Description / Table of Contents:
INTRODUCTION In the context of evolutionary studies, it is the privilege of paleontologists to trace the actual course of evolutionary change over time spans that are adequate for such a slow process. At the same time it is their crux that they can not always hope to do this with the resolution necessary to reveal the causal relationships involved. The Tübingen Sonderforschungsbereich 53, "Palökologie", was primarily geared to study the interrelationships between organisms and environments in the fossil record. As is pointed out in this volume, such an approach will necessarily emphasize the static aspect of this relationship, all the more since this is what we need for the practical purposes of facies recognition. This was clone during a time interval of thirteen years at the level of individual species and taxonomic groups ("Konstruktions-Morphologie"), of characteristic facies complexes ("Fossil-Lagerstätten") and of assemblages ("Fossil- VergeseIlschaftungen") with the aim to recognize general patterns that persist in spite of the historical and evolutionary changes in the biosphere. But as our project came closer to its end, the possible causal relationships between physical and evolutionary changes became more tangible. This trend is expressed by symposia devoted to the biological effects of long term tectonic changes (KULLMANN & SCHÖNENBERG, eds., 1983) and of short term physical events (EINSELE & SEILACHER, eds., 1982). But in retrospect it appears that the time scales of the environmental changes chosen were either too large or too small to reveal the mechanisms of evolutionary response. The present volume is the outcome of a symposium of the projects B 20 ("Bankungsrhythmen in sedimentologischer, ökologischer und diagenetischer Sicht", directed by U. BAYER), D 40 ("Analoge Gehäuse-Aberrationen bei Ammonoideen", directed by J. WIEDMANN) and D 60 ("Substratwechsel im marinen Benthos", directed by A. SEILACHER) in September, 1983. tt addresses environmental changes at time scales large enough to produce more than a local ecological response and short enough to observe evolutionary and/or migratory changes at the species and genus levels. It also focusses on basins which by various degrees of isolation provided suitable sites for "evolutionary experiments", such as lakes and marginal epicontinental basins. In a way, this book is a successor of the previous one on "Cyclic and event stratification" (EINSELE & SEILACHER, eds., 1982). Small scale cycles and events are the 'primitives' of a sedimentary sequence, the lowermost scale from which it can be deciphered. However, medium and long term physical cycles commonly impress sedimentological and lithological trends on the stratigraphic column which are accompanied by faunal replacements and cycles. But since sedimentation is controlled both by physical and biological processes, which are intercorrelated in complicated ways, we also need to decode the stratigraphic text. In this effort, paleontological and sedimentological interpretation must go hand in hand. On the 'megascale' of global sea-level changes faunal and species evolution is triggered by opening and closing of migration pathways, sometimes providing us with malor biostratigraphic boundaries. As it turns out, however, integrated research and the choice of suitable scales do not free us from problems of resolution. Thus our inability to distinguish local speciation from ecophenotypic modification and from immigration in the fossil record excludes definite evolutionary answers even in well studied cases. Nevertheless we hope that this approach opens a fruitful discussion, in which stratigraphy, systematic paleontology and paleoecology will be reconciled in a concerted effort to eventually understand the evolutionary mechanisms of our biosphere.
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