The late Paleozoic Ice Age along the southwestern margin of Gondwana: Facies models, age constraints, correlation and sequence stratigraphic framework
The late Paleozoic Ice Age along the southwestern margin of Gondwana: Facies models, age constraints, correlation and sequence stratigraphic framework
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冈瓦纳西南缘晚古生代冰河期：相模型、年龄限制、对比和层序地层格架
DOI：
10.1016/j.jsames.2020.103056
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发表时间：
2021
影响因子：
1.8
通讯作者：
Alonso-Muruaga, Pablo J.
中科院分区：
文献类型：
--
作者：
López-Gamundí, Oscar;Limarino, Carlos O.;Isbell, John L.;Pauls, Kathryn;Césari, Silvia N.;Alonso-Muruaga, Pablo J.
南美洲西南边缘提供了影响冈瓦纳超大陆的晚古生代冰期（LPIA）的完整记录。近年来，在新的辐射日期和生物地层（动植物群）分区的帮助下，LPIA冰川期的三重划分已被细化为五个较短寿命的离散事件：1.最新泥盆世-最早的图尔奈期，2.图尔奈期，3.维西恩期，4.谢尔普霍夫期-早巴什基尔期，5.宾夕法尼亚期晚期-最早二叠纪。这些冰川事件被冰后海侵沉积物和海洋动物所覆盖。冰川沉积物的不平衡保存潜力，偏向冰川海洋沉积物，提供了不均匀的地层记录，其中大陆冰川沉积的案例很少，仅限于谢尔普霍夫阶-早巴什基尔事件，而海洋环境中冰川沉积的例子也很多。海洋环境中的冰川沉积可分为两个主要相组合：山谷-冰川-退缩（峡湾）相组合和开放海洋区域的海底-退缩（冰川海洋裙带）相组合。过渡相与冰后海侵过程中山谷洪水形成的过渡相相对应，广泛分布于阿根廷西部的原记录地拉，其中古峡湾序列充分暴露，特别是在帕甘索盆地西部，并绘制了塔里哈盆地地下的地图。一般的古峡湾模型包括（从底部到顶部）以下阶段：（i）古河谷的切割和冰接触三角洲中冰下混积岩的沉积，（ii）早期海侵阶段，其特征是冰河前环境中水下沉积物重力流和塌陷对冰下物质的重新沉积，（iii）最大洪水（晚期海侵阶段），以与海洋入侵有关的黑色页岩或层状泥岩为主，被洪水淹没的山谷；正常的海洋或微咸水条件可能主导这一阶段；(iv) 高位：河流三角洲系统的进积，在某些情况下包括吉尔伯特型三角洲。在冰洋裙带环境中，基底相包括大量碎屑支撑的砾岩，很少有条纹和抛光碎屑，随后是向上细化的序列，包括带有冰筏碎屑（IRD）的薄层混积岩和混积岩层中局部扭曲的砂岩块，表明了块体侵位机制。耕作间和耕内铺装的存在表明沿盆地边缘的冰川前进/后退波动。冰消序列主要反映了冰盖、冰盖和高山冰川退缩期间的沉积以及连续的消冰作用，可以作为分析冈瓦纳西南部冰川演替的业务工具。它们的特点是在开阔的海洋环境中相当简单的向上细化序列，例如卡林加斯塔-乌斯帕亚塔盆地、克拉罗梅科盆地（和邻近的文塔纳褶皱带，VFB）的大部分以及巴拉那和卡鲁盆地的中部部分。在更近的地区（即古峡湾），这种垂直趋势通常被附近起源地区供给的三角洲楔所打断。冈瓦纳西南部晚古生代与冰川相关的序列表现出共同的三重图案，相当于估计持续时间为 10-80 Myr 的二级序列。下部对应于冰川和受冰川影响的混积岩；中间期始于冰期后的海侵。下部和中部区间对应于冈瓦纳几个盆地所描述和识别的冰消序列。最后，上面的术语包括沿海……
The southwestern margin of South America offers a complete record of the Late Paleozoic Ice Age (LPIA) that affected the Gondwana supercontinent. The tripartite division of LPIA glacial episodes has been refined with the help of new radiometric dates and biostratigraphic (flora and fauna) zonations in recent years to five shorter-lived discrete events: 1. Latest Devonian-earliest Tournaisian, 2. Tournaisian, 3. Visean, 4. Serpukhovian-Early Bashkirian, 5. late Pennsylvanian-earliest Permian. These glacial events are capped by postglacial transgressive deposits with marine fauna. The unbalanced preservation potential of the glacial deposits, skewed toward the glaciomarine sediments, provides an uneven stratigraphic record with few cases of continental glacial sedimentation, confined to the Serpukhovian-Early Bashkirian event, and numerous examples of glacial sedimentation in marine environments. Glacial sedimentation in marine settings has been grouped in two main facies associations: a valley-glacier-retreat (fjord) facies association and a submarine-retreat (glaciomarine apron) facies association in open-marine areas.Transitional facies, correspondent to those formed by the flooding of valleys during postglacial transgressions, are widely distributed along the Protoprecordillera in western Argentina, where paleofjord successions are well exposed particularly in western Paganzo Basin, and mapped in subsurface in the Tarija basin. A general paleofjord model includes (from base to top) the following stages: (i) Incision of paleovalley and deposition of subglacial diamictites in ice contact deltas, (ii) Early Transgressive stage characterized by resedimentation of subglacial material by subaqueous sediment gravity flows and slumps in proglacial settings, (iii) Maximum flooding (late transgressive stage) dominated by black shales or laminated mudstones related to a marine incursion that flooded valleys; normal marine or brackish conditions may dominate this stage and (iv) Highstand: progradation of a fluvial-deltaic system including in some cases Gilbert-type deltas. In glaciomarine apron environments, the basal facies includes massive clast-supported conglomerates, with few striated and polished clasts, followed by fining-upward successions including thinly bedded diamictites with ice-rafted debris (IRD) and locally contorted sandstone masses in diamictite beds, indicative of mass-emplacement mechanisms. The presence of inter- and intratill pavements suggests glacial advance/retreat fluctuations along the basin margins.Deglaciation sequences, reflecting deposition mainly during the retreat of ice sheets, ice caps and alpine glaciers and successive deglaciation, can be used as operational tools for the analysis of glacial successions in southwestern Gondwana. They are characterized as rather simple upward-fining successions in open marine settings as exemplified in most of the Calingasta-Uspallata Basin,Claromecó Basin (and adjacent Ventana foldbelt, VFB) and central portions of the Paraná and Karoo basins. In more proximal areas (i.e., paleofjords) this vertical trend is commonly punctuated with deltaic wedges fed by nearby provenance areas.The late Paleozoic glacial-related successions of southwestern Gondwana exhibit a common tripartite motif, equivalent to second-order sequences with estimated durations of 10–80 Myr. The lower section corresponds to glacial and glacially-influenced diamictites; the middle interval is initiated with postglacial transgressions. The lower and middle intervals correspond to the deglaciation sequence as described and identified in several basins of Gondwana. Finally, the upper term includes coastal …
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