Tide-dominated sedimentation in the upper Tertiary succession of the Sitapahar anticline, Bangladesh
Alam, M.M. (1995). Tide-dominated sedimentation in the upper Tertiary succession of the Sitapahar anticline, Bangladesh, in: Flemming, B.W. et al. (Ed.) Tidal Signatures in Modern and Ancient Sediments. Special Publication of the International Association of Sedimentologists, 24: pp. 329-341
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., meer
In: Special Publication of the International Association of Sedimentologists. Blackwell: Oxford. ISSN 0141-3600; e-ISSN 2054-6610, meer
|
| Abstract |
The Baraichari Shale Formation (Late Miocene-Pliocene) in the Upper Tertiary elastic succession of the Sitapahar anticline, south-eastern fold belt of the Bengal Basin, displays a spectrum of tidedominated facies. The fine-grained facies association (FFA), predominant in the upper and lower members of the formation, has mud- to sand-rich components and contains shale (sometimes sand/silt-streaked), lenticular-, wavy-, and flaser-bedded units and rippled siltstone. Fining-upward (FU) cycles and random intercalations are common, while coarsening-upward followed by finingupward (CUFU) cycles are rare within the FFA. The medium-grained facies association (MFA), characterizing the middle member of the formation, comprises fine- and medium-grained, crossbedded flat- and ripple-laminated sandstones with minor siltstone and shale intercalations. The MFA is interpreted to represent migrating sandy shoals in a moderate energy, shallow-water subtidal environment. The shoals are developed in areas of most intensive and concentrated tidal energy. The FFA represents an intertidal environment, with the mud- and sand-rich components accumulating in the upper and lower intertidal subenvironments, respectively. The FU cycles have been developed by progradation of the tidal flats, their thicknesses probably being related to the tidal range at the time of deposition. Large-scale alternations of MFA and FFA in the Baraichari Shale Formation are interpreted as resulting from minor transgressive and regressive phases during the overall regional regression in the south-eastern Bengal Basin. In the wake of subsequent tectonic upheavals, coupled with a regional regression, deposition of the coarse-grained facies association (CFA) of the Chandraghona Sandstone Formation took place in an essentially flu vial environment. |
|
