DOCSLIB.ORG

Neoproterozoic Glacial Origin of the Great Unconformity 2

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Neoproterozoic Glacial Origin of the Great Unconformity 2 Neoproterozoic glacial origin of the Great Unconformity Preprint ∗ C. Brenhin Keller1,2, Jon M. Husson3, Ross N. Mitchell4, William F. Bottke5, Thomas M. Gernon6, Patrick Boehnke7, Elizabeth A. Bell8, Nicholas L. Swanson-Hysell2, and Shanan E. Peters9 1Berkeley Geochronology Center 2Department of Earth and Planetary Science, University of California, Berkeley 3School of Earth and Ocean Sciences, University of Victoria 4Department of Applied Geology, Curtin University 5Southwest Research Institute, Boulder 6Ocean and Earth Science, University of Southampton 7Department of the Geophysical Sciences, The University of Chicago 8Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles 9Department of Geoscience, University of Wisconsin, Madison Abstract The Great Unconformity, a profound gap in Earth’s stratigraphic record often evident below the base of the Cambrian system, has remained among the most enigmatic field observations in Earth science for over a cen- tury. While long associated directly or indirectly with the occurrence of the earliest complex animal fossils, a conclusive explanation for the formation and global extent of the Great Unconformity has remained elusive. Here we show that the Great Unconformity is associated with a set of large global oxygen and hafnium isotope excursions in magmatic zircon that suggest a late Neoproterozoic crustal erosion and sediment subduction event of unprecedented scale. These excursions, the Great Unconformity, preservational irregularities in the terres- trial bolide impact record, and the first-order pattern of Phanerozoic sedimentation can together be explained by spatially heterogeneous Neoproterozoic glacial erosion totaling a global average of three to five vertical kilometers, along with the subsequent thermal and isostatic consequences of this erosion for global continental freeboard. Significance Walcott [2]. Observing a dearth of conformable sections span- ning the lower boundary of the Cambrian, Walcott proposed a It has long been observed that the sequence of sedimentary rocks “Lipalian” interval of continental exposure and erosion, which deposited in the past half-billion years often sharply overlies older igneous or metamorphic basement at an erosional surface known would have restricted any fossil precursors of the Cambrian as the Great Unconformity. We provide evidence that this uncon- fauna to the deep ocean basins. Subsequent investigation has formity may record rapid erosion during Neoproterozoic “snow- revealed a more complete Proterozoic, including fossiliferous ball Earth” glaciations. We show that the extent of Phanerozoic strata and conformable boundary sections; yet the observation sedimentation in shallow continental seas can be accurately repro- of a profound and extensive (if discontinuous) pre-Cambrian EarthArXiV Preprint 10.31223/osf.io/4k6pd duced by modeling the accommodation space produced by the unconformity remains [4, 5, Dataset S1]. Here we attempt to Proc. Natl. Acad. Sci. 10.1073/pnas.1804350116 proposed glacial erosion, underlining the importance of glacia- unite disparate evidence including the zircon Hf and O isotope tion as a means for lowering erosional base level. These results records, the terrestrial bolide impact record, and the record of provide new constraints on the sedimentary and geochemical en- continental sediment coverage in the context of this widespread vironment in which the first multicellular animals evolved and unconformity. diversified in the “Cambrian explosion” following the unconfor- mity. ADiscontinuous Global Unconformity arth’s sedimentary cover necessarily rests at depth upon ig- E neous or metamorphic crystalline basement. This contact The extent and magnitude of secular variation in preserved sed- need not be abrupt, since accumulating sediments gradually re- iment abundance across the Proterozoic-Phanerozoic boundary crystallize and metamorphose under increasing heat and pres- was first quantified by Ronov [4, Dataset S2], estimating pre- sure. Where observed, however, this transition often takes the served sediment volume flux over the past 1.6 Gyr from mapped form of a spatially abrupt and temporally correlated exposure sedimentary basin