Depositional processes across the Sinú Accretionary Prism, offshore Colombia
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Accretionary wedge
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Integration of the latest Digital Terrain Model (DTM) with Synthetic Aperture Radar (SAR) Bathymetry
Topography and bathymetry integration is one of the essential things in providing height data. So far, the topography and bathymetry problems are the lack of height data availability, not up to date, and low vertical accuracy. The latest DTM is one of the topography data with up to date elevation with a spatial resolution of 5 m. Bathymetry extracted from SAR images. It is an alternative depth data for ocean bathymetry and inland water bathymetry. Topography and bathymetry integration is required to obtain comprehensive height data. This study aimed to integrate the latest DTM with SAR bathymetry. The method used in this integration was DEM integration. The method combined the latest DTM data with SAR bathymetry based on the correlation of the two data's standard deviation. The integration of the latest DTM with SAR bathymetry needs to consider differences in height reference fields. Two integration studies were conducted in this research-the latest DTM integration with ocean bathymetry for Rote Island. Then the integration of the latest DTM with inland water bathymetry in Lake Singkarak. The result of the integration is necessary to check the surface by generating longitudinal and cross-section profiles. Integrating the latest DTM and SAR bathymetry can be used for various mapping surveys on lands and waters.
Elevation (ballistics)
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Forearc basins are large sediment repositories that develop in the upper plate of convergent margins and are a direct response to subduction. These basins are part of the magmatic arc-forearc basin-accretionary prism "trinity" that defines the tectonic configuration of the upper plate along most subduction-related convergent margins. Many previous studies of forearc basins have explored the links between construction of magmatic arcs, exhumation of accretionary prisms, and sediment deposition in adjacent forearc basins. These studies provide an important framework for understanding firstorder tectonic processes recorded in forearc basins that are characterized by long-lived subduction of "normal" oceanic crust. Many convergent margins, however, are complicated by second-order subduction processes, such as flat-slab subduction of buoyant oceanic crust in the form of seamounts, spreading and aseismic ridges, and oceanic plateaus. These second-order processes can substantially modify the tectonic configuration of the upper plate both in time and space, and produce sedimentary basins that do not easily fit into the conventional magmatic arc-forearc basin-accretionary prism trinity. In this chapter, we discuss the modification of the southern Alaska forearc basin by Paleocene-Eocene subduction of a spreading ridge followed by Oligocene- Holocene subduction of thick oceanic crust. This thick oceanic crust is currently being subducted beneath south-central Alaska and has an imaged maximum thickness of 30km at the surface and 22 km at depth. Findings from southern Alaska suggest that forearc basins modified from flat-slab subduction processes may contain a sedimentary and volcanic stratigraphic record that differs substantially from typical forearc basins. Processes and sedimentary features that characterize modified forearc basins include the following: (1) flat-slab subduction of a buoyant, topographically elevated spreading ridge oriented subparallel to the margin prompts diachronous uplift of the forearc basin floor and exhumation of older marine forearc basin strata as the ridge is subducted. Passage of the spreading ridge leads to subsidence and renewed deposition of nonmarine sedimentary and volcanic strata that locally exceeds the thickness of the underlying marine strata. (2) Insertion of a slab window beneath the forearc basin during spreading ridge subduction produces local intrabasinal topographic highs with adjacent depocenters, as well as discrete volcanic centers within and adjacent to the forearc basin. (3) Flat-slab subduction of thick oceanic crust also results in surface uplift and exhumation of forearc basin sedimentary strata. However, the insertion of thick crust throughout the flat-slab region (i.e., lack of a slab window) inhibits subduction-related magmatism adjacent to the forearc basin. In the case of subduction of a >350-km-wide fragment of thick oceanic crust beneath south-central Alaska, exhumation of forearc basin strata located above the region of flat-slab subduction has prompted enhanced sediment delivery to active basins located along the perimeter of the flat-slab region. These perimeter basins record an increase in subsidence and sediment accumulation rates coeval with flat-slab subduction beneath the exhumed, inactive remnant forearc basin.
Forearc
Accretionary wedge
Volcanic arc
Convergent boundary
Back-arc basin
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This paper proposes a new model for the evolution of geologic structures in forearcs concerning subduction erosion after tectonic accretion. The model was generated from a high-pressure (HP) metamorphic unit, in which the early history of frontal offscraping accretion is recorded, in the Kamuikotan Zone of central Hokkaido. It was transported from the trench to the interior of the subduction zone during a non-accretionary stage, and the process is regarded to be subduction erosion and subsequent underplating re-accretion at greater depths. This mode of material transport persuasively explains the common and abundant occurrences of terrigenous meta-clastic rocks in HP subduction complexes, in spite of common evidence that sediments had been scraped off at much shallower depths as seen in coeval non-metamorphic accretionary units. It is thus suggested that significant amounts of HP metasediments originated from tectonically eroded materials of the frontal accretionary complex, instead of rocks directly underplated from the subducted slab. Subduction erosion in Hokkaido occurred contemporaneously with the exhumation of a higher-grade HP unit with similar rates of vertical movement of opposite senses. It suggests that exhumation was a counter flow of subduction erosion: the higher-grade rocks were lifted up by the insertion and accumulation of tectonically eroded rocks at depths, and were unroofed by lateral extension of the oversteepened non-accretionary wedge. This model can also explain common flat-lying structures of accretionary and subduction complexes exposed on land. They originally had rather high-angle structures formed by lateral shortening during early accretionary stages, and then were tilted trench-ward by the removal of materials near the trench by subduction erosion and their underplating at rear-side portions during the subsequent non-accretionary stages.
Accretionary wedge
Blueschist
Underplating
Eclogitization
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Radermacher, M., Wengrove, M.E., Van Thiel de Vries, J.S.M., Holman, R.A., 2014. Applicability of video-derived bathymetry estimates to nearshore current model predictions. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 290–295, ISSN 0749-0208.In the framework of swimmer safety, coastal managers desire accurate nearshore current predictions obtained from numerical models. To this end, detailed and up-to-date bathymetry is a necessity. Remote sensing techniques for bathymetry estimation are a promising solution. The focus of this paper is to assess the performance of wavenumber-based bathymetric inversion using Argus imagery (also known as the cBathy algorithm) as a feasible input bathymetry for numerical models to make reasonable nearshore current predictions. Numerical flow simulations on a cBathy bed are compared to simulations on an in-situ surveyed bathymetry. Results demonstrate that simulated nearshore currents on a cBathy bathymetry have a root-mean-square error in the order of 10 cm/s (magnitude) and 40 degrees (direction) when compared to simulated currents on a surveyed bathymetry. In the intertidal zone cBathy should be combined with a different method for bathymetry estimation in order to decrease these errors.
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A depositional environment, also known as a sedimentary environment, is a physiography setting where sediments are deposited. A depositional setting can be a river, a lake, a delta, a lagoon and the vast ocean. Each depositional setting imparts distinctive signatures to the sediments which also includes the imprints of the paleoclimate, flora and fauna which flourished at the time. With climate change and passage of time the physiographic setting of that depositional environment location changes and the new deposits carry the signatures of the new settings. Hence, analysis of the sedimentary column at a location helps us decipher the past depositional environments and reconstruct the paleoenvironment and geologic history of the sedimentary basin.
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