Component analysis of three TV-guided grab sampler from the Sahul Shelf (NW Australia)

This paper constitutes a first detailed and systematic facies and biota description of an isolated carbonate knoll (Pee Shoal) in the Timor Sea (Sahul Shelf, NW Australia). The steep and flat-topped knoll is characterized by a distinct facies zonation comprising (A) soft sediments with scattered debris and scarce sponges, hydrozoans and crinoids (320-210 m water depth), (B) hardground outcrops (step-like banks, vertical cliffs) that are mainly colonized by octocorals and sponges (210-75 m), and (C) the summit region (75-21 m) where the slopes merge gently into the flat-topped summit that is densely colonized by massive and encrusting zooxanthellate corals and the octocoral Heliopora coerulea. In contrast, the sediments recovered from the summit are dominated by the green alga Halimeda, subordinate components are corals, benthic foraminifers, mollusks, and coralline red algae. Thus, the sediments are classified as chlorozoan grain assemblage. However, non-skeletal grains (fecal pellets, ooids) are almost completely absent. This discrepancy between the living biota and the sediment composition could reflect a disruption by the severe tropical cyclone Ingrid that hit the northern Australian shelf in March 2005, just before the sampling for this study took place (September 2005).

本研究首次对澳大利亚西北陆架萨胡尔台地（Sahul Shelf）帝汶海（Timor Sea）内一处孤立碳酸盐丘（carbonate knoll）——皮伊滩（Pee Shoal）开展了详细且系统的相带与生物群特征描述。该丘体呈陡峭平顶形态，具有清晰的相带分带特征：(A) 水深320~210米区域，分布着散布碎屑与少量海绵（sponges）、水螅虫（hydrozoans）、海百合（crinoids）的软沉积物；(B) 水深210~75米区域，为阶梯状岸滩、垂直崖壁构成的硬基底露头，主要被八放珊瑚（octocorals）与海绵定植生长；(C) 顶部区域（水深75~21米），坡度平缓过渡至平顶顶部，该区域被块状及包壳型虫黄藻珊瑚（zooxanthellate corals）与八放珊瑚蓝珊瑚（Heliopora coerulea）密集附着生长。与之形成对比的是，从顶部区域采集的沉积物以仙掌藻属（Halimeda）绿藻为主，次要组分包括珊瑚、底栖有孔虫（benthic foraminifers）、软体动物（mollusks）与珊瑚藻（coralline red algae），因此该沉积物被归类为chlorozoan颗粒组合（chlorozoan grain assemblage）。然而，非骨骼颗粒（non-skeletal grains）几乎完全缺失，该类颗粒包含粪球粒（fecal pellets）与鲕粒（ooids）。现生生物群与沉积物组成之间的这种差异，或由2005年3月袭击澳大利亚北部陆架的强热带气旋英格丽德（Ingrid）所导致——该气旋恰好发生在本研究2005年9月开展采样之前。