Integrating geochronologic and instrumental approaches across the Bengal Basin

Abstract

Constraining 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.

An Integrated Approach for Constraining Depositional Zones in a Tide-Influenced River: Insights from the Gorai River, Southwest Bangladesh

“…At Bardia Point, located~150 river km upstream of the mouth, the Gorai bifurcates into the Rupsha and Madhumati Rivers ( Figure 1B). Historically, the Madhumati accommodated the majority of discharge from the Gorai until the beginning of the 20th century [49], when the Rupsha off-take was extensively dredged to augment the delivery of river water to Khulna [50]. Since then, the Rupsha has taken precedence as the primary distributary, while the Madhumati has degraded as a result of waning fluvial input and channel siltation: Between 1965 and 1998, the average depth of the Madhumati River decreased 55% from 4.86 to 2.76 m [50].…”

Does Load‐Induced Shallow Subsidence Inhibit Delta Growth?

“…Moreover, this comparison indicates that a similar sediment yield is needed to maintain the delta‐plain area by offsetting RSLR in both deltas despite their vastly different tectonic settings. This has unfortunate implications for the sustainability of the Mississippi Delta, where sediment yield is about five times lower than in the Ganges‐Brahmaputra Delta (Chamberlain, Goodbred, Hale, et al., 2020).…”

Geomorphic change in the Ganges–Brahmaputra–Meghna delta

“…Reference source not found.). For instance, neotectonic activities such as uplift, tilting or subsidence occur gradually over a long period of time, whereas seismic events (like earthquakes) take place over a short period of time, but can generate morphological responses for years or decades after the event 17,36,159 . Human perturbations to the system tend to result in rapid adjustments, but the precise nature of the response depends on the boundaries of the system and the scale of disturbance 36 .…”