Applicability of dinoflagellate cyst stratigraphy to the analyses of passive and active tectonic settings

Abstract

The notion that fluctuating tectonic stress patterns within or between continental plates directly influence the development of a given sedimentary basin is a well-established concept in geotectonics. In recent years it has become increasingly understood that notably the phase of relative compressional stress build-up causes dramatic changes in basin configurations, particularly at basin margins. Detailed assessment of the timing and duration of such phases, and characterisation of the concomitant changes in sedimentary facies distribution patterns (or paleoenvironments) is vital for the better understanding of this process and the various possible underlying mechanisms. Conventionally in Mesozoic and Cenozoic basin analysis notably, the study and interpolation of ammonites and/or calcareous microfossils (planktic and benthic foraminifera, calcareous nannoplankton) play an important role in the generation of chronostratigraphically and paleoenvironmentally significant information. However, these fossil groups are frequently unsuitable for intra-basinal correlations between marginal marine and deeper marine deposits. Meanwhile, notably in hydrocarbon exploration the study and interpretation of dinoflagellate cyst assemblages has become increasingly successful in stratigraphic analysis of Mesozoic and Cenozoic basins throughout the world. Studies on Cenozoic and Recent dinoflagellate cysts published over the last decades stress their sensitivity to environmental changes, and successful application in high resolution stratigraphy (e.g., Wall et aI., 1977; papers in Head and Wrenn, 1992; Brinkhuis, 1992; Versteegh, 1995). Moreover, the organic-walled cyst producing dinoflagellates are primarily associated with neritic environments, causing their consistent occurrence in marginal marine settings. In more offshore settings, the dinoflagellate signal increasingly consists of transported elements, thus allowing detailed correlations along onshore-offshore transects. This thesis therefore concentrates on the assessment of the applicability of this relatively new biostratigraphic tool on the timing and characterisation of periods (inception) of compression. For the purpose of this study compressional phases recognised in two highly contrasting basins were selected, viz. (I) in the Early Cretaceous of the primarily carbonate dominated Dauphinois Basin (SE France), developed in a tectonically passive setting, and (2) in the Oligocene of the mainly siliciclastic-dominated Pindos Foreland Basin (Epirus, NE Greece) which developed in front of the Pindos Thrust. 8