Quaternary Glaciations - Extent and Chronology

A Closer Look

J. Ehlers, P.L. Gibbard, Philip D. Hughes, P.D. Hughes

• Publisher: Elsevier
• Year: 2011
• Print ISBN:
  9780444534477
• eBook ISBN:
  9780444535375
• Topic: Scienze fisiche
• Subtopic: Geologia e scienze della terra

The book presents an up-to-date, detailed overview of the Quaternary glaciations all over the world, not only with regard to stratigraphy but also with regard to major glacial landforms and the extent of the respective ice sheets. The locations of key sites are included. The information is presented in digital, uniformly prepared maps which can be used in a Geographical Information System (GIS) such as ArcView or ArcGIS. The accompanying text supplies the information on how the data were obtained (geomorphology, geological mapping, air photograph evaluation, satellite imagery), how the features were dated (14C, TL, relative stratigraphy) and how reliable they are supposed to be. All references to the underlying basic publications are included. Where controversial interpretations are possible e.g. in Siberia or Tibet, this is pointed out. As a result, the information on Quaternary glaciations worldwide will be much improved and supplied in a uniform digital format.The information on the glacial limits is compiled in digital form by the coordinators of the project, and is available for download at: http://booksite.elsevier.com/9780444534477/ - Completely updated detailed coverage of worldwide Quaternary glaciations - Information in digital, uniformly prepared maps which can be used in a GIS such as ArcView or ArcGis - Step-by-step guideline how to open and use ArcGis files - Possibility to convert the shapefiles into GoogleEarth kmz-files - Availability of chronological controls

Introduction

Jürgen Ehlers¹* (email: [email protected]), Philip L. Gibbard² (email: [email protected]) and Philip D. Hughes³ (email: [email protected])

¹Geologisches Landesamt, Billstraße 84, D-20539 Hamburg, Germany

²Cambridge Quaternary, Department of Geography, University of Cambridge, Downing Place, Cambridge CB2 3EN, United Kingdom

³Quaternary Environments and Geoarchaeology Research Group, Department of Geography, School of Environment and Development, Arthur Lewis Building, The University of Manchester, Manchester M13 9PL, United Kingdom

^*Correspondence and requests for materials should be addressed to J. Ehlers.

Abstract

The asynchroneity of glacial maxima across the world during the last glacial cycle emphasises the need to re-evaluate the concept of a ‘Last Glacial Maximum’ representing a single global event when glaciers reached their maximum extent. Glaciations were considerably more complex in terms of the timing and extent than previously appreciated

Keywords: VMAP1; SRTM; Open StreetMap; ASTER terrain model; Last Glacial Maximum

1.1. Introduction

This new edition of Quaternary Glaciations—Extent and Chronology gathers together the evidence of glaciation from around the world in 77 chapters. The book combines all regions of the world into one volume and provides a closer look at the extents, timing, and wider significance of Quaternary glaciations. The main advances reported in this book include better understanding of the timings of glaciations—especially through the application of cosmogenic nuclide analyses—and better understanding of the detailed extent and subdivision of different glaciations. These advances are supported by new digital maps, the detailed production of which is presented below. In addition, this introduction summarises the compilation's key findings and raises some of the main common themes that are apparent from the glacial records around the world. However, given the large number of excellent contributions, it is not possible to mention each chapter and it is recommended that readers explore the volume and discover for themselves the new findings from specific areas.

The editors would have liked to produce the volume in full colour. Unfortunately, that was not possible. However, this volume contains far more colour illustrations than the previous edition.

1.2. The Digital Maps

For more than 150 years, geologists have mapped the traces of Quaternary glaciations. One main purpose of creating the maps is to obtain reproducible results. Where scale and coordinates are given, the results are considered to be reproducible. But different scales and different projections hinder comparison. In High Asia, for instance, the printed maps do not show much more than that there are very different views on that topic. However, where exactly the ice margins are supposed to be located is very difficult to reconstruct. True comparison is only possible where digital maps in a digital Geographic Information System (GIS) are employed.

At the INQUA Congress in Berlin 1995, a new investigation of the glacial limits seemed desirable. The last such attempt, coordinated by Denton and Hughes (‘The Last Great Ice Sheets’, 1981), was by that time almost 25 years old and much was out of date. During the congress, a working group on the Extent and Chronology of Quaternary Glaciations of the Commission on Glaciation was initiated. The first question that work group had to solve was to find a suitable base map. A scale of 1:1,000,000 seemed desirable. However, the printed World Map of that scale was compiled over a period of about 70 years (since 1913) and it was still incomplete. Fortunately, a digital map had become available just in time that seemed ideal for the purpose: the Digital Chart of the World (DCW).

