Large Scale Extensional Tectonics in the Basin and Ranges USA and Western Anatolia, Turkey

Collisional tectonics preceded large-scale extension and metamorphic core complex formation In the Basins and Ranges of North America and the Aegean region of Eastern Europe. It occurred during the Cretaceous Sevier Orogeny in the Basin and Ranges and still continues to the NE of the region. In the Aegean region, collisional tectonics occurred during the Eocene Pontide Orogeny and continues today to the NW in Greece and to the NE in Eastern Turkey. In the Aegean region, subduction slab roll-back along the Hellenic arc and associated lateral extrusion is responsible for the large-scale extensional tectonics and associated metamorphic core complex development. In the basins and ranges, the NW movement of the Pacific plate with respect to the North American plate along the San Andreas fault zone is largely responsible for the basin and range extension. There are two important questions related to the large scale extensional tectonics: 1) what happens to the earlier formed large thrust faults during the extensional tectonics? and 2) How does rifting follow large scale continental extension along the collisional zones? Our work in the Death Valley Region of the Basins and Ranges suggest there are several earlier thrust faults that have been reactivated during the extension, including the Badwater Turtleback fault, and Bat Mountain fault. Our recent work Western Anatolia, Turkey suggest the Selimiye Shear zone of the Southern Menderes Massif has been reactivated during the Cenozoic Extension in the region. The reactivated structures in both regions tend to have an original low angle thrust geometry and dips ~30 degrees or less. However, extensional tectonics in both regions has also formed its steeply dipping (~60 degrees) normal faults. The process that lead to rifting after collisional tectonics is much more complex and are at present poorly understand. It involves several stages of magma generation and intrusive and volcanic activities.