Pull-apart basin formation and development in narrow transform zones with application to the Dead Sea Basin

Contrary to other examples, like Death Valley, California, and the Sea of Marmara, Turkey, the Dead Sea-type pull-apart basins form within a narrow transform corridor between strike-slip faults that are less than 10 km apart, much smaller than the crustal thickness of 35 km. In this paper we investigate the role of fault zone width versus thickness and rheology on the mechanics of pull-apart basins through a series of laboratory experiments. Results show that pull-apart basins that develop above a small step over (i.e., smaller than the thickness of the brittle layer") are narrow and elongated parallel to the overall motion. This is enhanced by increased decoupling along a basal ductile layer. The experiment with the highest degree of mechanical decoupling shows a striking resemblance to the Dead Sea Basin (DSB). Comparison with modeling results suggests that the DSB's flat basin floor is bordered over its full length by strike-slip faults that control the basin geometry and temporal and spatial basin migration. This is in strong contrast to Death Valley-type pull-apart basins that are highly oblique to the transform direction with transverse normal faults dominating over longitudinal strike-slip faults. Results imply that lithosphere rheology and the ratio of basin width to crustal thickness are controlling factors in the mechanics of pull-apart basin formation within transform corridors like the Dead Sea Fault. Copyright 2008 by the American Geophysical Union.