Abstract The Parana Basin is a large volcano-sedimentary basin with a complex depositional history from Ordovician to the Cretaceous period. During Permian significant amounts of organic-rich beds accumulated within the Rio Bonito and Irati formations representing deposition in coastal (deltaic and barrier lagoon) and shallow marine environments, respectively. In this work, the thermal history of these beds is examined from 16 vitrinite reflectance analyses of coal beds (Rio Bonito Formation), integrated with previous data on coal rank, and 21 apatite fission-track (AFT) analyses, collected from 17 well profiles in the south of the Parana Basin. Coal samples showed three different maturity levels. Two with reflectances of 0.4–0.6 and 0.6–0.8%Rr formed by the natural burial history of the basin (the latter is restricted to the Torres Syncline area). In contrast, the third group reached much higher values (1.0–5.0%Rr) related to intrusive igneous rocks. The AFT data show thermal consistency with the reflectance values. The sandstone samples related to the two lower reflectance patterns were partially reset, preserving AFT ages older than the stratigraphic age of the bed. Otherwise, the samples severely affected by the magmatism have Cretaceous and Early Cenozoic ages, but some were much younger than the last magmatic event, implying deep burial before cooling onset. The mean track length distribution of the partially reset samples is short due to the inheritance of tracks preserved from basement cooling history. However, the population of fully reset samples gives crucial information on the maximum temperature reached and the age when cooling started. At these conditions, around 1.0 to 3.0 km of the Parana Basin sequences would have been removed from the surface of the studied areas by erosion since Cretaceous. Regional variations in the amounts of removed sections were controlled by the structural framework, mostly regional NW-SE and NE-SW oriented structures.

中文翻译：

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巴西巴拉那盆地南部早二叠世 Rio Bonito 组的热和沉积历史

摘要 巴拉那盆地是一个大型火山-沉积盆地，从奥陶纪到白垩纪具有复杂的沉积历史。在二叠纪期间，在 Rio Bonito 和 Irati 地层内积累了大量富含有机物的床层，分别代表沿海（三角洲和屏障泻湖）和浅海环境中的沉积。在这项工作中，这些床的热历史是从 16 次煤层（Rio Bonito 组）镜质反射分析中检查的，结合以前的煤等级数据，以及从 17 个井剖面收集的 21 次磷灰石裂变径迹 (AFT) 分析在巴拉那盆地南部。煤样表现出三种不同的成熟度水平。两个反射率分别为 0.4-0.6 和 0.6-0.8%Rr，由盆地的自然埋藏历史形成（后者仅限于托雷斯向斜区域）。相比之下，第三组达到了与侵入火成岩相关的更高的值（1.0-5.0%Rr）。AFT 数据显示了与反射率值的热一致性。与两个较低反射率模式相关的砂岩样本被部分重置，保留了比床层地层年龄更古老的 AFT 年龄。另外，受岩浆作用严重影响的样品具有白垩纪和早新生代的年龄，但有些比上次岩浆活动年轻得多，表明在冷却开始之前埋藏较深。由于从地下室冷却历史中保留的轨迹的继承，部分重置样本的平均轨迹长度分布很短。然而，完全重置样本的总体提供了有关达到的最高温度和冷却开始时的年龄的关键信息。在这些条件下，大约 1.0 到 3。自白垩纪以来，巴拉那盆地层序的 0 公里将被侵蚀从研究区域的表面移除。拆除断面数量的区域变化受结构框架控制，主要是区域 NW-SE 和 NE-SW 导向结构。