En mellanjurassisk flora från Bagå-formationen, Bornholm

En samling växtfossil från Bagå-formationen, Bornholm, Danmark, har undersökts för att identifiera sammansättningen av floran samt tolka klimatet. Sedimenten som utgör Bagå-formationen deponerades under mellanjura mellan den danska bassängen och det polska tråget och består av lersten med mellanlagrande kolskikt. Depositionsmiljön har tolkats som ett meandrande flodsystem med stora torvbildande träskmarker i anslutning till flodområdet. Sedimenten innehåller mycket välbevarade avtryck och kompressioner av växter och materialet som ingår i denna studie insamlades av bl.a. Möller (1902) och materialet finns registrerat i samlingarna vid Geologiska institutionen vid Lunds universitet. Fossilen delades in i sju släkten varav bara två exemplar till artnivå. Den fossila floran domineras av ormbunkar men innehåller även Ginkgoales, barrträd, bennettiter och fräken. Jämförelser med likåldriga floror visar att sammansättningen i Bagåsamlingen liknar den jurassiska Eriksdalsfloran från Skåne. Juratiden var en varm och fuktig period och fem biom har identifierats globalt. Floran i denna studie tolkas som förekommande i ett varmtempererat biom (i ett varmt och fuktigt klimat). Prover av kutikula (det yttersta vaxartade lagret hos blad) härrörande från fossila barrtäd av arten Bilsdalea angustifolia från Bagå-formationen studerades med avseende på stomatadensitet för att utvärdera olika beräkningssätt och metoder för tolkning av temperatur och paleo-CO2 halter. Resultaten blev olika beroende på vilken del av bladet som räknades och i allmänhet gav resultaten låga koldioxidhalter. Mer omfattande studier krävs för att förbättra tekniken för användning av smalbladiga pre-angiosperma floror.A collection of plant fossils from the Bagå Formation, Bornholm, Denmark, has been investigated to identify the composition of the flora and interpret the climate. The sediments of the Bagå Formation were deposited during the Middle Jurassic between the Danish basin and the Polish through and consist of mudstone interbedded with coal seams. The depositional environment has been interpreted as a meandering fluvial system hosting extensive peatforming marshes in flood-basin areas. The sediments contain well-preserved plant impressions and compressions and the material investigated in this study was collected, among others, by Möller in 1902 and is registered in the collections at the Geological Department, Lund University. The fossils were assigned to seven plant genera but only two specimens were identified to species level. The fossil flora is dominated by ferns but also contains Ginkgoales, conifers, Bennettitales and Equisetales. Comparisons with coeval plant assemblages show that the flora from the Bagå Formation closely resembles that of Eriksdal, Skåne. The Jurassic was a warm and humid period and five biomes have been recognized across the globe. The flora studied herein is interpreted to have grown in the warm temperate biome (in i.e. a warm and humid climate). Additionally, samples of cuticle (the outer waxy coating of the leaf) derived from the conifer taxon Bilsdalea angustifolia from the Bagå Formation were studied to evaluate different methods for counting stomata used in the interpretation of palaeotemperature and the palaeo-CO2 levels. The results were different depending on which part of the leaf was analyzed and low palaeo-CO2 levels were generally documented using previous methods. More, extensive studies are required to refine this technique for use with predominantly narrow-leafed pre-angiosperm floras

Early land plant spores from the Paleozoic of Sweden – taxonomy, stratigraphy and paleoenvironments

