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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >A base-level stratigraphic approach to determining Holocene subsidence of the Ganges-Meghna-Brahmaputra Delta plain
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A base-level stratigraphic approach to determining Holocene subsidence of the Ganges-Meghna-Brahmaputra Delta plain

机译：确定全新世地区岩土沉降的基础地层方法 - 狂热沉降 - Brahmaputra Lelta平原

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Relative sea level history, which is the result of the combined effects of land subsidence, sediment supply and absolute sea level history may be reconstructed from preserved sediment thicknesses. However, variations in the preserved sediment thicknesses between different sedimentary environments strongly limit the accuracy of this type of geological approach, particularly in fluvial channelized systems, such as delta plains. To address this, we apply three different and independent stratigraphic approaches to the case of the Ganges-Brahmaputra-Meghna Delta (GBMD). Our approach has been made possible by a broad dataset of geological archives we have collected, which includes more than 400 hand-drilled stratigraphic wells, 198 radiocarbon ages, and river seismic reflection data (255 km of high-resolution multichannel seismic images). The seaward gradient of accommodation and the limit of the subsiding delta plain are estimated, assuming that the delta is near or at the base-level, which is considered to be the relative sea-level. First, a statistical analysis of the variability of preserved sediment thicknesses is used to derive the average pattern of accommodation from the Holocene isopach. Secondly, the preserved sediment thicknesses are analyzed by geomorphotectonic domains to estimate an average pattern of accommodation. Thirdly, the burial history of the seismically imaged last glacial incision of the Brahmaputra River is reconstructed. Results suggest that the variability of preserved sediment thicknesses can be up to 35% in a delta plain between river channel and flood plain deposits for the same relative sea-level history. Taking this variability into consideration, the Holocene relative sea-level history of the GBMD and the most likely pattern of subsidence are determined. Results provide evidence of moderate Holocene subsidence over the delta, gently increasing seaward from 0.2 mm/yr landward of the Hinge Zone, which can be considered as the northern li
机译：相对海平面历史，这是土地沉降，沉积物和绝对海平面历史的综合影响的结果可以从保存的沉积物厚度重建。然而，不同沉积环境之间的保存沉积物厚度的变化强烈限制了这种地质方法的准确性，特别是在河流通道化系统中，例如Δ平原。为了解决这个问题，我们将三种不同和独立的地层方法应用于Ganges-Brahmaputra-Meghna Delta（GBMD）的情况。我们的方法是由我们收集的地质档案的广泛数据集实现，其中包括400多家手工钻石地层井，198年以上的RadioCarbon年龄和河流地震反射数据（距离高分辨率多通道地震图像255公里）。假设Δ接近或在基础上，估计了住宿的海面梯度和沉降的δ平原的极限，被认为是相对海平面。首先，对保存沉积物厚度的变化的统计分析用于从全茂伊索普拉克获得平均住宿模式。其次，通过地理胶质域分析保存的沉积物厚度，以估计平均住宿模式。第三，重建了Brahmaputra河的地震成像最后冰川切口的埋葬历史。结果表明，在相同海平面历史的河流通道和洪水平原沉积物之间的三角洲平原中，保存沉积物厚度的可变性可以高达35％。考虑到这种可变性，全新世 - 英雄的相对海平历史和最可能的沉降模式。结果提供了对三角洲的中等全新世沉降的证据，从而从铰链区的落地落地时轻轻增加海洋，这可以被视为李北部

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