Lithology, Monsoon and Sea-Surface Current Control on Provenance, Dispersal and Deposition of Sediments over the Andaman Continental Shelf

Damodararao, Karri; Singh, Sunil Kumar; Vinai, K.; Ramaswamy, V.; Rao, P. S.

doi:10.3389/fmars.2016.00118

Cited by 34 publications

(23 citation statements)

References 49 publications

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“…The identical 87 Sr/ 86 Sr values for the bulk and decarbonated beach ridge sample suggest that marine biogenic carbonates are a minor sediment component at the coast. However, previous measurements on Ayeyawady sediments (Table S2 with (Damodararao et al, 2016), which suggest mixing with a source similar to Sittaung.…”

Section: Resultsmentioning

confidence: 79%

“…Goodbred and Saito, 2012) and the perennial loss of sediment advected to the Gulf of Mottama (Ramaswamy and Rao, 2014). The Nd and Sr fingerprint of the river sediment is almost identical to the beach ridge at Bogale, indicating that essentially no sediment from the Gulf of Mottama bearing the radiogenic imprint of Sittaung (see above) and especially Thanlwin (Damodararao et al, 2016) is feeding this part of the coast. The shore-attached sandy clinoform tapers off after 40 m b.s.l.…”

Section: Discussionmentioning

confidence: 95%

“…Most of the large Ayeyawady sediment suspended load is redistributed by the strong tidal currents ( Fig. 5) and seasonally reversing wind currents to be deposited on the wide northern Andaman shelf (Ramaswamy and Rao, 2014) where it mixes with sediment from the Sittaung, Thanlwin and other smaller rivers (Damodararao et al, 2016). Semidiurnal tides vary between 2 and 3 m from the Pathein River to the Bogale River, reaching higher stages inside distributaries.…”

Section: Introductionmentioning

confidence: 99%

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On the Holocene evolution of the Ayeyawady megadelta

et al. 2018

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Abstract. The Ayeyawady delta is the last Asian megadelta whose evolution has remained essentially unexplored so far. Unlike most other deltas across the world, the Ayeyawady has not yet been affected by dam construction, providing a unique view on largely natural deltaic processes benefiting from abundant sediment loads affected by tectonics and monsoon hydroclimate. To alleviate the information gap and provide a baseline for future work, here we provide a first model for the Holocene development of this megadelta based on drill core sediments collected in 2016 and 2017, dated with radiocarbon and optically stimulated luminescence, together with a reevaluation of published maps, charts and scientific literature. Altogether, these data indicate that Ayeyawady is a mud-dominated delta with tidal and wave influences. The sediment-rich Ayeyawady River built meander belt alluvial ridges with avulsive characters. A more advanced coast in the western half of the delta (i.e., the Pathein lobe) was probably favored by the more western location of the early course of the river. Radiogenic isotopic fingerprinting of the sediment suggests that the Pathein lobe coast does not receive significant sediment from neighboring rivers. However, the eastern region of the delta (i.e., Yangon lobe) is offset inland and extends east into the mudflats of the Sittaung estuary. Wave-built beach ridge construction during the late Holocene, similar to several other deltas across the Indian monsoon domain, suggests a common climatic control on monsoonal delta morphodynamics through variability in discharge, changes in wave climate or both. Correlation of the delta morphological and stratigraphic architecture information on land with the shelf bathymetry, as well as its tectonic, sedimentary and hydrodynamic characteristics, provides insight on the peculiar growth style of the Ayeyawady delta. The offset between the western Pathein lobe and the eastern deltaic coast appears to be driven by tectonic-hydrodynamic feedbacks as the extensionally lowered shelf block of the Gulf of Mottama amplifies tidal currents relative to the western part of the shelf. This situation probably activates a perennial shear front between the two regions that acts as a leaky energy fence. Just as importantly, the strong currents in the Gulf of Mottama act as an offshore-directed tidal pump that helps build the deep mid-shelf Mottama clinoform with mixed sediments from the Ayeyawady, Sittaung and Thanlwin rivers. The highly energetic tidal, wind and wave regime of the northern Andaman Sea thus exports most sediment offshore despite the large load of the Ayeyawady River.

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Section: Resultsmentioning

confidence: 79%

Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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On the Holocene evolution of the Ayeyawady megadelta

et al. 2018

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“…The reason is the highly energetic tidal, wind and wave regime of the northern Andaman Sea that exports most sediments offshore despite the large load of the river, as described by Ramswamy et al (2004) and Hedley et al (2010). In addition to their effects upstream (Brakenridge et al, 2017), the expected sediment deficit after dams are constructed on the river and tributaries may significantly impact the fragile delta sedimentary equilibrium (Giosan et al, 2014) rendering it more vulnerable to the accelerating sea level rise (Syvitski et al, 2009) or changes in frequency and intensity of cyclones hitting the coast (Darby et al, 2016) compounded with increased subsidence linked to the rapid development of the region (e.g., Van der Horst, 2017).…”

Section: Discussionmentioning

confidence: 98%

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Giosan¹

2018

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“…The Nd and Sr 542 fingerprint of the river sediment is almost identical to the beach ridge at Bogale 543 indicating that essentially no sediment from the Gulf of Mottama bearing the lower 544 radiogenic imprint of Sittaung or Thanlwin (Damodararao et al, 2016) is feeding this 545…”

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confidence: 99%