Messel Oil Shale Research Articles

Isoprenoidal GDGTs and GDDs associated with anoxic lacustrine environments

We examined membrane-spanning archaeal lipids using ultra high pressure liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS) in a suite of sediment samples from both cored sequences (Messel oil shale and Lake Chala) and surface sediments (Azorean lakes) encompassing ancient and modern (Eocene to Present) lacustrine environments. Additionally we compared the lacustrine data to those of marine (Mediterranean cored sequences, Arabian Sea surface sediments and Monterey outcrop sediments) and hypersaline sediments (Vena del Gesso marls) as well as marine suspended particulate matter (SPM) from the Black Sea. Regular isoprenoidal glycerol dialkyl glycerol tetraethers (GDGTs) and glycerol dialkyl diethers (GDDs) were the most abundant membrane-spanning lipids in all investigated settings (>90 % and 84 % respectively). Interestingly, GDGTs with a cyclohexyl ring (S-GDGTs) were also present in almost all investigated lake sediments, in relative abundances of ca. 2–7 % and, for the first time, also their S-GDD counterparts were detected (2–10 %). The producers of S-GDGTs are still unknown, however our results show that it is likely that bottom water anoxia (both seasonally induced or permanent) is the driving factor for the production of these lipids, whereas previous studies suggested euxinia was required for production. Unsaturated GDGTs (uns-GDGTs, ca. 2 %) were only detected in Lake Chala sediments and surface sediments from Azorean lakes, but without accompanying uns-GDDs. GMGTs, glycerol monoalkyl glycerol tetraethers, were present in Messel oil shale and marine samples, while GMDs were only found in Messel oil shale.

Towards completion of the early Eocene aviary: A new bird group fromthe Messel oil shale (Aves, Eopachypterygidae, fam. nov.).

A new avian species is described from the early Eocene Messel fossil site in Germany. Eopachypteryx praeterita, gen. et sp. nov. is a small bird and exhibits a characteristic morphology with a short and robust beak, a distinctively shaped coracoid, stout humerus, robust pectoral girdle skeleton, and short hindlimbs. Although similarities to the Paleogene Eocuculus as well as to some extant telluravian and strisorine taxa are noted, the phylogenetic affinities of the new species are unresolved. To account for the fact that the new species is clearly distinguished from any of the known fossil or extant avian taxa, it is here assigned to the new taxon Eopachypterygidae, fam. nov.. Eopachypteryx praeterita is represented by three partial skeletons. A further partial skeleton from Messel belongs to a second, unnamed species, which is tentatively referred to Eopachypteryx.

New palynology-based astronomical and revised 40Ar/39Ar ages for the Eocene maar lake of Messel (Germany)

The annually laminated oil shale from the Eocene maar lake at Messel (Federal State of Hessen, Germany) provides unique paleoenvironmental data for a time interval of ~640 ka during the Paleogene greenhouse phase. As a consequence of orbitally controlled changes in the vegetation in the vicinity of the lake, the lacustrine laminites can now be astronomically tuned. Dating is based on the short eccentricity amplitude modulations of the regional pollen rain and their correlation to the astronomical La2010a/La2010d solutions in combination with a revised 40Ar/39Ar age of a basalt fragment from a lapilli tuff section below the first lacustrine sediments. Depending on different newly suggested ages for the Fish Canyon sanidine used as monitor for neutron irradiation, the age for the eruption at Messel is between 48.27 ± 0.22 and 48.11 ± 0.22 Ma. This allows for the first time the exact correlation of a Paleogene lacustrine sequence to the marine record in Central Europe. The Messel oil shale becomes now slightly older than previously assumed and includes the Ypresian/Lutetian boundary that moves the base of the European Land Mammal Age Geiseltalian (MP 11) into the Lower Eocene. This opens a window for establishing an independent chronostratigraphic framework for Paleogene terrestrial records and their correlation to the marine realm. Furthermore, the study reveals that higher amounts of pollen from “wet” and thermophilous plants indicate less seasonal and more balanced precipitation and slightly higher temperatures during a well-expressed eccentricity minimum.

