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首页> 外文期刊>Quaternary Research: An Interdisciplinary Journal >A significant middle Pleistocene tephra deposit preserved in the caves of Mulu, Borneo
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A significant middle Pleistocene tephra deposit preserved in the caves of Mulu, Borneo

机译：一个重要的中更新世特非拉沉积物保存在婆罗洲穆鲁的洞穴中

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A distinctive white sediment in the caves of Mulu, Sarawak, Borneo is a well-preserved tephra, representing a fluvially transported surface air-fall deposit, re-deposited inside the caves. We show that the tephra is not the Younger Toba Tephra, formerly considered as most likely. The shards are rod-shaped with elongate tubular vesicles; the largest grains ~170μm in length; of rhyolitic composition; and ~(87)Sr/ ~(86)Sr ratio of 0.70426±0.00001. U-Th dating of associated calcites suggest that the tephra was deposited before 125±4ka, and probably before 156±2ka. Grain size and distance from closest potential source suggests an eruption of VEI 7. Prevailing winds, grain size, thickness of deposit, location of potential sources, and Sr isotopic ratio limit the source to the Philippines. Comparisons with the literature give the best match geochemically with layer 1822 from Ku et al. (2009a), dated by ocean core stratigraphy to 189ka. This tephra represents a rare terrestrial repository indicating a very substantial Plinian/Ultra-Plinian eruption that covered the Mulu region of Borneo with ash, a region that rarely receives tephra from even the largest known eruptions in the vicinity. It likely will be a valuable chronostratigraphic marker for sedimentary, palaeontological and archaeological studies.
机译：婆罗洲沙捞越穆鲁（Mulu）洞穴中有一种独特的白色沉积物，是保存完好的特非拉（Tephra），代表河流运输的地面空降沉积物，重新沉积在洞穴内部。我们显示该特非拉不是以前被认为是最有可能的“年轻鸟羽特非拉”。碎片为杆状，带有细长的管状囊泡;最大晶粒长约170μm;流纹组成〜（87）Sr /〜（86）Sr比为0.70426±0.00001。关联方解石的U-Th测年表明，前叶沉积在125±4ka之前，可能在156±2ka之前。晶粒尺寸和与最接近潜在污染源的距离表明VEI 7喷发。盛行的风，晶粒尺寸，矿床厚度，潜在污染源的位置以及Sr同位素比将污染源限制在菲律宾。与文献的比较在地球化学上与Ku等人的1822层最匹配。 （2009a），根据海洋核心地层的年代为189ka。该特非拉火山代表着一个罕见的陆地储藏库，指示着非常严重的普利尼亚/超普林尼阿喷发，火山灰覆盖了婆罗洲的穆鲁地区，该地区即使是附近最大的已知火山喷发也很少收到特非拉火山。这可能将是沉积，古生物学和考古研究的有价值的年代地层标记。

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