Presentation on theme: "Fault systems and Paleo-stress tensors in the Indus Suture Zone (NW Pakistan) Gerold Zeilinger, Jean- Pierre Burg, Nawaz Chaudhry, Hamid Dawood & Shahid."— Presentation transcript:
Fault systems and Paleo-stress tensors in the Indus Suture Zone (NW Pakistan) Gerold Zeilinger, Jean- Pierre Burg, Nawaz Chaudhry, Hamid Dawood & Shahid Hussain
Outline Overview Field examples Data Method Results Interpretation
Analysis of fault-striations to document the dynamics of the Indus Suture Zone during hypercollision. –The area straddles the Main Mantle Thrust and comprises three main units. The Indian unit: granodiorite and intensely foliated and folded gneisses. The lower Kohistan unit: ultramafic and mafic rocks. The Chilas Complex: gabbro-norite and diorites. Overview
Example 1 W E 305/36
Example 2 E W
Superposed Striations S N 290/18 274/17 011/03
Method chronological sequence –field relationships between fault and striation sets. regional stress tensor –250 measurements processed as one single data set. The 4 best tensors have the highest number of < 30° misfit angles, and close to 0°. faults fitting the regional stress tensors –data from each site separated from smallest misfit angle of each fault/striation pair for the 4 reference regional tensors. local deviations from the regional stress tensors –local stress tensor orientation from new random tensor search procedure on separated data sets.
Example of raw data NE - Continuation is not shown here
Example of processed data NE - Continuation is not shown here
Interpretation Population 1: Higher temperature faults (the oldest ones). SSE-NNW compression fits the Himalayan convergence. Population 2: E-W compression - Formation of the Nanga Parbat crustal antiform. Population 3: Extension shortly afterwards. Collapse in the hanging walls of the Nanga Parbat crustal antiform? Population 4: Compression fitting the present stress field (Patan earthquake, December 1974).