• Shenberg, Nachum

Abstract

The Judea Group masks the deeper parts of the section, preventing their expression in the residual gravimetric anomaly. The Judea Group, which is truncated near the monocline axis near the Makhtesh HaGadol, would be expected to cause a gravity anomaly opposite to the actual one, namely high gravity over the syncline and low over the monocline axis. A monocline model is proposed, which considers the sandy Hatira formation--a monocline truncated at the axis, with a lower density than that of the surrounding Jurassic section--to be the source of the gravity anomaly. An alternative model is the 'monocline and horst model', in which there is a horst comprising pre-Jurassic formations bounded by thrust faults, below the Hatira monocline. The horst plays a secondary role in explaining a secondary positive gravity anomaly over the sloping flank of the monocline. The monoclines reflect shortening in depth by means of tilted blocks, owing to the Syrian Arc activity, while the horst is uniquely related to the Hatira structure. Similarities to other monoclines in the Negev indicate that the solution for the Hatira structure may apply to other structures also. The Syrian Arc structure was also studied for common structural characteristics, through an isostatic analysis. The inversion problem was solved using a specially written inversion program which applies an algorithm for solving a minimum problem with constraints by a non-linear optimization and direct-search method.