A study on the dynamic process of fluid mud and its effect on siltation in the Yangtze Estuary Deepwater Channel

<p>The Yangtze Estuary Deepwater Channel Project has brought great economic and social benefits since its completion, but the siltation problem is still worthy of attention. In order to investigate the mechanisms of fluid mud in the estuary and to study the influence of fluid mud on siltation in the Yangtze Estuary Deepwater Channel, a two-dimensional physically-enhanced two-layer flow model will be developed in this paper. The model includes two series of governing equations which are about environment fluid and fluid mud, respectively. The model is based on the unstructured grid, and the governing equations are discretized by the finite volume method, and the improved LTS/GMaTS technology is used to improve the computational efficiency. Firstly, an experiment that the fluid mud was flowing underwater along a gentle slope is reconstructed by the two-layer model. It shows the ability of the model to describe the simple movement of fluid mud. Secondly, the model is applied to Yangtze Estuary. Without the fluid mud layer, the model can be simplified as a tide-current model. The reliability of the tidal current and tide level is verified, and it means the model can describe the tide accurately. Based on this, the process of formation, transport, and break-down of fluid mud is simulated and its effect on the siltation in the Yangtze Estuary Deepwater Channel is estimated.</p>

Seismic geomorphology anomalies within a Pliocene deepwater channel complex in the Taranaki Basin, offshore New Zealand

The Taranaki Basin, located offshore New Zealand, is a Cretaceous rift basin which has well defined yet complex Miocene deepwater sedimentary systems. This paper analyzes a pronounced anomalous seismic response in a late Miocene to early Pliocene deepwater channel within the 2005 Hector 3D survey located in the southern Taranaki Basin. Several seismic attributes were calculated to interpret the extent of these anomalous features. Modern analogues from Snedden (2013) within both the Iron River reservoir in Albania, Canada and the East Breaks Basin Four, offshore Gulf of Mexico suggest that these anomalous seismic features are most likely channel-body basal scours resulting from turbulent flows that eroded the base of the channel. One alternative interpretation is that this is not a channel but rather a scar left behind from a small-scale mass trasnport deposit (MTD) where sediment later ponded and filled in the rugose topography left by the MTD. This process has also been observed by Kremer et al. (2018) within the Molasse Basin in southern Germany. However, these scours could also be interpreted as pockmarks resulting from channel abandonment and fluid escape due to compaction. Jobe et al. (2011) described this process within submarine canyon systems, offshore Equatorial Guinea. Within all possible interpretations, there is evidence of differential compaction as sediment fills the accommodation space and creates a concave down expression immediately above the interpreted scours.