Interplay between lateral extension and subsidence in large pull-apart basins resolved by 3D numerical modeling of the Dead Sea Basin

Abstract

The evolution of large and deep interplate pull-apart basins is commonly associated with crustal extension, which promotes subsidence, sediment accumulation, Moho uplift, and elevated heat flux. However, the Dead Sea Basin departs from this tectonic model with a relatively cold and thick crust and earthquake activity down to the Moho at ∼30 km depth. The Dead Sea basin is subdivided into two sub-basins, with its deepest part at the south. Supported by previous geological, geophysical, and seismological observations, we suggest that the modern tectonic geometry of the basin evolved in two general phases. The evolutionary phases are manifested in differences in the seismicity patterns, where in the north, the longitudinal faults merge at a depth (below 17 km). In contrast, in the south, the faults remain separated. To examine the contribution of the lateral extension to the basin subsidence, we apply 3-D numerical modeling, resulting in an insufficient subsidence rate (0.3 mm/year) to explain the thickness of the sediments (∼8 km). We test whether the lateral extension plus a hypothetical magmatic intrusion explains the observed anomalies in the basin structure. Our calculation suggests that the basin evolved by a combination of two phases in which the subsidence rates accelerated from 0.3 mm/year to 0.7 mm/year at ∼5 Ma. The northern part of the basin is formed by extensional tectonics, whereas a deep magmatic intrusion could have facilitated the subsidence in the southern part of the basin. We find that the relatively low lateral slip rates in the basin enabled the cooling of the intruded crust and increased its density, which in turn intensified the subsidence rate. This scenario highlights the interplay between lateral extension and subsidence in shaping the structural and seismic characteristics of large pull-apart basins and provides a plausible explanation for the unusual depth of the Dead Sea Basin.