Deciphering the crustal architecture of the Cretaceous Barmer-Sanchore Basin (BSB) and Neoproterozoic provinces in the NW Indian Shield presents significant challenges due to extensive sediment deposition and widespread felsic igneous rocks. To address such intricacies, we employ a transdimensional Bayesian joint inversion of teleseismic P-wave polarizations and receiver functions to resolve the detailed structure of the upper 10 km of the crust beneath 29 seismic stations deployed in the study area. The new data is analyzed separately within each of the three different backazimuthal groups to identify any strong variations in the shallow subsurface structure and derive a more robust, averaged model for every station site. The resulting 1-D models reveal heterogeneous sediment cover in BSB and Marwar Basin, with respective thicknesses ranging from ∼1.3–5.5 km and 1–1.5 km. Remarkably low shear-wave velocities (Vs < 1.0 km/s) of sediments with increased Vp/Vs (>2.3) are observed in BSB and adjacent areas, which are related to highly unconsolidated Quaternary-Tertiary deposits. The Marwar Basin is imaged to have 0.3–0.5 km of uncompacted sediments that overlie 0.5–1 km thick Marwar Supergroup sequence. The Erinpura Granites (EG) and Malani Igneous Province (MIP) are characterized by a variably thick sediment blanket, typically ranging within 1 km in thickness. The Vs of the sediments in these regions exceeds 2.4 km/s that possibly corresponds to Mesozoic and older sediments. The basement beneath EG exhibits Vs faster than 3.4 km/s, consistent with moderately metamorphosed granites. In MIP, the basement is characterized by non-uniform shear velocities, suggesting the influence of intrusions linked to magmatic episodes in NW India.

中文翻译：

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使用贝叶斯方法从远震 P 波尾波对西北印度地体下方的浅地壳进行成像


由于广泛的沉积物沉积和广泛的长英质火成岩，破译白垩纪巴尔默-桑乔雷盆地（BSB）和印度地盾西北部新元古代省的地壳结构面临着巨大的挑战。为了解决这些错综复杂的问题，我们采用远震 P 波偏振和接收器函数的跨维贝叶斯联合反演来解析研究区域部署的 29 个地震台下方地壳上部 10 公里的详细结构。新数据在三个不同的方位角组中分别进行分析，以识别浅层地下结构中的任何强烈变化，并为每个站址得出更稳健的平均模型。由此产生的一维模型揭示了 BSB 和 Marwar 盆地的异质沉积物覆盖，厚度分别为 ∼1.3–5.5 km 和 1–1.5 km。在 BSB 和邻近地区观察到沉积物的剪切波速度非常低（Vs < 1.0 km/s），而 Vp/Vs (>2.3) 增加，这与高度松散的第四纪-第三纪沉积物有关。据成像，马尔瓦尔盆地有 0.3-0.5 公里长的未压实沉积物，覆盖在 0.5-1 公里厚的马尔瓦尔超群层序之上。埃林普拉花岗岩 (EG) 和马拉尼火成岩省 (MIP) 的特点是沉积层厚度不一，通常厚度在 1 公里以内。这些地区沉积物的 Vs 超过 2.4 km/s，可能对应于中生代和更古老的沉积物。 EG 下方的基底表现出速度超过 3.4 公里/秒，与中度变质花岗岩一致。在 MIP 中，基底的特征是剪切速度不均匀，这表明与印度西北部岩浆活动有关的侵入的影响。