220 ka以来西菲律宾海黏土矿物输入变化及其控制因素

Variation in clay mineral input and the control factors in the Western Philippine Sea since 220 ka

  • 摘要: 为揭示晚更新世以来西太平洋暖池黏土矿物输入变化的控制因素,对采自西菲律宾海本哈姆隆起上的Ph05-5孔沉积物中的黏土矿物组成、来源和堆积速率进行了分析。结果表明,220 ka以来,该孔沉积物中的黏土矿物主要以伊利石(13%)和蒙皂石(8%)为主,其次为绿泥石(6%)和高岭石(2%)。伊利石和绿泥石主要来源于亚洲大陆,蒙皂石主要源于菲律宾海周围岛屿的火山物质在海底遭受海水侵蚀后形成的自生Fe-蒙皂石和西菲律宾海周围岛屿上的物质风化后形成的他生Al-蒙皂石。220 ka以来,伊利石和绿泥石的堆积速率表现出明显的冰期高-间冰期低的旋回变化,与该孔总的风尘堆积速率、亚洲风尘和北太平洋风尘堆积速率一致。冰期/间冰期太阳辐射降低/增强、亚洲内陆干旱程度加强/减弱,是导致伊利石等源于亚洲内陆的黏土矿物向菲律宾海输入增加/减少的主控因素。Ph05-5孔蒙皂石的堆积速率同样表现出明显的冰期高-间冰期低的特征,与该孔总的火山物质堆积速率一致。蒙皂石在轨道尺度的变化,主要受到海平面变化和热带类ENSO过程影响的降雨过程控制。冰期低海平面,菲律宾岛和海水的混合作用加强,使得蒙皂石的输入增加。此外,冰期在热带太平洋类拉尼娜较强,降雨量增加,导致向菲律宾海输入的火山物质(蒙皂石)增加,间冰期则相反,由于类厄尔尼诺增强,菲律宾岛区域干旱,火山物质(蒙皂石)向菲律宾海的输入减少。

     

    Abstract: To reveal the controlling factors of clay minerals input in the Western Pacific Warm Pool since the Late Pleistocene, we analyzed the composition, source, and mass accumulation rates (MARs) of clay minerals in the sediment from Core Ph05-5 recovered from the Benham Rise in the Western Philippine Sea. The results indicate that the clay minerals in the core sediment are mainly composed of illite (13%) and smectite (8%), followed by chlorite (6%) and kaolinite (2%). Over the last 220 ka, illite and chlorite are derived mainly from the Asian continent, and smectite is mainly authigenic Fe-smectite in volcanic origin from islands around the Philippine Sea after erosion by seawater at the seabed, and smectite formed by weathering of volcanic material from islands around the West Philippine Sea. The MARs of illite and chlorite displayed significant high value during the glacial period and low value during the interglacial period, which is consistent with the total MARs of eolian dust of Core Ph05-5, MARs of Asian dust and North Pacific dust over the last 220 ka. The decrease/enhancement of solar radiation during the glacial/interglacial period, as well as the strengthening/weakening of arid in Asian continent are the main controlling factors for the increase/decrease in the input of clay minerals, such as illite from Asian continent into the Philippine Sea. The MARs of smectite in Core Ph05-5 also exhibits high value during the glacial period and low value during interglacial period, which is consistent with the total MARs of the volcanic material in Core Ph05-5. The changes of smectite in the orbital scale are mainly controlled by global sea level change and precipitation influenced by tropical ENSO processes. The low sea level during the glacial period resulted in the strengthened mixing effect between the Philippine Island and seawater, and led to an increase of smectite input in the Philippine Sea. In addition, during the glacial period, La Niña-like process was stronger in the tropical Pacific, resulting in an increase in rainfall and increased volcanic materials (smectite) input into the Philippine Sea. On the contrary, during interglacial period, the strengthened El Niño-like process resulted in the drought in the Philippine islands, and the decreased volcanic materials (smectite) input in the Philippine Sea.

     

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