海洋地质与第四纪地质2025，Vol.45Issue(2)：22-30,9.DOI:10.16562/j.cnki.0256-1492.2023101101
东海北部陆坡上缘沟的地形特征和成因探讨
Topography characteristics and the origination of valleys at the upper edge of continental slope in the northern East China Sea
摘要
Abstract
The upper edge of the continental slope of the East China Sea is a transitional zone between two main geomorphological units:the continental shelf of the sea and Okinawa Trough.Research into its geomorphological characteristics and origination is meaningful for better understanding the interaction between these two units,and the sea level changes during the late period of Late Pleistocene.Multibeam sounding and subbottom profile surveys revealed sea bottom valleys at the upper edge of the continental slope in the northern East China Sea.The valleys extend in NNE-SSW direction in quasi-parallel to the continental shelf break with an average distance of about 7 km.The depth of the slope break is about 150 m on average.It is also generally parallel to normal faults in the continental slope.They can be subdivided into single valleys and locally double-valleys.The later ones consist of a main west valley and an auxiliary east valley with an interval about 2km.All the valleys have a higher west slope and a lower east one,400～1600 m wide and 20～25 m deep in general.The single valleys have straight depth contours and gentle bottom topography,while the double-valleys have rather complicated topography,with minor gullies cutting down valley slopes and frequently uneven bottom and so on.Subbottom profiles across the west valley show the upper 10～15m strata having parallel reflection waves,forming an eastward-dipping structure,which is the paleo-Changjiang prodelta of the late period of Late Pleistocene.Cone penetration pest(CPT)measurements of 3m deep at 170 m depth west of the west valley are interpreted as surficial loose silty sands,and interbedded silt/clay with sands downward.Side-scan sonar images near the CPT site showed sea bottom sandwaves with amplitude about 0.5 m and wave length of 6～9 m.It is inferred that the location and layout of the valleys were affected by normal faults in the continental slope related to the third phase of the Okinawa Trough expansion.Taking into account the shell 14C dating of nearby borehole samples and sea level change curves,the valleys were formed mainly during 17.4～14.5 kaBP,which is the early stage of sea level rising after the last glacial maximum(LGM),when the area was in offshore-shallow sea environment and underwent tidal current scouring.Therefore,these valleys are fault-scouring valleys.The complicated topography of the double-valleys was related to submarine landslides of paleo-Changjiang predelta deposits.The measured 200 m depth contour lines of sea bottom are mostly within the west valley but partly to the east of the valley,resulting in the intersection of each other;and their similar stretching directions were considered to be resulted from the regional tectonic framework.关键词
陆坡/断裂冲沟/正断层/古长江三角洲/东海北部Key words
continental slope/fault-scouring valleys/normal faults/paleo-Changjiang delta/the northern East China Sea分类
海洋学引用本文复制引用
刘阿成,郭伟其,陈新玺,张杰,唐建忠,李嘉柠,秦威..东海北部陆坡上缘沟的地形特征和成因探讨[J].海洋地质与第四纪地质,2025,45(2):22-30,9.基金项目
华能集团总部科技项目"基于深远海的海上风电选址和支撑技术研究"(HNKJ20-H66) （HNKJ20-H66）
