Solid Earth Discuss., https://doi.org/10.5194/se-2019-49 Manuscript under review for journal Solid Earth Discussion started: 25 March 2019 c Author(s) 2019. CC BY 4.0 License. Deformation of intrasalt competent layers in different modes of salt tectonics Mark G. Rowan1, Janos L. Urai2, J. Carl Fiduk3, Peter A. Kukla4 1Rowan Consulting, Inc., Boulder, CO 80302, USA 5 2Institute for Structural Geology, Tectonics and Geomechanics, RWTH Aachen University, 52056 Aachen, Germany 3Fiduk Consulting LLC, Houston, TX 77063, USA 4Geological Institute, Energy and Mineral Resources, RWTH Aachen University, 52056 Aachen, Germany Correspondence to: Mark G. Rowan (
[email protected]) 10 Abstract. Layered evaporite sequences (LES) comprise interbedded weak layers (halite and, commonly, bittern salts) and strong layers (anhydrite and usually non-evaporite rocks such as carbonates and siliciclastics). This results in a strong rheological stratification, with a range of effective viscosity up to a factor of 105. We focus here on the deformation of competent intrasalt beds in different modes of salt tectonics using a combination of conceptual, numerical and analog models, and seismic data. In bedding-paralell extension, boudinage of the strong layers forms ruptured stringers, within a 15 halite matrix, that become increasingly isolated with increasing strain. In bedding-parallel shortening, competent layers tend to maintain coherency while forming harmonic, disharmonic, and polyharmonic folds, with the rheological stratification leading to buckling and fold growth by bedding-parallel shear. In differential loading, extension and the resultant stringers dominate beneath suprasalt depocenters while folded competent beds characterize salt pillows. Finally, in tall passive diapirs, stringers generated by intrasalt extension are rotated to near vertical in tectonic melanges during upward flow of salt.