Record of Early Cretaceous dinoflagellate cysts from well JM-A, Dhansiri Valley of Upper Assam Shelf, India

IF 0.5 4区 地球科学 Q4 PALEONTOLOGY
Divya Geddada, Kanchi Narsimha
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引用次数: 0

Abstract

A palynological study on subsurface Early Cretaceous sediments (1550–1860 m) in well JM-A located in Dhansiri Valley, Upper Assam Shelf has been carried out for determination of age and depositional environment. The palynological investigations resulted into the identification of the characteristic and diversified occurrence of Early Cretaceous dinoflagellate cysts comprising Batioladinium micropodum, Achomosphaera? neptuni, Batiacasphaera asperata, Lagenorhytis sp. cf. L. delicatula, Mendicodinium caperatum and Canningia sp. along with associated dinoflagellate cysts. The significant assemblage of spore-pollen assemblage represented by Cicatricosisporites australiensis, Ceratosporites equalis, Gleicheniidites circinidites, Contignisporites cooksonii, Microcachryidites antarcticus, Podosporites tripakshii and Callialasporites trilobatus has also been recorded. The Early Cretaceous sediments are regarded as Bamangaon Formation in Dhansiri Valley. The occurrence of dinoflagellate cysts suggests marginal marine environment for Bamangaon Formation deposited during the Early Cretaceous period corresponding to the Rift Phase. The Formation overlies the Metamorphic Basement Complex, and it is unconformably overlain by the sediments of Tura Formation of Ypresian (Early Eocene) age, deposited under subtidal to inner shelf environment during the Passive Margin Tectonic Phase.
印度上阿萨姆大陆架丹斯里谷 JM-A 井记录的早白垩世甲藻囊胞
为确定年代和沉积环境,对位于上阿萨姆邦大陆架丹斯里河谷的 JM-A 井的地下早白垩世沉积物(1550-1860 米)进行了古植物学研究。通过古植物学调查,确定了早白垩世甲藻囊虫的特征和多样性,包括 Batioladinium micropodum、Achomosphaera? neptuni、Batiacasphaera asperata、Lagenorhytis sp.cf.L.delicatula、Mendicodinium caperatum 和 Canningia sp.以及相关的甲藻囊虫。此外,还记录了以 Cicatricosisporites australiensis、Ceratosporites equalis、Gleicheniidites circinidites、Contignisporites cooksonii、Microcachryidites antarcticus、Podosporites tripakshii 和 Callialasporites trilobatus 为代表的大量孢粉组合。早白垩世沉积物被认为是丹斯里河谷的巴曼岗地层。甲藻孢囊的出现表明,巴曼加翁地层沉积于早白垩世时期的裂谷期,处于边缘海洋环境。该地层覆盖在变质基底复合地层之上,与被动边缘构造相期间沉积在潮下到内陆架环境下的伊普雷时代(始新世早期)的图拉地层沉积物形成不整合覆盖。
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来源期刊
CiteScore
1.10
自引率
16.70%
发文量
0
期刊介绍: The journal is devoted to the publication of original papers and review articles dealing with all aspects of Paleontology, Paleobotany, Stratigraphy, Geochronology, Anthropology and Pre-history.
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