Characterization of the sedimentary organic matter preserved in Messel oil shale by bulk geochemistry and stable isotopes

We investigated a 150m thick drill core section of Messel oil shale using bulk geochemical and stable isotope techniques in order to determine the organic matter sources and the environmental conditions that prevailed during the deposition of the lacustrine sequence. High Corg values (on average 27%) indicate that the Messel oil shale has likely been deposited under highly productive conditions and/or in an environment largely free of oxygen, which suggests a permanent stratification of the paleolake and prolonged periods of bottom water anoxia. Low stable nitrogen isotope values (ca. +1 to +2‰), observed at the transition from holomictic to meromictic conditions, suggest a brief period of an increased contribution of diazotrophic, possibly heterocystous, cyanobacteria that proliferated under the stagnant conditions. The basal oil shale unit (Lower Messel-Formation) is characterized by generally high HI values (>570mg HC/g Corg) and molar Corg/Ntot ratios (>35) that evidence an increased loading of terrestrial organic matter to the lake system, which is hypothesized to be dominated by the lipid-rich constituents of vascular plants. The oil shale of the mid-section (Middle Messel-Formation) is characterized by carbon isotope excursions towards comparatively heavy δ13Corg values of −24‰ that together with slightly lower Corg/Ntot ratios (ca. 30) of this interval are taken as evidence for a higher loading of aquatic-derived organic matter to the paleolake. The uppermost part of the Middle Messel-Formation displays decreasing δ13Corg and concomitantly high δ15Ntot values, which is interpreted to indicate an increased importance of bacterial driven processes (such as methanogenesis, methanotrophy and denitrification) in the paleolake system. Our results thus indicate that the Eocene maar lake received organic matter from various autochthonous and allochthonous sources with contributions of each source varying significantly over the lake's existence.

Exceptional three-dimensional preservation and coloration of an originally iridescent fossil feather from the Middle Eocene Messel Oil Shale

A feather from the Eocene Messel Formation, Germany, has been demonstrated to have been originally structurally colored by densely packed sheets of melanosomes similar to modern iridescent feathers exhibiting thin-film diffraction. The fossil itself currently exhibits a silvery sheen, but the mechanism for generating this optical effect was not fully understood. Here we use scanning electron microscopy, electron probe microanalysis, and dual-beam focused ion beam scanning electron microscopy to investigate the source of the silvery sheen that occurs in the apical feather barbules. Focused ion beam scanning electron microscopy provides a powerful tool for studying three-dimensionality of nanostructures in fossils. Use of the method reveals that the flattened apical barbules are preserved almost perfectly, including smooth structural melanosome sheets on the obverse surface of the fossil feather that are identical to those that cause iridescence in modern bird feathers. Most of each apical barbule is preserved beneath a thin layer of sediment. The silvery sheen is generated by incoherent light diffraction between this sediment layer and melanosomes and, although related to the original iridescence of the feather, is not a feature of the feather itself. The reddish and greenish hues frequently exhibited by fossil feathers from the Messel Formation appear to be due to precipitates on the surface of individual melanosomes.

Lu–Hf isotope systematics of fossil biogenic apatite and their effects on geochronology

