Mosses form a diverse land plant group in modern vegetation but have rarely showed up in the fossil record compared with vascular plants. Here, we report an extraordinarily-preserved early Miocene moss fossil from the...Mosses form a diverse land plant group in modern vegetation but have rarely showed up in the fossil record compared with vascular plants. Here, we report an extraordinarily-preserved early Miocene moss fossil from the lower Laoliangdi Formation in the Pingzhuang Coal Mine in Chifeng, Inner Mongolia Autonomous Region, northern China. Although lacking rhizoids and most reproductive organs, the well-preserved fossil allows us to assign it to Platydictya cf. jungermannioides (Amblystegiaceae) based upon its detailed gross and micro-morphology. The diagnostic characteristics include a small-sized body with slender stems bearing spirally arranged ovate-lanceolate leaves that lack costae. Leaf margins are mostly partly entire and partly dentate, a few dentate, and rarely completely entire. It represents the first fossil record of Platydictya in Asia. The specific living microenvironment of the extant P. jungermannioides enriched our understanding of the early Miocene environment that was previously based upon vascular plant fossils and sedimentary lithofacies in the area. Our early Miocene Platydictya cf. jungermannioides fossil lived in a warm and humid lush forest with a dense understory that received adequate water supplies.展开更多
The hydrogen isotopic composition(δD) of n-alkanes in lacustrine sediments is widely used in palaeoenvironmental studies, but the heterogeneous origins and relative contributions of these lipids provide challenges fo...The hydrogen isotopic composition(δD) of n-alkanes in lacustrine sediments is widely used in palaeoenvironmental studies, but the heterogeneous origins and relative contributions of these lipids provide challenges for the interpretation of the increasing dataset as an environment and climatic proxy. We systematically investigated n-alkane δD values from 51 submerged plants(39 Potamogeton, 1 Myriophyllum, and 11 Ruppia), 13 algae(5 Chara, 3 Cladophora, and 5 Spirogyra) and 20 terrestrial plants(10 grasses and 10 shrubs) in and around 15 lakes on the Tibetan Plateau. Our results demonstrate that δD values of C_(29) nalkane are correlated significantly with the lake water δD values both for algae(R^2=0.85, p<0.01, n=9) and submerged plants(R^2=0.90, p<0.01, n=25), indicating that δD values of these algae and submerged plants reflect the δD variation of lake water. We find that apparent hydrogen isotope fractionation factors between individual n-alkanes and water(εa/w) are not constant among different algae and submerged plants, as well as in a single genus under different liminological conditions, indicating that the biosynthesis or environmental conditions(e.g. salinity) may affect their δD values. The δD values of submerged plant Ruppia in the Xiligou Lake(a closed lake) are significant enriched in D than those of terrestrial grasses around the lake(one-way ANOVA,p<0.01), but the algae Chara in the Keluke Lake(an open lake) display similar δD values with grasses around the lake(one-way ANOVA, p=0.826>0.05), suggesting that the n-alkane δD values of the algae and submerged plants record the signal of D enrichment in lake water relative to precipitation only in closed lakes in arid and semi-arid area. For each algae and submerged plant sample, we find uniformed δD values of different chain length n-alkanes, implying that, in combination with other proxies such as Paq and Average Chain Length, the offset between the δD values of different chain length n-alkanes can help determine the source of sedimentary n-alkanes as well as inferring the hydrological characteristics of an ancient lake basin(open vs closed lake).展开更多
