DOCSLIB.ORG

Evidence from U-Pb Ages of Detrital Zircons

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Evidence from U-Pb Ages of Detrital Zircons Late Triassic Texas uplift preceding Jurassic opening of the Gulf of Mexico: Evidence from U-Pb ages of detrital zircons William R. Dickinson1*, George E. Gehrels1, and Robert J. Stern2 1Department of Geosciences, University of Arizona, Tucson, Arizona 85718, USA 2Department of Geosciences, University of Texas at Dallas, Box 830688, Richardson, Texas 75080, USA ABSTRACT dynamic subsidence behind the Cordilleran of North America by indicating the nature and magmatic arc, from headwaters in the Texas probable locations of changing sediment prov- We use U-Pb ages for 2655 individual prerift uplift to the sediment trap of the enances over Mesozoic time (Dickinson and detrital zircon grains in 30 samples of Upper backarc marine basin where the Auld Lang Gehrels, 2010). In this paper we discuss evi- Triassic (Carnian–Norian) sandstones of the Syne Group accumulated. dence from U-Pb ages of detrital zircons for southwestern USA (our data) and northern Sandstones from peripheries of the linked Late Triassic transport of voluminous sediment Mexico (other data) to infer regional Late Tri- fl uvial and marine depositional systems across southwest Laurentia from an uplift in assic provenance relations and tectonic fea- contain contrasting populations of detri- central Texas interpreted as a thermal precur- tures, which included a prerift uplift in Texas tal zircons derived either from the relict sor to Middle Jurassic opening of the Gulf of precursory to Jurassic opening of the Gulf of Amarillo-Wichita uplift, which fed abun- Mexico (Stern et al., 2008). Our focus is on pat- Mexico. Detrital zircons in sandstones from dant Cambrian zircons derived from an terns of Carnian and Norian sedimentation, with central paleorivers of the Chinle-Dockum uplifted aulacogen-fl oor igneous assemblage, minimal attention to Rhaetian (latest Triassic) fl uvial system on the High Plains (USA) and to selected basal units of the fl uvial system, deposits that typically formed in close associa- Colorado Plateau, and from the marine ter- or from the Cordilleran arc assemblage to tion with overlying eolian Lower Jurassic suc- minus of the fl uvial system along the eastern the south and west. The youngest Dockum cessions. The sedimentary record of detritus fl ank of the Auld Lang Syne backarc basin in sample from the Ouachita foreland on the from the Triassic uplift in Texas elucidates an the Great Basin, refl ect regional dispersal of High Plains contains abundant Devonian important facet of the evolution of the southern sediment from the Ouachita orogen and adja- zircons probably derived from the Ouachita margin of Laurentia. cent Mesoproterozoic basement exposed on metamorphic core zone now present only Detrital zircons in Chinle-Dockum fl uvial the northern fl ank of the rift uplift. The com- in the Texas subsurface. Sandstones along sandstones of the High Plains and Colorado Pla- posite grain population of Ouachita-derived the southern fl ank of the Chinle backarc teau were discussed in detail in Dickinson and sands displays dominant U-Pb age peaks basin on the southern Colorado Plateau Gehrels (2008). U-Pb analytical data, concordia at 1100–1050 Ma (Grenvillian) and subor- contain populations of detrital zircons simi- diagrams, age-bin histograms, and multiple age- dinate Neoproterozoic (630–550 Ma) and lar to those in sandstones of the Antimonio- probability plots for 19 Chinle-Dockum sand- Paleozoic (475–400 Ma) age peaks inferred Barranca forearc basin (Sonora) that was stones and two sandstones from the correlative to document recycling of sand grains from farther south beyond the arc axis. Sediment marine Auld Lang Syne Group, exposed farther the Ouachita system. The Ouachita detritus transported longitudinally from the Texas west in the Great Basin of Nevada, are included was supplemented by contributions from uplift to the El Alamar paleoriver and Potosí as Supplemental File 11 for this paper. The Auld Mesoproterozoic basement rocks of south- subsea fan of northeastern Mexico contains Lang Syne data supplant preliminary data in west Laurentia (compound 1805–1655 Ma populations of detrital zircons similar but Gehrels and Dickinson (1995) and Manuszak and unitary 1440 Ma age peaks) and from not identical to those in Chinle-Dockum et al. (2000) for the same two samples. We also Permian–Triassic arc assemblages of north- fl uvial strata of the High Plains shed trans- compare, with our Chinle-Dockum and Auld eastern Mexico (composite 285–215 Ma age versely from the rift uplift. peak). Master Chinle-Dockum paleodrain- ages extended east-southeast–west-northwest INTRODUCTION 1Supplemental File 1. Excel fi le of U-Pb (zircon) for 2000 km from Texas to Nevada, fl owing geochronologic analyses by laser-ablation multicol- along the axis of a backarc trough formed by U-Pb ages of detrital zircons from Meso- lector ICP mass spectrometry. If you are viewing the PDF of this paper or