Effective grain size distribution analysis for interpretation of tidal–deltaic facies: West Bengal Sundarbans

Abstract

This is an open access article published under a Creative Commons Attribution-NonCommercial-NoDerivs License (https://creativecommons.org/licenses/by-nc-nd/4.0/), which permits distribution and reproduction for non-commercial purposes, provided the author and source are cited. General rightsCopyright for the publications made accessible via the Queen's University Belfast Research Portal is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights.Take down policy The Research Portal is Queen's institutional repository that provides access to Queen's research output. Every effort has been made to ensure that content in the Research Portal does not infringe any person's rights, or applicable UK laws. If you discover content in the Research Portal that you believe breaches copyright or violates any law, please contact openaccess@qub.ac.uk. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. lithofacies; Sundarbans; Ganges-Brahmaputra delta. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT AbstractResearch over the past two decades on the Holocene sediments from the tide dominated west side of the lower Ganges delta has focussed on constraining the sedimentary environment through grain size distributions (GSD). GSD has traditionally been assessed through the use of probability density function (PDF) methods (e.g. log-normal, log skew-Laplace functions), but these approaches do not acknowledge the compositional nature of the data, which may compromise outcomes in lithofacies interpretations. The use of PDF approaches in GSD analysis poses a A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT 2 series of challenges for the development of lithofacies models, such as equifinal distribution coefficients and obscuring the empirical data variability. In this study a methodological framework for characterising GSD is presented through compositional data analysis (CODA) plus a multivariate statistical framework. This provides a statistically robust analysis of the fine tidal estuary sediments from the West Bengal Sundarbans, relative to alternative PDF approaches.

Seasonal Variability of Forces Controlling Sedimentation in the Sundarbans National Forest, Bangladesh

“…Interestingly, the deposition rates determined by this and other recent studies (e.g., Rogers et al, 2013;Auerbach et al, 2015;Bomer et al, in review) are similar to the local deposition rates observed across the entire Holocene (0.7-1.0 cm/year; Ayers et al, 2016). Further to the west, where sedimentation has been reduced as a result of the eastward migration of the Ganges River over the past 4000 years, the longterm deposition rates are closer to 0.1-0.2 cm/year (Flood et al, 2015). It would be an oversimplification to imply that this spatial variability stems exclusively from a moving sediment supply.…”

“…This study will focus on a portion of the Sundarbans National Forest (SNF), a relatively pristine mangrove forest located in southwestern Bangladesh (Figure 1). The total extent of the Sundarbans reaches across political boundaries into India, expressing a continuum of fluvial and tidal forces with increased distance from the modern Ganges-Brahmaputra-Meghna River mouth (Allison and Kepple, 2001;Rogers et al, 2013;Flood et al, 2015Flood et al, , 2018. Immediately to the north of the SNF is an inhabited region where the construction of earthen embankments ("polders") has resulted in a substantial modification of the tidal prism, leading to tidal amplification and extensive network reorganization (e.g., Pethick and Orford, 2013;Wilson et al, 2017).…”

Compositional data analysis of Holocene sediments from the West Bengal Sundarbans, India: Geochemical proxies for grain-size variability in a delta environment

“…The overarching trend would suggest a strong relationship between zirconium and 692 coarse grained sediment, as these sites are considered to reflect upward fining sequences 693 (e.g., Allison et al, 2003;Flood et al, 2015). In particular the trend consists of 694 coarse/very coarse-silt and sand with a concomitant relationship between coarse clay and 695 medium/coarse-silt for rubidium.…”

Analyzing coastal environments by means of functional data analysis

“…Particlesize determinations are common practice in powder technology, which includes several chemical and industrial activities (Burgess et al, 2004;Allen, 2013). However, such measurements are not limited to industrial purposes alone as they have various applications in the earth sciences (e.g., Sahu, 1964;Weltje and von Eynatten, 2004;Flood et al, 2015).…”