Eocene Tectonic Change in the South Pacific Caused Exhumation of the Transantarctic Mountains in Northern Victoria Land, Antarctica

Apatite fission‐track and (U‐Th)/He data indicate rapid exhumation of northern Victoria Land at 40–30 Ma, correlating with opening of Adare Trough at 43–28 Ma. Exhumation was greatest close to the Ross Sea, consistent with other regions of the Transantarctic Mountains. We find no evidence for tectonic activity during the interval 70–43 Ma at inland fault systems, so we infer the region behaved as a coherent block that was tilted or/and warped upward near the coastal range front at 43–28 Ma but was inactive from 70 to 43 Ma. The youngest single‐grain apatite (U‐Th)/He ages are consistent with fission track ages but single‐grain age dispersion limits their usefulness. We suggest a 4‐stage tectonic evolution. At 80–53 Ma, the Australia‐Antarctica plate boundary did not connect to South Pacific spreading ridges, but a zone of diffuse rifting connected Wilkes Basin to the Antarctic Peninsula. At 53–43 Ma, oceanic ridge‐transforms connected the Southeast Indian Ocean with South Pacific, the Tasman Sea stopped spreading, and intra‐Antarctic motion is required but did not involve northern Victoria Land. At 43–28 Ma, Adare Trough opened, and the Transantarctic Mountains were rapidly exhumed. The intra‐Antarctic plate boundary has been inactive since 28 Ma.