Mid-Miocene terrestrial carbon isotope shift driven by atmospheric CO2 in the Xining Basin, NE Tibetan Plateau

Abstract: The Mid-Miocene Climatic Optimum (MMCO;  17–15 Ma) was a relatively recent warming event unrelated to human activity that provides an ideal analogue for our global warming future. However, the terrestrial ecosystem response to the MMCO remains unclear because of limited records. Continuous sedimentation from the Tashan Borehole (TSB) in the Xining Basin, northeastern Tibetan Plateau (NETP) spans the entire MMCO, with dates of 18.5–13.5 Ma from high-resolution paleomagnetic studies. Here, we explore the organic carbon isotope (δ13CTOC) record of TSB to investigate the NETP terrestrial ecosystem response to the MMCO. The sediments are typical floodplain deposits with δ13CTOC values ranging from −28.03‰ to −25.16‰, indicating terrestrial C3 plants were the dominant NETP terrestrial vegetation during MMCO. Further, an obviously negative shift of 0.6‰ occurred in TSB δ13CTOC during  17.6–14.2 Ma. TSB δ13CTOC values show the opposite trend to global benthic δ13C values, both in the long-term Monterey Excursion event and short-term carbon maxima events. Increased atmospheric CO2 during the MMCO enhanced the carbon isotope fractionation through photosynthesis by terrestrial plants and resulted in more 12C-enriched organic matter. Similar processes on a global scale subsequently accounted for part of the Monterey carbon isotope excursion. Therefore, in warm and humid conditions, the carbon isotope cycle of terrestrial C3 plants in the Xining Basin was mainly controlled by atmospheric CO2 concentration, with superimposition of effects of enhanced East Asian summer monsoon precipitation.

carbon isotope
palaeoecology
mid-miocene climatic optimum
monterey carbon isotope excursion
tibetan plateau


Transport pathways of black carbon to a high mountain Himalayan lake during late Holocene: Inferences from nitrogen isotopes of black carbon

Abstract: Historically, forest fires have played a significant role in the production and distribution of black carbon (BC), including its deposition in water bodies. BC can reach to water bodies through two main pathways: (i) wet and dry atmospheric deposition and (ii) transportation of soil BC via surface runoff. Identifying the transport pathways of BC after fire has proven to be a challenging endeavour. This study aimed to decipher the pathway of BC transportation to a lake (Wular Lake, Kashmir Valley, India) by utilizing nitrogen isotopic composition of BC (δ15NBC) from a sediment core spanning 3744 years. The δ15NBC record demonstrate that terrestrial N dynamics in the Kashmir Valley were predominantly influenced by shifts in climate condition during the late Holocene. The observed variations indicated lower δ15NBC, indicative of dominance of atmospheric transportation of BC to the lake, during relatively drier periods with higher forest fire activity. In contrast, higher δ15NBC, suggesting a dominance of soil BC transportation via runoff, aligned with relative wetter periods of low forest fire activity.

himalaya
lake
black carbon
nitrogen isotopes
forest fire
transportation


Holocene hydroclimate stability in three lake sediment records from the southeastern United States

Abstract: Many Holocene paleoclimate records from the southeastern United States (SE US) have limited chronological constraints and/or low sedimentation rates and consequently low resolution; this presents challenges in discerning the relative importance of synoptic–scale drivers of past hydroclimate. In this study we summarize three lake sediment records that are uniquely located to test hypotheses regarding the importance of the Pacific North American (PNA) pattern and the North Atlantic Oscillation (NAO) over the last 5000 years. At Pigeon Marsh, Buck Pond, and Halls Pond, we used sedimentological (radiocarbon dating of transect cores), physical (grain size), geochemical (carbon and nitrogen ratios and isotopes), and biological (palynomorphs) proxies to reconstruct lake level and lake environment. Moderate lake and environmental changes occur around 2000 cal yr BP at Buck and Halls Pond, which is regionally consistent with other paleorecords and may suggest that the NAO was an important control. However, our results generally indicate fairly stable hydroclimate conditions up until historical European settlement when land clearance caused vegetational and lake hydrologic balance changes that were unprecedented in both magnitude and rate compared to the middle/late Holocene.

lake sediment
southeastern united states
north atlantic oscillation
sedimentology
human impacts


Atmospheric CO2 controls on the MIS 6 glaciation: 10Be chronology of moraines in the Haizishan area, southeastern Tibetan Plateau

Abstract: A unifying theory interpreting the cause of ice-age cycles remains elusive, in view of the near-synchronous interhemispheric major climate shifts but anti-phased summer solar insolation signatures between hemispheres. Determining the timing and magnitude of mountain glaciations helps in shedding new light on this long-standing unsolved puzzle. Yet, robust glacial chronologies are limited for the pre-Last Glaciation time periods, impeding a full understanding of glacial histories and climatic mechanisms behind them in mountainous regions, such as the Tibetan Plateau (TP). Here, we report thirty-five new 10Be exposure-ages from moraine boulders in the Niqingqu Valley, eastern Haizishan Plateau, which adds to the existing glacial chronologies of the Hengduan Mountains, southeastern TP. The dating results indicate that four centennial to millennial-scale glacial activities occurred around 168.4 ka in the studied valley. Despite being indistinguishable in age, these high-frequency glacial fluctuations allow us to draw a conclusion that glaciers in the studied valley achieved the marine isotope stage 6 (MIS 6) glacial maximum prior to the Penultimate Glacial Maximum (PGM), inconsistent with Northern Hemisphere. We attribute the MIS 6 glacial maximum identified here to the response of glaciers to a combination of low-level atmospheric CO2 content and low northern high-latitude summer solar insolation/high summer-monsoon precipitation. The consistent local PGM and low CO2 levels suggest that low atmospheric CO2 contents are likely a necessary prerequisite for the MIS 6 glaciation.

be exposure dating
penultimate glacial maximum
atmospheric co
summer solar insolation
east asian summer monsoon


Stromatolites from the Majiagou Formation in the Ordos Basin, Northwestern China

Abstract: Stromatolites declined remarkably in the Middle Ordovician, which has been speculatively related to the concomitant proliferation of metazoan reefs during the Great Ordovician Radiation Event, however, they are flourish and widely distributed in the Middle Ordovician (Darriwilian) Majiagou (Machiakou) Formation in the Ordos Basin, northwestern China. The stromatolites in the Ma-5 Member of the Majiagou Formation in the Ordos Basin exhibit significant morphological diversity, and are ready to be divided into wavy and domal stromatolites from the south and west part, columnar in the Northeast part, accompanied with rarely hemispheroid and conical ones. The stromatolites in the Ma-5 Member distribute in a subcircular ring belt, which can be subdivided into three sedimentary divisions, mostly near the boundary between the gypsum-bearing dolomite flat and gypsum salt lake, of which, the north-central division, with its thicker stromatolite-bearing strata and more complex stromatolite morphologies, was the most favorable for the establishment of stromatolites, where grazing animals were absent and burrowing animals few. Some calcified microorganisms were recovered from the stromatolites, which substantially increases their known diversity for this interval and suggestive of a severe undersampling of the middle Ordovician calcified cyanobacteria fossil record in the Ordos Basin.

middle odovician (darriwilian) majiagou formation


Impact of water level change on shifts in subsistence regimes revealed by anthropogenic fire in the lower Yangtze basin during the Mid-Holocene

Abstract: The lower Yangtze is one of the regions of origin of rice agriculture but it is unclear if environmental change drove the transition from hunting-gathering to agriculture. Long-term and continuous lacustrine records of anthropogenic fire are a more effective means of addressing this problem than the fragmentary terrestrial records available for the lower Yangtze region. We constructed a Holocene fire history revealed by records of black carbon content (BCC) and grain size of the sediments of Lake Nanyi in the lower Yangtze. Our results show the following: 1) Peaks in fire activity occurred during ∼8400–6500 (fire peak P1) and ∼ 1100–0 cal BP (fire peak P2), while weaker fire activity occurred during ∼6500–1100 cal BP (S2). 2) This temporal pattern of fire activity, with a double peak (P1-S2-P2), was asynchronous from east to west across the lower Yangtze. The warm and humid climate would not have caused intense fires and the reduction of forest during ∼8400–6500 and ∼ 1100–0 cal BP. Therefore, we suggest that anthropogenic ignitions, corresponding to pronounced population fluctuations after 8400 cal BP, dominated the regional fire activity. Combined with archaeological evidence, the inverse relationship between the agricultural and population levels and fire intensity during the mid-Holocene suggests that fire intensity at this time was the result of the diversity of landscape types associated with prehistoric subsistence patterns, rather than the magnitude of anthropogenic activity. Combined with sea level, rainfall and archaeological evidence, we propose a mechanism whereby asynchronous water-level rise during ∼8400–6500 cal BP forced the migration of humans to the foothills where they often used fire to modify the landscape as part of a broad-spectrum subsistence pattern. Whereas, water-level fall after 6500 cal BP expanded the area of open ground for human settlement, and in this less diverse landscape, less use was made of fire in agricultural subsistence. Overall, our study reveals how regional water-level, driven by sea-level rise and extreme rainfall, delayed the transition from hunting-gathering to agriculture in the lower Yangtze region.

