DOCSLIB.ORG

Model by Keven

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Model by Keven High-quality constraints on the glacial isostatic adjustment process over North America: The ICE-7G_NA (VM7) model by Keven Roy A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Graduate Department of Physics University of Toronto © Copyright 2017 by Keven Roy Abstract High-quality constraints on the glacial isostatic adjustment process over North America: The ICE-7G_NA (VM7) model Keven Roy Doctor of Philosophy Graduate Department of Physics University of Toronto 2017 The Glacial Isostatic Adjustment (GIA) process describes the response of the Earth’s surface to variations in land ice cover. Models of the phenomenon, which is dominated by the influence of the Late Pleistocene cycle of glaciation and deglaciation, depend on two fundamental inputs: a history of ice-sheet loading and a model of the radial variation of mantle viscosity. Various geophysical observables enable us to test and refine these models. In this work, the impact of the GIA process on the rotational state of the planet will be analyzed, and new estimates of the long-term secular trend associated with the GIA process will be provided. It will be demonstrated that it has undertaken a significant change since the mid-1990s. Other important observables include the vast amount of geological inferences of past sea level change that exist for all the main coasts of the world. The U.S. Atlantic coast is a region of particular interest in this regard, due to the fact that data from the length of this coast provides a transect of the forebulge associated with the former Laurentide ice sheet. High-quality relative sea level histories from this region will be employed to generate a new model of the GIA process that includes for the first time data from the forebulge region in its optimization process (the ICE-6G_C (VM6) model). Then, the series of analyses is extended to include space-geodetic observations of present-day vertical uplift of the crust. A solution reconciling all available data from the continent, named ICE-7G_NA (VM7), is obtained through modest further modifications of both the viscosity structure of the model and the North American component of the surface mass loading history. It provides an excellent fit to the constraining data related to the GIA process, including observations of the time-dependent de-levelling of the Great Lakes region. Finally, to test the global exportability of the new model, its predictions of relative sea level change are tested against observations from the Western Mediterranean region. ii Pour mes parents, Chantal et Martin iii Acknowledgements First of all, I would like to thank my supervisor, Prof. W. R. Peltier, for his support and thoughtful mentoring throughout my project. Your guidance, advice and insight have helped me become a much better scientist and communicator. I am also grateful for the privilege you have given me to present my work and interact with other scientists at many conferences and workshops around the world during my time at the University of Toronto. Special thanks go to Prof. Dylan Jones and Prof. Qinya Liu for their insightful comments and support while being on my Ph.D. committee. Rosemarie Drummond and Guido Vettoretti also deserve credit for the invaluable help they have provided throughout the project. I would also like to thank Prof. Ben Horton and Dr. Donald Argus for sharing their expertise with me as I was learning about relative sea level data and space-geodetic observations. My external examiner, Prof. Geoffrey Blewitt, also deserves credit for his insightful comments on the final version of this thesis. I would also like to thank the very hard-working people of the Physics Department, including Ana Sousa, Pierre Savaria, Krystyna Biel and Teresa Baptista, who have helped me so many times. Special thanks also go to Dr. Michel Bourqui. Your introductory course on atmospheric and oceanic physics at McGill University and your availability to discuss research in Earth sciences have helped me discover a passion for geophysics. I would also like to thank the Natural Sciences and Engineering Research Council of Canada (NSERC), the Ontario Ministry of Training, Colleges and Universities (through the Ontario Graduate Scholarship program) and the Fonds Nature et Technologies (FRQNT) for the funding I received in support of my project. I would also like to thank the Centre for Global Change Science (CGCS) for the funding I received to attend beneficial and exciting conferences in Greenland and Australia. Moreover, I am indebted to the amazing people I have met at the University of Toronto, and in particular the present and former members of the Atmospheric Physics and Geophysics groups. I have