DOCSLIB.ORG

Dynamics of Laboratory Diapir and Plume Models

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Dynamics of Laboratory Diapir and Plume Models VOL. 80, NO. 5 JOURNAL OF GEOPHYSICALRESEARCH FEBRUARY 10, 1975 Dynamics of Laboratory Diapir and Plume Models JOHN A. WHITEHEAD, JR. Departmentof Physical Oceanography, Woods Hole Oceanographic Instituiion Woods Hole, Massachusetts 02543 DOUGLAS S. LUTHER WoodsHole OceanographicInstitution, WoodsHole, Massachusetts02543 MassachusettsInstitute of Technology,Cambridge, Massachusetts 02139 The low Reynoldsnumber dynamicsof a thin layer of fluid boundedbelow by a flat horizontal boundaryand movingbuoyantly through a fluid of anotherviscosity and densityis observedby meansof modelexperiments and is describedtheoretically. Three distinct stages of growthwere observed. The first stageis describedby a linearizedRayleigh-Taylor instability, for whichprevious literature, present theory, and experimentsexhibit closeagreement. In this stage,disturbances of one specificwave numberare foundto grow mostrapidly. In the secondstage, distortion of the interfaceis largeenough to invalidate the linearizedanalysis. It is found experimentallythat the fluid movesupward as circularcolumns sur- rounded by relatively broad regions of descendingmaterial. A theory is advancedthat attributes an acceleratedgrowth to a structureof thiskind througha resonanttriad interaction.In the third stage,fully matured structuresare formed. If the upwellingmaterial has greaterviscosity than the surrounding material,the structureis a long verticalcolumn with graduallydecreasing diameter; if the upwelling material has lessviscosity than the surroundingmaterial, the structuredevelops a rim synclineand a pronouncedoverhang and eventuallyascends as a sphericalpocket of fluid fed by a pipe. Dynamicex- planationsfor thesefeatures are advanced,and somepossible implications for geologicaland geophysical processesare discussed. , A number of theories about the internal horizontal structure laboratories,the greatestnumber were aimed specifically at the of the mantleinvolve hot spots,mantle plumes, pipes, ascend- salt dome problem. ing sheetsof fluid under ridges,ascending blobs of fluid un- The investigation.s have utilized essentially two approaches. der island arc chains, and the like. More needs to be done to In the first the materials have been assumed to be Newtonian reconcilethe possibilityof suchstructures with what is known fluids. Analytical resultswere then obtainedfor the growth of flow in a deformable material. ratesof disturbancesin a fluid that is initiallyalmost perfectly Likewise, on a smaller scale,various types of diapirs are flat. This problem has been formulatedby, among others, believedto be formed from a densityin.version. Perhaps the Dane• [1964], solvedtheoretically by Selig [1965], solvedalso most highly studied example is salt domes, a considerable by Blotand Odb [1965] and Blot [1966],and solved numericaH, y amount being known about the structureof the domesand the for many layers by Ramberg [1968a, b]. In all cases the fluid propertiesof salt at elevatedtemperature. However, a equationscould be solvedanalytically as a linearizedproblem, variety of other diapiric structurespossibly have similar and recourseto a computerwas necessaryonly to avoid heavy dynamic origins, such as granitic batholiths, mud volcanoes, algebraicmanipulation. Recently, Berner et al. [1972] have mud lumps, and clay diapirs. Survey papers and a recent used finite differencemethods to study more matured struc- bibliographyare given by Braunsteinand O'Brien [1968]. turesthat cannotbe studiedanalytically. Emphasis in all the As an attemptto understandsuch structures, this paperis paperswas confinedto the rangeof parametersbelieved to be concernedwith the qualitativeshape and quantitative important in salt domes. dynamicsthat occur Whena fluid of a given large viscosity Experimental observationsof such a Newtonian fluid were movesbuoyantly up or downthrough a fluidof anotherlarge made by Nettleton [1934] and Dobrin [194'1]in which clear viscosityand density in a fieldof gravity.We reporton experi- photographsand