The isotopic composition of oxygen and carbon in the subfossil mollusc shells of the Baltic Sea as an indicator of palaeosalinity     

JAAN-MATI PUNNING  TÖNU MARTMA  HELGI KESSEL  REIN VAIKMÄE 《Boreas: An International Journal of Quaternary Research》1988,17(1):27-31

The carbon (δ¹³ C) and oxygen (δ¹⁸O) isotopic composistion in mollusc shells in mainly determined by the isotopic composition of water and dissolved bicarbonate. The δ¹⁸O values of water show a good correlation with the salinity of the Baltic. This correlation served as a basis for reconstructing palaeosalinity and for stratifying the marine sediments according to the δ¹⁸O values of the carbonate skeletons of subfossil shells. The δ¹³C values in shells are mainly determined by the isotopic composition of land-originating bicarbonate, especially in the carbonate skeleton of Lymnaea balthica , which inhabits the immediate coastal zone. According to the δ¹⁸O data, salinity in the investigated area (the coastal area of W and NW Estonia) was highest (about 9–11%) during the Littorina stage. The Limnae a stage had, in general, a salinity similar to the contemporary one, but during some phases possibly exceeding it by 2–3%.  相似文献   

CLIMATE OSCILLATIONS AS RECORDED IN SVALBARD ICE CORE ω¹⁸O RECORDS BETWEEN AD 1200 AND 1997     

ELISABETH ISAKSSON  DMITRY DIVINE  JACK KOHLER  TONU MARTMA  VEIJO POHJOLA  HIDEAKI MOTOYAMA  OKITSUGU WATANABE 《Geografiska Annaler: Series A, Physical Geography》2005,87(1):203-214

ABSTRACT. We apply two different time series analytical tools to ω¹⁸O records from two Svalbard ice cores. One ice core is from Lomonosovfonna at 1250 ma.s.l. and the other from Austfonna at 750 m a.s.l. These cores are estimated to cover at least the past 800 years and have been dated using a combination of known reference horizons and glacial modelling. Wavelet analysis reveals low frequency oscillations on the 60–120–year scale on the lower elevation site Austfonna while the higher altitude site on Lomonosovfonna does not reveal such variability throughout the record. The second method, Significant Zero Crossing of Derivates (SiZer) does not resolve the low-frequency periodicity seen in the wavelet analysis. The low-frequency variability resolved by the wavelet analysis is similar to what has been found in various climate records including instrumental temperatures and tree-rings, and has been proposed as the most important oscillation for the observed trends in Arctic air temperatures.  相似文献   

Stable isotope and pollen stratigraphy of a Holocene lake marl section from NE Finland     

HANNU HYVÅINEN  TÖNU MARTMA  JAAN-MATI PUNNING 《Boreas: An International Journal of Quaternary Research》1990,19(1):17-24

Oxygen and carbon isotope analyses are described from a marl series of Lake Vanhalampi, NE Finland, covering the time interval between about 9,000 and 4,000 to 3,000 years B.P. Both oxygen and carbon isotope ratios show consistent trends through time, apparently in response to significant environmental changes. Maximum 6^lsO levels of -12.0 on average are found in the Boreal Chronozone and minimum levels of –13.3 on average in the Subboreal Chronozone, with intermediate values during Atlantic time. A sharp decline occurs at the Atlantic/Subboreal transition between 5,000 and 4,000 years B.P. The δ15O trends are primarily believed to reflect trends in summer temperatures. The results from Lake Vanhalampi are compared with those from Lake Narotch in northwestern Belorussia.  相似文献