Titre

The rock magnetic signal of climate change in the maar lake sequence of Lac St Front (France)

Année de publication

1997

Source

Geophysical Journal International 131 724 740 3

ISSN
0956-540X
Résumé

Rock magnetic properties of the maar lake sediments of Lac St Front (Massif Central, France) reflect environmental changes during the last climatic cycle. High magnetic concentrations are measured in the sediments deposited under glacial climatic conditions, while lower concentrations correspond with more temperate climatic periods. Low- and high-temperature measurements indicate that the remanence is carried by (titanium-poor) magnetite. However, some maghemite and haematite is present in sediments deposited under temperate conditions. Normalized intensities and coercivities of the anhysteretic remanent magnetization (ARM) are clearly higher for the sediments deposited during the temperate climatic periods of the Eemian, St Germain I, II and Mid-glacial than for glacial sediments, but other magnetic parameters hardly differ between these groups. Due to slight differences in magnetic composition and possible effects of grain interactions, it is not straightforward to relate this different ARM behaviour to magnetic grain-size variations. For the Holocene sediments, rock magnetic parameters indicate a larger grain size. This trend is also suggested by granulometric experiments with an optical laser granulometer. Dissolution of smaller grains is the most likely explanation for this larger grain size. Changes in magnetic composition and grain size are extremely limited for the glacial sediments, but magnetic concentration varies considerably. Magnetic concentration maxima in the glacial sediments of Lac St Front correlate with those of the nearby Lac du Bouchet (Thouveny et al. 1994). Correlating the susceptibility records of these sequences with the δ18O record of the GRIP ice cores (Thouveny et al. 1994) suggests that magnetic concentration maxima may correspond with short cold climatic episodes, associated with Heinrich events.

Type de publication
  • journal
Type de document
  • research-article
Classification
 
Classification - Inist-CNRS
  • sciences appliquees, technologies et medecines
  • sciences exactes et technologie
  • terre, ocean, espace
  • geophysique externe
Classification - Scopus
  • 1 - Physical Sciences
  • 2 - Earth and Planetary Sciences
  • 3 - Geochemistry and Petrology
  • 3 - Geophysics
Classification - Science Metrix
  • natural sciences
  • earth & environmental sciences
  • geochemistry & geophysics
Classification - Clarivate Analytics (Subject Category)
  • science
  • geochemistry & geophysics
Entité nommée
 
Entité nommée - Emplacement géographique
  • Minneapolis
  • Utrecht
  • St.Gerrnain
  • St Germain
  • France
  • Marseille
  • MN
  • St. Gerrnain
  • NETHERLANDS
Entité nommée - Organisme
  • Keck Foundation, the NSF
  • Geologie du Quaternaire
  • IRM
  • University of Minnesota
  • Shepherd Laboratories
  • Institute for Rock Magnetism
  • ENVIRONMENTAL SIGNAL
  • DYTEC
Entité nommée - Personne
Astrid VilgC; Hc; Rock Magnetism; D. Williamson; V. Andrieu; A. J. van Velzen; N. Thouveny
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