Palynostratigraphy and palaeoenvironments across the Oligocene–Miocene boundary within the Centinela Formation, southwestern Argentina
Published:January 01, 2004
G. R. Guerstein, M. V. Guler, S. Casadío, 2004. "Palynostratigraphy and palaeoenvironments across the Oligocene–Miocene boundary within the Centinela Formation, southwestern Argentina", The Palynology and Micropalaeontology of Boundaries, A. B. Beaudoin, M. J. Head
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Palynological analysis of the Centinela Formation, exposed in the foothills of the Patagonian Andes, has revealed the presence of pollen, dinoflagellate cysts, and chlorococcalean and prasinophycean algae. These groups are here reported from the Centinela Formation for the first time. Sporomorph and dinoflagellate cyst assemblages suggest a Late Oligocene and Early Miocene age. These results coincide with a 87Sr/86Sr age close to the age of the Oligocene-Miocene boundary obtained from the lower part of the section. Palynological information from the Centinela Formation permits correlation with Upper Oligocene and Lower Miocene units cropping out along the Atlantic Patagonian coast. Assemblages from the lower part of the section suggest that the beds were deposited under marine, near-shore palaeoenvironmental conditions with a strong continental influence. In the middle part of the section, high dinoflagellate cyst ratios coincide with a maximum flooding surface recorded in the Centinela Formation. Towards the top of the Centinela Formation, the sporomorph assemblages reflect the development of vegetation adapted to coastal environments, which agrees with the sparse occurrence of marine palynomorphs. A new dinoflagellate species, Hystrichostrogylon sulcatum, is proposed. This species appears to range across the Oligocene-Miocene boundary and is particularly abundant in the lowest Miocene.
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The Palynology and Micropalaeontology of Boundaries
This volume explores geological boundaries in time and space using palynology and micropalaeontology. Boundaries produce distinct signatures in the micropalaeontological record. Diffuse or sharp, gradual or abrupt, boundaries can tell us much about the response of biotic systems to environmental change in both marine and terrestrial realms. Different microfossil groups and geological contexts require their own approaches, definitions and considerations of boundaries. The papers in this compilation capture the current range of thinking on the methodology of boundary identification from biostratigraphical, ecological and palaeoenvironmental perspectives. Contributions span the Cambrian to Miocene and feature many fossil groups (including pollen, dinoflagellates, foraminifera, ostracodes, conodonts, and diatoms). With a strong Canadian and North American focus, the volume also includes contributions from Poland, Egypt, Belgium, Argentina and the United Kingdom.