The Silurian through earliest Devonian, between ca 444 and 412 million years ago, was characterized by significant changes in global climate and environment. At that time, plants and animals had begun to expand the colonization of previous relatively desolate terrestrial landscape. Macrofossils of land plants are very rare from this period because these early land plants lacked large and robust tissues that could be easily fossilized. The spores produced by these early land plants are, therefore, an important tool for resolving the establishment of the early vegetation on Earth. Spore walls are composed of sporopollenin, a complex mix of biopolymers incorporating long chains of fatty acids, phenolics, phenylpropanoids and traces of carotenoids that are, collectively, very resistant to desiccation, pressure and high temperatures. These properties make spores easily preserved as fossils in the sedimentary deposits. Fossil spores can be used as a tool to: study diversity of the terrestrial vegetation, date and correlate sedimentary successions (biostratigraphy), make paleoenvironmental and paleoclimatic interpretations and, finally, assess the potential for hydrocarbon (gas, oil and coal) generation in the sediments. During the Silurian, the paleocontinent Baltica, of which Sweden was a part, was covered by shallow seas. However, the study area in central and southern Skåne was not too distant from the coast. The sediments here were deposited in foreshore to shoreface environments with water depths no more than a few tens of meters, and in some areas, represented by Lower Devonian successions, possibly even in non-marine environments such as rivers and lakes. Spores from the early land plants were transported by river water into the shallow sea and sank to the bottom as they lost buoyancy. Today these spores from early land plants are preserved in the mid-Paleozoic sedimentary rocks exposed in present day Skåne and on Gotland. In this project, sedimentary rock samples obtained from drill cores and outcrop at several localities in Skåne and Gotland, were processed by acid dissolution techniques to recover assemblages of organic-walled palynomorphs – mainly plant spores, detrital organic material, and marine palynomorphs. These palynological assemblages were studied by light microscopy to determine the diversity of spore taxa through several short stratigraphic intervals at various sites. Many of the bore cores were drilled by the Swedish Geological Survey during the 1960s and have never been investigated for their fossil spore content. Overall, there have been very few studies of spores from the Silurian of the Baltic region and the knowledge about the composition of the early land floras from this part of the world is sparse. In this thesis, rich and well-preserved assemblages of early land plant spores are described from both drill core and outcrop samples from Skåne. Both cryptospores (produced by the earliest land plants) and trilete spores (produced by vascular plants) have been recovered. In total, 66 species of both cryptospores and trilete spores were identified in the upper Silurian and Lower Devonian successions of Skåne. These results reveal a rather diverse early terrestrial flora previously unrecognized in the region. Further, a revised stratigraphy for the Öved Sandstone Formation is presented as the c. upper 100 metres of the succession is based on palynostratigraphy of this study shown to represent Devonian strata. From the Burgsvik Formation, on Gotland, sediments coeval to the studied sections in Skåne, also yielded spores from early land plants. In these beds, the earliest land plant fossil with in situ cryptospores from Baltica was discovered. These remains consist of spore masses with part of the sporangium still preserved, a possible land plant axis, and also more poorly preserved spore masses interpreted to be coprolites (fossil feaces) from arthropods. This last category represents one of the earliest examples of plant-animal interactions globally. Further, this study reports the oldest evidence of land plants in Sweden. This is in the form of spores identified in Upper Ordovician sedimentary successions in drill core material from Röstånga, Skåne

The spore record of early land plants from upper Silurian strata in Klinta 1 well, Skåne, Sweden

Prover från Öved-Ramsåsagruppen i Skåne från övre Silur har undersökts palynologiskt, främst med avseende på sporer från landväxter. Sedimenten består av karbonater med silisiklastiskt innehåll och paleomiljön har tolkats till ett strandnära marint ekosystem. Detta har graderat från öppen marin, grund-subtidal till lagun eller intertidal miljö, vilket erbjuder en god möjlighet till palynologiska analyser av strandnära marina facies. 28 prover processades palynologiskt från borrkärnan Klinta borrhål 1. Sedimenten är marina, men material från landmiljö är representerat av sporer från tidiga landväxter. Denna studie visar en välbevarad palynologisk association dominerad av sporer från landväxter. Totalt 14 arter tillhörande 11 släkten av sporer identifierades, samt tre taxa som endast bestämdes till släktnivå. Den relativa förekomsten av sporer varierar i kärnan från 100 % ner till 0 % i vissa prover. Där sporförekomsten sjunker ökar generellt förekomsten av marina mikrofossil så som akritarker, skolecodonter och chitinozoer. Nivå 85 m i kärnan karakteriseras av total avsaknad av sporer och en hög andel ved, vilket tolkas bero på dåliga bevaringsförhållanden. Den höga andelen av sporer på vissa nivåer indikerar en strandnära, intertidal miljö. Förutom sporer från landväxter förekommer också vedrester och marina palynomorfer så som akritarker, chitinozoer och skolecodonter i proverna. Sedimenten har daterats med hjälp av sporerna till sen Silur (sen Ludlow; Ludfordian, ca. 420 miljoner år) med hjälp av följande nyckelarter; Emphanisporites negelctus, Hispanediscus verrucatus, Synorisporites cf. libycus och Apiculiretusispora? burgsvikensis. Dateringen baserad på sporer har korrelerats med nuvarande biostratigrafisk zonering, i sin tur baserad på conodonter, graptoliter och tentaculiter. Sporer ändrar färg med ökande begravningsdjup och detta har visat sig vara en bra metod för att tolka paleotemperatur och mognad i moderbergarter för kolväten. Denna studie påvisar ett ”Thermal alteration index” (TAI) på –3 och ett ”spore Color index” (SCI) på 7, vilket indikerar att det finns en möjlighet för kolväten att existera eftersom (TAI) är inom ”oljefönstret”.Samples from the upper Silurian Öved-Ramsåsa Group, Skåne, Sweden have been investigated palynologically. The sediments are dominated by siliciclastic deposits with minor carbonate units and the palaeoenvironmental setting has been interpreted as a near shore marine ecosystem which grade from open marine shallow subtidal to lagoonal intertidal conditions, offering a prime target for palynological analysis of near shore marine facies. A total of 28 samples were processed palynologically from the drill-core Klinta BH 1 and the terrestrial record is, in this marine setting, represented by spores of early land plants. The study has revealed a well preserved palynological assemblage dominated by spores from land plants. A total of 14 spore species belonging to 11 genera were identified and additionally three taxa were identified to genus level. The high percentage of spores at some levels signifies a near-shore, intertidal environment. Apart from spores, wood remains and marine palynomorphs, such as acritarchs, are present in the palynological assemblages. The relative abundance of spores varies throughout the core, from abundances as high as 100% down to 0% in some samples. A decrease of relative spore abundance is generally met by an increase in marine microfossils such as acritarchs, scolecodonts and chitinozoans. The sediments at the level 85 m in the core, are characterized by a lack of spores and instead a high abundance of wood, which possibly indicates poor conditions of preservation. Palynostratigraphy based on the identified spores indicate that the studied sediments are of a late Ludlowian (Ludfordian) age (420 Ma) based on the presence of the following key-species; Emphanisporites negelctus, Hispanediscus verrucatus, Synorisporites cf. libycus and Apiculiretusispora? burgsvikensis. The spore zonation has subsequently been correlated with the existing biostratigraphical scheme based on conodonts, graptolites and tentaculitids. Spores change in colour with increasing depth of burial and this has shown to be a widely applicable method for thermal maturity determination in hydrocarbon source rocks. This study shows a maturity index of -3 (TAI) and 7 (SCI). Indicating that hydrocarbon presence is potentially possible as the Thermal Alteration Index (TAI) is within the “oil window”

