Neotectonic Structures Indicating Extensional and Contractional Strain within Pliocene Deposits Near the NW Margin of the Niksar Pull-Apart Basin, Turkey
The Niksar basin lies between the 1939 and 1942 earthquake fault segments of the North Anatolian Fault Zone (NAFZ) and has been described as a pull-apart basin. Its structural, drainage and depositional systems generally support such a model. The extensional structures indicate normal faults, oblique-slip faults with a normal component, and geomorphological expressions such as sag ponds and are attributed to NE-SW extension related to strike-slip movements along the WNW-ESE principle displacement zone (PDZ) during the progressive evolution of the basin. The extension direction makes an angle of 50-60^0 with the orientation of the PDZ of the strike-slip fault system indicating a significant degree of transtension compared with the basement. The general trend of the transtensional structures makes an angle, ranging from 17^0 to 32^0, with the associated strike-slip faults. The value is generally compatible with the theoretical models. The indicator of contractional strain is the presence of NE-SW trending fold axes which plunge at approximately 4^0 to 8^0 towards either S or N indicating NW-SE dextral transpression. The most important result obtained in this study is that the NAFZ, at least in this particular segment, does not present pure strike-slip movement. The displacements generally have a dip-slip component, either reverse or normal, and dextral oblique-slip movement is dominant along the course of the NAFZ in this region.
TATAR, Orhan (1996) "Neotectonic Structures Indicating Extensional and Contractional Strain within Pliocene Deposits Near the NW Margin of the Niksar Pull-Apart Basin, Turkey," Turkish Journal of Earth Sciences: Vol. 5: No. 2, Article 2. Available at: https://journals.tubitak.gov.tr/earth/vol5/iss2/2