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Contribution of Rock magnetism to Stratigraphy and Palaeoenvironment of the Karaïn cave infill, Antalya, Turkey

Abstract : The magnetic properties of the infill of the Karaïn cave in Turkey were compared to the results of a sedimentological study on three longitudinal sections. The sediments of this site, namely cavity E, cover a period of ca. 500 ka and correspond to a large part of the Middle and Upper Pleistocene. The evolution observed for the various magnetic parameters is mainly related to climatic changes which followed one another during the infilling history of the cave. Two preconditions are necessary to understand the environmental magnetism, namely both the identification and the quantification of different magnetic phases (components) in the sediments, expressed by the ratio of the various magnetic parameters and the analysis of the magnetization curves. The results obtained through the study of the different magnetic parameters (low-field initial bulk (..lf) and mass ( lf) magnetic susceptibility, frequency dependence of the magnetic susceptibility ( fd), anhysteretic remanent magnetization (ARM), hysteresis parameters, anhysteretic susceptibility, ...) on 171 samples allowed us: 1 - to follow the nature, size and source of the grains at each level, and 2 - to identify six alternating levels, having different magnetic susceptibility signatures during warm, damp periods, in which the contribution of prehistorical hominidae (Homo Sapiens or Homo Neandertalensis) and animals, could have modified the original sedimentary structures. This study, in agreement with the sedimentological results, suggests a significant difference between sandy or sandy-silty levels (3 and 5) and those rich in clays and concretions. The sandy or sandy-silty levels are mainly characterized by a low amount of antiferromagnetic type grains, likely goethite and hematite, dominated by single-domain size (SD) and a small content of ferrimagnetic type grains, likely magnetite of multidomain size (MD), inherited from the host rock. Antiferromagnetic grains did not develop and were a priori drifted by the wind. They could be contemporaneous with a cold climate. The clays and clayey-silty levels are characterized by a large amount of superparamagnetic (SP) and SD grains, and a high content of low coercivity magnetic grains (magnetite, maghemite and Ti-magnetite). The saturation remanent magnetization (SIRM) of clayey levels is 5 to 10 times higher than that of sandy levels. The clayey levels are contemporaneous with a humid climate, which favoured the formation of secondary iron oxides, of stalagmitic floors and calcite concretions and of the emplacement of local pedogenesis phenomena, mainly at the top of the infill, i.e. in Level 6.
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Submitted on : Friday, March 18, 2011 - 11:17:29 AM
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Abderrezak Djerrab, Tahar Aifa. Contribution of Rock magnetism to Stratigraphy and Palaeoenvironment of the Karaïn cave infill, Antalya, Turkey. Studia Geophysica et Geodaetica, Springer Verlag (Germany), 2010, 54, pp.49-76. ⟨insu-00578053⟩

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