reading it offl ine, please visit zoic strata of the Colorado Plateau and adjoin- http://dx.doi.org/10.1130/GES00532.S1 or the full- ing areas have provided fresh insights into the text article on www.gsapubs.org to view Supplemen- paleogeographic and paleotectonic evolution tal File 1. *[email protected] Geosphere; October 2010; v. 6; no. 5; p. 641–662; doi: 10.1130/GES00532.1; 12 fi gures; 4 tables; 1 supplemental fi le. For permission to copy, contact [email protected] 641 © 2010 Geological Society of America Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/6/5/641/3342232/641.pdf by guest on 27 September 2021 Dickinson et al. Lang Syne data, detrital zircon populations from Age spectra of detrital zircon populations are tistics (Press et al., 1986) were used to test for the western fl ank of the Auld Lang Syne basin presented as age-distribution curves in the form congruence or incongruence of comparative age adjacent to the Cordilleran magmatic arc in Cal- of relative age-probability plots derived from spectra. The K-S test mathematically compares ifornia (Manuszak et al., 2000), the Antimonio- the probability density function (Ludwig 2003). two age spectra, taking analytical uncertainties Barranca forearc basin of northwestern Mexico For the age-distribution curves presented here, of each grain age into account, and determines (González-León et al., 2009), and the El Alamar N denotes the number of samples composited a probability (P) assessing the likelihood that paleoriver–Potosí subsea fan system of north- and n is the number of U-Pb ages from those differences between two age spectra could be eastern Mexico (Barboza-Gudiño et al., 2010). samples (see fi gure captions herein). The plots due to random choice of grains during analysis. incorporate each age and its analytical uncer- Where P > 0.05, there is <95% confi dence that DATA ACQUISITION AND tainty as a normal distribution. The individual two age populations were not selected randomly MANIPULATION normal distributions are then stacked into a from the same parent population (with P = 1.0 single compound curve. For visual comparison, indicating identical age spectra). We infer that Procedures for sample collection and prepa- the age-distribution curves are normalized to comparative age spectra yielding P > 0.05 from ration, and for U-Pb analyses of individual detri- equal areas beneath each curve. Visual inspec- the K-S test refl ect statistically indistinguishable tal zircon grains by laser ablation inductively tion of the age-distribution curves allows quali- zircon sources, but note that the K-S test can- coupled plasma mass spectrometry (LA-ICP- tative comparison of detrital zircon populations not establish that two detrital zircon populations MS) methodology (Gehrels et al., 2008), were or subpopulations. actually had the same sources. described in detail in Dickinson and Gehrels Age-bin histograms for detrital zircon ages The K-S test is stringent, however; for exam- (2008). In brief, zircon grains separated from are useful for evaluating individual samples ple, if a detrital zircon population is composed 22–24 kg samples were incorporated into epoxy (Supplemental File 1; see footnote 1) because of just two age subpopulations in proportions of mounts (typically 1000–2000 zircon grains they allow age peaks on age-probability curves 40:60 and 60:40, then P is <0.05. This P value each), and sanded down to a depth of 20 µm controlled only by isolated individual detrital seemingly implies distinctly different prov- to expose grain interiors. U-Pb ages were then zircon grains to be discounted relative to age enances, but geological insight might suggest determined for ~100 randomly selected grains peaks controlled by multiple grain ages. Age-bin that the two grain populations were derived in each sample mount, but only concordant and histograms are selective presentations of U-Pb from the same source rocks in somewhat differ- nearly concordant ages (Dickinson and Gehrels, analytical data, however, and are not statistically ent proportions. For assessing provenance rela- 2008) were retained for further consideration. valid because they are based exclusively on best tions, qualitative visual comparisons of detrital Discordant U-Pb ages for detrital zircons can- estimates of grain age without taking age uncer- zircon age spectra are useful in addition to quan- not be interpreted because each zircon grain tainties into account. No matter how age bins titative K-S tests because geological affi nities of potentially had a different history, and discordia are selected, some grain ages in each bin will two detrital zircon populations are not neces- chords cannot be defi ned for detrital zircons. have age uncertainties that overlap with at least sarily revealed properly by a strictly statistical An average of 91 grain ages per sample were one adjacent age bin. For the age-probability comparison of grain ages. retained for provenance analysis and included in curves of this paper composited from multiple Supplemental File 1 (see footnote 1).
