DOCSLIB.ORG

Volume 66, Number 1, Fall 2004

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Volume 66, Number 1, Fall 2004 OREGON GEOLOGY Oregon Department of Geology and Mineral Industries Volume 66, Number 1, Fall 2004 DOME BUILDING ON MT. ST. HELENS ALSO IN THIS ISSUE: GEOLOGY AND HAZARD RESPONSE PLANS GLACIAL STRATIGRAPHY AND HISTORY OF THE BLUE RIVER DRAINAGE CRYSTAL SPRINGS ZONE OF CONTRIBUTION ALL DEPARTMENT BULLETINS AND OIL & GAS INVESTIGATIONS NOW AVAILABLE ON CD OREGON GEOLOGY VOLUME 66, NUMBER 1 FALL 2004 Contents From the State Geologist Geology and hazard response plans . .3 Mount St. Helens update . .4 Research Article Glacial Stratigraphy and History of the Blue River drainage, Lane County, Oregon: A stratigraphic study of glaciolacustrine sediments detailing reverse drainage glacial ice-margin oscillations and subsequent ice-dam failure similar to a small-scale Missoula Flood event . .5 Crystal Springs Zone of Contribution, Crystal Springs Water District, Odell, Oregon . .15 Publications Bulletins and Oil & Gas Investigations now on CD . .16 New DOGAMI Publications . .21 Thesis/Dissertation Abstract Feeder Dikes to the Columbia River Flood Basalts: Underpinnings of a Large Igneous Province . .23 To Order Publications . .24 OREGON DEPARTMENT OF GEOLOGY AND MINERAL INDUSTRIES Governing Board Grants Pass Field Office: 5375 Monument Drive, Grants Pass 97526, William M. Elliott, Chair . Lake Oswego phone (541) 476-2496, FAX (541) 474-3158. Donald A. Haagensen, Vice Chair . Portland Thomas J. Wiley, Southwest Oregon Section Leader. Steven McNab . Bend Mineral Land Regulation and Reclamation Program: 229 Broadal- Vera E. Simonton . Pendleton bin Street SW, Albany 97321-2246, phone (541) 967-2039, FAX (541) Barbara P. Seymour . Salem 967-2075. Gary W. Lynch, Assistant Director of Regulation. State Geologist . Vicki S. McConnell Nature of the Northwest Information Center: Suite 177, 800 NE Assistant Director . Don Lewis Oregon St. # 5, Portland, OR 97232-2162, phone (503) 872-2750, FAX (503) 731-4066. Internet: http://www.naturenw.org Produced by the Public Education Section of the Department Donald J. Haines, Manager. Main Office: Suite 965, 800 NE Oregon Street # 28, Portland Permission is granted to reprint information contained herein. Credit 97232, phone (503) 731-4100, fax (503) 731-4066. given to the Oregon Department of Geology and Mineral Industries for Internet: http://www.oregongeology.com compiling this information will be appreciated. Baker City Field Office: 1510 Campbell Street, Baker City 97814, Information and conclusions in these articles are the responsibility of the phone (541) 523-3133, FAX (541) 523-5992. author, and are not necessarily shared by the Department and its staff. Mark L. Ferns, Eastern Oregon Section Leader. Coastal Field Office: 313 SW Second Street, Suite D, Newport 97365, phone (541) 574-6642, FAX (541) 265-5241. Jonathan Allan, Coastal Section Leader. On the Cover Mount St. Helens new growth, from the north. USGS Photograph taken on November 29, 2004, by Jim Vallance and Matt Logan. Oregon Geology (ISSN 0164-3304) is published by the Oregon Department of Geology and Mineral Industries on its web site http://oregongeology.com. (Volumes 1 through 40 were entitled The Ore Bin.) OREGON GEOLOGY, VOLUME 66, NUMBER 1, FALL 2004 2 FROM THE STATE GEOLOGIST, DR. VICKI S. McCONNELL Geology and hazard response plans Although the awakening of Mount St. Helens is not A more challenging volcano response plan involves the only geologic activity that has occurred in or near the threat to the communities and resources in the our state in the last year, it certainly created the Central Cascades. From Mount Jefferson to Newber- biggest stir. Why is that? Volcanoes certainly garner ry Volcano there are several volcanoes and volcanic a certain amount of curiosity and infamy in general; centers, with a wide scale of potentially hazardous that attention increases during an eruption. Other types of eruptions and erupted materials. The hazard events like minor earthquakes or the opening or clos- could impact communities on both sides of the Cas- ing of quarries are not considered front page news. cades. A more pragmatic reason for the notice associated We do much more than volcano response plans. We with Mount St. Helens is the immediate impact of are assisting coastal communities with their planning policy decisions made to address the increase in for response to tsunami hazards. We research and risk—closing of visitor centers and restricting access map the extent of past tsunamis and model where to areas and roads. If you want the public to notice we would expect inundation from a future tsunami. something, just tell them they can’t go there! Then we help communities map evacuation routes and develop brochures to explain them to coastal res- The policy decisions made in response to the in- idents and visitors. creased risk of a volcanic eruption from Mount St. Helens were not arbitrary. They resulted from