areas and stratigraphic thicknesses. The re- surface known as the Great Unconformity, a lacuna of both time sulting temporal pattern has been subsequently refined in Lau- and mass [1, 2, 3, 4, 5]. While often deeply buried, the Great rentia by the Macrostrat database [7, 8, 9] which (within North Unconformity is exposed in areas of relief such as the Grand America) provides higher-resolution temporal and spatial con- Canyon of the southwestern United States, where it was recog- straints. Together these records corroborate the presence of a nized by Powell [1], most dramatically at the sharp nonconfor- large global shift in preserved continental sediment abundance mity between the Paleoproterozoic Vishnu Schist and Cambrian near the base of the Cambrian (Fig. 1a; Figs. S1-S3). Tapeats Sandstone [6]. The ubiquity of this pattern – unde- The observed increase from roughly 0.2 km3/yr of preserved formed clastic sediments deposited directly and unconformably sedimentary rock in the Proterozoic to ∼1 km3/yr in the atop Precambrian basement – was subsequently recognized by Phanerozoic (Fig. 1a) might be attributed in principle to either *correspondence: [email protected] Preprint –Neoproterozoic glacial origin of the Great Unconformity 2 Ronov,1980 (global) Alternatively, a purely constructive interpretation would require /yr) 3 a roughly five-fold increase in sediment supply and/or continen- 3 Macrostrat (N. Am.) scaled: tal accommodation space, sustained throughout the Phanero- fluxN.Am.∗area land / areaN.Am. zoic. However, the observed Great Unconformity is profoundly Proterozoic Phanerozoic erosional in nature, characteristically juxtaposing fluvial sedi- ment with crystalline basement that was formed at great depth 2 in the crust. For instance, as shown in Fig. 1b, the Cambrian Ig- nacio Quartzite is deposited directly upon the Mesoproterozoic Eolus Granite (Fig. 1), a pluton with an emplacement depth of approximately 10-15 km (3-4.5 kbar) [12], requiring the ero- sion of over a third of the nominal thickness of the continental 1 crust over some subset of the ∼0.9 Gyr of geologic history miss- ing from this section. Posing an additional conundrum in either scenario, the a Phanerozoic-Proterozoic boundary is rather unexceptional from Preserved sediment volume (km 0 a mantle perspective, with no major variation in mantle po- 2500 2000 1500 1000 500 0 tential temperature or tectonic style evident in the continental Age (Ma) record [13, 14, 15, 16]. Consequently, it is difficult to conceive of a model where tectonic sediment supply and basin forma- b tion increase profoundly as a result of Neoproterozoic solid- Earth processes alone, or one in which dramatically increased tectonic exhumation drives unprecedented erosion. Moreover, while the Rodinian supercontinent cycle features a number of Cambrian marine sandstone noteworthy irregularities – including extroverted superconti- nent assembly [17] and an unusual ore deposit profile [18, 19] Great Unconformity – it is unclear how such irregularities could contribute to the formation of the Great Unconformity and associated global pre- Mesoproterozoic granite served sediment abundance variations in the absence of signifi- cant excursions in mantle potential temperature. In either a constructive or destructive endmember scenario, if global sediment supply from tectonic uplift is held constant 50 m near Phanerozoic levels, then the depressed Proterozoic sedi- ment volume in Fig. 1a suggests that on the order of 109 km3 Figure 1: The Great Unconformity. (a) Global preserved sedimen- of sediment are absent from the continental crust and deposited tary rock volume increases by more than a factor of five across the Phanerozoic–Proterozoic boundary in both the estimate of Ronov [4] instead in the deep ocean basins – either gradually, throughout and a global scaling of North American units from the Macrostrat the Proterozoic due to a diminished sediment storage capacity database by the area ratio of global land area to North American land of the continents in a constructive model, or rapidly during an area (a factor of 6.1) after Husson and Peters [8], excluding recent allu- interval of enhanced erosion near the Proterozoic-Phanerozoic vium. (b) The Cambrian Ignacio Quartzite overlies the Mesoprotero- boundary in a destructive model. Indeed, prior to the plate zoic (∼1.43 Ga) Eolus Granite at a sharp