Investigating sediment thicknesses with geophysics in the East-African Rift Valley

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When aiming at the reconstructing of the paleoclimate, applied geophysical techniques can assist with the identification and definition of possible paleoenvironmental archives such as sedimental deposits.

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In 2014 and 2015, a group of geophysicists from the University of Cologne investigated

Marc Seidel, PhD Candidate in A2

Marc Seidel, PhD Candidate in A2

three sedimentary basins within the East ­African Rift Valley using 2D transient electromagnetics (TEM) and electrical resistivity tomography (ERT). Lake Chew Bahir (“Salty lake” in Amharic, approx. 500 m a.s.l.) is a 30 km x 70 km saline mudflat that episodically fills with water during rainy season. According to airborne gravity and seismic reflection data, the thickness of its sedimentary deposits is assumed to be of several kilometers. Therefore, the basin potentially provides sedimentary archives that extend far beyond the Quaternary. The source area of Bisare River is located within the Hobitcha Caldera near Wolaita Sodo in southern Ethiopia. Former sedimentological results indicate a continuous sedimentation process and Tephra layers. The double crater system of the Dendi Lakes is located at Mount Dendi (3,270 m asl) 80 km west of Addis Ababa. First drillings revealed holocene deposits within the lake sediments. Our results indicate sediment thicknesses comprising quaternary sediments.

The recorded data was processed using the software AarhusInv from the Hydrogeophysics Group of the University of Aarhus, Denmark. Here, all data and models are inverted as one system, producing layered solutions with laterally smooth transitions. The models are regularized through lateral constraints that tie interface depths or thicknesses and resistivities of adjacent layers. These inversion schemes are well suited for data taken in sedimentary environments.

Event Information:

Date, Time: 27/06/2016, 14:00 h – 14:45 h

Location: Room S12, Seminargebäude (Building 106), Universitätsstraße 37 , Cologne

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