DOCSLIB.ORG

Letter Regarding the Status of Open File Report Entitled, "Basin & Range-Age Reactivation of Rocky Mountain Structures

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Letter Regarding the Status of Open File Report Entitled, # I 2 BUREAU OF ECONOiC GEOLOGY THE UNIVERSITY OF TEXAS AT AUSTIN W'M OCKET N0TROL lSt To78713-750-(512)471-1534or471-7721(jZE *87 JIN -9 A1O:26 June 1, 1987 WM RecorgFile WM Project / /WI Docket No. 13 Dr. Theodore J. Taylor Salt Repository Project Office )rLPDRt adI9 n _ __ ta_ . U. 3* Uepdriinent UT Energy Dii b.iO 110 North 25 Mile Avenue _ _______- Hereford, TX 79045 Reference: Contract No. DE-AC97-83WM466t M __ ______ Dear Dr. Taylor: Per a request from Susan Heston to Chris Lewis, the status of the open-file report entitled *Basin and Range-Age Reactiviation of Rocky Mountain Structures in the Texas Panhandle, (OF-WTWI-1986-3),m by R. Budnik, is as follows. Dr. Budnik left the Bureau in August, 1986. The manuscript was revised by Dr. Budnik to reflect comments from GSA reviewers and resubmitted to the Journal before DOE comments were received at the Bureau. The article was published in the February, 1987 issue of Geology. Please note the title of the article was changed, it is now entitled nLate Miocene Reactivation of Ancestral Rocky Mountain Structures in the Texas Panhandle: A Response to Basin and Range Extension." Three copies of the reprinted article are enclosed. Also, the above referenced article supersedes OF-WTWI-1986-3. If you have any questions, please do not hesitate to contact me. Sincerely, Asoc iat cto Associate Director DCR:CL:cl Enclosures cc: P. Archer (BPMD) S. Heston (SRPO) F. Brown C. Lewis T. Clareson (BPMD/GRC) J. Raney S. Doenges F. Ross (NRC) L. Drover (BPMD/TIC) E. Washer (S&W) J. Ellenberger (SRPO) J.3 Williams (SRPO) L. Harrell - QA Files R. Helgerson (BMI/ONWI) --- 88123035 IMProjecti UN-16 OM Record File: 106 LPIR w/encl 6712I00O2 870601 E FDR Owl PDR AT PDR (Return to UK, 623-SS) 1416 / 710 Late Miocene reactivation of-Ancestral Rocky Mountain structures in the Texas Panhandle: A response to Basin and Range extension 3. Roy T. Budnik* Bureau of Economic Geology. University of Texas University Station Box X, Austin, Texas 78713 ABSTRACT Structural and stratigraphic evidence from the Ogallala Formation (Neogene) documents late Miocene tectonic activity within the Great Plalns Field and mibsurface studies hi the Texas Panhandle Indicate that parts .f the Adulo uplift, amajor element of the Penn- __ sylvanian Ancestral Rocky Mountains, were elevated as much as 150 mduring Initial dep- osition of the Ogallala Formation. Beactiva- I. lion of these basement structures occurred In response to Basin and Range extension and opening of the Rio Grande rift hi central New Mexico and Colorado. INTRODUCTION Investigations in the Texas Panhandle docu- ment late Tertiary tectonism within the Great Plains, more than 300 km beyond the known limits of contemporary Basin and Range faulting in central New Mexico. Evidence of tectonic activity within the panhandle comes primarily from the Ogallala Formation, a vast alluvial apron that was shed eastward from mountains bordering the Rio Grande rift in central New Mexico and. Colorado during Neogene time (Fig 1). Previous work in the panhandle sug- gested that distribution of the Ogaflala was con- trolled primarily by preexisting topography and by subsidence related to the dissolution of under- :::v: 2 lying evaporites (Seni, £980-, Gustavson and - Budnlk, 1985). However, recent neotectonic studies, part of alarger program examining the 22 2: * . 