water level
anthropogenic fire
subsistence
mid-holocene
lower yangtze


Pedogenic processes and climatic conditions from Cretaceous (Albian) tropical paleosols of the Itapecuru Formation, Parnaíba Basin, northeast Brazil

Abstract: Paleosols are an under-utilized tool for paleoenvironmental and paleoclimatic reconstruction in Brazilian intracontinental basins. The Itapecuru Formation, from the Lower Cretaceous of the Parnaíba Basin, consists of a 600-m-thick succession of interbedded very fine-to-fine-grained sandstone, mudstone, and paleosols containing rich fossil assemblages. This paper provides a detailed description of the macro and microscopic pedogenic features of a hydromorphic paleosol profile whithin the Itapecuru Formation. Analyses of clay mineralogy and whole-rock geochemistry in the hydromorphic paleosols at the Prata locality are used to infer pedogenic processes, paleoclimate, paleohumidity and paleovegetation. Estimates of paleoprecipitation and paleotemperature using climofunctions, chemical index of alteration without potassium, and paleosol weathering index proxies (PWIs) show values ranging from 810 to 1042 mm/yr (SE = ±78.1 mm/yr) and 10.9 to 11.8 °C (SE = ±0.23 °C), respectively. Climofunction values (MAP and MAT), paleohumidity, Kӧppen aridity index, and pedogenic clay mineral content suggest a humid paleoclimate during soil-forming and weathering processes. Based on these climate data and previously published paleogeographic and palynological studies, the Cretaceous (Albian) Prata pedotype was formed within the equatorial humid belt with vegetation of wet tropical forests.

itapecuru formation
ultisols
redoxmorphic features
tropical paleosols


Last Glacial – Holocene variability of the European Slope Current, NE Atlantic

Abstract: The upper branch of the Atlantic Meridional Overturning Circulation (AMOC) in the mid-latitudes of the Northeast Atlantic remains poorly studied. This study provides a complete overview of the glacial, deglacial and Holocene dynamics of the easternmost portion of the AMOC upper branch, namely the European Slope Current (ESC) and its glacial equivalent known as the Glacial Eastern Boundary Current (GEBC). This is achieved through the study of the sediment core SU81–44 retrieved from the southern Bay of Biscay (BoB) (∼1000 m water depth), and by using a multiproxy approach (i.e. benthic foraminiferal assemblage, grain size proxies, oxygen and carbon stable isotopes, and neodymium isotopic composition of foraminiferal shells). During the glacial period and the onset of the deglaciation, the grain size proxies at SU81–44 fluctuate significantly. These fluctuations are coherent with changes in relative densities of benthic foraminiferal indicator species of current strength and ventilation, thus highlighting significant changes in the GEBC vigor through time. The SU81–44 data confirm the Dansgaard-Oeschger interstadial/faster-stadial/slower flow pattern previously observed in northern BoB. Our results also provide new constraints on the strength of the slope current during the late deglaciation and Holocene period with a significant reinvigoration of the ESC, and by extension the upper branch of the AMOC during the Bølling-Allerød warming. This seems to confirm the crucial role of the ESC in deep water formation at high northern latitudes, as it is the case today. Finally, our data show a progressive weakening of the ESC during the Holocene. We hypothesize a link with a long-term decrease in the density gradient between low and high latitudes that can be attributed to long term changes in insolation and the strength of the subpolar gyre dynamics.

late glacial
heinrich stadials
bølling–allerød
holocene
european slope current
northeast atlantic
amoc


Orbitally-forced meridional shifts of the westerlies modulated the hydroclimate of northeast China during the late Eocene

Abstract: The mid-latitude westerlies are a fundamental component of the global climate system. There has been extensive research about how meridional shifts of the westerlies influenced the wet-dry paleoclimate regimes of mid-latitude Asia during the Quaternary. However, how the westerlies operated in much older geological times, such as the late Eocene, particularly on an orbital time scale, is not fully understood. Here, we conducted detailed cyclostratigraphic and palynological analyses on a late Eocene (41.2–37.8 Ma) mudstone-shale sedimentary sequence from the Fushun Basin in northeast China, which uniquely records orbitally-forced meridional shifts of the westerlies. Cyclostratigraphic analyses reveal that the mudstone-shale rhythms exhibit a prominent short eccentricity cycle, with a modest expression of obliquity cycles and a weak expression of precession cycles. The palynological results show that the vegetation experienced frequent alternations between semi-desert and swamp forest, and the climate exhibited periodic oscillations between warm-dry and cold-wet climates. We propose that a combination of eccentricity-modulated low-latitude summer insolation and obliquity-forced high-latitude incipient ice sheet and meridional temperature gradient variations drove cyclical vegetation and hydroclimate fluctuations in northeast China during the late Eocene by regulating the intensity and displacement of the westerlies and the subtropical high. Our results imply that continued poleward movement of the westerlies and the subtropical high will lead to increased aridification along the southern margin of the westerlies under a continuous global warming scenario.

orbital forcing
late eocene
westerlies
subtropical high
fushun basin
palynological record


Organic matter enrichment in shale deposited proximal to paleo-uplifts and its impact on shale gas exploration

Abstract: Much of the global exploration and development of shale gas is focused on organic-rich shale deposited in basin or slope/basin margin settings. There is a clear need to assess the degree to which organic-rich shale deposited in other settings, notably proximal to paleo-uplifts, are promising shale gas prospects. Organic-rich sediments that accumulated proximal to paleo-uplifts are recognized globally and include the Cambrian Niutitang Formation, Ordovician-Silurian transition “hot shales”, and modern sediments of the Black Sea. Though the subject of recent research efforts, much remains to be learned of the mechanisms of organic matter enrichment of fine-grained sediment deposited adjacent to paleo-uplifts. Our study focuses on the Ordovician Wufeng Formation that accumulated proximal to uplifted areas of the Upper Yangtze platform. Though the TOC content of the analyzed Wufeng Formation samples recovered from near the paleo-uplifts is less than that of Wufeng samples collected from basin or slope/basin margin settings, average TOC value of the former can still reach more than 2

paleo-uplift
upper yangtze platform
shale gas
organic matter
sedimentary environment


Modern-type reef in ancient time - Palaeoecology of a Middle Devonian coral community from Madène el Mrakib (Anti-Atlas, Morocco)

Abstract: The southernmost Devonian reefs formed along the north-western margin of Gondwana. One of the best-preserved reefal palaeoecosystems of this area is found in the Givetian of Madène el Mrakib (Anti-Atlas, Morocco), exposing a vast, at least ∼1.2 km2 area of reef strata. This contribution documents the ecological succession, taxonomical structure and palaeoecology of this exceptionally diverse reef community. Combined evidence from the sedimentary succession and faunal changes records a trend of progressive shallowing. The ecological succession is characterised by an upsection increase in the abundance and diversity of the reef-building biota, accompanied by a shift in the dominant morphotypes of tabulate corals from platy (pioneering and diversification stages) to branching and massive forms (climax stage). The exceptionally rich, shallow-water reef community occurs in the uppermost part of the succession. The climax community is dominated by extraordinarily large, branching tabulate corals (mostly Thamnopora), with the notable role of massive alveolitid, heliolitid and favositid tabulates, as well as large, solitary rugose corals. A surprising feature of this assemblage is the rather subordinate role of stromatoporoids, generally regarded as a main component of the shallow-water Devonian reefs. Remarkably, the observed community structure is closer to that typical of modern shallow-water reefs, dominated by branching scleractinian corals from the family Acroporidae, than to the archetypal Paleozoic reefs. These distinctive traits of the Madène el Mrakib community make it particularly suitable for comparative studies between Devonian and modern reef ecosystems, showing that these communities shared notable similarities in terms of their ecological successions, zonation patterns, dominance of branching corals and high morphological variability in shallow-water environments, and adaptations of corals to turbulent conditions.

