HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Nakajima, T. Articles by Thompson, P. J. P. GeoRef GeoRef Citation

Outer-Bank Bars: A New Intra-Channel Architectural Element within Sinuous Submarine Slope Channels

¹ National Institute of Advanced Industrial Science and Technology (AIST), Geological Survey of Japan, C-7, 1-1-1 Higashi, Tsukuba, Japan; takeshi.nakajima{at}aist.go.jp
² School of Earth and Environment, University of Leeds, Leeds LS2 9JT, U.K.
³ School of Earth and Environment, University of Leeds, Leeds LS2 9JT, U.K.
⁴ School of Earth and Environment, University of Leeds, Leeds LS2 9JT, U.K.
⁵ Department of Geology and Petroleum Geology, University of Aberdeen, Aberdeen AB24 3UE, U.K.; present address: BG Group, 100 Thames Valley Park Drive, Reading RG6 1PT, U.K.

This study describes for the first time "outer-bank bars," an intra-channel architectural element that is unique to sinuous submarine channels. The study is based on interpretation of 3D seismic data of sinuous channels in the upper slope of the Amazon Fan, offshore Brazil. Outer-bank bars comprise channel-fill deposits found in tight meander loops at outer corners of bend apices or slightly upstream or downstream of apices. This architectural element can be up to 1.5 km wide and up to 150 m thick with continuous internal reflectors dipping 1–20° towards the inner bend of the meander loop, a direction of dip opposed to that of fluvial point bars or submarine lateral-accretion packages. The angles of outer-bank bar surfaces increased to a maximum at bend apices. Outer-bank bars occur in the final aggradational channel fill in the two separated channel–levee systems in the Amazon data set. They may have been formed as a result of enhanced deposition on the outside of the bend caused by a combination of flow-volume reduction and flow superelevation. Accretion of outer-bank bars may cause the thalweg position to shift towards the inner bends leading to sinuosity reduction. Since this architectural element is likely to be sand prone, its recognition may have significant implications for prediction of hydrocarbon reservoirs.