22 :1 it ::: kasihihty of siting a high-level nuclear waste repository in the Texas Panhandle, has shown 222 222 322. thatatleastlocallytectonicprocessesalsoaf- fected the distribution and structural attitude of the Ogallala Formation. This paper reports on research conducted along the Amarillo uplift in the central panhandle about 75 km northeast of fhenw,,,Afiwtnvvtp .4 ICOhu 0A6062 FIgure 1. BasIn and Range province of western United Stat.. (lop) and distribution of Neogene sediments hi southern Rocky Mountains and western Great Plains (bottom). 'Present addrem RRl, Box 440.Aincnia, New Heavy fines In bottom figure are pm-Cenozoic faults. York 12501. GEOLOGY, v. 15,p. 163-166, Febnuy 1987 163 I STRUCTURAL GEOLOGY OF THE High Plains (SchulZ 1977). The overlying Co- can (Pliocene) lacustrine deposits (Schultz, AMARILLO UPL1F etas Formation contains a Clarendonian verte- 1977) to the south of the uplift. The Amarillo uplift isa narrow basement pos- brate fauna (Schultz, 1977). Paleoctologic and itive element that is part of a complex zone of isotopic data indicate that Ogallala deposition LATE TERTIARY DEFORMATION horsis and grabens extending west-northwest- ended during the Hemphillian Stage (late Ml- IN THE TEXAS PANHANDLE ward won the Texas Panhandle (Fig. 2). The ocene/early Pliocene) 4 to S Ma (Izett, 1975). Structures along the Amarillo uplift appear to Amarillo uplift and colinear Wichita uplift to The upper part of the OgalIala Formation is have been unaffected by the Laramide orogeny the southeast in Oklahoma form the southern undated in the vicinity of the uplift, but it is to the west, as indicated by parallelism of bed- margin of the Anadarko basin and are pert of lithologicafly similar to and in the same strati- ding in the lower part of the Ogallala Formation the Pennsylvanian Ancestral Rocky Mountain graphic position as the Dridwell Formation and underlying units. However, Permian, Tries- erogenic belt that extends from Oklahoma to (Evans, 1949) to the south, which is Hemphill- sic, and lower Ogallala strata dip as much as 1? Utah (ver Wiebe, 1930). Left-lateral motion of un in age (Winkler, 1985). Isotopic ages rang- off the southwest flank of the John Ray dome, as much as 120 km during the Pennsylvanian is ing from 4.5 to 6.6 Ma were obtained from ash documenting reactivation of the older structures indicated by the offset of lower Paleozoic strata beds near the top ofthe Ogallala Formation in after initiation of Ogallala deposition. An angu- seross the uplift (Budnlh, 1986). Hemphill County, just north of the uplift (Izett, hr unconformity lies between the Tertiary and Several thousand metres of structural relief 1975). The Ogallala islocally overlain by BIan- older units higher on the dome, and the Ogallala developed between the Amariflo uplift and ad- jacent basins to the northeast (Anadarko) and southwest (Whittenburg trough; Fig. 2) during the Pennsylvanian and Early Permian Reactiva- tion of Pennsylvanian structures since the Pa- leozoic is indicated by faulting of the Triassic Dockum Group against Permian strata won the Potter County fault, which separates the Wbittenburg trough from the Amarillo uplift. In addition, middle and Upper Permian and Tries- sic strata have been folded over en echelon basement horats (for example, the Exell and John Ray domes; Fig. 2) along the upthrown side of the fault. The Ogaflala Formation also has been folded this suggests that at least some of the deformation occurred in the Cenozoic. 