Reliable methods for direct dating of biogenic apatite from pre-Pleistocene fossils are currently not available, and recent attempts using the Lu–Hf decay system yielded highly inaccurate ages for both bones and teeth. The geological processes accounting for this poor accuracy of Lu–Hf chronometry are not yet understood. Here we explore Lu–Hf systematics in fossil bones and teeth in detail, by applying five different sample digestion techniques that are tested on bones and composites of bone and sediment. Our current dataset implies that dissolution methods only slightly affect the resulting Lu–Hf ages, while clear differences between the individual digestion techniques became apparent for element concentrations. By analysing the insoluble leftovers from incomplete sample dissolution, four main reservoirs of Hf in fossil bones were identified: (1) a radiogenic end-member associated with apatite; (2) an unradiogenic end-member represented by the authigenic minerals or the embedding sediment; (3) a highly unradiogenic end-member that can be attributed to detrital zircon; and (4) a moderately soluble phase (probably a Zr(Hf)-phosphate) that yielded very low Lu/Hf but a highly radiogenic Hf isotope composition at the same time. This Zr(Hf)-phase must have been precipitated within the fossil bone sample at a late stage of burial history, thereby incorporating radiogenic 176Hf released from apatite surfaces over geological timescales.A second focus of our study is the effect of different sediment matrices and of crystal size on the preservation of pristine Lu–Hf isotope compositions in bioapatite. Because near-depositional Lu–Hf ages of phosphate fossils have previously been reported for the London Clay (England) and a calcareous marl from Tendaguru (Tanzania), we herein investigate specimens fossilised in carbonate matrices (calcareous marl from Oker, Germany; carbonate concretions from the Santana Formation, Brazil; carbonate from the Eifel, Germany) and argillaceous matrices with low permeability (oil shale of Messel, Germany; Posidonienschiefer of Holzmaden, Germany). Materials analysed from these localities include bones, teeth, conodonts, as well as coproliths and diagenetic minerals (siderite, montgomeryite and messelite). Near-depositional Lu–Hf ages were obtained for a bony fish sample (Notelops brama) encapsulated in an early diagenetic carbonate concretion from the Early Cretaceous Santana Formation, Brazil and for conodonts from a Middle Devonian carbonate from the Eifel, Germany. Low 176Lu/177Hf ratios in all materials from the Middle Eocene Messel oil shale (e.g., bones, fish scales, sediment, siderite) result in poor age precision and an age that is near-depositional due to this large analytical error. In agreement with previous results, all other ages determined here for both bones and teeth are by far younger than respective chronostratigraphic ages.A model illustrating the behaviour of Lu and Hf over time, with respect to the fossilisation process is presented, which accounts both for the formation of a late diagenetic radiogenic Zr(Hf) phase and long term open system behaviour. The continuous Lu–Hf element exchange between the fossils and the embedding sediment is probably related to the nm-scale crystal size of fossil bones, dentine and also of enamel that generate large surface areas facilitating sorption/desorption processes and open system behaviour.

075 Digital visualisation of fossil fruits and seeds from the Eocene Messel oil shale

075 Digital visualisation of fossil fruits and seeds from the Eocene Messel oil shale

Fossilized Biophotonic Nanostructures Reveal the Original Colors of 47-Million-Year-Old Moths

Author SummaryBiological structural colors are generated when light is scattered by nanostructures in tissues. Such colors have diverse functions for communication both among and between species. Structural colors are most complex in extant butterflies and moths (lepidopterans), but the evolution of such colors and their functions in this group of organisms is poorly understood. Fossils can provide insights into the evolution of biological structures, but evidence of structurally colored tissues was hitherto unknown in fossil lepidopterans. Here, we report the preservation of structurally colored scales in fossil moths with striking metallic hues from the ∼47-million-year-old (Eocene) GrubeMessel oil shales (Germany). We identify the color-producing nanostructure in the scales and show that the original colors were altered during fossilization. Preserved details in the scales allow us to reconstruct the original colors and show that the dorsal surface of the forewings was yellow-green. The optical properties of the scales strongly indicate that the color functioned as a warning signal during feeding but was cryptic when the moths were at rest. Our results confirm that structural colors can be reconstructed even in non-metallic lepidopteran fossils and show that defensive structural coloration had evolved in insects by the mid-Eocene.