Load more

Recommended publications
  • A Mesoproterozoic Iron Formation PNAS PLUS
    A Mesoproterozoic iron formation PNAS PLUS Donald E. Canfielda,b,1, Shuichang Zhanga, Huajian Wanga, Xiaomei Wanga, Wenzhi Zhaoa, Jin Sua, Christian J. Bjerrumc, Emma R. Haxenc, and Emma U. Hammarlundb,d aResearch Institute of Petroleum Exploration and Development, China National Petroleum Corporation, 100083 Beijing, China; bInstitute of Biology and Nordcee, University of Southern Denmark, 5230 Odense M, Denmark; cDepartment of Geosciences and Natural Resource Management, Section of Geology, University of Copenhagen, 1350 Copenhagen, Denmark; and dTranslational Cancer Research, Lund University, 223 63 Lund, Sweden Contributed by Donald E. Canfield, February 21, 2018 (sent for review November 27, 2017; reviewed by Andreas Kappler and Kurt O. Konhauser) We describe a 1,400 million-year old (Ma) iron formation (IF) from Understanding the genesis of the Fe minerals in IFs is one step the Xiamaling Formation of the North China Craton. We estimate toward understanding the relationship between IFs and the this IF to have contained at least 520 gigatons of authigenic Fe, chemical and biological environment in which they formed. For comparable in size to many IFs of the Paleoproterozoic Era (2,500– example, the high Fe oxide content of many IFs (e.g., refs. 32, 34, 1,600 Ma). Therefore, substantial IFs formed in the time window and 35) is commonly explained by a reaction between oxygen and between 1,800 and 800 Ma, where they are generally believed to Fe(II) in the upper marine water column, with Fe(II) sourced have been absent. The Xiamaling IF is of exceptionally low thermal from the ocean depths. The oxygen could have come from ex- maturity, allowing the preservation of organic biomarkers and an change equilibrium with oxygen in the atmosphere or from ele- unprecedented view of iron-cycle dynamics during IF emplace- vated oxygen concentrations from cyanobacteria at the water- ment.
    [Show full text]
  • Redalyc.Lost Terranes of Zealandia: Possible Development of Late
    Andean Geology ISSN: 0718-7092 [email protected] Servicio Nacional de Geología y Minería Chile Adams, Christopher J Lost Terranes of Zealandia: possible development of late Paleozoic and early Mesozoic sedimentary basins at the southwest Pacific margin of Gondwanaland, and their destination as terranes in southern South America Andean Geology, vol. 37, núm. 2, julio, 2010, pp. 442-454 Servicio Nacional de Geología y Minería Santiago, Chile Available in: http://www.redalyc.org/articulo.oa?id=173916371010 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Andean Ge%gy 37 (2): 442-454. July. 2010 Andean Geology formerly Revista Geológica de Chile www.scielo.cl/andgeol.htm Lost Terranes of Zealandia: possible development of late Paleozoic and early Mesozoic sedimentary basins at the southwest Pacific margin of Gondwana­ land, and their destination as terranes in southern South America Christopher J. Adams GNS Science, Private Bag 1930, Dunedin, New Zealand. [email protected] ABSTRACT. Latesl Precambrian to Ordovician metasedimentary suecessions and Cambrian-Ordovician and Devonian­ Carboniferous granitoids form tbe major par! oftbe basemenl of soutbem Zealandia and adjacenl sectors ofAntarctica and southeastAustralia. Uplift/cooling ages ofthese rocks, and local Devonian shallow-water caver sequences suggest tbal final consolidation oftbe basemenl occurred tbrough Late Paleozoic time. A necessary consequence oftlris process would have been contemporaneous erosion and tbe substantial developmenl of marine sedimentary basins al tbe Pacific margin of Zealandia.
