Styles of positive inversion tectonics and kinematics of inversion tectonics
Speaker: Jia-Fu Zhang
Abstract
The Apennines chain in Italy and its adjacent Adriatic foreland indicates that the styles of positive inversion tectonics and the modes of interaction between the extensional and the subsequent compressive structures vary. The contraction deformation induced by the mainly north-directed convergence of Africa/Adria with respect to the European plate promoted the closure of various arms of the Atlantic and the Neo-Tethys oceans, which opened in different times and with distinct orientations.
Pre-reverse normal faults were commonly deformed by later thrusts. This suggests that these shallow and steeply-dipping discontinuities were not suitable to be reutilized by the superficial thin-skinned thrust faults propagating within the sedimentary cover. In contrast, presumably late Paleozoic and Mesozoic W-dipping normal faults appear moderately reactivated in the Adriatic foreland, and strong positive inversion tectonics affect the deeper and buried structural levels of the Apennine chain.
Positive inversion tectonics involves the reversal of extensional fault movement during contraction tectonics. Growth fault activity may be graphically displayed using thickness changes in stratigraphic intervals from fault footwall to hanging wall. The point of change from net extension to net contraction is the null point.
Finally, the contrasting styles of interactions of the pre-existing normal faults with later thrusts strictly result from the different evolution of the Apennine chain and the combined thin- and thick-skinned modes of deformation of the stretched lithosphere of the Adria plate.
Reference
Williams, G.D., Powell, C.M., Cooper, M.A., (1989) Geometry and kinematics of inversion tectonics. In: Cooper, M.A., Williams, G.D. (Eds.), Inversion Tectonics. Geological Society of London , Special Publication, 44, pp. 3–15.
Scisciani, V., (2009) Styles of positive inversion tectonics in the Central Apennines and in the Adriatic foreland: Implications for the evolution of the Apennine chain (Italy), Journal of Structural Geology, In Press, Corrected Proof, Available online 15 April 2009, p. 1-19.