detailedqualitative discussion revealed that mentsin which a thin horizontallayer of fluid is observedto suchdomes possess many features of realsalt domes, although go unstableand deform to a matrix of upwellingspouts that no theorieswere advanced to explainthe featuresof the struc- rise through a denserfluid of anotherviscosity. It is observed tures. that the structuralfeatures are stronglydependent on which Thesecond approach has been to studythe instability of fluid is more viscous.The dynamicsof sucha processis dis- materials whose rheology is felt to be somewhat more cussed.Experiments in which a fluid is fed from a continuous earthlike.Because of uncertaintyin the rheOlogicalequations, sourceare described,and it is again noted that the structural very little theoreticalor quantitativework is possible,and the featuresare stronglydependent on which fluid is more viscous. articlesare confinedto describingqualitative features of the in- Theoriesfor the formationof the structuresare advancedby trusions.An extensivework of this nature is by Parker and usingNewtonian fluid dynamics.Lastly, a comparisonwith McDowell [1955], which also contains an excellent some diapiric formations will be made. bibliographyof earlier work. A secondset of qualitativeex- Of the theoretical and laboratory studiesof diastrophic perimental studieshas been done by Ramberg [1963, 1967, movementsthat have beenpreviously modeled by theory or in 1970], who subjectedspecimens of pasty material to cen- trifugal forces.This approachhas the distinctadvantage that Copyright¸ 1975by the AmericanGeophysical Union. relativelycomplex and realisticgeometries are easilystudied, 705 706 WHITEHEAD AND LUTHER: DYNAMICS OF LABORATORYDIAPIR AND PLUME MODELS and specimenscan be stored and studied for a relatively long neck of fluid feedingthese pockets almost pinchedoff and left period of time. a tiny pipe of fluid trailing the main pocket of fluid, which The presentpaper differs from theseearlier works in that a descendedthrough the viscousfluid as almost perfectspheres. large range of viscosities is studied theoretically, and ex- This sequenceis shown in Figure 2. The picturesare inverted periments are conducted for the limiting cases. for clarity. It appears that the unstableflows proceededthrough three OBSERVATIONS OF UNSTABLE LAYERS distinctphysical flow stages,which will be discussedin the next This sectionwill describesome simple experimentsthat were three sections.Initially, the surfacewas nearly flat, while small performed in order to visualizethe problem. The experiments distortions to the interface grew by a Rayleigh-Taylor in- were suggestedby D. Griggs after a seminar given by D. stability. During this stage the assumptionof an almost flat Chappell at the Institute of Geophysicsand Planetary Physics, surface allows the equations to be linearized, and the University of California at Los Angeles, in 1969. A container equations that describe the growing flow have long been was almost completely filled with glycerin with a kinematic known. Such a study predicts the wavelength of maximum viscosityof 1400cm•'/s and a densityof 1.25 g/cm 3, to which a growth and the exponential time constant of growth. The small amount of immisciblesilicone oil with a viscosityof 60,- predicted rates, which will be describedin the next section, 000 cm•'/sand a densityof 0.92 g/cm 3 was added. This formed agree with various observationsin the literature as well as with a layer on top of the glycerinapproximately 5 mm thick. The observationsin the experiment described here. container was then carefully coveredso that no air was left in The second stage occurred when the interface became dis- it. After being left overnight, the container was inverted. In torted enoughto violate the linearizingassumptions of the first about 30 s the layer of viscousoil (which was on the bottom of stage. More complicated physical processesthat generally the tank) was observedto develop protrusionsthat buoyantly have not been identified began to occur at this stage.A few of pushedupward through' the glycerin as long buoyancy-driven the things that can happen are enhancedgrowth rate (super- columns,shown