The world unique triangular shaped Jonah High in the Levant Basin, eastern mediterranean – Tectonic setting, stratigraphy and exploration considerations

Abstract

A clear magnetic anomaly is evident across the central part of the Southern Levant Basin, coinciding with prominent structural features known as the Jonah High and Jonah Ridge. Jonah High is a triangular shaped, horst-like structure, bounded at each of its three rims by segments of steep dips and is capped by a prominent seismic marker. An attempt to drill through the cap resulted in a loss of circulation in the Lower Miocene. The well was side-tracked to the east of the cap and penetrated a Lower Miocene and Upper Oligocene deep-water section, as found in other wells in the basin. Few models were suggested since the 1980's to explain the combined magnetic anomaly, gravity and oddly shaped structure; they include basement high, intrusive body and shallow volcanic edifice. The upper part of the high has been suggested to be a carbonate build-up of either Mesozoic or Cenozoic age or a shale structure. This study takes advantage of recently released 3D surveys acquired over the Jonah High and the results of the well. It is suggested that the Jonah High was intruded during the Lower to Middle Miocene by allochthonous bodies; these form an equilateral triangle, measuring 265 sq. km at 6.5 km depth, that might be world unique. The interior of the upper part of Jonah High, from about 5 km to 6.5 km, is suggested to be composed of a deep-water Oligocene and Lower Miocene section and probably contains the Tamar Sands, the main gas-bearing reservoir in the basin. The deep part exhibits folded and tilted high amplitude strata that may be partly composed of old magmatic material that upwelled during the Cenozoic by mobile sediment acting under the regional contractional regime; these might be associated with the observed magnetic and gravity anomalies. Further exploration by better imaging and drilling together with analogue cases from other basins are required in order to solve this enigmatic feature.