Composition and Genesis of Temperate, Shallow-Marine Carbonate Muds: Spencer Gulf, South Australia
Composition and Genesis of Temperate, Shallow-Marine Carbonate Muds: Spencer Gulf, South Australia
复制标题
温带浅海碳酸盐泥的成分和成因：南澳大利亚斯宾塞湾
DOI：
10.2110/jsr.2015.73
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发表时间：
2015
影响因子：
2
通讯作者：
N. James
中科院分区：
文献类型：
--
作者：
L. O'connell;N. James
摘要 浅海非热带海洋环境中碳酸盐泥（粒度 < 63 µm）的起源鲜有记录。粗粒碳酸盐通常是沿海温带海底的特征，但许多此类矿床也含有丰富的碳酸盐泥。斯宾塞湾是澳大利亚南部边缘的一个大型浅海湾（水深 < 60 m），含有碳酸盐砾石、沙子和泥浆的混合物，其中泥浆体积含量高达 84%。底栖环境包括茂密的海草草甸、沙荒地和红石铺地，其中双壳类、底栖有孔虫、珊瑚藻和苔藓虫在杂动物碳酸盐组合中占主导地位。使用扫描电子显微镜对泥粒形态进行了研究，得出的结论是，泥主要由骨骼碎片（双壳类、底栖有孔虫、海鞘类、棘皮类动物和珊瑚藻）组成，解释为是由于浸渍后刚性材料分解而形成的。 X射线衍射分析证实这些泥浆含有中镁方解石、低镁方解石和霰石的组合；根据骨骼颗粒类型，不同地点的浓度有所不同。斯宾塞湾泥浆的矿物学和成分与热带和深水碳酸盐泥沉积的经典模型不同。与浅水热带碳酸盐泥不同，这些温带泥不以文石为主，也没有海水中碳酸盐沉淀的证据。与深水泥浆相比，浮游生物对这些沉积物的贡献微乎其微。
Abstract The origin of carbonate muds (grain sizes < 63 µm) in shallow, nontropical marine environments is poorly documented. Coarse-grained carbonates often characterize coastal temperate seafloors, but many such deposits also have abundant carbonate muds. Spencer Gulf, a large, shallow embayment along the southern Australian margin (< 60 m water depth), contains mixtures of carbonate gravels, sands, and muds, with muds constituting up to 84% volumetrically. Benthic environments include dense seagrass meadows, sand barrens, and rhodolith pavements where bivalves, benthic foraminifera, coralline algae, and bryozoans dominate heterozoan carbonate assemblages. Mud grain morphologies were investigated using scanning electron microscopy, leading to the conclusion that muds are predominantly composed of skeletal fragments (bivalves, benthic foraminifera, ascidians, echinoderms, and coralline algae), interpreted to have formed due to breakdown of rigid material via maceration. X-ray diffraction analysis confirms that these muds contain combinations of intermediate-Mg calcite, low-Mg calcite, and aragonite; with concentrations varying among locations according to skeletal grain types. Spencer Gulf muds differ in mineralogy and composition from those of classic models of tropical and deep-water carbonate mud deposition. Unlike shallow-water, tropical carbonate muds, these temperate muds are not dominated by aragonite and there is no evidence of carbonate precipitation from seawater. Pelagic organisms contribute only trivial amounts to these deposits, in contrast to deep-water muds.