The propagation of the North Anatolian Fault in the Dardanelles Region and the Messinian Salinity Crisis: A new challenge.

Conference:

Turkish Geological Congress, 24-28 March, 2008, Ankara, Turkey.

Authors:

Rolando Armijo, Bertrand Meyer, Jean-Pierre Suc, Georges Clauzon, Mihaela Carmen Melinte-Dobrinescu, Speranta-Maria Popescu, Gülsen Ucarkus, Ziyadin Çakir, Namik M. Çağatay.

 

Abstract:

The evidence presented by Armijo et al. (1999) for the propagation of the North Anatolian fault (NAF) across the Dardanelles Region is subject of controversy (e.g. Yaltirak et al. 2000 vs. Armijo et al. 2000). Two observations appear crucial to this discussion. One is the apparent 70 km offset of the Ganos-Gelibolu anticline, not seen before, but which Armijo et al. (1999) describe as a very clear feature. The other disputed observation is the stratigraphy of the main sedimentary units and the timing of the compressional strain in the Dardanelles, constrained by the unconformity between the strongly folded strata of middle-late Miocene age (Ghazhanedere and Kirazli Formations) and the overlaying, nearly flat layers of possible early Pliocene age (Alçitepe Formation). Furthermore, Armijo et al. (1999) suggested that the transgressive Alçitepe Formation fills a canyon incised in the Dardanelles region during the Messinian Salinity Crisis. This major feature, unmapped previously, has now been investigated further. Extensive sampling of the sediments of the different units and accurate dating by nannoplankton analyses show that:

  1. The Kirazli Formation is of Messinian age (zone NN11b) and the Alçitepe Formation of Zanclean age (zone NN12), so the tectonic unconformity spans the Messinian Salinity Crisis, during which an important erosional canyon formed in the Dardanelles.
  2. The shortening in the Dardanelles area has occurred in a short time interval (possibly less than 600 000 yrs) mostly at the end of the Messinian (zone NN11b) and had completely ceased by the Zanclean (zone NN12b).
  3. Strike slip on the NAF appears the dominating tectonic process throughout the Pliocene and the Quaternary and the 70 km offset of the Ganos-Gelibolu anticline has occurred during the past ~5 Myr, in agreement with the earlier inference of Armijo et al. (1999).

The new evidence opens many exciting perspectives, including development of paleogeographical evolution scenarios and reassessment of mechanical models of fault propagation interacting with loading changes by marine waters during the Messinian Salinity Crisis.