimentary cover. East of the Offerdal synform the basement surface has previously been interpreted to dip gently (about 2°) westwards. The new seismic and magnetic data suggest a more irregular basement configuration than has previously been demonstrated. Key Words: Seismic surveysrefractionP-velocitytime-delaybasement structuresedimentary coverintegrated geophysicsCaledonianJämtlandcentral SwedenN6305N6430E1539E1252

Book Review| August 01, 2014 Geological Interpretation of Aeromagnetic Data (David J. Isles and Leigh R. Rankin) Geological Interpretation of Aeromagnetic Data. . David J. Isles. and Leigh R. Rankin. 2013. Australian Society of Exploration Geophysicists. E-book format on DVD: www.aseg.org.au/images/pages/Order form for Isles Rankin ebook.pdf. Price: AUD99 (members), AUD110 (non-members). Additional pricing given on website. Noel C. White Noel C. White P.O. Box 5181, Kenmore East, Qld Australia Search for other works by this author on: GSW Google Scholar Economic Geology (2014) 109 (5): 1495–1496. https://doi.org/10.2113/econgeo.109.5.1495 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Noel C. White; Geological Interpretation of Aeromagnetic Data (David J. Isles and Leigh R. Rankin). Economic Geology 2014;; 109 (5): 1495–1496. doi: https://doi.org/10.2113/econgeo.109.5.1495 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEconomic Geology Search Advanced Search Having access to high-quality detailed aeromagnetic surveys is a huge benefit to any geological work, whether academic or applied, and whether in igneous, metamorphic, or sedimentary environments. Continuous data of uniform quality, whether or not there is outcrop, irrespective of the intensity of weathering, and unaffected by who controls surface rights and access, is an immensely valuable resource for geologists. Our capacity to use the data depends on knowing how. The rationale for this book is clearly stated in the first two sentences of the Preface: “This book aims to help you to extract maximum value from aeromagnetic survey data.... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Conclusion: An action plan for coastal plain wetland conservation. Toward a continental conservation strategy

Research Article| July 01, 1988 Detached strata in a Tertiary low-angle normal fault terrane, southeastern California: A sedimentary record of unroofing, breaching, and continued slip Julia M.G. Miller; Julia M.G. Miller 1Department of Geology, Vanderbilt University, Nashville, Tennessee 37235 Search for other works by this author on: GSW Google Scholar Barbara E. John Barbara E. John 2Department of Earth Sciences, Cambridge University, Cambridge CB2 3EQ, England Search for other works by this author on: GSW Google Scholar Geology (1988) 16 (7): 645–648. https://doi.org/10.1130/0091-7613(1988)016<0645:DSIATL>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Julia M.G. Miller, Barbara E. John; Detached strata in a Tertiary low-angle normal fault terrane, southeastern California: A sedimentary record of unroofing, breaching, and continued slip. Geology 1988;; 16 (7): 645–648. doi: https://doi.org/10.1130/0091-7613(1988)016<0645:DSIATL>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Miocene sedimentary strata exposed in the eastern Chemehuevi Mountains, southeastern California, record development of an evolving low-angle normal fault system. The sequence includes more than 1 km of conglomerate and sandstone with rare interbedded monolithologic breccia and volcanic flows. Clasts of Peach Springs Tuff in basal units indicate that this succession is younger than 18 Ma. These rocks have been displaced by a regionally extensive low-angle normal fault, the Chemehuevi detachment, and are folded and faulted. Structural reconstructions and the character of associated fault rocks indicate that the Chemehuevi fault was initiated at a low angle and that the footwall was progressively unloaded through thinning and displacement of its cover during extensional deformation. The syntectonic sedimentary rocks described here provide evidence that movement continued on the gently dipping (< 15°) fault even after part of the fault was breached and the footwall eroded.The conglomerates and sandstones were deposited by stream flow and debris flow on alluvial fans. Synsedimentary faulting is suggested by angular discordance below one monolithologic breccia bed and by local coarsening-upward sequences. Clast types reveal progressive unroofing of hanging-wall rocks to expose the Chemehuevi fault zone, from which chloritic, brecciated granite clasts were derived. Clasts were then derived from both the hanging wall and the footwall, footwall debris being dominant high in the section. Distinctive clasts show that late displacement on this evolving fault system was on the order of 1 to 5 km. