Microfossils from the late Mesoproterozoic - early Neoproterozoic Atar/EI Mreiti Group, Taoudeni Basin, Mauritania, northwestern Africa

The well-preserved Meso-Neoproterozoic shallow marine succession of the Atar/EI Mreiti Group, in the Taoudeni Basin, Mauritania, offers a unique opportunity to investigate the mid-Proterozoic eukaryotic record in Western Africa. Previous investigations focused on stromatolites, biomarkers, chemostratigraphy and palaeoredox conditions. However, only a very modest diversity of organic-walled microfossils (acritarchs) has been documented. Here, we present a new, exquisitely well-preserved and morphologically diverse assemblage of organic-walled microfossils from three cores drilled through the Atar/El Mreiti Group. A total of 48 distinct entities including 11 unambiguous eukaryotes (ornamented and process-bearing acritarchs), and 37 taxonomically unresolved taxa (including 9 possible eukaryotes, 6 probable prokaryotes, and 22 other prokaryotic or eukaryotic taxa) were observed. Black shales preserve locally abundant fragments of organic-rich laminae interpreted as benthic microbial mats. We also document one of the oldest records of Leiosphaeridia kulgunica, a species showing a circular opening interpreted as a sophisticated circular excystment structure (a pylome), and one of the oldest records of Trachyhystrichosphaera aimika and T. botula, two distinctive process-bearing acritarchs present in well dated 1.1 Ga formations at the base of the succession. The general assemblage composition and the presence of three possible index fossils (A. tetragonala, S. segmentata and T. aimika) support a late Mesoproterozoic to early Neoproterozoic (Tonian) age for the Atar/El Mreiti Group, consistent with published lithostratigraphy, chemostratigraphy and geochronology. This study provides the first evidence for a moderately diverse eukaryotic life, at least 1.1 billion years ago in Western Africa. Comparison with coeval worldwide assemblages indicates that a broadly similar microbial biosphere inhabited (generally redox-stratified) oceans, placing better time constraints on early eukaryote palaeogeography and biostratigraphy

Black shale deposition and early diagenetic dolomite cementation during Oceanic Anoxic Event 1: The mid-Cretaceous Maracaibo Platform, northwestern South America

Thin laterally continuous organic-rich dolomitic marlstones were deposited in the extended Late Aptian - Early Albian epicontinental sea of northwestern South America. These intervals are the proximal equivalents of thick hemipelagic black shale-ammonitic floatstone couplets, deposited in the distally stepped, differentially subsiding part of the Maracaibo Platform. The marlstones reflect the dynamic conditions resulting from orbital forcing mechanisms and can be genetically related to (1) minor sea-level changes, (2) proximal turnovers in marine productivity, and (3) sudden climate shifts affecting mid-Cretaceous shoaling upward, shallow marine, carbonate cyclicity. Therefore, the marlstones may well be linked to the multiple environmental perturbations collectively referred to as Oceanic Anoxic Event 1. The interstitial euhedral dolomite has a medium crystallinity, and exhibits unusual textural relations with framboidal pyrite and gypsum. The authigenic mineral assemblage also includes quartz, Ca-F apatite, and barite, which together with the chemical signals of dolomite, point to an unsteady climate regime. Bulk-rock biomarker parameters, rare earth element geochemistry, and iron speciation data point to widespread photic zone anoxia and transient shallow marine euxinia by the time of deposition, with climatic instability driving the delivery of oxidized detritus from the hinterlands. These conditions led to a schizohaline redox stratified environment favorable to dolomite precipitation. In such a depositional setting, the bio-utilization of Fe, Mn, and sulfur for organic matter respiration sustained elevated pore-water alkalinity and pH, and allowed for the pre-compactional growth of interstitial dolomite

Microfossils from the late Mesoproterozoic - early Neoproterozoic Atar/El Mreiti Group, Taoudeni Basin, Mauritania, northwestern Africa

