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| Titel |
A magnetic and geochemical record of centennial mid-Holocene fluvial-marine interaction at the apex of the Yangtze River delta |
| VerfasserIn |
Weiguo Zhang, Leiping Ye, Zhen Li, Bing Song, Qianli Sun, Lizhong Yu |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250096860
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| Publikation (Nr.) |
 EGU/EGU2014-16320.pdf |
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| Zusammenfassung |
| Magnetic properties, particle size and geochemical determinations were carried out on a
53.58 m long core of mid-Holocene age drilled at the apex of the Yangtze River delta. Based
on these analyses, core JD01 has been divided into seven units. Magnetic properties and
major elements geochemistry indicate that the whole core has a similar sediment provenance.
Magnetic mineral concentrations are positively correlated with the >125 μm fraction, while
reductive diagenesis of ferrimagnetic mineral is more marked in fine-grained sediments.
Total organic carbon (TOC), total nitrogen (TN) and their ratio (C/N) and stable
carbon isotope (δ13C) measurements suggest that the sedimentary environment
changed from marine dominated to terrestrial dominated at around 34 m, dated
to ca. 6200 cal. yr BP. Diagenesis of magnetic minerals, characterized by lower
magnetic S-ratios and lower ferrimagnetic mineral concentrations, is evident in marine
facies unit 3 (U3) and delta plain facies unit 7 (U7), The basal part of delta front
sediments are characterized by higher TOC concentrations with significant terrestrial
organic matter input. This sedimentary layer lasts from ca. 6200 to 5500 cal. yr BP,
corresponding to a period of warmer and wetter East Asian monsoon climate. It is
suggested that strengthened precipitation led to stronger fluvial sediment discharge to
the delta region. In addition, dramatic fluctuation in organic matter sources is also
evident during this period, indicating centennial-scale climate instability during the
mid-Holocene. The δ13C and chemical weathering index (CIA) values also suggest a general
weankening of the Asian summer monsoon from 6200 to 5700 yr. BP. This study
suggests that delta deposits with rapid sedimentation are potentially capable of
providing high-resolution paleoenvironmental information for parts of the Holocene |
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