Hybrid event bed characteristics and its role in high-frequency facies change of the Upper Triassic submarine fan in the West Qinling area of NE Tibetan Plateau
Hybrid event bed characteristics and its role in high-frequency facies change of the Upper Triassic submarine fan in the West Qinling area of NE Tibetan Plateau
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DOI：
10.1016/j.marpetgeo.2022.105937
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发表时间：
2022-09
影响因子：
4.2
通讯作者：
M. Tan;Haonan Sun;Yilin Fu;Xu Zhang;Haonan Cui;Haoran Ma
中科院分区：
文献类型：
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作者：
M. Tan;Haonan Sun;Yilin Fu;Xu Zhang;Haonan Cui;Haoran Ma
混合事件层（HEB）记录了海底扇演化的不平衡，这归因于泥浆强迫的阻尼湍流，这可能是由波瓣主导的海底扇近端或远端段在多个时间尺度上的外源和自生强迫引起的。详细的野外调查结合岩石学和矿物学分析表明，青藏高原东北部西秦岭地区上三叠统海底扇序列主要由浊积岩、HEBs和碎屑岩组成。根据厚度、沉积构造和结构特征，可识别出五种类型的高能量玄武岩。逐层描述和测量表明，这些HEB在整个海底扇序列中显示出独特的分布模式，包括HEB-1和HEB-2层（占71.50%）在分流河道到叶离轴环境（FA 1-FA 3）中占主导地位，HEB-3至HEB-5层（占54.22%）在叶边缘到叶远边缘环境（FA 4-FA 5）中占重要地位。泥质碎屑的结构和岩相特征表明，H1b和H3层段内的杂岩、同质和低粘性泥质碎屑（MC-1 ~ MC-4型）的解体，可能在纵向泥流驱动的湍流和层流行为模式之间的转换中发挥不同的作用。HEB倾向序列的垂直分布的特点是由四种类型的沉积情景，产生显着的外源和自生的签名结合识别的优势HEB类型和增厚或减薄的垂直堆叠的海底瓣向上的趋势。通过对古特提斯洋东缘几个未发现的深水露头的解剖，可以进一步认识古特提斯洋东缘沉积重力流的流动转化，反映在晚三叠世高频海底扇演化的启动、逐渐转换和撕脱过程中。
Hybrid event beds (HEBs) record disequilibrium in submarine fan evolution attributed to mud-forced dampening turbulence, which could be caused by allogenic and autogenic forcings in either the proximal or distal segment of a lobe-dominated submarine fan on several timescales. Detailed field investigation combined with petrographic and mineralogical analysis of selected outcrop samples indicate that the Upper Triassic submarine fan succession mainly comprises turbidites, HEBs, and debrites in the West Qinling (WQ) area of NE Tibetan Plateau. Five types of HEBs are recognized based on the thickness, sedimentary structure, and texture. Bed-by-bed description and measurement reveal that these HEBs show a distinct distribution pattern throughout the submarine fan succession, including dominance of HEB-1 and HEB-2 beds (∼71.50%) in distributary channel to lobe off-axis (FA1–FA3) and significant portion of HEB-3 to HEB-5 beds (∼54.22%) in lobe fringe to lobe distal fringe environments (FA4–FA5). Textural and petrographic characteristics of mudclasts suggest disaggregation of heterolithic, homogenous and less cohesive mudclasts (MC-1 to MC-4 type) within H1b and H3 interval of HEBs, which could play different roles in the longitudinal mud-driven flow transformation between turbulent and laminar flow behavior patterns. The vertical distributions of the HEB-prone succession are characterized by four types of depositional scenarios, which yields significant allogenic and autogenic signatures combined with the recognition of the dominant HEB types and thickening- or thinning-upward trend of the vertically stacked submarine lobes. This study can enhance our understandings of flow transformation of sediment gravity flows (SGF) along the eastern margin of the Paleo-Tethys Ocean based on the anatomy of several undiscovered deep-water outcrops, which were reflected by the initiation, gradual switching, and avulsion of the high-frequency submarine fan evolution during the Late Triassic.