devonian
shallow-water reef
branching corals
tabulate corals
photosymbiosis
gondwana


Meteoric diagenesis influenced by East Asian Summer Monsoon: A case study from the Pleistocene carbonate succession, Xisha Islands, South China Sea

Abstract: The East Asian Monsoon (EAM) has significantly influenced various depositional and diagenetic processes in carbonate sediments in much of East and South Asia during the Cenozoic. The relationship between the EAM and marine carbonate platforms, which are widely developed in this region, however, remains largely unknown. Based on petrographic, mineralogical, and geochemical analyses of the carbonate succession (∼237 m thick) on the Xisha Islands, South China Sea, meteoric diagenesis and its relationship with the East Asian Summer Monsoon (EASM) during the Pleistocene were studied. Various petrographic features, stable isotopes (δ13C, δ18O), and trace elements (Sr, Fe, Mn, Rare Earth Elements and Y) indicate that this succession was extensively altered by meteoric diagenesis, producing four exposed surfaces embedded in the shallow coral reef sediments. Given this data, we suggest that the meteoric diagenesis that affected this succession occurred during periods of low sea-level, and was potentially related to the relative intensity of the EASM. During strong EASM periods, particularly during the Mid-Pleistocene Transition ∼0.9 Ma, meteoric diagenesis was intense, as suggested by the complete alteration of unstable minerals, extreme dissolution, the presence of reddish-brown iron oxides, and a large negative excursion of δ13C (−6.2‰). The influence of the EASM on meteoric diagenesis of Pleistocene carbonate platforms can be identified throughout the South China Sea. This study sheds light on the relationship between meteoric diagenesis and paleo-climate conditions in carbonate platform regions that are influenced by monsoons.

meteoric diagenesis
east asian monsoon
carbonate rocks
pleistocene
xisha islands


Evolution of Silurian phytogeography, with the first report of Aberlemnia (Rhyniopsida) from the Pridoli of West Junggar, Xinjiang, China

Abstract: The development of phytogeography is an essential aspect of floral evolution. The Silurian is considered a pivotal period for the development of early land vegetation based on both macrofossil and microfossil evidence; however, the evolution of phytogeographic zonation at that time remains controversial. In this paper, we describe a new species of the rhyniopsid, Aberlemnia junggaria sp. nov., from the Pridoli (upper Silurian) of West Junggar, Xinjiang, China. The new plant consists of at least three orders of axes, an oval to reniform terminal sporangium bearing in sparse ultimate axes and sporangium with a nearly enclosed dehiscence line. A dataset of global Silurian macrofossil records was compiled, including 30 species within 24 genera from 38 localities covering 8 main paleogeographic blocks. Using these data, the spatial-temporal distribution of Silurian plant macrofossils was mapped. Biogeographic evolution is revealed for the first time by means of network analysis and cluster analysis, and two phytogeographic realms, the West Junggar-Vietnam and Laurussia-North Gondwana realms are provisionally recognized during the Pridoli Epoch. Considering the widespread microfossil evidence for land plant diversification and dispersal, this global phytogeographic zonation might have onset at an even earlier time.

paleobotany biogeography embryophyte sporophyte spores


Hydroclimatic changes in the Core Monsoon Zone of India since the Last Glacial Maximum: An overview of the palynological data and correlation with the marine and continental records

Abstract: The Indian Summer Monsoon (ISM) is one of the major components of the Asian Monsoon System that exhibits a complex ocean-atmospheric-coupled mechanism of the tropics, which is indispensable in inter-hemispheric heat transfer on Earth. The ISM causes ∼80

indian summer monsoon (ism)
inter-tropical convergence zone (itcz)
last glacial maximum (lgm)
holocene
palaeoclimate
core monsoon zone
india


Holocene climate variability and the effect of anthropogenic activities on the vegetation landscape of western-central Mexico

Abstract: Atmospheric forcings control climate variability and at the same time control vegetation distribution and forest fires during the Holocene. Paleoenvironmental studies are scarce in western Mexico, particularly those documenting vegetation change, landscape dynamics, and fire regimes. This study presents a vegetation and fire occurrence reconstruction in the Etzatlán-Magdalena paleolake, western Mexico, during the Holocene. The reconstruction relies on fossil pollen, macrocharcoal and microcharcoal analyses of a clay sediment core. In the early Holocene (10–5.8 ka), climatic conditions were humid between 10 and 9 ka, represented by cloud forest of Liquidambar, Juglans, and Betulaceae. After 9 ka Quercus forest expanded and a trend towards warm conditions was detected, associated with high fire activity, suggesting the presence of a dry forest. Fire episodes at local and regional scale had a long-term negative effect on temperate and cloud forests. In the middle Holocene (5.8–2.1 ka), temperate forest was replaced by dry forest, indicating a drier climate. In the late Holocene (2.1–0.3 ka), the expansion of disturbance taxa and the low local fires indicated an open landscape and dry conditions. Human activity was documented by an increase of Cheno-Amaranthaceae, Poaceae and microcharcoal concentration after 3.5 ka. This research provides relevant information on the vegetation dynamics in a region with a long history of human settlement.

paleoclimate
pollen
fire history
human perturbation
biodiversity


Diversity dynamics, faunal turnover and radiation pattern of the Middle Ordovician trilobites in South China

Abstract: Available data on the temporal and geographical distribution of Middle–early Late Ordovician trilobites in South China were reviewed under a high-resolution biostratigraphical framework to investigate the diversity dynamics and explain the faunal turnover and radiation pattern of trilobites during the Middle Ordovician. Three macroevolutionary phases are recognized on the basis of the diversity changes at taxonomic levels. Cluster analysis shows three trilobite groups, two distinct trilobite faunas and three faunal turnovers through nine time slices. Three trilobite groups (Groups A, B and C) are coupled with three macroevolutionary phases, and characterized by different proportions of the Whiterock Fauna. Two distinct trilobite faunas (Early–Middle Ordovician and Late Ordovician Trilobite Faunas) and three faunal turnovers could be recognized at different similarity coefficients, their replacements were mainly affected by changes of sea level and substrate conditions. The trilobite radiation was manifested by the development, expansion and domination of the Whiterock Fauna (part of the Paleozoic Evolutionary Fauna) through the Middle Ordovician. The first diversity acme of trilobites occurred during the Dapingian–early Darriwilian, while the radiation centre gradually shifted from inner platform to outer platform environments. From the end Darriwilian onwards, elements of the Whiterock Fauna had further developed and dominated all environmental settings from the inner platform to the lower slope, coinciding with the second and more extensive radiation of trilobites in South China. Two phases of radiation may have been directly triggered by two major transgressions during the late Dapingian–early Darriwilian and the late Darriwilian–early Sandbian respectively. In addition, climate cooling and various substrate conditions, as well as the increased oxygen levels in the atmosphere and marine water, nutrients and tectonic movements during the Middle Ordovician may have provided essential conditions for the trilobite radiation.

great ordovician biodiversification event


Editorial preface to special issue: Recovery of marine ecosystem after the Permian-Triassic mass extinction: New progress from South China

Abstract: The end Permian to Middle Triassic interval (∼252–242 Ma) witnessed the largest marine mass extinction and the most delayed recovery in the Phanerozoic. The nature and mechanism of these biotic and environmental changes remain unclear. This special issue focuses on the Triassic marine sediments in South China, which provide unique documentation of the collapse and recovery of marine ecosystems. Six papers focus on biotic changes and their ecological significance in Early and Middle Triassic times, documenting evidence from bivalves, marine reptiles, stromatolites, hybodontid teeth, vertebrate coprolites, and other putative fossils. Two papers study conodont biostratigraphy across the Permian-Triassic boundary (PTB) and Induan-Olenekian boundary. Two papers reconstruct the palaeoenvironments of the Early Triassic Chaohu Fauna and Middle Triassic Luoping Biota. Two further papers present new marine δ13C records and biomarker data and link them to volcanic eruptions in Early Triassic times. These new findings are important for understanding the co-evolution between biotic and environmental changes in the aftermath of Permian-Triassic boundary mass extinction.

mass extinction
recovery
triassic
south china
ocean anoxia
volcanisms


Evolution of sedimentary environment in the Eastern Henan Basin since the Late Pliocene

