ALBERT

Description / Table of Contents: PREFACE This volume presents results from members of the Project 216 "Global Biological Events in Earth History" of the International Geological Correlation Programme (IGCP). The project, initiated by the elder editor (O.H.W.) within the framework of the International Palaeontological Association (IPA) in the late 70s, was officially established in 1984. Subsequently, it led to the first three conferences on Global Bio-Events, and their respective symposia volumes: 1) In G6ttingen, West Germany in 1986 (WaUiser, O. H., Ed., 1986, Global Bio-Events, Springer-Verlag); in Bilbao, Spain in 1987 (Lamolda, M. A., Kauffrnan, E. G., and Walliser, O. H., Eds., 1988, Paleontology and Evolution: Extinction Events; Rev. Espafiola de Paleont., n. extraord.); and in Boulder, Colorado, U.S.A. in 1988 (this volume). The next meeting, on Innovations and Revolutions in the Biosphere, is planned in Oxford, England in 1990, to be hosted by Martin Brasier. During the history of this project, the focus of our research has shifted significantly. Initial focus was on specific global mass extinctions (e.g. the Precambrian/Cambrian, Frasnian/Fammenian, Cretaceous/Tertiary, and Eocene/Oligocene events) to a broader treatment of Phanerozoic mass extinctions, their differences or unifying factors, and their causal mechanisms. Subsequent meetings have attempted to focus attention on a fuller spectrum of global bio-events in Earth history. The Boulder Conference, and this volume, although still strongly influenced by the excitement of mass extinction research, expresses these new trends in bioevent studies. The Boulder conference, held on May 16-23, 1988, focused on a broad spectrum of Abrupt Changes in the Global Biota. Over 100 participants from 13 nations attended this meeting, representing diverse disciplines of palaeobiology, palaeoclimatology, palaeoceanography, sedimentology, geochemistry, and a broad spectrum of the stratigraphic and geological sciences. Four days of talks were supplemented by field trips to the continental Cretaceous/Tertiary boundary in the Raton Basin, New Mexico, and to the Cenomanian/Turonian mass extinction interval exposed near Pueblo, Colorado. The Conference itself was characterized by a great diversity of approaches to bio-event research, and the phenomenon of mass extinction. In particular, interactive causes involving both extraterrestrial and earthbound (tectonic, oceanographic, climatic) forces were discussed, and each major Phanerozoic mass extinction was treated by specialists in the field. In addition, many presentations focused on the causal mechanism and patterns of bio-event development that were not restricted to mass extinction intervals, but which could cause regional to global biotic response at any time in Earth history. Thus, both the conference, and this volume, focus attention on climatic and oceanic perturbations from anoxia, advection, rapid thermal change, toxic chemical enrichment, and energy shock from impacts and giant tsunamis as forcing mechanism for regional to global bio-events. The delicate balance of perched ocean/ctimate~fe systems under typical warm equable non-glacial Phanerozoic conditions, and their susceptibility to shock from even small perturbations, was a philosophical theme that ran throughout the meeting. The case for extraterrestrial forcing of tectonic, volcanic, and biological events was greatly strengthened by new data presented at this conference, with special concern for the effects of small comet/meteorite impacts in the oceans, and their chemical/physical/biological signature which might be used, in the absence of shocked minerals, microspheres or trace metals, to identify extraterrestrial events associated with global and regional bio-events. The conference benefitted from the introduction of much new data at high levels of resolution, especially from poorly studied mass extinction intervals. Interactive discussions, and many new ideas characterized the meeting. The new scientific results of this meeting are exciting; they are reviewed in the Conference Report published in Episodes (1988, v. 11, n. 4, p. 289-292). Most of the key papers presented at the Boulder meeting appear in this volume. What lies ahead in bio-event research? Clearly, a great deal of excitement and an age of discovery. We have only touched the surface of this new and dynamic field. We are starting to comprehend the dynamics of global mass extinctions, integrating detailed geochemical, physical and biological data into scenarios of cause and effect. But in the years ahead lies the job of understanding the whole spectrum of regional bioevents preserved in the ancient record, and especially the application of this research to solutions of the critical problems inherent in global change and the modern biotic crisis. Future directions for research at this conference include the investigation and modeling of abrupt chemical and thermal shifts in the ocean, the effects of impacts at deep ocean sites, the documentation of successful survival strategies and repopulation patterns following biotic crises, the deep ocean record of bio-events, and focus on alternative forces other than impacting to account for mass extinction events. This volume introduces some of these new pathways in bio-event research.

