Book contents
- Fluvial Megafans on Earth and Mars
- Fluvial Megafans on Earth and Mars
- Copyright page
- Contents
- Contributors
- Foreword
- Part I Introduction
- Part II Regional Studies
- 3 Megafans of Africa
- 4 Megafans of the Northern Kalahari Basin (Angola, Botswana, Namibia, Zambia)
- 5 The Chaco Megafans, South America
- 6 Megafans of the Pantanal Basin, Brazil
- 7 Geomorphic and Chronological Assessment of Aggradation Patterns on the Río Grande (Guapay) Megafan, Eastern Bolivia
- 8 Megafans of Southern and Central Europe
- 9 The Loire Megafan, Central France
- 10 Megafans of the Gangetic Plains, India
- 11 The Kosi Megafan, India
- 12 The Holocene Mitchell Megafan, Gulf of Carpentaria, Australia
- 13 Megafans of the Northern Victorian Riverine Plains, SE Australia
- Part III Applications in Other Sciences
- Part IV Megafans in World Landscapes
- Index
- References
5 - The Chaco Megafans, South America
from Part II - Regional Studies
Published online by Cambridge University Press: 30 April 2023
- Fluvial Megafans on Earth and Mars
- Fluvial Megafans on Earth and Mars
- Copyright page
- Contents
- Contributors
- Foreword
- Part I Introduction
- Part II Regional Studies
- 3 Megafans of Africa
- 4 Megafans of the Northern Kalahari Basin (Angola, Botswana, Namibia, Zambia)
- 5 The Chaco Megafans, South America
- 6 Megafans of the Pantanal Basin, Brazil
- 7 Geomorphic and Chronological Assessment of Aggradation Patterns on the Río Grande (Guapay) Megafan, Eastern Bolivia
- 8 Megafans of Southern and Central Europe
- 9 The Loire Megafan, Central France
- 10 Megafans of the Gangetic Plains, India
- 11 The Kosi Megafan, India
- 12 The Holocene Mitchell Megafan, Gulf of Carpentaria, Australia
- 13 Megafans of the Northern Victorian Riverine Plains, SE Australia
- Part III Applications in Other Sciences
- Part IV Megafans in World Landscapes
- Index
- References
Summary
The Chaco plain, covering > 800,000 km2 in Bolivia, Argentina, and Paraguay, comprises six megafans. These are fed mainly from Subandean basins that are among the highest sediment-yielding basins of the Andes: of the total supplied (~ 325 Mt·yr–1) ~ 68 % is trapped on the megafans – because all the rivers except one end on the megafans, reaching at most ~ 50 % of the distance of their late Pleistocene ancestors. As such, the Chaco plain is one of the largest active continental sedimentary sinks of the planet, and includes the longest known megafan. The rivers terminate in the largest area of seasonal wetlands in South America, a product of (i) extremely flat megafan surfaces, (ii) the mosaic of palaeolandforms and present fluvial and lacustrine patterns, and (iii) the hydrogeomorphological dynamics under the current Holocene humid climate. Calculations of specific power appear to explain the effectiveness of these rivers in transporting the current inputs of water and sediment. However, during part of the Late Pleistocene the hydrological and sedimentological regimes allowed the fan-forming rivers to deliver sediment to the regional Paraguay and Paraná trunk rivers and thence to the ocean. New morphometric data describe relationships between feeder-basin area and megafans area, slope and circularity.
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- Fluvial Megafans on Earth and Mars , pp. 78 - 99Publisher: Cambridge University PressPrint publication year: 2023
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