Search

The lower Toarcian black shale and mudstone succession of the Anya section in the northeastern Ordos Basin records a climatically controlled evolution of the lacustrine system during the negative carbon isotope excursion (NCIE) of the Toarcian oceanic anoxic event (T-OAE ; ca. 183 Ma). In the Anya section, petrography integrated with climate proxies (Sr/Cu and Rb/Sr) and weathering indices (weathering index of Parker, chemical index of weathering and plagioclase index of alteration), suggests that a warm-humid climate with sporadic semihumid-semiarid intervals developed during the early Toarcian and was coincident with strong chemical weathering. Sr/Ba and S/TOC ratios suggest that the Anya section's rocks were generally deposited in freshwater. Four phases (phases A, B, C and D) in lake evolution are distinguished from the variation in petrographical and geochemical proxies providing clues about the drivers of environmental change and organic matter accumulation in the lacustrine basin. Phases A and C have a high preservation of organic matter derived from lake plankton (Type II-III kerogens), were characterized by anoxia, and coincided with high primary productivity. On the contrary, phases B and D indicate a low primary productivity and suboxic-oxic conditions, with a lower organic matter content of predominantly higher land plant origin (Type III kerogen). The accumulation of organic matter was mainly controlled by changes in primary productivity and redox conditions that were tightly linked to the local sedimentary evolution of the Ordos Basin and to global and regional climate. During the early Toarcian NCIE, the accumulation of organic-poor sediment and terrestrial organic matter may have been driven by enhanced seasonality, superimposing on local lake level changes. As a consequence, the peak of the T-OAE carbon cycle perturbation does not coincide with lacustrine black shale deposition and/or peak anoxia in this continental depositional system. This emphasizes the significance of local or regional environmental change on the carbon sequestration within lacustrine systems.

The Early Jurassic Toarcian oceanic anoxic event (T-OAE, ca. 183 Ma) was accompanied by a major biotic turnover in the oceans and substantial vegetation change on land. The marine biotic crisis has been attributed to several triggers, e.g., anoxia, warming, ocean acidification, yet the processes underlying the collapse of the terrestrial ecosystem are poorly understood. New high-resolution geochemical and palynological data across the T-OAE from a lacustrine succession in North China reveal elevated occurrences of spore dwarfism, asymmetrical Classopollis tetrads, and aberrant spores coeval with increases in heavy metal (Hg, Cu, Cr, Cd, Pb, As) abundances. The occurrence of teratological spores and pollen in multiple plant groups suggests overall vegetation-scale ecological pressure. Our data indicate that the combination of a widespread floral crisis with higher terrestrial organic matter oxidation and decomposition, enhanced hydrological cycle, and coeval large-scale volcanism resulted in higher concentrations of toxic heavy metals in terrestrial ecosystems. These heavy metals could poison plants, causing mutations and disrupting their reproductive cycle, and making them more vulnerable to secondary stresses such as climatic extremes and/or habitat shifts, eventually leading to widespread collapse across all terrestrial trophic levels.

The marine system of the Mediterranean-Paratethys region in the Middle Miocene was influenced by the global climatic changes corresponding to the Miocene Climate Optimum. The latter was characterized by global warming of deep oceanic waters succeeded by a decrease of wind activity and ocean water circulation together with a decline in oceanic productivity. This study provides a detailed paleoenvironmental and depositional history of the Middle Miocene deposits from Mt. Požeška Gora (the east part of Croatia). Stable carbon and oxygen isotope data with foraminiferal fauna coupled together with palynological data indicate both seasonal and long-term changes in surface water temperatures, nutrient contents, and salinity. Furthermore, it was possible to determine two phases of Middle Miocene flooding in the studied marine system: (a) a shallow, high nutrient marginal sea strongly affected by freshwater inputs corresponding to the thermal maximum and periods with enhanced precipitation during the Miocene Climate Optimum, and (b) a younger deeper marginal sea with a developed seasonal stratification, rather intermediate nutrient availability and reduced fresh-water inputs. Based on the microbiostratigraphy and strontium isotope stratigraphy (87Sr/86Sr) coupled with previously published high-precision geochronology, the timing of the first and second flooding can be correlated with the Langhian age - ≤15.4 Ma and 14.6 Ma, respectively Possibly, the properties of the surficial waters that were described as a part of the flooding phases in individual time intervals can indicate changes in circulation patterns as a result of potential influence of the open-sea water masses.

