The warm interglacial Marine Isotope Stage 31; evidences from the calcareous nannofossil assemblages at Site 1090 (Southern Ocean)

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doi: 10.1016/j.marmicro.2009.03.002
Author(s): Maiorano, Patrizia; Marino, Maria; Flores, José-Abel
Author Affiliation(s): Primary:
Universita di Bari, Dipartimento di Geologia e Geofisica, Bari, Italy
Other:
Universidad de Salamanca, Spain
Volume Title: Marine Micropaleontology
Source: Marine Micropaleontology, 71(3-4), p.166-175. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0377-8398 CODEN: MAMIDH
Note: In English. Based on Publisher-supplied data; includes 2 appendices
Summary: Calcareous nannofossil assemblages have been investigated at Ocean Drilling Program (ODP) Site 1090 located in the modern Subantarctic Zone, through the Pleistocene Marine Isotope Stages (MIS) 34-29, between 1150 and 1000 ka. A previously developed age model and new biostratigraphic constraints provide a reliable chronological framework for the studied section and allow correlation with other records. Two relevant biostratigraphic events have been identified: the First Common Occurrence of Reticulofenestra asanoi, distinctly correlated to MIS 31-32; the re-entry of medium Gephyrocapsa at MIS 29, unexpectedly similar to what was observed at low latitude sites. The composition of the calcareous nannofossil assemblage permits identification of three intervals (I-III). Intervals I and III, correlated to MIS 34-32 and MIS 30-29 respectively, are identified as characteristic of water masses located south of the Subtropical Front and reflecting the southern border of Subantarctic Zone, at the transition with the Polar Front Zone. This evidence is consistent with the hypothesis of a northward shift of the frontal system in the early Pleistocene with respect to the present position and therefore a northernmost location of the Subantarctic Front. During interval II, which is correlated to MIS 31, calcareous nannofossil assemblages display the most significant change, characterized by a distinct increase of Syracosphaera spp. and Helicosphaera carteri, lasting about 20 ky. An integrated analysis of calcareous nannofossil abundances and few mineralogical proxies suggests that during interval II, Site 1090 experienced the influence of subtropical waters, possibly related to a southward migration of the Subtropical Front, coupled with an expansion of the warmer Agulhas Current at the core location. This pronounced warming event is associated to a minimum in the austral summer insolation. The present results provide a broader framework on the mid-Pleistocene dynamic of the ocean frontal system in the Atlantic sector of the Southern Ocean, as well as additional evidence on the variability of the Indian-Atlantic ocean exchange. Abstract Copyright (2009) Elsevier, B.V.
Year of Publication: 2009
Research Program: ODP Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Algae; Assemblages; Atlantic Ocean; Biostratigraphy; Cenozoic; Coccolithophoraceae; Gephyrocapsa; Interglacial environment; Leg 177; MIS 31; Marine environment; Microfossils; Middle Pleistocene; Nannofossils; ODP Site 1090; Ocean Drilling Program; Paleo-oceanography; Paleoclimatology; Paleoenvironment; Plantae; Pleistocene; Principal components analysis; Quaternary; Reticulofenestra asanoi; South Atlantic; Southern Ocean; Statistical analysis
Coordinates: S425449 S425449 E0085359 E0085359
Record ID: 2010013734
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands