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首页> 外文期刊>Sedimentary geology >Facies relationships recorded in a Late Paleozoic fluvio-deltaic system (Parana Basin, Brazil): Insights into the timing and triggers of subaqueous sediment gravity flows
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Facies relationships recorded in a Late Paleozoic fluvio-deltaic system (Parana Basin, Brazil): Insights into the timing and triggers of subaqueous sediment gravity flows

机译：晚古生代河流-三角洲系统（巴西帕拉纳盆地）中记录的相间关系：洞察水下泥沙重力流的时间和触发因素

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This paper aims at documenting the spatial and genetic relationships between fluvial and subaqueous gravity flow deposits in an ancient fluvio-deltaic system exposed in the eastern border of the Parana Basin, southern Brazil. The examined interval comprises the Pedra Alta sandstone and associated deposits, which are included in the glacially-influenced, Late Paleozoic Itarare Group. Five facies associations were identified and comprise the following coeval depositional settings from the more proximal to the more distal: A) braided fluvial/deltaplain, B) channel-mouth zone, C) delta-slope, D) distal marine glacially-influenced and E) non-cohesive density -flow deposits. These facies associations form a conformable, shallowing-upward succession about 200 m thick, whose stacking pattern is interpreted as a postglacial progradation. The stratigraphic architecture suggests a genetic correlation between high-energy fluvial discharges (possibly related to meltwater release) and coarse grained deposits (non-cohesive density-flow deposits) accumulated on the delta foreset and bottomset. Mass transport deposits were more likely triggered"by sediment load increase on the delta slope due to high sediment supply, rather than by relative sea-level fall. The stratigraphic evolution can be reconstructed considering an initial stage characterized by a grounded ice margin and the deposition of mudstones with ice-rafted debris (glacial stage). This stage was succeeded by a second phase in which a fluvial system formed as a result of ice-margin retreat farther to the SE (postglacial stage). This glacial-postglacial stratigraphic succession is different from that recognized by previous workers in the Itarare Group, a conclusion that impacts greatly in reservoir prediction and modeling in the Parana Basin. (C) 2016 Elsevier B.V. All rights reserved.
机译：本文旨在记录暴露于巴西南部巴拉那盆地东部边界的古老河流-三角洲系统中河流与水下重力流沉积物之间的空间和遗传关系。所检查的层段包括Pedra Alta砂岩和相关的沉积物，这些都包括在受冰川影响的晚古生代Itarare组中。从近端到远端，确定了五个相的组合，包括以下的近代沉积背景：A）辫状河床/三角洲，B）槽口区，C）三角坡，D）海洋冰河化和E ）非粘性密度流动沉积物。这些相的组合形成了一个约200 m厚的顺应性浅向上的演替，其堆积模式被解释为冰期后的演化。地层学结构表明，高能河流排放物（可能与融水释放有关）与三角洲前缘和底端堆积的粗粒沉积物（非粘性密度流沉积物）之间存在遗传相关性。大量运输的沉积物更有可能是“由于沉积物供应量高而不是相对海平面下降而增加了三角洲斜坡上的沉积物负荷而引起的。”地层演化可以考虑初始阶段以地缘冰缘和沉积为特征来重建。由冰漂碎屑形成的泥岩（冰期），此阶段的第二阶段是冰缘退缩至东南（冰期后）形成的河流系统，这是第二阶段。与Itarare集团以前的工作人员所认可的结论不同，这一结论对巴拉那盆地的储层预测和建模有很大影响（C）2016 Elsevier BV保留所有权利。

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