in the seriesof photographsin Figure 1. We exponential),nonlinear interactions among the variousgrow- found in particular, that if the containerwas left carefully ing modes,and a consequentialnarrowing of the classof the leveledfor a number of days so that the oil interfacewas very fastestgrowing modes. A work discussingthis stage will be flat before inversion,the columnsthat developedwere spaced briefly describedin the sectionon the initiation of spouts. quite uniformly throughout the tank and were very nearly In the third stagethe interfacewas greatly distorted,and the equal in size, volume, and growth rate. The wave number of intrusions had developeda matured structure. The linearized the columns, defined as 2;rH/L, where L is the distance solutions now are completely inadequate for describing the between columns and H is the depth of the fluid, was flow. The experimentsindicated that this final state is also a 2.5. strong function of the ratios of the viscositiesof the two fluids. The same experimentwas performed with another container The dynamics of these structures will be hypothesized and filled almost completelywith siliconeoil and with a thin layer tested against experiment. These will be describedin the sec- of glycerin on the bottom. Again, after the container was tion on rim synclines,overhang, and 'necking.' carefully leveled and left
Load more

Recommended publications
  • The Evolution of the Indian Ocean Mega-Undation
    Tectonophysics - Elsevier Publishing Company, Amsterdam Printed in The Netherlands THE EVOLUTION OF THE INDIAN OCEAN MEGA-UNDATION (CAUSING THE: INDIGO-FUGAL SPREADING OF GONDWANA k’I<AGMENTS) R.W. VAN BI<MILlL;LEN Geological Institute, State University, Utrecht (The Netherlands) (Received April 1, 1965) In the first section the geomechanical model of mega-undations is elaborated: (1) The lower mantle may have a Newtonian viscosity, but the upper mantle? which is largely in a crystalline state, shows an Andradean viscosity, with hot-creep phenomena and the formation of lamellae separated by zones or planes of high strain rate. (2) Reliable solutions of the mechanics in the fault planes of earthquake foci indicate that the spreading of the mega-undations is characterized in the outer 400 km by the farther advance of the higher structural levels with re- spect to the underlying ones: whereas the movements in the foci of deep earth- quakes underneath the Japan Sea and South America indicate a reverse pro- cess, the lower blocks moving faster towards the Pacific than the overlying ones. This is explained by the geomechanical model of the mega-undations. (3) The crest of the mega-undations shifts in the course of time, either gradually or by steps. The effects of such shifts are discussed and illustrated. (4) Four stages of evolution of mega-undations are distinguished: (a) young, (b) early mature or precocious, (c) late mature or ripe, and (d) fossil mega-undations. These stages are illustrated by type examples. In the section on the development of the Indian Ocean Mega-Undation this geomechanical model is tested by an analysis of the geotectonic evolution of the Indian Ocean and the surrounding shields.
    [Show full text]
  • The Geology of the Enosburg Area, Vermont
    THE GEOLOGY OF THE ENOSBURG AREA, VERMONT By JOlIN G. DENNIS VERMONT GEOLOGICAL SURVEY CHARLES G. DOLL, State Geologist Published by VERMONT DEVELOPMENT DEPARTMENT MONTPELIER, VERMONT BULLETIN No. 23 1964 TABLE OF CONTENTS PAGE ABSTRACT 7 INTRODUCTION ...................... 7 Location ........................ 7 Geologic Setting .................... 9 Previous Work ..................... 10 Method of Study .................... 10 Acknowledgments .................... 10 Physiography ...................... 11 STRATIGRAPHY ...................... 12 Introduction ...................... 12 Pinnacle Formation ................... 14 Name and Distribution ................ 14 Graywacke ...................... 14 Underhill Facics ................... 16 Tibbit Hill Volcanics ................. 16 Age......................... 19 Underhill Formation ................... 19 Name and Distribution ................ 19 Fairfield Pond Member ................ 