5 4 n .I FCIUII. boll wadownllwown sade LATE TERTIARY SYNTECTONIC DEPOSITION IN THE TEXAS Saa,.es, conto interval 1000 ft. 10000 ft Anodorl.o Basin PANHANDLE Along the Amarillo uplift, basal Ogaflala sands and gravels (called the Potter Formation; Patton, 923) include well-rounded siliceous clasts as large as 30 omin diameter transported from mountains along the eastern margin of the Rio Grande rift (Schultz, 1977). as well as blocks of dolomite and red mudstoce up to 45 cm in diameter derived from underlying Permian strata. The Potter Formation is more than 100 m thick within the Whittenburg trough, but thins abruptly onto the Amarillo up. lift woes the Potter County fault (Fig. 3). The unit is conformably overlain within the trough by finely laminated calcareous slltstone and mudstone (Coetas Formation; Patton, 1923). Undifferentiated upper Ogallala sand, silt, and W14T1ENBt.UG caliche blanket the entire area, including the ThcuG folds a4jacent to the Potter County fault. Toflay Ogollolo Fomaat.on EJ P,ftO1 lip Wallunirci Vertebrate fossil data from the Texas Pan- handle indicate onset of deposition of the Ogal- as tiassec Ooctwm Group meP.nruon strata . Fault lala Formation during the Clarendonian (late J Permian vaonles L Pcterczoac basement Miocene), about 10 Ma (Schultz, 1977; earn Winkler, 1985). The Potter Formation appar- FIgure 2. Structure contour map on top of basement (lop) and cross section of Amarillo uplift ently has no indigenous fauna preserved, but (bottom). BrO -Bravo dome; BuD - Bush dome; CB - Carson basin; JRO -John Ray dome; LFB Lefora basin; WDG - White Deer graben; WT - Whlttenburg trough; XLD - Exell dome. Uplift of worn Gryphaea (Early Cretaceous) fragments Exell dome occurred prior to deposition of upper part of Ogallala Formation. Evidence to east are common in itand other basal Ogallala (Qar- (see Fig. 3) suggests that deformation took place during deposition @1lower Ogallala units endonian) deposits throughout the southern (Potter and Coetas Formations). which are not present along this En. of section. 164GEOLOGY. Febnuiy 1987 I%.% / fls sucusszvdy on the Dockum Group, or Extension across the Rio Grande rift wasac- proposed many years ago (ver Webe, 1930) 7erniian Strata, and Emily cc eroded Permiar commodated in part by reactivation of preexist- and termed variously the Wichita lineansent mcntheapexeicrure(Fig.3).k ing fault zones (Eaton, 1979; Tweto, 1979; (Sales, 1968), the Wichita megashear (Walper, 8ddition, the Ogaflala appears to lap onto thr Cordefi, 1982; Baldridge et a!, 1984). Faults 1970; Budnlk, 1986). the Olympic-Wichita Un- * dome so that the Potter Formation rests on thr associated with the north-northwest-trending Lament (Baars, 1976), and the Oklahoma-New Dockum Group within the Whitzenburg trough * Use-Gore fault system (Tweto, 1980) influenced Mexico-Colorado-Utah tectonic zone ([arson whereas the upper unit of the Ogalala rests di* the location of small, discontinuous rift basins in at aL, 1985). The use-Gore and Apishapa fault reedy on Perniian strata on the apex of the Johr central and northern Colorado (Fig.
