Trace Fossil Assemblages in Middle Triassic Marginal Marine Deposits, Eastern Border of the Massif Central, France
Georges R. Demathieu, 1985. "Trace Fossil Assemblages in Middle Triassic Marginal Marine Deposits, Eastern Border of the Massif Central, France", Biogenic Structures: Their Use in Interpreting Depositional Environments, H. Allen Curran
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An integrated study of trace fossil assemblages from Middle Triassic deposits of the eastern border of the French Massif Central including analysis of primary sedimentary structures plant imprints invertebrate lebensspuren and vertebrate trackways has enabled reconstruction of the depositional environments. In this study, statistical methods are used to support morphological observations, permitting better definition of the ichnotaxa formed by reptilian vertebrates In addition by applying other statistical methods and the concept of “Euclidian distance” it is possible to estimate population sizes for the trackmakers. Using these data a reconstruction of the biological relationships between the different trackmakers represented by tracks in the trackway areas and between the trackmakers and their environment is proposed.
Lithology primary sedimentary structures and lebensspuren indicate that the trackway areas of this Triassic borderland were large sandy shores at the edge of a sea orlagoon The succession of footprint bearing beds in the lower sandstones or “Grés inférieurs du Lyonnais,” suggests cycles of deposition due to repeated marine transgressions.
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Organisms of one sort or another today inhabit virtually every sediment environment on Earth, and the rock record tells us that this has been the case through the greater part of our planet’s history. Furthermore, organisms leave their mark in most sedimentary settings, either directly in the form of body fossils or indirectly as biogenic structures. In addition to their often profound modifying effects on substrates, ancient biogenic structures preserve a record of organism behavioral activity in response to substrate and other paleoenvironmental controls. Thus, biogenic structures can be highly useful as facies indicators and can provide valuable clues to the interpretation of paleodepositional environments. The purpose of this volume is to present a broad spectrum of case-book examples of the use of biogenic structures in the interpretation of depositional environments.