Lake sediments have been found to carry a natural record of many environmental and geological processes which have occurred on time scales of hundreds and thousand years. They are ideal recorders of high-resolution paleo-environmental changes, because of high sedimentary rates and weak physical disturbance.
Under specific sedimentary conditions, lake-sediments preserve a record of variations in the direction and strength of Earth’s geomagnetic field. In addition, the type, concentration and grain-size of magnetic minerals found in lake-sediments vary according to a variety of processes operating in response to changes in climate, human activity and limnology. Therefore, examination of lake sediments enables inferences to be made about past environments.
In this talk, I’ll present magnetic measurement results of a ~10.7 m sediment core recovered from Lake Dendi. Lake Dendi (08°50’N, 38°01’E) is a caldera lake located on the Ethiopian Plateau at 2836 m a.s.l and approximately 86 km southwest of Addis Ababa. The lake partly fills a two-shallow adjacent structures (in a shape of number 8, ~2.4 km in diameter and 48 to 56 m depth) that was formed by the collapse of the Dendi Mountain volcano (~3267 m). Presence of early human interaction at high altitude that can be traceable back to the Early to Middle Stone Age (MSA) is documented by the discovery of ESA-MSA-LSA obsidian tools at the site. The lake is also a tributary of the Abay river (the Blue Nile), the evaporation is compensated for by rain and spring water in-flows from it’s catchment.
Focus in the talk will be given mainly to magnetic results [magnetic susceptibility (Χ), Natural, anhysteretic and isothermal remanent magnetization (NRM, ARM, IRM), coercivity parameters (S-ratio, and hysteresis)] of the first ~10.7 m core recovered from a depth of ~50 m of Lake Dendi and additional sampling of the catchments (sediments, ash deposits and pyroclastic rocks). In addition summary results of core facies descriptions, MSCL logging core data (MS, gamma density, P-wave velocity) and Multi-elements analysis (Si, K, Ca, Fe, Ti, etc.) based on XRF will be presented.
Date, Time: 12/05/2014, 17:45 h – 19:00 h
Location: Room S12, Seminargebäude (Building 106), Universitätsstraße 37 , Cologne