been lucky to be surrounded by such inspiring people and make lifelong friends in the process. In particular, special thanks go to Niall, Zen, Phil, Joseph, Ryan, Federico, Andrew, Alain, Ellen, Maria and Oliver. Your support and friendship have helped me carry this project through. I would also like to thank Simon: I was quite fortunate to have my best friend around for most of my time at the University of Toronto. Going rock climbing and spending time with you were always fun, and your friendship means a lot to me. The long discussions I have had with you and Jen have also helped me in the tougher times. Cheers to both of you. Also, thanks to all my friends back in Québec and Montréal, who have helped me a great deal in staying balanced and motivated. Finally, some very important people deserve recognition for the infallible support they have provided iv me throughout my project. Betty, you deserve special credit for this project. Your love and constant support have helped me so much with finishing this project. J’aimerais finalement remercier ma famille, et particulièrement mes parents (Chantal et Martin), à qui cette thèse est dédiée, ainsi que mes soeurs Mélissa et Karen. Votre support inconditionnel m’a permis de mener ce projet à terme. Je vous en suis extrêmement reconnaissant. v Contents 1 Introduction 1 1.1 The orbital theory of the timing of the ice age cycle . 2 1.2 Ice age cycles in deep-sea sedimentary cores and ice cores . 7 1.3 Other geomorphological evidence and the Glacial Isotatic Adjustment (GIA) process . 11 1.4 Overview . 17 2 The Earth’s rotational state and its recent evolution 18 2.1 Fundamental dynamics . 19 2.1.1 A useful simplification: the axisymmetric case . 21 2.1.2 A special case: the free Eulerian wobble . 22 2.1.3 The influence of the GIA process on the moment of inertia of the planet . 23 2.2 Observations of rotational variability and reference frame considerations . 25 2.2.1 Celestial reference systems and frames . 25 2.2.2 Terrestrial reference systems and Earth Orientation Parameters (EOPs) . 27 2.2.3 Rotational variability measurement techniques and the latest ITRF iteration . 32 2.3 The evolution of secular trends in the planetary rotational state: Methodology and results 34 2.3.1 Sources of variability in length-of-day measurements . 35 2.3.2 Sources of variability in polar wander measurements . 37 2.3.3 Polar wander and LOD evolution: Data set and methodology employed . 37 2.3.4 Secular trend pivot point determination: results and analysis . 41 2.4 Perspectives and future work . 45 3 GIA constraints from the U.S. East coast: the ICE-6G_C (VM6) model 48 3.1 General approach and strategy . 50 3.2 Modelling the GIA process: Theoretical background . 51 vi 3.3 The ICE-NG models of ice sheet loading history . 55 3.4 Analysis of the performance of the ICE-6G_C ice loading history as a function of viscosity model ............................................... 57 3.4.1 Relative sea-level history reconstructions . 57 3.4.2 The Engelhart and Horton (2012) data set of U.S. East coast RSL evolution . 59 3.4.3 Analysis of the performance of the VM5a and VM5b viscosity structures . 59 3.4.4 The fit to the Fennoscandian spectrum . 64 3.5 An exploration of alternative viscosity structures . 66 3.5.1 Basic assumptions and methodology employed . 67 3.5.2 Error analysis and model performance . 68 3.5.3 Alternative viscosity models: V1 and V2 . 69 3.5.4 Case study I: Mantle viscosity variations in the upper mantle . 74 3.5.5 Case study II: Viscosity changes in the upper part of the lower mantle . 77 3.5.6 Case study III: Viscosity variations in the transition zone . 77 3.5.7 Case study IV: Viscosity contrast variations between the upper mantle and lower mantle . 80 3.5.8 Case study V: Lithosphere thickness variations . 82 3.5.9 Case study VI: Lower mantle viscosity variations and the Earth’s rotational state . 85 3.5.10 Other considerations and a summary of the insights gained through the sensitivity analyses . 86 3.6 A preferred viscosity structure: the VM6 profile . 88 3.6.1 The predictions for the U.S. East coast for ICE-6G_C (VM6) . 89 3.6.2 The fit to the Fennoscandian relaxation spectrum . 93 3.6.3 Testing the viscosity structure against data from the North American West coast . 94 3.7 Conclusion . 97 4 Full GIA constraints over N. America: the ICE-7G_NA (VM7) model 100 4.1 Geophysical observables related to the GIA process in North America and the performance of current models . 101 4.1.1 Constraints on former ice sheet extent and thickness . 102 4.1.2 The importance of RSL data from the North American region of forebulge collapse 102 4.1.3 Space-geodetic uplift measurements over North America . 104 vii 4.1.4 Time-dependent gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) satellites .
