Review of Palaeobotany and Palynology最新文献

The Sauce Grande Formation of the Ventania System and Claromecó Basin, east-central Argentina, is a geological unit of glaciomarine origin showing evidence of the glaciation that affected the supercontinent of Gondwana during the late Paleozoic. The age of this unit was previously determined from scarce and poorly preserved fossils, but mainly from radiometric dating and the fossil content of the overlying geological units. This study presents a palynological assemblage obtained from the Sauce Grande Formation in the PANG 0002 borehole, drilled in the Upper Paleozoic Claromecó Basin. Based on the identification of key species, such as Converrucosisporites confluens, Pakhapites ovatus, P. fusus, Vittatina spp., and Weylandites magmus, an age no older than Gzhelian is inferred for the interval studied. The inferred age allows us to relate the glaciomarine deposits of the Sauce Grande Formation to the last episode of the late Paleozoic Ice Age. The palynological assemblage of the Sauce Grande Formation is correlated with the Converrucosisporites confluens-Vittatina vittifera (CV) Biozone of the Claromecó Basin. Based on updated information and new correlations of the CV Biozone with palynostratigraphic schemes established in neighboring basins (Chacoparaná, Paraná, and central-western Argentina), its age is adjusted to the Gzhelian-late Artinskian interval, encompassing the Carboniferous-Permian boundary. This new information contributes to refining the current biostratigraphic scheme of the late Paleozoic Claromecó Basin.

After the ecological discontinuity of the Aptian/Albian boundary, new biocoenoses were established. In the continental domain, ecosystems in which angiosperms began to play a role appeared, and soon became the framework for the success of this group, with considerable consequences. However, little is known about the palaeobiogeography of this period. The study of new wood fossils from south-western Europe together with bibliographical data shows that continental biogeography was compartmentalised there, with a strong north–south gradient. A weaker east–west gradient is also suggested.

Ukraine has a rich Proterozoic to Quaternary fossil record of photosynthetic microbes and plants. Particularly rich and scientifically important fossils of early multicellular organisms have been documented from the Ediacaran, early land plants from the Silurian–Devonian, coal-forming floras from the Carboniferous, typical post-extinction recovery vegetation and coal swamp forests from the Triassic and Jurassic, and well-preserved angiosperms and conifers from the Cretaceous and Cenozoic. These fossil floras help elucidate the temporal changes in the vegetation at the junction of Europe, Asia and the Tethyan microcontinental terranes and highlight biogeographic linkages between various floral provinces through deep time. The rich and variably preserved floras offer great scope for further taxonomic, palaeoecological, palaeoclimatic and biogeographic research. Extensive fossil collections are stored in several major institutional repositories scattered across Ukraine. Some of these institutions have now been occupied by Russian forces, and others have been damaged and remain under threat, risking potential loss for future research. The impact of the war on Ukrainian museums and scientific collections has implications for how fossil specimens are stored and what procedures are enacted to preserve collections in other parts of the world in the event of war, civil disturbance, or natural disasters.

Representatives of ginkgoaleans from the Middle Jurassic of the Stoilensky opencast mine in the Belgorod Region and the Mikhailovsky opencast mine in the Kursk Region, European Russia are described for the first time. Remains of ginkgoaceous affinity dominate in some samples and are represented by leaf fragments of Sphenobaiera angrenica (Samylina) Nosova, originally described from the Middle Jurassic Angren Formation in Uzbekistan where they are associated with female reproductive structures (collar complexes) of Nagrenia samylinae Nosova. Rare fragments of the collars were also found in the Stoilensky mine. These remains are assigned to Nagrenia sp. As well as in the Angren Formation, seeds of Allicospermum budantsevii Gordenko are recorded in the Stoilensky mine.

A high-resolution, radiocarbon dated, pollen sequence of the ecotone between the Grassland and Savanna Biomes, was extracted from a 2.5 m peat core at the Colbyn wetland in South Africa. The lithology indicates transitions between organic sediment, clay, and well-preserved peat layers. The pollen and micro-charcoal records suggest interactions between the seasonal climate, burning and possible human and other disturbance. The vegetation development over the last 4000 cal yr BP is compared with chronologically parallel pollen sequences from the nearby Moreleta River and Rietvlei Dam sequences. The study, that can be correlated with wider regional isotopic records of the region, shows drier conditions c. 3800 to 3400 cal yr BP, and around 800 cal yr BP, and a wetter phase at Colbyn c. 3000–1500 cal yr BP.

