EVIDENCE FOR EXTENSIVE VOLCANISM IN THE DEGLACIATION OF THE HUGO-ANVERS ISLAND TROUGH

Known volcanic systems in the Antarctic Peninsula region include Deception and Brabant Islands. However recent studies show an anomalous area in which pyroclastic grains appear far West of either of these volcanic sources. This study aims to provide evidence of a volcanic event that sparked deglaciation within the Hugo-Anvers Islands.

Efforts initially were to focus on a lithologic analysis of five cores taken proximal to the Hugo-Anvers Trough in 2012. These cores were split into sub samples every five centimeters. The samples studied ranged roughly 50 cm above the contact between the marine sediments and the glacial till, down to the base of the glacial till.

Within the investigated samples, three distinct volcanic grains were identified. Those being pumice, basaltic volcanics, and glassy micro vesicular volcanics.

Pumice was characterized by its highly vesicular, light colored, dull volcanic grains. The basaltic volcanics were much darker grains, and were dull in color comparatively to the glassy micro vesicular grains. Finally the glassy micro vesicular grains were dark in color, but extremely lustrous.

Due to the nature of the pyroclastic grains, the sample size of 0.25-0.5 mm was chosen to provide a relative composition of the core. The lithologic analysis confirmed the presence of volcanics with a pyroclastic presence upwards of 25% within certain samples. Pyroclastic grains were found almost exclusively within the marine sediments overlaying the glacial till.

Winds within the study area have a travel pattern from west to east. The two major volcanic sources within the area, Deception Island and Brabant Island, lay to the East of the core sites. This indicates either a western location, otherwise undocumented, or an alternate transport method allowing volcanic grains to be found at the coring location.

Initially the presence of volcanics within the marine sediment overlying the glacial till pointed towards the possibility of ice-rafted debris from Brabant Island. However, initial lithologic analysis of these cores reveal grains that do not resemble the volcanic rocks found at Brabant Island, rather they more closely resemble fine volcanic detritus of air fall origin, possibly from a large eruptive event.