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Epicontinental basins are extremely prone to major paleogeographic changes, and this will directly affect any organic matter (OM) preserved in the depositional record. In this study the Middle–Late Miocene successions in the northern Pannonian Basin System were investigated via sedimentological, petrographic, and geochemical analyses of cores from the Danube Basin to reveal the interplay of factors driving the character of the OM. In the late Middle Miocene (~12.3 Ma), the Central Paratethys Sea maintained normal marine salinity, with dysoxic bottom waters in a distal basin floor environment rich in aquatic OM. The last rifting phase followed during the Late Miocene and led to formation of the deep Lake Pannon. Like seawater, the brackish lake water still also contained sulfate. These open lacustrine deposits (~11.6–10.0 Ma) reveal OM sourced from submerged/floating macrophytes and algae, and humid conditions are indicated by the preponderance of deciduous trees and shrubs on shores. The study identifies hybrid event beds (HEBs) on Lake Pannon's floor (~10.0–9.3 Ma), with currents redepositing mud and OM, resulting in similarities between the Middle Miocene and Late Miocene successions. Turbidite deposition (~9.3–9.0 Ma) from the paleo-Danube induced a shift in OM, replacing algae with terrestrial input. Complete isolation from the main water masses of Lake Pannon (~9.0–8.9 Ma) altered its sources of OM, transitioning from algae to macrophytes, and caused a drop in salinity, likely associated with a humidity peak. The subsequent deltaic dominance (~8.9–8.6 Ma) features well-developed topset lakes, swamps, and floodplain forests, reflecting warm temperate to subtropical climates. The Middle–Upper Miocene deposits studied here are source rocks with fair to very good richness and poor to fair generative potential, and contain kerogen types III and IV, while type II is rare. The rapid paleoenvironmental changes observed over the order of ~100 kyr caused the complete switching of OM type and delivery, giving an indication of the complexity of epicontinental basins. • Multi-proxy approach tracing organic matter (OM) delivery in Pannonian Basin • Sarmatian sea (~12.3 Ma): normal marine salinity, dysoxic waters rich in aquatic OM • Lake Pannon HEBs (~10.0–9.3 Ma) share Middle Miocene strata traits due to redeposition. • Turbidite deposition (~9.3–9.0 Ma) from paleo-Danube shifts OM composition. • Deltaic topset beds (~8.9–8.6 Ma) bear aquatic OM with coal layers under warm climate. [ABSTRACT FROM AUTHOR]

The examined peatlands were assayed for the n-alkanes С14Н44–С31Н64; their contents of in all studied soil profiles are determined by both different botanical compositions of plant residues in peatlands and different climatic conditions (temperature and humidity) during these alkanes formation. The maximum total content of n-alkanes dates back to the Holocene climatic optimum and amounts to 104–191 μg/g for the studied peatlands of the extreme northern taiga. The composition of n-alkanes (the homologs with an odd number of carbon atoms C21H44, C23H48, C25H52, C27H56, C29H60, and C31H64) and their ratios are shown to reflect the specific features of the changes in plant communities composing the peat layers and the climatic conditions of peat soils genesis. The data on n-alkanes in combination with radiocarbon and paleobotanical data are useful in identification of the initial vegetation during the peat formation in the Holocene phases and more accurate reconstruction of the peatland genesis. [ABSTRACT FROM AUTHOR]