Load more

Recommended publications
  • Bilek Earth and Environmental Sciences Dept
    Susan L. Bilek Earth and Environmental Sciences Dept. New Mexico Institute of Mining and Technology, Socorro, NM 87801 Email: [email protected] Webpage: https://nmt.edu/academics/ees/faculty/sbilek.php Professional Preparation: B.S., with honors, Geosciences, minor in Economics, Penn State University, May 1996 M.S., Earth Sciences/Geophysics, University of California, Santa Cruz, June 1998 M.S. Thesis title: Lower mantle heterogeneity beneath Eurasia imaged by parametric migration of shear waves Ph.D. Earth Sciences/Geophysics, University of California, Santa Cruz, June 2001 Ph.D. Dissertation title: Multi-scale examination of seismogenic zone processes in circum- Pacific subduction zones Turner Postdoctoral Fellow, Dept. Geological Sciences, University of Michigan, 2001-2003 Appointments: Professor, Earth and Environmental Science Dept., New Mexico Tech, 2014 – present Associate Professor, Earth and Environmental Sciences Dept., New Mexico Tech, 2008 – 2014 Assistant Professor, Earth and Environmental Sciences Dept., New Mexico Tech, 2003 – 2008 Selected Recent Synergistic Activities: National/International: Board of Directors, Seismological Society of America, 2020-2022 Associate Editor, Geophysical Research Letters, 2020-present Editorial Board, Tectonophysics, 2016-present Associate Guest Editor, Subduction Top to Bottom 2, special issue of Geospheres, 2016-present PI of IRIS PASSCAL Instrument Center, Oct 2013-present IRIS Board of Directors, 2010-2012, Board secretary 2012 Reviewer: NSF, NNSA, Science, Science Advances, Nature,
    [Show full text]
  • Cenozoic Thermal, Mechanical and Tectonic Evolution of the Rio Grande Rift
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 91, NO. B6, PAGES 6263-6276, MAY 10, 1986 Cenozoic Thermal, Mechanical and Tectonic Evolution of the Rio Grande Rift PAUL MORGAN1 Departmentof Geosciences,Purdue University,West Lafayette, Indiana WILLIAM R. SEAGER Departmentof Earth Sciences,New Mexico State University,Las Cruces MATTHEW P. GOLOMBEK Jet PropulsionLaboratory, CaliforniaInstitute of Technology,Pasadena Careful documentationof the Cenozoicgeologic history of the Rio Grande rift in New Mexico reveals a complexsequence of events.At least two phasesof extensionhave been identified.An early phase of extensionbegan in the mid-Oligocene(about 30 Ma) and may have continuedto the early Miocene (about 18 Ma). This phaseof extensionwas characterizedby local high-strainextension events (locally, 50-100%,regionally, 30-50%), low-anglefaulting, and the developmentof broad, relativelyshallow basins, all indicatingan approximatelyNE-SW •-25ø extensiondirection, consistent with the regionalstress field at that time.Extension events were not synchronousduring early phase extension and were often temporally and spatiallyassociated with major magmatism.A late phaseof extensionoccurred primarily in the late Miocene(10-5 Ma) with minor extensioncontinuing to the present.It was characterizedby apparently synchronous,high-angle faulting givinglarge verticalstrains with relativelyminor lateral strain (5-20%) whichproduced the moderuRio Granderift morphology.Extension direction was approximatelyE-W, consistentwith the contemporaryregional stress field. Late phasegraben or half-grabenbasins cut and often obscureearly phasebroad basins.Early phase extensionalstyle and basin formation indicate a ductilelithosphere, and this extensionoccurred during the climax of Paleogenemagmatic activity in this zone.Late phaseextensional style indicates a more brittle lithosphere,and this extensionfollowed a middle Miocenelull in volcanism.Regional uplift of about1 km appearsto haveaccompanied late phase extension, andrelatively minor volcanism has continued to thepresent.