Load more

Recommended publications
  • WELLESLEY TRAILS Self-Guided Walk
    WELLESLEY TRAILS Self-Guided Walk The Wellesley Trails Committee’s guided walks scheduled for spring 2021 are canceled due to Covid-19 restrictions. But… we encourage you to take a self-guided walk in the woods without us! (Masked and socially distanced from others outside your group, of course) Geologic Features Look for geological features noted in many of our Self-Guided Trail Walks. Featured here is a large rock polished by the glacier at Devil’s Slide, an esker in the Town Forest (pictured), and a kettle hole and glacial erratic at Kelly Memorial Park. Devil’s Slide 0.15 miles, 15 minutes Location and Parking Park along the road at the Devil’s Slide trailhead across the road from 9 Greenwood Road. Directions From the Hills Post Office on Washington Street, turn onto Cliff Road and follow for 0.4 mile. Turn left onto Cushing Road and follow as it winds around for 0.15 mile. Turn left onto Greenwood Road, and immediately on your left is the trailhead in patch of woods. Walk Description Follow the path for about 100 yards to a large rock called the Devil’s Slide. Take the path to the left and climb around the back of the rock to get to the top of the slide. Children like to try out the slide, which is well worn with use, but only if it is dry and not wet or icy! Devil’s Slide is one of the oldest rocks in Wellesley, more than 600,000,000 years old and is a diorite intrusion into granite rock.
    [Show full text]
  • During the Last Ice Age As Ice Sheets Moved Southward Over Our Region, Glaciers Broke Off and Carried Pieces of the Underlying Bedrocks
    “Glacial Erratics and Fieldstones” Boulders and other rocks broken off and carried by ice sheets covering this region were left in place when the glaciers melted. Geologists call these “erratics.”. Early settlers called them “fieldstones” and used them to build their house walls. During the last Ice Age as ice sheets moved southward over our region, glaciers broke off and carried pieces of the underlying bedrocks. When the ice melted, the fragments were left scattered over the surface. Geologists call such transported rocks “glacial erratics,” because they are different from the native bedrock. Most of these were pebble- and boulder-sized, mixed into sands and clay. A few are more than 10 feet high, such as Haring Rock in the Tenafly Nature Center (Fig 1A) and Tripod Rock in Sussex County (Fig. 1b). Fig. 2 shows images of erratics of various sized in a state park. As the ice sheets moved, rocks underneath often scratched parallel grooves in the bedrocks. These are called “glacial striations” (Fig. 3). Until Englewood Township was formally organized in 1859, most of what is now our City consisted of small farms which stretched from Overpeck Creek uphill to the Hudson River. Like other early European settlers, the farmers needed to move the boulders and other glacial erratics to create plowable fields. Rocks were gathered to build stone walls typical of New England and other glaciated parts of the Northeast. (Fig. 4). Many of the stones collected from the fields (“fieldstones”) were trimmed to make the walls of homes and other buildings. Many of the remaining buildings from the Dutch/English colonial period and the early 19th Century here in Englewood and vicinity incorporated “fieldstones” in their walls.
    [Show full text]
  • The Early Wisconsinan History of the Laurentide Ice Sheet
    Document généré le 30 sept. 2021 19:59 Géographie physique et Quaternaire The Early Wisconsinan History of the Laurentide Ice Sheet L’évolution de la calotte glaciaire laurentidienne au Wisconsinien inférieur Geschichte der laurentischen Eisdecke im frühen glazialen Wisconsin Jean-Serge Vincent et Victor K. Prest La calotte glaciaire laurentidienne Résumé de l'article The Laurentide Ice Sheet L'identification, surtout en périphérie de l'inlandsis, de dépôts glaciaires que Volume 41, numéro 2, 1987 l'on croit postérieurs à la mise en place de sédiments non glaciaires ou de paléosols datant de l'interglaciaire sangamonien (phase 5) et antérieurs aux URI : https://id.erudit.org/iderudit/032679ar sédiments non glaciaires ou des sols mis en place au Wisconsinien moyen DOI : https://doi.org/10.7202/032679ar (phase 3) a amené de nombreux chercheurs à supposer que la calotte laurentidienne s'est d'abord développée au Sangamonien ou au Wisconsinien inférieur (phase 4). On passe en revue les différentes preuves associées au Aller au sommaire du numéro début de la formation de la calotte glaciaire wisconsinienne recueillies au Canada et au nord des États-Unis. En l'absence quasi généralisée de données géochronométriques sûres pour déterminer l'âge des dépôts glaciaires datant Éditeur(s) probablement du Sangamonien ou du Wisconsinien inférieur, on peut aussi bien supposer, pour une période donnée, que les glaces ont entièrement envahi Les Presses de l'Université de Montréal une région ou en étaient tout à fait absentes. En tenant pour acquis (?) que la calotte laurentidienne était en fait très étendue au Wisconsinien inférieur, on ISSN présente une carte montrant son étendue maximale et un tableau de 0705-7199 (imprimé) corrélation entre les unités glaciaires.
