Post Middle Miocene Tectonomagmatic and Stratigraphic Evolution of the Victoria Land Basin, West Antarctica

Abstract

Seismic reflection and borehole data are used to create structure maps of four regional and three local unconformities that constrain the post middle Miocene evolution of the Victoria Land Basin (VLB), which is located in the western Ross Sea within the Late Cretaceous through Quaternary West Antarctic Rift System. Isochore maps of the strata between unconformities show that rifting was mostly amagmatic between 12 to 7.6 Ma, with subsidence controlled by faults bordering the northwest margin of the basin and in a tectonic zone along the southern basin axis known as the Terror Rift. Depocenters surrounding volcanic features in strata younger than 4.3 Ma indicate an increasing influence of flexure due to volcanic loading on the subsidence pattern in the southern VLB after this time. The intervening period, from 7.6 to 4.3 Ma, was a transitional period during which both extensional tectonism and magmatism exerted strong influences on basin morphology. Since 4.3 Ma, a series of flexural subbasins formed successively at different times and positions as the different volcanic centers that built Ross Island erupted. In composite, these subbasins form a flexural moat surrounding Ross Island and smaller volcanic centers immediately to the north. The widths of these basins indicate that the flexural rigidity of the lithosphere ranges from 0.20 × 1019 to 12.96 × 1019 N‐m (elastic thickness 0.6 to 2.4 km).

Neogene Development of the Terror Rift, Western Ross Sea, Antarctica

“…(2013) and Wenman et al. (2020), northward within the basin, and to the eastern shoulder of the central and northern rift. The Ri unconformity (∼4.6 Ma) could not be directly correlated north from the area near ANDRILL 2A, so we interpreted a regional unconformity farther north as Ri (Figure 3).…”

“…Wenman et al. (2020) used the age ranges of 10.8–13.6 Ma for reflector Rg, 7.3–7.8 Ma for reflector Rh and 4.0–4.6 Ma for reflector Ri based on work by G. Wilson et al. (2012) and Naish et al.…”

“…The Rg (∼13 Ma) and Rh (7.6 Ma) unconformities were correlated from over-ice seismic reflection profiles in the McMurdo Sound area, as discussed in Pekar et al (2013) and Wenman et al (2020), northward within the basin, and to the eastern shoulder of the central and northern rift. The Ri unconformity (∼4.6 Ma) could not be directly correlated north from the area near ANDRILL 2A, so we interpreted a regional unconformity farther north as Ri (Figure 3).…”

“…C. Fielding, 2018;Horgan et al, 2005;Naish et al, 2007;Pekar et al, 2013). Wenman et al (2020) used the age ranges of 10.8-13.6 Ma for reflector Rg, 7.3-7.8 Ma for reflector Rh and 4.0-4.6 Ma for reflector Ri based on work by G. Wilson et al (2012) and Naish et al (2007) We have retained the different names and ages from core holes of these sets of stratigraphic nomenclatures in the text and in the figures. The RSU unconformities are correlated by using all the available data from the Eastern Basin across the Central High to the area of DSDP 273 in the Central Trough ( Figure 4; Sorlien et al, 2016Sorlien et al, , 2019.…”

Flexural Subsidence Around Ross Island, West Antarctica

“…Profiles crossing each of the sub‐basins were extracted from the decompacted isopach grids of Wenman et al. (2020). These sub‐basins form elongate depocenters located offshore and within a few tens of kilometers of each of the major volcanic centers, and are interpreted to be flexural sub‐basins formed as a result of volcanic loading on the island.…”