Since the Cenozoic, the earth entered a period of relatively active tectonic movement, which led to significant environmental and climatic shifts, including inland drought in Asia, global cooling, and the formation of the Asian monsoon. The Asian aridification has a far-reaching impact on the human living environment, and so do the climate changes in China. The beginning, strengthening, and ending times of the inland drought in Asia have been a long-concerned issue. Therefore, it is necessary to reveal the starting time, evolution process, and underlying driving mechanisms. Because of its unique topography and geographical location, the Qinghai–Tibet Plateau is known as the “starter” and “amplifier” of global climate change. It is a key area and an ideal “laboratory” for long-time scale climate change. Located in the central-eastern part of the Qinghai–Tibet Plateau, the Nangqian Basin is not only the confluence area of major monsoons and westerly winds but also the boundary between humid and arid areas. Moreover, the Nangqian section in the basin has a long continuous sedimentary sequence, making it a good carrier for long-time scale climate change research. In this study, biomarkers and total organic carbon (TOC) in the sedimentary strata of the Nangqian Basin in the central-eastern Qinghai–Tibet Plateau were used to reconstruct the paleoclimate and paleovegetation evolution history over the time interval of 51.8–37.5 Ma. According to the climatic index of the Nangqian Basin, the climate evolution history can be divided into three stages. StageⅠ: during 51.8–46.4 Ma, the depositional environments at this stage were mainly a braided river and an ephemeral shallow pond/lake environment. Also, the value of CPI, δ13Cn-alkanes, and total organic carbon (TOC) was low; meanwhile, ACL value increased with nC27/nC31 decrease, and these obvious change trends might be affected by the mixing of terrestrial sediments brought by rivers. The main peak carbons were nC22 and nC23, the vegetation type was predominantly woody plants, and the climate was relatively humid. Stage Ⅱ: during 46.4–42.7 Ma, Paq and nC27/nC31 values decreased gradually, and ACL, δ13Cn-alkanes, and CPI values increased slowly. Also, the main peak carbon number changed from low to high, and the vegetation type varied from woody to herbaceous. All these proxies displayed that the climate became more arid. Stage Ⅲ: during 42.7–37.5 Ma, Paq, ACL, and nC27/nC31 values did not vary too much, δ13Cn-alkanes values increased slightly, and ACL values decreased slightly, while the main peak carbon number, TOC, and CPI increased significantly, indicating that the climatic conditions continued to get dryer, which may have been affected by the MECO events. In addition, through the comparative study of the climate evolution history of the Eocene in the Nangqian Basin reconstructed by the multi-index system, together with the climate change in the adjacent area, the retreat process of the Paratethys Sea, the global deep-sea oxygen isotopes, and the global atmospheric CO2 concentration, it is considered that the Eocene climate change in the Nangqian Basin is mainly affected by the global climate change and the retreat of the Paratethys Sea. The uplift of the Qinghai–Tibet Plateau and the increase of altitude have little influence on the water vapor of the Nangqian Basin, and the basin was rarely affected by the South Asian monsoon.

Despite the fact that the vegetation pattern and history of the Bale Mountains in Ethiopia were reconstructed using pollen, little is known about the former extent of Erica species. The main objective of the present study is to identify unambiguous chemical proxies from plant-derived phenolic compounds to characterize Erica and other keystone species. Mild alkaline CuO oxidation has been used to extract sixteen phenolic compounds. After removal of undesired impurities, individual phenols were separated by gas chromatography and were detected by mass spectrometry. While conventional phenol ratios such as syringyl vs. vanillyl and cinnamyl vs. vanillyl and hierarchical cluster analysis of phenols failed for unambiguous Erica identification, the relative abundance of coumaryl phenols (>0.20) and benzoic acids (0.05—0.12) can be used as a proxy to distinguish Erica from other plant species. Moreover, a Random Forest decision tree based on syringyl phenols, benzoic acids (>0.06), coumaryl phenols (0.3) could be established for unambiguous Erica identification. In conclusion, serious caution should be given before interpreting this calibration study in paleovegetation reconstruction in respect of degradation and underground inputs of soil organic matter.