The Toarcian Oceanic Anoxic Event (T-OAE, ∼183 Ma) was marked by a pronounced negative carbon- isotope excursion, rapid global warming, ocean deoxygenation, and turnover of marine and terrestrial biota. The T-OAE has been linked to carbon (C) release from volcanism, but the mechanisms controlling the cycling of C, metals, and nutrients during the event are still not fully understood. Here we show that lacustrine strata (Anya section) through the T-OAE in the Ordos Basin (China) record large increases in Hg/TOC (up to 453 ppb/wt.% relative to a background of 23 ppb/wt.%), which are coincident with the sudden demise of spore producing plants and seed ferns and the acme of Classopollis pollen of the thermophilic Cheirolepidiaceae conifers. These changes occurred during the peak of the negative carbon-isotope excursion that marks the T-OAE in the Anya section. Hg-isotopes are a useful proxy for recognizing changes in Hg sources and fluxes (notably from atmospheric deposition and terrestrial biomass) in sediments and sedimentary rocks. The negative Hg and Hg throughout the Anya section are consistent with a constant terrestrial Hg source in the studied interval. Hence, the recorded Hg enrichment suggests that terrestrial Hg loading increased during the T-OAE. Coupled with evidence for a large increase in hydrological cycling, weathering and runoff, our data indicate that the T-OAE floral crisis was associated with a massive release of terrestrial Hg to oceanic and terrestrial ecosystems. This work provides new insights into the links between toxic metal cycling and mass extinction during times of large- scale volcanism.

In the early Late Triassic, the Carnian Pluvial Episode (CPE) is a phase with increased siliciclastic influx into the marine-carbonate dominated depositional setting of the Western Tethys assumingly caused by a shift to more humid climatic conditions and increased continental runoff. Here, vegetation changes inferred from the palynological assemblages and weathering proxies (αAli) have been studied from the Transdanubian Range (TR), western Hungary to reveal climate variations and detect episodes with hygrophytic vegetation and enhanced continental hydrolysis. Palynostratigraphy has been applied to correlate the clastic pulses known from elsewhere in the Western Tethys. The quantitative palynological analysis indicates a shift towards hygrophytic elements in the Julian 2, and return to xerophytic associations in the Tuvalian. The increase in the hygrophytic vegetation elements is coincident with elevated kaolinite and partially with the increase of α-values indicating strong terrestrial runoff, enhanced continental hydrolysis and more humid climate in the lower part of the Veszprem Formation in the early Julian 2. The wetter conditions in the Julian 2 were periodically interrupted by shorter periods of drier climate manifested in the progradation of carbonate platforms and the deposition of carbonate series and breccias interbedded between the marl units. In the late Julian 2 the high amount of hygrophytes points to another humid episode, but the decrease of kaolinite in the clay mineral profile and the weathering indices might suggest stronger seasonality. Although, the multiple clastic pulses in the western Tethys were related primarily to more humid climate during the CPE, the comparison to clay mineralogy and weathering proxies suggest a more complicated scenario in the TR. The enhanced continental weathering related to a more humid climate is only suggested for the lower part of the Veszprem Formation in the early stages of the CPE in the Julian 2.

