Paleomagnetic and environmental magnetic insights into the middle to late Pleistocene stratigraphy of the 8° North Bengal Fan transect, IODP Expedition 354

Author(s): Reilly, B. T.; Selkin, P. A.; Meynadier, L.; Savian, Jairo F.; Weber, Michael E.; Schwenk, T.; Spiess, V.; Stoner, J. S.; France-Lanord, C.; Klaus, A.
Author Affiliation(s): Primary:
Oregon State University, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, OR, United States
University of Washington, Tacoma, United States
Institut de Physique du Globe, France
Institute of Astronomy, Geophysics and Atmospheric Sciences, Brazil
University of Cologne, Germany
University of Bremen, Germany
Texas A&M University, United States
Volume Title: AGU 2015 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2015; American Geophysical Union 2015 fall meeting, San Francisco, CA, Dec. 14-18, 2015. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: IODP Expedition 354 cored seven sites along a ∼320 km transect of the Bengal Fan at 8°N. Assessing the Pleistocene fan development and depocenter migration in the upper 150-220 m of the Bengal Fan was a primary goal of this expedition. Because any one site includes local variations in depositional processes, the transect approach and accurate stratigraphic correlation of sites is essential to understand overall fan development. Within this transect framework, integrating sediment fluxes across the fan allows for reconstruction of regional climate and tectonic signals through time. A hemipelagic unit deposited at ∼1-2.5 cm/ka late in the Matuyama Chron, recording both the Cobb Mountain (1.173-1.185 Ma) and Jaramillo (0.988-1.072 Ma) Subchrons, was observed at all sites across the transect. This hemipelagic unit provides robust correlation between core derived chronologies and seismic imaging in the Middle Pleistocene. Correlation and orbital tuning of distinctive variations in physical properties (e.g. sediment lightness, wet-bulk density, and magnetic susceptibility) relative to paleomagnetic reversals indicate that turbidite deposition immediately below the base of this unit ceased relatively synchronously across the transect and turbidite deposition likely occurred elsewhere on the fan. The upper bound of the unit, however, is diachronous, with the timing of the onset of turbidite deposition in this part of the fan likely related to the infilling of accommodation space on the Middle Pleistocene fan surface. Stratigraphic constraints on the resumption of turbidite deposition to transect sites include the upper Jaramillo (0.988 Ma) and Matuyama-Bruhnes (0.780 Ma) polarity boundaries and the Oldest Toba Tephra (∼0.800±0.020 Ma). The Middle Pleistocene hemipelagic layer and directly overlying turbidites were continuously sampled (u-channels) during Expedition 354. We present initial u-channel magnetic and XRF results to refine the middle to late Pleistocene shipboard magnetostratigraphy, characterize the magnetic, geochemical, and geophysical properties of Bengal Fan sediments, and discuss the implication for Pleistocene fan development and sediment accumulation rates.
Year of Publication: 2015
Research Program: IODP2 International Ocean Discovery Program
Key Words: 07 Marine Geology and Oceanography; Bengal Fan; Cenozoic; Cores; Expedition 354; Indian Ocean; International Ocean Discovery Program; Lithostratigraphy; Marine sediments; Pleistocene; Quaternary; Sediments; Upper Pleistocene
Record ID: 2016053531
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States

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