    [Show full text]
  • Article (PDF, 237
    Workshop White Papers Sci. Dril., 18, 19–33, 2014 www.sci-dril.net/18/19/2014/ doi:10.5194/sd-18-19-2014 © Author(s) 2014. CC Attribution 3.0 License. Drilling to investigate processes in active tectonics and magmatism J. Shervais1, J. Evans1, V. Toy2, J. Kirkpatrick3, A. Clarke4, and J. Eichelberger5 1Utah State University, Logan, Utah 84322, USA 2University of Otago, P.O. Box 56, Dunedin 9054, New Zealand 3Colorado State University, Fort Collins, Colorado 80524, USA 4Arizona State University, Tempe, Arizona 85287, USA 5University of Alaska, Fairbanks, Fairbanks, Alaska 99775, USA Correspondence to: J. Shervais ([email protected]) Received: 7 January 2014 – Revised: 5 May 2014 – Accepted: 19 May 2014 – Published: 22 December 2014 Abstract. Coordinated drilling efforts are an important method to investigate active tectonics and magmatic processes related to faults and volcanoes. The US National Science Foundation (NSF) recently sponsored a series of workshops to define the nature of future continental drilling efforts. As part of this series, we convened a workshop to explore how continental scientific drilling can be used to better understand active tectonic and magmatic processes. The workshop, held in Park City, Utah, in May 2013, was attended by 41 investigators from seven countries. Participants were asked to define compelling scientific justifications for examining problems that can be addressed by coordinated programs of continental scientific drilling and related site investigations. They were also asked to evaluate a wide range of proposed drilling projects, based on white papers submitted prior to the workshop. Participants working on faults and fault zone processes highlighted two overarching topics with exciting po- tential for future scientific drilling research: (1) the seismic cycle and (2) the mechanics and architecture of fault zones.
    [Show full text]
  • The Plate Boundary Observatory
    The Plate Boundary Observatory Results of the First Workshop on Geological Research Held at Pasadena, California May 22-25, 2001 Submitted by PBO Geology Committee Douglas Burbank Ken Hudnut (PBO Steering Committee) Rick Ryerson Charles Rubin PBO Geology White Paper/Page 1 David Schwartz (Chair) Brian Wernicke (PBO Steering Committee) Steve Wesnousky Introduction The diffuse plate boundary zone of the western US and Alaska consists of hundreds of active tectonic elements that collectively accommodate large-scale relative motions between the North American, Pacific and Juan de Fuca plates (Figure 1). The major plate-bounding structures include the San Andreas transform and the Alaskan and Cascadia subduction zones, which accommodate most of the relative plate motion. Each of these features is a system of faults, each of which either fails in repeated large earthquakes or creeps aseismically. In addition to these fault systems, areally extensive structural domains within the North American plate, such as the Basin and Range province, Rio Grande rift, Rocky Mountains and interior Alaska accommodate up to 30% of the relative plate motion (Figure 1). PBO Geology White Paper/Page 2 Figure 1. Tectonic setting of the Pacific-Juan de Fuca-North America plate boundary system, showing major fault systems and locations of proposed geodetic instrumentation. Courtesy of PBO Steering committee. The life-cycle of an individual fault zone lasts on the order of 1 to 10 Myr, and the repeat times of major earthquakes (durations of the seismic cycle) are on the order of hundreds to thousands of years or more. Hence any attempt to understand tectonic systems must include observations on these time scales.
    [Show full text]
  • In the Southern Cascadia Subduction Zone Lucy M
    A possible “window of escape” in the southern Cascadia subduction zone Lucy M. Flesch* Department of Earth and Atmospheric Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, Indiana 47907, USA Understanding the forces and factors that are responsible for deform- 50°N ing the conti nental lithosphere remains a fundamental issue in geo physics. Deformation in continental plate boundary zones occurs over length scales of hundreds to thousands of kilometers, in contrast to oceanic plate North American Plate boundaries, where earthquakes are in most cases limited to much nar- rower zones. It is because of this typically diffuse nature that previous 30 mm/yr plate kinematic techniques have been limited in their ability to resolve surface motions within zones of continental deformation. However, with the proliferation of global positioning system (GPS) instrumentation over the past 20 yr, the kinematics and dynamics of these previously enigmatic 45° regions are coming into focus. One of the largest and most studied continental plate boundary zones is western North America, where the Pacifi c plate is grinding northwestward with respect to the North American plate, generating the Plate Juan de Fuca San Andreas fault system (Fig. 1). Finding a complete explanation for B&R the tectonics of this region is complicated by the subduction of the Juan Subduction Zone Cascadia de Fuca plate beneath the Pacifi c Northwest, and evidence that eastward of the San Andreas, the Basin and Range province (BRP) has under- 40° gone ~100% extension.
