Paul Bown - IODP Expedition 320 participation

点击翻译按钮获取中文摘要

1. Intercalibration of stratigraphic datums from the Paleogene PEAT splice Undertake shipboard and post-cruise calcareous nannofossil biostratigraphy for the Eocene-Miocene interval and integrate these data with those from other PEAT stratigraphers. The completion of a astronomically calibrated Paleogene stratigraphic 'mega-splice' is an Expeditions 320/321 primary objective. 2. Calcareous nannofossil evolution through Eocene hyperthermals and the Eocene climatic optimum The early to middle Eocene saw a rise in nannofossil diversity to a Cenozoic maximum. I will investigate the timing and structure of this increase and examine whether climatic shifts played a significant role in the evolution of the oceanic plankton at this time. If early Eocene hyperthermal intervals are recovered I will investigate the nannofossil response at high resolution to test for the forcing effects of temperature and/or ocean chemistry changes (e.g. acidification) on nannofossil abundance, diversity and evolutionary rates. 3. Climate, carbonate accumulation and nannofossil evolution through the middle to late Eocene Carbonate and silica accumulation events have been identified in previous records from the equatorial Pacific and linked to changes in planktonic productivity and global climate shifts. This time interval also saw a precipitous decline in the diversity of nannofossils from which the group has arguably never completely recovered. I will generate quantitative nannofossil abundance and diversity records on short and long timescales in order to examine the relationships between nannofossil productivity and evolution, carbonate accumulation and paleoclimate/paleoceanography. In detail, I am interested in the nannofossil record across the Middle Eocene climatic optimum (MECO; 42Ma) and the biogenic accumulation and carbonate compensation depth (CCD) events that follow, and precede the Eocene/Oligocene transition (48-34Ma). I will also investigate the nature of nannofossil preservation as sites approach the CCD, in particular its influence on preserved diversity and proxy records. 4. Eocene-Oligocene transition (EOT) - investigating links between ocean chemistry and plankton evolution A major restructuring in plankton ecosystems across the EOT suggests that the expansion of Antarctic ice sheets is coincident with a significant perturbation in low-latitude surface ocean environments. Evidence from calcareous nannofossil assemblages indicates that this may be due to a widespread increase in nutrient availability. A marked shoaling of the CCD immediately prior to the EOT has hampered the production of a comparable record from deep-sea sediments. We propose to measure absolute nannofossil species abundances and, combined with the cyclostratigraphic age model, quantify nannofossil accumulation rates across the EOT. We would also actively collaborate with PEAT scientists in the production of the full range of carbonate, silica, nannofossil and foraminiferal accumulation rates. 5. Early Miocene glaciation (Mi-1) and the plankton ecosystem The relatively short but significant early Miocene glacial episode, Mi-1, is in some ways similar to the EOT climate event. There has, however, been little observed response within planktonic ecosystems to Mi-1. We would apply the methodology used in objective 4 to Mi-1 (PEAT-6C). This is an extension of objective 4 and we will collaborate with PEAT nannofossil biostratigraphers who have this interval as a primary objective.