Origin and geochemical characterization of the glauconites in the Upper Cretaceous Lameta Formation, Narmada Basin, central India

作     者：Udita Bansal Santanu Banerjee Dhiren K.Ruidas Kanchan Pande 

作者机构：Department of Earth Sciences Indian Institute of Technology Bombay 

出 版 物：《Journal of Palaeogeography》 (古地理学报（英文版）)

年 卷 期：2018年第7卷第2期

页      面：99-116页

核心收录：

学科分类：0303[法学-社会学] 0710[理学-生物学] 0709[理学-地质学] 07[理学] 0708[理学-地球物理学] 0705[理学-地理学] 0815[工学-水利工程] 0813[工学-建筑学] 0833[工学-城乡规划学] 

基　　金：Ministry of Mines  Government of India for financial support through grant F No. 14/77/2015Met. IV 

主　　题：Glauconite Estuary Mineral chemistry Cerium anomaly Redox condition Lameta Formation Narmada Basin 

摘      要：This study presents geochemical characteristics of glauconites in estuarine deposits within the Maastrichtian Lameta Formation in central India. Resting conformably over the Bagh Group, the Lameta Formation consists of ~4-5 m thick arenaceous, argillaceous and calcareous green sandstones underlying the Deccan Traps. The sandstone is friable, medium-to coarse-grained, well-sorted and thoroughly crossstratified, and contains marine fossils. Detailed petrography, spectroscopy and mineral chemistry indicates unique chemical composition of glauconite with high KO, MgO, AlOand moderate TFeO. Glauconite is formed by the replacement of K-feldspars, initially as stringers in the cleavages and fractures of feldspars. Incipient glauconite subsequently evolves fully, appearing as pellets. Fully-evolved glauconite pellets often leave tiny relics of K-feldspar. XRD exhibits characteristic peak of 10A from basal(001)reflection of glauconite, indicating the evolved character. The KO content of glauconites in the Lameta Formation varies from 5.51% to 8.29%, corroborating the evolved to highly-evolved maturation *** TFeOcontent of glauconite varies from 12.56% to 18.90%. The PASS-normalized-REE patterns of glauconite exhibit a hat-shape confirming the authigenic origin of glauconites. The slightly-negative to slightly-positive Ce anomaly value and the moderate TFeOcontent of glauconite agree well with a suboxic,estuarine condition. The replacement of K-feldspar by the glauconite contributes towards the high KO content. Compositional evolution of glauconites in the Lameta Formation is similar to those observed in many Precambrian sedimentary sequences.