Late Cenozoic Rotatons Along the North Aegean Trough Fault Zone (Greece); Structural Constraints

Abstract

The NE-SW to E-W striking North Aegean trough fault zone takes up the righe handed strike-slip motion of the North Anatolian Fault at its western termination. Paleomagnetic measurements suggest that its southern border has undergone a clockwise rotation in the range of 26 to 48° since at most the Upper Miocene. Analysis of the Late Cenozoic extensional faulting conducted on both sides of the North Aegean trough demonstrates that in this area the tensional directions trended (1) ESE during the Upper Miocene, (2) NE during the Pliocene-Lower Pleistocene and (3) N-S during the Middle Pleistocene - Present day period. From the orientations of these tensional directions with respect to the strike of the fault zone, it appears that the right-handed strike-slip motion started at the earliest during the Uppermost Miocene and has been clearly active since the Pliocene. A statistical analysis of the tensional directions in this area suggests a differential clockwise rotation of the southern border of the fault zone with respect to its northern border, with a probable value of ~ 25, this rotation being distributed on a large area (Limnos, Lesbos). On the other hand, a statistical analysis of fold axes of Early Cenozoic age has been conducted in regions located on both sides of the western termination of the North Aegean trough close to the Greek mainland. This cannot clearly demonstrate the 48° paleomagnetic clockwise rotation of Euboea. Yet, a differential rotation of Euboea with respect to the regions located north of the Sperchios Valley is possible in the range of the uncertainties on the mean fold directions, i.e. in the range of less than 30°. Therefore, if the 48° paleomagnetic rotation is regionaly significant, then a large part of this rotation has to be related to the well-known clockwise rotation of the Ionian branch of the Aegean arc.