#Second extinction black site series#

The western Pacific warm pool (WPWP) into the Indian Ocean (Du and Qu, 2010 The ITF is the warm surface current that transports water from Variation in the intensity of the Indonesian throughflow (ITF) and the LeeuwinĬurrent (LC). Modern ocean circulation in the area is controlled by a Of the Indo-Pacific warm pool and near the only remaining “equatorial warm-water valve”. These challenges because of its position within the dynamic climate system The NW Australian shelf serves as an important test case to try and tackle The base map was generated using the ocean data visualisation tools of EU Copernicus Marine Service Information (MyOcean Pro). Main surface oceanography of the Indo-Pacific region, including the Indonesian throughflow (ITF dark-red arrows) and the main path of the Leeuwin Current (LC lighter-red arrow adapted fromĪuer et al., 2019 Gallagher et al., 2009) and the Holloway Current (HC), which in this study are considered as one, are shown. U1461 (NW Australian shelf), ODP Sites 762 and 763 (eastern Indian Ocean),Īnd ODP Site 757 and DSDP Site 214 (equatorial Indian Ocean). Other sites discussed in the text (black dots) include IODP Site

(NW Australian shelf green dots) are the primary sites of investigation in This further complicates the task of using nannofossil assemblages to consistently differentiate between signals of regional paleoclimatic forcing and broad-scale evolutionary trends and changes in the ocean's nutrient budget.įigure 1Modern bathymetric map indicating shelf environments ( <200 m depth dark-grey shading) and site locations. In such areas, calcareous nannoplankton communities may be significantly different from open-ocean marine settings owing to the influence of parameters such as seasonal water column stratification and tidal mixing (Sharples et al., 2009 Van Oostende et al., 2012), as well as variations in river runoff and nutrient input (Harlay et al., 2010 Poulton et al., 2014). Because of the interplay of regional and global imprints preserved in the sedimentary record, nannofossil assemblage studies come with a set of challenges, especially in highly dynamic environments across continental shelves. The abundant and well-preserved fossil record of their calcareous platelets (calcareous nannofossils) in shallow marine and deep-sea sediments has been used to reconstruct regional paleoclimatic and paleoceanographic changes but also global processes such as evolution (speciation and extinction) and basin-wide changes in ocean chemistry (Beaufort et al., 1997 Bolton et al., 2016 O'Dea et al., 2014 Thierstein and Young, 2004). Significant changes in nannofossil abundance and species composition that reflect broader-scale processes and evolutionary events, such as the termination of the late Miocene to early Pliocene biogenic bloom in the eastern Indian Ocean (4.6–4.4 Ma) and the extinction of Sphenolithus spp. ( ∼3.54 Ma), occurred long after this regional regime shift.Ĭalcareous nannoplankton (including coccolithophores) are sensitive indicators of current and past climatic change because, as primary producers, they are primarily dependent on the prevailing (and seasonally changing) physicochemical conditions, such as nutrient availability and temperature, within the upper sunlit layers of the ocean. By documenting shifts in the dominant species within the nannofossil assemblages and comparing these to paleotemperature gradients between the NW Australian shelf and the eastern Indian Ocean, we identify a significant change in the ecological and oceanographic regime that occurred across the Miocene–Pliocene boundary (5.4–5.2 Ma), which can be attributed to an overall intensification of the upper water column mixing over the shelf.

#Second extinction black site series#

In this study, we investigate two astronomically tuned calcareous nannofossil time series from IODP Sites U1463 and U1464 to track long-term changes in ocean circulation and water column stratification, which influences the availability of nutrients in the upper photic zone and is considered to be a primary control on the (paleo)productivity of marine phytoplankton.

Despite the available information regarding the general paleoclimatic conditions, little is known about the concurrent regional ocean circulation patterns and the relative strength of seasonally flowing boundary currents, such as the Leeuwin Current. Uninterrupted Indonesian throughflow and was characterised by prevailing humid conditions, including increased precipitation and river runoff. During the period from 6 to 3.5 Ma, the area was dominated by warm, tropical waters supplied by an intensified, Unique records of paleoclimatic variations under warmer-than-presentĬonditions. The International Ocean Discovery Program (IODP) Expedition 356, provide Late Miocene to Pliocene sediments from the NW Australian shelf, drilled by