Tectonic evolution of fault‐bounded continental blocks: Comparison of paleomagnetic and GPS data in the Corinth and Megara basins (Greece)

Abstract

[1] We report on new paleomagnetic and anisotropy of magnetic susceptibility (AMS) data from Plio-Pleistocene sedimentary units from Corinth and Megara basins (Peloponnesus, Greece). Paleomagnetic results show that Megara basin has undergone vertical axis CW rotation since the Pliocene, while Corinth has rotated CCW during the same period of time. These results indicate that the overall deformation in central Greece has been achieved by complex interactions of mostly rigid, rotating, fault bounded crustal blocks. The comparison of paleomagnetic results and existing GPS data shows that the boundaries of the rigid blocks in central Greece have changed over time, with faulting migrating into the hanging walls, sometimes changing in orientation. The Megara basin belonged to the Beotia-Locris block in the past but has now been incorporated into the Peloponnesus block, possibly because the faulting in the Gulf of Corinth has propagated both north and east. Paleomagnetic and GPS data from Megara and Corinth basins have significant implications for the deformation style of the continental lithosphere. In areas of distributed deformation the continental lithosphere behaves instantaneously like a small number of rigid blocks with well-defined boundaries. This means that these boundaries could be detected with only few years of observations with GPS. However, on a larger time interval the block boundaries change with time as the active fault moves. Paleomagnetic studies distinguishing differential rotational domains provide a useful tool to map how block boundaries change with time.

A "Great Deepening": Chronology of rift climax, Corinth rift, Greece

“…Within the plate the largely aseismic Peloponnesus block currently moves faster than central Greece and rotates counterclockwise along the Corinth rift about a pole located in eastern Greece (Fig. 3) (Goldsworthy et al, 2002;Mattei et al, 2004). This is the fundamental cause of extension rates increasing westward in the rift.…”

Localization of Quaternary slip rates in an active rift in 105 years: An example from central Greece constrained by 234U‐230Th coral dates from uplifted paleoshorelines

“…It seems unlikely that large‐scale effects such as buoyancy forces, thermally induced changes in mantle viscosity, or variations in the geometry and location of a subducted slab could change significantly on a 10 5 year timescale. With rates of rotation about vertical axes measured by paleomagnetism and inferred from geodetic measurements in the range of about 5–10°/Ma [ Clarke et al , 1998; Mattei et al , 2004], the orientations of fault blocks rotating within a regional velocity field would likewise not change significantly in 10 5 years [see Roberts and Ganas , 2000]. It also seems unlikely that the slip rate reorganization was caused by a change in loading associated with erosion/sedimentation/influx of the sea as sea levels are known to have been in the range of zero to −120 m in elevation both before and after 175 ± 75 ka (Figure 5).…”

Rifting and shallow-dipping detachments, clues from the Corinth Rift and the Aegean

“…The localisation of the Corinth Rift near the termination of the NAF, a high rate of extension and modelling of the GPS velocity field (Flerit et al, 2004) support this interpretation. The distribution of rotations indicated by paleomagnetic studies is however not simple and recent data suggest that the southern margin of the Gulf has rotated counterclockwise since the Pliocene (Mattei et al, 2004) instead of a simple clockwise rotation expected in a dextral shearing environment.…”