AAPG Foundation 2019 Grants-in-Aid Projects

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Seismic geomorphology and U-Pb geochronology based sediment mass-balance analysis for Source-to-Sink systems in multi-rifted basins: A case study in the Dampier Sub-basin, Northwest shelf Australia


The shelf-edge in rift basins is a structurally complex region where high accommodation interacts with a variety of depositional processes. Sediment mass balance studies are often used in attempts to reduce the high reservoir quality risk in these areas. The Dampier sub-basin is a Jurassic marine rifted basin, filled with thick syn-rift sediments. 3D seismic, core and well logs are integrated in seismic geomorphologic analysis of the relationships between footwall drainages and submarine fans. U-Pb geochronology is incorporated to further assist in understanding sediment mass-balance between different rift depositional systems. Results show that five sub-drainages focus into the eastern side of the Kendrew trough through breached relay ramps. The ratio of catchment area to fan area shows the southern fan-aprons appear smaller than would be suggested by their source area volumes, while the northern fan-aprons appear to overly large relative to the fan volume trends. The lack of sediment mass-balance is considered to result from either lateral transportation of sediments by the longshore-currents, or due to sediment inputs from more northward located axial drainage systems. Seismic morphologic features show toe trimmed fan-shapes in the south and relatively well-preserved fan-shapes in the north, suggesting that current-generated processes may be reworking and sweeping sediments along the footwall from south to north. Detrital zircon dating is needed to parse sediment origins as coming from either north or south causing anomalies in the mass balance calculations. The conclusions of this study are critical for the exploration in these and other global rift basins.