加拿大阿萨巴斯卡地区泥炭脂类分子记录的古气候信息

Paleo climate information recorded by peat lipid molecules in the Athabasca region, Canada

为了进一步了解泥炭中脂类分子化合物的分布与植被演化和气候变化的响应关系,对采自加拿大阿尔伯塔省东北部阿萨巴斯卡地区的JPH4、Mildred和McMurray泥炭柱样品中的脂类分子进行测定。根据正构烷烃、正烷酮、甾类和萜类等分子化合物的地球化学分析,结合年代学资料,重建了研究区近千年来的古气候演化过程。现代暖期以来(1990年以来),区内大范围的锈色泥炭藓发育,指示温暖干旱的气候条件;现代暖期早期(1900年以来),陆源高等植物和狭叶泥炭藓共存于干-湿交替的气候环境下;JPH4泥炭柱记录了小冰期期间寒冷干旱的气候环境,该时期莎草科等陆生维管植物发育;上述结论与前人记录的区域植被和气候变化具有较好的可比性。研究区发育的锈色泥炭藓种类特殊,多形成于干旱环境且具有C31正构烷烃优势分布,ACL、Paq、C23/(C27+C31)正构烷烃指标能够有效表征植被输入特征和气候变化。正烷酮主要来源于相应正构烷烃的微生物氧化作用,正烷酮指标CPI-ket、ACL-ket和(K23+K25)/(K27+K29+K31)有效地记录了泥炭沉积时期气候的演变过程。甾类、萜类化合物的丰度明显高于直链烷基类化合物,γ-内酯/生育酚、C29甾酮/C29甾醇、甾醇/甾类化合物等指标能够初步应用于指示区域气候的干湿冷暖变化,微生物的改造作用可能会影响这些指标的分布。

Lipid molecules of JPH4,MildredandMcMurray peat core samples fromthe Athabasca region ofnorthern Alberta, were systematically analyzed in order to improve the understanding of the relationship between peat lipid distribution and its response to the vegetation evolution and climate change. In accordance with the analysis results of n-alkanes, n-alkan-2-ones, steroids, terpenoids and other molecular compounds, combined with chronological data, the paleoclimatic evolution in the study area in the past millennium has been reconstructed.In the modern Recent Warming(since 1990 cal AD), Sphagnum fuscum developed widely in theAthabasca region under warm and dry climate.In the early Recent Warming,terrestrial plants and S. cuspidata species coexisted in the peatland with periods of dry-humid oscillations observed from 1900 to 1990 cal AD.As Little Ice Age period canbe dated in the JPH4 core, the climate became cold and dry after1560 cal AD when C27-dominated vascular plantsaccumulated in the JPH4 core. These conclusions are consistent with theinformation documented in local hydrological and paleoclimate data. Sphagnum fuscum,which favors dry conditions and has C31 n-alkane dominant distribution,is a special planttype of Sphagnum sect. Acutifolia, ACL,Paq,C23/(C27+C31)n-alkane proxies are optimally selected to interpretpaleoclimate alternations recorded by different types of peat-formingplants. In the representative Mildred peat core, microbial oxidation of related n-alkanes is the primary source of n-alkan-2-one. CPI-ket,ACL-ketand(K23+K25)/(K27+K29+K31) n-alkan-2-one are useful proxies to record paleoclimate variations during peat deposition.The abundance of steroids and terpenoids is significantly higher than that of linear-chain acyclic compounds, proxies of γ-lactone/tocopherols;C29 sterone/C29 sterol, sterol/steroids are preliminarilyapplied to indicate regional dry-wet and cold-warm changes in the study area, and microbial alternationmay be a factor affecting these proxies.