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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.

Abstract.The irregular motions of plates and the irregular distribution of plate consumption and generation require that subduction zones and descending lithospheric slabs migrate laterally.Absolute plate motions indicate that slab migration is generally retrograde; that is, it is opposite to the direction of motion of the plates to which the slabs are attached, at rates of 10-25 mm yr -1 . As a result, the downward motions of slabs are generally steeper than their dips, probably because of their negative buoyancy relative to the surrounding mantle. pulls it more forcefully toward the subduction zone by increasing both the magnitude of the basal drag and the length of the overriding plate subject to a trench-directed drag. This drag on the overriding plate is the source of

A B S T R A C TNew observations from the Island of Tinos, Greece, allow a better definition of the structural position of the Alpine (Eocene) blueschist belt exposed in the islands of the Aegean Sea. These blueschists, over a significant part of the Aegean sea, are delimited from below by a lowangle thrust fault, while from above they are delimited by a low-angle, normal-type fault which omits a substantial crustal interval. Both underlying and overlying rocks were not affected by the high? metamorphism. The rapid uplift and exhumation of the high? rocks was therefore mainly the result of fault movements rather than erosion and whole-crust uplifting. The low-angle normal fault apparently had a major role in the uplift of the blueschists.TERRA Now (1989) 1, 182-187. tacts. These observations support pre-