Article : DC resistivity and seismic refraction survey across the SE margin of Lake Ngami, NW Botswana
Authors : Yamasaki, K.Department of Earth and Planetary Sciences, Faculty of Science, Kobe University, Nada, Kobe, Japan, email@example.com, Teisseyre, R.Institute of Geophysics, Polish Academy of Sciences, Warszawa, Poland, firstname.lastname@example.org, Herak, M.University of Zagreb, Faculty of Science and Mathematics, Department of Geophysics, Zagreb, Croatia, email@example.com, Rosyidi, S. A. P.Department of Civil Engineering, Muhammadiyah University of Yogyakarta, Yogyakarta, Indonesia, firstname.lastname@example.org, Moustafa, S. S. R.Department of Seismology, National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt, email@example.com, Tenzer, R.School of Surveying, Faculty of Sciences, University of Otago, Dunedin, New Zealand, firstname.lastname@example.org, Rabeh, T.National Research Institute of Astronomy and Geophysics, Cairo, Egypt; Center of Geophysics, Faculty of Science IGIDL, Lisbon University, Lisbon, Portugal, email@example.com, Węglarczyk, S.Cracow University of Technology, Faculty of Environmental Engineering, Kraków, Poland, firstname.lastname@example.org, Huo, Y.China University of Geosciences, Beijing, China, email@example.com, Shemang, E. M.Department of Geology, University of Botswana, Gaborone, Botswana, firstname.lastname@example.org,
Abstract : Seismic refraction survey and DC resistivity measurements were made across the margin of the Lake Ngami. The structure and stratigraphy at the lake were determined. High resolution aeromagnetic data showed a prominent anomaly coinciding with the Kunyere Fault. Estimated depths to magnetic sources are increasing towards the lake. Two velocity layers were mapped. The top layer (500 m/s) is thin outside the lake and thicker inside the lake. The underlying layer (3125 m/s) has undeterminable thickness. Resistivity sounding results inside the lake showed that the low velocity layer has four sub-units: dry hard clays; diatomaceous earth; soft clays interlayered with silts; and wet whitish clays interlayered with silts. Normal faults were mapped along the profile with a total displacement up to 50 m. The results of the study indicate that the formation of the Lake Ngami basin was structurally controlled and probably initiated by the tectonics of the Okavango Rift Zone.
Bibliography : Briggs, I.C. (1974), Machine contouring using minimum curvature, Geophysics 39, 39-48.
DWA (2004), Department of Water Affairs, Maun Groundwater Development Project Phase II; Resources Assessment and Wellfield Development, Final Report, Ministry of Minerals, Energy and Water Resources, Gaborone, Botswana, 259 pp.
Gumbricht, T., T.S. McCarthy, and C.L. Merry (2001), The topography of the Okavango Delta, Botswana, and its tectonic and sedimentological implications, South African J. Geology 104, 243-264.
Interpex (2006), IXRefrax™, Version 1.05 for Windows.
Kampunzu, A.B., M.G. Bonhomme, and M. Kanika (1998), Geochronology of volcanic rocks and evolution of the Cenozoic Western Branch of the East African Rift System, J. African Earth Sc. 26, 441-461.
Kinabo, B.D., E.A. Atekwana, J.P., Hogan, M.P. Modisi, D.D. Wheaton, and A.B. Kampunzu (2007), Early structural development of the Okavango rift zone, NW Botswana, J. African Earth Sc. 48, 125-136.
McCarthy, T.S., I.G. Stanistreet, and B. Cairncross (1991), The sedimentary Dynamics of active fluvial channels on the Okavango fan, Botswana, Sedimentology 38, 471-487.
McCarthy, T.S., R.W. Green, and N.J. Franey (1993), The influence of neo-tectonics on water dispersal in the northeastern regions of the Okavango swamps, Botswana, J. African Earth Sc. 17, 23-32.
Modisi, M.P. (2000), Fault system at the southeastern boundary of the Okavango Rift, Botswana, J. African Earth Sc. 30, 569-578.
Modisi, M.P., E.A. Atekwana, A.B. Kampunzu, and T.H. Ngwisanyi (2000), Rift kinematics during the incipient stages of continental extension: Evidence from the nascent Okavango rift basin, northwest Botswana, Geology 28, 939-942.
Redpath, B.B. (1973), Seismic Refraction Exploration for Engineering Site Investigations. NTIS, US Department of Commerce.
Reid, A.B., J.M. Allsop, H. Granser, A.J. Millet, and I.W. Somerton (1990), Magnetic interpretation in three dimensions using Euler deconvolution, Geophysics 55, 80-91.
Ringrose, S., A.B. Kampunzu, B.W. Vink, W. Matheson, and W.S. Downey (2002), Origin and palaeo-environments of calcareous sediments in the Moshaweng dry valley, southeast Botswana, Earth Surf. Proc. Land. 27, 591-611.
Scholz, C.H. (1975), Seismicity, tectonics and seismic hazard of the Okavango Delta, Botswana. Final report to the United Nations Development Programme on the Okavango Delta, Investigation of the Okavango as a primary water source for Botswana, Food and Agricultural Organization.
W_Geosoft (2004), WinsismTM 10.4, Version 10.3.7 for Windows.
Qute : Yamasaki, K. ,Teisseyre, R. ,Herak, M. ,Rosyidi, S. A. P. ,Moustafa, S. S. R. ,Tenzer, R. ,Rabeh, T. ,Węglarczyk, S. ,Huo, Y. ,Shemang, E. M. ,Shemang, E. M. , DC resistivity and seismic refraction survey across the SE margin of Lake Ngami, NW Botswana. Acta Geophysica Vol. 57, no. 3/2009