Analysis of Mesoscopic structures at Mersing and Tanjung Kempit, Johore, Peninsular Malaysia

The metasedimetary rocks of possible Upper Palaeozoic age at Mersing and Tg. Kempit are multiply deformed. Using overprinting criteria as well as fold style and orientation, three phases of folding have been recognized, the second phase folds (F2) being predominant. The structural evolutionary sequence in both the areas is similar, the first phase folds (F1) are coaxially refolded by F2 and F3 folds are later superposed on both Fl and F2. Macroscopically, F1 and F2 folds are nonplane noncylindrical and F3 folds appear to be plane noncylindrical. The structural trends of the two areas are at variance. At Mersing. the F1 and F2 axial planes strike mainly northwesterly and axial plunge is towards southeast or northwest, while the trends of the F1 and F2 axial planes and axial plunge at Tg. Kempit are N to NNE. F1 and F2 axes at Mersing are dispersed. The dispersion pattern may be interpreted as due to the superposition of F3 folds of slip-type, the slip plane being subvertical and E-W trending with subhorizontal westerly a3 kinematic axis. Alternatively, bending of the crustal block on a subvertical axis may be responsible for the dispersion of F1 and F2 as well as the development of F3 folds. The difference in structural orientation between Mersing and Tg. Kempit is also explicable in terms of crustal bending. The postulated crustal bending may be envisaged as due to strike-slip motions