Marine and Petroleum Geology 22 (2005) 637–656
ate/marpetgeo
The architecture and evolution of the Middle Bengal Fan in vicinity of the
active channel–levee system imaged by high-resolution seismic data
T. Schwenka,*, V. Spießa, M. Breitzkea,1,¨bscherb
aUniversita¨t Bremen, Fachbereich Geowissenschaften, Postfach 330440, 28344 Bremen, Germany
bInstitut fu¨r Geophysik, Universita¨t Hamburg, Bundesstrasse 55, 20146 Hamburg, Germany
Received 4 June 2004; received in revised form 20 January 2005; accepted 31 January 2005
Abstract
High-resolution seismic data from the Middle Bengal Fan were analysed to study the architecture of the fan in the vicinity of the active
channel–levee system and to evaluate channel behaviours. The upper 600 m column of the fan in the study area reveal a pattern of different
sized channel–levee systems and high amplitude reflection packets (HARPS) of varying thicknesses, no mass-flow deposits or hemipelagic
drapes are found. Within the channel–levee systems, units of chaotic high amplitude reflectors (CHARS), which represent aggraded and
migrated channel axes, as well as abandoned channel-fill deposits appear. All channels are characterised by erosional incision into underlying
deposits. Within the active channel–levee system, numerous cut-off loops are found showing a broad spectrum plex behaviours with
different ratios of vertical aggradation and lateral migration. As a difference to the Amazon Fan, the floors of all cut off loops and the active
channel are not elevated above the surrounding seafloor, which may lead to such a long lifetime resulting in the large number of cut-off loops.
In contrast, a detailed studied buried system shows no cut-off loops and is characterised by a more simple behaviour: a first phase of lateral
migration is followed by a second phase of simultaneous vertical aggradation and lateral migration, which finally elevated the channel floor
above the level of the surrounding seafloor. These archite
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