R. Sutherland , G.R. Dickens , P. Blum , C. Agnini , L. Alegret , J. Bhattacharya , A. Bordenave , L. Chang , J. Collot , M.J. Cramwinckel , E. Dallanave , M.K. Drake , S.J.G. Etienne , M. Giorgioni , M. Gurnis , D.T. Harper , H.-H.M. Huang , A.L. Keller , A.R. Lam , H. Li , H. Matsui , H.E.G. Morgans , C. Newsam , Y.-H. Park , K.M. Pascher , S.F. Pekar , D.E. Penman , S. Saito , W.R. Stratford , T. Westerhold , X. Zhou
2 February 2019
International Ocean Discovery Program (IODP) Site U1510 (36°19.74ʹS, 164°33.52ʹE; 1238 m water depth) is on southern Lord Howe Rise, ~850 km west of northern New Zealand. Two Deep Sea Drilling Project (DSDP) sites are nearby: Site 592 is ~80 km east, and Site 207 is ~105 km southeast. Seismic reflection data can be used to tie stratigraphy between the three sites but with some uncertainty caused by unconformities and deformation. Site U1510 was chosen to determine the timing of Cenozoic folding on the southern Lord Howe Rise and to obtain stratigraphic information to constrain the timing of vertical tectonic movements and volcanism. At Site 592, a Quaternary to lower Miocene sequence of foraminifer-bearing nannofossil ooze and chalk overlies lower Oligocene to upper Eocene nannofossil ooze and chalk with volcanic ash. The boundary between the upper and lower units is a prominent unconformity clearly visible on seismic reflection data as a channeled erosion surface. The Neogene unit and its basal unconformity can be mapped from Site 592 to Site 207. At Site 207, however, Quaternary to middle Miocene foraminifer-bearing nannofossil ooze overlies middle Eocene to Paleocene foraminifer-bearing nannofossil ooze and chalk containing siliceous microfossils with clay content that increases downward. Cretaceous claystone overlies sandstone and Cretaceous rhyolite at the base of the sequence drilled at Site 207. Seismic reflection data used to map units near Sites 207 and 592 image reverse faults and volcanic centers. The faulting represents the “Tectonic Event of the Cenozoic in the Tasman Area” (TECTA). Site U1510 was chosen to sample strata adjacent to reverse faults, folds, and volcanic centers associated with this deformation. Three seismic stratigraphic units were identified. The upper seismic unit (1) has continuous moderate-amplitude reflectors with complex internal geometry. At Sites 207 and 592, the unit corresponds to Neogene and Quaternary strata. The middle seismic unit (2) is channeled near its top surface and characterized throughout by fanning low- to moderate-amplitude, continuous undulating reflectors. This unit has large lateral variations in thickness associated with folds and reverse faults that lie beneath. It is interpreted to be a syntectonic unit. Seismic Unit 2 correlates with lower Oligocene to upper Eocene strata at Site 592 but is missing at Site 207. Volcanic cones are identified on seismic reflection data and are inferred to be contemporaneous with seismic Unit 2, which is confirmed by the significant volcanic component in the lower unit at Site 592. The lower seismic unit (3) is characterized by moderate- or high-amplitude, continuous reflectors that are locally folded and reverse faulted. Seismic Unit 3 can be traced to Site 207, where it is sampled as the lowest sedimentary unit drilled. The unit is considerably thinner at Site 207 compared with at Site U1510. The primary drilling objectives at Site U1510 were to (1) sample the top and base of the middle seismic unit to constrain the minimum and maximum ages of folding, (2) sample the lower seismic unit to determine the pre-TECTA state of the southern Lord Howe Rise, and (3) look for evidence of volcanism and vertical movements (e.g., evidence of nearby shallow water at any age).