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Research Article| May 01, 2012 Vertical injectites of detachment carbonate ultracataclasite at White Mountain, Heart Mountain detachment, Wyoming John P. Craddock; John P. Craddock * 1Geology Department, Macalester College, St. Paul, Minnesota 55105, USA *E-mail: Craddock@Macalester.edu. Search for other works by this author on: GSW Google Scholar Jesse Geary; Jesse Geary 1Geology Department, Macalester College, St. Paul, Minnesota 55105, USA Search for other works by this author on: GSW Google Scholar David H. Malone David H. Malone 2Department of Geography, Geology, Illinois State University, Campus Box 4400, Normal, Illinois 61790, USA Search for other works by this author on: GSW Google Scholar Author and Article Information John P. Craddock * 1Geology Department, Macalester College, St. Paul, Minnesota 55105, USA Jesse Geary 1Geology Department, Macalester College, St. Paul, Minnesota 55105, USA David H. Malone 2Department of Geography, Geology, Illinois State University, Campus Box 4400, Normal, Illinois 61790, USA *E-mail: Craddock@Macalester.edu. Publisher: Geological Society of America Received: 10 Aug 2011 Revision Received: 03 Jan 2012 Accepted: 05 Jan 2012 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2012 Geological Society of America Geology (2012) 40 (5): 463–466. https://doi.org/10.1130/G32734.1 Article history Received: 10 Aug 2011 Revision Received: 03 Jan 2012 Accepted: 05 Jan 2012 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation John P. Craddock, Jesse Geary, David H. Malone; Vertical injectites of detachment carbonate ultracataclasite at White Mountain, Heart Mountain detachment, Wyoming. Geology 2012;; 40 (5): 463–466. doi: https://doi.org/10.1130/G32734.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Carbonate ultracataclasite (CUC) is found as a veneer along the bedding plane portion of the Eocene Heart Mountain detachment (Wyoming, United States). At White Mountain, where the CUC is thickest, we report the discovery of six dikes, as much as 1 m wide, that were intruded vertically ∼120 m from the detachment into the overlying Madison and Bighorn Formations. The horizontal basal detachment and injectite material is texturally, petrographically, geochemically, and isotopically identical, containing sparse, sand- to pebble-sized andesitic clasts, various quartz-calcite melt spherules, and armored lapilli in a matrix (95%) of fine-grained calcite. The relationship of hanging wall displacement to fault gouge generation, and the presence of vertical, 120 m, fault gouge injectites, makes the Heart Mountain slide anomalous to all fault systems, especially as this fault system had only one episode of motion. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Research Article| September 01, 1972 Developmental Model for the Southern Appalachians ROBERT D HATCHER, JR. ROBERT D HATCHER, JR. Department of Chemistry and Geology, Clemson University, Clemson, South Carolina 29631 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1972) 83 (9): 2735–2760. https://doi.org/10.1130/0016-7606(1972)83[2735:DMFTSA]2.0.CO;2 Article history received: 19 Aug 1971 rev-recd: 28 Feb 1972 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation ROBERT D HATCHER; Developmental Model for the Southern Appalachians. GSA Bulletin 1972;; 83 (9): 2735–2760. doi: https://doi.org/10.1130/0016-7606(1972)83[2735:DMFTSA]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract A developmental model is proposed for the southern Appalachians. This model integrates current ideas on structure, sedimentation, metamorphism, and igneous activity with the concept of plate tectonics.Progressive metamorphism culminated about 1,000 m.y. ago (middle Precambrian) and again about 400 m.y. ago (Silurian-Devonian). Later, localized retrogressive metamorphism affected the rocks of the Blue Ridge and Piedmont. Igneous activity occurred during the middle Precambrian (1,000 m.y. ago), prior to, during, and after Paleozoic regional metamorphism, and during the Mesozoic.The Valley and Ridge and Cumberland Plateau structures are treated as areas deformed by thin-skinned tectonics generated during the late Paleozoic, as is the Blue Ridge thrust sheet. The Blue Ridge