Abstract

The study of the distribution law and origin of groundwater in Quaternary sediments downstream of the Red River Delta is approached in the direction of research on sequence stratigraphy and the distribution law of lithofacies according to space and time. However, the distribution law of lithofacies and groundwater depends on global sea-level changes and tectonic activities as the two most important reasons. Quaternary sediments of the Red River delta downstream have 5 sediment cycles corresponding to 5 sequences: (1) sequence 1 with Early Pleistocene age (Sq₁–\({\text{Q}}_{1}^{1}\)); (2) sequence 2 with early Middle Pleistocene age (Sq₂–\({\text{Q}}_{1}^{{2{\text{a}}}}\)); (3) sequence 3 with late middle Pleistocene age (Sq₃–\({\text{Q}}_{1}^{{2{\text{b}}}}\)); (4) sequence 4 with early Pleistocene age (Sq₄–\({\text{Q}}_{1}^{{3{\text{a}}}}\)); (5) sequence 5 with late Pleistocene–Holocene age (Sq₅–\({\text{Q}}_{1}^{{3{\text{b}}}}\)–Q₂). Each sequence is composed of three sedimentary systems tracts. The lowstand systems tract (LST) is characterized by a lowstand alluvial muddy sand facies complex that acts as a primary freshwater aquifer (S_marLST). The transgressive systems tract (TST) is characterized by a coastal swamp sand mud facies (M_samtTST) and a maximum transgression bay-lagoon mud facies (MmtTST) acting as an aquifuge. The highstand systems tract (HST) is characterized by sand bar facies (SamhHST) and delta plain sandy mud facies (M_samhHST). Thus, vertically Pleistocene sediments have 5 aquifers, in which each aquifer is constituted by the superposition of two successive facies complex: (1) upper part: lowstand alluvial gravelly sand facies complex (LST) and (2) lower part: highstand dune sand bar facies complex (SarLST/SamhHST). The spatial distribution of freshwater aquifers in 3 provinces Northwest Thai Binh, Ninh Binh—southeast Nam Dinh, and northwest Nam Dinh demonstrate the absence of shallow marine-bay mud facies.

中文翻译：

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红河三角洲下游地区第四纪沉积层序地层与地下水与全球海平面变化的关系

摘要

红河三角洲下游第四纪沉积物中地下水的分布规律和成因研究，朝着层序地层学和岩相时空分布规律的研究方向展开。然而，岩相和地下水的分布规律取决于全球海平面变化和构造活动这两个最重要的原因。红河三角洲下游第四纪沉积物有 5 个沉积旋回，对应 5 个序列：（1）序列 1，早更新世年龄（Sq ₁ – \({\text{Q}}_{1}^{1}\)） ; (2) 中更新世早期的序列 2 (Sq ₂ – \({\text{Q}}_{1}^{{2{\text{a}}}}\) )；(3) 层序 3 中更新世晚期 (Sq₃ – \({\text{Q}}_{1}^{{2{\text{b}}}}\) ); (4) 更新世早期的序列 4 (Sq ₄ – \({\text{Q}}_{1}^{{3{\text{a}}}}\) )；(5) 具有晚更新世-全新世年龄的序列 5 (Sq ₅ – \({\text{Q}}_{1}^{{3{\text{b}}}}\) –Q ₂ )。每个层序由三个沉积系统域组成。低水位系统域 (LST) 的特点是低水位冲积泥砂相复合体，作为初级淡水含水层 (S _m arLST)。海侵体系域（TST）以海岸沼泽砂泥相（M _samtTST) 和最大海侵海湾-泻湖泥相 (MmtTST) 作为隔水层。高位体系域（HST）以砂坝相（SamhHST）和三角洲平原砂质泥相（M _s amhHST）为特征。因此，垂直更新世沉积物有 5 个含水层，其中每个含水层由两个连续相复合体的叠加构成：（1）上部：低位冲积砾砂相复合体（LST）和（2）下部：高位沙丘砂坝相复合体（SarLST/SamhHST）。太平西北部、宁平—南定东南、南定西北部 3 省淡水含水层空间分布表明不存在浅海湾泥相。