3D analogue modelling of transtensional pull-apart basins: comparison with the Cinarcik basin, Sea of Marmara, Turkey

Scaled 3D sandbox models have been used to investigate the 3D geometry and evolution of transtensional pull-apart basins. In this paper two representative analogue models were constructed to simulate the evolution of a 5^o transtensional pull-apart basin formed above an underlapping, 45^o strike-slip releasing bend basement stepover. Model 1 had 1:1 relative motion between opposing plates whereas Model 2 had 2:1 relative plate motion. In both experiments, a rhomboidal pull-apart basin developed with one central depocentre that was bounded by en-echelon basin margin faults. The early stages of basin evolution were characterised by basin subsidence and the nucleation of en-echelon normal faults. In the latter stages strike-slip occurred along the en-echelon normal faults, a cross-basin strike-slip fault formed and incremental basin subsidence decreased. Model 1 developed a symmetric basin whereas Model 2 developed a weakly asymmetric basin that had very active basin margin faults above the faster moving plate and a segmented cross-basin strike-slip fault system. The models were compared to the Cinarcik basin, Sea of Marmara. Both the analogue models and the natural prototype were characterised by basin margins bounded on one side by a simple, steeply-dipping normal fault and on the other side by an en-echelon array of steeply-dipping normal faults. The Model 1 showed similarities to the central and eastern part of the Cinarcik basin.