    [Show full text]
  • Glaciers and Glaciation
    M18_TARB6927_09_SE_C18.QXD 1/16/07 4:41 PM Page 482 M18_TARB6927_09_SE_C18.QXD 1/16/07 4:41 PM Page 483 Glaciers and Glaciation CHAPTER 18 A small boat nears the seaward margin of an Antarctic glacier. (Photo by Sergio Pitamitz/ CORBIS) 483 M18_TARB6927_09_SE_C18.QXD 1/16/07 4:41 PM Page 484 limate has a strong influence on the nature and intensity of Earth’s external processes. This fact is dramatically illustrated in this chapter because the C existence and extent of glaciers is largely controlled by Earth’s changing climate. Like the running water and groundwater that were the focus of the preceding two chap- ters, glaciers represent a significant erosional process. These moving masses of ice are re- sponsible for creating many unique landforms and are part of an important link in the rock cycle in which the products of weathering are transported and deposited as sediment. Today glaciers cover nearly 10 percent of Earth’s land surface; however, in the recent ge- ologic past, ice sheets were three times more extensive, covering vast areas with ice thou- sands of meters thick. Many regions still bear the mark of these glaciers (Figure 18.1). The basic character of such diverse places as the Alps, Cape Cod, and Yosemite Valley was fashioned by now vanished masses of glacial ice. Moreover, Long Island, the Great Lakes, and the fiords of Norway and Alaska all owe their existence to glaciers. Glaciers, of course, are not just a phenomenon of the geologic past. As you will see, they are still sculpting and depositing debris in many regions today.
    [Show full text]
  • Geology, Utah State University, Logan, Utah Topography and Is Composed of Highly Resistant, Fractured Gabbroic Rock
    Using inherited cosmogenic 36Cl to constrain glacial erosion rates of the Cordilleran ice sheet Jason P. Briner* Terry W. Swanson Department of Geological Sciences and Quaternary Research Center, University of Washington, Box 351310, Seattle, Washington 98195 ABSTRACT Cosmogenic 36Cl/Cl ratios measured from glacially eroded bedrock provide the first quan- titative constraints on the magnitude, rate, and spatial distribution of glacial erosion over the last glacial cycle. Of 23 36Cl/Cl ratios, 8 yield exposure ages that predate the well-constrained deglaciation of the Puget Lowland, Washington, and are inferred to result from 36Cl inherited from prior exposure during the last interglaciation where ice did not erode enough rock (~1.80–2.95 m) to reset 36Cl/Cl ratios to background levels. Surfaces possessing inherited 36Cl evidently were abraded only 0.25–1.06 m, corresponding to abrasion rates of 0.09–0.35 mm˙yr –1. These results indicate that in the absence of glacial quarrying, the Cordilleran ice sheet may have abraded as little as 1–2 m of bedrock near its equilibrium-line altitude over the last glacial cycle, equating to only tens of meters over the entire Quaternary. INTRODUCTION Where independent age control constrains the timing of surface expo- Although many researchers have discussed the glacial origin of stoss- sure following a given geomorphic event, such as a glaciation, 36Cl concen- and-lee topography (e.g., Jahns, 1943; Hallet, 1979), only Jahns (1943) at- trations that are higher than expected can be inferred to reflect 36Cl inherited tempted to determine quantitative estimates of glacial erosion by using ex- from prior exposure, presumably attributable to a lack of sufficient glacial ero- foliation patterns in granitic domes that were differentially eroded by the sion to remove the surface rock in which 36Cl accumulated prior to glaciation.