The well-preserved Meso-Neoproterozoic shallow marine succession of the Atar/El Mreïti Group, in the Taoudeni Basin, Mauritania, offers a unique opportunity to investigate the mid-Proterozoic eukaryotic record in Western Africa. Previous investigations focused on stromatolites, biomarkers, chemostratigraphy and palaeoredox conditions. However, only a very modest diversity of organic-walled microfossils (acritarchs) has been documented. Here, we present a new, exquisitely well-preserved and morphologically diverse assemblage of organic-walled microfossils from three cores drilled through the Atar/El Mreïti Group. A total of 48 distinct entities including 11 unambiguous eukaryotes (ornamented and process-bearing acritarchs), and 37 taxonomically unresolved taxa (including 9 possible eukaryotes, 6 probable prokaryotes, and 22 other prokaryotic or eukaryotic taxa) were observed. Black shales preserve locally abundant fragments of organic-rich laminae interpreted as benthic microbial mats. We also document one of the oldest records of Leiosphaeridia kulgunica, a species showing a circular opening interpreted as a sophisticated circular excystment structure (a pylome), and one of the oldest records of Trachyhystrichosphaera aimika and T. botula, two distinctive process-bearing acritarchs present in well-dated 1.1 Ga formations at the base of the succession. The general assemblage composition and the presence of three possible index fossils (A. tetragonala, S. segmentata and T. aimika) support a late Mesoproterozoic to early Neoproterozoic (Tonian) age for the Atar/El Mreïti Group, consistent with published lithostratigraphy, chemostratigraphy and geochronology. This study provides the first evidence for a moderately diverse eukaryotic life, at least 1.1 billion years ago in Western Africa. Comparison with coeval worldwide assemblages indicates that a broadly similar microbial biosphere inhabited (generally redox-stratified) oceans, placing better time constraints on early eukaryote palaeogeography and biostratigraphy.Research support from BELSPO IAP PLANET TOPERS to J. Beghin (PhD scholarship) and E.J. Javaux (PI), and European Research Council (ERC) Stg ELiTE FP7/308074 to J.-Y. Storme (postdoc fellowship) and E.J. Javaux (PI) are gratefully acknowledged. J.J. Brocks acknowledges support from the Australian Research Council (DP1095247)

A palaeoecological model for the late Mesoproterozoic – early Neoproterozoic Atar/El Mreïti Group, Taoudeni Basin, Mauritania, northwestern Africa

Reconstructing the spatial distribution of early eukaryotes in palaeoenvironments through Proterozoic sedimentary basins provides important information about their palaeocology and taphonomic conditions. Here, we combine the geological context and a reconstruction of palaeoenvironmental redox conditions (using iron speciation) with quantitative analysis of microfossil assemblages (eukaryotes and incertae sedis), to provide the first palaeoecological model for the Atar/El Mreïti Group of the Taoudeni Basin. Our model suggests that in the late Mesoproterozoic – early Neoproterozoic, the availability of both molecular oxygen and nutrients controlled eukaryotic diversity, higher in oxic shallow marginal marine environments, while coccoidal colonies and benthic microbial mats dominated respectively in anoxic iron-rich and euxinic waters during marine highstands or away from shore where eukaryotes are lower or absent

Microbial assemblage and palaeoenvironmental reconstruction of the 1.38 Ga Velkerri Formation, McArthur Basin, northern Australia

