Insight to the geological character of the Early Triassic strata in the Western Salt Range, Pakistan: A comparative study,Geological Journal

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Insight to the geological character of the Early Triassic strata in the Western Salt Range, Pakistan: A comparative study
Geological Journal ( IF 1.4 ) Pub Date : 2021-06-24 , DOI: 10.1002/gj.4204
Abdus Saboor _{1,

2} , Moin Haq ₁ , Abid Nawaz ₁ , Muhammad Azhar Farooq Swati ₁ , Jamal Gohar ₁ , Sohrab Khan ₁ , Abuzar Ghaffari ₁

Affiliation

The sedimentary strata along the Permian–Triassic Boundary in the Western Salt Range of the sub-Himalayas were analysed to gain an insight of its geological character regarding palaeoenvironments, palaeoclimate, and sequence stratigraphic attributes. The Early Triassic Mianwali Formation is dominated by shallow marine facies with transgressive phases, differentiation in facial character, and palaeowater depth among different sections. The study suggests that compared to the siliciclastic-dominated Nammal Gorge Section, the Zaluch Nala Section is more carbonate-dominated, representing algal-laminated limestones, dolomitic marls, and siliciclastics – mainly restricted to the Mittiwali Member. There is a general decrease in ammonoids and increase in thickness from east to west, that is believed to be due to algal-induced rapid sedimentation in the shallow marine environments as compared to deeper marine in the east. The Mianwali Formation has been deposited in two transgressive systems tracts, two highstand systems tracts, and one falling-stage regressive systems tract. Two flooding surfaces, one each in the Mittiwali and Narmia members, have been recognized. The maximum regressive surfaces at the bottom (with the Chhidru Formation) and top (with the Tredian Formation) mark second-order eustatic falls. The study also advocates for existence of a low-energy platform in the temperate waters of the Palaeo-Tethys. The sediments have similarities with various sections of Gondwanaland having the same trend of shallow marine facies and presence of algal-laminated deposits. In the Middle Triassic, the gradual loss of sediment binding organisms shifted the low-energy meandering patterns to high-energy braided systems.

中文翻译：

对巴基斯坦西部盐岭早三叠世地层地质特征的洞察：一项比较研究

分析了亚喜马拉雅山脉西部盐岭二叠纪-三叠纪边界的沉积地层，以了解其在古环境、古气候和层序地层属性方面的地质特征。早三叠世棉瓦里组以浅海相为主，海侵相，相特征分异，不同剖面古水深。研究表明，与以硅质碎屑为主的 Nammal 峡谷剖面相比，Zaluch Nala 剖面以碳酸盐为主，代表藻层灰岩、白云质泥灰岩和硅质碎屑——主要限于 Mittiwali 段。从东到西，菊石普遍减少，厚度增加，这被认为是由于与东部较深的海洋环境相比，浅海环境中藻类引起的快速沉积。棉瓦里组已沉积2个海侵体系域、2个高位体系域和1个降级海退体系域。已识别出两个洪水面，Mittiwali 和 Narmia 成员各有一个。底部（Chhidru 组）和顶部（Tredian 组）的最大回归表面标志着二级浮沉。该研究还主张在古特提斯群岛的温带水域存在一个低能量平台。沉积物与冈瓦纳大陆各剖面相似，具有相同的浅海相趋势和藻层状沉积物的存在。在中三叠世，

更新日期：2021-09-02

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