Seismic investigations of Laguna Potrok Aike

Description:

Laguna Potrok Aike is a small lake located in southern Patagonia (Argentina), at 52°S within a 770 ka old maar of the Pali Aike Volcanic Field. During the last years, it has been focus of detailed geochemical, geological and geophysical studies within the framework of the PASADO project. Southern South America, the only landmass between 38°S and Antarctica, is a key location for understanding paleoclimatic changes on regional to global scales mainly for two reasons:

Studies on the lacustrine sediments allow

• Patagonia is known as the dominant source area of aeolian dust in the southern hemisphere, and
• Patagonia is located at the present day boundary between the southern Westerlies and the Antarctic Polar Front.

Enhanced aeolian supply of terrestrial derived iron to the biota of the Southern Ocean during glacial times is suspected to be an important contributory mechanism to the low mixing ratios of atmospheric CO2. Iron is the limiting element controlling oceanic production and thus uptake of atmospheric CO2 in the southern ocean. A better knowledge of short and long-term changes of continental climate conditions in Patagonia is fundamental to better understand the variability of dust transport to the ocean, fertilization and changes in the global CO2 budgets.

Patagonia is located at the present day boundary between the southern Westerlies and the Antarctic Polar Front. Between 45°S and 55°S strong westerly winds drive the Antarctic Circumpolar Current, the strongest ocean current on Earth. As atmospheric and ocean circulation are closely linked, the southern ocean plays an important role in transmitting climate anomalies around the globe. Therefore, knowledge about variations in strength and position of the Antarctic Circumpolar Current is crucial for the understanding of our climate system. It is expected that changes in causes and feedbacks of the Antarctic Circumpolar Current leave distinct imprints in southern Patagonian paleoclimatic records, which make them ideal to study such variability.

Laguna Potrok Aike is highly susceptible to (paleo)climate changes and, therefore, is a continental key location to better understand natural variability of dust transport to the southern ocean and the wind-induced Antarctic Circumpolar Current system. The lake has the potential for a continuous undisturbed sedimentary archive of geological, environmental and climatical processes spanning the last 1 Ma. This record represents one of the longest and most continuous lake archives for non-tropical South America and the entire southern hemisphere. It is, therefore, a potential target for continental deep drilling (ICDP).

Recent seismic data (pre-site survey for deep drilling) indicate the boundary between the lacustrine sediments and the bedrock at a depth of about 300 meters below lakefloor by combining different lacustrine seismic methods (multi-channel reflection seismics, refraction seismics) and instruments (streamer, sonobuoys, land stations). Further seismic investigations are now needed to better understand the lake geometry and sedimentary fill and to find the most promising drilling sites.

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