    [Show full text]
  • MBMG 657 Maurice Mtn 24K.Ai
    MONTANA BUREAU OF MINES AND GEOLOGY MBMG Open-File Report 657 ; Plate 1 of 1 A Department of Montana Tech of The University of Montana Geologic Map of the Maurice Mountain 7.5' Quadrangle, 2015 INTRODUCTION YlcYlc Lawson Creek Formation (Mesoproterozoic)—Characterized by couplets (cm-scale) and couples (dm-scale) of fine- to medium-grained white to pink quartzite and red, purple, black, A collaborative Montana Bureau of Mines and Geology–Idaho Geological Survey (MBMG–IGS) and green argillite. Lenticular and flaser bedding are common and characteristic. Mud rip-up mapping project began in 2007 to resolve some long-standing controversies concerning the clasts are locally common, and some are as much as 15 cm in diameter. Thick intervals of 113° 07' 30" 5' 2' 30" R 12 W 113° 00' relationships between two immensely thick, dissimilar, Mesoproterozoic sedimentary sequences: the 45° 37' 30" 45° 37' 30" medium-grained, thick-bedded (m-scale) quartzite are commonly interbedded with the TKg TKg Lemhi Group and the Belt Supergroup (Ruppel, 1975; Winston and others, 1999; Evans and Green, argillite-rich intervals. The quartzite intervals appear similar to the upper part of the CORRELATION DIAGRAM 32 2003; O’Neill and others, 2007; Burmester and others, 2013). The Maurice Mountain 7.5′ quadrangle underlying Swauger Formation (unit Ysw), but quartz typically comprises a large percentage 20 Ybl occupies a key location for study of these Mesoproterozoic strata, as well as for examination of of the grains (up to 93 percent) in contrast to the feldspathic Swauger Formation. Except in Qaf 45 Tcg Ybl 40 Ybl Holocene important Proterozoic through Tertiary tectonic features.
    [Show full text]
  • A Template for an Improved Rock-Based Subdivision of the Pre-Cryogenian Timescale
    Downloaded from http://jgs.lyellcollection.org/ by guest on September 28, 2021 Perspective Journal of the Geological Society Published Online First https://doi.org/10.1144/jgs2020-222 A template for an improved rock-based subdivision of the pre-Cryogenian timescale Graham A. Shields1*, Robin A. Strachan2, Susannah M. Porter3, Galen P. Halverson4, Francis A. Macdonald3, Kenneth A. Plumb5, Carlos J. de Alvarenga6, Dhiraj M. Banerjee7, Andrey Bekker8, Wouter Bleeker9, Alexander Brasier10, Partha P. Chakraborty7, Alan S. Collins11, Kent Condie12, Kaushik Das13, David A. D. Evans14, Richard Ernst15,16, Anthony E. Fallick17, Hartwig Frimmel18, Reinhardt Fuck6, Paul F. Hoffman19,20, Balz S. Kamber21, Anton B. Kuznetsov22, Ross N. Mitchell23, Daniel G. Poiré24, Simon W. Poulton25, Robert Riding26, Mukund Sharma27, Craig Storey2, Eva Stueeken28, Rosalie Tostevin29, Elizabeth Turner30, Shuhai Xiao31, Shuanhong Zhang32, Ying Zhou1 and Maoyan Zhu33 1 Department of Earth Sciences, University College London, London, UK 2 School of the Environment, Geography and Geosciences, University of Portsmouth, Portsmouth, UK 3 Department of Earth Science, University of California at Santa Barbara, Santa Barbara, CA, USA 4 Department of Earth and Planetary Sciences, McGill University, Montreal, Canada 5 Geoscience Australia (retired), Canberra, Australia 6 Instituto de Geociências, Universidade de Brasília, Brasilia, Brazil 7 Department of Geology, University of Delhi, Delhi, India 8 Department of Earth and Planetary Sciences, University of California, Riverside,
    [Show full text]
  • Precambrian Basement and Late Paleoproterozoic to Mesoproterozoic Tectonic Evolution of the SW Yangtze Block, South China
    minerals Article Precambrian Basement and Late Paleoproterozoic to Mesoproterozoic Tectonic Evolution of the SW Yangtze Block, South China: Constraints from Zircon U–Pb Dating and Hf Isotopes Wei Liu 1,2,*, Xiaoyong Yang 1,*, Shengyuan Shu 1, Lei Liu 1 and Sihua Yuan 3 1 CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei 230026, China; [email protected] (S.S.); [email protected] (L.L.) 2 Chengdu Center, China Geological Survey, Chengdu 610081, China 3 Department of Earthquake Science, Institute of Disaster Prevention, Langfang 065201, China; [email protected] * Correspondence: [email protected] (W.L.); [email protected] (X.Y.) Received: 27 May 2018; Accepted: 30 July 2018; Published: 