fol- Landslides, particularly fast-moving debris flows, are lowing a decision tree outlined in a coordinated haz- a common winter hazard, and call for a different type ard response plan for Mount St. Helens. Response of response plan. After several fatalities in 1996-98, a plans for geologic hazards are the logical outcome of debris flow warning system has been put in place, in- a basic part of DOGAMI’s mission—to identify and volving the Oregon Department of Forestry, Oregon characterize the geology of the state of Oregon. Emergency Management, and the National Weather Service. Rainfall is monitored, and when pre-estab- To me, the development of geologic hazards re- lished threshholds are reached, a debris-flow warn- sponse plans represents an excellent measure of the ing may be issued. Part of the response plan includes success of both our geologic work and our public ed- highway signs notifying travellers entering potential- ucation programs at DOGAMI. Writing a response ly dangerous areas. plan is done when you have learned of a hazard or threat and you determine there is enough informa- These are only a few of the various types of response tion available to make adequate decisions. plans that DOGAMI has been involved with. Com- munities, businesses, government agencies, and indi- The challenge in preparing any response plan is en- viduals can all benefit from planning their responses suring that proper organizations are involved in the to the many geologic hazards in Oregon. creation of the plan and that everyone has the neces- sary information to aid with decision making. Our work to expand and refine information about Oregon’s geology continues, as does our coordina- Here in Oregon we have our fair share of geologic tion with other agencies and organizations. Response hazards to plan for, including our own volcanoes. plans must be updated periodically to reflect current For example, DOGAMI staff serves as the state geolo- understanding. The more we know about the poten- gy representative to review and revise the Mount tial damage from specific geologic hazards, the more Hood Coordination Plan that is slated to be released we can all use our limited resources more wisely. early in 2005. If you would like to preview the plan, you may do so from our website, oregongeology.com, and click on the “Earthquakes and other natural hazards” page. OREGON GEOLOGY, VOLUME 66, NUMBER 1, FALL 2004 3 MOUNT ST. HELENS UPDATE BY VICKI S. MCCONNELL In late September and early October our most active was indeed migrating. This spurred the decision to volcano in the Cascade Range gave both geologists upgrade to alert level 3, a Volcano Alert. Johnson and emergency response personnel a real wake up Ridge Observatory was evacuated. Tremor blasts and call. Mount St. Helens has entered into a late stage of observable changes in the crater floor increased over dome building activity. Although this is a completely the next several days and on Tuesday, October 5 at normal phase in the life of an active stratovolcano, 9:00 am, a vigorous steam and ash explosion took after several years of negligible activity it seemed place that cleared several small vents. Seismicity quite spectacular. dropped off markedly and scientists assumed that the opening of the vents depressurized the system. Beginning on September 22, 2004 seismologists at the This allowed magma to be extruded to the surface, to US Geologic Survey Cascade Volcano Observatory begin a dome-building episode if enough lava were CVO) noted a marked increase in tiny, shallow earth- available. The volcano alert was downgraded to alert quakes located under the lava dome. By the next day level 2, a Volcano Advisory. hundreds of small (less than magnitude 1) earth- quakes were occurring and the observatory issued an Presently Mount St. Helens continues to extrude lava information statement about it. The earthquakes at the northern edge of the 1980-1986 dome, pushing were so shallow it was not clear if they were actually a spire upwards to over 76 m higher than the dome. occurring at the surface and might be associated with This poses some threat of collapse and formation of Horseshoe glacier that surrounds the dome. By Sep- pyroclastic flows and lahars down drainages. Analy- tember 26 both the frequency and magnitude of sis of bombs collected from the steam and ash emis- earthquake activity had increased enough that the sions indicate the lava is rhyolite. This would be ex- staff at CVO decided to issue a Notice of Volcanic Un- pected if the magma is the cooling product of the rest and the US Forest Service staff closed the flanks 1980-1986 chamber that has been cooling and evolv- of the volcano to hikers and climbers. ing. The volcano was pressurizing beneath the lava dome The volcano alert level remains at level 2, Volcano Ad- in response to fluid migration and there was a good visory; Johnson Ridge Observatory remains closed, chance a phreatic or phreatomagatic eruption could and we watch and wait as the mountain continues to occur.
