Magnetic Susceptibility Application: A Window onto Ancient Environments and Climatic Variations
Magnetic susceptibility (MS) is a tool frequently used by geologists on sediments or rocks to perform correlations and sea-level or climatic reconstructions. Applied measurements are made on unoriented, bulk samples and bulk MS is mostly influenced by the magnetic mineral content of the rock and often interpreted as influenced by detrital inputs. Magnetic data acquisition is fast and straightforward and this allows the high-resolution sampling needed for palaeoclimatic research (e.g. spectral analysis). However, the link with detrital inputs is not always preserved and the impact of diagenesis on the final MS signal can blur primary information. This volume includes contributions dealing with the origin of the magnetic minerals, and the application of MS as a palaeoenvironmental or palaeoclimatic proxy and also as a tool to provide astronomical calibration in order to improve the chronology of selected time intervals.
Sedimentology and magnetic susceptibility of recent sediments from New Caledonia
-
Published:January 01, 2015
-
CiteCitation
Hélène Jadot, Frédéric Boulvain, 2015. "Sedimentology and magnetic susceptibility of recent sediments from New Caledonia", Magnetic Susceptibility Application: A Window onto Ancient Environments and Climatic Variations, A. C. Da Silva, M. T. Whalen, J. Hladil, L. Chadimova, D. Chen, S. Spassov, F. Boulvain, X. Devleeschouwer
Download citation file:
- Share
Abstract
The interpretation of the primary origin of the minerals carrying the magnetic susceptibility (MS) signal from ancient rocks suffers notably from the scarcity of studies on Recent sediments. To bring new data, a study of tropical coastal sediments of New Caledonia was undertaken. This island is surrounded by a nearly uninterrupted reef barrier, isolating a wide lagoon from the open ocean. The erosion of extremely varied rocks (from mantle rocks to laterites) produces different types of detrital sediments, which are mixed with the indigenous precipitated carbonates. This generates different types of coastal sediments, detrital- or carbonate-dominated or mixed. More than 300 samples were analysed for grain size, nature of sediment, MS and geochemistry (major elements). The first results show that: (a) carbonate sands and carbonate silts are characterized by lower MS than detrital sediments; (b) the MS signal of mixed sediments is mostly influenced by the proportion of detrital sediments; (c) MS is directly correlated with Mn and Fe content; (d) beachrocks are characterized by lower MS than equivalent loose sediment; (e) the MS signal of carbonate sediments is locally positively correlated with granulometry; (f) there is no MS change between surface and 20 cm deep samples; and (g) when the subsurface sediment is reducing, the MS is higher than that from surface sediment.