The Yanchang Formation was deposited during the Middle Triassic in a vast lacustrine basin in the modern Ordos Basin and is a main target for hydrocarbon exploration in Central China. It is divided, based on sedimentary cycles and lithology, into the Chang 10 (the oldest) to Chang 1 (the youngest) members. During the deposition of the Chang 7 Member, the Ordos lake system reached its maximum depth and large volumes of organic-rich sediments were deposited. The evolution of the Ordos Basin sedimentary system during this phase is, however, not completely understood, and uncertainty still exists as for the chronostratigraphy of Chang 7 Member. We acquired palynological markers and palynofacies and a high-resolution δ13Corg record through the entire Chang 7 Member, and a ID-TIMS 206Pb/238U date of 240.95 ± 0.033 Ma from a volcanic ash bed in the middle of this Member. These imply that the maximum deepening phase of the lacustrine system was during the earliest Ladinian. Evidence of marine influence in the Ordos Basin at that time and comparison to the sea-level oscillations observed in Western Tethys suggest that a global eustatic rise and highstand may have played a role in determining lake-level variations.

New palynological data from the deep-water Gușterița section in the Transylvanian Basin depict the late Miocene evolution of Lake Pannon between 11.0 and 10.5 Ma. Spores and pollen were used to analyze vegetation and climate while dinoflagellate cysts were used to reconstruct lake ecology. The section hosts primarily endemic brackish-water dinoflagellate cysts related to those in the Ponto-Caspian realm. The lake was fringed by swamps of taxodioid gymnosperms and riparian forests. The proximity of the Carpathians and Apuseni Mts. allowed the presence of montane vegetation with Picea and Abies. The azonal vegetation narrowed down the extent of the zonal mesophytic forests. Plants were growing under warm-temperate, humid climate with mean annual temperature of 13.3–21.3 °C and mean annual precipitation of 705–1613 mm. The decline of the thermophilous Taxodioideae is linked to the uplift of the mountains and volcanism, but the expansion of Lake Pannon contributed to the swamp-retreat too. The lake expansion was stepwise with the alternation of minor floodings and stabilization of the lake-level. This pattern is inferred from the oscillation of “Virgodinium”-dominated dinoflagellate cyst assemblages characteristic of transgressive periods and assemblages with Spiniferites indicating the slowing-down of the flooding and higher nutrient input from rivers. Active sediment transport into the deep basin via turbidity currents is inferred by the large amount of plant debris in the sedimentary organic matter. The introduction of new dinoflagellate cyst morphotypes with more pronounced ornamentation and thicker wall is possibly a phenotypic response of the dinoflagellates to increasing freshwater influence.

The biota of the brackish-water Lake Pannon in the Pannonian Basin is characterised by remarkable endemism due to the isolated evolution of the lake for 8 myr after the last Miocene marine connection ceased (∼11.6 Ma). A conspicuous feature of this endemism is the large, probably ecophenotypic variation in the morphology of brackish-water dinoflagellate cysts that challenges taxonomy and complicates biostratigraphical and ecological interpretations. We conclude that a widely debated Lake Pannon genus, Pontiadinium, includes several proximate dinoflagellate cyst species with prominent apical and antapical protuberances, and we show how the genus differs from the morphologically similar gonyaulacacean cyst genera Impagidinium, Leptodinium, Cribroperidinium and Komewuia. The generic description of Pontiadinium is emended together with the species descriptions of Pontiadinium inequicornutum, Pontiadinium obesum and Pontiadinium pecsvaradanesis. A new species is described as Pontiadinium szentaiae sp. nov. from Našice (northern Croatia) that is characterised by unique trabeculate sutural septa formed from a beaded tegillum supported by columellae or rod-like luxuriae. The dinoflagellate cyst assemblages of the long-lived brackish-water Lake Pannon clearly demonstrate that dinoflagellate cysts in low-salinity, isolated epicontinental seas display greater morphological plasticity than their normal-marine relatives. The development of an antapical horn appears to be a previously undocumented example of phenotypic morphological features that developed in response to subnormal salinities within at least two dinoflagellate cyst genera endemic to Lake Pannon and the Post-Paratethyan seas of the Ponto-Caspian realm. This ecophenotypic variation resulted in a higher level of morphological adaptation, leading to the evolutionary development of new dinoflagellate cyst species and genera.