The hydrogen isotopic composition(δD) of leaf wax long-chain n-alkanes(C27, C29, and C31) from lacustrine sediments has been widely applied to reconstruct terrestrial paleoclimatic and paleohydrological changes. Howe...The hydrogen isotopic composition(δD) of leaf wax long-chain n-alkanes(C27, C29, and C31) from lacustrine sediments has been widely applied to reconstruct terrestrial paleoclimatic and paleohydrological changes. However, few studies have addressed whether the aquatic-derived n-alkanes can affect the δD values of lake sedimentary long-chain n-alkanes, which are usually regarded as a recorder of the terrestrial hydrological signals. Here we systematically investigated δD values of long-chain n-alkanes from modern aquatic plants, both near-shore and off-shore surface sediments, surrounding terrestrial plant litters, as well as river water and lake water in Lake Qinghai and its satellite lakes on the northeastern Qinghai-Tibet Plateau. Our data showed that(i) δD values of long-chain n-alkanes from aquatic plants varied from-184‰ to-132‰ for n-C27, from-183‰ to-138‰ for n-C29, and from-189‰ to-130‰ for n-C31, respectively, with no significant differences among the three n-alkanes homologues;(ii) δD values of long-chain n-alkanes from aquatic plants were generally more positive than those from surrounding terrestrial plants, possibly because that they recorded the D-enrichment of lake water in this semi-arid region;(iii) δD values of long-chain n-alkanes from surface sediments showed significant differences among the three n-alkanes homologues, due to the larger aquatic input of n-C27 to the sedimentary lipid pool than that of n-C31, and(iv) n-C27 δD values of near-shore aquatic plants and near-shore sediments are more negative than those from off-shore as a result of lower δD values of near-shore lake water. Our findings indicate that in this region(i) the offset between sedimentary n-C27 and n-C31 δD values(ΔδDC27-C31) could potentially be used to evaluate if sedimentary long-chain n-alkanes are derived from a single source;(ii) while δD values of n-C27 may be influenced by lake water hydrological changes, sedimentary n-C31 is derived predominantly from terrestrial plants and thus its δD can serve as a relatively reliable indicator for terrestrial paleoclimatic and paleohydrological reconstructions.展开更多
基金This research was supported by the National Natural Science Foundation of China(Grant Nos.41872017 and 42072015)the Fundamental Research Funds for the Central Universities,CHD(Nos.300102272206,300102272901,300102271402,and 300102262903)+2 种基金the Foundation of State Key Laboratory of Palaeobiology and Stratigraphy(Nanjing Institute of Geology and Palaeontology,CAS)(Nos.183125 and 20172106)the Natural Science Basic Research Program in Shaanxi Province of China(No.2023-JC-YB-223)Chang᾽an University Students᾽innovation and entrepreneurship training program(No.G202210710054).
文摘Mosses form a diverse land plant group in modern vegetation but have rarely showed up in the fossil record compared with vascular plants. Here, we report an extraordinarily-preserved early Miocene moss fossil from the lower Laoliangdi Formation in the Pingzhuang Coal Mine in Chifeng, Inner Mongolia Autonomous Region, northern China. Although lacking rhizoids and most reproductive organs, the well-preserved fossil allows us to assign it to Platydictya cf. jungermannioides (Amblystegiaceae) based upon its detailed gross and micro-morphology. The diagnostic characteristics include a small-sized body with slender stems bearing spirally arranged ovate-lanceolate leaves that lack costae. Leaf margins are mostly partly entire and partly dentate, a few dentate, and rarely completely entire. It represents the first fossil record of Platydictya in Asia. The specific living microenvironment of the extant P. jungermannioides enriched our understanding of the early Miocene environment that was previously based upon vascular plant fossils and sedimentary lithofacies in the area. Our early Miocene Platydictya cf. jungermannioides fossil lived in a warm and humid lush forest with a dense understory that received adequate water supplies.
