Palynology of a coal seam in Karoo deposits of Botswana and correlation with southern African coal-bearing strata

A significant amount of palynological work has been done on southern African coal seams in the Ecca Group, but as yet there is little consensus on how these areas relate to each other. This study investigated the palynology of a coal seam from Mmamantswe (Mmamabula area), Botswana, approximately 70 km north-east of Gaborone. A total of 124 samples were taken from two borehole cores and subjected to acid preparation, oxidation and acetolysis. Coal samples were found to be barren of palynomorphs. Fifty carbonaceous mudstones and siltstone samples yielded twenty-two productive samples. A thermal alteration index of 3.0-3.5 was assigned for the sediments. Palynomorph diversity was high, with 64 genera and 90 species present, dominated by trilete and alete spores. This indicates a parent flora of mostly lower order lycopods, sphenophytes and ferns. Non-taeniate bisaccate and monosaccate pollens were scarce, and striates extremely rare (only two species), suggesting an autochthonous origin for the coal swamp. The Mmamantswe core was sub-divided into five microfloral assemblage zones. A transition from monosaccate dominance in the lower part of the core, to equal numbers of monosaccates and non-taeniate bisaccates in the upper part of the core, was seen. As the Mmamantswe palynoflora possesses elements of both the Late Carboniferous glacial floras and the mid-Permian coal floras, it is thought to represent a cross-over assemblage dating to soon after the Permo-Carboniferous boundary (Sakmarian and Early Artinskian). The Mmamantswe assemblage can be correlated with Assemblage Zones II and III of Falcon (1975a); Biozones B and C of MacRae (1988); and Zones 1, 2 and 3 of Anderson (1977) but does not fit well into any existing biozonation. The Mmamantswe palynoflora was most similar to that of Milorgfjella, Dronning Maud Land, Antarctica (Larrson et al. 1990) and the No. 2 Seam, Witbank, South Africa (Falcon 1989). Taphonomic controls on palynomorph preservation suggest that future studies should also attempt to focus on Permian sediments not containing coal, as microfloral assemblages from coal seams tend to be autochthonous, and subject to local climatic influences. Accordingly they are not as useful for inter-basinal correlation across Gondwana

The evolutionary history of the Central Asian steppe-desert taxon Nitraria (Nitrariaceae) as revealed by integration of fossil pollen morphology and molecular data

The transition from a greenhouse to an icehouse world at the Eocene-Oligocene Transition (EOT) coincided with a large decrease of pollen from the steppe-adapted genus Nitraria. This genus, now common along the Mediterranean coast, Asia and Australia, has a proposed coastal origin and a geographically widespread fossil record. Here we investigated the evolution, taxonomic diversity and morphological disparity of Nitraria throughout the Cenozoic by integrating extant taxa and fossil palynological morphotypes into a unified phylogenetic framework based on both DNA sequences and pollen morphological data. We present the oldest fossil pollen grain of Nitraria, at least 53 Myr old. This fossil was found in Central Asian deposits, providing new evidence for its origin in this area. We found that the EOT is an evolutionary bottleneck for Nitraria, coinciding with retreat of the proto-Paratethys Sea, a major global cooling event and a turnover in Central Asian steppe vegetation. We infer the crown age of modern Nitraria spp. to be significantly younger (Miocene) than previously estimated (Palaeocene). The diversity trajectory of Nitraria inferred from extant-only taxa differs markedly from one that also considers extinct taxa. Our study demonstrates it is therefore critical to apply an integrative approach to fully understand the plant evolutionary history of Nitrariaceae.publishedVersio

Sporopollenin chemistry and its durability in the geological record: an integration of extant and fossil chemical data across the seed plants.