Fossil plant assemblages including spores and pollen grains provide useful information on past ecosystems and the response of terrestrial biotas to various environmental perturbations. New quantitative palynological data from the Chinle Formation of the American Southwest suggest that a floral turnover occurred in the middle Norian (between 217 and 213 Ma). Analysis of plant communities reveals that this turnover was followed by a complete reorganization of the riparian vegetation, driven by changes in fluvial styles and the tectonic regime of the basin, as well as a gradual transition toward a more arid climate. Marked increases in Klausipollenites gouldii, Patinasporites spp., and Froelichsporites traversei are probable indicators of environmental stress, such as increased aridity, perturbations of atmospheric pCO2, acid rain, and atmospheric aerosol accumulation due to volcanism in connection with the Pangean rifting and uplift of the Cordilleran arc. Comparison of the vegetation turnover with younger assemblages from the Chinle Formation in New Mexico revealed similar floral turnover patterns, suggesting two distinct drier periods as a result of multiple climatic oscillations. The climate-induced floral turnover may have contributed to the vertebrate faunal turnover as the loss of wetland habitat space and an increase in xerophytic plants may have dwindled the supply of palatable vegetation for herbivores. The onset of the floral turnover in Arizona roughly corresponds to the Manicouagan impact event, but a direct causal link is still speculative.

The early Toarcian (Early Jurassic) Oceanic Anoxic Event (T-OAE) or Jenkyns Event (~183 Ma) was marked by a globally synchronous negative carbon-isotope excursion, large-scale organic carbon burial and widespread oxygen depletion in the oceans. These features have been associated with volcanic activity of the Karoo and Ferrar large igneous provinces. The Jenkyns Event is well investigated in the Tethyan Ocean, but its expression in continental settings outside of Europe are still poorly understood. Here, the lacustrine Anya (AY) section in the NE Ordos Basin, North China, is studied for carbon-isotope geochemistry and palynology. Palynostratigraphy constrains the age of the section to the Pliensbachian-Toarcian transition, and a positive trend in δ13C, interrupted by a pronounced negative carbon-isotope excursion, has been identified in bulk organic matter and long-chain n-alkanes. The negative excursion is the expression of the Jenkyns Event, and coincides with variable total organic carbon (TOC) content in lake sediments. The maximum TOC (~21.5%) values precede the most negative carbon isotopes. A turnover from spore and seed fern-dominated palynological assemblages to Classopollis superabundance is coincident with the isotopic excursion and indicates clearly environmental perturbation. Biomarker data suggest that the organic matter was mainly sourced from higher plants. The magnitude of the Toarcian excursion in the bulk organic matter of this section (~ − 12.5‰) is much larger compared to that typically observed in marine and lake strata. Humidity-related fractionation effects in land plants and changes in plant groups might have contributed to the recorded magnitude. This magnitude is also larger than that of other terrestrial records, and casts doubt on the use of terrestrial C-isotope data to constrain deep time pCO2. Nevertheless, our findings show that the Jenkyns Event is well-recorded in lacustrine facies of the Ordos Basin.

The data presented in this article are related to the research article “Palynology and weathering proxies reveal climatic fluctuations during the Carnian Pluvial Episode (CPE) (Late Triassic) from marine successions in the Transdanubian Range (western Hungary)” (Baranyi et al., 2019). Palynological and palynofacies counts and mineralogical data are presented that build the core for the palaeoenvironmental and palaeoclimatic interpretation discussed in the original research article. Other component of this data article is the description of the applied laboratory and analytical techniques. We also supply microscopic images of the identified pollen and spores and a list of all identified palynomorphs.