The ca. 1.38 billion years (Ga) old Roper Group of the McArthur Basin, northern Australia, is one of the most extensive Proterozoic hydrocarbon-bearing units. Organic-rich black siltstones from the Velkerri Formation were deposited in a deep-water sequence and were analysed to determine their organic geochemical (biomarker) signatures, which were used to interpret the microbial diversity and palaeoenvironment of the Roper Seaway. The indigenous hydrocarbon biomarker assemblages describe a water column dominated by bacteria with large-scale heterotrophic reworking of the organic matter in the water column or bottom sediment. Possible evidence for microbial reworking includes a large unresolved complex mixture (UCM), high ratios of mid-chained and terminally branched monomethyl alkanes relative to n-alkanes-features characteristic of indigenous Proterozoic bitumen. Steranes, biomarkers for single-celled and multicellular eukaryotes, were below detection limits in all extracts analysed, despite eukaryotic microfossils having been previously identified in the Roper Group, albeit largely in organically lean shallower water facies. These data suggest that eukaryotes, while present in the Roper Seaway, were ecologically restricted and contributed little to export production. The 2,3,4- and 2,3,6-trimethyl aryl isoprenoids (TMAI) were absent or in very low concentration in the Velkerri Formation. The low abundance is primary and not caused by thermal destruction. The combination of increased dibenzothiophene in the Amungee Member of the Velkerri Formation and trace metal redox geochemistry suggests that degradation of carotenoids occurred during intermittent oxygen exposure at the sediment-water interface and/or the water column was rarely euxinic in the photic zone and likely only transiently euxinic at depth. A comparison of this work with recently published biomarker and trace elemental studies from other mid-Proterozoic basins demonstrates that microbial environments, water column geochemistry and basin redox were heterogeneous.Amber J. M. Jarrett, Grant M. Cox, Jochen J. Brocks, Emmanuelle Grosjean Chris J. Boreham, Dianne S. Edward

Microfossils from the late Mesoproterozoic – early Neoproterozoic Atar/El Mreïti Group, Taoudeni Basin, Mauritania, northwestern Africa

The well-preserved Meso-Neoproterozoic shallow marine succession of the Atar/El Mreïti Group, in the Taoudeni Basin, Mauritania, offers a unique opportunity to investigate the mid-Proterozoic eukaryotic record in Western Africa. Previous investigations focused on stromatolites, biomarkers, chemostratigraphy and palaeoredox conditions. However, only a very modest diversity of organic-walled microfossils (acritarchs) has been documented. Here, we present a new, exquisitely well-preserved and morphologically diverse assemblage of organic-walled microfossils from three cores drilled through the Atar/El Mreïti Group. A total of 48 distinct entities including 11 unambiguous eukaryotes (ornamented and process-bearing acritarchs), and 37 taxonomically unresolved taxa (including 9 possible eukaryotes, 6 probable prokaryotes, and 22 other prokaryotic or eukaryotic taxa) were observed. Black shales preserve locally abundant fragments of benthic microbial mats. We also document one of the oldest records of Leiosphaeridia kulgunica, a species showing a pylome interpreted as a sophisticated circular excystment structure, and one of the oldest records of Trachyhystrichosphaera aimika and T. botula, two distinctive process-bearing acritarchs present in well-dated 1.1 Ga formations at the base of the succession. The general assemblage composition and the presence of three possible index fossils (A. tetragonala, S. segmentata and T. aimika) support a late Mesoproterozoic to early Neoproterozoic (Tonian) age for the Atar/El Mreïti Group, consistent with published lithostratigraphy, chemostratigraphy and geochronology. This study provides the first evidence for a moderately diverse eukaryotic life, at least 1.1 billion years ago in Western Africa. Comparison with coeval worldwide assemblages indicate that a broadly similar microbial biosphere inhabited (generally redox-stratified) oceans, placing better time constraints on early eukaryote palaeogeography and biostratigraphy

Challenging European borders : Fatih Akın's filmic visions of Europe

textIn my dissertation, I discuss three of Akın’s feature films: Im Juli (In July, 2000), Gegen die Wand (Head-On, 2004), and Auf der anderen Seite (The Edge of Heaven, 2007) in order to investigate Akın’s filmic visions of Europe. Through close textual readings, I analyze three aspects of his films in particular: the spatial conceptions of Europe (city- and landscapes), the sounds of Europe (music and languages) as well as the display of ethnic minorities and the changing urban demography in Germany and Europe. I argue that Akın employs an “aesthetic of heterogeneity” to portray his filmic Europe as a diverse space, in which multiethnic and multilingual music, people, and sceneries are juxtaposed with regions that often have been perceived historically and politically as distinct and complicated. My first chapter discusses Akın’s conceptions and depictions of European Space in In July. By analyzing city- and landscapes, soundscapes, and dynamic spaces in In July, I argue that Akın provides a dynamic, fluctuating, and interconnected European space, including Eastern Europe and Turkey. In my second chapter, I scrutinize language use and dialogue in Head-On to map out the changing demographics in European urban spaces. Ultimately, I argue that Akın moves beyond Hamid Naficy’s theory of “accented cinema” by including accented languages and dialects for all protagonists, including Western Europeans. Through this linguistic polyphony, multilingualism and a diversity of accents are depicted as integral elements of today’s Europe. In my final chapter, I discuss the sound of Europe as depicted in The Edge of Heaven. Looking particularly at music (and music lyrics) in the film, I argue that Akın’s use of dubbed and remixed music (especially by the artist Shantel) underscores Akın’s filmic challenges to (national) European borders. By foregrounding the mixed styles of music, where an “original” becomes hard to decipher, the director shows, on an aural level, that blurring boundaries and multidirectional movement are the predominant components of today’s Europe.Germanic Studie