Amber of different color and fluorescence has recently been found in a lignite seam in the Zerkal'nenskaya depression, Primorsky Krai, Russia. In this deposit, the amber is associated with abundant charcoal and fusain fragments in the host rocks. Beside three composite samples of different color from the lignite and one composite amber sample from the Sakhalin Island has been included in this study for comparison. Based on previous fluorescence and fluorescence excitation measurements, the blue glow of amber has been related to the fluorescent aromatic hydrocarbon perylene, although FTIR study of the Russian blue amber has not found any distinct signature of this compound. The present analyses using gas chromatography–mass spectrometry have also identified no perylene in any of the four Russian amber samples. The hydrocarbon fractions of the extractable organic matter from the ambers are dominated by C 18 to C 20 diterpenoids of the labdane, abietane, pimarane, phyllocladane and kaurane types. Their biomarker composition is consistent with the proposed origin from gymnosperms of the families Pinaceae, Cupressaceae, and/or Taxodiacceae. The cause for the blue amber glow could not be clarified based on the commonly used methods of hydrocarbon composition study. [ABSTRACT FROM AUTHOR]

In Dombayova graben (Dinar-Afyonkarahisar, western Turkey) a 203-m-thick coal-bearing zone of Late Miocene to Pliocene age was recently drilled. The zone hosts several coal beds with a total thickness of 46 m. Coal samples from the Dombayova field were studied by means of standard proximate, ultimate, petrological analyses, micro-FTIR spectroscopy and Rock-Eval pyrolysis, and organic geochemical analyses. Coal proximate analyses and the presence of carbonate minerals and fossil shell fragments point to alkaline surface waters of changing pH-values due to fluctuations of the water level in the paleomire and/or Ca-rich water influx. Low sulfur contents argue for sulfate-limitation of bacterial sulfate reduction. Petrographic observations reveal that the coal is dominantly composed of weakly altered wood fragments and roots. The mean random reflectance values of ulminite (0.33 %Ro) indicate lignite rank of the coal. The micro-FTIR data of macerals of huminite group indicate higher contributions of aliphatic hydrogen in textinite, compared to more aromatic levigelinite. The semi-quantitative differences in the ratios of selected functional groups suggest that aromaticity and the extent of oxidation are higher in levigelinite. Aliphatic chains are longest in textinite and ulminite, and shortest in texto-ulminite and levigelinite. We interpret this difference to point to a different origin of levigelinite, probably from colloidal humic solutions that were gelified during diagenesis. The concentrations of n -alkanes and their distribution patterns provide evidence for higher terrestrial plants as the dominant source of organic matter. Decreasing pristane/phytane ratios with depth are interpreted to reflect more reducing conditions during peat formation due to higher (ground)water level. The absence of diasterenes is most probably caused by low clay mineral contents and is consistent with the presence of alkaline waters in the paleomire. The presence of terpenoid hydrocarbons in the lignite indicates a major contribution of angiosperms to peat formation. The positive relationship between the concentrations of perylene and lupane-type triterpenoids suggests an increasing abundances of wood-degrading fungi in the peat-forming vegetation characterized by a high density of Betulaceae. [ABSTRACT FROM AUTHOR]

Carbon isotope of total organic carbon (δ 13 C org ) and long-chain n -alkanes, which are terrestrial plant biomarkers, and their compound-specific carbon isotope ratios (δ 13 C ALK ) were investigated in the sediment of the Jeongok-ri Paleolithic Site in central Korea to interpret changes in paleovegetation and paleoclimate. The δ 13 C org ranged between approximately −24‰ and −27‰, suggesting different organic matter sources. Relatively lighter δ 13 C org occurred in lower part and the occurrence of heavier δ 13 C org in upper part may indicate terrestrial C 3 plant dominance and/or a mixture of C 3 and C 4 plants, respectively. The patterns of n -alkane distribution were characterized by a continuous predominance of odd-numbered n -alkanes, particularly n C 29 and n C 31 , and by variation in the distribution of even-numbered n -alkanes. Total concentration of n -alkanes and distributions of each number of n -alkanes are quite different over time, suggesting paleovegetation changes. The average chain length (ACL) and carbon preferences index (CPI) showed gradual variations with distinctive switching points at about 160 ka. This variation reflecting changes in paleovegetation type, is coincident with those of the δ 13 C org . Individual n -alkane isotopes, δ 13 C ALK , ranged between −18.64‰ and −38.09‰, suggesting different sources of n -alkanes. Although some petrogenic sources of n -alkanes were possible, the distribution of n -alkanes and their δ 13 C ALK support paleovegetation and paleoclimatic variations in Jeongok-ri Paleolithic site, Korea for the last 300 ka. [ABSTRACT FROM AUTHOR]