    [Show full text]
  • Field-Trip Guide to the Vents, Dikes, Stratigraphy, and Structure of the Columbia River Basalt Group, Eastern Oregon and Southeastern Washington
    Field-Trip Guide to the Vents, Dikes, Stratigraphy, and Structure of the Columbia River Basalt Group, Eastern Oregon and Southeastern Washington Scientific Investigations Report 2017–5022–N U.S. Department of the Interior U.S. Geological Survey Cover. Palouse Falls, Washington. The Palouse River originates in Idaho and flows westward before it enters the Snake River near Lyons Ferry, Washington. About 10 kilometers north of this confluence, the river has eroded through the Wanapum Basalt and upper portion of the Grande Ronde Basalt to produce Palouse Falls, where the river drops 60 meters (198 feet) into the plunge pool below. The river’s course was created during the cataclysmic Missoula floods of the Pleistocene as ice dams along the Clark Fork River in Idaho periodically broke and reformed. These events released water from Glacial Lake Missoula, with the resulting floods into Washington creating the Channeled Scablands and Glacial Lake Lewis. Palouse Falls was created by headward erosion of these floodwaters as they spilled over the basalt into the Snake River. After the last of the floodwaters receded, the Palouse River began to follow the scabland channel it resides in today. Photograph by Stephen P. Reidel. Field-Trip Guide to the Vents, Dikes, Stratigraphy, and Structure of the Columbia River Basalt Group, Eastern Oregon and Southeastern Washington By Victor E. Camp, Stephen P. Reidel, Martin E. Ross, Richard J. Brown, and Stephen Self Scientific Investigations Report 2017–5022–N U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior RYAN K. ZINKE, Secretary U.S.
    [Show full text]
  • Seismic Anisotropy of the Rio Grande Rift and Surrounding Regions
    Seismic anisotropy of the Rio Grande Rift and surrounding regions Tia Barrington and Jay Pulliam, Baylor University The evolution of distinct tectonic provinces in the southwestern United States since the Cretaceous, including the Great Plains, the Colorado Plateau, and the Rio Grande Rift (RGR), has been linked to flat subduction of the Farallon plate (~80 Ma) and then its subsequent foundering (~40 Ma). However, there has been a resurgence in tectonic activity (magmatism, extension, and possibly uplift) much more recently (~10 Ma), so there is no clear connection between the Farallon plate’s foundering and present tectonic activity. Small‐scale, edge‐driven convection is a possible explanation for this renewed activity. Edge‐driven convection, if it is occurring, should extend to the north and south along the margin of the Proterozoic Great Plains craton. Convective flow should have a signature in the upper mantle’s seismic anisotropy and our goal is to determine whether patterns of anisotropy, as determined from SKS splitting that may be consistent with small‐scale convection. SKS splitting measurements were made for 126 broadband stations located on the eastern flank of the Rio Grande Rift. Seventy‐one of these stations were installed in 2008 as an Earthscope Flexible Array deployment called SIEDCAR; the remainderare EarthScope Temporary Array stations. SKS splitting patterns conform both to surface physiographic features as well as to models of the subsurface produced independently. Fast polarization directions near the Rio Grande Rift tend to be sub‐parallel to the RGR but then change to angles that are consistent with North America’s average plate motion, to the east.
