Abstract The early Mesozoic extensional processes recognized in SW Gondwana have been related to a supercontinent precursor break-up phase, the gravitational collapse of a late Paleozoic orogen, changes in subduction dynamics or the impact of a thermal anomaly. However, intraplate extension is still lacking accurate temporal constraints for the area devoid of the influence of subduction-related extensional processes that affected its margin between mid-Permian and Early Cretaceous times. Evidence from this intraplate extensional phase is found in the Cara Cura – Reyes depocenter of the Neuquen basin located in west-central Argentina. Field and seismic evidence allowed identifying synextensional growth geometries, and zircon U-Pb SHRIMP dating of volcanic rocks revealed ages of 198.8 ± 2.0 Ma and 195.4 ± 1.0 Ma for the oldest and youngest exposed synrift deposits. These allowed limiting the mechanical subsidence phase to the Sinemurian, which was followed by a Pliensbachian – Toarcian hiatus separating it from the postrift deposits. These deposits are characterized by a series of marine transgressive-regressive cycles separated by sedimentation gaps, constrained in this sector to the Bathonian – Callovian and the Kimmeridgian. When inserted into the broader realm of the Neuquen basin, a diachronic development for both the synrift and postrift deposits is evident, although the synrift-postrift transition occurred at ca. 190 Ma. The correlation of these events along SW Gondwana supports a common tectonic evolution which, at the same time, allows correlating the hiatus detected in postrift sedimentation of the Cara Cura – Reyes depocenter with Jurassic intraplate contractional events. The shift in the intraplate tectonic regime coincides with a radical change in Gondwana’s absolute motion, being northwards during extension, and southwards during contraction, after the opening of the Central Atlantic Ocean. Therefore, upper-plate dynamics seems to have played a first-order role during the opening of the Neuquen basin.

中文翻译：

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受 U-Pb SHRIMP 定年约束的阿根廷中西部早侏罗世板内伸展：对内乌肯盆地开放的影响

摘要 冈瓦纳西南地区发现的早期中生代伸展过程与超大陆前体破裂阶段、晚古生代造山带的重力坍塌、俯冲动力学变化或热异常的影响有关。然而，对于没有俯冲相关伸展过程影响的区域，板内伸展仍然缺乏准确的时间约束，这些伸展过程影响了二叠纪中期和早白垩世之间的边缘。在位于阿根廷中西部的内乌肯盆地的卡拉库拉 – 雷耶斯沉积中心发现了来自这种板内伸展阶段的证据。野外和地震证据允许识别同伸生长几何形状，火山岩的锆石 U-Pb SHRIMP 测年显示年龄为 198.8 ± 2.0 Ma 和 195.4 ± 1。0 Ma 为最老和最年轻的暴露的同裂谷沉积物。这些允许将机械下沉阶段限制在 Sinemurian 阶段，随后是 Pliensbachian - Toarcian 断层，将其与后裂谷沉积物分开。这些沉积物的特征是一系列被沉积间隙隔开的海侵-海退旋回，在该区域内仅限于巴顿阶 - 卡洛维阶和基默里阶阶。当插入内乌肯盆地更广阔的领域时，同裂谷和后裂谷沉积物的历时发展是明显的，尽管同裂谷-后裂谷转变发生在大约 190 马。这些沿西南冈瓦纳的事件的相关性支持了共同的构造演化，同时，允许将在 Cara Cura – Reyes 沉积中心的裂谷后沉积中检测到的间断与侏罗纪板内收缩事件相关联。板内构造体制的转变与冈瓦纳大陆绝对运动的根本变化同时发生，在中大西洋开放后，在伸展时向北，在收缩时向南。因此，在内乌肯盆地的开放过程中，上板块动力学似乎起到了一级作用。