Late Mesoproterozoic Microbial Communities

The first eukaryotes are found in the geological record at ~1.6 Ga, a further 800 million years later they became more abundant and diverse, and only during the Ediacaran did they start shaping ecosystems. This work studies a marine and a lacustrine aquatic ecosystem at the edge of the Mesoproterozoic (~1.1 Ga) to gauge the role of eukaryotes and to investigate the environmental conditions that may have prohibited their proliferation. The evolutionary state of the earliest eukaryotic fossils remains unresolved. The first unambiguous stem group eukaryote appears at 1.2 Ga, but modern ferns occur around 0.8 Ga. Extreme bias on fossil preservation prevents estimation on how ecologically abundant early eukaryotes were. Here we use biomarkers to close this gap. They have low taxonomic resolution but afford a quantitative view of relative organism abundances. We combine biomarkers with inorganic, isotope geochemical and microscope analysis to investigate successions of the marine Taoudeni Basin and lacustrine Nonesuch Formation. Further, we include an analysis of the Cretaceous Maracaibo Basin to obtain a clear point of contrast from a period of time where redox environments were similar but eukaryotes were abundant. The extraordinary black shales of the Taoudeni Basin have high TOC (< 31 %), lack eukaryotic steranes despite present eukaryotic microfossils, contain aromatic steroids, and are mostly deposited under ferruginous and euxinic conditions. This implies at first sight a stagnant deep water environment. Yet, clear crinkly mats are preserved, invoking a non-uniformitarian ecosystem. Low atmospheric oxygen levels facilitate to explain clear, anoxic, shallow (<20 m) waters above phototrophic microbial mats. Biomarker data imply that the microbial community was composed of cyanobacteria, anoxygenic purple and green sulfur bacteria, and microaerophilic methanotrophs. It is likely that cyanobacteria switched between oxic and anoxic photosynthesis and dominated the photosynthetic community. The latter is supported by nitrogen isotopic composition of individual porphyrins, which range between 5.6 and 10.2 per mil and yield epsilon-porphyrin values of 0.5 to - 5.1 per mil. This study is the first unambiguous report of Mesoproterozoic geoporphyrins. The dominant species contain Ni and their structures relate to chl a, chl b/chl c3 and a chl c-like molecule. The biomarker and iron speciation results of Nonesuch shales qualitatively resemble the ones of the marine Taoudeni Basin including a mainly ferruginous depositional setting, absence of diagnostic eukaryotic biomarkers despite eukaryotic microfossils and biomarkers specific for cyanobacteria, anoxygenic purple and green sulfur bacteria, and microaerophilic methanotrophs. The bitumens of the Phanerozoic Maracaibo Basin were composed of degradation products of marine algae, green sulfur bacteria and archaea as well as terrestrial higher plants and lacustrine algae. The mixing of two components, marine and terrestrial organic matter, can explain the distribution of biomarkers. The data describe the restricted Maracaibo Basin as a stable, stratified sea influenced by upwelling waters near a shallow shelf. The results exemplify that biomarkers of primary producers such as algae are in fact preserved in similar environments as in the Mesoproterozoic and that the absence in ~1 Ga samples is not a preservation artefact