Birth and decay of an intracontinental magmatic swell: early Cretaceous tectonics of southern Israel

The Early Cretaceous history of southern Israel is an example of the formation, growth, and decay of an intracontinental swell associated with magmatism. In this paper we document and quanitfy this process and analyze its geodynamic mechanism. The magmatism and the uplifting continued for about 10 Myr and produced a 150 to 200-km-wide dome, from whose crest nearly 1000 m of sediments were removed. Shortly after the magmatism ended, a period of cooling and subsidence began, and sediments started to cover the swell's margins. However, this subsidence was mcuh smaller than the initial uplift and did not bury the swell's crest, which remained elevated for an additional 10 Myr. The fact that most of the uplift remained indicates that the major cause for uplifting was the permanent buoyancy effect of intrusions. Transient effects such as heating at the base of the lithosphere and dynamic support of the asthenosphere may have also occurred, but their contribution to the local uplifting was minor. The distinction between temporal and permanent effects is possible because of the long-term history provided by the stratigraphic record (a full life cycle of a fossil swell). In currently active swells this distinction is much more complicated, and from this point of view this case provides unique formation. The tectonostratigraphic analysis we present illustrates how geological observations can be used to calculate tectonic uplift and to estimate accordingly the volume of magmatism that produced it. Taking into account the sea level rise during uplift and considering the topographic relief that remained after the erosion, the calculated tectonic uplift amounts to about 500 m or 40% higher than the uplift inferred only from the amount of erosion. Thermal-mechanical modeling indicates that this uplift can be explained by intrusions with a volume equivalent to a four to five-km-thick sill, consistent with other geological and geophysical observations.