کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6428612 | 1634743 | 2015 | 10 صفحه PDF | دانلود رایگان |
- The Marmara Lake (50 to 14.7 calâkyrâBP) had a salinity of about 4â°.
- Marmara Lake freshening occurred via spill-out of fresh water from the Bosphorus.
- Spill-out through the Bosphorus was continuous for at least the 50-14.7 calâkyrâBP period.
During the last glaciation the Marmara Sea was isolated from the Mediterranean Sea because global sea level was below the depth of the Dardanelles sill. Prior to the postglacial reconnection to the Mediterranean Sea (â¼14.7 calâkyrâBP), the surface waters of the Marmara Sea were brackish (Marmara Lake). Freshening of a previously saline Marmara Sea could have happened via spill-out of brackish to fresh water from the surface water of the Black Sea through the Bosphorus Strait. This hypothesis has not been tested against alternative possibilities (salt flushing by river run-off and precipitation). Here we use the dissolved Clâ and stable isotope composition (δO18 and δD) of Marmara Sea sediment pore water to estimate the salinity and stable isotope composition of Marmara Lake bottom water and to evaluate possible freshening scenarios. We use a transport model to simulate pore water Clâ, δO18 and δD in Marmara Sea sediments in the past 130 kyr, which includes the last interglacial (130-75 calâkyrâBP), the last glacial (75-14 calâkyrâBP) and the current postglacial period. Our results show that the bottom waters of the Marmara Lake were brackish (â¼4â° salinity) and isotopically depleted (δO18â¼â10.2â° and δDâ¼â70â°, respectively) compared to modern seawater. Their salinity and stable isotope ratios show that they are a mixture of Mediterranean waters and Danube-like waters implying that the freshening took place via spill-out of freshwater through the Bosphorus. Our modelling approach indicates that the transit of fresh water from glacial Eurasia to the Mediterranean via the Marmara Sea started at least 50 calâkyrâBP, was continuous throughout most of the last glaciation and persisted up to the post glacial reconnection to the Mediterranean through the Dardanelles sill (14.7 calâkyrâBP). These results are consistent with previously published micropaleontological and geochemical investigations of sediment cores that indicate lacustrine conditions in the Marmara Sea from about 75 to 14.7 calâkyrâBP.
Journal: Earth and Planetary Science Letters - Volume 413, 1 March 2015, Pages 176-185