Presentation on theme: "RAPID ENVIRONMENTAL CHANGES IN THE BLACK SEA OVER THE LAST 3 KYRS M. Namık Çağatay 1 and Emin Güngör 2 1 İstanbul Technical University, Geology Department,"— Presentation transcript:
RAPID ENVIRONMENTAL CHANGES IN THE BLACK SEA OVER THE LAST 3 KYRS M. Namık Çağatay 1 and Emin Güngör 2 1 İstanbul Technical University, Geology Department, Ayazağa 80626 İstanbul 2 Çekmece Nuclear Research and Training Centre, K. Çekmece İstanbul Main topics 1)Change in phytoplankton population at ~2700 yrs BP 2)Climate cooling at ~ 1700 AD 3)Increase in mass accumulation and land erosion rates in last few hundred years 4)Increased eutrophication and metal pollution in the last 50 yrs
Large, enclosed unoxic basin, covering 432,000 km2; max.depth: 2250 m. Anoxia below 100-150 m for the last 7-8 kyrs due to sharp density stratification, weak vertical circulation and organic matter degradation. Severe environmental degradation in the last 50 yrs, mainly because of riverine input of contaminants and nutrients.
Four undisturbed cores recovered by a multi-corer during 1998 and 2000 IAEA cruises Total organic carbon (TOC) analysis by CHN elemental analysis Total carbonate analysis by gasometric-volumetric method Metals analysis by ICP-MS after a total digestion 210 Pb dating by alpha counting of 210 Po, followed by using a constant 210 Pb flux (F Pb-210 in Bq cm -2 yr -1 ) - constant MAR (g cm -2 yr -1 ) model A compaction correction applied for 210 Pb age modelling Methodology
Stratigrafic level Cal. Age (yr) MethodSource Base Sapropel Unit (Unit II/III boundary) 7090 ± 180 6600 7540 ±130 7800 5083 14 C Varve counting Ross ve Degens, 1974 Calvert, 1987 Jones ve Gagnon, 1994 Arthur ve Dean, 1997 Degens ve diğ., 1980 First Coccolith band 3450 ± 120 2720 ±160 2000 1633 14 C Varve counting Ross & Degens, 1974 Jones &Gagnon, 1994 Arthur ve Dean, 1997 Hay et al., 1991 Last coccolith invasion and base of Coccolith unit (Unit I) 3200 ± 140 1635 ±60 998 1256 14 C Varve counting Ross & Degens, 1974 Jones & Gagnon, 1994 Degens et al., 1980 Hay et al., 1991 Chronostratigraphy Çağatay & Güngör 2700 yrs BP 7540 yrs BP
West Black Sea BasinEast Black Sea Basin According to 210 Pb chronology, the carbonate peak corresponds to ~1700 AD and the blue shaded area to a time interval of 100 yrs Late Maunder Minimum (1645-1715; Eddy, 1978; Pfister, 1994; Lutherbacher et al., 2001)
Oxygen and carbon isotope distributions Carbonate Temperature decrease during LMM (?)
Core MAR (g m -2 yr -1 ) LSR (cm yr -1 ) BS98-9171.5 0.72 BS98-1571.250.34 BS2K-9155.70.45 BS2K-2387.310.26 Mass accumulation and Linear sedimentation rates for the last 125 yrs The average total MAR values for the last 125 yr are 2 to 4 times higher than those for the last 2700 years, computed from published 14 C ages, suggesting that the sedimentation rate has considerably increased in recent times, due to human impact.
Eutrophication and Metal Pollution Core BS-15 ElementEnrich.factor over backgr. Ba5.5 Zn5 Pb9 Cu2
Core BS-9 ElementEnrich.factor over backgr. Ba5 Zn3.6 Pb2 Cu2.4
Conclusions Core evidence shows four important rapid environmental changes in Black Sea: 1)Coccolitophore invasion at about 2700 yrs as result of salinity increase to 11 ppt. This event increased the CaCO 3 burial by at least 3 times over the previous period. 2) Cold climate: Late Maunder Minimum during 1645-1715 AD. 3) Increase in sedimentation and land erosion rates in the last few centuries. 4) Increase in eutrophication and metal pollutin in the last 50 yrs. 5) This study is onother demonstration of the usefulness of core studies in obtaining long records of environmental changes in marine basins. This is important for modelling and future predictions.