Load more

Recommended publications
  • The Origin of the Columbia River Flood Basalt Province: Plume Versus Nonplume Models
    The Origin of the Columbia River Flood Basalt Province: Plume versus Nonplume Models Peter R. Hooper1, Victor E. Camp2, Stephen P. Reidel3 and Martin E. Ross4 1 Dept of Geology, Washington State University, Pullman, WA 99164 and Open University, Milton Keynes, MK7 6AA, U.K. 2 Dept of Geological Sciences, San Diego State University, San Diego, CA 92182 3 Washington State University Tri-Cities, Richland, Washington 99352 4 Dept of Earth and Environmental Sciences, Northeastern University, 360 Huntington Av., Boston, MA 02115 ABSTRACT As a contribution to the plume-nonplume debate we review the tectonic setting in which huge volumes of monotonous tholeiite of the Columbia River flood basalt province of the Pacific Northwest, USA, were erupted. We record the time-scale and the locations of these eruptions, estimates of individual eruption volumes, and discuss the mechanisms of sheet- flow emplacement, all of which bear on the ultimate origin of the province. An exceptionally large chemical and isotopic data base is used to identify the various mantle sources of the basalt and their subsequent evolution in large lower crustal magma chambers. We conclude by discussing the available data in light of the various deep mantle plume and shallow mantle models recently advocated for the origin of this flood basalt province and we argue that the mantle plume model best explains such an exceptionally large volume of tholeiitic basalt erupted over an unusually short period and within such a restricted area. 1 INTRODUCTION Advocates of mantle plumes have long considered continental flood basalt provinces to be one of the most obvious expressions of plume activity (Campbell and Griffiths, 1990; Richards et al., 1989).
    [Show full text]
  • Regional Dike Swarm Emplacement of Silicic Arc Magma in the Peninsular Ranges Batholith
    REGIONAL DIKE SWARM EMPLACEMENT OF SILICIC ARC MAGMA IN THE PENINSULAR RANGES BATHOLITH: THE SAN MARCOS DIKE SWARM (SMDS) OF NORTHERN BAJA CALIFORNIA Phil FARQUHARSON (presenter), David L. KIMBROUGH, and R. Gordon GASTIL, Department of Geological Sciences, San Diego State University Rancho San Marcos A densely intruded, northwest-striking, predominantly silicic regional dike The SMDS occurs entirely within the western province of the PRB, which is charac- swarm is exposed over an approximately 100 km-long segment in the terized by gabbro-tonalite-granodiorite plutons with primitive island arc geochemical west-central portion of the Cretaceous Peninsular Ranges batholith (PRB) affinities (DePaolo, 1981; Silver & Chappell, 1988; Todd et al., 1988, 1994), and in northern Baja California. Dike compositions range from basalt to rhyo- Rancho El Campito U/Pb zircon ages of 120-100 Ma. The extent of the swarm is shown schematically lite and are locally strongly bimodal. The swarm is intruded into two main N on the Gastil et al. (1975) 1:250 000 map of Baja California. units; 1) Triassic-Jurassic (?) turbidite flysch and 2) older, presumably pre- The swarm is intruded into two main units; 1) Triassic-Jurassic(?) turbidite flysch of 120 Ma batholithic rocks. Cross-cutting field relationships and a prelimi- the Rancho Vallecitos Formation (Reed, 1993) that is correlated to Julian Schist and nary U-Pb zircon age of 120±1 Ma clearly establish the swarm as an inte- Middle Jurassic Bedford Canyon Formation north of the border, and 2) older, pre- gral feature in the magmatic evolution of the PRB. Surprisingly, despite Agua Blanca Fault sumably pre-120 Ma batholithic rocks for which little data is currently available.