The dawn of terrestrial ecosystems on Baltica: First report on land plant remains and arthropod coprolites from the Upper Silurian of Gotland, Sweden

Abstract in UndeterminedSporangia, with their in situ cryptospores, spore masses, and a possible axis were identified in marginal marine Ludlovian deposits from Gotland. Sweden by means of light- and scanning electron microscopy.The sporangia identified are elongate, with fragments of the sporangia covering preserved, and contain well-preserved in situ embryophyte cryptospores identified as Laevolancis divellomedia (monad) and Dyadospora murusdensa (dyad). A single detached axis was identified possessing superficial longitudinal striations resembling epidermal cell patterning. The axis ends in a cup-shaped structure that possibly represents the basal part of a sporangium. masses of cryptospore monads shrouded in amorphous organic material, most probably representing coprolites of terrestrial arthropods, were found in the same beds. The spores in these masses are degraded in sharp contrast to the excellent preservation of the dispersed and sporangia-hosted spores. The monad, L divellomedia, a common local constituent of the dispersed microflora, was identified in the coprolites. This is the first report of undisputed Silurian land plant remains in Baltica and the study reveals one of the earliest examples of arthropod-plant interactions

A Jurassic (Pliensbachian) flora from Bornholm, Denmark - a study of a historic plant-fossil collection at Lund University, Sweden

A historic collection of plant fossils from the Baga Formation, Bornholm, Denmark registered at the Lund University is reviewed and found to be dominated by ferns with subsidiary Ginkgoales, Coniferales, Bennettitales and Equisitales. Ten genera are represented, of which six can be confidently identified to species level. The Baga Formation flora is most similar in age to the flora of the Middle Jurassic Mariedals Formation of Eriksdal, Skane, although there are important compositional differences between these assemblages. The Baga flora is characteristic of the temperate (warm and humid) biome of the Early-mid Jurassic. A historical investigation reveals that at least four scientists contributed material to the collections. A palynological investigation made on samples from the leaf fossils reveals that the macroflora was most probably collected from the Sorthat beds as the palynoflora corresponds to the Pliensbachian Chasmatosporites Zone

Linking upper Silurian terrestrial and marine successions—Palynologicalstudy from Skåne, Sweden

