Reconstructing fluvial bar surfaces from compound cross-strata and the interpretation of bar accretion direction in large river deposits

Reconstructing fluvial bar surfaces from compound cross-strata and the interpretation of bar accretion direction in large river deposits

Author Almeida, Renato P. Google Scholar
Freitas, Bernardo T. Google Scholar
Turra, Bruno B. Google Scholar
Figueiredo, Felipe T. Google Scholar
Marconato, Andre Google Scholar
Janikian, Liliane Autor UNIFESP Google Scholar
Abstract The interpretation of fluvial styles from the rock record is based for a significant part on the identification of different types of fluvial bars, characterized by the geometric relationship between structures indicative of palaeocurrent and surfaces interpreted as indicative of bar form and bar accretion direction. These surfaces of bar accretion are the boundaries of flood-related bar increment elements, which are typically less abundant in outcrops than what would be desirable, particularly in large river deposits in which each flood mobilizes large volumes of sediment, causing flood-increment boundary surfaces to be widely spaced. Cross-strata set boundaries, on the other hand, are abundant and indirectly reflect the process of unit bar accretion, inclined due to the combined effect of the unit bar surface inclination and the individual bedform climbing angle, in turn controlled by changes in flow structure caused by local bar-scale morphology. This work presents a new method to deduce the geometry of unit bar surfaces from measured pairs of cross-strata and cross-strata set boundaries. The method can be used in the absence of abundant flood-increment bounding surfaces; the study of real cases shows that, for both downstream and laterally accreting bars, the reconstructed planes are very similar to measured bar increment surfaces.
Keywords Architectural elements
bar geometry reconstruction
cross-strata set boundaries
fluvial depositional systems
xmlui.dri2xhtml.METS-1.0.item-coverage Hoboken
Language English
Sponsor Sao Paulo Research Foundation (FAPESP)
Liliane Janikian
Grant number FAPESP: 2009/53363-8
FAPESP: 2009/52807-0
FAPESP: 2009/51766-8
FAPESP: 2010/51103-6
FAPESP: 2010/51559-0
FAPESP: 2013/01825-3
FAPESP: 2014/16739-8
CAPES: PROEX-558/2011
CNPq: 301774/2012-9
Liliane Janikian: 301775/2012-5
Date 2016
Published in Sedimentology. Hoboken, v. 63, n. 3, p. 609-628, 2016.
ISSN 0037-0746 (Sherpa/Romeo, impact factor)
Publisher Wiley-Blackwell
Extent 609-628
Access rights Open access Open Access
Type Article
Web of Science ID WOS:000372342200004

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