Abstract: The Eastern Henan Basin is situated within the downstream alluvial plain of the Yellow River, harboring an impressive accumulation of over 500 m of fluviolacustrine strata since the Pliocene. However, the evolutionary characteristics and driving factors of the sedimentary environment in this region remain unclear due to a lack of reliable chronological constraints on the sedimentary sequence. Here, two cores were retrieved from Hangkonggang (HKG, 303.5 m) and Baisha (BS, 320.2 m) in the Eastern Henan Basin for comprehensive analyses of chronology and sedimentology. A combination of paleomagnetism, electron spin resonance (ESR), and optically stimulated luminescence (OSL) dating results indicates that sediments of two boreholes were accumulated spanning the last ∼3.48 Ma. Grain size distributions (GSDs) of typical sedimentary facies show that the boreholes predominantly encompass three types of sedimentary facies: riverbed, levee, and floodplain. Downcore variations of mean grain size (MGS) reveal that the sedimentary environment in this basin evolved from a dominant riverbed setting during the late Pliocene (3.48–2.72 Ma) to alternations between the floodplain and levee facies during the early Pleistocene (2.72–1.25 Ma) and subsequently between the riverbed, levee, and floodplain after 1.25 Ma. It was closely associated with the decrease in East Asian monsoon precipitation at ∼2.72 Ma and the increase at 1.25 Ma. Notably, the abrupt coarsening of MGS after ∼1.25 Ma was synchronized with the formation of the Sanmenxia terraces, implying the significant influence of the evolution of the Yellow River. Our results suggest that the sedimentary environment of the Eastern Henan Basin was predominantly affected by the stepwise evolution of the East Asian monsoon since ∼3.48 Ma and complementary landform transformation of the Yellow River since at least ∼1.25 Ma.

plio-pleistocene
fluvial deposits
grain size
sedimentary environment
east asian monsoon
magnetic stratigraphy


Re-Os geochronology of the Middle to Upper Jurassic marine black shales in the Agardhfjellet Formation, Central Spitsbergen, Svalbard: A cornerstone for global faunal correlation and Os isotopic change

Abstract: Ammonite provincialism makes it difficult to link the Boreal and Tethyan realms during the Late Jurassic to Early Cretaceous time. Absolute ages through radiometric dating offer new age information that is independent and complementary to relative ages based on biostratigraphy. In this study, we report seven new Re-Os ages for black shales from the Agardhfjellet Formation, Svalbard. We also report pyrolysis results, carbon and sulfur stable isotopic data, and initial 187Os/188Os ratios to evaluate the paleoenvironment during organic-rich shale deposition. Re-Os ages are derived from three Boreal ammonite zones: (1) 159.2 and 160.1 Ma from the shale intervals containing Cadoceras sp.; (2) 149.6, 149.9, 150.8, and 151.9 Ma from the Rasenia cymodoce Zone in the Early Kimmeridgian, which is the equivalent of the Sutneria platynota and Ataxioceras hypselocyclum zones in the Tethyan realm; (3) 146.8 Ma from an upper Volgian interval above the occurrence of Laugeites sp.. Within this 14.5 Myr interval, the initial Os profile shows a gradually increasing trend from 0.335 (one of the lowest shale values throughout the Phanerozoic) to 0.529, consistent with previous initial Os studies and Sr isotopic ratio chemostratigraphic studies. The trend of increasing initial Os ratios indicates an increase in continental runoff relative to unradiogenic Os input from mantle sources, such as seafloor hydrothermal activity or ultramafic source rocks. We provide new Re-Os geochronological anchors in the Late Jurassic with new Re-Os ages and propose correlations of specific Late Jurassic ammonite zones between the Tethyan and Boreal realms. In turn, the gradual increase in seawater Os isotopic ratios may signal climate change in the Late Jurassic, indicating the increase of radiogenic Os or decrease of unradiogenic Os, induced by high continental runoff or less hydrothermal/volcanic activity.

black shale
late jurassic
agardhfjellet formation
re-os ages
initial os/os ratio


Significance of site-specific factors to peat accumulation indicated by differences in Holocene histories of dust delivery and peat deposition at two neighboring locations in the Altai Mountains, northwestern China

Abstract: Peatlands can archive exceptional paleoenvironmental histories of dust delivery because of their uninterrupted and elevated accumulation rates, yet long-term records of dust deposition and its effect on peat accumulation are rare in the arid and semiarid Asian regions that can be major dust sources. We present here high-resolution Holocene peat accumulation and paleodust records from the Tielishahan (TLSH) and Halashazi (HLSZ) peatlands in the Altai Mountains of northwestern China. We find that although the two peatlands share common histories of external climate forcing and dust delivery, they have significantly different long-term rates of peat accumulations. Peat deposition initiated  2 kyr earlier in the HLSZ peatland than in the TLSH peatland, exhibiting higher peat accumulation rates and greater mineral dust fluxes during the early Holocene, but it has constantly smaller values from the mid-Holocene to the present. The TLSH peatland has a higher peat accumulation rate and mineral dust flux during the early Holocene, lower values during the mid-Holocene, and increasing values during the latest Holocene. The elemental proxies in the two peat cores indicate that atmospheric deposition is the major factor in controlling delivery of mineral elements in HLSZ peatland, whereas elemental delivery in the TLSH peat record is affected by both the regional atmospheric dust flux and the water table under this sequence. We also find that peat accumulation is closely related to mineral dust deposition, as most Asian locations generally share similar patterns in long-term peat accumulation and dust deposition. We postulate that increased aridity in the dust sources of arid central Asia and stronger westerly winds induced by negative NAO variations are key drivers on greater dust deliveries. We further postulate that local factors, such as site-specific differences in permafrost thawing, the areas of the peatlands, and their hydrology are the main reasons for the asynchronous Holocene histories of these two neighboring peatlands. These local factors should be considered when interpreting long-term paleoclimate records from rates of peat accumulation and paleodust delivery.

peatlands
peat accumulation
dust deposition
holocene
the altai mountains of northwest china


Holocene geomorphological evolution of a sediment-starved coastal embayment in response to sea level change: Insights from the Qing'ao Embayment, southern China

Abstract: Aiming to gain a better understanding of the response of sediment-starved coastal systems to the climate-driven sea level change, this study examines the Holocene evolution history of Qing'ao Embayment, southern China, as a case study. Results suggest three distinct stages of the evolution history: Stage 1 (8400–6000 cal yr BP) records an initial sedimentation phase associated with the early Holocene marine transgression into the embayment. Stage 2 (6000–3000 cal yr BP) records early sediment deposition under relatively strong hydrodynamic inshore/open-bay environment during early marine regression. Stage 3 (3000 cal yr BP to present) records two substages: Stage 3a relates to the semi-enclosed bay, intertidal and lagoonal salt marsh facies between 3000 and 1300 cal yr BP, and Stage 3b records the final infilling of the embayment into a lagoonal plain. This evolution model suggests that the rates of sea level change and sediment accretion are the two major controlling factors for the Holocene geomorphological evolution of sediment-starving coastal systems. Comparison of the evolution of Qing'ao embayment with sediment-supply rich large-river estuary/deltas reveals unique features in the response to Holocene sea level change of this sediment-starved embayment: During the early Holocene marine transgression, sediment starts to accumulate in the small embayment around 8400 cal yr BP, hundreds of years later than in large river estuaries. During 8400–6000 cal yr BP, sediment accretion rate remains dramatically lower than sea level rise rate, which results in the quick growth of sediment accommodation space during this stage. Around 6000 cal yr BP, though sea level has remained relatively stable and large-river deltas have been growing for about 1000 years, the sediment-starved embayment was still under shallow marine and/or open bay conditions. At 3000 cal yr BP, shoreline started to prograde in sediment-starved embayment, which is about 3000 years later than large river deltas. Finally, agricultural activity started around 1300 cal yr BP in the embayment, thousands of years later than large river deltas. Limited or minimal fluvial sediment supply to the small embayment has constrained the land expansion during the sea level stabilization since mid-Holocene, and the limited living space might result in the much later agricultural activity in such coastal system. Due to the different balances between sea level change and sediment flux, sediment-starved coasts are expected to be under higher risks than large river deltas. However, earlier and more extensive human activities in large river basins have resulted in the reduction of sediment discharge that heighten the risks of large river deltas against future sea level rise. Thus, more attention should be paid to the coastal sediment supply budgets in the context of the background of rising sea level.

sediment-starved coastal embayment
sedimentary environment
sea level change
holocene
sediment supply


Back-reef and lagoonal communities, Givetian (Middle Devonian) in Guangdong, South China: Their role in global Devonian reef development