基金supported by the National Natural Science Foundation of China(Grant No.41573005)National Basic Research Programme of China(Grant No.2013CB955901)Key Program of the Chinese Academy of Sciences(Grant No.QYZDY-SSWDQC001)
文摘The hydrogen isotopic composition(δD) of n-alkanes in lacustrine sediments is widely used in palaeoenvironmental studies, but the heterogeneous origins and relative contributions of these lipids provide challenges for the interpretation of the increasing dataset as an environment and climatic proxy. We systematically investigated n-alkane δD values from 51 submerged plants(39 Potamogeton, 1 Myriophyllum, and 11 Ruppia), 13 algae(5 Chara, 3 Cladophora, and 5 Spirogyra) and 20 terrestrial plants(10 grasses and 10 shrubs) in and around 15 lakes on the Tibetan Plateau. Our results demonstrate that δD values of C_(29) nalkane are correlated significantly with the lake water δD values both for algae(R^2=0.85, p<0.01, n=9) and submerged plants(R^2=0.90, p<0.01, n=25), indicating that δD values of these algae and submerged plants reflect the δD variation of lake water. We find that apparent hydrogen isotope fractionation factors between individual n-alkanes and water(εa/w) are not constant among different algae and submerged plants, as well as in a single genus under different liminological conditions, indicating that the biosynthesis or environmental conditions(e.g. salinity) may affect their δD values. The δD values of submerged plant Ruppia in the Xiligou Lake(a closed lake) are significant enriched in D than those of terrestrial grasses around the lake(one-way ANOVA,p<0.01), but the algae Chara in the Keluke Lake(an open lake) display similar δD values with grasses around the lake(one-way ANOVA, p=0.826>0.05), suggesting that the n-alkane δD values of the algae and submerged plants record the signal of D enrichment in lake water relative to precipitation only in closed lakes in arid and semi-arid area. For each algae and submerged plant sample, we find uniformed δD values of different chain length n-alkanes, implying that, in combination with other proxies such as Paq and Average Chain Length, the offset between the δD values of different chain length n-alkanes can help determine the source of sedimentary n-alkanes as well as inferring the hydrological characteristics of an ancient lake basin(open vs closed lake).
基金supported by the National Natural Science Foundation of China (Grant No. 41573005)the National Basic Research Program of China (Grant No. 2013CB955901)
文摘The hydrogen isotopic composition(δD) of leaf wax long-chain n-alkanes(C27, C29, and C31) from lacustrine sediments has been widely applied to reconstruct terrestrial paleoclimatic and paleohydrological changes. However, few studies have addressed whether the aquatic-derived n-alkanes can affect the δD values of lake sedimentary long-chain n-alkanes, which are usually regarded as a recorder of the terrestrial hydrological signals. Here we systematically investigated δD values of long-chain n-alkanes from modern aquatic plants, both near-shore and off-shore surface sediments, surrounding terrestrial plant litters, as well as river water and lake water in Lake Qinghai and its satellite lakes on the northeastern Qinghai-Tibet Plateau. Our data showed that(i) δD values of long-chain n-alkanes from aquatic plants varied from-184‰ to-132‰ for n-C27, from-183‰ to-138‰ for n-C29, and from-189‰ to-130‰ for n-C31, respectively, with no significant differences among the three n-alkanes homologues;(ii) δD values of long-chain n-alkanes from aquatic plants were generally more positive than those from surrounding terrestrial plants, possibly because that they recorded the D-enrichment of lake water in this semi-arid region;(iii) δD values of long-chain n-alkanes from surface sediments showed significant differences among the three n-alkanes homologues, due to the larger aquatic input of n-C27 to the sedimentary lipid pool than that of n-C31, and(iv) n-C27 δD values of near-shore aquatic plants and near-shore sediments are more negative than those from off-shore as a result of lower δD values of near-shore lake water. Our findings indicate that in this region(i) the offset between sedimentary n-C27 and n-C31 δD values(ΔδDC27-C31) could potentially be used to evaluate if sedimentary long-chain n-alkanes are derived from a single source;(ii) while δD values of n-C27 may be influenced by lake water hydrological changes, sedimentary n-C31 is derived predominantly from terrestrial plants and thus its δD can serve as a relatively reliable indicator for terrestrial paleoclimatic and paleohydrological reconstructions.