The Early Devonian plant fossil record provides evidence of large vegetation turnover events in addition to rapid morphological and anatomical changes among vascular plants. The Ardenno-Rhenish Massif has historically yielded a vast number of these plant fossils allowing us to obtain a nearly unparalleled snapshot of Early Devonian vegetation. Nonetheless, the interest for describing or redescribing fossil floras from this region has waned in recent years despite their inherent value to understand Early Devonian plant diversity dynamics. Here, we describe a newly collected macrofossil flora from the middle Emsian Schuttbourg Formation at Consthum Quarry (Luxembourg). Six different plant macrofossil taxa were identified, including Drepanophycus spinaeformis and Psilophyton cf. princeps, in addition to putative macroalgal and fungal remains. The flora also includes other equivocal specimens resembling Sawdonia, Huvenia and Zosterophyllum. The composition of the assemblage is extremely similar, at generic level, to older Pragian–early Emsian and coeval floras from nearby localities, which indicates that there was no major floral turnover until the latter part of the Emsian in this region. Taxonomic descriptions also highlight many of the underlying issues in identifying Early Devonian sterile specimens. Inconsistencies in plant fossil identifications from this region call for a thorough revision of Belgian and German floras that together could provide a high-resolution picture of plant diversity changes in the Early Devonian.

The Lower Devonian Rhynie chert preserves a remarkable diversity of microorganisms from an early terrestrial ecosystem. However, eukaryotic microalgae are rarely reported. This study describes Harpericystis verecunda gen. et sp. nov., a probable green alga (Chlorophyta) from the Rhynie chert, using more than 50 specimens, all of which are enclosed in a degraded land plant axis. Specimens include single cells up to 8(− 10) μm in diameter, dyads, decussate and tetrahedral tetrads, and small colonies comprised of 8 or 16 cells. Other specimens consist of both larger cells and tetrads of smaller cells, which either are the result of successive cell divisions (autosporogenesis), or have formed from multinucleate parent cells by directed cytokinesis. Cells, cell groups, and colonies are surrounded by a colorless mucilage. In some cases, it appears that the constituent cells of the colonies are interconnected by thickened plates of their envelopes or short processes. Harpericystis verecunda was non-motile and most likely planktonic. It shows similarities with various present-day colony-forming green algae, in particular with Coelastrum (Sphaeropleales) and Sphaerocystis (Chlamydomonadales), but its systematic affinity remains unresolved. This discovery is further evidence that intra-plant environments facilitated the preservation of fragile microbial life in the Rhynie setting.

The role of climate variability in the expansion and collapse of the Harappan Civilization in South Asia has been a subject of intense research and debate among archaeologists, Quaternary climate scientists, meteorologists, climatologists, historians, geographers, archaeobotanists, and anthropologists. Moreover, high-resolution palaeoclimatic studies have challenged the previous perspectives attributing societal collapses solely to socio-political and economic factors. These studies have revealed that periods of abundant rainfall, resulting from climate amelioration and/or due to seasonality: Winter vs. Summer precipitation, often coincided with the peak of socio-economic, cultural, and technological advancements in various civilizations. Conversely, abrupt climatic changes or rapid climatic changes, such as prolonged droughts, led to the destruction of irrigation systems, agricultural devastation, and widespread famines. These climatic disruptions triggered cultural adaptations, migrations, and sometimes even the collapse of entire civilizations. Climate forcing, particularly solar variability, played a primary role in repeated societal displacements, migrations, and deurbanization across different regions in the past. Additionally, the intensified El Niño-Southern Oscillation, a shift of the Indian Ocean Dipole to a strong negative state, and the southward migration of the Inter-Tropical Convergence Zone contributed to an extended period of weakened Summer Monsoons of South Asia and increased aridity. This depletion of water resources triggered the general demographic shift vis-à-vis the 4.2 ka event. The displacement was a response to a weakened Summer Monsoons of South Asia. In this research review article, we aim to understand the role of climate variability and explore the complex socio-climatological linkages in the mysterious displacement of once-thriving, highly advanced, widespread, and urbanized Harappan Civilization at the 4.2 ka.