Last exposure process of the Larsemann Hills and adjacent area, East Antarctica, based on bedrock exposure ages

Abstract

The East Antarctic Ice Sheet (EAIS) is the largest glacial system in the world, and the evolution history of the EAIS strongly affects global climate change. As one of the most extensive ice-free areas in coastal East Antarctica, the Larsemann Hills represent an important site for understanding the glacial evolution of East Antarctica. Generally, the last exposure process in the Larsemann Hills was considered to occur in the last glacial period. However, the initial time of the last exposure process in the Larsemann Hills remains unclear. This study presents the 10Be exposure ages of eight bedrock samples with glacial striae, which means that the original uneroded surfaces are preserved, from the Larsemann Hills and neighboring areas. The 10Be exposure ages ranging from 70.7 ± 4.7 to 13.5 ± 1.2 ka indicate that the Larsemann Hills have become ice-free since MIS4. The 10Be exposure ages with the characteristics of zonal distribution in the E–W direction and ages generally change from north to south, which reveals the combination of glacial retreat and topography differences. The activity of the ice sheet in the Larsemann Hills did not respond to the Last Glacial Maximum (LGM). In contrast, the deglaciation in the Larsemann Hills occurred as a diachronous process during the global last glacial periods, which began long before the LGM and lasted after the LGM. According to the exposure ages in the Larsemann Hills and the distance from the edge of the ice sheet, the average glacial retreat rate since MIS4 has been 71.57 m/ka.