tailieunhanh - International Perspectives on Global Environmental Change Part 6

Tham khảo tài liệu 'international perspectives on global environmental change part 6', khoa học tự nhiên, công nghệ sinh học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Continental Erosion Weathering Changes in Central Asia Recorded in the Holocene Sediment from Lake Hovsgol Northwest Mongolia by Synchrotron p-XRF Mapping Analyses 139 2. Materials and analytical methods Core HDP-06 In the present study we used core HDP-06 which was collected at the base of the southeast slope of Lake Hovsgol in northwest Mongolia Fig. 1 . The HDP-06 core drilling took place in March 2006 at 50 54 25 N 100 27 03 E at a water depth of m using an improvised push-coring type technology Hovsgol Drilling Project Members 2009 . Core HDP-06 was about 26 m long and the sediment recovery was on the order of 80 . In the present study we analyzed the upper section about 18 cm of HDP-06 core 1-1 about 140 cm which was undisturbed and fully recovered. The lithologic observation revealed that the core 1-1 bears sedimentary layers distinctive of Hovsgol s sediment which is composed of diatomaceous clayey ooze in the Holocene section and calcareous clayey silt to silty clay in the last glacial section Prokopenko et al. 2005 . Sample preparations In order to acquire two-dimensional XRF images of the sediment surface by the SR p-XRF techniques we prepared thin sections of the resin-embedded samples. Subsamplings from an open core surface were carried out using aluminum U-channels Fig. 2 . After carefully retrieving the sediment slab from the U-channel the slabs were impregnated with epoxy resin following the procedure of Tiljander et al. 2002 . The U-channels were produced from a aluminum sheet using a sheet bender Fig. 2a which we produced ourselves. A resin-embedded sediment block was shaped to a thickness of mm for SR p-XRF mapping. This was done to reduce the X-ray scattering from the inside of the sample. First a pair of sediment slabs Fig. 3a was separated with a band saw because several sediment slabs were embedded together with the epoxy resin. Each sediment slab was cut into three pieces to produce approximately 5 cm X 5 cm .