Abstract: Back-reef and lagoonal communities played an important role in the construction of global reef ecosystems and shallow water carbonate factories during the Devonian Period, but their reef-building significance is not fully understood. This study describes a previously undocumented Givetian stromatoporoid biostromal sequence, 12 m thick and comprising 7 biostromes, in the Tangjiawan Formation of Yaozhai, Guangdong Province, Southeast China. Large bulbous or columnar stromatoporoid Actinostroma and delicate dendroid stromatoporoid Amphipora are abundant, with a comparatively smaller presence of tabulate corals, rugose corals, brachiopods, gastropods, calcimicrobes, and tubeworms. The dominant Actinostroma-Amphipora assemblage, together with leperditicopid ostracods, parathuramminid foraminifers, and calcispheres, indicates a shallow, low-energy back-reef to lagoonal setting. Taphonomic analysis shows a common occurrence of overturned skeletons, and the deposit is interpreted as a parabiostrome constructed in a low-energy environment and affected by episodic high-energy events. Statistical data of similar global assemblages from the Lochkovian to the Famennian based on 153 localities show a relatively rare occurrence of back-reef and lagoonal communities from the Lochkovian to the Eifelian, peaking during the Givetian and Frasnian together with metazoan reefs then declining sharply in the Famennian after the Kellwasser Event. Although autobiostromes have rarely been documented, the densely packed reworked bulbous/domical and dendroid stromatoporoids justify the existence of low-diversity but highly abundant metazoan ecosystems in back-reef to lagoonal settings. This study thus highlights our understanding of the back-reef and lagoonal facies and the important role they played in the expansion of large-scale carbonate factories and reef ecosystems during the Middle to Late Devonian.

stromatoporoids
biostromes
back-reef to lagoon
devonian
reef expansion


Eocene-Oligocene large-scale circulation of the East Asian summer monsoon recorded in neritic carbonates of the proto-South China Sea

Abstract: When the modern features of large-scale Asian monsoonal circulation were set-up is poorly constrained and pre-Neogene monsoonal archives are rare. This study investigates the temporal evolution of neritic carbonates in the proto-South China Sea to reconstruct East Asian monsoonal currents and winds during the middle to late Paleogene. Analysis of three-dimensional seismic and well core data from the North-West Palawan block reveals the occurrence of a set of thick (>125 m), aggrading Halimeda bioherms, early Oligocene in age. By analogy with Holocene green algal buildup counterparts, they are interpreted to form in nutrient-rich areas subject to upwelling currents and reflect the early presence of a strong coastal jet in the Proto-South China Sea, as seen today during the summer monsoonal season. The analysis of the underlying mixed carbonate–siliciclastic ramp shows that mesotrophic conditions already prevailed during the late Eocene, thus suggesting that modern-like summer East Asian Monsoon large-scale circulation was possibly active as early as the late Eocene in the Proto-South China Sea. Evidence for upwelling currents vanishes in late early Oligocene carbonate-producing biota, that are characterized by the significant development of euphotic hermatypic coral communities reflecting lower nutrient concentrations. This turnover coincides with the opening of the modern South China Sea and is interpreted to result from the southward drift of the North-West Palawan block which placed the area away from the Chinese margin and the coastal jet. Our results highlight therefore that many of the features of the summer East Asian Monsoon large-scale circulation are rooted in the middle Paleogene.

monsoon
carbonates
paleogene
southeast asia
coastal jet


Recurrent E - W oscillations of the ice flow confluence of the East and West Antarctic ice sheets in the central Ross Sea, Antarctica, from the Middle Miocene to the present day

Abstract: We present a multidisciplinary provenance study on legacy cores drilled in the 1970s during DSDP Leg 28 at sites 271 and 272, in the central Ross Sea, Antarctica. The two sites combined provide a discontinuous glaciomarine sedimentary record covering 18 myr, from the Middle Miocene to the present day. The two boreholes are located on the continental shelf and near the edge of the Ross Ice Shelf, in the middle of the Ross Sea, at a key site close at 180° longitude that is considered to represent the present confluence between ice flows fed by West Antarctica and East Antarctica. The study employs UPb dating of detrital zircons and apatites, coupled with apatite fission-track dating and trace element and REE compositions. Based on the sedimentary provenance, our data show a recurrent E-W oscillation of the confluence of the West Antarctica and East Antarctica ice flows, allowing phases of advance and retreat of the West Antarctic Ice Sheet to be inferred.

middle miocene-quaternary glaciomarine sediments


Basin-scale reconstruction of late Pleistocene-Holocene fluvial landform evolution and its mechanisms in transitional areas between Taihang Mountain and North China Plain

Abstract: The processes and mechanisms of fluvial landform evolution, especially in the transitional zones between mountains and plains, are of great significance for predicting future regional sustainability and ecosystem stability in the basin. As a region of significant cultural and ecological importance, the transitional area between Taihang Mountain and North China Plain still has a limited understanding of the fluvial landform evolution. With detailed field surveys and 39 optically stimulated luminescence (OSL) ages of 14 sections, we reconstruct fluvial landform evolution in the southern piedmont of the Taihang Mountain since the late Pleistocene. The results show that two major fluvial processes occurred during 18–10 ka BP and 9–3 ka BP. Meanwhile, the late Pleistocene-Holocene can be divided into 5 intervals in the alluvial fan and floodplain areas, with corresponding ages of 3 ka BP, 9–3 ka BP, 10–9 ka BP, 18–10 ka BP, and before 20 ka BP, respectively. The results also indicate that the regional fluvial processes primarily result from climate change and tectonic activities, and secondarily result from sea level fluctuation. Additionally, the prehistoric settlement pattern was also shaped by the evolution of regional rivers. Our research is significant for understanding the evolution and mechanisms of fluvial landforms in transitional zones.


The trace fossil Thalassinoides paradoxicus Kennedy, 1967 revisited from its type locality (Albian-Cenomanian chalk, SE England)

Abstract: The trace fossil Thalassinoides includes ichnospecies that have been recognised for a long time and widely used in the interpretation of depositional systems. Despite its broad occurrence, the ichnotaxonomic status of this important ichnogenus is far from being unmistakable, which in turn hampers its application in palaeoenvironmental reconstructions. One of the most common ichnospecies is Thalassinoides paradoxicus, originally described from the Paradoxica Bed of the Lower Chalk in the Hunstanton Cliff in SE England. To demarcate this characteristic form from similar ichnospecies, T. paradoxicus is reexamined and described from its type locality. It is characterised by an ‘irregular, very extensive horizontal burrow network, occurring at several levels, connected by vertical shafts’ (Kennedy), but its morphological variability also includes a range of significant architectural elements as well as burrow portions with a laminated wall, scratches and pellets. A series of colonisation events along omission surfaces can be reconstructed based on the occurrence of several burrow generations. T. paradoxicus is an important constituent of shallow-marine environments and subtle variations in morphology may help to constrain facies interpretations. Based on modern analogues and finds of body fossils within their burrows, decapod crustaceans (foremost callianassid shrimp) are known producers of T. paradoxicus from the Mesozoic onwards, whereas older records can be attributed to other malacostracans but also trilobites.

cretaceous
chalk
burrow
ichnotaxonomy
decapoda
callianassidae
mud shrimp


Quaternary evolution of the Meiji Atoll (Mischief Reef) in the southern South China Sea

Abstract: This paper describes the Quaternary evolution of Meiji Atoll (also known as Mischief Reef) in the southern South China Sea. Findings are based on a sedimentological and paleontological investigation of the uppermost 150 m of core NK-1. Through the Quaternary, open-lagoon sediments initially developed from ca. 2.6 to 1.6 Ma, which were succeeded by backreef sediments from 1.6 to 1.1 Ma, and subsequently by reef-flat sediments from 1.1 Ma to present, as the atoll evolved. The deepest depositional environments occurred between 2.0 and 1.6 Ma as a result of significant rates of subsidence in the Dangerous Grounds area. Coral abundance steadily increased during the Quaternary due to the secular eustatic sea-level drop and continuous high temperatures in the southern South China Sea. After the start of the Mid-Pleistocene Transition from 1.25 Ma, there was an increase in the amplification of short-eccentricity glacio-eustatic cycles, which resulted in two impacts. First, more frequent exposure horizons developed over the atoll due to an increase in amplitude of short-term sea-level fall events. Second, the occurrence of the thickest coral framestone units developed at around 0.8 Ma, perhaps linked to prominent short-term sea-level highstands (i.e., 125-ka cycle) and moderate subsidence rates. In summary, we document the Quaternary evolution of the Meiji Atoll, and show how variations in sea surface temperature, eustatic sea level, and tectonics have influenced its development. These findings have broader implications for understanding the Quaternary evolution of similar tropical carbonate atolls in the region.