anticlinorium, Murphy syncline, Chauga belt, mobilized Inner Piedmont, Kings Mountain belt, Charlotte and Carolina slate belts developed during the deformational event accompanying early-mid-Paleozoic regional metamorphism. The Blue Ridge anticlinorium, mobilized Inner Piedmont and Charlotte belts are interpreted as anticlinoria composed of middle Precambrian basement and later Precambrian metasedimentary and metavolcanic rocks mobilized to a greater or lesser degree. The Murphy, Chauga, Kings Mountain, and Carolina slate belts are inferred to be synclinoria composed of younger (late Precambrian to early-mid-Paleozoic) metasedimentary and metavolcanic rocks.The development of the sedimentary, deformational, metamorphic, and intrusive history of the southern Appalachians may be directly related to the Paleozoic history of movement of the North American and African continents as portions of major Paleozoic lithospheric plates. This developmental scheme is divisible into several phases: (1) An early (late Precambrian to mid-Ordovician) phase of continental margin sedimentation, igneous activity, and initial compression occurred. (2) This was followed by an intermediate (late Precambrian to late Devonian) phase of compression producing isoclinal folding, regional metamorphism, and intrusive activity with deposits from a rising tectonic source land. These phenomena are the direct result of westward underflow of a proto-Atlantic plate beneath an eastward-moving proto-North American plate with concomitant development of a subduction zone along the continental margin. (3) Next a later (mid-late Paleozoic) phase of compression and igneous activity accompanied by continued deposition from the rising mountain system occurred. The Brevard Zone, Towaliga, Goat Rock, and Gold Hill faults developed early in phase 3 and experienced renewed movement during formation of the thrusts and folds in the Valley and Ridge, Cumberland Plateau, and the late structures in the Blue Ridge. Compressional stresses that formed these structures were generated during the collision and suturing of Africa with southeastern North America. (4) Finally, there was a tensional phase (Triassic-Jurassic) accompanied by normal faulting, igneous activity, and deposition related to the decoupling of Africa and North America and the formation of the present Atlantic Ocean and continental margin. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.

Estimates of seismic hazard are strongly influenced by the location and recurrence of large earthquake events. Understanding such events is inherently difficult because recurrence intervals for large events in a given intra-plate region are typically much greater than the period over which earthquakes have been instrumentally recorded. Consequently, there is often very little data with which to robustly estimate seismic hazard. One way of enlarging the dataset is to study pre-historic large events using palaeoseismological methods, and there are many probable palaeo-fault scarps in the southwest of Western Australia. Studying these, along with historic fault scarps, places constraints on the geological setting of large events. The Southwest Seismic Zone is a belt of intra-plate seismic activity within the southwest of Western Australia. The local geological environment comprises deeply weathered Archaean granitoids and supracrustals. Outcrop is extremely sparse. The geological setting of large seismic events is best determined using high-resolution aeromagnetic data. These data allow bedrock geology to be mapped, and in particular identify structures that have been reactivated. This is the first step in establishing whether particular areas are more prone to large events than others. The 1968 Meckering earthquake (MS 6.8) resulted in an extensive and complex pattern of surface faulting, comprising faults with a range of orientations with reverse and dextral lateral offsets. Interpretation of new aeromagnetic data show that the surface faulting correlates closely with linear magnetic anomalies, interpreted as dykes/faults and lithological contacts/faults. The geometry of the surface faulting can be explained in terms of the reactivation of northeasterly and northwesterly trending surfaces in a stress regime with an east-west oriented maximum principal stress. Space problems created where these two trends converge led to the creation/reactivation of a linking north-south trending thrust fault which accommodated the greatest vertical displacements recorded for the 1968 event.