Short-term fluctuations in vegetation and phytoplankton during the Middle Eocene greenhouse climate: a 640-kyr record from the Messel oil shale (Germany)

The Palaeogene was the most recent greenhouse period on Earth. Especially for the Late Palaeocene and Early Eocene, several superimposed short-term hyperthermal events have been described, including extremes such as the Palaeocene–Eocene Thermal Maximum. Major faunal and floral turnovers in the marine and terrestrial realms were recorded in association with these events. High-resolution palynological analysis of the early Middle Eocene maar lake sediments at Messel, near Darmstadt, Germany, provides an insight into the dynamics of a climax vegetation during the Middle Eocene greenhouse climate in a time span without significant climatic excursions. Numerical techniques like detrended correspondence analysis and wavelet analysis have been applied to recognize cyclic fluctuations and long-term trends in the vegetation through a time interval of approximately 640 kyr. Based on the numerical zoning of the pollen diagram, three phases in the development of the vegetation may be distinguished. Throughout these phases, the climax vegetation did not change substantially in qualitative composition, but a trend towards noticeably less humid conditions probably in combination with a drop of the water level in the lake may be recognized. A shift in algal population from the freshwater dinoflagellate cyst Messelodinium thielepfeifferae to a dominance of Botryococcus in the uppermost part of the core is interpreted as a response to changes in acidity and nutrient availability within the lake. Time series analyses of pollen assemblages show that variations in the Milankovitch range of eccentricity, obliquity and precession can be distinguished. In addition, fluctuations in the sub-Milankovitch range are indicated. This demonstrates that floral changes during steady depositional conditions in the Middle Eocene of Messel were controlled by orbital forcing.

Structural coloration in a fossil feather

Investigation of feathers from the famous Middle Eocene Messel Oil Shale near Darmstadt, Germany shows that they are preserved as arrays of fossilized melanosomes, the surrounding beta-keratin having degraded. The majority of feathers are preserved as aligned rod-shaped eumelanosomes. In some, however, the barbules of the open pennaceous, distal portion of the feather vane are preserved as a continuous external layer of closely packed melanosomes enclosing loosely aligned melanosomes. This arrangement is similar to the single thin-film nanostructure that generates an iridescent, structurally coloured sheen on the surface of black feathers in many lineages of living birds. This is, to our knowledge, the first evidence of preservation of a colour-producing nanostructure in a fossil feather and confirms the potential for determining colour differences in ancient birds and other dinosaurs.

Potential of palynostratigraphic resolution in a homogeneous lacustrine succession: the Middle Eocene Messel Formation

Palynologieal results from two cores of the Middle Eocene Messel oil shale (Germany)are compared and tested for their reliability in stratigraphic correlation and suitability for time series analysis. The studied section of 139 m respectively 126.5 m mainly of annually laminated oil shale represents a time interval of less than I my during the Eocene greenhouse phase. Frequency curves and running means are shown for examples of restricted distribution (Restionaceae, Pinaceae pollen), rare (Labrapollis labraferus, Pentapollenites spp.), common (various pollen of Juglandaceae) and dominat occurrence (Plicatopollis spp., Tricolpopollenites liblarensis /Tricolporopollenites cingulum group). They show good correspondence between the two cores even in minor quantitative changes and thus confirm the fidelity by which vegetation changes in the vicinity are reflected in the homogeneous sediments of a lacustrine basin.

Distribution and paleoecologic significance of the freshwater dinoflagellate cyst Messelodinium thielepfeifferae gen. et sp. nov from the Middle Eocene of Lake Messel, Germany

An exploration well drilled at the Middle Eocene fossil site of Messel, near Darmstadt, Germany proved that the famous Messel oil shale was deposited in a maar lake. During a quantitative palynological investigation of the entire succession of lake sediments, a monospecific population of dinoflagellate cysts was encountered. Based on transmitted light and scanning electron microscope (SEM) studies, they are assigned to the new peridinioid taxon Messelodinium thielepfeifferae gen. et sp. nov. because they are acavate and lack distinct apical or antapical horns. The dinoflagellate cysts exhibit considerable intraspecific variation in surface ornamentation. Messelodinium thielepfeifferae gen. et sp. nov. is abundant in sediments of the early holomictic stage of Lake Messel, but generally is reduced in frequency in the oil shale which represents the meromictic stage. These dinoflagellate cysts appear in peak abundances in mass flow and debris flow deposits in which material from the lake shore was transported downslope to the basin center. Thus, major concentrations of Messelodinium thielepfeifferae gen. et sp. nov. occurred in nearshore environments either due to primary population density of the parent motile stage, or due to secondary cyst accumulation by wind and wave action. The dinoflagellate cysts are notably absent in the uppermost 25 m of the core, where Botryococcus dominates. This shift in algal populations is interpreted as a response to changes in the chemistry of the water body.

