Environmental and Tectonic Influence on Growth and Internal Structure of a Fringing Reef at Tasmaloum (SW Espiritu Santo, New Hebrides Island Arc, SW Pacific)
Environmental and Tectonic Influence on Growth and Internal Structure of a Fringing Reef at Tasmaloum (SW Espiritu Santo, New Hebrides Island Arc, SW Pacific)
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环境和构造对塔斯马卢姆岸礁生长和内部结构的影响（圣埃斯皮里图西南、新赫布里底群岛弧、太平洋西南）
DOI：
10.1002/9781444304879.ch14
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发表时间：
2009
影响因子：
4.6
通讯作者：
T. Corrège
中科院分区：
文献类型：
--
作者：
G. Cabioch;F. Taylor;J. Récy;R. Edwards;S. Gray;G. Faure;G. Burr;T. Corrège
澳大利亚板块的俯冲导致了新赫布里底群岛中部岛弧（西南太平洋南纬1.5“）的快速抬升。德恩特卡斯特海岭系统是下行板块上的一个突出的测深特征，它正在向新赫布里底岛弧的中部冲下。大多数岛屿的海岸线都有全新世珊瑚礁阶地的出现。沿着圣埃斯皮里图西南海岸，靠近板块边界，出现了6 mm y r '的最大抬升速率。为了调查晚第四纪新构造和环境演变的隆起边缘礁，我们钻了新出现的全新世礁Tasmaloum（西南埃斯皮里图桑托）的深度高达40-45米。如其他地方所述，对不同层次的珊瑚样品进行了230 Th和I4 C测年，并对珊瑚礁的内部结构进行了研究。初步的古生态学和沉积学数据表明：首先，珊瑚礁殖民的基板，并开始增长24 ka弱硬结钙质砂床，这可能是在晚更新世期间形成的，可能是30 ka或更老。这些砂层可能代表了一个较老的珊瑚礁的深前礁区，目前在上升的全新世阶地后面。其次，生物相和珊瑚年龄的礁序列，这是连续的末次盛冰期（LGM），提供了一个内部结构的视图：在24和12-10 ka，珊瑚水平，主要由kroporu gr. hyacinthus和gr. cytlzereu（伴随着一些Gulaxeu gr. fmciculuris），构成中到高能量组合，反映了相对较深，更受保护的环境。然而，在一些水平上，Acroporu gr. dunui/robustu的acroporid积累表明高能环境的改变。从12-10 ka到现在，顶孔类（Acroporu gr. dunui/robustu）、稀少的孔类、大量的结壳珊瑚藻、蠕虫腹足类和结壳有孔虫的组合指示高能环境，可能对应于暴露礁坡的上部。这一生物相序列表明了波浪能量的变化，与受海平面上升、珊瑚礁生长和构造隆起的可变速率的净效应控制的局部水深波动有关。6 ka后，珊瑚和珊瑚藻框架取代珊瑚，珊瑚藻和叠层石组合意味着一个新的水文和海洋制度的建立。生物相和年龄结构表明，自24-ka.1 -yr fi_2以来，生物礁的隆升速率已发生变化。
Subduction of the Australian Plate has caused rapid uplift of the central New Hebrides island arc (1 5"S, SW Pacific). The d'Entrecasteaux ridge system, a prominent bathymetric feature on the downgoing plate, is underthrusting the central part of the New Hebrides arc. The coastlines of most islands are characterized by emerged Holocene coral reef terraces. A maximum uplift rate of 6 mm y r ' occurs along the south-west coast of Espiritu Santo, near the plate boundary. To investigate the Late Quaternary neotectonic and environmental evolution of the uplifted fringing reefs, we drilled the emerged Holocene reef at Tasmaloum (SW Espiritu Santo) to depths as great as 40-45 m. Coral samples from various levels were dated by 230Th and I4C, as described elsewhere, and the intemal structure of the reefs was studied. Preliminary palaeoecological and sedimentological data indicate the following. First, the coral reef colonized a substrate and began to grow by 24 ka on weakly indurated calcareous sand beds, which probably formed during the Late Pleistocene and are possibly as old as 30 ka or more. These sand levels could represent the deep fore-reef area of an older reef, at present behind the uplifted Holocene terraces. Second, the biofacies and coral ages from the reef sequence, which is continuous from the last glacial maximum (LGM), provide a view of the internal structure: between 24 and 12-10 ka, coral levels, composed mainly ofkroporu gr. hyacinthus and gr. cytlzereu (accompanied by a few Gulaxeu gr. fmciculuris), constitute mediumto high-energy assemblages, reflecting relatively deeper and more protected environments. However, at a few levels, acroporid build-ups of Acroporu gr. dunui/robustu indicate high-energy environment altemation. Between 12-10 ka and the present, assemblages of acroporids (Acroporu gr. dunui/robustu), scarce poritids, numerous encrusting coralline algae, vermetid gastropods and encrusting foraminiferids indicate high-energy environments, probably corresponding to the upper part of the exposed reef slopes. This biofacies succession indicates changes in wave energy, related to fluctuations in local bathymetry controlled by the net effect of variable rates of sea-level rise, reef growth and tectonic uplift. After 6 ka, the replacement of coral, coralline algal and stromatolite assemblages by coral and coralline algal frameworks implies the establishment of a new hydrological and oceanographic regime. The biofacies and age structure of the reef show that the uplift rate has vaned sinze24-ka.1 -I ,:-y r f i_.--