    [Show full text]
  • Lower Devonian Glacial Erratics from High Mountain, Northern New Jersey, USA: Discovery, Provenance, and Significance
    Lower Devonian glacial erratics from High Mountain, northern New Jersey, USA: Discovery, provenance, and significance Martin A. Becker1*and Alex Bartholomew2 1. Department of Environmental Science, William Paterson University, Wayne, New Jersey 07470, USA 2. Geology Department, SUNY, New Paltz, New York 12561, USA *Corresponding author <[email protected]> Date received 31 January 2013 ¶ Date accepted 22 November 2013 ABSTRACT Large, fossiliferous, arenaceous limestone glacial erratics are widespread on High Mountain, Passaic County, New Jersey. Analysis of the invertebrate fossils along with the distinct lithology indicates that these erratics belong to the Rickard Hill Facies of the Schoharie Formation (Lower Devonian, Tristates Group). Outcrops of the Rickard Hill Facies of the Schoharie Formation occur in a narrow belt within the Helderberg Mountains Region of New York due north of High Mountain. Reconstruction of the glacial history across the Helderberg Mountains Region and New Jersey Piedmont indicates that the Rickard Hill Erratics were transported tens of kilometers from their original source region during the late Wisconsinan glaciation. The Rickard Hill Erratics provide a unique opportunity to reconstruct an additional element of the complex surficial geology of the New Jersey Piedmont and High Mountain. Palynology of kettle ponds adjacent to High Mountain along with cosmogenic-nuclide exposure studies on glacial erratics from the late Wisconsinan terminal moraine and the regional lake varve record indicate that the final deposition of the Rickard Hill Erratics occurred within a few thousand years after 18 500 YBP. RÉSUMÉ Les grand blocs erratiques fossilifères apparaissent disperses dans les formations basaltiques de Preakness (Jurassique Inférieur) sur le mont High, dans le conte de Passaïc, dans l’État du New Jersey (NJ).
    [Show full text]
  • The Scenic Geology of Calgary – a Walk at Nose Hill – Dale Leckie 1
    The Scenic Geology of Calgary – A Walk at Nose Hill – Dale Leckie 1 The Scenic Geology of Calgary – A Walk at Nose Hill Nose Hill – so much geology to be seen Nose Hill Park is one of the best places to appreciate the geology of Calgary. The park overlooks the city and surrounding area, providing panoramic overviews in all directions. The Bow River valley is several kilometres wide and 200 metres deep, with a complicated geological history. The Rocky Mountains dominate the horizon to the west and the Plains stretch into the distance to the north, east and southeast. Directions Nose Hill Park and the associated hikes are best accessed from two locations. For the best overviews of the Bow River valley, the Rocky Mountains to the west, and to picture the glaciations and Glacial Lake Calgary, park at Edgemont Boulevard parking lot at the intersection of Shaganappi Trail and Edgemont Boulevard. A second location for an overview and to access the glacial erratic, park at the 64th Avenue parking lot, at the intersection of 14 Street NW and 64 Avenue. Use the figure below as a reference to the Scenic Geology of Calgary, as viewed from Nose Hill. The Scenic Geology of Calgary – A Walk at Nose Hill – Dale Leckie 2 • Meandering river sands and floodplain mudstones of the Paleocene Porcupine Hills Formation extend down about 600 metres below the city. These ancient rivers flowed into Alberta during the last mountain-building phase of the Rocky Mountains 62.5 to 58.5 million years ago. Sediment originated from the ancestral Rocky Mountains at the time.
