| 21 May 2026
Assessing sedimentological proxies for characterizing tropical storm deposits in the Chandipur coastal region of Bay of Bengal, India: A modern analog for paleotempestology
Abstract. Coastal morphodynamics in barrier systems are governed by changes in sediment supply, sea level, and storm events. However, the limited availability of well-characterized modern analogs hinders the interpretation of sediments deposited by tropical storms, particularly in the Bay of Bengal. This study aims to evaluate the sedimentological proxies for identifying overwash deposits in the back-barrier region of Chandipur, India, using integrated granulometric and morphoscopic analyses across five sediment transects. Grain size distributions were modeled into four end-members (EMs) representing aqueous suspension-dominated transport, aqueous suspension with minor saltation, aeolian saltation, and high-energy depositional environment. To address compositional constraints, centered log-ratio (Clr)-transformed EM scores, were analyzed spatially to assess variations in depositional processes. Quartz grain morphoscopy, following the Cailleux classification, was used to assign grains to seven established shape categories, with fractured C-type grains being interpreted as indicative of high-energy mechanical modification. By combining grain size and morphoscopic characteristics, cluster analysis distinguished three sediment groups linked to aqueous, aeolian, and overwash-dominated environments. Microtextural observations further refine transport interpretations, indicating that many grains underwent high-energy collisions typical of marine reworking during storm events. A multi-proxy approach incorporating EM modelling, compositional analysis, grain morphology, and microtextural evidence establishes a reliable framework for differentiating overwash deposits. The results emphasize the value of integrating multiple sedimentological proxies to identify tropical storm signatures, with clear applications in paleotempestology and coastal management initiatives.
Review of “Assessing sedimentological proxies for characterizing tropical storm deposits in the Chandipur coastal region of Bay of Bengal, India: A modern analog for paleotempestology”
Saha et al presents an investigation on the sedimentological characteristics of tropical storm deposits in the Chandipur coasta region by using grain-size distribution, end-member modeling analysis, SEM grain-morphoscopic and microtextural analysis inspired in Mycielska and Woronko (1998), and multivariate statistics. The topic is very relevant to the fields of paleotempestology and coastal hazard assessment because of the studies on forecasting tropical storms and sea level rise deposits remain limited. The authors present a dataset over 5 transects along the Barrier bar located in the Bay of Bengal; for this specific case samples were extracted at ~10 cm from the surface. The manuscript also employs a multi-proxy approach that might have a potential value. However; several aspects of the study require clarification and strengthening before the discussion and conclusions can be fully supported. One of my main concerns goes to the evidence linking the different sediment populations that were identified to the different types of deposits. In the case of the overwash deposition (cluster 3), it is largely inferential and it is difficult to conclude something from Figure 11. Finally, the current manuscript lacks direct validation that the samples obtained were generated by specific documented storm events.
Major-comments:
One of the main conclusions of the manuscript is that EM4 and the associated morphoscopic cluster (NU and C grains) respresent storm-overwash deposits (Fig. 10). Nevertheless, this interpretation seems to be based on grain-size characteristics and the presence of fractured grains, which can be a good assumption, but other high-energy coastal processes are not excluded. In addition, the presence of this distribution over most of the transects is not well discussed.
The manuscript states that surface sediments were collected in 2018 from the upper ~10 cm of sediment. A 10 cm thick surface sample may integrate multiple depositional events occurring over months or years. Consequently, it is difficult to directly associate the observed sediment characteristics with specific storms such as Daye or Titli. The authors should discuss the temporal resolution of the sampling strategy and the extent to which the sampled material can realistically be attributed to individual storm events.
The manuscript repeatedly interprets fractured grains as indicators of storm activity due to high-energy collisions and other factors. While previous studies have reported similar observations, fractured quartz grains can originate from multiple processes including sediment recycling, beach swash processes, mechanical weathering, and fluvial transport. The authors should better justify why fractured grains in this setting specifically indicate storm overwash rather than generic high-energy transport.
The assignment of EM1–EM4 to distinct transport modes (suspension, suspension with saltation, aeolian transport, and overwash transport) appears largely conceptual. No independent hydrodynamic measurements or transport modelling are shown to validate these interpretations. The authors should explain more clearly how each end-member was linked to a specific transport process and discuss uncertainties associated with these assignments.
The PCA and cluster analysis identify three groups interpreted as aqueous, aeolian, and overwash deposits (Fig. 10). However, the observed clustering may simply reflect spatial gradients across the barrier-marsh system. The authors should demonstrate that the clusters represent distinct depositional processes rather than a continuum of environmental conditions.
SEM analysis is presented as an important component of the study, yet the interpretation remains largely qualitative. The manuscript would benefit from more detailed presentation of representative SEM images and clearer explanation of how specific microtextures distinguish storm transport from normal marine reworking. From Figs. 6, 12 and 13, it is hard to see the difference between shine and mate particles.
Several studies have described sedimentological characteristics of known storm deposits from other regions. A more detailed comparison between the Chandipur deposits and established modern overwash analogs would strengthen the interpretation.
Minor comments:
From line 87-91: this paragraph has to be more specific. Here the authors can relate the grain characteristics (size, shape, etc) to the storm derived sediments.
Line 118-119: explain why the samples were only at 10cm from the surface
Line 127-129: explain better why the authors used a solution of (NaPO3)6
Line 155: Why the samples were sieved only for the grain morphoscopic and microstructural study? This comes back to the grain size distribution. It should be well explained. The reader can get confused.
Line 172-178: There is too much explanation on the SEM details, instead, the authors should focus more on the characterization of rounded/angular shine/mate surfaces. This process seems that was very random.
From section 3.3 on: authors called EM as the end-member method, but sometimes, I got confused with the other nomenclature (shape/brightness), what about the authors renamed as EMMA as stated in section 3.1
Section 3.4: This section should be enhanced, this is the one that leads the discussion and conclusions. See major comments.
Line 229: Authors say that only CL3 to CL5 have moderate to poor sorting, but I see that all the transects have this distribution (Fig.2)
Figure 4 and 5 should have a label of the colormaps, what the colors represent?
Figure 10: In my opinion, this is the most important figure in the manuscript; however the last column should be enhanced, it is difficult to distinguish the aqueous, aeolian, and overwash transport.
Figure 12 and 13: The images should be zoomed in to see the real differences of the patterns described. For me, it is difficult to differentiate CF, AP, and VS.