1.2.1. The Digital Chart of the World

The DCW consists of 2094 tiles, each of which (except near the South Pole) is 5 × 5° in size. To identify the tiles, the globe had been subdivided into 12 latitudinal and 24 longitudinal stripes, named using the letters of the alphabet, starting from the south and the west. The resulting 15 × 15° areas were again subdivided into nine tiles, which were numbered. A tile named NK11 (Paris) would be between 0° and 15°E (letter N), between 45° and 60°N (letter K) and the southeasternmost tile of that section (number 11)—thus located between 0° and 5°E and 45° and 50°N (Fig. 1.1). Six hundred of these original tiles are required to cover the formerly glaciated parts of the globe. Gaps in the hypsometry layer of the DCW could be filled with information from the GTOPO30 terrain model (see below).

Figure 1.1 Naming scheme of the digital maps.

In 1999, when the coordinators of the project started to work with the DCW, the correctness of their base map was not in doubt. However, as soon as better digital maps got available, the shortcomings of the DCW became obvious. The horizontal accuracy was insufficient. The position of each individual line, point or polygon was found to be several hundred metres out of place, in extreme cases even more. At 1:1,000,000, where 1km is equal to 1mm, that is still acceptable. However, as soon as comparison with higher resolution topographic data is attempted, the error can no longer be tolerated. The present maps aim to be accurate at a scale of 1:250,000 (1km equal to 4mm). Freely available satellite-based topographic data have a much higher accuracy and allow mapping down to 1:75,000.

1.2.2. The GTOPO30 Terrain Model

The GTOPO30 terrain model had been compiled by the United States Geological Survey (USGS) in 1998 and can today be downloaded without charge from various websites. It has a horizontal resolution of ca. 1km and is very suitable for overview maps, although at a scale of 1:1,000,000, it is at its limit. GTOPO30 was compiled from published sources. For most parts of the world, it is based on the Digital Terrain Elevation Data (DTED). Whilst the terrain model seems flawless in global overviews, at a higher resolution artefacts appear. One of them consists of diagonal stripes, especially in Africa and the Middle East. More disturbing is the dissolution of the image into 1 × 1° blocks. This is strongest in areas of low relief, such as the lowlands of West Siberia. When used as an image, this effect can be masked by using the right altitudinal intervals. When trying to reconstruct the extent of the former ice-dammed lakes, however, the effects of this fault are clearly visible.

1.2.3. The Vector Map Level 1 (VMAP1)

Today, the DCW has been re-named Vector Map Level 0 (VMAP0), but the contents have not been updated. The VMAP1 is far more accurate, it is intended for a scale of 1:250,000. Unfortunately, only part of this comprehensive map system, that like the DCW covers the whole globe, has been made available to the public. The published parts include most of the United States, about half of the Russian Arctic, parts of the Central Asian lowlands, Japan, parts of South America and a few other regions such as the Kerguelen Islands. For the present publication, the VMAP1 layers have been adjusted the original DCW tiles format.

The VMAP1, like the DCW before it, is a map-based map. To create it, published maps have been digitised. This results in occasional ‘faults’ where adjoining map sheets do not match. There are also occasional gaps where either the published map was not available (for instance in minor parts of the former Soviet Union), or it was available but did not contain certain types of information (e.g. contours).

The VMAP1 dataset includes contours, although there is no altitudinal colouring. To make the information easier to read, the contours can be underlain by the ‘old’ DCW hypsometric tints.

1.2.4. GeoBase (Canada)

Additional topographic data and terrain models are available for several countries. For example, it is possible to download digital files of the Canadian terrain model (scale either 1:250,000 or 1:50,000) from GeoBase, as well as the roads, lakes, rivers and a few other layers without charge. The data have to be transformed to WGS84. The data come in 1 × 1° tiles. This means that for one tile of our digital maps, 25 tiles of the coarser version of the GeoBase terrain model are required. This makes the application of GeoBase possible for the present purpose, but very slow.

1.2.5. The Shuttle Radar Topography Mission (SRTM)

For most parts of the globe, the easier to use and higher resolution SRTM terrain model is available. It covers the area between 60°N and 60°S. It was created by radar measurements from the Space Shuttle in 2000. The data have undergone various corrections. The voids in the original coverage have been filled, the coastlines have been corrected and the surfaces of lakes and the sea have been levelled. The data are easy to download and to import into ArcView. They can be used to calculate contours, so that a highly reliable and very accurate base topography is available. The SRTM topography is good enough to show individual drumlins. However, because it is radar-based and largely uncorrected for contents, it shows forest areas as elevations. This can be seen nicely, when the SRTM model is combined with satellite imagery.

When trying to identify the glacial features shown in the maps, such as key sites, additional information is desirable. The river courses are visible in the SRTM terrain model, at least in hilly terrain, but there is no possibility to colour them blue, unless information from VMAP1 can be used. Lakes and rivers can be calculated from satellite imagery by isolating the black areas in infrared channel 4, but this method is very time-consuming and also hindered by cloud shadows and—more importantly—by shadows in narrow valley...

