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首页> 外文期刊>Brazilian Journal of Geology >Lowstand Turbidites and Delta Systems of the Itararé Group in the Vidal Ramos region (SC), southern Brazil
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Lowstand Turbidites and Delta Systems of the Itararé Group in the Vidal Ramos region (SC), southern Brazil

机译：巴西南部维达尔拉莫斯地区（SC）的Itararé集团的低位浊积体和三角洲系统

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Turbidites have captioned the attention of sedimentologists during the last decades due their importance as hydrocarbon reservoirs. However, their relationship to delta systems still deserves further studies. This paper presents examples from a late deglacial to early post-glacial deltaic and turbidite strata exposed in the surroundings of Vidal Ramos (Santa Catarina State, Brazil), southern portion of the Paraná Basin. There, the uppermost part of the Mafra Formation and the Rio do Sul Formation onlap the Proterozoic basement and comprises an up to 360 m thick package. It includes (base to top) black shales, mass transport deposits (MTD) and sandy turbidites (Mafra Formation) as well as thin bedded turbidites (tbt), including one interval of black shales and sandy turbidites, overlain by proximal delta front sandstones (Rio do Sul Formation). The analysis of the succession shows two more than 150 m thick coarsening-upwards deltaic successions composed of turbidite sand sheets at their base (prodelta), followed by partially collapsed thin bedded turbidites (delta slope wedge) and delta front sandstones. Both turbidite sand-sheets abruptly overlay black shale intervals related to maximum flooding surfaces and therefore record correlative conformities. A detailed stratigraphic section elaborated from the correlation of four logs (1/100) suggests that distal delta front sands includes both thin bedded turbidites and wave reworked sands whereas the proximal delta front was dominated by long-lived underflows (hyperpycnal flows). The succession suggests that the most expressive turbidite beds (base of the delta systems) have resulted from relative sea-level falls (early lowstand) whereas the thin-bedded turbidites were related to the development of the late lowstand wedge. Black shales represent the transgressive systems tract and HST were not deposited or preserved in the area. High sediment supply associated with lowstand tracts could explain the occasional (Vidal Ramos) to common occurrence of slope failures (slumps and diamictites) involving thin bedded turbidites and delta front sandstones. This situation is quite logical in terms of deglacial periods, and resulting high sediment supply, within a long-term icehouse context, with prevalence of lowstand to transgressive settings.
机译：在过去的几十年中，由于浊积岩作为碳氢化合物储集层的重要性，使浊积岩受到了沉积学家的关注。但是，它们与增量系统的关系仍然值得进一步研究。本文提供了巴拉那盆地南部维达尔拉莫斯（巴西圣卡塔琳娜州）周围暴露的晚冰期到冰期后三角洲和浊积岩地层的实例。那里，Mafra组和Rio do Sul组的最上部分覆盖在元古生界基底上，包括一个厚达360 m的包裹。它包括（底部到顶部）黑色页岩，大量沉积物（MTD）和砂质浊积岩（Mafra层），以及薄层状浊积体（tbt），包括黑色页岩和砂质浊积岩的一个层段，上面覆盖有近端三角洲前砂岩（南里约热内卢组）。对演替的分析表明，有两个大于150 m的向上粗化的三角洲演替，它们的底部（前三角洲）为浊积砂岩片，随后为部分塌陷的薄层状浊积岩（三角洲斜楔）和三角洲前砂岩。两种浊质砂岩突然覆盖了与最大洪泛面有关的黑色页岩层段，因此记录了相关的一致性。从四个测井曲线（1/100）的相关性详细阐述的详细地层剖面表明，远三角洲前缘砂岩既包括薄层浊积岩，也包括波状返工砂，而近海三角洲前缘砂岩主要是长寿命的底流（高渗流）。演替表明，最富表现力的浊积岩床（三角洲系统的基础）是由于相对海平面下降（早期低水位）而形成的，而薄层浊积岩与后期低水位楔形物的发育有关。黑色页岩代表海侵体系，HST未沉积或保存在该地区。与低水位道相关的高沉积物供应可能解释了偶然的（维达尔拉莫斯）与薄层状浊积石和三角洲前砂岩发生的边坡破坏（塌陷和铁矾土）的偶然发生。就冰川期而言，这种情况是合乎逻辑的，在长期的冰库环境中，由此产生的沉积物供应量很高，而低潮位向海侵环境盛行。

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