Abstract
ABSTRACTConstraining time is of critical importance to evaluating the rates and relative contributions of processes driving landscape change in sedimentary basins. The geomorphic character of the field setting guides the application of geochronologic or instrumental tools to this problem, because the viability of methods can be highly influenced by geomorphic attributes. For example, sediment yield and the linked potential for organic preservation may govern the usefulness of radiocarbon dating. Similarly, the rate of sediment transport from source to sink may determine the maturity and/or light exposure of mineral grains arriving in the delta and thus the feasibility of luminescence dating. Here, we explore the viability and quirks of dating and instrumental methods that have been applied in the Bengal Basin, and review the records that they have yielded. This immense, dynamic, and spatially variable system hosts the world's most inhabited delta. Outlining a framework for successful chronologic applications is thus of value to managing water and sediment resources for humans, here and in other populated deltas worldwide. Our review covers radiocarbon dating, luminescence dating, archaeological records and historical maps, short‐lived radioisotopes, horizon markers and rod surface elevation tables, geodetic observations, and surface instrumentation. Combined, these tools can be used to reconstruct the history of the Bengal Basin from Late Pleistocene to present day. The growing variety and scope of Bengal Basin geochronology and instrumentation opens doors for research integrating basin processes across spatial and temporal scales. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd.
Highlights
Like sands through the neck of an hourglass, the fluvial and tidal channels of deltaic margins govern the transfer of sediment from large source terrains to their expansive ocean sinks
Constraining the rates and timing of these processes through the application of geochronologic and instrumental tools is essential to determine the amount and distribution of available sediment, and of tectonic, compactional, and marine controls that may generate space to capture it on the delta plain (e.g.Paola et al, 2011; Allison et al, 2016)
We focus on methods that have been used to capture subsidence (e.g. Global Navigation Satellite System (GNSS), archaeological records, tide gauges, interferometric synthetic aperture radar (InSAR), and Rod surface elevation tables (RSETs); Steckler et al, 2010; Sarker et al, 2012; Pethick and Orford, 2013; Higgins et al, 2014; Wilson et al, 2018), and sediment accretion in the Bengal Basin
Summary
Like sands through the neck of an hourglass, the fluvial and tidal channels of deltaic margins govern the transfer of sediment from large source terrains to their expansive ocean sinks. Shortcomings, and quirks of each method in the context of Bengal Basin geomorphology, the datasets which they have yielded, and the implications that may emerge from combined geochronologic and instrumental records This novel perspective on chronology gives insights into the link between field setting and dating approach viability, thereby providing readers with the background needed to select appropriate methods for further advancing geochronologic and instrumental research into delta evolution. Radiocarbon dating of very young (less than ~300 years) material is generally not reliable due to the high anthropogenic input of carbon to the atmosphere (e.g. see Levin and Hesshaimer, 2000), there has been some recent progress on developing radiocarbon approaches for the past few centuries, including ‘post-bomb’ calibration (see Törnqvist et al, 2015) This means that radiocarbon dating can presently yield reliable ages within the range of 30,000–300 years, provided that suitable organic material is measured
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