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Processes of clastic sedimentation associated with Late Cretaceous ophiolite emplacement in the SW segment of the Antalya Complex (S Turkey)
Sedimentary Geology ( IF 2.8 ) Pub Date : 2020-10-01 , DOI: 10.1016/j.sedgeo.2020.105718
Alastair H.F. Robertson , Osman Palak , Kemal Taslı , Paulian Dumitrica

Abstract Clastic sediments provide important clues to the timing and processes of ophiolite emplacement, when integrated into the regional temporal and tectonic framework. Four related settings of Late Cretaceous ophiolite-related clastic sediment deposition are exposed in the SW segment of the Antalya Complex, along the western limb of the Isparta Angle, an orocline in SW Turkey. The restored pre-emplacement paleogeography is indicative of a regional-scale Mesozoic carbonate platform, bordered to the east by a Late Triassic volcanic rift that partially infilled with deep-sea sediments, passing eastwards into several Mesozoic carbonate platforms (floored by pre-rift or syn-rift crust) and finally into the South Neotethys. First, emplacement-related sediments unconformably overlie exhumed ultramafic and gabbroic ophiolitic rocks and comprise locally variable mass-flow deposits (up to several-hundred m thick) that are dominated by subaqueous screes and debris-flow deposits. Fossil evidence (benthic and planktic foraminifera, radiolarians and macrofossils) indicates accumulation during the Campanian-Maastrichtian. Much of the coarse talus was derived from weathering and erosion of intrusive ophiolitic rocks (sheeted dykes, gabbro). Petrographic, XRD and whole-rock geochemical analysis of sandstones and igneous clasts indicate additional derivation from basaltic rocks, interpreted as the eroded extrusive layer of the ophiolite. Additional material was derived from Late Triassic-Cretaceous deep-water volcanics and sediments, and also from Late Cretaceous (and older) platform carbonates. The coarse clastics relate to ophiolite emplacement onto the continental margin, rather than forming in an oceanic setting (e.g., rifted ridge or oceanic fracture zone). The emplacement was associated with crustal extension that exposed ultramafic and gabbroic rocks on the seafloor, where they were covered by clastic debris. Secondly, Late Cretaceous calciturbidites and debris-flow deposits depositionally overlie Late Triassic-Late Cretaceous deep-water passive margin sediments. The clastic debris was derived from the emplacing ophiolite and from an adjacent Mesozoic carbonate platform. Thirdly, calciturbidites and debris-flow deposits also depositionally overlie the same carbonate platform. Fourthly, west of the same carbonate platform, ophiolite-derived mass-flow breccias accumulated locally and were then interleaved with previously emplaced ophiolitic plutonic rocks (mainly serpentinite and gabbro), typically at high angles. The four depositional settings relate to ongoing stages of Late Cretaceous ophiolite emplacement in a setting dominated by regional-scale thrusting and strike-slip (i.e., transpression). The latest Cretaceous deformation and related clastic deposition affected part of the northern, active continental margin of the Southern Neotethys, but without reaching more inboard continental crust (regional Tauride platform), a situation that contrasts with more orthogonally emplaced ophiolites.

中文翻译:

与晚白垩世蛇绿岩在安塔利亚杂岩体(土耳其南部)西南段侵位相关的碎屑沉积过程

摘要 碎屑沉积物为蛇绿岩侵位的时间和过程提供了重要线索,当整合到区域时间和构造框架中时。在安塔利亚杂岩体西南段,沿着伊斯帕尔塔角(土耳其西南部的一个斜斜线)的西翼,有四个与晚白垩世蛇绿岩相关的碎屑沉积物沉积的相关环境。恢复的侵位前古地理表明一个区域尺度的中生代碳酸盐台地,东接晚三叠世火山裂谷,部分充满深海沉积物,向东进入几个中生代碳酸盐台地(由前裂谷或同裂谷地壳)并最终进入南新特提斯。第一的,与就位相关的沉积物不整合地覆盖在挖掘出的超镁铁质和辉长岩蛇绿岩上,并且由局部可变质量流沉积物(高达数百米厚)组成,主要是水下碎屑和碎屑流沉积物。化石证据(底栖和浮游有孔虫、放射虫和大型化石)表明坎帕阶-马斯特里赫特阶有堆积。大部分粗距骨来自侵入蛇绿岩(片状岩脉、辉长岩)的风化和侵蚀。砂岩和火成岩碎屑的岩相学、XRD 和全岩地球化学分析表明玄武岩的额外衍生,解释为蛇绿岩的侵蚀喷出层。其他材料来自晚三叠世-白垩世深水火山岩和沉积物,也来自晚白垩世(和更老的)台地碳酸盐岩。粗碎屑与蛇绿岩在大陆边缘的侵位有关,而不是在大洋环境中形成(例如裂谷海脊或大洋断裂带)。就位与地壳延伸有关,暴露了海底的超镁铁质和辉长岩,在那里它们被碎屑覆盖。其次,晚白垩世钙质浊积岩和碎屑流沉积物沉积在晚三叠世-晚白垩世深水被动边缘沉积物上。碎屑碎片来自包围的蛇绿岩和相邻的中生代碳酸盐平台。第三,方解石浊积岩和碎屑流沉积物也沉积在同一碳酸盐台地之上。第四,同碳酸盐台地以西,蛇绿岩衍生的质量流角砾岩在局部堆积,然后与先前放置的蛇绿岩深成岩(主要是蛇纹岩和辉长岩)交错,通常以大角度。这四种沉积环境与白垩纪晚期蛇绿岩侵位的持续阶段有关,该环境以区域规模的逆冲和走滑(即,挤压)为主。最新的白垩纪变形和相关的碎屑沉积影响了新特提斯南部活动大陆边缘的部分北部,但没有到达更内侧的大陆地壳(区域 Tauride 平台),这种情况与更正交的蛇绿岩形成对比。这四种沉积环境与白垩纪晚期蛇绿岩侵位的持续阶段有关,该环境以区域规模的逆冲和走滑(即,挤压)为主。最新的白垩纪变形和相关的碎屑沉积影响了新特提斯南部活动大陆边缘的部分北部,但没有到达更内侧的大陆地壳(区域 Tauride 平台),这种情况与更正交的蛇绿岩形成对比。这四种沉积环境与白垩纪晚期蛇绿岩侵位的持续阶段有关,该环境以区域规模的逆冲和走滑(即,挤压)为主。最新的白垩纪变形和相关的碎屑沉积影响了新特提斯南部活动大陆边缘的部分北部,但没有到达更内侧的大陆地壳(区域 Tauride 平台),这种情况与更正交的蛇绿岩形成对比。
更新日期:2020-10-01
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