Nothofagus pollen grain size as a proxy for long-term climate change: An applied study on Eocene, Oligocene, and Miocene sediments from Antarctica

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© 2015 Elsevier B.V. Understanding the nature of moisture availability in the Eocene, Oligocene, and Miocene of Antarctica is imperative for climate reconstructions and for understanding the potential influence of future climate change on modern landscapes. Previous studies have used traditional palynological techniques, fossil leaf margins, hydrogen isotope leaf waxes, and palynomorph δ13C values to indicate changes in moisture on the southernmost continent. Here, we explore the relationship between pollen width (equatorial diameter) and climate as a potential indicator of changes in moisture availability in Antarctica, a technique that had not been widely applied previously. To date, studies of pollen grain size response to environmental stress and the applicability of using fossil pollen grain size as a climate change proxy are limited. In this paper, we explore the relationship between pollen grain size and environmental stress (desiccation intensity) and whether such a relationship can be applied to fossil pollen from Antarctica. We measured the widths of 157 modern specimens of Nothofagus spp. (the genus of Southern beech) pollen from throughout the Southern Hemisphere and compared them with mean annual precipitation records to assess the relationship between pollen grain size and moisture availability. The widths of 458 Antarctic Nothofagidites lachlaniae-complex pollen grains (from Eocene, Oligocene, and Miocene cores) were then measured and compared to other paleoenvironmental proxies to evaluate whether or not a significant trend in size variability can be associated with a change in moisture availability through geological time. Modern data show a significant relationship between decreased moisture availability and increased pollen grain size and are consistent with a previous study, providing confidence for using changes in pollen grain size as an indicator of moisture. Fossil data show a 23% increase in average pollen grain size from the late Eocene through the early to mid Miocene, indicating a decrease in moisture availability in Antarctica during this time.

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Review of Palaeobotany and Palynology

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