Magnetic properties of two cores from the Iberian Margin


Autoria(s): Channell, James ET; Hodell, David A; Margari, Vasiliki; Skinner, Luke C; Tzedakis, Polychronis C; Kesler, M S
Cobertura

MEDIAN LATITUDE: 37.723000 * MEDIAN LONGITUDE: -10.155000 * SOUTH-BOUND LATITUDE: 37.565000 * WEST-BOUND LONGITUDE: -10.176000 * NORTH-BOUND LATITUDE: 37.881000 * EAST-BOUND LONGITUDE: -10.134000

Data(s)

21/05/2013

Resumo

Magnetic properties of late Quaternary sediments on the SW Iberian Margin are dominated by bacterial magnetite, observed by transmission electron microscopy (TEM), with contributions from detrital titanomagnetite and hematite. Reactive hematite from eolian dust, together with low organic matter concentrations and the lack of sulfate reduction, lead to dissimilatory iron reduction and availability of Fe(II) for abundant magnetotactic bacteria. Magnetite grain-size proxies (kARM/k and ARM/IRM) and S-ratios (sensitive to hematite) vary on stadial/interstadial timescales, contain orbital power, and mimic planktic d18O. The detrital/biogenic magnetite ratio and hematite concentration are greater during stadials and glacial isotopic stages, reflecting increased detrital (magnetite) input during times of lowered sea level, coinciding with atmospheric conditions favoring hematitic dust supply. Magnetic susceptibility, on the other hand, has a very different response being sensitive to coarse detrital multidomain (MD) magnetite associated with ice-rafted debris (IRD). High susceptibility and/or magnetic grain size coarsening, mark Heinrich stadials (HS), particularly HS2, HS3, HS4, HS5, HS6 and HS7, as well as older Heinrich-like detrital layers, indicating the sensitivity of this region to fluctuations in the position of the polar front. Relative paleointensity (RPI) records have well-constrained age models based on planktic d18O correlation to ice-core chronologies, however, they differ from reference records (e.g. PISO) particularly in the vicinity of glacial maxima, mainly due to inefficient normalization of RPI records in intervals of enhanced detrital/eolian hematite input.

Formato

application/zip, 2 datasets

Identificador

https://doi.pangaea.de/10.1594/PANGAEA.811826

doi:10.1594/PANGAEA.811826

Idioma(s)

en

Publicador

PANGAEA

Direitos

CC-BY: Creative Commons Attribution 3.0 Unported

Access constraints: unrestricted

Fonte

Supplement to: Channell, James ET; Hodell, David A; Margari, Vasiliki; Skinner, Luke C; Tzedakis, Polychronis C; Kesler, M S (2013): Biogenic magnetite, detrital hematite, and relative paleointensity in Quaternary sediments from the Southwest Iberian Margin. Earth and Planetary Science Letters, 376, 99-109, doi:10.1016/j.epsl.2013.06.026

Palavras-Chave #Abs; Absolute; Decl (NRM); Depth; DEPTH, sediment/rock; Incl (NRM); MAD; Maximum angular deviation; N/A; N/AQ; N/I30; N/I95; NRM, Declination; NRM, Inclination; R-value; Slope
Tipo

Dataset