peneplanar nonconformity in tectonic revolution, the missing sediments from Walcott’s “Li- the Needle Mountains, Colorado. palian interval” were generally expected to reside in the ocean basins [2, 20]; their absence, along with the young age of the ocean crust, was considered a significant point of evidence in fa- vor of seafloor spreading and plate tectonics [20]. In a plate tec- tonic model, much sediment accumulated on the oceanic crust constructive (faster sediment accumulation in the Phanerozoic) is consumed by subduction – presently at a rate of about 1.65 or destructive (erosion of Proterozoic strata) processes. How- km3/yr [21]. Due to its low density and fusibility, however, ever, the abrupt nature of the observed transition presents dif- subducted sediment in the mantle wedge is often incorporated ficulties for either endmember model. The estimated volume into new arc magmas [21, 22]; consequently, a chemical or
Load more

Recommended publications
  • 2018-5 PGS Newsletter
    SEPTEMBER 2018 PGS NEWSLETTER VOL LXXI NO 1 September 12, 2018 Tectonics of the Social hour 6:00 PM Midcontinent: Looking Dinner 7:00 PM West (Geologically) Program 8:00 PM Dinner costs from Pittsburgh $30.00 per person $10.00 student member Across the Craton Reservations Email your name and number of attendees in your party to: pgsreservations @gmail.com You can also reserve and pay via PayPal at: https://www.pittsburgh geologicalsociety.org/ Dr. Stephen Marshak Location Foster’s Restaurant University of Illinois, Urbana-Champaign Foster Plaza Bldg. 10 Green Tree PA Deadline for reservations is noon on Monday, Sept. 10. Speaker Abstract Geologists have long held a fascination with and magnetotelluric arrays) that serve to mountain belts, because of their scenic beauty, characterize variations in crustal thickness, the and because they offer cross sections that intensity of faulting, and the relationship of provide access to rocks once deep in the crust. seismicity to structure; 2) structure-contour Datable igneous and metamorphic rocks in maps that help characterize the nature of mountain belts provide a basis for developing a displacement in fault-and-fold zones; 3) chronology of tectonism. The USA subsidence curves that constrain the timing of Midcontinent region doesn't display such basin subsidence; 4) a digital elevation model drama. These interior plains, which extend (DEM) of the Great Unconformity (the contact from Pittsburgh west to the Rockies, are part of between Precambrian and Paleozoic strata), North America's cratonic platform, a region in that gives a clearer image of structural relief which crust that formed over 1 billion years ago between basins and domes; 5) results from a lies buried beneath a veneer of nearly flat-lying thermochronologic study of the Great Phanerozoic sedimentary strata.
    [Show full text]
  • Grand Canyon
    U.S. Department of the Interior Geologic Investigations Series I–2688 14 Version 1.0 4 U.S. Geological Survey 167.5 1 BIG SPRINGS CORRELATION OF MAP UNITS LIST OF MAP UNITS 4 Pt Ph Pamphlet accompanies map .5 Ph SURFICIAL DEPOSITS Pk SURFICIAL DEPOSITS SUPAI MONOCLINE Pk Qr Holocene Qr Colorado River gravel deposits (Holocene) Qsb FAULT CRAZY JUG Pt Qtg Qa Qt Ql Pk Pt Ph MONOCLINE MONOCLINE 18 QUATERNARY Geologic Map of the Pleistocene Qtg Terrace gravel deposits (Holocene and Pleistocene) Pc Pk Pe 103.5 14 Qa Alluvial deposits (Holocene and Pleistocene) Pt Pc VOLCANIC ROCKS 45.5 SINYALA Qti Qi TAPEATS FAULT 7 Qhp Qsp Qt Travertine deposits (Holocene and Pleistocene) Grand Canyon ၧ DE MOTTE FAULT Pc Qtp M u Pt Pleistocene QUATERNARY Pc Qp Pe Qtb Qhb Qsb Ql Landslide deposits (Holocene and Pleistocene) Qsb 1 Qhp Ph 7 BIG SPRINGS FAULT ′ × ′ 2 VOLCANIC DEPOSITS Dtb Pk PALEOZOIC SEDIMENTARY ROCKS 30 60 Quadrangle, Mr Pc 61 Quaternary basalts (Pleistocene) Unconformity Qsp 49 Pk 6 MUAV FAULT Qhb Pt Lower Tuckup Canyon Basalt (Pleistocene) ၣm TRIASSIC 12 Triassic Qsb Ph Pk Mr Qti Intrusive dikes Coconino and Mohave Counties, Pe 4.5 7 Unconformity 2 3 Pc Qtp Pyroclastic deposits Mr 0.5 1.5 Mၧu EAST KAIBAB MONOCLINE Pk 24.5 Ph 1 222 Qtb Basalt flow Northwestern Arizona FISHTAIL FAULT 1.5 Pt Unconformity Dtb Pc Basalt of Hancock Knolls (Pleistocene) Pe Pe Mၧu Mr Pc Pk Pk Pk NOBLE Pt Qhp Qhb 1 Mၧu Pyroclastic deposits Qhp 5 Pe Pt FAULT Pc Ms 12 Pc 12 10.5 Lower Qhb Basalt flows 1 9 1 0.5 PERMIAN By George H.