3 August 2018 Abstract: Zircon U–Pb dating and Hf isotopic analyses are performed on clastic rocks, sedimentary tuff of the Dongchuan Group (DCG), and a diabase, which is an intrusive body from the base of DCG in the SW Yangtze Block. The results provide new constraints on the Precambrian basement and the Late Paleoproterozoic to Mesoproterozoic tectonic evolution of the SW Yangtze Block, South China. DCG has been divided into four formations from the bottom to the top: Yinmin, Luoxue, Heishan, and Qinglongshan. The Yinmin Formation, which represents the oldest rock unit of DCG, was intruded by a diabase dyke. The oldest zircon age of the clastic rocks from the Yinmin Formation is 3654 Ma, with "Hf(t) of −3.1 and a two-stage modeled age of 4081 Ma. Another zircon exhibits an age of 2406 Ma, with "Hf(t) of −20.1 and a two-stage modeled age of 4152 Ma.
    [Show full text]
  • The World Turns Over: Hadean–Archean Crust–Mantle Evolution
    Lithos 189 (2014) 2–15 Contents lists available at ScienceDirect Lithos journal homepage: www.elsevier.com/locate/lithos Review paper The world turns over: Hadean–Archean crust–mantle evolution W.L. Griffin a,⁎, E.A. Belousova a,C.O'Neilla, Suzanne Y. O'Reilly a,V.Malkovetsa,b,N.J.Pearsona, S. Spetsius a,c,S.A.Wilded a ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS) and GEMOC, Dept. Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia b VS Sobolev Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090, Russia c Scientific Investigation Geology Enterprise, ALROSA Co Ltd, Mirny, Russia d ARC Centre of Excellence for Core to Crust Fluid Systems, Dept of Applied Geology, Curtin University, G.P.O. Box U1987, Perth 6845, WA, Australia article info abstract Article history: We integrate an updated worldwide compilation of U/Pb, Hf-isotope and trace-element data on zircon, and Re–Os Received 13 April 2013 model ages on sulfides and alloys in mantle-derived rocks and xenocrysts, to examine patterns of crustal evolution Accepted 19 August 2013 and crust–mantle interaction from 4.5 Ga to 2.4 Ga ago. The data suggest that during the period from 4.5 Ga to ca Available online 3 September 2013 3.4 Ga, Earth's crust was essentially stagnant and dominantly maficincomposition.Zirconcrystallizedmainly from intermediate melts, probably generated both by magmatic differentiation and by impact melting. This quies- Keywords: – Archean cent state was broken by pulses of juvenile magmatic activity at ca 4.2 Ga, 3.8 Ga and 3.3 3.4 Ga, which may Hadean represent mantle overturns or plume episodes.
    [Show full text]
  • Late Jurassic Dinosaurs on the Move, Gastroliths and Long-Distance Migration" (2019)
    Augustana College Augustana Digital Commons Geography: Student Scholarship & Creative Works Geography Winter 12-8-2019 Late Jurassic Dinosaurs on the Move, Gastroliths and Long- Distance Migration Josh Malone Augustana College, Rock Island Illinois Follow this and additional works at: https://digitalcommons.augustana.edu/geogstudent Part of the Geology Commons, Physical and Environmental Geography Commons, Sedimentology Commons, and the Spatial Science Commons Augustana Digital Commons Citation Malone, Josh. "Late Jurassic Dinosaurs on the Move, Gastroliths and Long-Distance Migration" (2019). Geography: Student Scholarship & Creative Works. https://digitalcommons.augustana.edu/geogstudent/8 This Student Paper is brought to you for free and open access by the Geography at Augustana Digital Commons. It has been accepted for inclusion in Geography: Student Scholarship & Creative Works by an authorized administrator of Augustana Digital Commons. For more information, please contact [email protected]. LATE JURASSIC DINOSAURS ON THE MOVE, GASTROLITHS AND LONG- DISTANCE MIGRATION a senior thesis written by Joshua Malone in partial fulfillment of the graduation requirements for the major in Geography Augustana College Rock Island, Illinois 61201 1 Table of Contents 1. Abstract ................................................................................................................................................ 4 2. Introduction ........................................................................................................................................
