Tracing Along-Strike Structural Continuity of the Neoproterozoic Allaqi-Heiani Suture, Southern Egypt using Principal Component Analysis (PCA), Fast Fourier Transform (FFT) and Redundant Wavelet Transform (RWT) of ASTER Data
We have used the visible and near infrared (VNIR) and short wave infrared (SWIR) bands of the advanced space-borne thermal emission and reflectance radiometer (ASTER) to trace along-strike structures in the ophiolite-decorated Neoproterozoic Allaqi-Heiani Suture in southern Egypt. The suture is E-trending in the west, changes to N-trending in its central part, and E-trending further east. The western part of the suture is defined by a fold and thrust belt dominated by an autochthon in the south followed by a southern, central and northern allochthons that were emplaced top-to-the-south. Tracing along-strike structures in the Allaqi-Heiani Suture has been a challenging task due to structural complexity and change of structural style.
Principal component analysis (PCA), fast Fourier transform (FFT), and redundant wavelet transform (RWT) are used to identify ophiolite components such as talc carbonate schist, gabbro, and serpentinite as well as Neoproterozoic ductile structures to trace along-strike continuation in the Allaqi-Heiani Suture. (1) The PCA is performed on the 9 x 9 covariance matrix of the ASTER VNIR and SWIR bands. PC5 is selected because the ophiolite components and the Neoproterozoic ductile structures are best emphasized. (2) The FFT is performed on PC5 to reduce noises and mosaicking boundaries of the ASTER scenes. (3) The RWT is performed to enhance the contrast between ophiolite components and the surrounding rock types.
This work helped in tracing structures along the Allaqi-Heiani Suture and revealed structural features that have not been identified before: (1) Some folds associated with the S-verging fold and thrust belts are periclinal folds that might be associated with nappe emplacement. (2) Truncation of structures associated with the S-verging fold and thrust belts occurs along NNW-trending sinistral strike-slip shear zones that swing at their extreme ends to become parallel to the truncated structures. (3) Presence of N-trending folds close to the NNW-trending sinistral strike-slip shear zones. (4) Presence of N- and NE-trending brittle faults younger than the Neoproterozoic ductile structures. Nappes identified in the west are traced into the central part of the suture allowing for subsequent modification by younger structures. The difference in structural styles along the suture might be due to development of frontal and lateral ramps along the traces of the orogen front. This was followed by superimposition of E-W shortening to produce N-trending folds that are localized close to the lateral ramps. Subsequently, N- and NE-trending brittle faults were developed and deformed early Neoproterozoic ductile structures.
D. Ren and M. G. Abdel Salam, "Tracing Along-Strike Structural Continuity of the Neoproterozoic Allaqi-Heiani Suture, Southern Egypt using Principal Component Analysis (PCA), Fast Fourier Transform (FFT) and Redundant Wavelet Transform (RWT) of ASTER Data," Journal of African Earth Sciences, vol. 44, no. 2, pp. 181-195, Elsevier, Feb 2006.
The definitive version is available at http://dx.doi.org/10.1016/j.jafrearsci.2005.10.010
Geosciences and Geological and Petroleum Engineering
Keywords and Phrases
ASTER; Geological Mapping; Proterozoic; Remote Sensing; Structural Geology; Suture Zone; Africa; Allaqi-Heiani Suture Zone; Egypt; North Africa; FFT; Neoproterozoic Allaqi Suture; PCA; RWT; ASTER (Computer file); Fourier transformations; Principal components analysis
International Standard Serial Number (ISSN)
Article - Journal
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