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Supplementary investigation and assessment of environmental ...

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  • 1. Development of stratigraphy and geo-hazards in the offshore area of the Yellow River delta duing the late Quaternary Jian LIU1, Yoshiki Saito2, Hongwang1 1QingdaoInstitute of Marine Geology, CGS, Qingdao, 266071, China 2Coastal Environmental Research Group, MRE, Geological Survey of Japan, AIST, Tsukuba, Ibaraki, 305-8567, Japan January 19, 2004
  • 2. Outline Introduction Methods Late-Quaternary stratigraphy Geo-hazards in the subaqueous YRD
  • 3. Schematic map of the bathymetry and regional circulation pattern in the Yellow Sea and adjacent areas during wintertime (modified after Su, 1986, and Guan, 1983).
  • 4. The Bohai Basin belongs to the North China platform; A cratonic fault-bounded basin of Mesozoic-Cenozoic age; During the Mesozoic, NE- trending rifts formed and filled with 1000-1500 m of sediment; During the Cenozoic, the Bohai Basin was formed and was connected with the North China Basin inland.
  • 5. 10 delta superlobes in the delta plain (1) 6000-5000 a BP; (2) 5000-4500 a BP; (3) 4500-3400 a BP; (4) 3400-3000 a BP; (5) 3000 a BP-602 BC; (6) 602 BC-AD 11; (7) AD 11-1048; (8) 1048-1128; (9) 1128-1855; (10)1855-present. (Saito et al., 2000)
  • 6. (Xue, 1993)
  • 7. The overall modern Yellow River delta is composed of juxtaposed and imbricated deltaic lobes (Xue, 2003).
  • 8. Methods 1. Application of remote sensing technology in studying of environmental geology in the area; 2. Shallow seismic profiling and coring: investigation of late Quaternary stratigraphy in the shallow-water area; 3. Mapping of geological hazards.
  • 9. Coastal evolution of the Yellow River Delta during the last 25 Coastline in 1976 Coatline in 2001
  • 10. Changes of offshore bathymetry 38¡ã 30¡ä 1976 38¡ã 15¡ä 1984 2001 38¡ã 00¡ä 37¡ã 45¡ä Yellow River Delta 1976 data:Yellow River Conservancy commission 1984 data: from Z. 37¡ã 30¡ä Wang(1988) 118¡ã 30¡ä 118¡ã 45¡ä 119¡ã 00¡ä 119¡ã 15¡ä 119¡ã 30¡ä 119¡ã 45¡ä 120¡ã 00¡ä
  • 11. Surface sediment distribution in the Modern Yellow River Delta
  • 12. Geomorphologic map of the modern Yellow River Delta
  • 13. Investigation of late Quaternary Stratigraphic framework One core as long as 61 m was retrieved; Seismic profiles of about 700 km were measured.
  • 14. H3 H 1 Core HB-1 Distribution of shallow seismic profiles and core HB-1
  • 15. Survey equipment Vessels: Jiwenyu 4003 & Luheyu 2069 High-resolution seismic profiles were obtained using 300-500J CSP 1500 sparker, with vertical resolution of 0.5-1 m. Penetration of 150 ms two-way travel time Device measuring the offshore bathymetry: SDH-13D
  • 16. Sea-level changes during deep sea oxygen isotope stages (OIS) 1-6
  • 17. AMS14C dates: 0 26 52 Delta Sedimentary sequence 1 27 53 front 2 3 28 29 River 54 55 Delta of Core HB-1 4.66 m: 240 a; 4 30 56 plain Yellow River delta (since 1855) 5 31 57 14.23 m: 830 a; 6 7 32 33 58 59 Delta front 0~13.97 m: Deposits of the 8 34 60 Yellow River Delta Delta plain 17.1 m: 4330 a; 9 35 61 Silty clay Middle sand Fine sand since 1855; 10 36 62 Silt 11 37 Clayey silt 13.97~17.2 m: Shelf 19.32 m: 6480 a; 12 38 Lengend Wavy lamination deposits; 13 39 Flaser bedding Depth (m) 14 40 Lenticular bedding Deformation bedding 23.08 m: 11380 a; 15 Shelf 41 Clayey banding Silty lamination Cross bedding 17.2~20.70 m: Deposits of 16 42 17 43 Brown oxidation surface Scouring / erosional surface tidal flat to salty Silt/fine sand banding 26.98 m: 14190 a; 18 Tidal flat 44 Burrow Strong bioturbation marsh; 19 45 Middle bioturbation Delta front Salt mash Gastropods 20 46 Mullusk shell 38.75 m: 43640 a; 21 47 Mud pebble Carbonaceous spots 20.70~29.60 m: Fluvial 22 23 48 49 Carbonaceous fragments Brown rusty stain Calcium-containing concretion deposits; River Carbonaceous silty clay 53.44 m: 38470 a; 24 50 Peat layer 25 26 51 52 29.60~61. 01 m: Tidal flat to 60.82 m: 41330 a. 27 Silty clay Middle sand Fine sand Silt Clayey silt 53 Silty clay Middle sand Fine sand Silt Clayey silt littoral-shallow sea deposits.
