Oxygen-isotope geothermometers in lacustrine sediments: New insights through combined δ18O analyses of aquatic cellulose, authigenic calcite and biogenic silica in Lake Gościąż, central Poland

Palaeoclimate inferred from δ18O and palaeobotanical indicators in freshwater tufa of Lake Äntu Sinijärv, Estonia

“…-5‰ and ca. -14‰ (Hyvärinen et al 1990;Makhnach et al 2004;Jonsson et al 2010;Rozanski et al 2010) and reflects regional environment fluctuations and location (e.g. latitude).…”

Palaeo-seasonality of the last two millennia reconstructed from the oxygen isotope composition of carbonates and diatom silica from Nar Gölü, central Turkey

“…Large differences in d 18 O were also seen in the record from Lake Go scią _ z (52 35 0 N, 19 21 0 E) in Poland (Rozanski et al, 2010), again thought to be because of differences in the time of deposition of diatoms and carbonates. In contrast, a study by Lamb et al (2005) using the sediments of Lake Tilo in the Ethiopian Rift Valley (7 03 0 N, 38 05 0 E), for the period 9.0e5.7 ka, found that while d 18 O diatom was more variable (ascribed by the authors to be largely the result of tephra contamination) and did not pick up two arid events seen in the d 18 O carbonate record, the general trends were the same because diatom growth and carbonate precipitation occurred at similar times of the year.…”

“…This was possible because, as in the studies of Leng et al (2001) and Rozanski et al (2010), the climate of the study site is seasonal and the two hosts apparently record conditions in the lake at different times of the year. At Pınarbaş ı (Leng et al, 2001), d 18 O carbonate is seen as a proxy for summer temperature because of the short residence time of the lake, but Nar has a long residence time meaning that d 18 O carbonate here responds to water balance.…”

Late Holocene expansion of Siberian dwarf pine (Pinus pumila) in Kamchatka in response to increased snow cover as inferred from lacustrine oxygen-isotope records

“…Based on repeated analyses, the average δ 18 O uncertainty was ±0.4‰ for OBL and ±0.5‰ for PL. Cellulose δ 18 O was transformed into inferred lake-water δ 18 O using a constant cellulose-water fractionation factor of 1.028 (Edwards and McAndrews, 1989;Wolfe et al, 2007;Rozanski et al, 2010).…”

“…The UWEIL method commonly yields excellent δ 18 O results, even for relatively organic-poor lake sediments containing abundant lacustrine carbonate or diatom silica (e.g., Lake Gościąż - Rozanski et al, 2010) or finely comminuted glacial rock flour (e.g., Lake Agassiz - Birks et al, 2007;Teller et al, 2008;Kluane Lake -Brahney et al, 2010). This success is aided by the use of the fine fraction, which tends to minimize the influence of coarse organic detritus that is potentially of terrestrial origin (Edwards, 1993), as well as the tendency for cellulose fibres to form flocculent agglomerations during final freeze-drying that can be selectively separated from residual mineral matter when samples are weighed and loaded for analysis (Wolfe et al, 2007), thereby offsetting poor efficiency that may occur in the density separation step (as detected by Wissel et al (2008)).…”