Magnetic signatures of Heinrich-like detrital layers in the Quaternary of the North Atlantic

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doi: 10.1016/j.epsl.2013.03.034
Author(s): Channell, J. E. T.; Hodell, D. A.
Author Affiliation(s): Primary:
University of Florida, Department of Geological Sciences, Gainesville, FL, United States
Other:
University of Cambridge, United Kingdom
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, Vol.369-370, p.260-270. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. 51 refs.; illus., incl. sketch map
Summary: Magnetic parameters are useful for distinguishing North Atlantic Heinrich-like detrital layers from background sediments. Here we compare magnetic properties with XRF scanning data back to 700ka and 1.3 Ma at IODP Sites U1302-U1303 and U1308, respectively. Multi-domain magnetite, with grain sizes >20 µm, is characteristic of both Ca- and Si-rich detrital layers, as defined by XRF core scanning, confirming the contribution of ice rafting. Reflectance spectra and magnetic parameters distinguish Ca- and Si-rich IRD layers due the presence of high coercivity hematite in Si-rich layers. Heinrich layer 6 (H6) at Site U1302-U1303 is unlike other detrital layers, being marked by a 45-cm thick homogeneous cream-colored clay layer underlain by a thin (5-cm) graded coarse-sand. Comparison of Site U1302/03 and Site U1308 detrital layers implies a dominant Laurentide source for both Ca- and Si-rich detrital layers. At Site U1308, low benthic δ13C values during stadials are in-step with magnetic grain-size coarsening associated with Si-rich detrital layers back to 1.3 Ma, indicating a link between deep-sea ventilation and ice rafting. The surface-sediment tan-colored oxic layer (∼2m thick at Site U1308) yields magnetic hysteresis ratios that are offset from the single-domain to multi-domain (SD-MD) magnetite mixing-line in hysteresis-ratio diagrams. This offset is attributed to maghemite grain-coatings, that form on magnetite in surface sediment, and undergo dissolution as they pass through the oxic/anoxic boundary. Abstract Copyright (2013) Elsevier, B.V.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Atlantic Ocean; Benthic environment; C-13/C-12; Carbon; Carbonates; Cenozoic; Coercivity; Detritus; Expedition 303; Expeditions 303/306; Grain size; Heinrich events; Hematite; IODP Site U1302; IODP Site U1303; IODP Site U1308; Ice rafting; Integrated Ocean Drilling Program; Isotope ratios; Isotopes; Magnetic domains; Magnetic hysteresis; Magnetic properties; Magnetite; Marine sediments; Mid-Atlantic Ridge; Multidomains; North Atlantic; Northeast Atlantic; Northwest Atlantic; Oxides; Paleomagnetism; Quaternary; Reflectance; Sediments; Single domains; Spectra; Stable isotopes; Ventilation; X-ray fluorescence spectra
Coordinates: N501000 N501000 W0453800 W0453800
N501200 N501200 W0454100 W0454100
N495300 N495300 W0241400 W0241400
Record ID: 2013070469
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands