The timing and evolution of the post-glacial transgression across the Sea of Marmara shelf south of İstanbul

Abstract

High-resolution seismic reflection profiles and analyses of the sedimentary substrate at the Sea of Marmara (SoM) entrance to the Strait of İstanbul (SoI, Bosphorus) provide a detailed record of the transgression that took place after the SoM reconnected with the Mediterranean. The sediments progressively fill a paleo shelf valley that incised the margin from the SoI to the shelf break at the time of the pre-Holocene lowstand. We map seven seismic reflection units that can be confidently correlated to sediment cores by lithology and physical properties. Sediments in the cores are dated by radiocarbon methods. Early channel and levee deposits within the paleo valley belong to the Younger Dryas cold stage and record outflow from the Black Sea via the SoI. Small clinoform packages on the valley margin formed in proximity to climbing paleo shorelines. The elevations of these deposits conform to the sealevel history recorded in Barbados corals. The younger part of the succession includes a subaqueous prodelta sourced from the Kurbağalıdere River. Its relatively young age when the Holocene sea had almost reached its modern level suggests that the thick progradational and aggradational clinoform development was primarily a response to sediment supply rather than the filling of expanding accommodation space. Our findings refute the hypothesis of Aksu et al.

Post-Glacial Terraces of the Marmara Sea and Water Exchange Periods

“…Morphological characteristics of each shelf sector are considerably different from each other, considering their structural characteristics, distance to NAF, coastal morphology, current system and features of coastal sedimentary processes. The presence of terraces and their depths were identifi ed at -85 m (Çağatay et al 2009, 2003Polonia et al, 2004;Eriş et al, 2007Eriş et al, , 2008McHugh et al, 2008), -80 m (Kuprin et al, 1974;Shimkus et al, 1980;Dimitrov, 1982;Ballard et al, 2000) and-65 m (Çağatay et al, 2009, 2003Newman, 2003;Polonia et al, 2004;Eriş et al, 2007Eriş et al, , 2008McHugh et al, 2008) in previous studies. The main reason for these differences may be due to that fact that the seismic refl ection data analysed belong to different areas of the Sea of Marmara which could have been affected by different uplift-subsidence rates.…”

“…According to an alternative outfl ow hypothesis, the Black Sea level was at -40 m (i.e., the bedrock sill depth in the Istanbul Strait), Black Sea waters were cascading down slope into the rising Marmara Sea from 10 to 9 Cal kyr BP and fi nally constructing the outfl ow delta at the southern exit of the strait Aksu et al, 2002b). However, the same delta was claimed to have been formed by sediments transported by the Kurbağalıdere River during the middle Holocene (Eriş et al, 2007).…”

“…Various scenarios have been proposed for the modes and periods of the connections e.g., Ryan et al (1997); Gökaşan et al (1997); Görür et al (2001); Aksu et al (2002a, b and c); Kaminski et al (2002); Myers et al (2003); Polonia et al (2004); Major et al (2006); Hiscott et al (2002Hiscott et al ( , 2007Hiscott et al ( and 2008 ;Meriç and Algan (2007); Eriş et al (2007 and ;Martin et al (2007); McHugh et al (2007); Çağatay et al (2000, 2003,2009, 2015). Myers et al (2003) examined the catastrophic fl ood hypothesis through the İstanbul Strait proposed by Ryan et al (2003) by means of a series of simple hydraulic calculations to investigate some of the questions associated with the Holocene reconnection of the Black Sea with the Mediterranean Sea through the Turkish Straits System.…”

Estimation of successive coseismic vertical offsets using coeval sedimentary events – application to the southwestern limit of the Sea of Marmara's Central Basin (North Anatolian Fault)

“…In particular, late Quaternary climatic cycles, and especially associated sea level changes, left a strong sedimentary imprint in shallow parts as well as in deep basins (Çagatay et al, 2000;Major et al, 2006;Vidal et al, 2010, etc.). Different hypotheses (including catastrophic flooding) have been proposed for the last "reconnection" of the three realms through the Bosphorus and Dardanelles (Çanakkale Straits) sills (Ryan et al, 1997(Ryan et al, , 1999Aksu et al, 1999, Eriş et al, 2007. For our purpose, the age of the last nonmarine to marine shift of the Sea of Marmara is a key point: (i) for the chronological frame of recent seismotectonic activity; and (ii) for the change of volume, composition, and behavior of remobilized sediments (impact of water density and circulation).…”

“…Due to its importance for the study of the last climatic cycle, the hydrologic evolution of the Sea of Marmara has been intensively surveyed by different authors through sedimentation. Biological, chemical, mineralogical, and isotopic proxies, have been analyzed to detect the respective influence of the Black Sea and the Aegean Sea since the Last Glacial Maximum (MIS 2) depending on their surface level (Çagatay et al, 2000;Major et al, 2006;Reichel and Halbach, 2007;Eriş et al, 2007;Vidal et al, 2010). The impact of these variations has also been investigated in shallow parts (Çagatay et al, 2003).…”