Abstract In the southern Central Andes, between 27 and 33°S, a flab-slab subduction has been established since the last 10 Ma. This particular subduction geometry has been proposed to control the eastward migration of the deformation, with the Precordillera fold-and-thrust belt development and the uplift of the foreland Sierras Pampeanas basement blocks. In this study, we present a 190 km-long structural section, across the easternmost Cordillera Frontal, the Precordillera and the westernmost sector of the Sierras Pampeanas, and revise both previous kinematic models, and the relationship between the establishment of the flat-slab and deformation in the foreland. For this purpose, we integrate published sedimentological data with a new structural analysis. Our forward kinematic model is fed back by: (i) the geometries of Neogene deformed beds throughout the Precordillera, such as sedimentary wedges and angular unconformities; (ii) flexural subsidence due to the topographic and sedimentary loads for each deformation step, constrained by measured stratigraphic sections; (iii) a revised chronostratigraphy and correlation chart of the Cenozoic sedimentary units; and, (iv) recent constraints on the ages of activity of the faults. This allows us to build a model that considers the timing of deformation for each main structure and its relationship with sedimentation, producing a model with better geometrical, sedimentological and paleogeographical constraints than previous proposals. The results of this modelling are presented in six different evolutionary stages. During the first stage, between 19 and 15 Ma, the eastern Cordillera Frontal is uplifted, associated with subsidence in the Rodeo-Iglesia proximal foreland basin, and low subsidence in the Bermejo distal foreland basin. In the second stage, between 15 and 12 Ma, uplift of the Western Precordillera took place, associated with the creation of a shallow detachment beneath the Rodeo-Iglesia basin. The third stage, between 12 and 8 Ma, was the beginning of the Central Precordillera uplift and the first pulse of uplift in the Valle Fertil range. During the next stage, between 8 and 5 Ma, the Central Precordillera rapidly deformed. Between 5 and 2 Ma, deformation in the Western and Central Precordillera almost ceased, and the focus of contractional deformation shifted to the Eastern Precordillera. The last 2 Ma phase is characterized by strike-slip deformation in the Rodeo-Iglesia basin and contractional deformation in the Eastern Precordillera and the Valle Fertil range. The key results are that the amount of total shortening, 66 km (35%), calculated for the cross-section, is significantly less than previously proposed, and the detachment of the Precordillera fold-and-thrust belt is shallower (∼6.5 km vs 16 km) than previous models. This last point allows us to connect the Cordillera Frontal with the Precordillera, with a ramp-plane geometry of the detachment, as previously suggested, but allowing at the same time the subsidence and the generation of the observed geometries in the Rodeo-Iglesia basin.

中文翻译：

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重新审视 Jáchal 河横截面（阿根廷安第斯山脉，南纬 30 度）：来自新近系同源沉积物的年代学和几何学的限制

摘要 在中南安第斯山脉南部，27°S～33°S，近10 Ma以来形成了扁平板状俯冲。这种特殊的俯冲几何结构已被提出来控制变形的向东迁移，伴随着 Precordillera 褶皱和逆冲带的发展和前陆 Sierras Pampeanas 基底块体的隆起。在这项研究中，我们提出了一个 190 公里长的构造剖面，横跨最东端的 Cordillera Frontal、Precordillera 和 Sierras Pampeanas 的最西端，并修改了先前的运动学模型，以及平板和板坯建立之间的关系。前陆变形。为此，我们将已发表的沉积学数据与新的结构分析相结合。我们的正向运动学模型反馈如下：(i) 整个 Precordillera 新近纪变形层的几何形状，例如沉积楔形和角不整合面；(ii) 由于每个变形步骤的地形和沉积载荷引起的弯曲沉降，受测得的地层剖面的约束；(iii) 经修订的新生代沉积单元年代地层和对比图；(iv) 最近对断层活动年龄的限制。这使我们能够建立一个模型，该模型考虑每个主要结构的变形时间及其与沉积的关系，从而产生一个比以前的建议具有更好的几何、沉积学和古地理约束的模型。这种建模的结果呈现在六个不同的进化阶段。在第一阶段，在 19 到 15 Ma 之间，东部 Cordillera Frontal 隆起，与 Rodeo-Iglesia 近端前陆盆地的沉降和 Bermejo 远端前陆盆地的低沉降有关。在第二阶段，在 15 到 12 Ma 之间，西部 Precordillera 发生了抬升，与在 Rodeo-Iglesia 盆地下方形成浅层拆离有关。第三阶段，在 12 到 8 Ma 之间，是中央 Precordillera 隆起的开始和 Valle Fertil 范围的第一个隆起脉冲。在下一阶段，在 8 到 5 Ma 之间，中央前科迪勒拉迅速变形。5~2 Ma，西、中前科迪勒拉的变形基本停止，收缩变形的重点转移到东前科迪勒拉。最后 2 Ma 阶段的特征是 Rodeo-Iglesia 盆地的走滑变形和东部 Precordillera 和 Valle Fertil 范围的收缩变形。关键结果是，为横截面计算的总缩短量 66 公里（35%）明显小于先前提出的，并且 Precordillera 褶皱冲断带的拆离更浅（~6.5 公里） vs 16 公里）比以前的型号。这最后一点使我们能够将前科迪勒拉山脉与前科迪勒拉山脉连接起来，如前所述，具有分离的斜坡平面几何形状，但同时允许下沉和在罗迪欧-伊格莱西亚盆地中观察到的几何形状的生成。为横截面计算的 66 公里（35%）明显小于先前提出的，并且 Precordillera 褶皱冲断带的脱离比以前的模型更浅（~6.5 公里对 16 公里）。这最后一点使我们能够将前科迪勒拉山脉与前科迪勒拉山脉连接起来，如前所述，具有分离的斜坡平面几何形状，但同时允许下沉和在罗迪欧-伊格莱西亚盆地中观察到的几何形状的生成。为横截面计算的 66 公里（35%）明显小于先前提出的，并且 Precordillera 褶皱冲断带的脱离比以前的模型更浅（~6.5 公里对 16 公里）。最后一点使我们能够将前科迪勒拉山脉与前科迪勒拉山脉连接起来，如前所述，具有分离的斜坡平面几何形状，但同时允许下沉和在罗迪欧-伊格莱西亚盆地中观察到的几何形状的生成。