    [Show full text]
  • 'Great Unconformity' on the North China Craton Using New Detrital
    1 Measuring the ‘Great Unconformity’ on the North China Craton using new 2 detrital zircon age data 3 4 Tianchen He1*, Ying Zhou1, Pieter Vermeesch1, Martin Rittner1, Lanyun Miao2, Maoyan Zhu2, Andrew 5 Carter3, Philip A. E. Pogge von Strandmann1,3 & Graham A. Shields1 6 7 1 Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, UK 8 2 State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and 9 Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China 10 3 Department of Earth and Planetary Sciences, Birkbeck College, University of London, Malet Street, 11 London WC1E 7HX, UK 12 *Corresponding author (e-mail: [email protected]) 13 14 Abstract: New detrital zircon ages confirm that Neoproterozoic strata of the southeastern North China 15 Craton (NCC) are mostly of early Tonian age, but that the Gouhou Formation, previously assigned to 16 the Tonian, is Cambrian in age. A discordant hiatus of >150-300 million years occurs across the NCC, 17 spanning most of the late Tonian, Cryogenian, Ediacaran and early Cambrian periods. This widespread 18 unconformable surface is akin to the ‘Great Unconformity’ seen elsewhere in the world, and highlights 19 a major shift in depositional style from largely erosional, marked by low rates of net deposition, during 20 the mid-late Neoproterozoic to high rates of transgressive deposition during the mid-late Cambrian. 21 Comparison between age spectra for southeastern NCC and northern India are consistent with a 22 provenance affinity linking the NCC and East Gondwana by ~510 Ma. 23 24 Supplementary material: The full sample list and U-Pb data are available at: 25 26 It has long been recognized that the traditional Precambrian–Cambrian (Ediacaran–Cambrian) 27 boundary interval is characterized worldwide by low rates of deposition and/or a major unconformity, 28 known as the ‘Great Unconformity’ (Brasier & Lindsay 2001, Peters & Gaines 2012).
    [Show full text]
  • The Meaning of the Great Unconformity and Sauk
    JOURNAL OF CREATION 28(1) 2014 || PERSPECTIVES distinctive stratigraphic surface in The meaning the rock record.”1 The Great Unconformity is also of the Great considered a unique feature within Unconformity the last 900 Ma of uniformitarian time.2 The Tonto Group in the Grand and Sauk Canyon is also recognized as covering about half of North America and is Megasequence called the Sauk Megasequence,1 the bottom of six megasequences that Michael J. Oard supposedly account for sedimen- tation over North America. The Sauk sequence is well defined lithologically he Great Unconformity, first on top of the upper crust and locally defined in the Grand Canyon T on Precambrian sedimentary and in 1869, separates the Cambrian metasedimentary rocks. However, Tapeats Sandstone from the underlying the other five sequences are based Precambrian rocks (the geological on many assumptions, such as fossil column and timescale are used for dating and not lithology, and are discussion purposes only). There commonly missing large sections in is some confusion in the Grand North America (see below). Canyon in that there is a second major unconformity between the Precambrian sedimentary rocks and The Great Unconformity in the igneous and metamorphic rocks Montana and Wyoming (figure 1). The uniformitarian origin of the Great Unconformity is supposed I have observed the Great Un- to be slow denudation over about a conformity at several locations in billion years that resulted in a nearly Wyoming and Montana. Whereas flat planation surface. Then after the Great Unconformity is near the this denudation, a shallow marine bottom of 1,200 m of flat strata in the transgression deposited the Tapeats Grand Canyon, it occurs at the tops of Sandstone, Bright Angel Shale, and some mountain ranges in Wyoming Muav Limestone in a fining upward and Montana.