20 White Brook Member ................. 21 West Sutton Slate ................... 22 Bonsecours Facies ................... 23 Greenstones ..................... 24 Stratigraphic Relations of the Greenstones ........ 25 Cheshire Formation ................... 26 Name and Distribution ................ 26 Lithology ...................... 26 Age......................... 27 Bridgeman Hill Formation ................ 28 Name and Distribution ................ 28 Dunham Dolomite .................. 28 Rice Hill Member ................... 29 Oak Hill Slate (Parker Slate) .............. 29 Rugg Brook Dolomite (Scottsmore
    [Show full text]
  • The Orocline Concept in Geotectonics
    The Orocline Concept in Geotectonics PART I By S. WARREN CAREY University of Tas'lnnnin (WITH 22 'f};XT FIGURES) A_BSTRACT The face of the globe shows muny areas where orogenic belts wheel in trend 0 through large angles, sometimes as much as 180 • Such a fOHn could have one of two origins. Either the orogenic zon(; had that shape from the beginning, or the bend represents an impressed strain (here defined as an orucline). Classieal geology has always made the first assumption, explicitly or implicitly, using the concept of cratons around which the orogens were moulded. However, logical ~cientific analysis demands that we should also examine the consequences of making the second assump­ tion. Twenty-five such cases occur on the face of the globe. In e-;m-y casp the major structures of the region not only agree with the assumption, but k'53e1' eomp:ressiona] and tensional structures fall where they would be prpdicted by the impressed strain theory. and quite unexpected solutions of other major tectonic: problems reRulL. Six of these oroclines are workod out in detail in this paper. Six ll101-e are presented more briefly. When all such oroclines, together with other identifiable strains, are reversed, there appears a Laurasia substantially identical with that deduced by Du Toit on wholly different grounds. INTRODUCTION Sir James Hall first made the induction that observed contortions in strata were actual deformations of heds originally flat, and therewith structural geology began. A century and a half has seen much progress, but most of it has been towards increasing our understanding of the internal anatomy of orogens.
    [Show full text]
  • The Deformation Cf Inhomogenous Materials and Consequent Geological Inflications
    THE DEFORMATION CF INHOMOGENOUS MATERIALS AND CONSEQUENT GEOLOGICAL INFLICATIONS by NICHOLAS CHARLES GAY A thesis submitted for the degree of Doctor of Philosophy at the University of London August, 1966. (±) ABSTRACT This thesis is a theoretical and experimental study of the deformation of inhomogenous materials by- simple and pure shear. The model adopted is that of a homogenous, Newtonian fluid matrix, in which are embedded rigid or deformable inclusions. The inclusions are ellipsoidal or elliptical in shape and the deformable ones are also assumed to be Newtonian bodies, but they may differ from the matrix in coefficient of viscosity. Published work on rock deformation is reviewed to show that rock does, in certain geological environments, approxi- mate closely to a Newtonian body. Equations are derived to describe the motion and changes in shape of the inclusions (or particles as they are called) during deformation of-the model. These equations are checked experimentally and, within the limits of the experimental error, the results agree satisfactorily with the theory. The behaviour of systems containing a large number of particles is discussed and the strains developed in the matrix around the inclusions are examined. The application of the theoretical concepts to certain problems in structural geology, such as the rotation of crys- tals, the development of preferred orientations and the deformation of conglomerates, is considered. Particular emphasis is laid on the use of the theoretical equations to determine the finite strain in rock. (ii) TABLE OF CONTENTS Page CHAPTER I INTRODUCTION A. GENERAL STATEMENT 1 B. ACKNOWLEDGEMENTS 5 C. LIST OF SYMBOLS 6 CHAPTER II VISCOSITY AND THE VISCOUS FLOW OF ROCKS' A.