    [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]
  • Giant Radiating Mafic Dyke Swarm of the Emeishan Large Igneous Province: Identifying the Mantle Plume Centre
    doi: 10.1111/ter.12154 Giant radiating mafic dyke swarm of the Emeishan Large Igneous Province: Identifying the mantle plume centre Hongbo Li,1,2 Zhaochong Zhang,1 Richard Ernst,3,4 Linsu L€u,2 M. Santosh,1 Dongyang Zhang1 and Zhiguo Cheng1 1State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China; 2Geologi- cal Museum of China, Beijing 100034, China; 3Department of Earth Sciences, Carleton University, Ottawa, ON K1S 5B6, Canada; 4Ernst Geosciences, 43 Margrave Avenue, Ottawa, ON K1T 3Y2, Canada ABSTRACT In many continental large igneous provinces, giant radiating and recognized six dyke sub-swarms, forming an overall dyke swarms are typically interpreted to result from the arri- radiating dyke swarm and converging in the Yongren area, val of a mantle plume at the base of the lithosphere. Mafic Yunnan province. This location coincides with the maximum dyke swarms in the Emeishan large igneous province (ELIP) pre-eruptive domal uplift, and is close to the locations of have not received much attention prior to this study. We high-temperature picrites. Our study suggests that the Yon- show that the geochemical characteristics and geochronologi- gren area may represent the mantle plume centre during the cal data of the mafic dykes are broadly similar to those of peak of Emeishan magmatism. the spatially associated lavas, suggesting they were derived from a common parental magma. Based on the regional geo- Terra Nova, 27, 247–257, 2015 logical data and our field observations, we mapped the spa- tial distribution patterns of mafic dyke swarms in the ELIP, ridge by a continent (Gower and swarms and their distributions pro- Introduction Krogh, 2002), edge-driven enhanced vide an opportunity to further test Large igneous provinces (LIPs) are mantle convection (King and Ander- the plume model for the ELIP.
    [Show full text]
  • Instability of the Southern Canadian Shield During the Late Proterozoic 2 3 Kalin T
    1 Instability of the southern Canadian Shield during the late Proterozoic 2 3 Kalin T. McDannella,b*, Peter K. Zeitlera, and David A. Schneiderc 4 5 aDepartment of Earth and Environmental Sciences, Lehigh University, 1 W. Packer Ave. Bethlehem PA, 18015 USA 6 7 bGeological Survey of Canada, Natural Resources Canada, 3303 – 33 St NW Calgary AB, T2L 2A7 Canada 8 9 cDepartment of Earth & Environmental Sciences, University of Ottawa, 25 Templeton Ave., Ottawa ON, K1N 6N5 10 Canada 11 12 *corresponding author: [email protected]; [email protected] 13 14 ABSTRACT 15 Cratons are generally considered to comprise lithosphere that has remained tectonically 16 quiescent for billions of years. Direct evidence for stability is mainly founded in the Phanerozoic 17 sedimentary record and low-temperature thermochronology, but for extensive parts of Canada, 18 earlier stability has been inferred due to the lack of an extensive rock record in both time and 19 space. We used 40Ar/39Ar multi-diffusion domain (MDD) analysis of K-feldspar to constrain 20 cratonic thermal histories across an intermediate (~150-350°C) temperature range in an attempt 21 to link published high-temperature geochronology that resolves the timing of orogenesis and 22 metamorphism with lower-temperature data suited for upper-crustal burial and unroofing 23 histories. This work is focused on understanding the transition from Archean-Paleoproterozoic 24 crustal growth to later intervals of stability, and how uninterrupted that record is throughout 25 Earth’s Proterozoic “Middle Age.” Intermediate-temperature thermal histories of cratonic rocks 26 at well-constrained localities within the southern Canadian Shield of North America challenge 27 the stability worldview because our data indicate that these rocks were at elevated temperatures 28 in the Proterozoic.