The Neogene Transylvanian Basin (TB), enclosed between the eastern and southern Carpathians and the Apuseni Mountains in Romania, is a significant natural gas province with a long production history. In order to improve the (bio) stratigraphic resolution, correlations and dating in the several 100-m-thick upper Miocene (Pannonian) succession of the basin, the largest and most fossiliferous outcrop at Guşteriţa (northeastern part of Sibiu) was investigated and set as a reference section for the Congeria banatica zone in the entire TB. Grey, laminated and massive silty marl, deposited in the deep-water environment of Lake Pannon, was exposed in the ~55-m-high outcrop. The uppermost 25 m of the section was sampled in high resolution (sampling per metres) for macro- and microfossils, including palynology; for authigenic 10Be/9Be dating and for magnetostratigraphy; in addition, macrofossils and samples for authigenic 10Be/9Be isotopic measurements were collected from the lower part of the section as well. The studied sedimentary record belongs to the profundal C. banatica mollusc assemblage zone. The upper 25 m can be correlated to the Hemicytheria tenuistriata and Propontoniella candeo ostracod biozones, the uppermost part of the Spiniferites oblongus, the entire Pontiadinium pecsvaradense and the lowermost part of the Spiniferites hennersdorfensis organic-walled microplankton zones. All samples contained endemic Pannonian calcareous nannofossils, representing the Noelaerhabdus bozinovicae zone. Nine samples were analysed for authigenic 10Be/9Be isotopic measurements. The calculated age data of six samples provided a weighted mean value of 10.42 ± 0.39 Ma. However, three samples within the section exhibited higher isotopic ratios and yielded younger apparent ages. A nearly twofold change in the initial 10Be/9Be ratio is a possible reason for the higher measured isotopic ratios of these samples. Magnetostratigraphic samples showed normal polarity for the entire upper part of the outcrop and can be correlated with the C5n.2n polarity chron (11.056–9.984 Ma, ATNTS2012), which is in agreement with the biostratigraphic data. Based on these newly obtained data and correlation of the biozones with other parts of the Pannonian Basin System, the Guşteriţa section represents the ~ 11.0–10.5 Ma interval, and it is a key section for correlation of mollusc, ostracod, dinoflagellate and calcareous nannoplankton biostratigraphic records within this time interval.

Marked climate warming during the early Toarcian oceanic anoxic event (T-OAE, ~182 Ma) has been shown to have had a significant effect on the global carbon cycle and biosphere. There is also emerging evidence that a primary short-term consequence of this warming was a marked increase in hydrological cycling. In this study, we have investigated local environmental responses to T-OAE climate change by conducting a palynofacies analysis through an expanded Panthalassic margin record of the event exposed in southwestern Japan (Nishinakayama Formation, Toyora area). Palynomorphs are poorly preserved and rare in the studied interval. A pronounced increase in terrestrial phytoclast abundance coeval with the peak of the T-OAE can be linked to increased fluvial supply driven by enhanced hydrological cycling that occurred in response to early Toarcian warming. Broader scale trends in phytoclast abundance through the studied interval may be linked to longer-term sea-level changes. Nitrogen-isotopes, commonly used to elucidate basin redox changes, are found to correlate with changes in the relative abundance of phytoclasts. In contrast, carbon-isotope data are probably not significantly influenced by changes in organic matter type through the succession. However, thermal maturity indicators demonstrate that the succession is overmature, and this likely suppresses the magnitude of the well-known T-OAE carbon-isotope excursion in this succession.

