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Posted by / 01-Oct-2019 12:06

Magneticdating com

With the application of clay minerals, geochemistry, and heavy mineral analyses, researchers have documented different sedimentary environments during the Pliocene to Pleistocene transition [26,27].

Heavy mineral analysis evinces the presence of high contents of zircon and extremely low contents of amphibole (5%) in Pliocene sediments of the Changjiang Delta, which is related to strong chemical weathering or diagenesis during this time (Figure 1).

The different chemical weathering and sedimentary conditions at the Pliocene to Quaternary transition make the Changjiang Delta an ideal location to document the physical and geochemical response of single minerals to different sedimentary environments [23,27].

In this study, unstable (amphibole, epidote) and stable (tourmaline) heavy mineral in grain size fractions of 32–63 µm and 63–125 µm were analyzed by using a scanning electron microscope (SEM) and an electron probe (EP).

However, there are only a few studies that deal with the relationship between the physical and chemical parameters of single heavy minerals and address these significant research lacunae: (i) How do different minerals respond to different sedimentary environments in the deltaic area?

Chemical analysis on single-grain minerals (e.g., zircon, tourmaline, apatite, rutile, monazite, amphibole, and garnet) has promoted the study of sediment source to sink [19,20,21].The pre-dam (Three Gorges Dam) sediment yield of the Changjiang River was tons [4].The reconstruction of the source and distribution patterns of the delta sediments can help to unravel the history of erosion processes, source area characteristics, and the factors controlling and determining the production (source), transport, dispersal and accumulation (sink), and reworking (number of burial-erosion cycles during sediment transport) at different temporal and spatial scales [5,6,7].There were many calcareous and iron-manganese nodules (Figure 2).Moreover, a block of grey calcareous sand was found in the bottom strata (Figure 2).

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The Quaternary strata comprised several sedimentary sequences, which were composed of sand at the bottom and clayey silt at the top, suggesting a fluvial environment (Figure 2).

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