    [Show full text]
  • U.S. DEPARTMENT of the INTERIOR U.S.GEOLOGICAL SURVEY ALK.BIB a Selected Bibliography of Alkaline Igneous Rocks and Related Mine
    U.S. DEPARTMENT OF THE INTERIOR U.S.GEOLOGICAL SURVEY ALK.BIB A selected bibliography of alkaline igneous rocks and related mineral deposits, with an emphasis on western North America compiled by Felix E. Mutschler, D. Chad Johnson, and Thomas C. Mooney Open-File Report 94-624 1994 This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. INTRODUCTION This bibliography contains 3,406 references on alkaline igneous rocks and related mineral deposits compiled in conjunction with ongoing studies of alkaline igneous rocks, metallogeny, and tectonics in western North America. Much of the literature on these topics is not readily recovered by searches of current bibliographies and computerized reference systems. We hope that by making this bibliography available, it will help other workers to access this occasionally hard to find literature. The bibliography is available in two formats: (1) paper hardcopy and (2) Apple Macintosh computer-readable 3.5 inch double density diskette. The computer-readable version of the bibliography is a 725 KB WORD (version 5.0) document. Individual literature citations are arranged alphabetically by author(s) and the order of items in each citation follows the standard U.S. Geological Survey format. Version 3.4 1 February 1994 BIBLIOGRAPHY Abbott, J. G., Gordey, S. P., and Tempelman-Kluit, D. J., 1986, Setting of stratiform, sediment- hosted lead-zinc deposits in Yukon and northeastern British Columbia, in Morin, J.
    [Show full text]
  • Flow Fabric Determination of Two Mesoproterozoic Midcontinent Rift Dike Swarms, Northeastern Minnesota
    FLOW FABRIC DETERMINATION OF TWO MESOPROTEROZOIC MIDCONTINENT RIFT DIKE SWARMS, NORTHEASTERN MINNESOTA A thesis submitted to the Kent State University Graduate College in partial fulfillment of the requirements for the degree of Master of Science by Elizabeth May Fein May, 2009 Thesis written by Elizabeth May Fein B.A., Oberlin College, 2003 M.S., Kent State University, 2009 Approved by ___________________________________, Advisor Daniel Holm ___________________________________, Chair, Department of Geology Daniel Holm ___________________________________, Dean, College of Arts and Sciences Timothy Moerland ii DEPARTMENT OF GEOLOGY THESIS APPROVAL FORM This thesis, entitled Flow fabric determination of two Mesoproterozoic midcontinent rift dike swarms, northeastern Minnesota has been submitted by Elizabeth Fein in partial fulfillment of the requirements for the Master of Science in Geology. The undersigned member’s of the student’s thesis committee have read this thesis and indicated their approval or disapproval of the same. Approval Date Disapproval Date _______________________________ _______________________________ Daniel Holm Daniel Holm _______________________________ _______________________________ Donald Palmer Donald Palmer _______________________________ _______________________________ David Schneider David Schneider iii Table of Contents List of Figures…………………………………………………………………………....v List of Tables…………………………………………………………………………….vi Acknowledgements…………………………………………………………………….vii Abstract ………………………………………………………………………………….1 1. Introduction
    [Show full text]
  • Ignimbrite Calderas, Regional Dike Swarms, and the Transition from Arc to Rift in the Southern Rocky Mountains
    Research Paper GEOSPHERE Magmato-tectonic links: Ignimbrite calderas, regional dike swarms, and the transition from arc to rift in the Southern Rocky Mountains 1, 2, GEOSPHERE, v. 15, no. 6 Peter W. Lipman * and Matthew J. Zimmerer * 1U.S. Geological Survey, Menlo Park, California 94025, USA 2New Mexico Bureau of Geology and Mineral Resources, Socorro, New Mexico 87801, USA https://doi.org/10.1130/GES02068.1 18 figures; 3 tables; 1 set of supplemental files ABSTRACT active for at least an additional 9 m.y. Platoro magmatism began to decline at ca. 26 Ma, concurrent with initial basaltic volcanism and regional extension CORRESPONDENCE: [email protected] Radial and linear dike swarms in the eroded roots of volcanoes and along along the Rio Grande rift, but no basalt is known to have erupted proximal rift zones are sensitive structural indicators of conduit and eruption geometry to Platoro caldera prior to ca. 20 Ma, just as silicic activity terminated at this CITATION: Lipman, P.W., and Zimmerer, M.J., 2019, Magmato-tectonic links: Ignimbrite calderas, regional that can record regional paleostress orientations. Compositionally diverse magmatic locus. The large numbers and lengths of the radial andesitic-dacitic dike swarms, and the transition from arc to rift in the dikes and larger intrusions that radiate westward from the polycyclic Platoro dikes, in comparison to the absence of similar features at other calderas of the Southern Rocky Mountains: Geosphere, v. 15, no. 6, caldera complex in the Southern Rocky Mountain volcanic field (southwest- San Juan volcanic locus, may reflect location of the Platoro system peripheral p.