carbonate sediments
coral reef
quaternary
meiji atoll
south china sea


Multiproxy approach to reconstruct the climate and environment of a new late Middle Pleistocene vertebrate site in northwestern Italy

Abstract: The Moleto site (Ottiglio, AL, Piemonte, Italy) was discovered in the 1990s in an abandoned quarry carved into a Burdigalian–Langhian carbonate succession called Pietra da Cantoni. Sediment collection in three closely spaced fissures provided a rich vertebrate association whose age can be constrained to the late Middle Pleistocene on the basis of the presence of the extinct water vole Arvicola mosbachensis and its enamel characteristics (SDQ values ranging from 100 to 130). The very similar faunal content, evidenced by the common presence of Arvicola mosbachensis and its similar SDQ values, is indicative of a coeval deposition of the fillings of the three fissures. The vertebrate assemblage is represented by 30 taxa, including amphibians, squamate reptiles, birds, and mammals. Interestingly, a diverse fish assemblage from the embedded sediments of the Miocene Pietra da Cantoni has been found in the fissure fillings. We present here a multi-method approach using the small vertebrate assemblages (rodents, insectivores, amphibians, and squamate reptiles) from Moleto to characterize the environment and climate of the site. In order to reconstruct the palaeoenvironmental and palaeoclimatic conditions, we applied the Mutual Ecogeographic Range using UDA-ODA technique, the Bioclimatic Model, the Habitat Weightings, and the Quantified Ecology methods. The results revealed a landscape dominated by woodland habitats with presence of open humid meadows, under temperate and moist climatic conditions, although somewhat colder and drier than today. According to all evidence, the associations from Moleto would correspond to the interglacial MIS 7.

vertebrate assemblage
mutual ecogeographic range
bioclimatic model
quantified ecology
habitat weightings
marine isotope stage 7


Sabretooths, giant hyenas, and hominins: Shifts in the niche of Early Pleistocene scavengers in Iberia at the Epivillafranchian-Galerian transition

Abstract: The Epivillafranchian and the transition to the Galerian (1.2–0.9 Ma) was a period marked by environmental fluctuations and faunal turnover. Homo arrived into Europe around 1.4 Ma. ago, and was established in Iberia during the Epivillafranchian, as evidenced by the oldest sites with hominin fossils located in the Iberian Peninsula. The Iberian ecosystems offered a variety of trophic resources to hominins, including the opportunity to scavenge carcasses of large ungulates killed by a diverse predatory guild, especially due to the presence of two sabre-toothed cats. It has been claimed that the presence of Pachycrocuta brevirostris, a strong competitor for carrion, prevented hominins from exploiting abandoned carcasses as a reliable meat and fat resource. However, computer simulation experiments suggest that the coexistence of P. brevirostris and hominins competing for carrion was ecologically viable in the Epivillafranchian. Nevertheless, the faunal turnover of the Epivillafranchian-Galerian transition drastically changed the composition of the large carnivore fauna. The changes include the extinction of the sabre-toothed felid Megantereon, frequently considered a key provider of partially consumed carcasses, and the demise of the hyperscavenger P. brevirostris. All these changes modified the ecological scenario and the opportunities for hominins and other facultative scavengers. Computer simulation experiments using the agent-based model SCAVCOMP-ABM are used here to evaluate the viability of the coexistence of hominins and giant hyenas in the Epivillafranchian-Galerian transition. Different ecological scenarios defined by the composition of the predatory guild, ecosystem productivity, and competition pressure from other scavengers are evaluated. Results suggest that hominins and giant hyenas could coexist during the Epivillafranchian with different carnivore guilds, but a disruption of the scavenging niche likely occurred in the transition to the Galerian, coinciding with the extinction of P. brevirostris. A low ecosystem productivity during the cold intervals, maintenance of a high competition for carrion with other facultative scavengers, and a hypothetical social behaviour of the sabre-toothed cat Homotherium latidens appear as key factors to explain the changes in the scavenger guild at the Epivillafranchian-Galerian transition.

pleistocene
palaeoecology
western europe
computer simulation
trophic ecology


Diversity of leaf architecture and its relationships with climate in extant and fossil plants

Abstract: In this contribution, the diversity of functional leaf architecture and its association with climate is studied for extant woody dicot species of North America and Europe/South West Asia. The results are compared to fossil leaves of seventeen locations in Central Europe ranging from the Paleogene to Neogene. Four functional leaf traits, lobation, margin, type of primary and secondary venation, were selected as defining sixteen basic functional architectures (Trait Combination Types, TCT). Diversity of leaf architecture was studied as Shannon diversity (meaning frequency and evenness of TCT occurrence) as realized by site-specific species composition. The extant data indicate significant positive correlations of Shannon diversity of leaf architecture with temperature particularly for North America. After having reached a peak at about 18 °C MAT, functional diversity of leaf architecture then declines in North America with rising MAT. This decline occurs mostly for drier sites, probably because humidity becomes more influential at higher MAT, with low water availability driving selective pressure towards adaptive convergence. The data indicate that warm environments are able to accommodate a higher variety of leaf types than colder environments, unless water supply is scarce. The fossil data essentially agree with the recent data, with the exception of sites harbouring fossil leaves preserved in marine sediments. Here, the diversity of leaf architecture is lower which is probably due to taphonomic bias. Highest leaf architecture diversity was found for the Pliocene sites, although no distinct relationship with stratigraphic age could be identified. The results of this study indicate that diversity of leaf architecture may be a useful source of information for palaeoecology and palaeoclimate and merits further study.

functional diversity
shannon diversity
functional traits
leaf venation
leaf margin
leaf lobation


Natural and anthropogenic forcing on the fate of sedimentary organic matter in the South Yellow Sea during the Holocene

Abstract: Long-term organic matter (OM) burial in the ocean is essential to the global carbon cycle. Mud deposits, such as South Yellow Sea mud deposit (SYSMD) located in the central South Yellow Sea (SYS), are ideal for the study of long-term OM burial. A sediment core YS-A from the SYSMD was analyzed for lignin phenols and bulk OM properties to reveal the driving forces of sedimentary OM (SOM) fate during the Holocene. SOM burial was found to be dominantly influenced by sea level rise and increased East Asian summer monsoon during 11.0–7.0 ka BP. During 7.0–1.0 ka BP, the fate of SOM was controlled by El Niño Southern Oscillation on the millennial time scale, and correlated with East Asian winter monsoon variability on the centennial time scale. Remarkably, anthropogenic perturbation has gradually overwhelmed long-term climate control on the fate of SOM since 1.0 ka BP, and this phenomenon became more evident after 0.4 ka BP.

sedimentary organic matter
south yellow sea
holocene
climate change
human activities


Holocene climate and catchment change inferred from the geochemistry of Lashmars Lagoon, Kangaroo Island (Karti/Karta), southern Australia

Abstract: We present a continuous ∼7000-year sedimentary record from Lashmars Lagoon, Kangaroo Island (Karti/Karta), southern Australia, a region heavily impacted by drought and bushfires in recent decades. Records such as this are vital to contextualise current climatic and environmental shifts, particularly regarding the interplay between hydroclimate and fire-related disturbances in this ecologically sensitive area. We use high-resolution μX-ray fluorescence core scanning, complemented by bulk organic geochemistry and X-ray diffraction mineralogy of catchment soil and lake sediments to reconstruct past climate and catchment processes. Phases of elevated sediment organic matter content (inferred from high Br and total organic carbon) suggest increased lake freshening and productivity, and coincide with increased chemical weathering (inferred from high Al/K and kaolinite/illite and feldspars), likely reflecting the influence of wetter climates. Conversely, periods of high Ca correlate with biogenic carbonate inputs typical of brackish conditions, which we attribute to drier climates or a marine influence. From 7.0 ka, at the mid-Holocene sea level highstand, until 5.7 ka, we suspect Lashmars Lagoon was under virtually continuous influence from the sea. At 5.7 ka, we interpret the abrupt increase in sediment total organic carbon to reflect the severance of the connection to the sea, allowing organic material to accumulate. This, coupled with evidence of high inferred chemical weathering, suggests the climate was relatively wet at the time. After 5.4 ka, our data point to the establishment of drier conditions until the commencement of wetter climates again at 4.5 ka. From 2.5 ka, however, drier climates prevailed again until present. Notably, the climate changes recorded in the sedimentary sequence at Lashmars Lagoon seem to be linked to the strength of the Leeuwin Current, a current that brings warm tropical waters to southern Australia and demonstrates a teleconnection with the El Niño Southern Oscillation, and may well have been an important driver of rainfall on Kangaroo Island (Karti/Karta) over the past ∼7000 years.

