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THE PALEOGEOGRAPHIC ATLAS PROJECT IN 2002


Introduction

The
Paleogeographic Atlas Project was begun at the University of Chicago in 1975 with the help of seed money from the Shell Development Company, and since that time has received substantial support from oil companies. Our objective has been to apply the plate tectonics paradigm to the reconstruction of the geological past in all its aspects, including sea-floor spreading, paleomagnetism, tectonics, topography, bathymetry, climate, oceanography, phytogeography and zoogeography. Our team has made primary contributions to most of these fields, but in general our work derives from the worldwide geological literature and has involved the compilation of data from some 28,000 catalogued references. Our approach is distinguished by the recognition that all of the above fields provide useful constraints for paleogeographic mapping, but also that a level of expertise is required in each field to make proper interpretations. Accordingly, our team includes tectonicists, sedimentologists, paleobotanists, invertebrate paleontologists, and climate modelers.

Initially, our work was devoted to the Paleozoic and we helped to establish the general latitudinal orientations and east-to-west order of the paleocontinents in the pre-Pangaean world (see references). With our Paleozoic maps we were able to determine the paleolatitudinal distributions of the climate-sensitive sediments and to establish that the Earth's present-day Hadley Cell circulation applies to these earlier intervals. In the 1980's, our emphasis shifted to the Mesozoic and Cenozoic and the focus was sharpened to details of individual basins and mountain ranges. David Rowley digitised the linear magnetic anomalies, and fitted the ocean basins for each anomaly pair. Judy Parrish showed that phosphorite and oil source rock occurrences could be predicted using basic principles of oceanic circulation. With the political opening of China, we established a continuing working relation with the Nanjing Institute of Geology and Palaeontology, which has enabled us to make many research trips and gather a large library on this geologically complicated region.

In the 1990's, we diversified our goals to include paleotopography and phytogeography, and revisited the subject of paleoclimatology. The topographic work covers the orogenic phase as well as the subsequent erosional history of mountain ranges, and forms the basis for climate modeling studies on the Permian and Jurassic. In the current generation of paleogeographic maps, which pay special attention to topography, we have completed four Permian maps (Ziegler et al., 1997), two Jurassic maps and one Cretaceous map. The phytogeographic approach has been to assemble huge taxonomic datasets for the Permian through Jurassic Periods for the purpose of tracing the climate evolution from the "Icehouse" to the "Greenhouse" world (see abstract). Also, we have developed an approach to reconstructing oceanic water masses using a new climate-sensitive sediment database and have applied this to the Permian (Ziegler et al., 1999). This work is yielding valuable new insights into the various settings for oil source rock formation.


Present Activities

The main thrust has been to consolidate our paleoclimate work on the Permian and at the same time to diversify our approaches to Jurassic climates. The Chicago team has been working closely with John Kutzbach at the Center for Atmospheric Research (University of Wisconsin) and we have completed a paper, "Permian climates: evaluating model predictions using global paleobotanical data" (Rees et al., 1999). The details of this NSF-sponsored research are now in press (Gibbs et al., Rees et al.) and will be ready for distribution soon. Phytogeographic maps for the Sakmarian and Wordian Stages are each based on over 100 floral lists and these have been the subject of a multivariate analysis to detect gradients reflecting variations in climate across the earth. Physiognomic adaptations and diversity patterns in the floral elements (Figure 2) have been compared with the climate-sensitive sediments in a new effort to generate biome maps for the world that account for each basin with Permian rocks. The Wisconsin team has also made biome maps, but their's are based on a General Circulation Model study of the Sakmarian and Wordian Stages. The result of these studies is the most detailed climate study yet of the deeper geologic past, and represents a new standard in the verification of model output.

The Permian climate work is based on papers mentioned earlier on paleogeography and paleotopography, and oceanic water masses, but we are applying still other approaches to this period. Our Russian colleague, Tatyana Leonova, has supplied us with a worldwide dataset on ammonoid distributions which we are currently using to test our conclusions on water mass characteristics and patterns. The idea is that provinces of marine organisms should act as watermass tracers, and the open ocean character of most ammonoids should make them useful in detecting current patterns. Ocean circulation modeling is still another approach, and Arne Winguth, who recently moved from Chicago to join the faculty at the University of Wisconsin, has begun such a study using our Permian maps and the Hamburg GCM. Initial results of this work show salinity and temperature patterns that compare closely with inferences we have made based on climate-sensitive sediments. A new dimension to continental climates is being provided by our Russian co-worker, Sergei Naugolnykh, who is an expert on Permian floras. He is helping with the interpretation of the Angaran Floral Realm. In addition his superb illustrations of Permian plant and animal communities provide a new dimension to presentations of our Permian floral work.

Our Jurassic climate work is also progressing on both continental and oceanic fronts. A paper on "Jurassic phytogeography and climates: new data and model comparisons" (Rees et al., 2000) is now published. In this paper, floral-based biome maps for the Lower, Middle and Upper Jurassic are presented, and an Upper Jurassic climate simulation with biome prediction map is included. For this paper we collaborated with Paul Valdes (University of Reading) for the modeling study, but the general approach is similar to our Permian work. Also, a major new climate-sensitive sediment database was compiled in 1998 by Postdoctoral Fellow, Helen Morgans for the eleven stages of the Jurassic Period. We are now in the process of reconstructing water mass maps using this information, and a major interest is in the bathymetric and oceanographic settings of the numerous oil source rock provinces of this period.