    [Show full text]
  • Paleomagnetism Geochronology Geochemistry Proterozoic Mafic Dike
    ISBN 0-7794-8963-2 THESE TERMS GOVERN YOUR USE OF THIS DOCUMENT Your use of this Ontario Geological Survey document (the “Content”) is governed by the terms set out on this page (“Terms of Use”). By downloading this Content, you (the “User”) have accepted, and have agreed to be bound by, the Terms of Use. Content: This Content is offered by the Province of Ontario’s Ministry of Northern Development and Mines (MNDM) as a public service, on an “as-is” basis. Recommendations and statements of opinion expressed in the Content are those of the author or authors and are not to be construed as statement of government policy. You are solely responsible for your use of the Content. You should not rely on the Content for legal advice nor as authoritative in your particular circumstances. Users should verify the accuracy and applicability of any Content before acting on it. MNDM does not guarantee, or make any warranty express or implied, that the Content is current, accurate, complete or reliable. MNDM is not responsible for any damage however caused, which results, directly or indirectly, from your use of the Content. MNDM assumes no legal liability or responsibility for the Content whatsoever. Links to Other Web Sites: This Content may contain links, to Web sites that are not operated by MNDM. Linked Web sites may not be available in French. MNDM neither endorses nor assumes any responsibility for the safety, accuracy or availability of linked Web sites or the information contained on them. The linked Web sites, their operation and content are the responsibility of the person or entity for which they were created or maintained (the “Owner”).
    [Show full text]
  • Reshuffling the Columbia River Basalt Chronology—Picture Gorge Basalt, the Earliest- and Longest-Erupting Formation Emily B
    https://doi.org/10.1130/G47122.1 Manuscript received 17 April 2019 Revised manuscript received 3 December 2019 Manuscript accepted 5 December 2019 © 2020 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Reshuffling the Columbia River Basalt chronology—Picture Gorge Basalt, the earliest- and longest-erupting formation Emily B. Cahoon1*, Martin J. Streck1*, Anthony A.P. Koppers2 and Daniel P. Miggins2 1 Department of Geology, Portland State University, P.O. Box 751, Portland, Oregon 97207-0751, USA 2 College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331-5503, USA ABSTRACT divided into formations based on geographic The Columbia River Basalt Group (CRBG) is the world’s youngest continental flood basalt location of vents, geochemistry, and timing of province, presumably sourced from the deep-seated plume that currently resides underneath eruptions (Camp and Ross, 2004) and include Yellowstone National Park in the northwestern United States. The earliest-erupted basalts Steens, Imnaha, Grande Ronde, and Picture from this province aid in understanding and modeling plume impingement and the subsequent Gorge Basalts (e.g., Reidel et al., 2013). While evolution of basaltic volcanism. We explore the Picture Gorge Basalt (PGB) formation of the several models have been proposed for CRBG CRBG, and discuss the location and geochemical significance in a temporal context of early magmatism, many researchers support that the CRBG magmatism. We report new ARGUS-VI multicollector 40Ar/39Ar incremental heating flood basalts are sourced from the Yellowstone ages from known PGB localities and additional outcrops that we can geochemically classify mantle plume (e.g., Geist and Richards, 1993; as PGB.