Description / Table of Contents: PREFACE This monograph is a compendium of revised papers which were originally presented at the "Ron Mather Symposium on Four-Dimensional Geodesy", 28-31 March, 1989, held at the University of New South Wales, Sydney, Australia. The symposium had the enthusiastic support of the International Association of Geodesy and the Australian Academy of Sciences. The symposium served two purposes: to honour the achievements of the late Professor Ron S. Mather, the distinguished Australian geodesist who died in 1978, and to review and report on the latest developments in four-dimensional geodesy. Four-dimensional geodesy is a convenient term for those geodetic principles and techniques which yield position, gravity and their time variations. In the past geodesists have tended to think of the earth as a static body, save from occasional savage earthquakes or volcanic eruptions. So, why the need to coin the term "four-dimensional geodesy") Because it explicitly recognises that time is an integral part of understanding geodetic measurements. But let's first identify the scope of modern geodesy. Geodesy has traditionally been concerned with two separate, though closely related, topics: accurate positioning of objects on the earth's surface, and mapping the earth's external gravity field. These are still the fundamental tasks of geodesy, although the spheres of application have now extended into space. However, present and emerging geodetic measurement technologies for gravity field mapping and positioning are sensitive to defolTnations of the earth's surface and gravity field. Within the geodetic community, this new emphasis on accounting for the time-varying characteristics of position and gravity has fundamental principles; in particular the establishment and maintenance of appropriate global reference systems for geodesy. At the same time, there has been a growing recognition by the earth sciences in general of the important role of geodesy in studying earth deformations, as well as atmosphere and ocean dynamic phenomena. The geodetic measurements, for example, are taken over time scales of hours to decades, and occasionally to a century or longer. Though this is only a small part of the whole deformation spectrum, it is a very important one. Geodesy bridges the low frequency part of the spectrum available from geological observations, with the high frequency end observed from, for example, seismic instrumentation. It's role in atmospheric and oceanographic studies is as a unique, high precision remote sensing tool. The revolution in geodesy is not, however, restricted to the measurement technology only. It is true that without the advances of space geodesy and terrestrial metrology, the notion of four-dimensional geodesy is a rather academic one. These advances, which now reveal time-variable signals above the measurement noise level, have important implications for all geodetic activities. The geodetic activities we refer to can be identified as: experiment design and measurement processes; definition and maintenance of highly stabie geodetic reference systems; data analysis; and interpretation of position and gravity results. Ultra high precision measurements are of little use without sophisticated analysis tools to extract the small signals in the data. The interpretation of geodetic results will be in error if insufficient attention is paid to ensuring that the reference systems to which the results relate are themselves stable. Clearly four-dimensional geodesy is as much about concepts and principles, as about computers and geodetic equipment. This diversity is reflected in the papers selected for this book. They range over topics related to the modem measurement tools, the reduction and analysis techniques, to the interpretation of geodetic results within the context of problems currently being investigated in the earth sciences. We would like to thank the International Association of Geodesy and the Australian Academy of Sciences for sponsorship of the Symposium. Unisearch Ltd., the commercial arm of the University of New South Wales, was the managing agent, and staff members of the School of Surveying and of Unisearch Ltd. were involved in the organisation of the Symposium. We would like to gratefully acknowledge these excellent contributions. Let us express also our gratitude for the useful guidance which we received from Prof. K. Lambeck, A. Prof. A. Stolz and Dr. R. Coleman of the Scientific Advisory Committee and the continuous support given by Prof. E.W. Grafarend. Sincere thanks are due to the authors of the selected papers for agreeing to contribute to this Monograph, and for their positive cooperation during the production of this volume.

Description / Table of Contents: The present study will provide an introduction into the biomechanics of trees and will give a critical survey of the phylogeny and the constructional principles of the tree habit. Since the trunk is considered the basic and crucial element of a tree, the analysis is largely restricted to a functional comparison of the stem anatomy of the various tree forms. It is based on the concept of constructional morphology, thus considering simultaneously the functional aspect and the ontogenetical and phylogenetical development of the various trunk types. The main questions to be answered in this study are; Why do trees exist? - Which are the constructional principles of tree trunks and when and in which group of plants do they appear? - How important are internal (phylogenetic) and external (functional, constructional) constraints? - What are the specific properties of the different constructional principles and does a correlation between trunk design and growth habit exist? - Is there a tendency in phylogeny to a better performance? The study does not (and cannot) intend to provide a detailed biophysical analysis of individual cases because experimental data on the mechanical properties of the structural elements of the different kinds of trees are still lacking. Instead, it will he the task to evaluate in a comprehensive and qualitative or semi-quantitative manner the available data of the morphology, anatomy and phylogeny of fossil and recent trees by using concepts of biomechanics and constructional morphology. Thus a somewhat holistic approach is used, which is becoming increasingly more acceptable today.