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Correspondence analysis and fuzzy C-means cluster methods were used to divide the stratigraphy of heavy mineral assemblages,and the sediment sources and depositional dynamics of the environment reconstructed.The assemblages were taken from marine sediments from the late Pleistocene to the Holocene in Core Q43 situated on the outer shelf of the East China Sea.Based on the variable boundaries of the mineral assemblage at 63 and 228 cmbsf (cm below sea floor),the core might have previously been divided into th... 相似文献
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Correspondence analysis and fuzzy C-means cluster methods were used to divide the stratigraphy of heavy mineral assemblages,
and the sediment sources and depositional dynamics of the environment reconstructed. The assemblages were taken from marine
sediments from the late Pleistocene to the Holocene in Core Q43 situated on the outer shelf of the East China Sea. Based on
the variable boundaries of the mineral assemblage at 63 and 228 cmbsf (cm below sea floor), the core might have previously
been divided into three sediment strata marked with units I, II and III, which would be consistent with the divided sediment
stratum of the core using minor element geochemistry. The downcore distribution of heavy minerals divided the sedimentary
sequence into three major units, which were further subdivided into four subunits. The interval between 0 and 63 cmbsf of
the core (unit I), which spans the Holocene and the uppermost late Pleistocene, is characterized by a hornblende-epidote-pyroxene
assemblage, and contains relatively a smaller amount of schistic mineral and authigenic pyrite. In comparison, the interval
between 63 and 228 cmbsf (unit II), is representative of the Last Glacial Maximum (LGM), and features a hornblende-epidote-magnetite-ilmenite
assemblage containing the highest concentrations of heavy minerals and opaque minerals. However, the interval between 228
and 309 cmbsf (unit III), which spans the subinterglacial period, is characterized by a hornblende-authigenic-pyrite-mica
assemblage. Relative ratios of some heavy minerals can be used as tracers of clastic sediment sources. The lower part of the
sediment core shows the highest magnetite/ilmenite ratio and relatively high hornblende/augite and hornblende/epidote ratios.
The middle core shows the highest hornblende/augite and hornblende/epidote ratios, and the lowest magnetite/ilmenite ratio.
The upper part exhibits a slightly higher magnetite/ilmenite ratio, and also the lowest hornblende/augite and hornblende/epidote
ratios. The distribution of the mineral ratio is consistent with stratigraphic division in heavy mineral data using correspondence
analysis and fuzzy C-means clustering. Variations in heavy mineral association and mineral ratio in core Q43 revealed changes
in provenance and depositional environment of the southern outer shelf of the East China Sea since the late Pleistocene, well
corresponding to interglacial and glacial cycles. 相似文献
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