We have performed a palynostratigraphic study on miospore assemblages from near-shore marine Silurian sed-imentary rocks of Skåne, southern Sweden. The material includes both drillcore (from Klintaborrningen 1 and Bjärsjölagårdborrningen 2) and outcrop samples from various localities in Skåne. Well- preserved spore assemblages were identified. Long ranging species with a global distribution dominate the spore assemblages, including Ambitisporites sp., Dyadospora sp., Laevolancis sp., and Tetrahedraletes sp. and complemented with key taxa including Emphanisporites neglectus, Hispanaediscus lamontii, Hispanaediscus verrucatus, Scylaspora scripta, Synorisporites libycus and Synorisporites tripapillatus. Based on biostratigraphical schemes for early land plant spores, the studied sedimentary rocks of the cores Klintaborrningen 1 and Bjärsjölagårdborrningen 2 are interpreted as late Silurian in age, spanning Ludlow to Přídolí. The spore assemblages are compared and correlated to marine fossil schemes including those of conodonts, chitinozoans, graptolites and tentaculitids. Additionally, relative abundance data of specific spore taxa have been used for correlation between the drillcores and the outcrops

First evidence of Devonian strata in Sweden — A palynological investigation of Övedskloster drillcores 1 and 2, Skåne, Sweden

Palynological analyses were carried out on 50 samples from the Övedskloster 1 (Ö1) and 2 drillcores (Ö2), southern Sweden. The study revealed well-preserved palynological assemblages including 77 spore species in 28 genera, and some additional forms retained under open nomenclature. The spore assemblages are collectively dominated by trilete spores in terms of abundance and diversity and have been ascribed to two informal palynozones (Assemblage A and Assemblage B), based on the representation of spore taxa. The presence of the spore species Acinosporites salopiensis, Chelinohilates erraticus, Cymbohilates allenii, Cymbohilates allenii var. magnus, and Retusotriletes maccullockii indicates that the stratigraphic succession spans the Silurian–Devonian boundary (Přídolí–Lochkovian), and thus constitutes the first robust evidence of Devonian strata on the Swedish mainland. These results have implications for the age of fossil faunas (e.g. fish) from the samedeposits, previously dated as late Silurian. Palynofacies analyses reveal a shallowing-upward succession with nearshore marine marls at the base of the investigated core, grading into sandstones in conjunction with a decrease in the relative abundance of marine palynomorphs. The uppermost 70 m are mainly represented by red sandstones that are devoid of recognizable palynomorphs and host only phytodebris. We interpret this interval to represent predominantly paralic to fluvial deposits equivalent to facies represented in the Old Red Sandstone of Britain

Late Ordovician (Katian) spores in Sweden: oldest land plant remains from Baltica

A palynological study of the Ordovician–Silurian boundary (Katian–Rhuddanian) succession in the Röstaånga-1 drillcore, southern Sweden, has been performed. The lithology is dominated by mudstone and graptolitic shale, with subordinate limestone, formed in the deeper marine halo of southernBaltica. The palynological assemblages are dominated by marine microfossils, mainly chitinozoans and acritarchs. Sparse but well-preserved cryptospores, including Tetrahedraletes medinensis, Tetrahedraletes grayii and Pseudodyadospora sp., were encountered in the Lindegård Formation (late Katian–early Hirnantian), with the oldest record just above the first appearance of the graptolite species Dicellograptus complanatus. This represents the earliest record of early land plant spores from Sweden and possibly also from Baltica and implies that land plants had migrated to the palaeocontinent Baltica by at least the Late Ordovician

A palynological study from Sweden reveals stable terrestrial environments during Late Silurian extreme marine conditions

A palynological study of the upper Silurian Öved–Ramsåsa Group in Skåne, Sweden yields a well preserved spore assemblage with low relative abundances of marine microfossils. In total, 26 spore taxa represented by 15 genera were identified. The spore assemblage is dominated by long-ranging cryptospore taxa, and the trilete spore Ambitisporites avitus-dilutus. However, key-species identified include Artemopyra radiata, Hispanaediscus lamontii, H. major, H. verrucatus, Scylaspora scripta and Synorisporites cf. libycus. Importantly, Scylaspora klintaensis was identified, allowing correlation with the Klinta 1 drillcore (Skåne). A Ludlow age is inferred for the exposed succession, which agrees well with previous conodont stratigraphy. The organic residue is dominated by phytodebris and spores, but with high relative abundances of acritarchs at two levels, possibly related to flooding surfaces. Based on the palynofacies analysis, a near-shore marine environment is proposed. The close proximity to land is inferred by the high proportions of spores, and the dispersed assemblage most likely represents the local flora growing on delta plains. The palynological signal also infers a stable terrestrial environment and vegetation, in contrast to unstable conditions in the marine environment characterised by ooid formation in an evaporitic environment. Comparisons with coeval spore assemblages from Gotland, Avalonia and Laurentia show relatively close similarities in taxonomic composition at the generic level