The generally arid Late Triassic climate was interrupted by a wet phase during the mid-Carnian termed the Carnian Pluvial Episode (CPE). Quantitative palynological data from the Mercia Mudstone Group in the Wessex Basin (UK) reveal vegetation changes and palaeoclimate trends. Palynostratigraphy and bulk organic carbon isotope data allow correlation to other Carnian successions. The palynostratigraphy indicates that the Dunscombe Mudstone is Julian and the lowest part of the overlying Branscombe Mudstone Formation is Tuvalian. The Aulisporites acme characterizing the CPE in Tethyan successions and the Germanic Basin is missing in the UK. The quantitative palynological record suggests the predominance of xerophyte floral elements with a few horizons of increased hygrophytes. A humidity signal is not seen owing to the dry climate in central Pangea. Also, the signal might be masked by the overrepresentation of xerophyte regional pollen and the predominance of xerophyte hinterland flora. The bias towards regional pollen rain is enhanced by the potential increase in continental runoff related to seasonally humid conditions and differences in pollen production rates and transport mechanisms. The vegetation of British CPE successions suggests a more complex climate history during the Carnian, indicating that the CPE is not recognized by the same changes everywhere. Supplementary material: A detailed lithological log of the Strangman9s Cove (Devon) outcrop with the description of the Mercia Mudstone Group lithostratigraphical units, a description of the laboratory techniques, seven photoplates with selected spores and pollen grains, a list of all identified palynomorphs, Excel sheets with the palynological and palynofacies counts, bulk organic carbon isotope ratios and total organic carbon values of the Strangman9s Cove outcrop are available at https://doi.org/10.6084/m9.figshare.c.4138085

The development of high‐resolution 3D seismic cubes has permitted recognition of variable subvolcanic features mostly located in passive continental margins. Our study area is situated in a different tectonic setting, in the extensional Pannonian Basin system (central Europe) where the lithospheric extension was associated with a wide variety of magmatic suites during the Miocene. Our primary objective is to map the buried magmatic bodies, to better understand the temporal and spatial variation in the style of magmatism and emplacement mechanism within the first order Mid‐Hungarian Fault Zone (MHFZ) along which the substantial Miocene displacement took place. The combination of seismic, borehole and log data interpretation enabled us to delineate various previously unknown subvolcanic‐volcanic features. In addition, a new approach of neural network analysis on log data was applied to detect and quantitatively characterise hydrothermal mounds that are hard to interpret solely from seismic data. The volcanic activity started in the Middle Miocene and induced the development of extrusive volcanic mounds south of the NE‐SW trending, continuous strike‐slip fault zone (Hajdu Fault Zone). In the earliest Late Miocene (11.6–9.78 Ma), the style of magmatic activity changed resulting in emplacement of intrusions and development of hydrothermal mounds. Sill emplacement occurred from south‐east to north‐west based on primary flow‐emplacement structures. The time of sill emplacement and the development of hydrothermal mounds can be bracketed by onlapped forced folds and mounds. This time coincided with the acceleration of sedimentation producing poorly consolidated, water‐saturated sediments preventing magma from flowing to the paleosurface. The change in extensional direction resulted in change in fault pattern, thus the formerly continuous basin‐bounding strike‐slip fault became segmented which could facilitate the magma flow toward the basin centre.

Premise of research. Froelichsporites traversei is a prominent palynomorph in the Upper Triassic of North America that always occurs in tetrahedral permanent tetrads. It is an important regional biostratigraphic marker in the Norian of North America, and its abundance rises around 215 Ma, associated with a significant floral and faunal turnover. Its most striking morphological features are one well-developed distal pore (ulcus) on each grain and the annulus-like exine thickening around them. Previous works suggested that it was produced by spore-producing plants or Cheirolepidiaceae, but its botanical affinity is still unclear. Methodology. The wall ultrastructure of F. traversei was analyzed by TEM in order to reveal more information on the botanical affinity of the palynomorph. Pivotal results. The sporoderm consists of two layers and an inner faint discontinuous lamination. The outermost exine layer has a homogeneous texture (tectum), while the inner layer has a granular texture (infratectum). The laminae below the granular layer are not continuous but directly contiguous with the granules. Conclusions. The ultrastructure studies have ambiguous results, and the botanical affinity could not be revealed with certainty. It represents most likely a gymnosperm. The sporoderm layers indicate full development, and F. traversei was most likely dispersed as permanent tetrads at maturity. The ulcus might represent a germinal aperture or a rehydration pore similar to Cupressaceae pollen. The permanent tetrads may be related to polyembryony or polyploidy, and they probably provided an adaptive advantage to the parent plant.

