Crustal Strain in the Marmara Pull‐Apart Region Associated With the Propagation Process of the North Anatolian Fault

Publication Type:

Journal Article

Source:

Tectonics, Volume 37, Issue 5, p.1507-1523 (2018)

Abstract:

Propagation processes of plate‐scale faults through continental lithosphere are poorly documented. The North Anatolian Fault (NAF) is a continental right‐lateral transform with striking evidence for propagation processes in the Marmara Sea pull‐apart region. Earlier work (Armijo et al., 1999, https://doi.org/10.1130/0091‐7613(1999)027<0267:WPOTNA>2.3.CO;2) suggests that in the Dardanelles, where the principal, northern branch of that fault (NNAF) enters into the Aegean: (1) a fold‐thrust system has progressively developed above the NNAF fault tip, at the WSW corner of the Marmara Sea pull‐apart. The main anticline formed there was sheared and its SW half laterally offset by ~70 km to the SW; (2) the timing of structure development appears correlated with sea level changes associated with the Messinian Salinity Crisis. Our new description of the Dardanelles (or Ganos‐Gelibolu) fold‐thrust system is based on structural mapping, field observations, and calcareous nannoplankton analyses to date key sedimentary units. Our results provide tight constraints on the main pulse of folding associated with propagation of the tip of the NNAF: it took place in the late Miocene to earliest Pliocene (5.60 to 5.04 Ma), before deposition of undeformed Pliocene marine sediments. The folding is mostly coeval with the Messinian Salinity Crisis and accommodated several kilometers of shortening at the fault tip. After full propagation of the NNAF up to the surface, the folded structure was sheared and right laterally offset, with an average 14 mm/year of slip rate during the past ~5 Myrs. A reconstruction of tectonic evolution suggests a flower structure nucleating and taking root at the tip of the fault.