The geological record preserved by Amazon shelf sedimentation

Nittrouer, Charles A.; Kuehl, Steven A.; Figueiredo, Alberto G.; Allison, Mead A.; Sommerfield, Christopher K.; Rine, James M.; Faria, L. Ercilio C.; Silveira, Odete Fátima Machado da

doi:10.1016/0278-4343(95)00053-4

Cited by 108 publications

(64 citation statements)

References 39 publications

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“…Amazon, Po, Ebro, Eel, Columbia, etc (Wright and Nittrouer, 1995;Driscoll and Karner, 1999;Nittrouer et al, 1996;Cattaneo et al, 2004). The combined effect of oceanographic processes (tidal, wave and current) redistributed most of large riverderived sediments along the shelf, extending hundreds of kilometers from the river mouths and the proximal subaqueous deltas.…”

Section: Discussionmentioning

confidence: 99%

Fate of sediments delivered to the sea by Asian large rivers: Long-distance transport and formation of remote alongshore clinothems

Liu¹,

Xue²,

Ross³

et al. 2009

TSR

159

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Recent studies show that the global flux of river-derived sediment reaching the coasts and oceans is about 15-19 x 10 9 tons per year. New sediment budgets for the major Asian river systems (e.g.,Yellow, Yangtze, Mekong, Ganges-Brahmaputra, etc.) suggest that 30-50% of their sediment load has been retained in the lower channel reaches to form an extensive subaerial delta plain, while the rest is discharged to the sea. Of the sediment load reaching the ocean, about half has been found to accumulate near the river mouth as a proximal subaqueous delta clinothem. However, the remaining sediment is found to be transported up to 600-800 km alongshore, ultimately being deposited as a shore-parallel middle-shelf clinothem.These clinoform deposits are generally <100 km in across-shelf width, 20-40 m thick nearshore, and pinch-out gradually seaward at 40-90 m water depth.A secondary nearshore depocenter can usually be found along the shelf away from the river mouth, with mud-lobe accumulation up to 40-50 m thick locally. Except for a few systems with shelf-indenting canyons (e.g., Ganges-Brahmaputra and Indus), most of Asian riverderived sediments are trapped on the inner and middle shelf, unable to reach the deep ocean (i.e., >150 m) despite having been transported hundreds of kilometers from their mouths.

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Section: Discussionmentioning

confidence: 99%

Fate of sediments delivered to the sea by Asian large rivers: Long-distance transport and formation of remote alongshore clinothems

Liu¹,

Xue²,

Ross³

et al. 2009

TSR

159

View full text Add to dashboard Cite

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“…A conventional molecular clock of 2% per million years for the cytochrome b gene (Avise, 2000) suggests that this divergence is between 0.6 and 1.65 millions of years (myr) old, much younger than the estimated age of the initial connection of the Amazon with the Atlantic, 10-12 myr old (Hoorn, 1994;Nittrouer et al, 1996;Costa et al, 2001). Thus, vicariance alone cannot explain the observed pattern, and dispersal from one area to the other after the formation of the Amazon is probably involved in speciation of western Atlantic Halichoeres.…”

Section: Discussionmentioning

confidence: 99%

Mitochondrial DNA and Color Pattern Variation in Three Western Atlantic Halichoeres (Labridae), with the Revalidation of Two Species

Rocha¹

2004

Copeia

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Genetic surveys of widely distributed marine species often find previously undetected biodiversity. In the present study, populations of three species of Halichoeres were sampled across their entire geographical ranges: Halichoeres cyanocephalus and Halichoeres maculipinna were sampled on both sides of the Amazon freshwater outflow, the main biogeographic barrier in the tropical western Atlantic; and Halichoeres garnoti was sampled in the Caribbean and Bermuda. Genetic divergences between populations separated by the Amazon ranged from 2.3% in H cyanocephalus to 6.5% in H. maculipinna. There is inconsistency between color differences and genetic partitions in the species surveyed. The color differences between populations of H cyanocephalus and H maculipinna correspond to deep genetic partitions at the cytochrome b locus. However, genetic similarity at this same locus was observed between populations of H. garnoti with striking color differences. Based on the combination of the observed genetic differences with diagnostic color differences, the BraziUan species Halichoeres dimidiatus (Agassiz) and Halichoeres penrosei Starks, 1913 are revalidated. In addition, a neotype is designated to H cyanocephalus (Bloch, 1791), to clarify its taxonomic status and type locaUty. All species analyzed have a similar larval dispersal potential, but varying degrees of genetic divergences were observed, indicating that benthic stage ecology may also play a role in speciation in this group.