Future Plans

For many years we have been struggling with the difficulty and expense of publishing full-color paleogeographic maps, but now technology, in the form of the World Wide Web, presents a flexible new alternative. We received a grant from the University of Chicago to support the development of a Web-based approach to teaching undergraduates about paleogeography. We think the results will be adaptable to the wider audience of professional colleagues as well as the lay scientific public. The money is being used to expand our implementation of ArcView-based GIS software and the hardware to support it, and to hire a computer specialist to implement this program. The initial target will be to exploit the great diversity of Permian maps and diagrams we have completed in the last three years, including paleogeography, paleotopography, phytogeography, zoogeography, climatology and oceanography, together with diverse atmospheric and oceanic modeling runs and landscape reconstructions (Figures 2, 3, 4, 8). The goal will be to describe how the datasets are compiled and the maps are reconstructed, but also to point out the significance of the results. We hope to make the maps as interactive as possible, so the various datasets and map interpretations can be compared and used with ease.

We aim to expand the mapping work to include the Triassic, so that the transition from the Icehouse World to the Hothouse World can be viewed in terms of changes in geography, climate and biota. We have compiled a floral dataset, but not a climate-sensitive sediment dataset for each stage of the Triassic. When this is done, we can examine the 150 million year time span during which Pangea existed from the Permian through the Jurassic. Experience shows that a stage level approach is necessary to detect the large scale climate transitions. This is because the continents have moved across individual climate zones well within the span of a geologic period (1500 to 2000 km in many cases). Such transitions must be detected before the more interesting features of global climate change can be addressed. We are examining evolutionary events, such as the Permo-Triassic extinctions, in terms of the effects they had on floras in the geographic sense. Also, we are building a database of dinosaur occurrences using the distribution chapter of the forthcoming edition of "The Dinosauria". This information can help with paleogeographic interpretation by giving clues to migration routes between continents or to potential barriers like the Western Interior Seaway.

Finally, a major goal is to complete the set of fourteen paleogeographic maps for the Mesozoic and Cenozoic (e.g. Figure 1). Admittedly, this goal has eluded us for years, as more interesting and fundable projects have been given precedence. However, climate predictions and biogeographic patterns are only as good as the paleogeographic maps on which they are based. Over the years we have assembled over 8000 published paleogeographic maps representing various basins abround the world, and this collection has been updated substantially in the last year. Also, we have prepared good paleotopographic reconstructions for selected intervals of the Permian, Jurassic and Cretaceous, so bridging the gaps will not be that great a problem. The initial step will be the paleogeography of Africa and Arabia, and the Tethyan areas to the north, simply because of interest expressed by a number of our sponsors. This area of course contains the world's largest oil forming basins, and we intend to examine the relationship of source rock occurrence to the latitudinal motion of this area during the Mesozoic and Cenozoic. For further details and information on the personalities involved, see the following section.


Atlas Workers, and Their Current Projects

Karin Goldberg arrived with an MSc from the Universidade do Vale do Rio dos Sinos, Brazil in 1997 to begin PhD research. She is interested in the climatic fluctuations recorded in Permian rocks from the Parana Basin, Brazil, where glacial deposits are succeeded by coal beds, oil shales and finally red beds, from Early to Late Permian. She is determining whether this sequence was the result of global climate change or simply the northward migration of Gondwana beneath climate zones.Also, she is studying in detail the Irati oil shales, important source rocks that bear compelling geologic and environmental questions, and also constitute an excellent marker across the Gondwana basins. She intends to address the depositional setting in which the oil shales were formed, as well as to obtain radiometric ages from bentonites interbedded with the oil shales. Karin is working with drill cores where the Permian vertical succession was recorded without major breaks. She is coupling the traditional approach of using climate-sensitive sediments and paleontology, with sedimentary petrology and geochemistry. The methods used in her research include petrography, major element analysis, redox-sensitive element analysis, degree of pyritization, C/S ratio, carbon-isotope analysis, Sr-isotope analysis and U-Pb geochronology.

Tatyana A. Grunt and Tatyana B. Leonova of the Paleontological Institute of the Russian Academy of Sciences, Moscow are collaborating on a project "Permian Biogeography of Brachiopods and Ammonoids", funded by the U.S. Civilian Research and Development Foundation. This has allowed for exchange visits for both Russian and U.S. teams in 1997 and 1998. In August 1998, we all participated in an international symposium, "Upper Permian Stratotypes of the Volga Region". We are comparing the biogeographic patterns observed in these fossil groups with the oceanic water-masses defined in the Permian Period (Ziegler et al., 1999). The worldwide ammonoid data set has been completed, and is being plotted and analyzed by Al McGowan (see below).