    [Show full text]
  • Glaciers in Indiana
    Glaciers in Indiana Key Objectives State Parks Featured Students will understand how glacial ice and melting water ■ Pokagon State Park www.stateparks.IN.gov/2973.htm shaped and reshaped the Earth’s land surface by eroding rocks ■ Chain O’Lakes State Park www.stateparks.IN.gov/2987.htm and soil in some areas and depositing them in other areas in a process that extended over a long period, and will look at how the glaciers affected two Indiana State Parks. Activity: Standards: Benchmarks: Assessment Tasks: Key Concepts: Glaciers Describe how wind, water and glacial ice shape and reshape earth’s land surface by eroding Explain how a glacier is formed and Glaciers and nat- Time and SCI.4.2.2 2010 rock and soil in some areas and depositing moves along, and what natural features ural features of IN Motion them in other areas in a process that occurs it can leave behlnd. State Parks over a long period of time. Glacial vocabulary Pose and respond to specific questions to Understand the different glaciers that clarify or follow up on information, and make ELA.4.SL.2.4 moved across Indiana and the parts of comments that contribute to the discussion the state they reached. and link to the remarks of others. The World in Spatial Terms: Use latitude and Left Behind: longitude to identify physical and human Identify the location of two Indiana Glacial Parks SS.4.3.1 2007 features of Indiana. Example: Transportation State Parks using latitude and longitude in Indiana routes and major bodies of water (lakes and rivers) Engage effectively in a range of collabora- tive discussions (one-on-one, in groups, and Discuss and understand some the ELA.4.SL.2.1 teacher-led) on grade-appropriate topics and glacial features at Chain O’Lakes and texts, building on others’ ideas and expressing Pokagon.
    [Show full text]
  • The Glacial Geology of New York City and Vicinity, P
    Sanders, J. E., and Merguerian, Charles, 1994b, The glacial geology of New York City and vicinity, p. 93-200 in A. I. Benimoff, ed., The Geology of Staten Island, New York, Field guide and proceedings, The Geological Association of New Jersey, XI Annual Meeting, 296 p. John E. Sanders* and Charles Merguerian Department of Geology 114 Hofstra University Hempstead, NY 11549 *Office address: 145 Palisade St. Dobbs Ferry, NY 10522 ABSTRACT The fundamental question pertaining to the Pleistocene features of the New York City region is: "Did one glacier do it all? or was more than one glacier involved?" Prior to Fuller's (1914) monographic study of Long Island's glacial stratigraphy, the one-glacier viewpoint of T. C. Chamberlin and R. D. Salisbury predominated. In Fuller's classification scheme, he included products of 4 glacial advances. In 1936, MacClintock and Richards rejected two of Fuller's key age assignments, and made a great leap backward to the one-glacier interpretation. Subsequently, most geologists have accepted the MacClintock-Richards view and have ignored Fuller's work; during the past half century, the one-glacial concept has become a virtual stampede. What is more, most previous workers have classified Long Island's two terminal- moraine ridges as products of the latest Pleistocene glaciation (i. e., Woodfordian; we shall italicize Pleistocene time terms). Fuller's age assignment was Early Wisconsinan. A few exceptions to the one-glacier viewpoint have been published. In southern CT, Flint (1961) found two tills: an upper Hamden Till with flow indicators oriented NNE-SSW, and a lower Lake Chamberlain Till with flow indicators oriented NNW-SSE, the same two directions of "diluvial currents" shown by Percival (1842).
    [Show full text]
  • Virtual Tour of Maine's Surficial Geology
    Maine Surficial Geology Maine Geological Survey Virtual Tour of Maine’s Surficial Geology Maine Geological Survey, Department of Agriculture, Conservation & Forestry 1 Maine Surficial Geology Maine Geological Survey Introduction Maine's bedrock foundation is covered in many places by surficial earth materials such as sand, gravel, silt, and clay. These sediments were transported and deposited by glacial ice, water, and wind. Many of them formed during the "Ice Age", which occurred between about two million and ten thousand years ago. Others were laid down more recently in stream, shoreline, and wetland environments. The colors on the map represent various kinds of surficial sediments. We will see examples of the most common types in the following photos. Maine Geological Survey Maine Geological Survey, Department of Agriculture, Conservation & Forestry 2 Maine Surficial Geology Maine Geological Survey Sand and Gravel Maine Geological Survey Surficial geology is important to Maine's citizens for economic and environmental reasons. Most of the sand and gravel used in construction, concrete, and sanding roads in winter was originally deposited by streams from melting glacial ice. Gravel pits are often located in these glacial deposits. The deeper parts of many sand and gravel deposits contain large quantities of water and are classified as aquifers. Yields from some aquifers are so large that they can supply water to municipal wells and the bottled water industry. Maine Geological Survey, Department of Agriculture, Conservation & Forestry 3 Maine Surficial Geology Maine Geological Survey Planning Projects Maine Geological Survey Information about the type and thickness of surficial sediments is used in planning highway and building projects such as the new bridge across the Kennebec River in Augusta (shown here in an early stage of construction).
