Upper Triassic–lowermost Jurassic palynology and palynostratigraphy: a review
Published:January 01, 2010
This review advances understanding of the palynostratigraphy of the Late Triassic–Early Jurassic by correlating the established palynozonations for the northern and southern hemispheres. Previous palynological studies have contributed greatly to our understanding of the biostratigraphy, paleoclimatology and paleogeography of the Upper Triassic. In general, palynology is a good tool for interregional cross-correlation of marine and non-marine successions because palynomorphs, unlike most of other fossils, commonly are present in continental and marine environments. Currently, however, biostratigraphical resolution based on Upper Triassic palynomorph assemblages is rather low, primarily because of the rarity of successions that are independently dated (i.e. via ammonoids, conodonts, isotopes, paleomagnetism) to correlate the palynomorph assemblages, but also for other reasons, such as microfloristic provincialism, palaeoenvironmental conditions and differential preservation of palynomorph assemblages. During the last few decades many palynological studies have attempted to integrate and improve the biostratigraphical correlations and paleoclimatologic reconstructions across the Triassic–Jurassic boundary. Several authors have recognized specific microfloral assemblages with well-defined and recognizable suites of palynomorphs that enhance the importance of palynomorphs in the definition of Triassic–Jurassic stages. Comparison of the palynomorph assemblages from different biostratigraphical stages demonstrates that a change occurred in the palynofloral composition of the Tethyan domain between the Carnian and the earliest Hettangian that was gradual and without abrupt changes.
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The Triassic Timescale
The Mesozoic Era begins with the approximately 50-million-year-long Triassic Period, a major juncture in Earth history when the vast Pangaean supercontinent completed its assembly and began its fragmentation, and the global biota diversified and modernized after the end-Permian mass extinction, the most extensive biotic decimation of the Phanerozoic. The temporal ordering of geological and biotic events during Triassic time thus is critical to the interpretation of some unique and pivotal events in Earth history. This temporal ordering is mostly based on the Triassic timescale, which has been developed and refined for nearly two centuries. This book reviews the state of the art of the Triassic timescale and includes comprehensive analyses of Triassic radio-isotopic ages, magnetostratigraphy, isotope-based and cyclostratigraphic correlations and timescale -relevant marine and non-marine biostratigraphy.