    [Show full text]
  • Proterozoic Ocean Chemistry and Evolution: a Bioinorganic Bridge? A
    S CIENCE’ S C OMPASS ● REVIEW REVIEW: GEOCHEMISTRY Proterozoic Ocean Chemistry and Evolution: A Bioinorganic Bridge? A. D. Anbar1* and A. H. Knoll2 contrast, weathering under a moderately oxidiz- Recent data imply that for much of the Proterozoic Eon (2500 to 543 million years ing mid-Proterozoic atmosphere would have 2– ago), Earth’s oceans were moderately oxic at the surface and sulfidic at depth. Under enhanced the delivery of SO4 to the anoxic these conditions, biologically important trace metals would have been scarce in most depths. Assuming biologically productive marine environments, potentially restricting the nitrogen cycle, affecting primary oceans, the result would have been higher H2S productivity, and limiting the ecological distribution of eukaryotic algae. Oceanic concentrations during this period than either redox conditions and their bioinorganic consequences may thus help to explain before or since (8). observed patterns of Proterozoic evolution. Is there any evidence for such a world? Canfield and his colleagues have developed an argument based on the S isotopic compo- n the present-day Earth, O2 is abun- es and forms insoluble Fe-oxyhydroxides, sition of biogenic sedimentary sulfides, 2– dant from the upper atmosphere to thus removing Fe and precluding BIF forma- which reflect SO4 availability and redox the bottoms of ocean basins. When tion. This reading of the stratigraphic record conditions at their time of formation (16–18). O 2– life began, however, O2 was at best a trace made sense because independent geochemi- When the availability of SO4 is strongly 2– Ͻϳ constituent of the surface environment. The cal evidence indicates that the partial pressure limited (SO4 concentration 1 mM, ϳ intervening history of ocean redox has been of atmospheric oxygen (PO2) rose substan- 4% of that in present-day seawater), H2S interpreted in terms of two long-lasting tially about 2400 to 2000 Ma (4–7).
    [Show full text]
  • The Archean Geology of Montana
    THE ARCHEAN GEOLOGY OF MONTANA David W. Mogk,1 Paul A. Mueller,2 and Darrell J. Henry3 1Department of Earth Sciences, Montana State University, Bozeman, Montana 2Department of Geological Sciences, University of Florida, Gainesville, Florida 3Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana ABSTRACT in a subduction tectonic setting. Jackson (2005) char- acterized cratons as areas of thick, stable continental The Archean rocks in the northern Wyoming crust that have experienced little deformation over Province of Montana provide fundamental evidence long (Ga) periods of time. In the Wyoming Province, related to the evolution of the early Earth. This exten- the process of cratonization included the establishment sive record provides insight into some of the major, of a thick tectosphere (subcontinental mantle litho- unanswered questions of Earth history and Earth-sys- sphere). The thick, stable crust–lithosphere system tem processes: Crustal genesis—when and how did permitted deposition of mature, passive-margin-type the continental crust separate from the mantle? Crustal sediments immediately prior to and during a period of evolution—to what extent are Earth materials cycled tectonic quiescence from 3.1 to 2.9 Ga. These compo- from mantle to crust and back again? Continental sitionally mature sediments, together with subordinate growth—how do continents grow, vertically through mafi c rocks that could have been basaltic fl ows, char- magmatic accretion of plutons and volcanic rocks, acterize this period. A second major magmatic event laterally through tectonic accretion of crustal blocks generated the Beartooth–Bighorn magmatic zone assembled at continental margins, or both? Structural at ~2.9–2.8 Ga.
