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The Study of Paloe Deltas in Western Shelf of the South Yellow Sea

Author: TaoZuoZuo
Tutor: ZhangWeiGang；LiuBaoHua
School: Ocean University of China
Course: Earth Exploration and Information Technology
Keywords: the South Yellow Sea seismic stratigraphy sea level change buried paleo delta
CLC: P736.21
Type: Master's thesis
Year: 2009
Downloads: 101
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Abstract

The Western shelf of the South Yellow Sea is enclosed by south bank of Shandong peninsula and adjacent to North plain of Jiangsu Province. It has been subsiding and receiving deposits since Cenozoic and becomes a good place on which sediment can be preserved and evolved. Because of the climate alternation since Quaternary, the study area has suffered several transgression-regression cycles. In regression period, the shelf emerged and abundant terrigenous sediment was injected and deposited. In transgression period, marine dynamics such as tide, wave, and storm eroded and migrated sediment and made the sedimentary facies and sediment distribution extremely complicated. Neotectonics activities also resulted in the discontinuity of the stratum. Because of the upper factors, the area has characters of sedimentary source diversity, sedimentary structure complication and stratum discontinuity.The high resolution shallow seismic profiles surveyed in the western shelf of the South Yellow Sea and existing QC2 core data were used to interpret and analyze the seismic sequence and its geological age. The seismic stratigraphy can be divided into 11 seismic units: early Pleistocene U1, mid-Pleistocene U2, U3, U4, U5 and U6, late Pleistocene U7, U8, U9, U10 and U11. These units have obvious sea-land alternation character, U1, U3, U5, U7, U9 and U11 are marine facies layers and U2, U4, U6, U8 and U10 are continental facies layers. Through the identification of seismic reflection and drilling contrast, the seismic facies and sedimentary facies of the various units were described.Based upon the Seismic stratigraphic division and sea-level change, the multi-phase buried paleo submerged deltas on the western South Yellow Sea shelf were studied as a key point. It has important co-relationship between deltas and sea level change. The sea level change of the study area was discussed first, and it was concluded that there are 6 regression-transgression cycles in south Yellow Sea, in every cycle, there are several sub-cycles. The identification of the delta were based on a typical reflection of bias cross foreset structure in which the foreset angle changes continuously and exists obvious down-lap and up-cut station. The delta seismic facies parameters such as amplitude, frequency, continuity provide an important basis for sediment characteristics and deposition rate of the delta. Through research, there are 6 phases paloe Changjiang submerged deltas and 4 phases paleo Huanghe or Huaihe submerged deltas. The paleo Changjiang deltas were separately formed during end of early Pleistocene, late mid-Pleistocene and late Pleistocene. Restricted by the data, the Changjiang delta boundary in end of early Pleistocene was not demarcated, it was described using previous data. The Changjiang delta in late mid-Pleistocene was only identified in very few profiles, and it could not be verified by core data. 4 Phases Changjiang deltas in late Pleistocene were obviously identified in seismic profiles and the boundaries were demarcated using seismic reflection characters. Contrasted with core data, it is defined that these deltas are all paleo Changjiang deltas which formed in regression period. The first 3 phases paleo Huanghe(Huaihe) deltas in 4 are formed in late Pleistocene, the last one has been studied in higher degree. They all distribute in west of study area, nearby the old Huanghe river port. The approximate boundaries were demarcated based on seismic facies. The first 3 phases deltas were formed in late transgression period and early regression period of oxygen isotope 3, the last one was formed in Holocene but not only in 1128-1855.The buried paleo submerged Changjiang and Huanghe(Huaihe) deltas of the Southern Yellow Sea were described in details in this paper. It provides important information for continental shelf deltas study and provides a favorable basis for the paleo-environment study and sea-level changes in the South Yellow Sea. The study has an important geological significance.

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