Browsing by Author "Blattler, Clara L."
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- Cyclic anoxia and organic rich carbonate sediments within a drowned carbonate platform linked to Antarctic ice volume changes: Late Oligocene-early Miocene MaldivesPublication . Swart, Peter K.; Blattler, Clara L.; Nakakuni, Masatoshi; Mackenzie, Greta J.; Betzler, Christian; Eberli, Gregor P.; Reolid, Jesus; Alonso-Garcia, Montserrat; Slagle, Angela L.; Wright, James D.; Kroon, Dick; Reijmer, John J. G.; Mee, Anna L. Hui; Young, Jeremy R.; Alvarez-Zarikian, Carlos A.; Bialik, Orr M.; Guo, Junhua Adam; Haffen, Sebastian; Horozal, Senay; Inoue, Mayuri; Jovane, Luigi; Lanci, Luca; Laya, Juan Carlos; Luedmann, Thomas; Nath, B. Nagender; Niino, Kaoru; Petruny, Loren M.; Pratiwi, Santi Dwi; Su, Xiang; Sloss, Craig R.; Yao, ZhengquanThis paper reports on the newly discovered occurrence of thick sequences (similar to 100 m) of Late Oligocene and Early Miocene (similar to 24.9 to similar to 20 Ma) interbedded organic-rich sediments (sapropels) and pelagic (organic poor) carbonates at Sites 01466 and U1468 drilled in the Maldives archipelago during the International Ocean Discovery Program (IODP) Expedition 359. This occurrence is unusual in that this sequence is located > 1000 m above the surrounding ocean floor within an inter-atoll basin and not linked to any known global oceanic events. Total organic content reaches as high as 35% in the darker layers, while the interbedded carbonates have concentrations of less than 0.1%. Trace elements characteristic of anoxic waters, such as Mo, V, Cr, U, and Pb, correlate positively with concentrations of organic carbon. Nitrogen isotopic data show no evidence that the intervals of high total organic carbon are related to enhanced productivity driven by upwelling. Instead, high organic carbon is associated with intervals of anoxia. We propose that sea-level fluctuations linked to changes in Antarctic ice volume restricted exchange with the open ocean causing bottom waters of the inter-atoll basin to become anoxic periodically. The architecture of the platform at the end of the Oligocene, combined with the global sea-level highstand, set the stage for orbitally-driven sea-level changes producing cyclic deposition of sapropels. The proposed mechanism may serve as an analogue for other occurrences of organic carbon rich sediments within carbonate platform settings. (C) 2019 Elsevier B.V. All rights reserved.
- Magnetic properties of early Pliocene sediments from IODP Site U1467 (Maldives platform) reveal changes in the monsoon systemPublication . Lanci, Luca; Zanella, Elena; Jovane, Luigi; Galeotti, Simone; Alonso-Garcia, Montserrat; Alvarez-Zarikian, Carlos A.; Bejugam, Nagender Nath; Betzler, Christian; Bialik, Or M.; Blattler, Clara L.; Eberlik, Gregor P.; Guo, Junhua Adam; Haffen, Sebastien; Horozal, Senay; Inoue, Mayuri; Kroon, Dick; Laya, Juan Carlos; Mee, Anna Ling Hui; Luedmann, Thomas; Nakakunir, Masatoshi; Niino, Kaoru; Petruny, Loren M.; Pratiwi, Santi D.; Reijmer, John J. G.; Reolid, Jesus; Slagle, Angela L.; Sloss, Craig R.; Su, Xiang; Swart, Peter K.; Wright, James D.; Yao, Zhengquan; Young, Jeremy R.We report a study of the magnetic stratigraphy and the anisotropy of isothermal remanent magnetization of Pliocene sediments from International Ocean Discovery Program (IODP) Site U1467 drilled in the Maldives platform (Indian Ocean) during Exp. 359. Magnetic stratigraphy gives a precise record of geomagnetic reversals of the early Pliocene from approximately 5.3 Ma to 3.1 Ma providing a detailed age model in an interval where the biostratigraphic record is scarce. We use the anisotropy of isothermal remanent magnetization (AIRM) to investigate the statistical orientation of fine magnetic particles and provide data on the strength and direction of bottom currents during the early Pliocene. The strength of bottom currents recorded by the AIRM, shows a prominent increase at the top of Chron C3n.1n (about 4.2 Ma), and the current direction (NE - SW) is consistent with that of modern instrumental measurements. Since bottom currents in the Maldives are driven by the monsoon, we speculate that the 4.2 Ma increase of bottom currents could mark the onset of the present-day setting, probably related to the coeval uplift phase of the Himalayan plateau.
- The abrupt onset of the modern South Asian Monsoon windsPublication . Betzler, Christian; Eberli, Gregor P.; Kroon, Dick; Wright, James D.; Swart, Peter K.; Nath, Bejugam Nagender; Alvarez-Zarikian, Carlos A.; Alonso-Garcia, Montserrat; Bialik, Or M.; Blattler, Clara L.; Guo, Junhua Adam; Haffen, Sébastien; Horozal, Senay; Inoue, Mayuri; Jovane, Luigi; Lanci, Luca; Laya, Juan Carlos; Mee, Anna Ling Hui; Luedmann, Thomas; Nakakuni, Masatoshi; Niino, Kaoru; Petruny, Loren M.; Pratiwi, Santi D.; Reijmer, John J. G.; Reolid, Jesus; Slagle, Angela L.; Sloss, Craig R.; Su, Xiang; Yao, Zhengquan; Young, Jeremy R.The South Asian Monson (SAM) is one of the most intense climatic elements yet its initiation and variations are not well established. Dating the deposits of SAM wind-driven currents in IODP cores from the Maldives yields an age of 12.9 Ma indicating an abrupt SAM onset, over a short period of 300 kyrs. This coincided with the Indian Ocean Oxygen Minimum Zone expansion as revealed by geochemical tracers and the onset of upwelling reflected by the sediment's content of particulate organic matter. A weaker 'proto-monsoon' existed between 12.9 and 25 Ma, as mirrored by the sedimentary signature of dust influx. Abrupt SAM initiation favors a strong influence of climate in addition to the tectonic control, and we propose that the post Miocene Climate Optimum cooling, together with increased continentalization and establishment of the bipolar ocean circulation, i.e. the beginning of the modern world, shifted the monsoon over a threshold towards the modern system.