Three‐dimensional seismic analysis of sediment waves and related geomorphological features on a carbonate shelf exposed to large amplitude internal waves, Browse Basin region, Australia

Abstract

This study analyses the three-dimensional geometry of sedimentary features recorded on the modern sea floor and in the shallow subsurface of a shelf to upper slope region offshore Australia that is characterized by a pronounced internal wave regime. The data interpreted comprise an extensive, >12 500 km 2 industrial three-dimensional seismic-reflection survey that images the northern part of the Browse Basin, Australian North West Shelf. The most prominent seismic-morphological features on the modern sea floor are submarine terrace escarpments, fault-scarps and incised channels, as well as restricted areas of seismic distortion interpreted as mass wasting deposits. Besides these kilometre-scale sea floor irregularities, smaller bedforms were discovered also, including a multitude of sediment waves with a lateral extent of several kilometres and heights up to 10 m. These sedimentological features generally occur in extensive fields in water depths below 250 m mostly at the foot of submerged terraces, along the scarps of modern faults and along the shelf break between the outer shelf and the upper continental rise. Additional bedforms that characterize the more planar regions of the outer shelf are elongate, north-west/southeast oriented furrows and ridges. The formation of both sediment waves and furrow-ridge systems requires flow velocities between 0Á3 m sec À1 and 1Á5 m sec À1 , which could be generated by oceanic currents, gravity currents or internal waves. In the studied setting, these velocities can be best explained as being generated by bottom currents induced by internal waves, an interpretation that is discussed against oceanographic background data and modelling results. In addition to the documentation of three-dimensional seismic-geomorphological features of the modern sea floor, it was also possible to map kilometre-scale buried sediment wave fields in the seismic volume down to ca 500 ms two-way-time below the present sea floor, indicating the general potential for the preservation of such bedforms in the sedimentary record.

Research on the fluid dynamics interaction between submarine sand waves and seawater by seismic oceanography

“…The calculation and analysis of the formation mechanism and mathematical model of submarine sand waves show that the incipient velocity of medium sand forming submarine sand waves is 0.507m/s. Therefore, the bottom current velocity in this area is sufficient to shape the seabed topography by forming submarine sand waves (Reeder et al, 2011;Belde et al, 2015;Ribóet al, 2016). Consequently, based on previous studies of the hydrodynamic environment around the Dongsha Uplift of the northern South China Sea and the development of submarine sand waves, it is reasonable to estimate the seawater flow velocity of 0.80m/s by fluid dynamics numerical simulation and seismic oceanography method.…”

Physical sedimentary controls on subtropical coastal and shelf sedimentary systems: Initial application in conceptual models and computer visualizations to support archaeology

“…The coastal and shelf sedimentary composition, distribution, suite of bedforms and sedimentary environments all indicate that, for the modern shelf, there is the regional importance of the pre‐existing shelf topography, because most post‐glacial Holocene deposits are thin and there are many bathymetric features and islands derived from drowned shorelines (e.g., Baker, Potter, Tran, & Heap, ; Wilson, ) (score 4); the widespread occurrence of mesotidal to macrotidal estuaries (e.g., Lees, ) (score 4); and cyclone‐associated features on the seabed (cf. Belde et al., ; Belde, Reuning, & Back, ; Larcombe et al., ; Ward et al., ) (score 4). …”

“…• cyclone-associated features on the seabed (cf. Belde et al, 2015;Belde, Reuning, & Back, 2017;Larcombe et al, 2014;Ward et al, 2016) (score 4).…”

“…similar array of physical evidence occurs at a wide variety of depths on Australia's cyclone-influenced NW Shelf(Belde, Back, & Reuning, 2015;Jones, 1973;Jones, Kennard, Logan, Grosjean, & Marshall, 2009;Larcombe, Huang, & Pusey, 2014) although relatively little material has been dated. On the inner and middle shelf are located extensive fields of asymmetric very large submarine sand and gravel dunes (sensuAshley, 1990), almost universally aligned with the steep sides facing SSW along the shelf, and an array of other large sedimentary bedforms.…”

The role of Internal Solitary Waves on deep-water sedimentary processes: the case of up-slope migrating sediment waves off the Messina Strait

“…Sand waves generally form in those tidal environments where the interaction between seafloor morphology and tidal currents is strong enough to allow for the necessary shear stress that triggers sediment motion1112131415. Sand-wave formation can be also due to downslope-flowing turbidity currents, along-slope bottom currents, and internal (progressive or solitary) waves9101617.…”