Deguo Chiemsee Hu ci xing xi jun gan hu ni de ci xue xing zhi

In this paper,we measured the magnetic parameters,grain size and XRD for four dry mud samples,which were taken from Lake Chiemsee, Bavaria of Germany. The Lake Chiemsee （47°54＇N, 12°30＇E ; 520m above sea level） located in the piedmont of Alps,covers about 80kin2. After collected by piston cores, the samples had experienced the magnetotactic bacteria culture in laboratory, then were air-dried and divided into four parts （various depths） which were named Bio-tesl, Bio-lcs2, Bio-lcs3, Bio-lcs4. The results of the experiments show that the main magnetic minerals in the samples are magnetite, and a few pyrite simultaneously exist. Compared with other samples, the sample cultured at 1 - 2cm depth displays some different properties in magnetic susceptibility （Z） , percentage frequency magnetic susceptibility （ Zfd% , anhysteretic remanent magnetization （ ARM ） , saturation magnetization （M） and eoercivity（ H o） , likely indicating higher concentration of magnetosomes produced by more magnetotactie bacteria in such certain depth. The results of low-temperature saturation remanence show clear Verwey transition, suggesting presence of multi-domain （MD） magnetite in the samples. That coarse size is out range of reported magnetosomes. That was also detected by particle size measurements showing a few peaks for the distribution curves. Of which,two main peaks are all larger than that of single domain SD/MD boundary. That likely indicates that lake Chiemsee sediments may be a mixture sources, together with aeolian deposit down to the lake. Some coarser sands and aeolian deposit around the lake would be possibly washed down to the lake by surface water flow. The multi-domain magnetite measured in the samples could be within these coarser sediments.