Rising sea-levels in tectonically active epicontinental basins often lead to varied depositional settings and palaeogeography, mostly influenced by the net accommodation resulting from mutual interference of the extent and nature of landward encroachment by the sea and the net sedimentation. The Cenomanian Nimar Sandstone Formation, Bagh Group, Narmada rift basin, uniquely portrays the effect of sea-level rise within an intra-cratonic setting and attributes to the corresponding palaeogeographic changes in west-central India. An integrated sedimentological–sequence-stratigraphic study of the broadly fining-upward Nimar Sandstone Formation (thickness ~ 20–30 m) depicts the actual nature of changeover from a fluvial to a marine-dominated transitional depositional setting. Detailed sedimentological study reveals total seventeen facies, grouped in five facies associations, viz., the channel-fill facies association (FA-1), the overbank facies association (FA-2), the fluvial-dominated fluvio-tidal facies association (FA-3), the tide-dominated fluvio-tidal facies association (FA-4), and the shoreface facies association (FA-5). Overall facies architecture indicates a west-to-eastward marine encroachment, resulting in stacking of three distinct palaeo-depositional conditions: (i) an initial fluvial system with channel and overbank, changing into a tide-influenced fluvial bay-head delta in the inner estuary, followed by (ii) marine encroachment leading to a tide-dominated central estuary with inter- to sub-tidal settings, and finally, (iii) with further intense marine encroachments, a wave-reworked open shore condition in the outer estuary zone. The overall fining-up succession with a systematic change from fluvial to marine-dominated depositional systems points to a landward shift of the shoreline, signifying a major transgressive event correlated to the Cenomanian global sea-level rise. Characteristic stratal stacking patterns point to four coarsening- and fining-up hemicycles, embedded within the major transgressive succession. These high-frequency cycles attest to the varied interplay of sedimentation, tectonics and sea-level changes, and the resultant net accommodations. A palaeogeographic model is proposed based on the high-frequency transgressive–regressive hemicycles, which envisages the evolution of the depositional environments in relation to the Cenomanian eustatic rise in the intra-cratonic riftogenic fluvio-marine transitional basinal setup.

中文翻译：

---

印度纳尔马达裂谷盆地河-海过渡系统的古地理重建——对晚白垩世全球海平面上升的影响

构造活跃的陆上盆地的海平面上升通常会导致不同的沉积环境和古地理，主要受海洋向陆侵占的范围和性质与净沉积相互干扰导致的净容纳的影响。Narmada 裂谷盆地 Bagh Group 的 Cenomanian Nimar 砂岩组独特地描绘了克拉通内环境中海平面上升的影响，并归因于印度中西部相应的古地理变化。对广泛向上向上的 Nimar 砂岩组（厚度 ~ 20-30 m）进行的综合沉积学-层序-地层研究描述了从河流到海洋主导的过渡沉积环境转变的实际性质。详细的沉积学研究揭示了总共十七个相，分为五个相协会，即，河道充填相协会（FA-1），河岸相协会（FA-2），河流主导的潮汐相协会（FA-3），潮汐主导的潮汐相协会 (FA-4) 和滨面相协会 (FA-5)。整体相结构显示出自西向东的海洋侵蚀，导致三种不同的古沉积条件叠加：(i) 具有河道和堤岸的初始河流系统，在内陆转变为受潮汐影响的河流湾头三角洲河口，然后是 (ii) 海洋侵蚀导致潮间带至潮下环境的潮汐主导的中央河口，最后，(iii) 进一步强烈的海洋侵蚀，在外河口区形成波浪改造的开放海岸条件. 从河流沉积系统到海洋主导沉积系统的系统性变化的整体整理序列表明海岸线向陆地移动，这表明与森诺曼尼亚全球海平面上升相关的重大海侵事件。特征地层堆积模式指向四个粗化和细化的半旋回，嵌入在主要的海侵序列中。这些高频循环证明了沉积、构造和海平面变化的不同相互作用，以及由此产生的净适应。提出了一个基于高频海进-海退半环体的古地理模型，该模型设想了与克拉通内裂谷成因河-海过渡盆地设置中的森诺曼阶海平面上升相关的沉积环境的演变。