Structural style of the Guañacos Fold and Thrust Belt (southern Central Andes): A tectonic setting for the Cura Mallín Basin revisited

IF 2.7 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Lucía Jagoe , Martín Turienzo , Lucía Sagripanti , Natalia Sánchez , Andrés Folguera
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引用次数: 0

Abstract

The tectonic setting of the Oligo-Miocene Cura Mallín Basin in the southern Central Andes has been a topic of debate in recent years. Proposed models include extensional, compressional, and a hybrid-sequential model with an initial extension (∼20 Ma) followed by contraction (∼19 Ma). We conducted a detailed structural analysis to understand the tectonic evolution of the Cura Mallín Basin at the eastern Andean slope in the Guañacos Fold and Thrust Belt (FTB) (37°-38°S). This tectonic element provides exceptional exposure of the upper sedimentary infill of the Cura Mallín Basin. Despite detailed studies about composition, the structural configuration of this basin remains poorly understood. This study refines the age of the upper Cura Mallín Formation on the eastern Andean slope with a new detrital U/Pb date of 15.47 ± 0.28 Ma from the basal portion of the sedimentary sequence, indicating a maximum Middle Miocene deposition, in contrasts with the previous Oligo-Miocene age. This work presents the first balanced cross-sections for the Guañacos FTB. Structural analysis reveals a thin-skinned deformation style, contrasting with previous interpretations of thick-skinned deformation, with shortenings of 9.6 km (29 %) and 8.5 km (24 %). Therefore, significant Andean contraction at these latitudes was absorbed by the Guañacos FTB. Our model assumes that all deformation in the Cura Mallín Formation postdates deposition. Contractional deformation began on the Chilean Andean slope by ∼18.7 Ma, jumped to the Argentinean side at ∼12.5 Ma, and persisted beyond 6.5 Ma, with progressively diminishing intensity. Combined evidence from the Guañacos FTB and the eastern Chos Malal FTB, suggests synchronous deformation throughout the entire orogen during the Late Miocene. Additionally, these two belts record the reactivation of Miocene thrust faults during the Quaternary. This reactivation is potentially linked to the apparent persistence of the regional stress field since the Late Miocene.
Guañacos褶皱冲断带(中安第斯山脉南部)的构造样式:古拉Mallín盆地的构造背景重新考察
中安第斯山脉南部渐近-中新世库拉Mallín盆地的构造背景是近年来争论的一个话题。提出的模型包括伸展、压缩和混合序列模型,初始伸展(~ 20 Ma)随后是收缩(~ 19 Ma)。为了解Guañacos褶皱冲断带(FTB)(37°-38°S)东安第斯斜坡上Cura Mallín盆地的构造演化,进行了详细的构造分析。这一构造元素提供了库拉Mallín盆地上部沉积充填物的特殊暴露。尽管对其组成进行了详细的研究,但对该盆地的构造形态仍知之甚少。本研究对安第斯东部斜坡上库拉Mallín组的年龄进行了修正,从沉积序列的基底部分得到新的碎屑U/Pb年龄为15.47±0.28 Ma,与之前的渐新-中新世形成对比,表明中中新世沉积最大。这项工作提出了Guañacos FTB的第一个平衡截面。构造分析揭示了一种薄皮变形类型,与之前对厚皮变形的解释形成对比,缩短了9.6公里(29%)和8.5公里(24%)。因此,这些纬度显著的安第斯山脉收缩被Guañacos FTB吸收。我们的模型假设库拉Mallín组的所有变形都是在沉积之后发生的。收缩变形在~ 18.7 Ma时开始于智利安第斯斜坡,在~ 12.5 Ma时跳到阿根廷一侧,并持续超过6.5 Ma,强度逐渐减弱。结合Guañacos断裂带和东Chos Malal断裂带的证据,表明晚中新世整个造山带发生了同步变形。此外,这两条带还记录了第四纪中新世逆冲断层的再活动。这种重新激活可能与晚中新世以来区域应力场的明显持续有关。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Tectonophysics
Tectonophysics 地学-地球化学与地球物理
CiteScore
4.90
自引率
6.90%
发文量
300
审稿时长
6 months
期刊介绍: The prime focus of Tectonophysics will be high-impact original research and reviews in the fields of kinematics, structure, composition, and dynamics of the solid arth at all scales. Tectonophysics particularly encourages submission of papers based on the integration of a multitude of geophysical, geological, geochemical, geodynamic, and geotectonic methods
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