IADO   05364
INSTITUTO ARGENTINO DE OCEANOGRAFIA
Unidad Ejecutora - UE
artículos
Título:
Morphodynamics and seismostratigraphy of a deep hole at tidal channel confluence.
Autor/es:
SILVIA SUSANA GINSBERG; SALVADOR ALIOTTA; GUILLERMO O. LIZASOAIN
Revista:
GEOMORPHOLOGY
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Año: 2009 p. 253 - 261
ISSN:
0169-555X
Resumen:
The sedimentary circulation pattern at a deep hole at a tidal channel junction in an estuary environment is
examined using morphosedimentological and seismostratigraphic data. The bottom and sub-bottom acoustic
information (side scan sonar and 3.5 kHz profiler) obtained at a tidal channel confluence in Bahía Blanca
estuary (Argentina) evidences the depositional and erosive features, bed load sediment transport pathways
and morphological evolution of the depression. This important depression in the confluence zone of the
channels is characterised by the presence of steep scour faces (14°) at the mouth of both channels and gentle
slopes (1.5°) opposite to them. Bed load sediment transport analysis reveals a differential circulation pattern
of sand on both sides of the hole, which is associated with the different sediment availability in each channel.
The side scan sonar information therefore indicates that there is no available sand in one of the channels
whereas the other channel is characterised by the presence of a large amount of sediment coming from its
inner area. Deposition therefore occurs on the side where sediment is mobilised as bed load by the ebb
current dominance and on the face developed downstream. In the latter, a part from the sediment is
deflected inward by the tidal flood currents which produce the deposition of sediment on the gentle side. The
rest of the sediment is exported from the system by ebb currents. In contrast, erosion occurs on the opposite
side of the hole and at the mouth of each channel and it is manifested by the outcrop of old sedimentary
strata. The seismostratigraphic information collected in this study indicates that the depression was
originally a fully erosive morphological feature. A descriptive model of the morphological evolution at a
channel confluence is presented in this study.filer) obtained at a tidal channel confluence in Bahía Blanca
estuary (Argentina) evidences the depositional and erosive features, bed load sediment transport pathways
and morphological evolution of the depression. This important depression in the confluence zone of the
channels is characterised by the presence of steep scour faces (14°) at the mouth of both channels and gentle
slopes (1.5°) opposite to them. Bed load sediment transport analysis reveals a differential circulation pattern
of sand on both sides of the hole, which is associated with the different sediment availability in each channel.
The side scan sonar information therefore indicates that there is no available sand in one of the channels
whereas the other channel is characterised by the presence of a large amount of sediment coming from its
inner area. Deposition therefore occurs on the side where sediment is mobilised as bed load by the ebb
current dominance and on the face developed downstream. In the latter, a part from the sediment is
deflected inward by the tidal flood currents which produce the deposition of sediment on the gentle side. The
rest of the sediment is exported from the system by ebb currents. In contrast, erosion occurs on the opposite
side of the hole and at the mouth of each channel and it is manifested by the outcrop of old sedimentary
strata. The seismostratigraphic information collected in this study indicates that the depression was
originally a fully erosive morphological feature. A descriptive model of the morphological evolution at a
channel confluence is presented in this study.fluence zone of the
channels is characterised by the presence of steep scour faces (14°) at the mouth of both channels and gentle
slopes (1.5°) opposite to them. Bed load sediment transport analysis reveals a differential circulation pattern
of sand on both sides of the hole, which is associated with the different sediment availability in each channel.
The side scan sonar information therefore indicates that there is no available sand in one of the channels
whereas the other channel is characterised by the presence of a large amount of sediment coming from its
inner area. Deposition therefore occurs on the side where sediment is mobilised as bed load by the ebb
current dominance and on the face developed downstream. In the latter, a part from the sediment is
deflected inward by the tidal flood currents which produce the deposition of sediment on the gentle side. The
rest of the sediment is exported from the system by ebb currents. In contrast, erosion occurs on the opposite
side of the hole and at the mouth of each channel and it is manifested by the outcrop of old sedimentary
strata. The seismostratigraphic information collected in this study indicates that the depression was
originally a fully erosive morphological feature. A descriptive model of the morphological evolution at a
channel confluence is presented in this study.flected inward by the tidal flood currents which produce the deposition of sediment on the gentle side. The
rest of the sediment is exported from the system by ebb currents. In contrast, erosion occurs on the opposite
side of the hole and at the mouth of each channel and it is manifested by the outcrop of old sedimentary
strata. The seismostratigraphic information collected in this study indicates that the depression was
originally a fully erosive morphological feature. A descriptive model of the morphological evolution at a
channel confluence is presented in this study.fluence is presented in this study.