    [Show full text]
  • Francis A. Macdonald
    Francis A. Macdonald Professor of Geology Department of Earth Sciences 2111 Webb Hall University of California at Santa Barbara Santa Barbara, CA 93106 (857) 998-9993 [email protected] Education Ph.D. Earth and Planetary Sciences, Harvard University, Cambridge, MA, 2009. B.S. Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 2001. Experience § Professor of Geology, University of California, Santa Barbara, CA, 2018-present. § Professor of Earth and Planetary Sciences, Harvard University, Cambridge, MA, 2017- 2018. § John L. Loeb Associate Professor of the Natural Sciences, Harvard University, Cambridge, MA, 2014-2017. § Associate Professor, Harvard University, Cambridge, MA, 2013-2014. § Assistant Professor, Harvard University, Cambridge, MA, 2009-2013. § Research Assistant, USGS Astrogeology, Flagstaff, AZ, 2004. § Lab Manager, Paleomagnetics Laboratory, Caltech, Pasadena, CA, 2002-2004. § Field Technician, Aguoron Paleoproterozoic Drilling Project, South Africa, 2002-2003. § Field Technician, Geophysical cruise ship, South Pacific, 2000-2001. § Research Assistant, Caltech, 1999-2000. Awards § Macelwene Medal (American Geophysical Union Early Career Award), 2019. § Reviewer Award, Geology, for consistently prompt, insightful, meticulous, and tactful reviews, 2015. § Donath Medal (Geological Society of America Young Scientist Award), 2014. § Star Family Prize for Excellence in Advising Award, Harvard College, 2012. § Ian Hamilton Golden Brunton Award, for excellence in field mapping, Caltech, 2001. Grants & Fellowships § NSF Frontier Research in Earth Systems: Do arc-continent collisions in the tropics set global climate state? 2019-present § NSF Sedimentary Geology and Paleontology: Collaborative Research: Did the formation of the Great Unconformity trigger oxygenation and the Cambrian explosion? 2018- present. § Inter-Continental Drilling Program (ICDP): Geological Research through Integrated Neoproterozoic Drilling, Ediacaran-Cambrian transition (GRIND-ECT) for scientific drilling in Brazil, Namibia, and South China.
    [Show full text]
  • G E O L O G Y This Interpretive Site Is Located Near a Significant Geologic Boundary
    G E O L O G Y This interpretive site is located near a significant geologic boundary. • You are standing approximately 450 feet west of a geologic contact called the “Great Unconformity” that By the beginning of the Paleozoic era, approximately 540 million years ago, the Precambrian‐age rocks had separates older Precambrian‐age rocks from younger Paleozoic‐age rocks. been eroded down to a nearly level surface. A seaway encroached from the west about 525 million years ago, • To the west (left) are metamorphic rocks of Precambrian age. As you drive toward Mount Rushmore, resulting in the accumulation of sedimentary rocks. The erosional surface between the Precambrian rocks and Precambrian‐age rocks include schist, amphibolite, quartzite, and granite. A large road cut in schist is 1.7 the younger, overlying Paleozoic rocks represents a break in time of approximately 1 billion years where rocks miles to the southwest. were not preserved. This break in time is called the “Great Unconformity.” It is marked below in the aerial • To the east are gently‐dipping younger sedimentary rocks of Paleozoic age. The road cut 0.2 miles to the east photo and is located on the hillside about 450 feet to the east‐northeast of this location. is in the Pahasapa Limestone. An outcrop of Pahasapa Limestone is also visible as a distant ridgeline N Stratobowl approximately 4 miles to the north. The Paleozoic and Tertiary sedimentary rocks deposited near this interpretive site include, from youngest to oldest: West Pahasapa Limestone Gravel deposit Minnelusa Formation
    [Show full text]
  • Diachronous Development of Great Unconformities Before Neoproterozoic Snowball Earth
    Diachronous development of Great Unconformities before Neoproterozoic Snowball Earth Rebecca M. Flowersa,1, Francis A. Macdonaldb, Christine S. Siddowayc, and Rachel Havraneka aDepartment of Geological Sciences, University of Colorado, Boulder, CO 80309; bEarth Science Department, University of California, Santa Barbara, CA 93106; and cDepartment of Geology, The Colorado College, Colorado Springs, CO 80903 Edited by Paul F. Hoffman, University of Victoria, Victoria, Canada, and approved March 6, 2020 (received for review July 30, 2019) The Great Unconformity marks a major gap in the continental precisely because the Great Unconformities mark a large gap in geological record, separating Precambrian basement from Phan- the rock record, the erosion history leading to their formation erozoic sedimentary rocks. However, the timing, magnitude, cannot be investigated directly by study of preserved units. spatial heterogeneity, and causes of the erosional event(s) and/ Past work leads to at least four general models for the timing or depositional hiatus that lead to its development are unknown. and magnitude of pre-Great Unconformity continental erosion, We present field relationships from the 1.07-Ga Pikes Peak batho- which are depicted in Fig. 1. Some have proposed major erosion lith in Colorado that constrain the position of Cryogenian and of the continents associated with assembly of the supercontinent Cambrian paleosurfaces below the Great Unconformity. Tavakaiv Rodinia and mantle upwelling below it prior to 850 Ma (Hy- sandstone injectites with an age of ≥676 ± 26 Ma cut Pikes Peak pothesis 1) or with the early diachronous breakup of Rodinia granite. Injection of quartzose sediment in bulbous bodies indi- between 850 and 717 Ma (Hypothesis 2) (10–17).