The reconstruction of paleovegetation from terrestrial sediments such as loess and paleosols represents a major, but still challenging task in Quaternary research. A significant methodological advance was the implementation of biomarker applications to terrestrial archives such as loess sequences and fossil soils. Essentially, the n-alkane approach has been widely applied within the last years to reconstruct changes in the paleoenvironment as for example regarding the relative abundance of woody species versus grasses from Quaternary terrestrial deposits. However, complex distribution patterns of leaf wax lipid homologues in plants and often little taxonomic specifity limit the use of n-alkyl series in paleoflora research. In this study, retene is introduced as a new molecular marker specifically for conifer derived organic matter to Quaternary loess – paleosol research. The ratio of retene to cadalene serves as a useful proxy for the relative contribution of conifers to the paleovegetation. Up to now these molecular markers have been mainly applied to coal research and marine sediments. Using samples from the Tumara site (Siberia), the added value of this new molecular approach for paleovegetation reconstruction also for loess and Quaternary fossil soils is demonstrated. The results of this pilot study confirm the presence of conifers during the penultimate glacial in NE-Siberia. [ABSTRACT FROM AUTHOR]

Tricyclic diterpenoids and non-steroid or non-hopanoid pentacyclic triterpenoids are almost exclusively taxon-specific terrestrial plant biomarkers produced by conifers and angiosperms, respectively. Due to this source specificity and their prevalence in the geologic record, these compounds are often used to reconstruct paleovegetation. However, the physical and chemical processes that influence the dispersal and fate of terpenoids in sedimentary archives are poorly constrained. Modern fluvial systems can be used as ancient river analogs to provide information on the utility of terrestrial plant terpenoids as paleovegetation proxies by defining their potential flux and identifying the processes that control their transport to, and deposition and degradation in, sediments. To determine if the contribution of terpenoids from vegetation is reflected in forested soil and river sediments and to constrain the dispersal of these compounds in fluvial systems, di- and triterpenoid concentrations in Miners River drainage basin (Upper Peninsula of Michigan, USA) were quantified. In the basin, evergreen conifers are less abundant than deciduous angiosperms, but yet contribute substantially more terpenoids to soils and river sediments when scaled for leaf litter production and present vegetation cover. The composition and relative concentration of di- and triterpenoids in source vegetation do not match those in soils and river sediments, suggesting that some process or processes result in the preferential removal of diterpenoids. While the soil and river sediment terpenoid concentration, corrected for differential terpenoid inputs, can closely predict the basin wide vegetation cover in Miners River drainage basin, the extent to which terpenoids can be used a paleovegetation proxy in other modern or geologic sediments remains unclear. [ABSTRACT FROM AUTHOR]

Abstract: Lignin has been analysed as a proxy for vegetation change in the Quaternary science literature since the early 1990s in archives such as peat, lakes, and intertidal and marine sediment cores. Historically, it has been regarded as comparatively resistant to various types of degradation in comparison to other plant components. However, studies of modern biogeochemical processes affecting organic carbon have demonstrated significant degradation and alteration of lignin as it is transported through the terrestrial biosphere, including phase changes from particulate to dissolved organic matter, mineral binding and decay due to biotic and abiotic processes. The literature of such topics is vast, however it is not particularly useful to Quaternary research without a comprehensive review to link our understanding of modern processes involving lignin to Quaternary environments. This review will outline the current state of the art in lignin phenol research that is relevant to the Quaternary scientist, and highlight the potential future applications for this important biomarker for vegetation change and terrestrial organic carbon cycling. [Copyright &y& Elsevier]

