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Bedrock analysis reveals evidence for lost mountains from Antarctica's past

A new study led by University of Wisconsin-Oshkosh geologist Timothy Paulsen and University of Colorado Boulder thermochronologist Jeff Benowitz advances the understanding of the geologic history of Transantarctic Mountains bedrock, with implications for understanding the evolution of landscapes lying beneath the ice sheets covering Antarctica.

The team of researchers analyzed the chemistry of mineral grains commonly found in igneous rocks, like granite, from the Transantarctic Mountains. The research team includes other scientists from the University of Arizona, St. Louis University, The Ohio State University, and the University of Alaska Fairbanks.

The study was in Earth and Planetary Science Letters.

"Early exploration of the Antarctic continent revealed a surprising result, a 3500 km long mountain range with peaks over 4500 m crossing the Antarctic continental interior," said Paulsen, the lead author on the paper.

"This range was known as the 'great Antarctic horst' and is recognized today as the Transantarctic Mountains. These mountains currently restrict the East Antarctic ice sheet as it flows from East Antarctica to low elevations in the Ross Sea."

Yet there are significant questions about the past uplift history of the Transantarctic Mountains, as well as the rugged under-ice topography of Antarctica, which may have influenced the growth and behavior of ice sheets over time.

"The Antarctic ice sheets blanket and mask the bedrock geology of Antarctica," said Benowitz, a co-author on the paper. "The time-temperature evolution of Transantarctic basement rocks can provide important clues for understanding the development of the under-ice bedrock topography of Antarctica, especially ancient landscapes that predated the Cenozoic rise of the Transantarctic Mountains and how these older mountains possibly influenced glacial cycles."

The researchers' findings, based on an analysis of an exceptionally large data set from igneous rocks recovered from the Transantarctic Mountains, may signify a much more dynamic Antarctic landscape history than previously recognized, including added support for a glacial period around ~300 million years ago.

"Our new results suggest Transantarctic Mountain basement rocks experienced several punctuated mountain building and erosion events, creating surfaces along which ancient rocks are missing," Paulsen said. "These events are curiously associated with major plate tectonic changes along the margins of Antarctica.

"Based on our analyses, the older geologic history of the continent may have profoundly shaped the patterns of the modern landscape, which likely influenced cycles of glacial advance and retreat, and perhaps evolutionary steps in Earth's global ocean-atmosphere system."