Sporopollenin is a highly resistant biopolymer that forms the outer wall of pollen and spores (sporomorphs). Recent research into sporopollenin chemistry has opened up a range of new avenues for palynological research, including chemotaxonomic classification of morphologically cryptic taxa. However, there have been limited attempts to directly integrate extant and fossil sporopollenin chemical data. Of particular importance is the impact of sample processing to isolate sporopollenin from fresh sporomorphs, and the extent of chemical changes that occur once sporomorphs enter the geological record. Here, we explore these issues using Fourier transform infrared (FTIR) microspectroscopy data from extant and fossil grass, Nitraria (a steppe plant), and conifer pollen. We show a 98% classification success rate at subfamily level with extant grass pollen, demonstrating a strong taxonomic signature in isolated sporopollenin. However, we also reveal substantial chemical differences between extant and fossil sporopollenin, which can be tied to both early diagenetic changes acting on the sporomorphs and chemical derivates of sample processing. Our results demonstrate that directly integrating extant and late Quaternary chemical data should be tractable as long as comparable sample processing routines are maintained. Consistent differences between extant and deeper time sporomorphs, however, suggests that classifying fossil specimens using extant training sets will be challenging. Further work is therefore required to understand and simulate the effects of diagenetic processes on sporopollenin chemistry

ICDP workshop on scientific drilling of Nam Co on the Tibetan Plateau: 1 million years of paleoenvironmental history, geomicrobiology, tectonics and paleomagnetism derived from sediments of a high-altitude lake

The Tibetan Plateau is of peculiar societal relevance as it provides freshwater from the so-called “Water Tower of Asia” to a large portion of the Asian population. However, future climate change will affect the hydrological cycle in this area. To define parameters for future climate change scenarios it is necessary to improve the knowledge about thresholds, timing, pace and intensity of past climatic changes and associated environmental impacts. Sedimentary archives reaching far back in time and spanning several glacial–interglacial cycles such as Nam Co provide the unique possibility to extract such information. In order to explore the scientific opportunities that an ICDP drilling effort at Nam Co would provide, 40 scientists from 13 countries representing various scientific disciplines met in Beijing from 22 to 24 May 2018. Besides paleoclimatic investigations, opportunities for paleomagnetic, deep biosphere, tectonic and paleobiological studies were discussed. After having explored the technical and logistical challenges and the scientific opportunities all participants agreed on the great value and need to drill this extraordinary archive, which has a sediment thickness of more than 1 km, likely covering more than 1 Ma

Palynostratigraphy of the South African Karoo supergroup and correlations with coeval Gondwanan successions

The Main Karoo Basin of South Africa is renowned for its exceptional palaeontological record and while its vertebrate fossils have been extensively researched, Karoo floras have received considerably less attention. Poor yields of palynomorphs from the Beaufort and “Stormberg” groups have complicated the task of erecting a comprehensive palynozonation scheme for the Karoo Supergroup. For this study, 65 palynologically productive samples from the Dwyka, Ecca, Beaufort and “Stormberg” groups allowed for systematic descriptions of all palynomorphs, as well as the ranges of the different taxa through the entire Karoo stratigraphic succession. Taxa with restricted ranges are useful for biostratigraphic correlation and these palynomorphs were used to delineate microfloral zones for the Karoo basin. The Dwyka Group contains high numbers of acritarchs and is generally low in species diversity. Useful biostratigraphic taxa for the Ecca Group include Cannanoropollis, Hamiapollenites, Platysaccus and Striatopodocarpites. Aratrisporites is a marker for the Latest Permian / Early Triassic Beaufort Group, while Cyathidites, Dictyophyllidites, Equisetosporites and Uvaesporites are indicators of the Late Triassic / Early Jurassic “Stormberg” Group. Palynostratigraphic zones correlate largely with the Karoo vertebrate biozones and severe and sudden extinction events are recognised among Karoo palynomorphs in the upper Tapinocephalus and Dicynodon assemblage zones. The first comprehensive palynological biozonation scheme for the Main Karoo Basin is proposed and the study provides a broad overview of Gondwanan Carboniferous - Jurassic floras. This study demonstrates that palynology is useful in correlating age equivalent lithostratigraphic units in the proximal and distal sectors of the Karoo Basin. Microfloras from previous South African studies are integrated within the proposed palynostratigraphic scheme, and palynological signatures of the various Karoo formations are shown to be consistent. Despite the constraints of floral provincialism, South African microfloras can be correlated to selected Gondwanan biozonations from Australia, Africa, Antarctica, New Zealand and South America. Future studies should focus on sampling more intensively over smaller stratigraphic intervals, which will assist in the correlation of time equivalent lithostratigraphic units in the different sectors of the basin, thus aiding in refinement of basin development models. Key words: palynology, Karoo, vertebrate biozones, stratigraphy, Gondwan

Bringing science communication skills into the university classroom and back out again: What do palaeoscience educators think?