Sea surface temperature (SST) changes in the SW Indian and SE South Atlantic Ocean are proposed to have controlled environmental changes at the southern tip of the African continent during the past. For a better understanding of the hydrological variations and their environmental impact during the past 84kabeforepresent (BP), we analyzed lipid biomarkers and their stable carbon (δ13C) and hydrogen (δD) isotopic compositions in sediments from Lake Tswaing (25°24′30″ S, 28°04′59″ E). δD values of long-chain n-alkanes from higher plants varied between −155 and −82‰ and matched well with SST gradient changes between the tropical and subtropical SW Indian Ocean. Increased SSTs correlate with deuterium-depleted δD values of n-alkanes and indicate a higher convection transporting more moisture across South Africa in the time from 84 to 80kaBP, during the marine isotope stage (MIS) 4 and from 50 to 39kaBP. During these humid periods high amounts of organic matter (up to 9.8% total organic carbon (TOC)) were deposited in Lake Tswaing. Periods with deuterium-enriched δD values of n-alkanes (76kaBP, 73 to 69kaBP, 55 to 51kaBP, and 31.4 to 12.6kaBP), indicating dry climate and increased lake water salinity, were associated with lower TOC contents and a higher degradation state of the terrestrial organic matter. We occasionally detected algae-derived C37- and C38-alkenones in the core, particularly in times when lake salinity and alkalinity were elevated. The disappearance of alkenones around 25kaBP was accompanied by highly depleted δD values of n-alkanes from aquatic organisms (−180‰ for n-C23) indicating a substantial freshening of the lake water. The vegetation surrounding Lake Tswaing during the last 84kaBP consisted mainly of savanna-type plants, such as trees and shrubs with varying contributions from C4 grasses. The latter predominated particularly at the end of MIS 5 and during arid climatic conditions in MIS 3. We show that the changing vegetation controls the n-alcohol to n-alkane ratio of the leaf waxes; this is reflected by the higher plant alkane (HPA) index which has potential as a new climate-controlled vegetation proxy; in semi-arid periods HPA index values were elevated reflecting savanna vegetation which is adapted to drier climate, whereas HPA index values were lower during more humid conditions. [ABSTRACT FROM AUTHOR]

The role of savannas during the course of early human evolution has been debated for nearly a century, in part because of difficulties in characterizing local ecosystems from fossil and sediment records. Here, we present high-resolution lipid biomarker and isotopic signatures for organic matter preserved in lake sediments at Olduvai Gorge during a key juncture in human evolution about 2.0 Ma-the emergence and dispersal of Homo erectus (sensu lato). Using published data for modern plants and soils, we construct a framework for ecological interpretations of stable carbon-isotope compositions (expressed as δ13C values) of lipid biomarkers from ancient plants. Within this framework, δ13C values for sedimentary leaf lipids and total organic carbon from Olduvai Gorge indicate recurrent ecosystem variations, where open C4 grasslands abruptly transitioned to closed C3 forests within several hundreds to thousands of years. Carbon-isotopic signatures correlate most strongly with Earth's orbital geometry (precession), and tropical sea-surface temperatures are significant secondary predictors in partial regression analyses. The scale and pace of repeated ecosystem variations at Olduvai Gorge contrast with long-held views of directional or stepwise aridification and grassland expansion in eastern Africa during the early Pleistocene and provide a local perspective on environmental hypotheses of human evolution. [ABSTRACT FROM AUTHOR]

