in 2001, a small H4 chondrite, Frontier Mountain (FRO) 01149, was found on a glacially eroded surface near the top of Frontier Mountain, Antarctica, about 600 m above the present ice level. The metal and sulphides are almost completely oxidized due to terrestrial weathering. We used a chemical leaching procedure to remove weathering products, which contained atmospheric Be-10 and Cl-36 in a ratio similar to that found in Antarctic ice. The FRO 01149 meteorite has a terrestrial age of 3.0 +/- 0.3 Myr based on the concentrations of the cosmogenic radionuclides Be-10, Al-26 and Cl-36. This age implies that FRO 01149 is the oldest stony meteorite (fossil meteorites excluded) discovered on Earth. The noble gas cosmic ray exposure age of FRO 01149 is similar to 30 Myr. The meteorite thus belongs to the 33 Myr exposure age peak of H-chondrites. The bedrock surface on which FRO 01149 was found has wet-based glacial erosional features recording a former high-stand of the East Antarctic ice sheet. This ice sheet evidently overrode the highest peaks (> 2800 m a.s.l.) of the inland sector of the Transantarctic Mountains in northern Victoria Land. We argue that FRO 01149 was a local fall and that its survival on a glacially eroded bedrock surface constrains the age of the last overriding event to be older than similar to 3 Myr. The concentrations of in-situ produced cosmogenic Be-10, Al-26 and Ne-21 in a glacially eroded bedrock sample taken from near the summit of Frontier Mountain yield a surface exposure age of 4.4 Myr and indicate that the bedrock was covered by several meters of snow. The exposure age is also consistent with bedrock exposure ages of other summit plateaus in northern Victoria Land.
|Autori:||Welten K C; Folco L; Nishiizumi K; Caffee M W; Grimberg A; Meier M; Kober F|
|Titolo:||Meteoritic and bedrock constraints on the glacial history of Frontier Mountain in northern Victoria Land, Antarctica|
|Anno del prodotto:||2008|
|Digital Object Identifier (DOI):||10.1016/j.epsl.2008.03.052|
|Appare nelle tipologie:||1.1 Articolo in rivista|