DISTRIBUTION AND PALEOECOLOGIC SIGNIFICANCE OF THE FRESHWATER DINOFLAGELLATE CYST MESSELODINIUM THIELEPFEIFFERAE GEN. ET SP. NOV FROM THE MIDDLE EOCENE OF LAKE MESSEL, GERMANY

An exploration well drilled at the Middle Eocene fossil site of Messel, near Darmstadt, Germany proved that the famous Messel oil shale was deposited in a maar lake. During a quantitative palynological investigation of the entire succession of lake sediments, a monospecific population of dinoflagellate cysts was encountered. Based on transmitted light and scanning electron microscope (SEM) studies, they are assigned to the new peridinioid taxon Messelodinium thielepfeifferae gen. et sp. nov. because they are acavate and lack distinct apical or antapical horns. The dinoflagellate cysts exhibit considerable intraspecific variation in surface ornamentation. Messelodinium thielepfeifferae gen. et sp. nov. is abundant in sediments of the early holomictic stage of Lake Messel, but generally is reduced in frequency in the oil shale which represents the meromictic stage. These dinoflagellate cysts appear in peak abundances in mass flow and debris flow deposits in which material from the lake shore was transported downslope to the basin center. Thus, major concentrations of Messelodinium thielepfeifferae gen. et sp. nov. occurred in nearshore environments either due to primary population density of the parent motile stage, or due to secondary cyst accumulation by wind and wave action. The dinoflagellate cysts are notably absent in the uppermost 25 m of the core, where Botryococcus dominates. This shift in algal populations is interpreted as a response to changes in the chemistry of the water body.

06/02521 C40 monoaromatic lycopane derivatives as indicators of the contribution of the alga Botryococcus braunii race L to the organic matter of Messel oil shale (Eocene, Germany)Adam, P. et al. Organic Geochemistry, 2006, 37, (5), 584–596

06/02521 C40 monoaromatic lycopane derivatives as indicators of the contribution of the alga Botryococcus braunii race L to the organic matter of Messel oil shale (Eocene, Germany)Adam, P. et al. Organic Geochemistry, 2006, 37, (5), 584–596

C 40 monoaromatic lycopane derivatives as indicators of the contribution of the alga Botryococcus braunii race L to the organic matter of Messel oil shale (Eocene, Germany)

A novel series of sedimentary aromatic lycopane derivatives, cyclolycopatrienes, has been found in an outcrop sample from the Messel oil shale. The predominant monoaromatic compound 4 from this hydrocarbon series has been isolated using reversed phase HPLC and its structure determined using 1D and 2D 1H NMR spectroscopy, as well as from identification of the RuO 4 degradation products. From examination of its structure, related to that of lycopane, and from its stable carbon isotopic composition, this compound and related isomers can be considered as new proxies for Botryococcus braunii race L in sediments deposited under freshwater and/or brackish conditions.

Degradation of 5α-cholestane into dimethylperhydrophenanthrenes: an experimental and theoretical study