Previous studies have found that wetlands prevailed in western Chinese Loess Plateau and pine pollen could reach up to 80% in Qin'an area of the plateau during middle Holocene. It was then deduced that forest vegetation covered Qin'an area in a warm and wet climate during middle Holocene. The proxies of molecule biomarkers from two Holocene sections, a swamp-alluvial loess section and a typical loess-paleosol section are used to reconstruct regional vegetation history. It is found that the heavy-molecular-weight (HMW) homobogues of the n-alkanes in all samples exhibit a pronounced odd-over-even predominance, maximizing at C31 and the abundance of the nC27-alkanes is the lowest in nC27, nC29, nC31, i.e. C27

Paleoenvironmental and paleoclimatic variations experienced by the Mediterranean region during the Miocene Burdigalian-Langhian interval have been investigated through analysis of biomarker signals (n -alkanes and glycerol dialkyl glycerol tetraethers, GDGTs) from slope mudstones of the northern Apennines (Marne di Vicchio Fm). Terrestrial signatures in marine sediments reflected by preserved long-chain n -alkanes with a identifiable odd-over-even carbon number predominance attest to the thermal immaturity of the sedimentary rock. Abundances of n -C 27 , n -C 29 and n -C 31 alkanes, coupled with the carbon isotopic signatures of the n -C 31 homologue suggest that Mediterranean vegetation crossed a transition phase adapting to arid conditions that may favored a shift from woodland to wooded grassland during the Middle Miocene. This ecosystem evolution could have been favored by the passage from warm humid conditions to a warm drier climate, as indicated by GDGT-based TEX 86 and BIT indexes. Strong similarities between these Mediterranean biomarker records and those from the Atlantic (DSDP Sites 94, 516, 608) imply a constant connection of the western Mediterranean to the Atlantic Ocean from ~19 Ma to ~14.5 Ma. • Mediterranean vegetation transition from woodland to grassland during Middle Miocene. • New hydrocarbon biomarker study for the Middle Miocene Mediterranean area. • Ecosystem evolution favored by the passage from warm humid to drier climate condition. • Similar biomarker values between Mediterranean and north Atlantic (IODP SITE 608). • Steady connection of western Mediterranean to Atlantic Ocean from19 Ma to 14.5 Ma. [ABSTRACT FROM AUTHOR]

• Xylites are affected by weak gelification and advanced cellulose decomposition. • δ13C of xylites reflect the extent of cellulose decomposition. • Xylites represent wood remains of the same species of conifers in the lignite. • Fluctuating δ13C and δ2H of lipids within the seam are caused by water availability. Single pieces of fossil wood fragments (xylites) were collected from the middle Miocene First Lusatian lignite seam at the Adamów, Jóźwin IIB and Tomisławice opencast mines and are characterized by maceral variety, cellulose contents and their molecular and isotopic composition. Biomarker composition of xylites and δ13C of their total organic matter, lipids and cellulose are used to provide insights into woody plant community and the effects of wood decomposition. The investigated xylites represent fragments of fossil wood from conifers, most likely species of Cupressaceae, indicated by terpenoid biomarkers characteristic for conifers and by the δ13C values of the extracted cellulose. This conclusion is confirmed by paleobotanical data highlighting Taxodium and Nyssa as the main elements of the wet forest swamps. Due to the wet swamp habitat and the higher-decay resistance exclusively wood fragments of conifers are found in the lignite seam. Minor abundances of angiosperm-derived triterpenoids in the xylites are explained by impurities from inherent detritic lignite. The xylites are characterized by minor to moderate extents of gelification, but elevated to high cellulose decomposition. The relationship between δ13C values of xylites and their cellulose contents reflects wood decomposition removing preferentially the 13C-enriched compounds, but decomposition did not affect the δ13C of cellulose. Despite of similar δ13C of xylites and detritic lignite, differences in isotopic composition of hopanoids argue for slightly different microbial communities involved in the decomposition of the respective OM. Thus, we conclude that wood decomposition proceeded in a freshwater environment under acidic conditions by fungi and bacteria. Variations in water availability during growth periods of the conifers are suggested as the most probable cause for the observed minor variations in isotopic composition of plant lipids. The positive relationship found between δ2H and δ13C of plant biomarkers, and cellulose of xylites can be explained by the ability of vascular plants to minimize evapotranspiration during dryer phases resulting in plant OM enriched in 13C and 2H. The significant differences in δ2H between diterpenoids of different structural types and n -alkanes are most likely caused by differences in isotopic fractionation during lipid biosynthesis. [ABSTRACT FROM AUTHOR]

