Lithofacies and fluvial–lacustrine environments of the Palaeogene Sevkhuul and Ergil members (Ergiliin Zoo Formation, South Gobi, Mongolia)
Lithofacies and fluvial–lacustrine environments of the Palaeogene Sevkhuul and Ergil members (Ergiliin Zoo Formation, South Gobi, Mongolia)
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DOI：
10.1017/s0016756806001725
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发表时间：
2006-03
影响因子：
2.3
通讯作者：
H. Dill;S. Khishigsuren;J. Bulgamaa;Kh. Bolorma;F. Melcher
中科院分区：
文献类型：
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作者：
H. Dill;S. Khishigsuren;J. Bulgamaa;Kh. Bolorma;F. Melcher
额尔吉林动物园组的碎屑岩层序沿着蒙古戈壁沙漠南部的蒙古-中国边境延伸。暴露在额尔德尼苏姆地区的其成员（Sevkhuul、Ergil）以其始新世晚期和渐新世时代的脊椎动物遗骸而闻名。根据现场工作，大陆红层被细分为四个单元，分别为（I）前三角洲/泥砂坪、（II）三角洲前缘、（III）三角洲平原和（IV）钙质结石。所有子环境均位于河流-湖泊环境中。除了常规的薄片检查外，电子探针分析还应用于揭示由轻矿物（石英、斜长石、三元长石、正长石、蒙脱石、伊利石、稀有坡缕石）、重矿物（铁铝榴石-镁铝榴石固溶体系列、黝帘石-绿帘石）和丰富的针铁矿和碳酸盐矿物（方解石、白云石）。源区暴露的火成岩在成岩作用过程中促进了碳酸盐矿物和含镁片状硅酸盐的形成。在远端冲积层和三角洲沉积物之间的三角洲平原过渡区的较高处，流体从远端冲积-河流沉积物中涌出并形成钙质硬壳。根据岩石颜色、矿物组合和古生态数据得出的结论，气候条件可以描述为干湿季节交替，与现代热带草原的条件非常相似。
The clastic sequence of the Ergiliin Zoo Formation stretches along the Mongolian–Chinese border in the southern Gobi Desert, Mongolia. Its members (Sevkhuul, Ergil) exposed in the Erdene Sum region are well known for their vertebrate remains of Late Eocene and Oligocene age. Based upon field work, the continental red beds were subdivided into four units described as (I) prodelta/mud-sand flat, (II) delta front, (III) delta plain and (IV) calcretes. All sub-environments are in a fluvial–lacustrine setting. Electronmicroprobe analysis, in addition to conventional thin-section examination, was applied to shed some light on the complex mineral association made up of light minerals (quartz, plagioclase, ternary feldspar, orthoclase, smectite, illite, rare palygorskite), heavy minerals (almandine–pyrope solid solution series, zoisite–epidote s.s.s.) and abundant goethite and carbonate minerals (calcite, dolomite). Igneous rocks being exposed in the source area have contributed to the formation of carbonate minerals and Mg-bearing sheet silicates during diagenesis. Higher up on the delta plain transitional between distal alluvial and deltaic deposits, fluids emerged from the distal alluvial–fluvial deposits and formed calcareous duricrusts. Drawing conclusions from the rock colour, the mineral assemblage and the palaeoecological data, the climatic conditions may be described as alternating wet and dry seasons, closely resembling those conditions of a modern savannah.