Combined ^(40)Ar/^(39)Ar and (U–Th)/He geochronological constraints on long-term landscape evolution of the Second Paraná Plateau and its ruiniform surface features, Paraná, Brazil
Combined ^(40)Ar/^(39)Ar and (U–Th)/He geochronological constraints on long-term landscape evolution of the Second Paraná Plateau and its ruiniform surface features, Paraná, Brazil
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DOI：
10.1016/j.geomorph.2014.10.041
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发表时间：
2015-03
期刊：
影响因子：
3.9
通讯作者：
S. Riffel;P. Vasconcelos;I. Carmo;K. Farley
中科院分区：
文献类型：
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作者：
S. Riffel;P. Vasconcelos;I. Carmo;K. Farley
测年风化陆地表面的区域相关性为测试长期大陆景观演化模型提供了必要的约束，但对这些表面进行正确测年仍然存在重大挑战。巴西巴拉那州第二巴拉那高原的地貌省是一个高海拔（约 800 米）陆地表面，其特征是广泛分布的深层腐泥土和分散的红土剖面（例如，Vila Velha 和 Serra das Almas）。长期暴露在风化和侵蚀之下，形成了该地貌特有的拟喀斯特和废墟状特征。在这项研究中，对 Vila Velha 红土剖面的 22 个表生 Mn 羟基氧化物颗粒进行 40Ar/39Ar 激光增量加热地质年代学，得出的结果范围为 17.2 ± 0.7 至 9.1 ± 0.7 Ma。对同一剖面的 28 颗针铁矿颗粒进行的 (U–Th)/He 地质年代学得出的结果范围为 36.4 ± 3.6 至 1.0 ± 0.1 Ma，年龄组位于 17.2 ± 0.7 至 7.9 ± 0.8 Ma 区间内。对距维拉维尔哈 20 公里的 Serra das Almas 红土剖面中的 17 颗针铁矿颗粒进行 (U–Th)/He 地质年代学，得出的结果范围为 35.1 ± 3.5 到 14.1 ± 1.4 Ma。两个地点的综合结果揭示了大约开始于大约 1970 年的共同风化历史。 35 Ma，表明第二巴拉那高原是由约 35 Ma 之前的区域河流切割和剥蚀造成的，随后是剥蚀率下降和相应更强烈的风化作用。与红土剖面中央年龄一致，风化作用在中新世（17-8Ma）期间特别强烈。上新世之后，剥蚀加剧。
Regional correlation of dated weathered land surfaces provides the necessary constraints to test long-term continental landscape evolution models, but major challenges remain in properly dating these surfaces. The geomorphological province of Second Paraná Plateau, Paraná State, Brazil, is a high elevation (ca. 800 m) land surface characterized by widely distributed deep saprolites and scattered lateritic profiles (e.g., Vila Velha and Serra das Almas). Prolonged exposure to weathering and erosion has promoted the pseudo-karstic and ruiniform features that are characteristic of this landscape. In this study,40Ar/39Ar laser incremental heating geochronology on 22 grains of supergene Mn oxyhydroxides from lateritic profiles at Vila Velha yielded results ranging from 17.2 ± 0.7 to 9.1 ± 0.7 Ma. (U–Th)/He geochronology on 28 goethite grains from the same profile yielded results ranging from 36.4 ± 3.6 to 1.0 ± 0.1 Ma, with an age cluster lying within the 17.2 ± 0.7 to 7.9 ± 0.8 Ma interval. (U–Th)/He geochronology on 17 goethite grains from the Serra das Almas lateritic profile, located 20 km from Vila Velha, yield results ranging from 35.1 ± 3.5 to 14.1 ± 1.4 Ma. The combined results for the two sites reveal a common weathering history that started ca. 35 Ma, suggesting that the Second Paraná Plateau results from regional fluvial incision and denudation before ~ 35 Ma, followed by a decline in denudation rates and proportionally more intense weathering. Consistent with the laterite profile central ages, weathering was particularly intense during the Miocene (17–8 Ma). Denudation intensified after the Pliocene.