• A mixed vegetation during peat-formation is indicated by lipid composition. • Terpenoids characteristic for Taxodiaceae, Pinaceae and Betulaceae are present. • The biomarker compositions are in good agreement with palaeobotanical data. • δ13C values of coal are governed by changing gymnosperm/angiosperm ratios. • Changes in δ13C of atmospheric CO 2 are reflected in compound-specific isotope ratios. Samples of detrital lignite have been collected for detailed organic geochemical and carbon isotope analyses from the First Lusatian lignite seam at the Adamów, Jóźwin IIB and Tomisławice opencast mines, deposited after the last peak of the Mid-Miocene Climatic Optimum. Carbon isotopic compositions of biomarkers from Polish lignite are reported for the first time. The aim of the study is to improve the chemotaxonomic value of biomarkers by relating the results to existing paleobotanical data, and to gain information about the influencing factors on δ13C of lignite and lipids. Furthermore, biomarker and isotopic proxies are tested for their applicability in paleoclimate studies. The molecular composition of the extracted lipids is highly variable, including leaf-wax n -alkanes in the C 23 to C 31 range, diterpenoids, hopanoids, and angiosperm-derived triterpenoids, as well as saturated fatty acids, long-chain n -alkanols and n -alkan-2-ones. The relative abundances of mid-chain (C 23 , C 25) n -alkanes and their 1–2‰ higher δ13C values compared to long-chain n -alkanes (C 29 , C 31) argue for a minor contribution of macrophytes (graminoids, etc.) to peat formation, enhanced during periods of raised water level. The presence of ferruginol and dehydroferruginol testifies the contribution of Taxodiaceae. The abundances of pimarane-type diterpenoids and the presence of non-aromatic abietane-derivatives argue for the contribution of Pinaceae. Based on the presence of lupeol and lupane-type triterpenoids, an input of Betulaceae can be concluded. The contribution of further angiosperms cannot be specified based on the composition of pentacyclic triterpenoids. However, the results indicate mixed vegetation, and are in agreement with paleobotanical data highlighting abundant conifers of the Taxodiaceae/Cupressaceae and Pinaceae families, as well as angiosperms of various families (e.g., Nyssa, Quercus, Fagus), including Betulaceae (e.g., Alnus, Betula, Corylus). Based on the relationship between the carbon preference index of n -alkanes and mean annual air temperatures, obtained from a global database of peatlands, an average temperature of 24.5 °C is obtained. This value is significantly higher as estimated from paleobotanical data (15.7–19.7 °C), probably due to the influence of changes in vegetation on carbon preference index. The relative abundances of diterpenoids versus di- plus angiosperm-derived triterpenoids in detrital lignite samples revealed variable contributions of gymnosperms and angiosperms during the middle Miocene. Consistent with these results, a positive relationship exists between the di-/(di- + tri-) terpenoid biomarker ratios and δ13C of lignite samples, indicating the dominating role of varying gymnosperm/angiosperm contributions on the carbon isotopic composition of lignite. The C-isotope data of long-chain n -alkanes, diterpenoids, and angiosperm-derived triterpenoids co-vary within the profiles, arguing for an overall control of changes in δ13C of atmospheric CO 2 on δ13C of plant lipids. Fluctuations in δ13C of individual compounds may also be related to changes in carbon cycling within the peat, humidity and air temperature. The influence of local variations in ambient CO 2 (e.g., the canopy effect) cannot be excluded. [ABSTRACT FROM AUTHOR]