    [Show full text]
  • Distributed Deformation Across the Rio Grande Rift, Great Plains, and Colorado Plateau
    Geology, 40(1), 23-26, 2012 Distributed Deformation across the Rio Grande Rift, Great Plains, and Colorado Plateau Henry T. Berglund1, Anne F. Sheehan2, Mark H. Murray3, Mousumi Roy4, Anthony R. Lowry5, R. Steven Nerem6, and Frederick Blume1 1UNAVCO Inc, 6350 Nautilus Drive, Boulder, Colorado 80301-5553, USA 2Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309-0399, USA 3Department of Earth and Environmental Science, New Mexico Tech, Socorro, New Mexico 87801, USA 4Department of Earth & Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131-1116, USA 5Department of Geology, Utah State University, Logan, Utah 84322-4505, USA 6Department of Aerospace Engineering Sciences, University of Colorado, Boulder, Colorado 80309-0429, USA ABSTRACT We use continuous measurements of GPS sites from across the Rio Grande Rift, Great Plains, and Colorado Plateau to estimate present-day surface velocities and strain rates. Velocity gradients from five east-west profiles suggest an average of ~1.2 nanostrains/yr east-west extensional strain rate across these three physiographic provinces. The extensional deformation is not concentrated in a narrow zone centered on the Rio Grande Rift but rather is distributed broadly from the western edge of the Colorado Plateau well into the western Great Plains. This unexpected pattern of broadly distributed deformation at the surface has important implications for our understanding of how low strain-rate deformation within continental interiors is accommodated. INTRODUCTION Global positioning system (GPS) monuments installed for the EarthScope Plate Boundary Observatory (PBO) and the Rio Grande Rift GPS experiment (Fig. 1) have greatly enhanced modern geodetic coverage of the physiographic regions of the Rio Grande Rift and the Colorado Plateau.
    [Show full text]
  • Cooling Histories of Mountain Ranges in the Southern Rio Grande Rift Based on Apatite Fission-Track Analysis—A Reconnaissance Survey
    Cooling histories of mountain ranges in the southern Rio Grande rift based on apatite fission-track analysis—a reconnaissance survey by Shari A. Kelley, Dept. of Earth and Environmental Sciences, New Mexico Institute of Mining & Technology, Socorro, NM 87801-4796; and Charles E. Chapin, New Mexico Bureau of Mines & Mineral Resources, Socorro, NM 87801-4796 Abstract Fifty-two apatite fission-track (AFT) and two zircon fission-track ages were deter- mined during a reconnaissance study of the cooling and tectonic history of uplifts asso- dated with the southern Rio Grande rift in south-central New Mexico. Mack et al. (1994a, b) proposed that the southern rift has been affected by four episodes of extension beginning at about 35 Ma. The main phases of faulting started in the late Eocene, the late Oligocene, the middle Miocene, and the latest Miocene to early Pliocene, with each phase disrupting earlier rift basins and in some cases reversing the dip of the early rift half-grabens found in the vicinity of the southern Caballo Mountains. The timing of denudation derived from AFT data in the Caballo, Mud Springs, San Diego, and Dona Ana mountains are consistent with the episodes of uplift and erosion preserved in the Oligocene to Miocene Hayner Ranch and Rincon Valley Formations in the southern Caballo Mountains. Each mountain block studied in the southern rift has a unique history. AFT ages in the Proterozoic rocks on the east side of the San Andres Mountains record cooling of this mountain block at 21 to 22 Ma in re- sponse to the phase of extension that began in the late Oligocene.