    [Show full text]
  • K43: Field Development Report Technical: Storage
    February 2016 K43: Field Development Report Technical: Storage K43: Field Development Report IMPORTANT NOTICE The information provided further to UK CCS Commercialisation Programme (the Competition) set out herein (the Information) has been prepared by Capture Power Limited and its sub-contractors (the Consortium) solely for the Department of Energy and Climate Change in connection with the Competition. The Information does not amount to advice on CCS technology or any CCS engineering, commercial, financial, regulatory, legal or other solutions on which any reliance should be placed. Accordingly, no member of the Consortium makes (and the UK Government does not make) any representation, warranty or undertaking, express or implied, as to the accuracy, adequacy or completeness of any of the Information and no reliance may be placed on the Information. In so far as permitted by law, no member of the Consortium or any company in the same group as any member of the Consortium or their respective officers, employees or agents accepts (and the UK Government does not accept) any responsibility or liability of any kind, whether for negligence or any other reason, for any damage or loss arising from any use of or any reliance placed on the Information or any subsequent communication of the Information. Each person to whom the Information is made available must make their own independent assessment of the Information after making such investigation and taking professional technical, engineering, commercial, regulatory, financial, legal or other
    [Show full text]
  • Ice Petrofabrics, Tuktoyaktuk, Nwt
    ICE PETROFABRICS, TUKTOYAKTUK, N.W.T., CANADA by ALAN WILLIAM GELL B.Sc, Liverpool University, 1971 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS in the Department of Geography We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA August, 1973 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of GEOGRAPHY The University of British Columbia Vancouver 8, Canada Date 22<th September, 1973 ABSTRACT This thesis attempts to elucidate the origin and deformation of a folded sequence of ice and icy sediment in Tuktoyaktuk, N.W.T., Canada. Tuktoyaktuk lies between the maximum and late Wisconsin limits of glaciation. Bodies of underground ice in permafrost have character• istic Ice crystal sizes and shapes and inclusions dependent on the mode of ice growth and subsequent deformational or other history. The ice body which was studied lies beneath 2 m of fluvioglacial sands and 0.6 m of gravel. The ice-icy sediment foliation has been deformed into subhorizontal isoclinal folds, the major movement being from the SSW. Folds are classified into three styles.
    [Show full text]
  • Section Three: Geology and Geomorphology
    SECTION THREE: GEOLOGY AND GEOMORPHOLOGY 3- 0 3.1 GENERAL STATEMENT Geology is one of the principal factors that govern the geomorphic and hydrologic processes within a watershed. Geology includes rock type and sequence (lithology and stratigraphy); soils; tectonics (faults, seismicity, and folds), and mass wasting (landslides). The lithology and stratigraphy of rocks in the La Honda watershed strongly influence the channel form and the composition of the sediment in the streambed and banks. The lithology of the bedrock also influences the extent of soil development, shear strength, porosity, depth, vegetation productivity, and erodibility, as well as the depth and style of landslides, and the magnitude of ground acceleration during earthquakes. The rates of tectonic uplift affect the stream gradient and rate of downcutting, and extent of bank/bed erosion. Geologic ages are noted herein in millions of years (Ma) for older rocks or events, and in years before present (BP) for younger. A Geologic time scale is included in Appendix W. 3.2 PREVIOUS WORKS Numerous works have provided invaluable background to this study. Brabb et al. (2000) mapped the bedrock units in the La Honda area. Sarna-Wojcicki et al. (1991); Turner (1970); and Fox et al. (1985) determined the ages of the Mindego basalt and the Tahana Member of the Purisma Formation. Wagner and Nelson (1954) compiled the San Mateo Area Soil Survey based on the USDA-SCS soil classification system. Wieczorek (1982) discussed the weathering characteristics of bedrock in the area, and their effect on the style and extent of landsliding. Wieczorek (1984) mapped landslide parameters in the La Honda area.
