Evidence of tidal influence in the Murree Group of rocks of the Jammu Himalaya, India
Singh, B.P.; Singh, H. (1995). Evidence of tidal influence in the Murree Group of rocks of the Jammu Himalaya, India, in: Flemming, B.W. et al. (Ed.) Tidal Signatures in Modern and Ancient Sediments. Special Publication of the International Association of Sedimentologists, 24: pp. 343-351 In: Flemming, B.W.; Bartholomä, A. (Ed.) (1995). Tidal Signatures in Modern and Ancient Sediments. Special Publication of the International Association of Sedimentologists, 24. Blackwell Science: Oxford. ISBN 0-86542-978-2. 358 pp., more In: Special Publication of the International Association of Sedimentologists. Blackwell: Oxford. ISSN 0141-3600; e-ISSN 2054-6610, more |
| Abstract | The sediments of the Murree Group form a broad rim in the inner Tertiary belt of the Himalaya, extending from the Jhelum syntaxis to the Jammu foothills on the Indian subcontinent. The Murree foreland basin, in which the sediments from the Himalayan uplifts have accumulated, was formed as a result of the early Tertiary Himalayan Orogeny. Recent palaeomagnetic and palaeontologoic studies have revealed that these sediments were deposited in the late Eocene-early Miocene. The present study is confined to the Murree Group of rocks exposed along the Jammu-Srinagar highway (north of Udhampur) and deals with the depositional environments in relation to lithofacies and their organization, sedimentary structures, trace fossils and palaeocurrent patterns. Lithologically, the Murree Group of rocks has been divided into a Lower Murree Formation, exhibiting a cyclic sandstone-siltstone-mudstone sequence, and an Upper Murree Formation with sandstone-mudstone cycles. The individual cycles in the Lower Murree start with an erosional base, followed by channel-lag conglomerates, cross-bedded sandstones with thin mud flasers and massive sandstones. The latter are overlain by laminated sandstones displaying ripples, massive sandstones and mudstone-siltstone intercalations. In the upper Murree Formation, the arrangement of the rock units changes with a general increase of sandstone fades as compared to mudstone facies. The absence of siltstone facies is a characteristic feature in the Upper Murree Formation. The presence of strongly bioturbated, pebbly conglomerates and cross-bedded sandstones with thin mud !lasers indicates deposition in a subtidal environment. The sandstone-mudstone intercalations along with laminated siltstones represent a mixed tidal flat sequence deposited in the intertidal zone. The presence of herringbone cross-bedding in the Lower Murree sandstones further enhances the evidence for tidal influence during the accumulation of these sediments. The sole marks (groove casts and flute casts) at the base of the cycles of the Lower Murree rocks indicate their formation in tidal channels. The bifurcated, straight-crested asymmetrical, linguoid starved ripples in the Lower as well as the Upper Murree rocks substantiate the tidal origin of these rocks. Wrinkle marks indicate intertidal emergence of the sediments. Vertical burrows point towards deposition in a shallow-water environment. Palaeocurrent patterns are bimodal and in part bipolar. On the basis of this evidence an estuarine depositional environment with strong tidal influence is suggested for the Murree Group of rocks. |
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