陈芳, 周洋, 庄畅, 陆红锋, 吴聪. 南海东北部冷泉区末次冰期沉积间断及其成因[J]. 海洋地质与第四纪地质, 2016, 36(2): 19-27. DOI: 10.16562/j.cnki.0256-1492.2016.02.003
引用本文: 陈芳, 周洋, 庄畅, 陆红锋, 吴聪. 南海东北部冷泉区末次冰期沉积间断及其成因[J]. 海洋地质与第四纪地质, 2016, 36(2): 19-27. DOI: 10.16562/j.cnki.0256-1492.2016.02.003
CHEN Fang, ZHOU Yang, ZHUANG Chang, LU Hongfeng, WU Cong. ORIGIN OF THE HIATUS OF LAST GLACIAL PERIOD IN COLD SEEP AREA of NORTHEASTERN SOUTH CHINA SEA[J]. Marine Geology & Quaternary Geology, 2016, 36(2): 19-27. DOI: 10.16562/j.cnki.0256-1492.2016.02.003
Citation: CHEN Fang, ZHOU Yang, ZHUANG Chang, LU Hongfeng, WU Cong. ORIGIN OF THE HIATUS OF LAST GLACIAL PERIOD IN COLD SEEP AREA of NORTHEASTERN SOUTH CHINA SEA[J]. Marine Geology & Quaternary Geology, 2016, 36(2): 19-27. DOI: 10.16562/j.cnki.0256-1492.2016.02.003

南海东北部冷泉区末次冰期沉积间断及其成因

ORIGIN OF THE HIATUS OF LAST GLACIAL PERIOD IN COLD SEEP AREA of NORTHEASTERN SOUTH CHINA SEA

  • 摘要: 对南海东沙海域冷泉区DH-CL10和DH-CL5柱状样开展AMS14C年代学、高分辨率底栖有孔虫和沉积物同位素以及沉积学研究。结果表明:DH-CL10柱状样在全新统底部574 cm处出现沉积间断,间断面相邻沉积物AMS14C年龄分别为9 850/(9 680~9 950) cal.aBP和27 610/(27 500~27 700) cal.aBP,相当于MIS2期和部分MIS3期的沉积缺失。底栖有孔虫Uvigerina bifurcataδ13C值为-0.37‰~-1.91‰,平均值为-1.11‰,沉积物全岩碳同位素值为-22.7‰~-23‰,均为正常的碳同位素值。尽管该柱状样未发现天然气水合物分解释放的地球化学证据,但相邻的DH-CL5柱状样相当于其所缺失的部分沉积中的自生碳酸盐岩和沉积物的δ13C负偏明显,分别为-55.24‰和-25.9‰~-27.9‰,表明与天然气水合物分解有关。推断DH-CL10柱状样沉积间断所缺失的沉积物可能记录了天然气水合物分解的证据,且沉积间断主要出现在末次盛冰期低海平面,与天然气水合物易分解的时间相吻合,因此,沉积间断的形成可能主要与下伏天然气水合物的分解导致沉积物的滑塌有关。

     

    Abstract: With the purpose to search for sedimentary evidence of gas hydrate dissociation, a thorough research on AMS14C chronology, high-resolution (2 cm sampling interval) carbon and oxygen stable isotope of benthic foraminifera and authigenic carbonate and sediment, as well as sedimentological studies has been accomplished for the core DH-CL10 and DH-CL5 located at the Dongsha cold seep area of the South China Sea. The analytical results show that a sedimentary hiatus occurs at the core depth of ~574 cm, the bottom of the Holocene. The AMS14C ages of the sediments above and below are 9 850 (9 680 to 9 950) cal.aBP and 27 610 (27 500 to 27 700) cal.aBP, respectively. The δ13C values of benthic foraminifera Uvigerina bifurcata vary from -0.37‰ to -1.91‰ with -1.11‰ on average, while the δ13C values of bulk samples range from -22.7‰ to -23.0‰, both within the normal range of variation. Although we do not find any geochemical evidence for dissociation and release of gas hydrate in the core DH-CL10, the authigenic carbonate and sediment from the neighbor site DH-CL5 reveal remarkable δ13C negative excursions, -55.24‰ and -25.9‰ to -27.9‰ in bulk respectively, suggesting the distinct influence of gas hydrate. The sedimentary hiatus occurred in the sea-level lowstand period of the Last Glacial Maximum, which was consistent with the time when gas hydrate tended to dissociate. Therefore, it can be concluded that the sedimentary hiatus was predominantly related to the sediment slump induced by the dissociation and release of the underlying gas hydrate.

     

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