Hydrology in the Sea of Marmara during the last 23 ka: Implications for timing of Black Sea connections and sapropel deposition

Abstract

Sediments deposited under lacustrine and marine conditions in the Sea of Marmara hold a Late Quaternary record for water exchange between the Black Sea and the Mediterranean Sea. Here we report a multiproxy data set based on oxygen and strontium isotope results obtained from carbonate shells, major and trace elements, and specific organic biomarker measurements, as well as a micropaleontological study from a 14C‐dated sediment core retrieved from the Sea of Marmara. Pronounced changes occurred in δ18O and 87Sr/86Sr values at the fresh and marine water transition, providing additional information in relation to micropaleontological data. Organic biomarker concentrations documented the marine origin of the sapropelic layer while changes in n‐alkane concentrations clearly indicated an enhanced contribution for organic matter of terrestrial origin before and after the event. When compared with the Black Sea record, the results suggest that the Black Sea was outflowing to the Sea of Marmara from the Last Glacial Maximum until the warmer Bølling‐Allerød. The first marine incursion in the Sea of Marmara occurred at 14.7 cal ka B.P. However, salinification of the basin was gradual, indicating that Black Sea freshwaters were still contributing to the Marmara seawater budget. After the Younger Dryas (which is associated with a high input of organic matter of terrestrial origin) both basins were disconnected, resulting in a salinity increase in the Sea of Marmara. The deposition of organic‐rich sapropel that followed was mainly related to enhanced primary productivity characterized by a reorganization of the phytoplankton population.

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)

“…The highest values characterize the 1380-980 cm so-called "sapropelic" interval. This organic matter enrichment has been previously reported in the different basins of the Sea of Marmara, and in the shallower zone between the Tekirdag and Central basins (Çagatay et al, 2000;Reichel and Halbach, 2007;Vidal et al, 2010). The different ages proposed are in agreement and a 11-7.5 kyr BP period (cal 14 C without reservoir correction) has been attributed to this particular episode.…”

“…According to their radiocarbon dating, this change occurred at 13 cal kyr BP (before present). Vidal et al (2010) concluded on a slightly different scenario: beginning with the Aegean influence at 14.7 cal kyr BP, the progressive increase of the mixing, lasting 2 kyr, and followed at 12.8 cal kyr BP by an increase of terrigenous continental organic material. They relate the latter to the beginning of Younger Dryas (YD).…”

“…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).…”

“…The calcite maximum may correspond to the end of mixing process. The end of significant Black Sea input at 11.5 cal kyr BP (Vidal et al, 2010) may correspond to the end of the calcite-rich episode. Differences may be due to data sets respectively coming from a deep basin floor (Vidal et al, 2010) and from a shallower setting between two basins (Reichel and Halbach, 2007).…”

Abrupt drainage cycles of the Fennoscandian Ice Sheet

“…Additionally, to the south, the hydrology of the BS was also strongly affected by the cyclic drainage of Lake Disna. The increase in runoff due to repeated seasonal floods over four successive periods of ∼220 y raised the BS water level by around 100 m, until the sill of the Bosphorus Strait was reached (12,13,16,44,45), leading to the flooding of the vast northwestern shelf of the BS basin and the attendant drastic retreat of the coastline (SI Text). The resulting outflow of BS waters into the northeastern Mediterranean basins altered the hydrology of both the Marmara Sea (45) and the Aegean Sea (46,47).…”