    [Show full text]
  • Early Mesozoic Paleogeography and Tectonic Evolution of the Western
    Downloaded from gsabulletin.gsapubs.org on August 26, 2011 Early Mesozoic paleogeography and tectonic evolution of the western United States: Insights from detrital zircon U-Pb geochronology, Blue Mountains Province, northeastern Oregon Todd A. LaMaskin1,†, Jeffrey D. Vervoort2, Rebecca J. Dorsey1, and James E. Wright3 1Department of Geological Sciences, University of Oregon, 1272 University of Oregon, Eugene, Oregon 97403-1272, USA 2School of Earth and Environmental Sciences, Washington State University, Pullman, Washington 99164-2812, USA 3Department of Geology, University of Georgia, 308 Geography-Geology Building, 210 Field Street, Athens, Georgia 30602-2501, USA ABSTRACT the southwestern United States and modi- Vallier, 1995; Dorsey and LaMaskin, 2007, fied by input from cratonal, miogeoclinal, 2008). This proliferation of models reflects, This study assesses early Mesozoic prove- and Cordilleran-arc sources during Triassic in part, insufficient constraints on provenance nance linkages and paleogeographic-tectonic and Jurassic time. Jurassic sediments likely links to North America, the early Mesozoic models for the western United States based were derived from the Cordilleran arc and latitude of marginal arc-basin complexes, and on new petrographic and detrital zircon data an orogenic highland in Nevada that yielded the amount of subsequent post-Jurassic margin- from Triassic and Jurassic sandstones of the recycled sand from uplifted Triassic backarc parallel displacement. “Izee” and Olds Ferry terranes of the Blue basin deposits.
    [Show full text]
  • Megaripples from the Mesoproterozoic of the Kimberley Region, Northwestern Australia and Its Geological Implications
    Journal of Palaeogeography 2012, 1(1): 15−25 DOI: 10.3724/SP.J.1261.2012.00003 Lithofacies palaeogeography and sedimentology Megaripples from the Mesoproterozoic of the Kimberley region, northwestern Australia and its geological implications Lan Zhongwu1, 2, 3, , Zhong-Qiang Chen2, 4, * 1. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 2. School of Earth and Environment, The University of Western Australia, Australia 3. Key Lab of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 4. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Wuhan), Wuhan 430074, China Abstract Large ripples are described from the Mesoproterozoic Hilfordy Formation in the Kimberley region, northwestern Australia. Both ripple index (RI) and ripple symmetry in- dex (RSI) suggest the Kimberley ripples were likely generated by storm waves. Their wave height is up to 15−23 cm and wave length is up to 70−90 cm. These features, incorporated with other morphological characteristics such as symmetry, steepness, ripple spacing, and compositions, agree well with the megaripples previously reported from the intertidal-nearshore settings of modern seas and the geological past. The Mesoproterozoic ripples were likely gen- erated by the storm-induced flows. Literature survey of the global record of megaripples reveals that such structures have occurred through the geological past from the Archean to present day. They were particularly common in the Neoproterozoic and had the largest ripple length and ripple height among the modern and geological records. This is probably because extreme storms prevailed at that time.
    [Show full text]
  • Oxygenated Mesoproterozoic Lake Revealed Through Magnetic
    Oxygenated Mesoproterozoic lake revealed through magnetic mineralogy Sarah P. Slotznicka,1, Nicholas L. Swanson-Hysella, and Erik A. Sperlingb aDepartment of Earth and Planetary Science, University of California, Berkeley, CA 94720; and bDepartment of Geological Sciences, Stanford University, Stanford, CA 94305 Edited by Paul F. Hoffman, University of Victoria, Victoria, BC, Canada, and approved October 29, 2018 (received for review August 4, 2018) Terrestrial environments have been suggested as an oxic haven Formation has been further interpreted to indicate the pres- for eukaryotic life and diversification during portions of the Pro- ence of more than 50 different species (4). This record is terozoic Eon when the ocean was dominantly anoxic. However, argued to be more diverse than similar-aged marine assemblages, iron speciation and Fe/Al data from the ca. 1.1-billion-year-old which leads to the interpretation that lacustrine environments Nonesuch Formation, deposited in a large lake and bearing a with stable oxygenated waters may have been more hospitable diverse assemblage of early eukaryotes, are interpreted to indi- to eukaryotic evolution than marine ones (4). Early oxygena- cate persistently anoxic conditions. To shed light on these distinct tion of lacustrine environments during the Mesoproterozoic hypotheses, we analyzed two drill cores spanning the trans- has also been proposed based on large sulfur isotope frac- gression into the lake and its subsequent shallowing. While the tionations from sedimentary rocks of the Stoer and Torridon proportion of highly reactive to total iron (FeHR/FeT) is consis- groups that were interpreted to have resulted from oxidative tent through the sediments and typically in the range taken sulfur cycling (15).
    [Show full text]