Froelichsporites traversei (Dunay & Fisher) Litwin, Smoot, Weems is a prominent palynomorph in the Upper Triassic of Northern America which is permanently found in tetrahedral tetrads. The distribution of the taxon seems to be restricted to the Upper Triassic of North America. It is an important biostratigraphic marker in the Norian and a rise in its abundance around 215 Ma is associated with a significant faunal and floral turnover. Its most striking morphological features are the well- developed pores (ulci) and exine thickening around them on the distal side of each grain. Previous works suggested it was produced by spore producing plants e.g. sphenopsids, or Cheirolepidiaceae. Alternatively, it may represent a prepollen, but its botanical affinity is still unclear. We present preliminary results of a detailed morphological analysis (light microscopy and SEM) of newly collected outcrop material from the Chinle Formation at the Petrified Forest National Park (Arizona, USA). TEM analysis was applied to study the wall ultrastructure which may reveal more information on the botanical affinity of this peculiar palynomorph. The ultrastructure analysis revealed that it has a unique, simple wall structure consisting of only two layers. The outer layer is an electron dense layer with homogenous texture, while the inner layer has spongy-granular texture. A layer with lamination was lacking. The simple wall structure might point to an affinity to spore producing plants (possibly ferns, or bryophytes related the Andreaopsida ; a group of mosses). However, the distal pores and the occurrence exclusively as permanent tetrads would suggest an affinity with seed plants. An explanation for the lack of the laminated layer and nexine is that it might represent an immature pollen grain with gnetalean affinity in the early stage of tetrad formation, where the nexine is not developed yet. Alternative solution of the unusual morphological and ultrastructural features is that they represent experimentation with angiosperm related features and functions, which often characterize Bennettitalean plants in the Late Triassic.

Major palaeoenvironmental and palaeoceanographical changes occurred during the Early Jurassic Toarcian Oceanic Anoxic Event (T-OAE), due to a perturbation of the global carbon cycle and a crisis in marine ecosystems. The sequence of environmental change and regional differences during the T- OAE are not yet fully understood and organic-walled phytoplankton and other palynomorphs are well-suited, but under-utilised, in research into this event. Based on quantitative palynological analyses from a black shale- bearing succession at Réka Valley in the Mecsek Mountains of southwest Hungary, five sequential palynomorph assemblages are distinguished. These reveal major shifts in organic-walled phytoplankton communities, driven by palaeoenvironmental changes. In addition, palynofacies analysis helped to document changes in the composition of sedimentary organic matter, and to quantify the terrestrial input. Assemblage 1 is characterised by a moderately diverse phytoplankton community and high levels of terrestrial palynomorphs. Assemblage 2 records a significant peak of the euryhaline dinoflagellate cyst Nannoceratopsis. Assemblage 3 is distinguished by dominance of highly opportunistic prasinophytes and the temporary disappearance of all dinoflagellate cyst taxa. Assemblages 4 and 5 represent distinctive phases of a prolonged recovery phase with low diversity phytoplankton assemblages and intermittently high levels of terrestrially-derived palynomorphs. The successive disappearance of phytoplankton taxa and the gradual takeover by opportunistic euryhaline species at the onset of the T-OAE were related to several phenomena. These include reduced salinity in the surface waters, establishment of a stable pycnocline and deterioration of nutrient recycling, followed by oxygen deficiency throughout much of the water column. The high amount of terrestrially-derived palynodebris indicates intense runoff and freshwater input, driven by the early Toarcian warming and the enhanced hydrological cycle. Comparison with coeval European successions proves that the palaeoenvironmental changes during the T-OAE were not entirely synchronous, and local factors played a crucial role in influencing phytoplankton communities. In the Mecsek Basin, regional freshening of the surface waters and increased terrestrial input due to the proximity of the hinterland had a greater influence on phytoplankton communities compared to the open oceanic setting of the Tethys to the south.