University-level pedagogy and public science communication both have the same broad goal: to facilitate the sharing of knowledge and understanding from a specialist or expert, to a non-specialist group. Recent research has emphasised the need for there to be a two-way transfer or dialogue of ideas between these fields, but collaboration thus far is rare, particularly at the tertiary education level. Performing science outreach is mostly a voluntary service for academics, and institutions provide little in the way of support, training or recognition. Here I explore the potential for a positive feedback loop between science communication and higher-education pedagogy in the palaeosciences. A synthesis of best practises in science outreach is drawn from the literature and related to pedagogical concepts and findings. The resulting congruences suggest enormous potential for ‘cross-pollination' of ideas between the fields. However, in-depth one-on-one interviews and focus groups with palaeoscience educators, as well as an online survey, indicate that this potential remains largely untapped in the palaeosciences community. While respondents could identify certain skills as being integral to success in science communication, they did not appear to realise that the same skills, when applied in the classroom, could contribute towards key challenges in higher education today, including the stimulation of student engagement and motivation, the accommodation of an increasingly diverse student body, the anticipation of common student misconceptions in science, and the improvement of pedagogical models of delivery. Another emergent theme was that being a good science communicator was “much simpler” than being a good teacher, conflicting with evidence-based pedagogical and outreach research. While many palaeoscientists did express strong commitments to science communication, they had previous experience of time constraints and conflicts with other academic responsibilities. Therefore, both palaeoscientists and their institutions would benefit from viewing science communication as a valuable and formally rewardable activity within the scholarship of sharing knowledge, which also contributes to other aspects of a successful academic career.publishedVersio

MULTIPLE PALAEOECOLOGICAL PROXIES CONSTRAIN THE INTERPLAY BETWEEN TIBETAN PLATEAU GROWTH, THE PROTO-MONSOONS AND FLORAL DISPERSAL DURING THE EARLY INDIA-ASIA COLLISION

International audienceThe interplay between tectonics, monsoonal climate regimes, andbiodiversity of the Tibetan Plateau has been the recent focus ofmuch investigation. However, the linkages between orogeny andclimate, as well as their impacts on floral diversity, are still unclear.The Nangqian Basin of east-central Tibet holds a key Paleocene–Eocene record of deformation and environmental change duringthe early stage of the India-Asia collision, the development of theTibetan Plateau, and the proto-monsoons. Here, we examine newpalynoassemblages recovered from this basin and apply FourierTransform Infrared (FTIR) microspectroscopy to quantify ultravioletirradiance based on pollen chemistry, in combination with plantleaf wax biomarkers. Although the studied section was previouslyassigned a mid-Cretaceous age based on ostracods, this new palynologicalevidence combined with magnetostratigraphy rather indicatesa Paleogene age. Volcanic intrusives and extrusives crosscutthe lacustrine to alluvial Cenozoic Nangqian strata, providing aminimum age constraint at ca. 37 Ma. In the context of a proto-TibetanPlateau established early in the Cenozoic, the abundance ofhigh-altitude bisaccates from the Nangqian section is of particularinterest. It largely predates the spread of high-altitude elements tothe North in Central Asia from 36 Ma, and their diversification afterthe 34 Ma Eocene–Oligocene transition cooling. These observationsare in line with a growing body of evidence that parts of the TibetanPlateau had attained high elevations similar to modern conditionssoon after the India-Asia collision. The outward growth from this elevatedcentral part of the Tibetan Plateau, with associated effects onthe monsoons, is envisioned to have had major effects on dispersaland speciation of the Pinophyta across Asia during the Paleogene

Analysis of fossil plant cuticles using vibrational spectroscopy: A new preparation protocol

