[J08-1] Imaging and interpreting lithospheric structures using seismic and geodetic approaches I

[J08-1-03] Formation of the Lord Howe Rise continental ribbon during eastern Gondwana breakup from multi-channel seismic reflection data

^○Brian Boston¹, Yasuyuki Nakamura¹, Shuichi Kodaira¹, Seiichi Miura¹, Flora Gallais¹, Gou Fujie¹, Yuka Kaiho¹, Ron Hackney², Yasuhiro Yamada¹, Saneatsu Saito¹, Kazuya Shiraishi¹, Scott Nichol², George Bernardel², Cameron Mitchell² (1.Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan, 2.Geoscience Australia, Canberra, Australia)

The Lord Howe Rise continental ribbon, offshore eastern Australia, formed during the Late Cretaceous rifting of eastern Gondwana. This project focuses on multi-channel seismic reflection and bathymetry data collected on a multi-leg marine geophysical survey in 2016 to constrain the nature of rifting and the formation of the Lord Howe Rise. We present processed pre-stack depth-migrated seismic reflection images and interpretations of a regional, ~900 km long east–west-oriented profile at 27.2S, from the oceanic Tasman Basin to the extended continental crust of the Lord Howe Rise. We find that the Tasman Basin contains buried basins that may be related to early transform faulting. The Tasman Basin has a sharp eastern boundary against the Dampier Ridge, within which are multiple rift basins up to 3 km deep. These basins are similar to those found on the Lord Howe Rise. The Middleton Basin separates the Dampier Ridge and the Lord Howe Rise and is a broad, well-stratified sedimentary basin of up to ~3.5 km thickness. This basin contains an unconformity that separates deeper sediments, likely deposited during rifting of the Dampier Ridge, that are conformable with the basement and younger strata that filled the basin post-rifting. Both syn-rift and post-rift sedimentary sequences are found on the Lord Howe Rise. To better understand these rifting events, we present grids of pre-stack time-migrated seismic reflection lines covering two rift basins of the Lord Howe Rise. The two basins show contrasting evolution, including variations in normal faulting intensity within the syn-rift sequences. These results help constrain the dynamic processes that caused the formation of the Lord Howe Rise continental ribbon.