Thumbnail
Access Restriction
Open

Author Manley, P. L. ♦ Flood, R. D.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword GEOSCIENCES ♦ AMAZON RIVER ♦ ALLUVIAL DEPOSITS ♦ SEDIMENTATION ♦ ATLANTIC OCEAN ♦ DEPOSITION ♦ SEISMIC SURVEYS ♦ GEOLOGIC DEPOSITS ♦ GEOPHYSICAL SURVEYS ♦ RIVERS ♦ SEAS ♦ STREAMS ♦ SURFACE WATERS ♦ SURVEYS 580100* -- Geology & Hydrology-- (-1989)
Abstract The Upper and middle Amazon Fan has grown in a cyclic fashion. An individual deposition cycle consists of (1) a widespread basal, acoustically transparent seismic unit (interpreted as debris-flow deposits) that fills and levels preexisting topographic lows, and (2) a levee complex built of overlapping channel-levee systems. Two and possibly three cycles have been identified within the Amazon Fan. The levee complex beneath one debris flow originated from a different submarine canyon than did the levee complex above the debris flow, suggesting that these levee complexes formed during different sea level lowstands. Calculations based on present sediment discharge of the Amazon River suggest that an entire levee complex can form within the time span of a single glacial stage, such as the Wisconsin; however, the levee complex probably could not have formed during the relatively short time interval when sea level rose rapidly at the end of a glacial stage. The basal seismic units (debris-flow deposits) may have been deposited at any time during sea level fluctuations. Although seismic evidence suggests that this cyclic sedimentation pattern may be related to glacio-eustatic sea level variations, cyclic fan growth may be attributed to other processes as well. For example, a bottom-simulating reflector (BSR) observed within the upper fan appears to be a gas hydrate. Migration of the hydrate phase boundary during sea level fluctuations and diapiric activity may be mechanisms for initiating widespread debris flows. 10 figs.
Educational Use Research
Learning Resource Type Article
Publisher Date 1988-08-01
Publisher Place United States
Journal AAPG Bull.
Volume Number 72
Issue Number 8
Organization Columbia Univ., Palisades, NY (USA)


Open content in new tab

   Open content in new tab