ROSS ICE SHEET DYNAMICS: CLUES FROM DETRITAL THERMOCHRONOLOGY AND SEDIMENTARY PETROGRAPHY

The influence of Antarctic ice sheets on the global climate system during the Cenozoic has been intensely investigated in the last years, especially after the successful offshore drilling projects in the western Ross Sea. This area is crucial for a better understanding of the ice dynamics as it records the evolution of both East and West Antarctic Ice Sheets (EAIS and WAIS). The WAIS is smaller than the EAIS but it is supposed to be capable of ultra-fast melting because of its greater sensitivity to sea temperature. Thus, the breath of WAIS in the past, particularly during periods considered warmer than today, such as during the Oligocene, is a key issue to monitor the glacial dynamics in Antarctica.

Detrital geochronology, sedimentary petrography and, in general, data about provenance of sediments, allow inferences to be made about the ice-flow patterns as they provide information on the source-to-sink path. In this work, we combine several data from Andrill (AND-2A and AND-1B) and Cape Roberts wells and compare them with evidences from the putative source rocks located along the Transantarctic Mountains (TAM). This dataset gives a solid picture of erosional pattern along the TAM from Oligocene to Miocene.

All the data point to a general north-to-south ice flow but relevant variations of source rock appear through time. Taking into consideration tectonic activity along the TAM, we relate these variations to fluctuations of Ross Ice Sheet as far back as the early Oligocene. In other words, the sedimentary signature is strongly influenced by climatically-controlled expansions of a grounding WAIS into the Ross embayment which repetitively extended as far as the the Cape Roberts drilling site.