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“…Studies on large modern subaqueous deltas like the Amazon (Kuehl et al, 1986;Nittrouer et al, 1986;Nittrouer et al, 1996;Kineke et al, 1996) and the Ganges-Brahmaputra (Kuehl et al 1997;2005;Michels et al, 1998) show that hyperpycnal sediment plumes play a crucial role in transporting and delivering sediment from the river mouth to the clinoform, and that alongshore currents redistribute sediments allowing clinoform development along-shelf as well as across-shelf (Driscoll and Karner, 1999;Giosan et al, 2006). Modeling studies for gravity-driven, wave-supported sediment transport predict the equilibrium profile of a mid-shelf clinoform as a function of wave climate and fluvial sediment supply (Friedrichs and Wright, 2004;Wright and Friedrichs, 2006).…”

Section: Iamentioning

confidence: 99%

Aridification of the Indian subcontinent during the Holocene : implications for landscape evolution, sedimentation, carbon cycle, and human civilizations

Ponton¹

2012

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The Indian monsoon affects the livelihood of over one billion people. Despite the importance of climate to society, knowledge of long-term monsoon variability is limited. This thesis provides Holocene records of monsoon variability, using sediment cores from river-dominated margins of the Bay of Bengal (off the Godavari River) and the Arabian Sea (off the Indus River). Carbon isotopes of terrestrial plant leaf waxes (6 13 Cwax) preserved in sediment provide integrated and regionally extensive records of flora for both sites. For the Godavari River basin the 61 3 Cwax record shows a gradual increase in aridity-adapted vegetation from ~4,000 until 1,700 years ago followed by the persistence of aridity-adapted plants to the present. The oxygen isotopic composition of planktonic foraminifera from this site indicates drought-prone conditions began as early as -3,000 years BP. The aridity record also allowed examination of relationships between hydroclimate and terrestrial carbon discharge to the ocean. Comparison of radiocarbon measurements of sedimentary plant waxes with planktonic foraminifera reveal increasing age offsets starting -4,000 yrs BP, suggesting that increased aridity slows carbon cycling and/or transport rates. At the second site, a seismic survey of the Indus River subaqueous delta describes the morphology and Holocene sedimentation of the Pakistani shelf and identified suitable coring locations for paleoclimate reconstructions. The 6 3 Cwax record shows a stable arid climate over the dry regions of the Indus plain and a terrestrial biome dominated by C 4 vegetation for the last 6,000 years. As the climate became more arid 4,000 years, sedentary agriculture took hold in central and south India while the urban Harappan civilization collapsed in the already arid Indus basin. This thesis integrates marine and continental records to create regionally extensive paleoenvironmental reconstructions that have implications for landscape evolution, sedimentation, the terrestrial organic carbon cycle, and prehistoric human civilizations in the Indian subcontinent. 3 4A mi Tito y mi Sense, por haberme despertado el interes por la Ciencia. 5Creo muy poco en lo que veo. Y de lo que me cuentan... nada.-Juan Siyago 6 Acknowledgements I am indebted to my Advisors for their unconditional support and generosity with their ideas and their time. Thank you for keeping me afloat when the seas were rough and I had started to drown. I learned that persistence is key and Science is humbling. Through this journey Liviu's tenacity and strong guidance, and Tim's enthusiasm and optimistic outlook delivered me safely to shore.I will like to thank my committee members and Chair for their invaluable contributions to improve this thesis, but most importantly for their continuous support, concern and encouragement through out these years. Delia, for always being my advocate and offering your experience to suggest alternative solutions. Valier, I have learned immensely from you in the lab and our discussions have always been frui...

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The geological record preserved by Amazon shelf sedimentation

Cited by 108 publications

References 39 publications

Fate of sediments delivered to the sea by Asian large rivers: Long-distance transport and formation of remote alongshore clinothems

Fate of sediments delivered to the sea by Asian large rivers: Long-distance transport and formation of remote alongshore clinothems

Mitochondrial DNA and Color Pattern Variation in Three Western Atlantic Halichoeres (Labridae), with the Revalidation of Two Species

Aridification of the Indian subcontinent during the Holocene : implications for landscape evolution, sedimentation, carbon cycle, and human civilizations

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