Postglacial Early Permian (late Sakmarian–early Artinskian) shallow-marine carbonate deposition along a 2000 km transect from Timor to west Australia
Postglacial Early Permian (late Sakmarian–early Artinskian) shallow-marine carbonate deposition along a 2000 km transect from Timor to west Australia
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DOI：
10.1016/j.palaeo.2014.05.009
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发表时间：
2014-09
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通讯作者：
D. Haig;E. McCartain;A. Mory;Gilsel Borges;V. Davydov;M. Dixon;A. Ernst;Stefan Groflin;E. Håkansson;M. Keep;Z. D. Santos;G. Shi;Jacinto Soares
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作者：
D. Haig;E. McCartain;A. Mory;Gilsel Borges;V. Davydov;M. Dixon;A. Ernst;Stefan Groflin;E. Håkansson;M. Keep;Z. D. Santos;G. Shi;Jacinto Soares
北起帝汶岛（Timor），南至珀斯盆地北部，延伸至东冈瓦纳内陆的海相克拉通内裂谷盆地中，普遍存在萨克纪晚期至早二叠世（Artinskian）早期碳酸盐岩沉积。这些盆地跨越古纬度约20°（约35°S至55°S）。本文描述了东帝汶Maubisse灰岩的类型剖面，并将其与Canning盆地（Poole砂岩的Nura Nura段）、Carnarvon盆地南部（Callytharra组）和Perth盆地北部（Holmwood页岩的Fossil Cliff段）的碳酸盐岩剖面进行了比较。碳酸盐单元没有冰川的影响，形成了一个主要沉积旋回的一部分，在南部盆地，它覆盖在受冰川影响的地层上，位于泥岩下面很短的距离，泥岩中含有海洋化石和散落的坠石（可能表明海冰）。在南部，海相条件受到限制，并被沉积层序顶部的煤系所取代。在北部，碳酸盐岩矿床可能为苔藓虫-海珊瑚丘；而在南部盆地，它们形成横向连续的相对较薄的层，沉积在非常低梯度的海底，在页岩-灰岩准层序的顶部，在准层序集中向上加厚。层序内的所有海相沉积都发生在非常浅的（内浅海）条件下，灰岩具有相似的颗粒组成。苔藓虫和海百合碎屑为主，腕足类壳碎片、有孔虫和介形虫瓣通常常见。虽然很少，但在北方更常见，它们的分布范围远至南卡那封盆地。腹足类和双壳类动物的壳碎片、棘刺、单生的褶皱珊瑚和三叶虫的甲壳元素是罕见的。颗粒组合的均匀性和缺乏热带元素，如较大的有孔虫，殖民地珊瑚或水藻，表明温带海洋环境，只有轻微的北部温度升高。所研究的碳酸盐矿床的沉积旋回比之前受冰川影响的阿塞利亚期至早萨克森期和随后的“中”阿廷斯基期的冷期更为温暖，随后是阿廷斯基期晚期至早昆古里期的显著变暖。西澳大利亚盆地冷暖间隔的时间似乎与东澳大利亚演替不一致，但这可能是由于特有动物和孢粉植物造成的年代地层错配问题。
Late Sakmarian to early Artinskian (Early Permian) carbonate deposition was widespread in the marine intracratonic rift basins that extended into the interior of Eastern Gondwana from Timor in the north to the northern Perth Basin in the south. These basins spanned about 20° of paleolatitude (approximately 35°S to 55°S). This study describes the type section of the Maubisse Limestone in Timor-Leste, and compares this unit with carbonate sections in the Canning Basin (Nura Nura Member of the Poole Sandstone), the Southern Carnarvon Basin (Callytharra Formation) and the northern Perth Basin (Fossil Cliff Member of the Holmwood Shale). The carbonate units have no glacial influence and formed part of a major depositional cycle that, in the southern basins, overlies glacially influenced strata and lies a short distance below mudstone containing marine fossils and scattered dropstones (perhaps indicative of sea ice). In the south marine conditions became more restricted and were replaced by coal measures at the top of the depositional sequence. In the north, the carbonate deposits are possibly bryozoan–crinoidal mounds; whereas in the southern basins they form laterally continuous relatively thin beds, deposited on a very low-gradient seafloor, at the tops of shale–limestone parasequences that thicken upward in parasequence sets. All marine deposition within the sequence took place under very shallow (inner neritic) conditions, and the limestones have similar grain composition. Bryozoan and crinoidal debris dominate the grain assemblages and brachiopod shell fragments, foraminifera and ostracod valves are usually common.Tubiphytesranged as far south as the Southern Carnarvon Basin, albeit rarely, but is more common to the north. Gastropod and bivalve shell debris, echinoid spines, solitary rugose corals and trilobite carapace elements are rare. The uniformity of the grain assemblage and the lack of tropical elements such as larger fusulinid foraminifera, colonial corals or dasycladacean algae indicate temperate marine conditions with only a small increase in temperature to the north.The depositional cycle containing the studied carbonate deposits represents a warmer phase than the preceding glacially influenced Asselian to early Sakmarian interval and the subsequent cool phase of the “mid” Artinskian that is followed by significant warming during the late Artinskian–early Kungurian. The timing of cooler and warmer intervals in the west Australian basins seems out-of-phase with the eastern Australian succession, but this may be a problem of chronostratigraphic miscorrelation due to endemic faunas and palynofloras.