This paper presents the results of a mineralogical, petrographic and palynological study of selected Pannonian calcareous marl and sandstone samples penetrated by the Hodmezővasarhely–I (Hod–I) well, Endrőd Formation (Totkomlos Member, cores 35 and 40, 5167.0–5183.0 m and 5468.0–5486.0 m, respectively); this formation is part of the Mako Trough of the Pannonian Basin, SE Hungary. The studied sections comprise mixed carbonate-siliciclastic rocks with abundant silt- to sand-sized angular grains such as monocrystalline and polycrystalline quartz, muscovite, biotite, chlorite, carbonate and metamorphic rock fragments. This polymictic and immature clast composition reflects the importance of local provenance, suggesting that intrabasinal structural highs represent additional source areas to the basin. Palynological analysis was carried out on selected core segments of the well in order to provide a biostratigraphic framework and palaeoenvironmental interpretation for the studied interval. In the investigated samples two biozones were distinguished: the Spiniferites bentorii oblongus Zone and the Spiniferites paradoxus Zone. The successive changes of the dinocyst assemblages reflect changes in the distance from the shoreline or the terrestrial input from the margin of the Mako Trough. The older assemblage indicates a more proximal setting in relation to the shoreline and/or a higher terrestrial input; the younger dinocyst assemblage — with a more open-water taxa point in relation to a greater distance from the shoreline — represents an increase in the water level, and/or decreased terrestrial input. The predominance of membranous dinocysts in this assemblage indicates a fluctuation in the lake surface salinity, or possibly a shift to a holoplanktonic lifestyle due to periodical oxygen depletion in the water column. The assemblages of both zones demonstrate their regional distribution throughout the whole Pannonian Basin and therefore they can be used to document regional scale trends in phytoplankton communities, as well as implying the communication of water bodies. The colour and preservation of the palynomorphs suggests significant burial heating and the high maturity of the sedimentary organic matter. In the studied samples a series of paragenetic events have been identified using petrographic methods. Early diagenesis was generally represented by cementation (i.e. of framboidal pyrite and carbonates with variable iron content) and weak mechanical compaction. On the other hand, late diagenesis involved pressure solution (chemical compaction), cementation (late pyrite) and, occasionally, dolomite replacement and mineral transformation (smectite to illite) processes. It is noteworthy that in these two core sections neither significant macroporosity nor microporosity were observed, this being due to pervasive cementation.

Palynological and paleobotanical investigation of bonebeds and other strata of the Csehbánya Formation from the vertebrate locality at Iharkút (Bakony Mts, Hungary) reveals well-preserved Santonian palynological assemblages dominated by the Normapolles group, with a minor component consisting of other angiosperm pollen, some gymnosperm pollen, and spores. Eleven species of Normapolles-type pollen grains belonging to seven genera and fruit remains of a new taxon, Sphaeracostata barbackae gen. et sp. nov., are described. The new species is very abundant in the material, represented by ca. 1000 specimens. The genus Caryanthus Friis and an unnamed form previously reported from Haţeg by Lindfors et al. (2010) are also present. Plants producing Normapolles-type pollen grains diversified during the Late Cretaceous, with a bloom in the Santonian. The palynostratigraphy of the Upper Cretaceous terrestrial sediments in the studied region is based on Normapolles-related species. The studied assemblage is assigned to the Oculopollis zaklinskaiae- Tetracolporopollenites (Brecolpites) globosus Zone (or Zone C) indicating a late Santonian age. Comparison of the Iharkút palynoflora with other known Upper Cretaceous palynofloras of Central Europe shows diachronous occurrence of Normapolles taxa at different geographic localities and warrants further investigation. The ecological requirements of the amphibian fauna reflect azonal conditions controlled by the availability of water, which is in agreement with the inferred ecological conditions based on the paleobotanical investigations. The fauna is of entirely non-marine character, further supported by isotope studies, in line with our data showing that the palynological samples contain no marine forms.