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Cobianchi, M.
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- PublicationRestrictedA Pleistocene warming event at 1 Ma in Prydz Bay, East Antarctica: Evidence from ODP Site 1165(2008)
; ; ; ; ; ;Villa, G.; Dipartimento di Scienze della Terra, Università di Parma ;Lupi, C.; Dipartimento di Scienze della Terra, Università di Pavia ;Cobianchi, M.; Dipartimento di Scienze della Terra, Università di Pavia ;Florindo, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Pekar, S. F.; Lamont-Doherty Earth Observatoryof ColumbiaUniversity, Palisades, NewYork; ; ; ; Bio- and magnetostratigraphic age data and nannofossil assemblage analysis from ODP Site 1165 evidence an anomalous warming event of the surface waters in and around Prydz Bay during the Early Pleistocene, approximately 1 Ma. This results from an increase in the abundance of nannofossils at Site 1165, that occurred at 1 Ma. Detailed high-resolution sampling permits a new bio-magnetostratigraphic interpretation for ODP Site 1165. A decrease in δ18O values at Sites 1165 and 1167 also occurs at this time, supporting the presence of warming conditions in the Prydz Bay area. A return to colder surface waters, indicated by the absence or rare occurrence of nannofossils in the upper cores from Site 1165, suggests that more stable glacial conditions existed in the Prydz Bay basin, for the last 900 ka. The biogenic carbonate sequence identified at Site 1167 is similar to the carbonate shales recovered from the Cape Roberts Project 1. Both have been dated at about 1 Ma, supporting the idea that a significant surface waters warming occurred during the Pleistocene. These data and the presence of calcareous nannofossils from locations around the Antarctic continent also suggest that the warming event was not limited to the analysed basin, but it extended around the East Antarctic continent. These new evidence call for a re-evaluation of the notion that the East Antarctic Ice-Sheet has experienced stable conditions similar to today since the late Neogene.158 26 - PublicationRestrictedRecords of Climate and Paleoceanographic Variability during the Mid-Pleistocene Transition in the Pacific Ocean(2008)
; ; ; ;Venuti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Cobianchi, M.; Dipartimento di Scienze della Terra, Università degli Studi di Pavia, Pavia, Italy ;Lupi, C.; Dipartimento di Scienze della Terra, Università degli Studi di Pavia, Pavia, Italy; ; ; ; ;Tewles, K. B.; Nova Science Publishers, Inc.Paleoclimatic proxies from sedimentary marine sequences often record orbital frequencies (eccentricity, obliquity, and precession) and reveal the effects of insolation on environmental processes. During Pleistocene an important transition occurred in the time interval between 1.25 and 0.7 Ma, the so called Mid-Pleistocene Transition (MPT; Clark et al., 2006) that marked the passage from glacial cycles with 41 to 100-kyr rhythm. In the southwestern Pacific Ocean this transition reflects in paleoceanographic changes as the case east of New Zealand in correspondence of the northward flow of the Deep Western Boundary Current (DWBC). Many studies show evidences of the MPT by the use of proxies dependent on bulk and magnetic sediment grain-size and which provide qualitative information on variations in the strength of the deep Pacific Ocean inflow, possibly directly related to fluctuations of Antarctic Bottom Water production. Many works have been performed about these topics which revealed the importance to improve and enhance the knowledge through future researches.147 29