AIRPHOTO INTERPRETATION AS AN AID TO LITHO - STRUCTURAL MAPPING IN TROPICAL TERRAIN - THE NEW FEDERAL CAPITAL CITY SITE, ABUJA, NIGERIA

Yıl 1988, Cilt: 108 Sayı: 108, 65 - 75, 01.01.1988

Murat Avcı

Öz

The Federal Capital Development Authority of Nigeria requested that an engineering geological
investigation of the proposed New Federal Capital City Site at 1: 25.000 scale be carried out for suitability purposes.
Mapping with conventional field methods alone proved to be insufficient due to the concealed
terrain conditions in the area. Two different scales (1: 40.000 and 1:10.000) of aerial photographs were used
which have revealed three main bedrock units and the entire structural framework of the area. Airphoto interpretation
data shows lithological banding running NNE — SSW and fractures developed mainly in NW — SE
and NE — SW directions. Through this information a major tectonic event has been inferred, resulting from a
principal stress acting WNW—ESE.The directional frequency and the length of fractures show variations according
to rock type. The metaigneous rocks gave high fracture density and frequency values, whereas metasedimentary
rocks yielded low values of the same parameters. 

Anahtar Kelimeler

AIRPHOTO, LITHO, STRUCTURAL

Kaynakça

• Ball, E.,1980, An example of very consistent Brittle Deformation over a vide intracontinental area : The late Pan-African Fracture System of the Tuareg and Nigerian Shield.
• Blanchet, P.H.,1957, Development of Fracture Analysis as Exploration Method : Bull. Amer. Assoc. Petrol. Geol.,41,8.
• Friedman, M., 1972, Residual elastic strain in Rocks : Techtonophysics, 15, 297 - 330.
• Grant, N.K., 1971, A compilation of radiometric ages from Nigeria : Jour. Mining Geology, 6, 37 - 54.
• Henderson, G., 1960, Air - Photo Lineaments in Mpada Area, Western Province Tanganyika, Africa: Bull. Amer. Assoc. Petrol. Geol. 44.
• Hobbs et al. 1976, An Outline of Structural Geo- logy: John Wiley and Sons Inc., New York.
• Jeager, J.C. and Cook, N.C.W., 1969, Fundamentals of Rock Mechanics: Methuen & Co. London, 513.
• Krynine, P.D. and Judd, R.W. 1969, Principals of Engineering Geology and Geotechnics: McGraw- Hill, New York.
• Lattman, H.L.,1958, Technique of mapping geologic fracture traces and lineaments on aerial pho- tographs : Phot. Eng. 25.
• McCurry, P., 1976, The Geology of the Precambrian to Lower Paleozoic Rocks of Northern Nigeria: A review in C.A. Kogbe (ed.), Geology of Nigeria Elizabethan Fubl. Co.
• Moody, J.D. and Hill, M.J.,1956,, Wrench fault tec- tonics: Bull. Geol. Soc. Amer.,67.
• Norman, J.W. 1976, Photogeological fracture trace analysis as a subsurface exploration technique: Trans. Inst. Min. and Metal.85.
• Oversby, V.M.,1975, Lead isotopic study of Aplites from the Precambrian Basement Rocks near Ibadan, Southwestern Nigeria : Earth Planetary Sci, Letts., 27, 177 -180.
• Rahaman, M.A. et al.,1983, The Potassic - Granites of the Igbeti Area : Further Evidence of the Polycyclic Evolution of the Pan-African Belt in Southwestern Nigeria : Res. Pre Cambrian Geology.
• and Lancelot, (in press), Continental Crust Evolution in South-western Nigeria : Constraints Flow U/Pb Dating of Pre-Pan, African Gneisses: Res. Pre Cambrian Geology.
• Ray, R.G.,1960, Aerial photographs in geologic inter- pretation and mapping: USGS. Prof. Paper 373, Washington, D.C.
• Thomas, G.E.. 1974, Lineament-Block Tectonics : Williston - Blood Greek Basin : Am. Ass. Pet. Geol. 58, 7.
• Truswell, F.J. and Cope, R.N., 1963, The Geology of Parts of Niger and Zaria provinces : Geol. Surv. Nigeria Bull., 29, 52.
• U.A.B., 1979, Geology and engineering geology of the Federal Capital Territory : University of Ahmadu Bello, Zaria, Nigeria. UNIFE,1979, Geology and Engineering Geology of the Federal Capital City Site : University of Ife, Nigeria.
• USGS,1977, Preliminary Engineering Geologic report on selection of Urban Sites in the Federal Capital Territory, Nigeria-. Project Report Nigerian Investigations (IF) N — 1.
• Van Bremeen, O. et al, 1976, Age and Origin of the Nigerian Mesozoic Granites : a Rb — Sr Isotopic study : Contrib. Mineral Petrol., 50, 157 -172.
• Vielon, P. et al., 1976, Elements de Tectonique Ana- litique: Masson, Paris.