Open AccessAbrupt changes of temperature and water chemistry in the late Pleistocene and early Holocene Black Sea
Author(s) -
Bahr André,
Lamy Frank,
Arz Helge W.,
Major Candace,
Kwiecien Olga,
Wefer Gerold
Publication year - 2008
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2007gc001683
Subject(s) - geology , younger dryas , holocene , isotopes of oxygen , radiocarbon dating , period (music) , calcite , meteoric water , δ18o , precipitation , seawater , oceanography , stable isotope ratio , geochemistry , paleontology , physics , quantum mechanics , meteorology , acoustics , hydrothermal circulation
New Mg/Ca, Sr/Ca, and published stable oxygen isotope and 87 Sr/ 86 Sr data obtained on ostracods from gravity cores located on the northwestern Black Sea slope were used to infer changes in the Black Sea hydrology and water chemistry for the period between 30 to 8 ka B.P. (calibrated radiocarbon years). The period prior to 16.5 ka B.P. was characterized by stable conditions in all records until a distinct drop in δ 18 O values combined with a sharp increase in 87 Sr/ 86 Sr occurred between 16.5 and 14.8 ka B.P. This event is attributed to an increased runoff from the northern drainage area of the Black Sea between Heinrich Event 1 and the onset of the Bølling warm period. While the Mg/Ca and Sr/Ca records remained rather unaffected by this inflow; they show an abrupt rise with the onset of the Bølling/Allerød warm period. This rise was caused by calcite precipitation in the surface water, which led to a sudden increase of the Sr/Ca and Mg/Ca ratios of the Black Sea water. The stable oxygen isotopes also start to increase around 15 ka B.P., although in a more gradual manner, due to isotopically enriched meteoric precipitation. While Sr/Ca remains constant during the following interval of the Younger Dryas cold period, a decrease in the Mg/Ca ratio implies that the intermediate water masses of the Black Sea temporarily cooled by 1–2°C during the Younger Dryas. The 87 Sr/ 86 Sr values drop after the cessation of the water inflow at 15 ka B.P. to a lower level until the Younger Dryas, where they reach values similar to those observed during the Last Glacial Maximum. This might point to a potential outflow to the Mediterranean Sea via the Sea of Marmara during this period. The inflow of Mediterranean water started around 9.3 ka B.P., which is clearly detectable in the abruptly increasing Mg/Ca, Sr/Ca, and 87 Sr/ 86 Sr values. The accompanying increase in the δ 18 O record is less pronounced and would fit to an inflow lasting ∼100 a.