    [Show full text]
  • Westward Migrating Ignimbrite Calderas and a Large Radiating Mafic Dike Swarm of Oligocene Age, Central Rio Grande Rift, New
    http://geoinfo.nmt.edu/staff/chamberlin/mrds/Chamberlin_2002_GSA_poster.pdf WESTWARD MIGRATING IGNIMBRITE CALDERAS AND A LARGE RADIATING MAFIC DIKE SWARM OF OLIGOCENE AGE, CENTRAL RIO GRANDE RIFT, NEW MEXICO: SURFACE EXPRESSION OF AN UPPER MANTLE DIAPIR? CHAMBERLIN, Richard M., CHAPIN, Charles E., and McINTOSH, William C., New Mexico Bureau of Geology and Mineral Resources, New Mexico Tech, Socorro NM 87801, [email protected] ABSTRACT: (Chamberlin et al., 2002) A cluster of five large overlapping ignimbrite calderas is moderately well exposed in strongly extended tilted fault-block mountain ranges of the central Rio Grande rift, southwest of Socorro NM. The Socorro-Magdalena caldera cluster (SMCC) is 85 km long and 20-25 km wide. It parallels the southeastern flank of the Colorado Plateau and the WSW-trending San Agustin arm of the rift. Precise 40Ar/ 39Ar ages of sanidines from the rhyolite ignimbrites demonstrate that the distended calderas become progressively younger to the west-southwest. Large volume ignimbrite eruptions occurred at 31.9, 28.7, 27.9, 27.4 and 24.3 Ma. A large satellitic caldera, formed at 28.4 Ma, is located 20 km south of the main overlapping trend. Moderately alkaline to sub-alkaline basaltic andesite and basalt dikes of Oligocene age (31-24 Ma, K-Ar, 40Ar/ 39Ar in progress) form a large semi-continuous radial array that is broadly focused on the SMCC. The Magdalena radial dike swarm (MRDS) fans through 220° of arc from Pie Town clockwise to Acoma, Chupadera, Bingham and Elephant Butte. The maximum radius of the MRDS is 125 km; subswarms of near parallel dikes are commonly 20-75 km long.
    [Show full text]
  • Mill Creek Diabase Dike Swarm, Eastern Arbuckles: a Glimpse of Cambrian Rifting in the Southern Oklahoma Aulacogen
    Cambrian (?) Mill Creek diabase dike swarm, eastern Arbuckles: A Glimpse of Cambrian rifting in the Southern Oklahoma Aulacogen Edward G. Lidiak1, Rodger E. Denison2, and Robert J. Stern3 1Department of Geology and Planetary Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15260. [email protected]. Corresponding author. 215141 Kingstree Drive, Dallas, Texas 75248. [email protected]. 3Department of Geosciences, The University of Texas at Dallas, Box 830688, Richardson, Texas 75083-0688. rjstern@ utdallas.edu. ABSTRACT INTRODUCTION A swarm of Cambrian (?) diabase dikes intrude The Southern Oklahoma Aulacogen (SOA) is a well- the 1390-1365 Ma granitoids of the eastern Arbuck- known transverse structure that trends west-northwest in le Mountains of Oklahoma. The dikes strike predom- the southern North American craton. Exposures within the inantly N60°W parallel to the rifted margin of the SOA reveal faults that record extension and which may Southern Oklahoma Aulacogen and are interpreted as be interpreted as related to its formation. Mesoproterozo- being related to Cambrian opening of that structure. ic basement underlies much of the region and ~1390 Ma The dikes, referred to here as the Mill Creek diabas- gneiss and granodiorite and ~1365 Ma granite are exposed es, are olivine-normative to quartz-normative tholeiitic in the eastern Arbuckle Mountains (Figures 1, 2). Diabase basalts. Their tholeiitic character is further indicated dikes are widespread throughout the core of the eastern Ar- T by high Fe2O3 (total Fe), moderate to high TiO2, low buckles. These dikes are referred to here as the Mill Creek P O , and low Nb/Y ratio. Mg numbers (Mg#) of 52-36 2 5 diabase dike swarm for excellent exposures in Mill Creek are indicative of derivative basaltic liquids which are Quarry (Figures 2, 3), which is here designated as the type consistent with the fine-grained, equigranular mineral locality.
    [Show full text]