  • 18. Abundances of Simple diversity Abundances of Simple diversity of foraminifers of ostracods foraminifers ostracods
  • 19. Yellow mud-flaser- Intercalated sand, interbedding of 0~13.97 m: muddy bands and Deposits of the sand, no Yellow River bioturbation. Delta since 1855; Grey silt-clayey silt, interbedding of silt and mud, bioturbation . 13.97~17.21 m: Shelf deposits Peaty layers, muddy pebbles, 17.21~20.79 m: Deposits of tidal flat to salty marsh
  • 20. 20.79~29.66 m: Fluvial deposits
  • 21. 29.66~40.45 m: Deposits of tidal flat to coastal marsh
  • 22. 40.45~53.87 m: Deposits of littoral area to Shallow sea Depth (m) 53.87~60.82 m: Deposits of tidal flat to littoral area
  • 23. Abunndance of euryhaline and brackish water species Percentage of euryhaline and brackish water species
  • 24. Core HB-1 U1 U2 U4 U3 U5 U6 U7
  • 25. U1 U3 U2 U4 U5
  • 26. U1 U2 U1 U3 U4 U5 U7 U6
  • 27. Sea-level reconstruction for OIS 3 from uplifted coral reefs at Huon Peninsula (from Lambeck et al., 2000)
  • 28. Delta deposit P-G LGM OIS-3 OIS-4 OIS-5 Late Quaternary stratigraphic framework in the subaqueous area
  • 29. Distribution of sediment thickness of the Yellow River Delta in the subaqueous part
  • 30. The Holocene sediment thickness of the delta in the subaqueous area
  • 31. The OIS-2 sediment thickness of the delta in the subaqueous area
  • 32. Seismic profile H7&H10 Delta Front Slope collapse collapse
  • 33. Burried channel, shallow gas&diapir
  • 34. Seismic profile H7 The rise and faults
  • 35. Diapir Diapirism in the subaqueous abandoned delta is closely related to seabed erosion and results from the deformation of soft, fine-grained prodelta sedimentary stratum.(Li et al.,2000)
  • 36. Bathymetric profile: Active delta lobe Line H5 normal to delta front Line H7 normal to delta front collapse
  • 37. Bathymetric profile : Abandoned delta lobe Line H3 normal to delta front Irregular Sea Floor Line H8 parallel to delta front Gully
  • 38. Subaqueous slide on the YRD After Z. S. Yang et al. (1994)
  • 39. Geo-hazard map
  • 40. Conclusion on the geo-hazards Four types of coastline erosion were distinguished, including: rapid erosion, moderate erosion, no detectable erosion, and accretion. geo-hazards were found: coast erosion, diapir, shallow gas, seabed stability, faults, seabed morphology. The resultant map of geo-environment and geo-hazards presents the coastline change and distribution of geo- hazards in the Yellow River Delta The rise outside of the modern river mouth is a new evidence for the seabed mass-movement
  • 41. Thank You!

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