    [Show full text]
  • Chapter 5. Paleozoic Invertebrate Paleontology of Grand Canyon National Park
    Chapter 5. Paleozoic Invertebrate Paleontology of Grand Canyon National Park By Linda Sue Lassiter1, Justin S. Tweet2, Frederick A. Sundberg3, John R. Foster4, and P. J. Bergman5 1Northern Arizona University Department of Biological Sciences Flagstaff, Arizona 2National Park Service 9149 79th Street S. Cottage Grove, Minnesota 55016 3Museum of Northern Arizona Research Associate Flagstaff, Arizona 4Utah Field House of Natural History State Park Museum Vernal, Utah 5Northern Arizona University Flagstaff, Arizona Introduction As impressive as the Grand Canyon is to any observer from the rim, the river, or even from space, these cliffs and slopes are much more than an array of colors above the serpentine majesty of the Colorado River. The erosive forces of the Colorado River and feeder streams took millions of years to carve more than 290 million years of Paleozoic Era rocks. These exposures of Paleozoic Era sediments constitute 85% of the almost 5,000 km2 (1,903 mi2) of the Grand Canyon National Park (GRCA) and reveal important chronologic information on marine paleoecologies of the past. This expanse of both spatial and temporal coverage is unrivaled anywhere else on our planet. While many visitors stand on the rim and peer down into the abyss of the carved canyon depths, few realize that they are also staring at the history of life from almost 520 million years ago (Ma) where the Paleozoic rocks cover the great unconformity (Karlstrom et al. 2018) to 270 Ma at the top (Sorauf and Billingsley 1991). The Paleozoic rocks visible from the South Rim Visitors Center, are mostly from marine and some fluvial sediment deposits (Figure 5-1).
    [Show full text]
  • Cenozoic Stratigraphy and Paleogeography of the Grand Canyon, AZ Amanda D'el
    Pre-Cenozoic Stratigraphy and Paleogeography of the Grand Canyon, AZ Amanda D’Elia Abstract The Grand Canyon is a geologic wonder offering a unique glimpse into the early geologic history of the North American continent. The rock record exposed in the massive canyon walls reveals a complex history spanning more than a Billion years of Earth’s history. The earliest known rocks of the Southwestern United States are found in the Basement of the Grand Canyon and date Back to 1.84 Billion years old (Ga). The rocks of the Canyon can Be grouped into three distinct sets Based on their petrology and age (Figure 1). The oldest rocks are the Vishnu Basement rocks exposed at the Base of the canyon and in the granite gorges. These rocks provide a unique clue as to the early continental formation of North America in the early PrecamBrian. The next set is the Grand Canyon Supergroup, which is not well exposed throughout the canyon, But offers a glimpse into the early Beginnings of Before the CamBrian explosion. The final group is the Paleozoic strata that make up the Bulk of the Canyon walls. Exposure of this strata provides a detailed glimpse into North American environmental changes over nearly 300 million years (Ma) of geologic history. Together these rocks serve not only as an awe inspiring Beauty But a unique opportunity to glimpse into the past. Vishnu Basement Rocks The oldest rocks exposed within the Grand Canyon represent some of the earliest known rocks in the American southwest. John Figure 1. Stratigraphic column showing Wesley Paul referred to them as the “dreaded the three sets of rocks found in the Grand rock” Because they make up the walls of some Canyon, their thickness and approximate of the quickest and most difficult rapids to ages (Mathis and Bowman, 2006).
