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作 者:梁超 解习农 史冠中[2,3] Liang Chao;Xie Xinong;Shi Guanzhong(College of Marine Sciences and Technology China University of Geosciences(Wuhan),Wuhan 430074,China;Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education China University of Geosciences(Wuhan),Wuhan 430074,China;Faculty of Resources,China University of Geosciences(Wuhan),Wuhan 430074,China)
机构地区:[1]中国地质大学海洋学院,武汉430074 [2]中国地质大学构造与油气资源教育部重点实验室,武汉430074 [3]中国地质大学资源学院,武汉430074
出 处:《地质科技情报》2018年第6期54-64,共11页Geological Science and Technology Information
基 金:国家自然科学基金项目(91528301;41402192;41372112);内蒙古满都拉地区晚古生代浊积岩沉积物源研究(2014M562080)
摘 要:内蒙古满都拉地区中二叠统哲斯组上段的重力流堆积特征对理解该区中二叠世晚期的沉积环境具有重要意义。通过对研究区哲斯组上段地层野外露头精细的沉积学研究,识别出了4种重力流沉积岩相组合类型:(1)碎屑流沉积,灰色砾岩,砾石长轴平行层面排列,基质多富含泥质;(2)混合重力流沉积,下部为灰色砾岩,上部为灰色砂岩或泥质砂岩,砾岩中砾石长轴平行层面排列,基质富含泥质,砂岩和泥质砂岩中见较多细小碎屑;(3)高密度浊流沉积,灰色块状砂岩或泥质砂岩,内部常见细小泥质碎屑,偶见干净块状砂岩中分布较多泥质粉砂岩、泥岩团块和撕裂屑;(4)低密度浊流沉积,下部为灰色薄层粉砂岩、泥质粉砂岩,向上变为薄层泥岩。垂向上4种重力流沉积类型相互叠置,发育多个沉积旋回;空间上呈席状展布。剖面对比揭示了重力流沉积由以碎屑流和混合重力流沉积为主-以高密度浊流沉积为主-以低密度浊流沉积为主的相变趋势。该重力流沉积体系中的流体转换需要周围水体的存在,指示其发育于水下环境;而以较薄的席状展布的高密度浊流和低密度浊流沉积为主,不同类型重力流沉积相互叠置,并且缺乏波浪和潮汐改造的沉积构造等现象,则暗示在该重力流沉积体系发育时期,满都拉地区可能处于远端较深水环境。Gravity flow deposits in the upper member of the Middle Permian Zhesi Formation in Mandula area are crucial for understanding the sedimentary environment during the late Middle Permian in the study area.Four sub-types of gravity flow deposits have been recognized:(1)debris flow deposits:gray conglomerates with mud-rich matrix,in which the long axes of gravels are commonly parallel to bedding planes;(2)hybrid sediment gravity flow deposits:gray conglomerates are overlaid by gray sandstones or muddy sandstones;moreover,many small clasts could be recognized in the sandstones and muddy sandstones ;(3)high-density turbidites,gray,structureless sandstones or muddy sandstones,commonly with small clasts.Sometimes,lager muddy siltstone and mudstone clasts could be recognized in clean sandstones;and (4)low-density turbidites:thin layers of gray siltstones or muddy siltstones,grading upwards into thin-layer mudstones.All the subtypes are repeated in the vertical sedimentary sequence,forming multiple sedimentary cycles.The comparison of the profiles indicates that the lithofacies is a gradually transition from the predominant debris flow,hybrid gravity flow deposits,via the predominant high-density turbidites,and finally into the low-density turbidites.The hydrodynamic conditions reflected by the gravity flow systems suggest submarine settings.In addition,the scarcity of waves and tides sedimentary structures implies that the study area might be in a deep-water area in the late Middle Permian.
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