Table of contents

• Cover image
• Table of Contents
• Preface
• Introduction
• Quaternary Glaciations in Austria
• The Pleistocene Glaciations in Belarus
• Pleistocene Glaciations of Czechia
• Pleistocene Glaciations in Denmark: A Closer Look at Chronology, Ice Dynamics and Landforms
• The Glacial History of the British Isles during the Early and Middle Pleistocene: Implications for the long-term development of the British Ice Sheet
• Pleistocene Glaciation Limits in Great Britain
• Pleistocene Glaciations in Estonia
• The Glaciation of Finland
• Quaternary Glaciations in the French Alps and Jura
• Recent Advances in Research on Quaternary Glaciations in the Pyrenees
• Late Pleistocene (Würmian) Glaciations of the Caucasus
• Pleistocene Glaciations of North Germany—New Results
• Pleistocene Glaciations of Southern Germany
• Glaciation in Greece
• Pliocene and Pleistocene Glaciations of Iceland
• Middle Pleistocene to Holocene Glaciations in the Italian Apennines
• Pleistocene Glaciations in Latvia
• Pleistocene Glaciations in Lithuania
• Pleistocene Glaciation in The Netherlands
• The Pleistocene Glaciations of the North Sea Basin
• Glacial History of Norway
• Quaternary Glaciations in Poland
• New Evidence on the Quaternary Glaciation in the Romanian Carpathians
• Ice Margins of Northern Russia Revisited
• Glaciations of the East European Plain
• Glacial History of the Barents Sea Region
• Glacial History of the Taymyr Peninsula and the Severnaya Zemlya Archipelago, Arctic Russia
• Glacial History of Slovenia
• Quaternary Glaciations of Turkey
• Limits of the Pleistocene Glaciations in the Ukraine
• Chronology and Extent of Late Cenozoic Ice Sheets in North America
• Alaska Palaeo-Glacier Atlas (Version 2)
• Glaciations of the Sierra Nevada, California, USA
• Pleistocene Glaciation of Hawaii
• Quaternary Glaciations in Illinois
• Ice-Margin Fluctuations at the End of the Wisconsin Episode, Michigan, USA
• The Quaternary of Minnesota
• Pleistocene Glaciation of Ohio, USA
• The Glaciation of Pennsylvania, USA
• Glaciation of Western Washington, USA
• The Quaternary of Wisconsin
• Summary of Early and Middle Pleistocene Glaciations in Northern Missouri, USA
• Pleistocene Glaciation of British Columbia
• Limits of Successive Middle and Late Pleistocene Continental Ice Sheets, Interior Plains of Southern and Central Alberta and Adjacent Areas
• Magnetostratigraphy of Quaternary Sections in Eastern Alberta, Saskatchewan and Manitoba
• Late Pleistocene–Early Holocene Decay of the Laurentide Ice Sheet in Québec–Labrador
• The Appalachian Glacier Complex in Maritime Canada
• Stratigraphical Record of Glacials/Interglacials in Northwest Canada
• The Greenland Ice Sheet During the Past 300,000 Years: A Review
• Pleistocene Glaciations in Southern Patagonia and Tierra del Fuego
• Pleistocene Glaciations in Northern Patagonia, Argentina: An Updated Review
• The High-Glacial (Last Glacial Maximum) Glacier Cover of the Aconcagua Group and Adjacent Massifs in the Mendoza Andes (South America) with a Closer Look at Further Empirical Evidence
• The Pleistocene Glaciations of Chile
• Late Quaternary Glaciations in Bolivia: Comments on Some New Approaches to Dating Morainic Sequences
• Ecuador, Peru and Bolivia
• Late Quaternary Glaciations of Ecuador
• Quaternary Glaciations of Colombia
• Late Quaternary Glaciations in the Venezuelan (Mérida) Andes
• Costa Rica and Guatemala
• Late Quaternary Glaciation in Mexico
• Late Pleistocene Glaciation of the Hindu Kush, Afghanistan
• Late Pleistocene Glaciations in North-East Asia
• Extent and Timing of Quaternary Glaciations in the Verkhoyansk Mountains
• Glaciation in the High Mountains of Siberia
• Late Quaternary Glaciation of Northern Pakistan
• Quaternary Glaciation of Northern India
• The High Glacial (Last Ice Age and Last Glacial Maximum) Ice Cover of High and Central Asia, with a Critical Review of Some Recent OSL and TCN Dates
• The Extent and Timing of Late Pleistocene Glaciations in the Altai and Neighbouring Mountain Systems
• Quaternary Glaciations
• Late Pleistocene and Early Holocene Glaciations in the Taiwanese High Mountain Ranges
• Late Quaternary Glaciations in Japan
• The Glaciation of the South-East Asian Equatorial Region
• The Glaciation of Australia
• Quaternary Glaciers of New Zealand
• Quaternary Glaciations of the Atlas Mountains, North Africa
• Quaternary Glacial Chronology of Mount Kenya Massif
• Glaciation in Southern Africa and in the Sub-Antarctic