Balls Pyramid is the southernmost island in a linear island chain in the southwest Pacific Ocean, 24 km south of the limit of known coral reef formation at Lord Howe Island. This paper describes the geomorphometric structure of the shelf surrounding Balls Pyramid through the application of remote sensing data to create a high-resolution digital elevation model of the shelf (5 m cell size) and seafloor feature classification. Seafloor features were delineated using the bathymetry model together with slope, backscatter and sub-bottom profile data. The average depth of the 260.6 km2 shelf was 55 m (± 21 m), with the majority of shelf area (77%) within 30–60 m water depth. Dominating the shelf is an extensive, mid-shelf reef at 30–50 m depth, dissected by basin and channel features. Outer-shelf reef and platform features surround the mid shelf, with terrace sequences marking the seaward outer-shelf rim in 65–100 m depth. Sub-bottom profiles and backscatter data demonstrate substantial accumulation (up to 16.5 m) of unconsolidated sediments within basin and channel features. The submerged mid-shelf reefs of Balls Pyramid are similar to the fossil coral reef system discovered on the Lord Howe Island shelf, implying origins as a drowned coral reef system. This paper reveals complex shelf topography with extensive submerged reefs on what was previously considered to be a planated volcanic shelf outside of reef-forming seas.

Depth range
30- 100 m

Mesophotic “mentions”
0 x (total of 6447 words)

Classification
* Presents original data
* Focused on 'mesophotic' depth range
* Focused on 'mesophotic coral ecosystem'

Fields
Geomorphology

Locations
Australia - Southeastern Australia

Platforms
Sonar / Multibeam