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Quantitative analysis of crevasse-splay systems from modern fluvial settings

M. Mostafizur Rahman, John A. Howell and David I. M. MacDonald
Quantitative analysis of crevasse-splay systems from modern fluvial settings
Journal of Sedimentary Research (September 2022) 92 (9): 751-774

Abstract

Although crevasse splays are a common constituent of many fluvial and fluvio-deltaic systems, they remain less well understood than the channel deposits in those settings, especially with respect to controls on their occurrence, distribution, and geometry. The current study aims to redress this balance and investigate controls on 1) splay formation and occurrence and 2) splay size and geometry. The study has used Google Earth-based satellite imagery to examine crevasse-splay deposits from eight modern fluvial systems. A total of 1556 crevasse splays were identified using imagery from 1984 to 2020. Most of the splays (c. 70%) occur on the outer sinuous river bank with offtake angles ranging from 10 degrees to 140 degrees (mean 75 degrees ) to the channel flow direction. Three different types of splays have been identified: i) single crevasse splays, ii) laterally amalgamated crevasse splays, and iii) crevasse-splay complexes. The areal extent of splay bodies varies widely and ranges from less than 1 km (super 2) up to 221 km (super 2) . The single crevasse splays are the primary and smallest form of splay, with an average area of 0.61 km (super 2) . Compensational stacking or progradation significantly increase the splay area and form laterally amalgamated splays and splay complexes, respectively. The average areal extent of laterally amalgamated splays is 1.33 km (super 2) , and of splay complexes, 39 km (super 2) . The climate, discharge, floodplain morphology, vegetation, trunk channel slope, sinuosity, and sediment load primarily control the occurrence, geometry, and dimensions of crevasse splays. Results demonstrate that sparse or no floodplain vegetation favors the formation of elongated tongue-shaped crevasse splays while densely vegetated floodplains produce more lobate splays. The highest splay frequency occurs in systems where the river experiences sudden high magnitude variation in discharge, has a low cross-sectional area, and noncohesive bank materials. Larger splay size is correlated with lower river slope angles and higher sinuosity, discharge, and floodplain relief. Channel size has little influence on the extent of splays. This work suggests that autogenic factors such as trunk-channel slope and sinuosity are more influential in arid-semiarid settings while allogenic factors such as discharge are important in temperate-equatorial settings.


ISSN: 1527-1404
EISSN: 1938-3681
Serial Title: Journal of Sedimentary Research
Serial Volume: 92
Serial Issue: 9
Title: Quantitative analysis of crevasse-splay systems from modern fluvial settings
Affiliation: University of Dhaka, Department of Geology, Dhaka, Bangladesh
Pages: 751-774
Published: 202209
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 110
Accession Number: 2022-052467
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables, sketch maps
Secondary Affiliation: University of Aberdeen, Department of Geology and Petroleum Geology, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 2022
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