    [Show full text]
  • Downloaded from U.S
    85 84 Utah Geological Survey Western States Seismic Policy Council Pmceedings CONTRASTS BETWEEN SHORT- AND LONG-TERM RECORDS OF SEISMICITY cally <1-2 mm/year; thus, recunence intervals for surface rupturing fault are as little as several thousand years (e.g., IN THE RIO GRANDE RIFT-IMPORTANT IMPLICATIONS FOR SEISMIC­ the Wasatch fault zone) or as long as 10,000 years (e.g., a N ----1 typical Basin and Range fault) t I 00,000 years (e.g., HAZARD ASSESSMENTS IN AREAS OF SLOW EXTENSION Denver ome of the least active Quaternary fau lts in the Rio Grande rift). Obviously, the 150- to 300-year-long record :~ Colorado Michael N. Machette of felt seismicity only portrays a small fraction of the '\ I\ U.S. Geological Survey, MS 966 potentially active faults in these regions. I \ GP I I Geologic Hazards Team-Central Region I I I Finally, in even le s tectonically active regions, such CP SRM' ' ' Denver, Colorado 80225 as the pa i.ve margin of the ea tern U.S. and compres­ --r -~ -- l~ ([email protected]) sional domain of the stable continental interior of the , ~Taos i-- U.S., Canada, and Australia, fault slip rates are probably J- Los', ( 1 measured in hundredths of a mm/year, and intervals be­ Alamo~'• :Santa Fe I ABSTRACT tween surface rupturing events may be extremely long \ Arizona : , ~J 1 ., Albuquerque (>100,000 years) or immeasurable. However, these re­ I f,C~ \ I I I The Rio Grand rift ha a relatively hort and unimpres iv record of hi toricaJ eisouc1ty.
    [Show full text]
  • Smith-Konter, B., D. Sandwell, and M. Wei (2010
    inSights the EarthScope newsletter summer 2010 EarthScope NEWSNews Integrating GPS & InSAR to Resolve Stressing Rates Along the San Andreas System The absence of a major earthquake over the past three centuries along the southern San Andreas fault, a region home to over 10 million people and the site of large earthquakes in the past, provides ample motivation for studying the loading conditions of an active plate boundary. A comparison of strain rate maps of the western United States, produced by 15 research groups using primarily the same GPS measurements, reveals that modeled rates can differ by a factor of 5-8, with largest differences along the most active faults. Participants in the EarthScope San Andreas interpretive workshop (www.earthscope.org/eno/parks) show how New estimates of seismic hazard will rely on high compute continuous velocities before obtaining a the PBO-GPS station at CSU San Bernardino is moving resolution measurements of crustal deformation strain rate map. Simple dislocation models predict relative to North America. Photo by Shelley Olds and a secure understanding of strain rate derived that strain rate is proportional to slip rate divided ■ Register and apply for travel from such measurements. The growing archive by the locking depth, so even when using similar support by July 15 for the of EarthScope’s Plate Boundary Observatory slip rates, strain rates can differ by a factor of 2-3 EarthScope Institute on the (PBO) GPS data is uniquely positioned to provide because of different fault depth assumptions. Spectrum of Fault Slip Behaviors a large-scale perspective on plate boundary strain; October 11-14 in Portland, OR however it cannot accurately resolve the highest A collaborative effort involving 15 research groups (www.earthscope.org/workshops/ strain rates near the most active faults.
    [Show full text]
  • Rio Grande Rift--Problems and Perspectives W
    New Mexico Geological Society Downloaded from: http://nmgs.nmt.edu/publications/guidebooks/35 Rio Grande rift--Problems and perspectives W. Scott Baldridge, Kenneth H. Olsen, and Jonathan F. Callender, 1984, pp. 1-12 in: Rio Grande Rift (Northern New Mexico), Baldridge, W. S.; Dickerson, P. W.; Riecker, R. E.; Zidek, J.; [eds.], New Mexico Geological Society 35th Annual Fall Field Conference Guidebook, 379 p. This is one of many related papers that were included in the 1984 NMGS Fall Field Conference Guidebook. Annual NMGS Fall Field Conference Guidebooks Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico. Free Downloads NMGS has decided to make peer-reviewed papers from our Fall Field Conference guidebooks available for free download. Non-members will have access to guidebook papers two years after publication. Members have access to all papers. This is in keeping with our mission of promoting interest, research, and cooperation regarding geology in New Mexico. However, guidebook sales represent a significant proportion of our operating budget. Therefore, only research papers are available for download. Road logs, mini-papers, maps, stratigraphic charts, and other selected content are available only in the printed guidebooks. Copyright Information Publications of the New Mexico Geological Society, printed and electronic, are protected by the copyright laws of the United States.
    [Show full text]