    [Show full text]
  • Coupling Study Between Rheology and Electromagnetic Emission Of
    Available online at www.sciencedirect.com Procedia Engineering ProcediaProcedia Engineering Engineering 00 (20 2611 )(2011) 000–000 1571 – 1575 www.elsevier.com/locate/procedia First International Symposium on Mine Safety Science and Engineering Coupling study between Rheology And Electromagnetic Emission of Coal or Rock dynamic catastrophe Xue Erlong a, Zhang Xiaopin a, He Xueqiu b , Zhao feic, liu xinnac, Guo Jianhuac,LI Hailongca* aSafety Supervision Sector of Shenhua Group Limited Liability Company, Beijing, China bChina Academy of Safety Science & Technology, Beijing 100012, China cSchool of Resource and Safety Engineering, China University of Mining & Technology(Beijing), Beijing 100083, China Abstract This paper provides a theory of coal and rock rheological electromagnetic radiation coupling based on the generalized original model by using theoretical analysis, numerical simulation, field test and analysis of the coal rock material damage characteristics and strength statistics. On this basis, the software FLAC was used to simulate the roadway creep strain condition of # 2218 of Chengzhuang Coal Mine, and a research of electromagnetic radiation test on the tunnel was conducted. The practical testing results agree well with the analysis of theory. The results make contributions to the research on the usage of electromagnetic radiation and other disasters. © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of China Academy of Safety Science and Technology, China University of Mining and Technology(Beijing), McGill University and University of Wollongong Keyword: Coal petrography; creep deformation; simulation; electromagnetic radiation; tunnelling 1. Introduction Coal and rock dynamic disaster is one of the most critical natural disasters. Coal and rock rheology can explain the phenomenon of coal and rock dynamic disasters because it considers the factor of time.
    [Show full text]
  • The Morphology and Development of Folds A
    THE MORPHOLOGY AND DEVELOPMENT OF FOLDS A thesis submitted for the degree of Ph.D. of the University of London by Peter John Hudleston May 1969 2 ABSTRACT This thesis is concerned with the description, classification, analysis and interpretation of folds based on their morphologic properties. Existing methods of geometrical fold analysis are critically examined. Many are found to be impracticable. Two new analytical techniques are presented, one based on the use of dip isogons and the other based on harmonic analysis. A Visual method of rapid harmonic analysis is described that involves no measurements. Theories of fold development are discussed with particular reference to folds developed by buckling in isolated competent layers embedded in a less competent matrix. The geometric form of folds predicted by theory are examined. Emphasis is placed on the geometric forms taken up by buckle folds and by buckle folds modified by compression. A series of buckling experiments in single viscous layers embedded in a less viscous matrix at low viscosity contrasts are described. Progressive development of the shape of the experimentally formed folds is analysed and interpreted in terms of buckling theory. Detailed analyses of minor folds, in small parts of the Moine rocks in Scotland, the basement gneisses in the Swiss Alps and the Culm sediments on the Cornish coast are described. In the rocks of each region the geometric forms of the folds are shown to be different in each fold phase, and are also shown to be related to differences in layer composition. By analogy with the forms of folds predicted theoretically and observed experimentally the geometric forms of the natural folds are accounted for by processes of buckling and 'flattening'.
    [Show full text]
  • G14 Dynamic Theory of Plate Tectonics
    PLATE TECTONICS 417 g14 Dynamic theory of plate tectonics < rock, over time, has no strength; cooled plates actively sink > Throughout most of the Earth the geotherm is determined mainly by convection, except in the lithosphere where conduction is the principal means of heat transfer. But even here the oceanic part of the lithosphere is involved in convection through ocean-floor spreading and subduction. —Anthony R. Philpotts Principles of Igneous and Metamorphic Petrology, 1990.1 Rocks are rheids that under different conditions of rate of strain, temperature, and confining pressure, deform elastically, break brittlely, deform plastically, or creep viscously. Glacial-ice well exhibits rheid behavior (elastic upper part that crevasses, and plastic at higher confining pressure below). Simple dynamic modeling treats rock as a viscous compressible fluid. When other factors do not obtain, heating makes rock positively buoyant and cooling makes it negatively buoyant. Complications are metamorphism, metasomatism, and sometimes partial melting. For ten years beginning in 1923, Felix Andries Vening Meinesz (1887-1966), while uncomfortable for his giant height 2 in a submarine courtesy the Netherlands Navy, made area-gravity measurements of the East Indies seafloor.3 Between volcanic island-arcs and the ocean trench that parallels each on one side, he consistently found a profound negative-gravity anomaly. This, he conjectured in 1934 was due to mantle-sima convections that at convergences buckles, and holds down against isostasy, the less-dense sialic crust.4 Much effort, by many, was spent in refining this (wrong) picture of a crustal downfold for which H. H. Hess in 1938 5 coopted the term “tectogene” that E.