    [Show full text]
  • Till/A Symposium ' • TILL a Symposium
    ) Till/a Symposium ' • TILL a Symposium Edited by Richard P. Goldthwait Assisted by: Jane L. Forsyth David L. Gross Fred Pessl, Jr. OHIO STATE UNIVERSITY PRESS QE 097 T55 C~pyrl9ht © 1971 by the Ohio State University Press All Rights Reserved Library of Congress Catalogue Card Number 70-153422 Standard look Number 8142-0141-2 Manufactured In the United States of America Dedication To George W. White, at the time of his retirement, to honc,r his devotion, inspiration, and teaching on the subiect of till. Blank page vi. Contents PREFACE xi I ntroductfon 1 INTRODUCTION TO TILL, TODAY 3 by R. P. Goldthwait 1 , PROCEDURES OF TILL INVESTIGATIONS IN NORTH AMERICA: A GENERAL REVIEW 27 by A. Dreimanis Genesi~ 2 TILL GENESIS AND FABRIC IN SVALBARD, SPITSBERGEN 41 by G. S. Boulton j EVIDENCE FOR ABLATION AND BASAL TILL IN EAST-CENTRAL NEW HAMPSHIRE 73 by L. D. Drake J TILL FABRICS AND TILL STRATIGRAPHY IN WESTERN CONNECTICUT 92 by F. Pessl, Jr. ABLATION TILL IN NO~,THEASTERN VERMONT 106 by D. P. Stewart and P. MacClintock vii Thickness and Structure 3 INFLUENCE OF -IRREGULARITIES OF THE BED OF AN ICE SHEET ON DEPOSITION RATE OF TILL 117 by L. H. Nobles and J. Weertman GLACIOTECTONIC STRUCTURES IN DRIFT 127 by S. R. Moran THICKNESS OF WISCONSINAN TILL IN GRAND RIVER AND KILLBUCK LOBES, NORTHEASTERN OHIO AND NORTHWESTERN PENNSYLVANIA 149 by G. W. White Stratigraphic Correlations . 4 TILLS IN SOUTHERN SASKATCHEWAN, CANADA 167 by E. A. Christiansen TILL STRATIGRAPHY OF THE DANVILLE REGION, EAST-CENTRAL ILLINOIS 184 by W.
    [Show full text]
  • The Early Wisconsinan History of the Laurentide Ice Sheet
    Document generated on 10/05/2021 2:08 a.m. Géographie physique et Quaternaire The Early Wisconsinan History of the Laurentide Ice Sheet L’évolution de la calotte glaciaire laurentidienne au Wisconsinien inférieur Geschichte der laurentischen Eisdecke im frühen glazialen Wisconsin Jean-Serge Vincent and Victor K. Prest La calotte glaciaire laurentidienne Article abstract The Laurentide Ice Sheet The identification, particularly at the periphery of the ice sheet, of glacigenic Volume 41, Number 2, 1987 sediments thought to postdate nonglacial sediments or paleosols regarded as having been laid down sometime during the Sangamonian Interglaciation URI: https://id.erudit.org/iderudit/032679ar (stage 5) and thought to predate nonglacial sediments or soils reckoned to be of DOI: https://doi.org/10.7202/032679ar Middle Wisconsinan age (stage 3), has led numerous authors to propose that the Laurentide Ice Sheet initially grew during the Sangamonian and/or the Early Wisconsinan (stage 4). The evidence for the beginning of the See table of contents Wisconsinan ice sheet in various areas of Canada and the northern United States is briefly reviewed. The general absence of sound geochronometric frameworks for potential Sangamonian or Early Wisconsinan glacial deposits Publisher(s) has led to a situation where in most areas it can be argued, depending on one's interpretation, that ice completely inundated or was completely absent at that Les Presses de l'Université de Montréal time. On the premise (perhaps false) that Laurentide Ice was in fact extensive during the Early Wisconsinan, a map showing maximum possible ice extent, as ISSN put forward by some authors is presented and the glacigenic units possibly 0705-7199 (print) recording the ice advance are shown in a correlation chart.
    [Show full text]