lake sediment
itrax
x-ray diffraction (xrd)
x-ray fluorescence (xrf)
weathering
hydroclimate


Reconstruction of the topographic evolution of the Nanling Range in South China and its implications for the East Asian Monsoon evolution

Abstract: The East Asian monsoon is the largest periodic airflow on Earth and significantly affects the climate of East Asia. However, considerable controversy exists about the onset timing of the East Asian monsoon. As one of the southern barriers blocking the northward movement of the warm and humid airflow, the Nanling Range has likely recorded key topographic information related to the East Asian monsoon onset and development. We used apatite and zircon (UTh)/He data obtained from the Shaoguan–Guidong horizontal cross-section to reconstruct the two-dimensional (2-D) paleotopography of the Nanling Range on a long-term scale. Four vertical profiles in Shulouqiu, Erjian, Sanfenshi, and Leiwangdian were used to constrain the exhumation history of the Nanling Range. The result revealed the following: 1) The drainage divide began to move from south to north at 80 Ma. At 80 Ma, the south segment of the cross-section reached a peak elevation of ∼3.6 km. The asymmetric topography experienced a rapid elevation (and relief) decrease from 80 Ma to 40–30 Ma. The four vertical profiles also experienced increased cooling and high exhumation rates from 100 Ma to 40–30 Ma. 2) The south segment experienced more rapid exhumation than the north segment from 80 Ma to 40–30 Ma. The rapid exhumation of the south segment during the Late Cretaceous–Paleocene is probably related to the activity of the Nanxiong Fault, and the rapid exhumation of the south segment during the Eocene probably results from the onset of the East Asian Monsoon.

low-temperature thermal history
topographic evolution
(uth)/he dating
nanling range
south china


Redox geochemical signatures in Mediterranean sapropels: Implications to constrain deoxygenation dynamics in deep-marine settings

Abstract: Global warming and anthropogenic activity are boosting marine deoxygenation in many regions around the globe. Deoxygenation is a critical ocean stressor with profound implications for marine ecosystems and biogeochemical cycles. Understanding the dynamics and evolution of past deoxygenation events can enhance our knowledge of present-day and future impacts of climate change and anthropogenic pressure on marine environments. Many studies have reconstructed the evolution redox conditions of past deoxygenation events using geochemical proxies. In this regard, the present work focuses on understanding the paleoenvironmental significance of geochemical redox signals derived from the onset, evolution and termination of regional-scale deoxygenations in deep-marine settings, with a specific focus on sapropels in the Eastern Mediterranean (EM). Sapropels, rhythmic organic-rich sediments deposited in EM, offer a unique opportunity to investigate recent deoxygenation events linked to past climate changes. Sapropels serve as paleo-archives of past deoxygenation events and can provide insights into the potential impacts of ongoing climate change on marine ecosystems and biogeochemical cycles. By integrating previous sapropel geochemical studies with a detailed analysis of new geochemical data from five Quaternary sapropels (S1, S5, S6, S7 and S8) in three different EM deep-marine settings, this study enhances our understanding of the paleoenvironmental significance of geochemical redox signals produced by deoxygenation dynamics and postdepositional processes in different deep-marine settings. The study supports that certain trace elements, such as Mo, V, U, Co, and Ni, are identified as more reliable redox proxies compared to Cr, Cu, Pb, and Zn. Four recurrent geochemical intervals attributed to specific redox conditions and postdepositional processes have been identified. Moreover, internal calibration of redox proxies thresholds has been performed and demonstrates how local environmental conditions (e.g., productivity rate) and hydrogeographic features (e.g., water-depth, particulate-shuttling intensity, deep-water renewal and fluvial input) play crucial roles in controlling the authigenic uptake rates of redox-sensitive trace metals, and subsequently, redox thresholds values of geochemical redox proxies. The results also emphasize the importance of postdepositional processes to accurately interpret geochemical signals in paleoenvironmental studies. This research enhances our overall understanding of geochemical signals associated with regional-scale deoxygenation events in deep-marine settings, offering new insights into predicting biogeochemical changes in marine environments undergoing a transition towards anoxia. By comprehending the dynamics of past and present deoxygenation, we acquire valuable knowledge regarding the potential effects of climate variability in marine ecosystems.

mediterranean
sapropel
deoxygenation
paleoredox
trace metal
inorganic geochemistry


Monsoon influence on plant diversity in northern Indochina: Evidence from the late Miocene Yen Bai flora, northern Vietnam

Abstract: Indochina, as a global biodiversity hotspot, offers the potential for understanding the evolution of biodiversity. However, the historical narrative of plant diversity in this region remains enigmatic due to limited fossil records. Here, we report a newly discovered megafossil flora from the late Miocene of the Yen Bai Basin, northern Vietnam. This megafossil flora suggests that the late Miocene vegetation in northern Vietnam comprised mixed tropical evergreen and deciduous broadleaved forest components mainly characterized by Fabaceae, Fagaceae, and Lauraceae bearing strong resemblance to the modern vegetation in northern Vietnam. Paleoclimate reconstruction for this plant fossil assemblage using the Coexistence Approach indicates a mean annual temperature (MAT) of 18.5–23.0 °C and a mean annual precipitation (MAP) of 1183.1–2078.5 mm. Similarly, employing the Climate-Leaf Analysis Multivariate Program yields an MAT of 21.3 ± 2.3 °C and a growing season precipitation (GSP) of 1328.6 ± 606.0 mm. The length of the growing season was about eleven months. Overall these results indicate a modern-like warm and humid tropical monsoon climate in northern Vietnam during the late Miocene. Climatic comparison of the Yen Bai with other fossil floras in northern Vietnam and southern China reveals the relative stability of temperature seasonality since the middle Eocene but obvious long-term variation in precipitation seasonality, particularly in respect of precipitation during the three consecutive driest months (X3.DRY). This suggests the Asian monsoon in northern Vietnam underwent important changes from the middle Eocene to the late Miocene, and intensified significantly during the middle and late Miocene. Our results show the modernization of plant diversity in northern Indochina had its origin in the Paleogene and further developed in the late Miocene, and was linked to the evolution of the Asian monsoon mainly in terms of changes in dry season precipitation.

asian monsoon
indochina
neogene
paleoclimate
red river fault zone
yen bai basin


Intensive chemical weathering in the Arctic during the Miocene Climatic Optimum

Abstract: The Arctic today has shallow, chemically immature, and frost-dominated weathering regimes. At Sokli, Finland (68°N), a 70 m deep palaeo-weathering profile is developed in a Devonian carbonatite pipe that represents fundamentally different past weathering environments. Formation of the apatite-francolite P-ore likely began under Palaeogene warm, humid climates. Later, cryptomelane (K-Mn oxide) crusts developed within the ore that have yielded peak 40Ar/39Ar ages of 16.20 ± 0.13 Ma (2σ)., The crusts formed at the redox front during the Miocene Climatic Optimum (∼16.9–14.7 Ma) under mean annual temperatures ∼12–14 °C warmer than today. The presence of the cryptomelane crust at shallow depth (15 m) indicates very low erosion rates since formation, consistent with its position on a tectonically stable Archaean craton and in the cold-based ice-divide zone of successive Fennoscandian ice sheets. The Miocene Climatic Optimum triggered a pulse of intensive weathering in mid- and low latitudes; the Sokli cryptomelane ages demonstrate that intensive chemical weathering extended into the Arctic.

miocene climatic optimum
weathering
arctic
cryptomelane
climate change


Porcelaneous larger foraminiferal responses to Oligocene–Miocene global changes

Abstract: Sea surface temperatures (SST) have been identified as a main controlling factor on larger benthic foraminifera (LBF) living in tropical to sub-tropical shallow-water carbonate and mixed siliciclastic‑carbonate platforms. Changes in SST, along with those in ocean acidification and nutrient content recorded in the global oceans throughout their history will not only continue but also be amplified in the future at an unprecedented rate of change possibly reaching levels found in the geological record. This study focuses on the Oligocene (mean SST 8 °C higher than present) and the Miocene (SST 5–8 °C higher than present) epochs which were characterized by a higher richness in porcelaneous LBF (pLBF) than today. A systematic re-assessment and comprehensive literature survey of stratigraphic ranges and palaeogeographic distribution in the Western Tethyan (Mediterranean) and Indo-Pacific regions are used to evaluate the impact of changes in SST, seawater pCO2 and pH on the biodiversity of the Oligocene–Miocene pLBF Alveolinella, Austrotrillina, Borelis, Bullalveolina, Flosculinella, and Praebullalveolina. Two peaks in species richness were identified during the Aquitanian and Langhian–Serravallian. These peaks occurred when SST was ∼29 °C, with pCO2 of ∼400 ppm and pH > 7.8. These values are comparable to those of today. The minima in species richness recorded in the Rupelian–early Chattian, in the Burdigalian and from the Tortonian onward can be correlated to the detrimental effects of both minimum (< 26 °C) and maximum (> 31 °C) SST thresholds. High pCO2 (> 600 ppm) values, which are limited to the Rupelian–early Chattian, are also detrimental to species richness. Seawater pH higher than 7.7 did not negatively affect species richness. These historical trends have serious implications for the future diversity of pLBFs with the increasing likely scenario of rising SST and pCO2 and lowering of pH values in the near future. These developments can potentially lead to diversity decrease and even extinction of pLBFs. However, the resilience of present-day pLBF species to rising SST and pCO2 levels is underpinned by the evolutionary histories of their fossil counterparts during climate variations, albeit at much different rates of change.