Alistair McGowan worked on evolutionary trends in ammonoids for his Master's thesis at the University of Bristol, and arrived here in late 1998 to begin work as a PhD student. He is helping us to construct distribution maps for Leonova's Permian ammonoid database (see above), and is correlating the patterns with geography and oceanic water masses (as defined by Ziegler et al., 1999). His thesis work will be focused on Triassic ammonoid macroevolution with reference to biogeography and climate.

Helen S. Morgans completed a DPhil thesis at Oxford University in 1997 and spent 1998 with us on a Lindemann Fellowship, assembling a database on climate-sensitive sediments for the Jurassic (Figure 5) which is similar in style to our new Permian database. Since these two geologic periods represent extremes in climate between the "Hothouse" and "Icehouse" worlds, these databases should reflect these contrasts, and provide material to test GCM results. Helen has returned to Oxford, but continues to work with us on finalizing this project, presenting some of the results at Geoscience 2000 in the UK (Morgans et al., 2000).

Sergei S. Naugolnykh is a paleobotanist at the Geological Institute, Russian Academy of Sciences, Moscow and he joined us for two months in 1999 on a project funded by the U.S. Civilian Research and Development Foundation. He is a specialist on the Permian floras of the Uralian basin and has compiled taxonomic lists from the Russian language literature for our database. Sergei is collaborating with Allister Rees and Fred Ziegler on reconstructing the floral biomes of the Permian. As part of this work, Sergei prepared some landscape reconstructions showing representative floral and faunal elements.

Peter McAllister Rees, who was a post-doctoral fellow at the Open University, UK, has worked with the Atlas Project since 1993 and is now a full time Research Associate in Chicago. Allister is a paleobotanist and has been applying multivariate statistics to our extensive Permian, Triassic and Jurassic floral databases in order to analyze temporal and spatial patterns of change in worldwide vegetation. He is also applying a knowledge of foliar physiognomy to elements of each flora to determine just what these patterns mean in terms of precipitation and temperature. This is probably the most extensive effort ever undertaken in the field of paleobiogeography and paleoclimate data interpretation in terms of the geographic coverage and the number of taxonomic lists compiled, and provides the first rigorous means of testing climate models for these intervals. Allister and Fred Ziegler continue to collaborate with John Kutzbach and Arne Winguth at the Center for Climate Research (University of Wisconsin-Madison). The focus has been on detailed analyses of our extensive Permian floral and climate-sensitive sediment database and comparison with their climate model results (e.g. Figure 4) to achieve truly integrated paleoclimate data/model studies. He is also studying patterns of land plant diversity in the Permian and Triassic, which encompassed a time of icehouse-hothouse climate transition, ca 25 degrees northwards motion of the Pangean supercontinent, and the biggest recorded mass extinction (the Permo-Triassic boundary).

David B. Rowley is now chairman of our department, and has been an integral member of the Atlas Project since 1982. Dave continues to work on a number of fronts related to the Atlas Project. Recent NSF funding of a project entitled "Collaborative Research: Time of initiation of the India-Asia collision east of Mount Everest" provides 2 years of funding for field-based studies of the stratigraphic record along the Indus-Yarlung Zangpo suture. This work is being done in collaboration with Bill Kidd at SUNY Albany and Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences. Previous work summarized in Rowley (EPSL 1996) and Rowley (Journal of Geology 1997) suggest that the collision may be diachronous from west to east along the suture, but direct stratigraphic evidence supporting this has yet to be found, and is the focus of our current research. Field based studies of the Dabie Shan ultrahigh pressure metamorphic rocks continues as discussed below in regards to Feng Xue. Dave has focused most of his attention on the problem of paleoaltimetry. In collaboration with Ray Pierrehumbert they have developed a stable isotope-based paleoaltimeter. The first application of this paleoaltimeter was to Late Miocene lacustrine carbonates in the Thakkhola Graben in Nepal,based on sampling by Kip Hodges and Co from MIT. This work implies that High Himalayas had already achieved their current stature by the Late Miocene. Further work applying this paleoaltimeter to Tibet has recently received 2 years of funding from the NSF. In addition, Dave has begun a re-analysis of the Atlas Project plate motion model using the most recent release of satellite gravity data by Smith and Sandwell. This provides an independent dataset for the trajectories of transforms and fracture zones that will be used to refine our current kinematic models.

Alfred M. Ziegler, with the help of Dave Rowley and Allister Rees, directs the Paleogeographic Atlas Project, and is involved with many of the research efforts mentioned above. He is concentrating on the completion of the Permian atlas, and has begun work on the basic Mesozoic reconstructions. Fred has a particular interest in explaining the warm climates of the "Greenhouse World" and presented an initial paper on "Warm Polar Currents" at the AGU meeting in May, 1998. This project was stimulated by the observations that high-latitude fossil floras during many geologic intervals indicate temperate conditions and that the polar oceans during these intervals had better connections with the main ocean basins. John Kutzbach is conducting climate modeling experiments to determine if warm currents would be deflected into polar regions during these times, and inital results seem to confirm the theory.

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PGAP Home Permian Jurassic Movies, Slideshows and Maps Publications Recent Abstracts (full text) About our Data Links