A tetradeuteriated cholestane was heated with kerogen isolated from the Messel oil shale at 350 °C for 25 different time periods (ranging from 0.5 to 80 h) in borosilicate vessels. Three isomers of tetradeuteriated dimethylperhydrophenanthrene were formed and one of these was the major saturated hydrocarbon product under most conditions. The stereochemistry for these isomers was unknown but if the stable 5α,8β,9α(H),10β(CH3) sterane configuration is inherited from the cholestane then there are four possible isomers namely: I and II [13β(H) and 13α(H) diastereomers, respectively, of 10,13-dimethylperhydrophenanthrene] as well as III and IV [14β(H) and 14α(H) diastereomers, respectively, of 10,14-dimethylperhydrophenanthrene]. Molecular mechanics revealed that I is the most stable form and therefore is the component that dominated the saturated hydrocarbon degradation products. The identification of only three isomers of deuteriated dimethylperhydrophenanthrene in the pyrolysis experiments is supported by the calculated stabilities (ΔΔG) as isomer IV is considerably more unstable (by 1.7 kcal/mol) than II which is the least stable of I, II and III. If these compounds can be detected in crude oils their distributions may be useful maturity indicators in oils that have been generated at high thermal maturity.

Degradation of 5α-cholestane into dimethylperhydrophenanthrenes: an experimental and theoretical study

A tetradeuteriated cholestane was heated with kerogen isolated from the Messel oil shale at 350 °C for 25 different time periods (ranging from 0.5 to 80 h) in borosilicate vessels. Three isomers of tetradeuteriated dimethylperhydrophenanthrene were formed and one of these was the major saturated hydrocarbon product under most conditions. The stereochemistry for these isomers was unknown but if the stable 5α,8β,9α(H),10β(CH 3) sterane configuration is inherited from the cholestane then there are four possible isomers namely: I and II [13β(H) and 13α(H) diastereomers, respectively, of 10,13-dimethylperhydrophenanthrene] as well as III and IV [14β(H) and 14α(H) diastereomers, respectively, of 10,14-dimethylperhydrophenanthrene]. Molecular mechanics revealed that I is the most stable form and therefore is the component that dominated the saturated hydrocarbon degradation products. The identification of only three isomers of deuteriated dimethylperhydrophenanthrene in the pyrolysis experiments is supported by the calculated stabilities (ΔΔ G) as isomer IV is considerably more unstable (by 1.7 kcal/mol) than II which is the least stable of I, II and III. If these compounds can be detected in crude oils their distributions may be useful maturity indicators in oils that have been generated at high thermal maturity.

New methods applied to the microstructure analysis of Messel oil shale: confocal laser scanning microscopy (CLSM) and environmental scanning electron microscopy (ESEM)

Investigations of mass movements of the Messel oil shale in Germany presumed that swell- and especially shrink-deformations of the organic-rich clay were among the factors triggering initial displacements. Within the scope of the present studies, delicate clay/organic microstructures had to be deciphered. Reactions of clay minerals and microstructures upon dehydration were observed by environmental scanning electron microscopy (ESEM) and the distribution of organic matter was studied by confocal laser scanning microscopy (CLSM) in fluorescence mode. ESEM and CLSM have been demonstrated to be valuable tools for the microstructural characterization of laminated organic-rich sediments. The application of these analytical and imaging techniques will be of great interest to a wide range of geological disciplines such as palaeontology, organic petrology, engineering geology and global change studies.

The stereochemistry of bound and extractable pentacyclic triterpenoids during closed system pyrolysis

The distributions of hopanoic acids, ranging from C30 to C34, in the Messel oil shale were characterized in both the free and bound states. The bound acids were released by thermochemolysis in the presence of tetramethylammonium hydroxide (TMAH). These were compared with the distributions of the hopanoic acids and hopanes released or generated from Messel oil shale kerogen following closed system microscale pyrolysis. This comparison revealed that epimerization had occurred at C-17, C-21 and C-22 during heating. It was also clear that the residual bound hopanoic acids had undergone configurational isomerization. During the pyrolysis there is a large loss of hopanoic acids following their rapid release from the kerogen into the free fraction even at 250 °C. In these particular experiments this loss does not appear to result in exclusive formation of hopanes, by way of decarboxylation or reduction reactions, unless the resulting hopanes are either themselves rapidly transformed into other compounds or the reaction rates are a function of the total number of carbon atoms in each hopanoic acid precursor.

Kerogen-bound and free hopanoic acids in the Messel oil shale kerogen

Kerogen-bound and free hopanoic acids in the Messel oil shale kerogen