    [Show full text]
  • Neoproterozoic Glacial Origin of the Great Unconformity
    Neoproterozoic glacial origin of the Great Unconformity C. Brenhin Kellera,b,1, Jon M. Hussonc, Ross N. Mitchelld, William F. Bottkee, Thomas M. Gernonf, Patrick Boehnkeg,h, Elizabeth A. Belli, Nicholas L. Swanson-Hysellb, and Shanan E. Petersj aBerkeley Geochronology Center, Berkeley, CA 94709; bDepartment of Earth and Planetary Science, University of California, Berkeley, CA 94720; cSchool of Earth and Ocean Sciences, University of Victoria, Victoria, BC V8W 2Y2, Canada; dDepartment of Applied Geology, Curtin University, Perth, WA 6845, Australia; eSouthwest Research Institute, Boulder, CO 80302; fOcean and Earth Science, University of Southampton, Southampton SO17 1BJ, United Kingdom; gDepartment of the Geophysical Sciences, The University of Chicago, Chicago, IL 60637; hChicago Center for Cosmochemistry, Chicago, IL 60637; iDepartment of Earth, Planetary, and Space Sciences, University of California, Los Angeles, Los Angeles, CA 90095; and jDepartment of Geoscience, University of Wisconsin–Madison, Madison, WI 53706 Edited by Paul F. Hoffman, University of Victoria, Victoria, BC, Canada, and approved November 29, 2018 (received for review March 21, 2018) The Great Unconformity, a profound gap in Earth’s stratigraphic A Discontinuous Global Unconformity record often evident below the base of the Cambrian system, The extent and magnitude of secular variation in preserved sed- has remained among the most enigmatic field observations in iment abundance across the Proterozoic–Phanerozoic boundary Earth science for over a century. While long associated directly or were first quantified by Ronov et al. (ref. 4 and Dataset S2), esti- indirectly with the occurrence of the earliest complex animal fos- mating preserved sediment volume flux over the past 1.6 Gy from sils, a conclusive explanation for the formation and global extent mapped sedimentary basin areas and stratigraphic thicknesses.
    [Show full text]
  • The Shinumo Quadrangle, Grand Canyon District, Arizona
    DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY , ' ' ' *< ! !-" GEORGE OTIS SMITH, DIRECTOB BULLETIN 549 THE SHINUMO QUADRANGLE GRAND CANYON DISTRICT ARIZONA BY L. F. NOBLE WASHINGTON GOVERNMENT PRINTING OFFICE 1914 CONTENTS. Preface, by F. L. Kansome................................................. Introduction.............................................................. Location and geography................................................ Field work............................................................ Literature............................................................ Acknowledgments.........................................."............ Physiography of the Grand Canyon district................................. 15 Topography of the Shinumo quadrangle...................................... 2l Climate. .........=...................................................... 25 Vegetation............................................................... 27 Indian ruins.............................................................. 28 Geology.................................................................. 29 Age and character of the rocks.......................................... 29 . Series of rocks discriminated........................................... 31 Proterozoic rocks..................................................... I 32 Archean system.................................................... 32 Vishnu schist.................................................. 32 Name...................................................
    [Show full text]
  • Young Earth Flood Geology in the Grand Canyon John H
    Cedarville University DigitalCommons@Cedarville Science and Mathematics Faculty Publications Department of Science and Mathematics 3-2017 Young Earth Flood Geology in the Grand Canyon John H. Whitmore Cedarville University, [email protected] Follow this and additional works at: http://digitalcommons.cedarville.edu/ science_and_mathematics_publications Part of the Biblical Studies Commons, and the Geology Commons Recommended Citation Whitmore, John H., "Young Earth Flood Geology in the Grand Canyon" (2017). Science and Mathematics Faculty Publications. 355. http://digitalcommons.cedarville.edu/science_and_mathematics_publications/355 This Article is brought to you for free and open access by DigitalCommons@Cedarville, a service of the Centennial Library. It has been accepted for inclusion in Science and Mathematics Faculty Publications by an authorized administrator of DigitalCommons@Cedarville. For more information, please contact [email protected]. YOUNG EARTH FLOOD GEOLOGY IN THE GRAND CANYON by John Whitmore I grew up in a Christian home and was first attracted to encountered potential challenges between my faith and geology when my eighth-grade Earth Science class took a geology. In a paper I wrote for my freshman honors English weeklong field trip around Ohio collecting fossils. I went class on Darwin’s Origin of Species, I compromised. I tried on that trip again the next year and was hooked; I wanted to put evolution and millions of years within the Genesis to become a paleontologist. A year later, I traveled to the account. I wasn’t happy with this approach because I knew Grand Canyon for the first time. I’ll never forget looking Scripture didn’t clearly suggest such a view, but I didn’t know over the edge; I couldn’t believe something could be that what else to do.
    [Show full text]