Possible Incision Time of the Large Valleys in Southern Marmara Region, Nw Turkey

Abstract

Surface water and sediments derived from the southern Marmara region (= Susurluk Drainage basin-SDB) transport to lakes Manyas and Ulubat first and then go to the Sea of Marmara via the Kocasu River only. The present drainage system of the SDB provides a good opportunity to study erosion rate and subsequently occurrence times of large-scale valleys in the region. To achieve it, depositional characteristics and ion contents of the ancient lacustrine sediment have been investigated and re-interpreted using cores taken from Lake Ulubat. The boron content of these sediments increased upward suddenly at 4 m depth, most probably due to starting of erosion at Emet borate beds in the drainage basin. Taking into consideration equilibrium between natural erosion and sedimentation, the incision rate in the Emet valley was found to be 1.4 cm.yr-1. From here one can calculate a time span of 75 kyr for the formation of the whole valley itself. However, it is known that working of the geological processes was not monotonous in the past; hence, this date is not absolute. Newertheless, formation of the large valleys of the southern Marmara region should not be older than 300 kyr. An important reason rapid erosion was likely lowered base-level as the Marmara Sea was a closed lake during the last Glacial Period. High altitudinal difference between source and depositional areas caused acceleration of for erosion.

Late Quaternary landscape evolution of the southern Marmara region:paleogeographic implications for settlements, NW Turkey

“…1250 m altitude, are formed of sedimentary, magmatic, and metamorphic hard rocks, which are all highly weathered (Helvacı and Orti, 1998;MTA, 2002) (Figure 2). Neogene units and older altered rocks in the highlands are highly disintegrated and less resistant to erosion, such that large valleys could develop in the basin (Helvacı, 1984;Kazancı et al, 2014). Moreover, the erodible lithology provides a large amount of sediment load to the streams, causing downstream the formation of deltas in the lakes and the Sea of Marmara (Kazancı et al, 1999(Kazancı et al, , 2004.…”

“…All rock units in the area have been uplifted by tectonics and, as a result, are deeply incised by rivers. According to Kazancı et al (2006Kazancı et al ( , 2014, the erosion rate of boron beds in the Neogene deposits and the general morphostratigraphy of the region indicate that the morphology of the SDB formed during the last 300 ka.…”

ACTIVE TECTONIC AND PALEOSEISMOLOGIC CHARACTERISTICS OF THE YENİCE-GÖNEN FAULT, NW TURKEY, IN LIGHT OF THE 18 MARCH 1953 YENİCE-GÖNEN EARTHQUAKE (Ms=7.2)

“…Data illustrating the total offset of the YGF since the Late Quaternary comes from Gönen River. According to erosion and deposition rates, Kazancı et al (2014) stated the incision times for large valleys in the Southern Marmara region did not extend beyond 300,000 years. proposed the Gönen River was cut by the YGF and offset by a total of 5,5 km.…”

“…However, the fault location stated for the YGF in this study (see fi gure 5 in is very different to the location known in the literature and adopted in this study. Considering the excavation times for large rivers in the Southern Marmara region do not extend beyond 300.000 years (Kazancı et al, 2014), for the YGF to cause a total of 5,5 km offset on the Gönen River, the annual slip rate on the fault must be 18 mm which does not comply with regional geology, and active fault and geodesy studies. In this study the total displacement amount on Gönen River west of Gönen was measured as 800±50 m (Figure 23).…”

“…West of Gönen, Gönen River is cut by the YGF and offset 800±50 m right-laterally ( Figure 23). Kazancı et al (2014) stated the excavation times for large valleys in the South Marmara Region could not go back further than 300,000 years to erosion and deposition rates. This study accepted the incision time for Gönen River Figure 22-Comparison of earthquakes identifi ed and dated in the Seyvan and Çakır trenches.…”