    [Show full text]
  • Lithostratigraphy of the Red Sea Region
    GeoArabia, Vol. 10, No. 3, 2005 Gulf PetroLink, Bahrain Lithostratigraphy of the Red Sea Region Geraint Wyn ap Gwilym Hughes and Robert S. Johnson ABSTRACT The onshore and offshore Saudi Arabian Red Sea region contains a series of lithostratigraphic units that have not previously been formally defined and described. Based on an intensive study of the succession, a lithostratigraphic scheme is proposed in a lexicon format that integrates biostratigraphic, sedimentological, seismic and field studies from the Midyan Peninsula in the north, to the Jizan Coastal Plain in the south. In view of the economic aspect of the Neogene succession and greater accessibility to Neogene subsurface samples, emphasis has been placed on a revision of the Neogene lithostratigraphy. Resting upon Proterozoic Basement, the sedimentary succession was deposited during the Cretaceous to Pleistocene times. The oldest pre-ri� Suqah Group nonconformably overlies the Proterozoic Basement and consists of Upper Cretaceous shales of the Adaffa Formation and Cretaceous to Palaeogene sandstones, shales and thin limestones of the Usfan Formation. A series of volcanics includes the early to middle Oligocene Matiyah Formation and the late Oligocene-early Miocene Jizan Group. The Neogene succession displays a great lithological diversity. The Tayran Group (Al Wajh, Musayr and Yanbu Formations) includes marginal marine siliciclastics of the Al Wajh Formation, and represents the earliest ri�-associated sediments deposited during the earliest Miocene. These are conformably overlain by lower Miocene shallow- marine carbonates of the Musayr Formation. In some of the central Red Sea onshore basins, thick lower Miocene submarine evaporites of the Yanbu Formation were deposited under locally restricted conditions and form the third formation of the Tayran Group.
    [Show full text]
  • STRUCTURAL GEOLOGY TECTONICS DIVISION Newsletter
    STRUCTURAL GEOLOGY & TECTONICS DIVISION SPRING NEWSLETTER STRUCTURAL GEOLOGY AND TECTONICS DIVISION Newsletter Volume 20, Number 1 March 2001 I wish you all a productive and successful year. First and foremost, I‘d like to thank the former Chair, Jane TWO OF THE WORLD'S Selverstone who, gave a lot of her time and energy to make OLDEST EARTH SCIENCE sure that things happened, and in a timely manner (thank you ORGANIZATIONS Jane from all of us!). Fortunately, Jane is still on the SG&T COLLABORATE IN board, and I am sure I will be drawing on her experience as this year unfolds. Charlie Onasch, Secretary/Treasurer and Division‘s long-term memory was happy to pass on his memo- "STUDY OF PLANET ry to Peter Vrolijk; thanks a lot, Charlie, for your great efforts EARTH AND BEYOND" with bookkeeping and words of wisdom, and Peter, welcome on board! Welcome also to Martha Withjack who has been The Geological Society of America elected second-vice Chair. CHAIRPERSON'S (established in 1888) and the MESSAGE Geological Society of London I would like to also recognize a number of people who just (established in 1807) will co-convene retired from committee duties. They have made great "Earth System Processes" June 24-28, contributions to the Division, after having served some of the most important goals of the 2001, in Edinburgh, Scotland, to take Division for several years: Kip Hodges (Career Contribution Award Committee), Steve an updated look at how the Earth Wojtal and Joanne Stock (Best Paper Award Committee), and Meghan Miller (Short works.
    [Show full text]