A MULTIPROXY STUDY OF LAKE ANONIMA, VEGA ISLAND, ANTARCTICA

MARCOS A.E. CHAPARRO; FRANCISCO CÓRDOBA; KARINA L. LECOMTE; JOSÉ D. GARGIULO; NADIA T. MANOGRASSO CZALBOWSKI; JUAN M. LIRIO; MAURO A.E. CHAPARRO

Mérida

Congreso; 12th Scientific Assembly IAGA 2013; 2013

The Lake Anonima is a small closed hydrological basin, which is located over moraine deposits in a periglacial ice free area from Vega Island (NE Antarctic Peninsula, 63.8°S; 57.3°W). In this contribution, sedimentary and hydrochemical processes in the lake and surroundings were investigated, focussing on magnetic proxies for environmental processes, and their relation with the depositional dynamic (geology and geomorphology on modern depositional processes, lake currents, tributaries). After a detailed bathymetry, lake sediments were collected from a grid of 61 sites, sub-sampled and studied using rock-magnetic (magnetic susceptibility, anhysteretic and isothermal remanent magnetisation), geochemical (TOC, TIC), sedimentological (grain size) and multivariate statistical techniques. In addition, some physicochemical characteristics of snow, river and lake water samples (pH, electrical conductivity, temperature, alkalinity, total dissolved solids and dissolved oxygen) were measured in situ and laboratory. The system shows high hydrological and hydrochemical dynamic behaviour during summer (e.g. changes in size and level). Physicochemical data and field observations indicate dominant evaporation processes over infiltration ones, as well as water input is mostly supplied by snow/ice meltwater rather than by streams. The multiproxy analysis suggests that tributaries around the lake basin contribute to the spatial sediment variations; e.g.: mass-specific magnetic susceptibility values (63.4-166.7 x10-8 m3 kg-1) show the influence of a stream that develops a delta in the SW coast. In particular, magnetic proxies reveal differences between clay-silt, fine and medium sand fractions; as well as between depositional areas as consequence of bottom morphology and the influence of episodic inflow into this lake. This multi parameter analysis not only contributes to understand the present day sedimentary processes, but also it can help to understand environmental and magnetic changes in the past.