Lord Howe Rise

Geology

The Lord Howe Rise is associated with seafloor spreading which also resulted in the creation of the Tasman Sea. The geology has not yet been characterised as well as other parts of Zealandia but when previous samples are analysed with current geological techniques they fit with the Zealandia hypothesis. The seafloor is known to be dominated by soft sediments and the highest quality recent survey only mapped approximately 25500 km2 of the western flank of the rise which is less than 1% of the total area of the rise. In this area about 0.1% of the rise's seafloor was classed as hard substrata based on a combined area of 31 km2 for 16 volcanic peaks. Sandstone rocks dredged from the central Lord Howe Rise contained granite pebbles that were in the range 216–183 million years old. It was rifted away from Eastern Australia in association with a mid-ocean ridge that was active from 80 to 60 million years ago, and now lies 800 kilometres offshore from mainland Australia.

The Lord Howe Rise contains a line of seamounts called the Lord Howe Seamount Chain which formed during the Miocene period when this part of Zealandia existed over the Lord Howe hotspot. One rhyolite sample has been dated at 97 million years drilled on the southern Lord Howe Rise. Lord Howe Island was the last volcano to erupt on the rise 6.5 million years ago.

Islands, reefs and seamounts

Lord Howe Island and Ball's Pyramid cap a seamount towards the central east of the rise in an area known as the Lord Howe platform. The Lord Howe Seamount Chain extends northwards along the rise. The seamounts provide habitat to a diverse range of marine species which attracts commercial fishers, but cover a very small area, less than 1% of the total area of Lord Howe Rise.

Further north is the Elizabeth and Middleton part of the Coral Sea Islands, which together with reefs around Lord Howe Island are the most southern coral reefs on Earth.

Environment

The seabed on the rise is mostly sandy mud with some volcanic outcrops, gravel and boulders.

The doubleheader fish, Coris bulbifrons, is endemic to reefs on the Lord Howe Rise and the West Norfolk Rise.

Resources

Much of the basin remains unexplored in relation to oil and gas reserves.

References

References

1. (16 June 2003). "Lord Howe Rise". [[Geoscience Australia]].
2. Harris, Peter T.. (2011). "Seafloor Geomorphology As Benthic Habitat: GeoHAB Atlas of Seafloor Geomorphic Features and Benthic Habitats". Elsevier.
3. Luyendyk, Bruce P.. (April 1995). "Hypothesis for Cretaceous rifting of east Gondwana caused by subducted slab capture". Geology.
4. (2011). "Biogeography of the Lord Howe Rise region, Tasman Sea". Deep Sea Research Part II: Topical Studies in Oceanography.
5. Mueller-Dombois, Dieter. (1998). "Vegetation of the Tropical Pacific Islands". Springer.
6. (2004). "Basement gabbro from the Lord Howe Rise". New Zealand Journal of Geology and Geophysics.
7. (2015). "Triassic–Jurassic granites on the Lord Howe Rise, northern Zealandia". Australian Journal of Earth Sciences.
8. Harris, P.T., 2011. Benthic environments of the Lord Howe Rise submarine plateau: Introduction to the special volume. Deep-Sea Research Part II 58, 883–888
9. Woodroffe, C.D., Dickson, M.E., Brooke, B.P., Kennedy, D.M., 2005. Episodes of reef growth at [[Lord Howe Island]], the southernmost reef in the southwest Pacific. Global and Planetary Change 49, 222–237
10. Gibson, Robin N.. (2011). "Oceanography and Marine Biology, Volume 49". CRC Press.
11. Misha Schubert and Barry Fitzgerald. (2009-04-22). "National bonanza sitting on shelf". [[Fairfax Digital]].