Analyses for organic “fingerprints” on fossilized plant cuticles and pollen hold valuable chemotaxonomic and palaeoclimatic information, and are thus becoming more utilized by palaeobotanists. Plant cuticle and pollen composition are generally analyzed after standard treatments with several chemical reagents for mineral and mesophyll removal. However, the potential alterations on the fossil composition caused by the different cleaning reagents used are still poorly understood. We tested the effects of commonly used palaeobotanical processing methods on the spectra of fossilized cuticles from successions of Late Triassic to Early Jurassic age, including the gymnosperms Lepidopteris, Ginkgoites, Podozamites, Ptilozamites and Pterophyllum astartense. Our study shows that standard chemical processing caused chemical alterations that might lead to erroneous interpretation of the infrared (IR) spectra. The difference in pH caused by HCl induces changes in the proportion between the two bands at ~1720 and 1600 cm 1 (carboxylate and C-C stretch of aromatic compounds) indicating that the band at ~1610 cm 1 at least partially corresponds to carboxylate instead of C-C stretch of aromatic compounds. Interestingly, despite being used in high concentration, HF did not cause changes in the chemical composition of the cuticles. The most alarming changes were caused by the use of Schulze ’s solution, which resulted in the addition of both NO2 and (O)NO2 compounds in the cuticle. Consequently, a new protocol using H2CO3, HF, and H2O2 for preparing fossil plant cuticles aimed for chemical analyses is proposed, which provides an effective substitute to the conventional methods. In particular, a less aggressive and more sustainable alternative to Schulze’s solution is shown to be hydrogen peroxide, which causes only minor alteration of the fossil cuticle ’s chemical composition. Future work should carefully follow protocols, having in mind the impacts of different solutions used to treat leaves and other palaeobotanical material such as palynomorphs with aims to enable the direct comparison of spectra obtained in different studies

Cooling, vegetation shift and decline in monsoonal rainfall in NE Tibet through the greenhouse to icehouse transition

International audienceUnderstanding how and why global climate tipped from greenhouse to icehouse conditions remains a major challenge.This critical shift is well documented in the marine realm characterized by a steady decline in global temperatureuntil a large and rapid cooling step at the Eocene-Oligocene Transition (EOT). However, the chronology andmechanisms of cooling on land remain unclear. To reconstruct Paleogene climate conditions for the Tibetan Plateauand the Asian continental interior, clumped isotope thermometry and palynology in accurately-dated continentalrecords from northeastern Tibet, are here combined with climate and vegetation simulations. Our results show twosuccessive dramatic (>9 C) drops in soil carbonate temperature, at 37 Ma and at 33.5 Ma associated respectivelywith the appearance and dominance of high altitude conifer forests. Such large temperature decreases associatedwith ecological reorganisations cannot result from regional cooling alone. They require shifting of the rainy seasonto cooler months, which we interpret to reflect a decline of monsoonal intensity. Our results suggest that theresponse of Asian temperatures, monsoonal rainfall and vegetation to the decline of atmospheric CO2 and globaltemperature through the late Eocene occurred in two steps separated by a period of climatic instability. Our resultssupport the onset of the Antarctic Circumpolar Current coeval to the Oligocene isotope event 1 (Oi-1) glaciationat 33.5 Ma, reshaping the distribution of surface heat worldwide; however, the origin of the 37 Ma cooling eventremains to be determined

Acute Asian cooling across the Eocene–Oligocene transition evidenced by ecosystem restructuring on the Tibetan Plateau

International audienceThe Eocene-Oligocene transition (EOT) represents a profound global climatic shift to a cool climate, but detailed environmental responses to this change are not yet well understood. High-resolution, well constrained terrestrial records spanning the EOT are comparatively rare, with most information deriving from the marine realm. Previous studies of Asian terrestrial ecosystems have employed pollen records as a powerful proxy for response to global climatic change in the Eocene. We present an updated and expanded Late Eocene palynological record for the Xining Basin on the northeastern margin of the Tibetan Plateau, that now extends into the lower Oligocene. Together with regionally significant high-resolution palaeoclimatic multi-proxy records, Early Oligocene palynological samples indicate profound ecosystem restructuring consistent with acute cooling and a possible increase in seasonality across Asian environments. Major vegetation turnover is linked to massive Antarctic ice sheet expansion during the EOT and thus suggests global climate may have modulated monsoonal systems driving Asian environmental change