No abstract

Geometric analysis shows that motion of sets of strike-slip faults should cause block rotation; otherwise the distorted fault domain would not fit with its surrounding. The sense of the block rotation depends on the sense of fault slip and the spacing and orientation of the faults, all of which can be obtained from structural data. The predictions of the geometric model can then be independently tested by paleomagnetic measurements. The model was tested in northern Israel. Structural data reveal several domains of contemporaneous right-and leftlateral strike-slip faults. Paleomagnetic measurements show that in a domain of NNW trending left-lateral faults, blocks rotated 23.3o+8.2 ø clockwise, and in a domain of rightlateral faults, blocks rotated 22.4o+9.0 ø anticlockwise. These results are in agreement with the prediction of the geometric analysis of the structure. The combined results of the hetero-genous deformation of the area resembles a pure shear which allows N-S extension by about 1.3. In other domains, rotations of 34.6ø+9.1 ø and 53.1ø+11.0 ø were found. In their original orientation the left-and right-lateral faults intersected at angles of 60o-70 ø , enclosing the principal axis of shortening, in accordance with theories of brittle failure. As a result of block rotations, this angle is now larger and may reach 110 ø. The results demonstrate large block rotations, in different senses, in domains of strikeslip faults. The independent structural and paleomagnetic data can be interpreted within the framework of a simple geometric model. Northern Israel is considered to be a good model for this efficient mechanism of intraplate deformation, which is expected to occur in similar tectonic settings elsewhere. each of the faults within a domain must be related to the rotation of the blocks, and (2) the faults themselves must also rotate because they are the boundaries of the blocks (Figure 1). This idea was applied to several areas of strikeslip tectonics in eastern Iran [Freund, 1970a], 1Deceased February 1980.

Recent surface and subsurface geological investigations in Israel and Jordan provide new data for the re-examination of Dubertret’s (1932) hypothesis of the left-hand shear along the Dead Sea rift. It is found that while none of the pre-Tertiary sedimentary or igneous rock units extend right across the rift, all of them resume a reasonable palaeographical configuration once the east side of the rift is placed 105 km south of its present position. It is therefore concluded that the 105 km post-Cretaceous, left-hand shear along the Dead Sea rift is well established. The 40 to 45 km offset of Miocene rocks and smaller offsets of younger features indicate an average shear movement rate of 0.4 to 0.6 cm a -1 during the last 7 to 10 Ma. Unfortunately, the 60 km pre-Miocene movement cannot be dated yet. Along the Arava and Gulf of Aqaba and in Lebanon the shear is divided over a wide fault zone within and outside the rift.

No abstract

No abstract