oligocene–miocene
larger foraminifera
western tethys
mediterranean
indo-pacific
ocean acidification
marine biodiversity


Paleoenvironment and paleoecology associated with the early phases of the Great American Biotic Interchange based on stable isotope analysis of fossil mammals and new U–Pb ages from the Pampas of Argentina

Abstract: The analysis of stable isotopes in fossil mammals is useful for reconstructing paleoenvironmental and paleoecological conditions, but has been rarely applied to the Neogene of South America. In this study, we perform an integrative analysis (including U–Pb zircon dates and mammalian stable isotopes data) for the Late Miocene–Early Pliocene of central Argentina. We provide radioisotopic ages for some classic fossiliferous localities in this region, including an age of 9.7 ± 0.3 Ma for Arroyo Chasicó and 4.5 ± 0.2 Ma for Farola Monte Hermoso, and address the interval covering the Chasicoan (Late Miocene), Huayquerian (Late Miocene–Early Pliocene), and Montehermosan (Early Pliocene) stages/ages. In the Chasicoan Stage/Age, taxa with mixed C3–C4 diets are recorded, suggesting the existence of favorable conditions for the C4 photosynthetic pathway before its full expansion. However, taxa represented across most of the Huayquerian Stage/Age show a preference for C3–based diets, which changes in the latest Huayquerian–Montehermosan stages/ages when an increase in the percentage of C4 plants in the diet of notoungulates, rodents, and xenarthrans is recorded, coinciding with the global expansion of C4 plants. For the first time, the dietary behavior of two South American endemic sparassodont metatherians (Lycopsis and Thylacosmilus) has been evaluated from using stable isotope; analysis of these hypercarnivores show differences in δ13C values, suggesting prey partitioning, partly due to the difference in body size. The fossiliferous sites studied, and the new isotopic and chronological information obtained, provide more detailed paleoecological and paleoenvironmental contexts for the Argentine Pampas during the last stages of the isolation of South America and the first pulses of the Great Biotic American Interchange. In addition, the new ages allow to better adjust the arrival of the first Holarctic immigrants in the region.

carbon
oxygen
radiometric dating
miocene
pliocene
south america


Contrasting patterns of Last-deglacial and Holocene precipitation between the southern and northern portions of Arid Central Asia

Abstract: The north-south migration of prevailing westerly system shapes the seasonality of modern precipitation in Arid Central Asia (ACA). The temperate continental climate with warm-season precipitation dominates the northern ACA and the Mediterranean climate with cold-season precipitation dominates the southern ACA. However, the north-south contrasts of precipitation/moisture for longer time scales remain unknown. In this study, we quantitatively reconstructed the precipitation sequence covering the past  14.4 cal. kyr BP based on pollen data obtained from Shayan loess section in southern ACA using MAT (Modern Analogue Technique) method. Our reconstruction shows that the precipitation had an increasing trend from  14.4 to  8.2 cal. kyr BP and a decreasing trend from  8.2 to  1.5 cal. kyr BP with the past 1500 years being characterized by an averagely high precipitation. The precipitation trend in southern ACA was rather different from that in northern ACA where the precipitation has increased more or less constantly since the late deglaciation. The contrast between southern and northern ACA appears to have been associated with the south-north migration of westerlies that was accompanied with alterations of NAO (North Atlantic Oscillation) phases and also with changes in strengths of Siberian High and ENSO (El Nino-southern Oscillation).

loess
pollen
modern analogue techniques
precipitation
last deglaciation
arid central asia


Barnacle-rich facies as a tool for palaeoenvironmental reconstructions

Abstract: Palaeoenvironmental data are fundamental in determining the manifold impacts of climate change. This paper argues that sessile barnacles are an excellent palaeoenvironmental proxy: they are present in nearly all nearshore environments, and their shell consists of diagenetically stable low-magnesium calcite and grows fast enough to record short-term variations. To demonstrate their utility, specimens from several Western Mediterranean Pliocene and Pleistocene barnacle-rich deposits are analysed herein, using for the first time a combination of sedimentology, taphonomy, stable isotope geochemistry and detailed comparisons with modern counterparts. Within shelf carbonate systems, barnacle diversity is highest in the shallow, nearshore waters and decreases moving offshore, thus providing a good proxy for the reconstruction of water depth and distance from the coastline. Barnacle taphonomy is also informative. Well-preserved complete specimens are characteristic of protected areas, whereas less well-preserved specimens occur in high-energy areas. The presence/absence of opercular plates is also particularly relevant for evaluating hydrodynamic conditions. As regards the C and O stable isotope ratios, due to the porous and coarse-grained nature of the deposits in which barnacle remains are usually found, the shells are often exposed to meteoric water percolation during diagenesis. Among the analysed specimens, only those collected from fine-grained deposits display no evidence of alteration and have isotopic ratios in line with those of their modern counterparts. These fossils display intra-shell variations that in modern barnacles have been related to short-term environmental changes (e.g., seasonal cycles). These results demonstrate that barnacles can always be useful for detailed palaeoenvironmental reconstructions based on skeletal assemblages. Furthermore, with further research aimed at gathering more data and assessing potentially interfering signals, they could become useful proxies for palaeoseasonality.

pliocene
pleistocene
stable isotope geochemistry


Fluctuations of aquatic macrophytes in a shallow lake in eastern China over the last 1800 years: Evidence from n-alkanes

Abstract: To address the threats of global warming and human activities to freshwater shallow lake ecosystems, it is imperative to comprehend the long-term evolutionary history of lake ecosystems under external forces. However, short-term records are insufficient to distinguish the effects of climate change and human activities. This study applied n-alkanes in a sediment core retrieved from Lake Nvshan in the Huai River basin in eastern China to investigate ecological changes over the past 1800 years. Carbon isotope compositions of long-chain (C27–31) n-alkanes revealed that they were mainly derived from floating and submerged plants, which enabled us to monitor the evolution of aquatic macrophytes in lake sediments. Prior to the Little Ice Age, the growth of floating and submerged plants in Lake Nvshan declined steadily, but underwent a significant expansion afterwards. Before ∼1400 CE, the development of aquatic macrophytes was controlled by the hydrological condition, which regulated nutrient supply from the watershed. After 1700 CE, however, anthropogenic activities became the dominant factor influencing the evolution of lake macrophytes, leading to an increase in erosion and nutrient input, potentially resulting in a shift from submerged plants to a system dominated by floating plants and algae. This research emphasizes the effect of various stressors on the long-term development of lake macrophytes, and provides insight into how freshwater shallow lakes can be safeguarded in the face of global changes.

lake ecosystem
-alkanes
macrophytes
paleolimnology
compound-specific carbon isotope


Sedimentary evidence for the diversion of the Yellow River onto the North China Plain 3000–2600 years ago

Abstract: The lower Yellow River is characterized by frequent channel avulsion and flooding during the late Holocene, which not only shaped the geomorphic landscape of the North China Plain, but also modified the preexisting drainage network and affected human settlement pattern. The channel evolution of the lower Yellow River during historical periods of China has been well known from documentary records. However, it is still unclear about the drainage pathway of the river during the archaic period of Chinese history. Here we show sedimentary evidence for a dramatic channel displacement of the lower Yellow River about 3000–2600 years ago. Our multi-proxy analyses indicate that the first prehistoric diversion of the Yellow River occurred around 3000 yr B.P. and the river flowed northward into the Bohai Sea through the foreland depression along the eastern foothill of the Taihang Mountains. Frequent floods thereafter not only led to the widespread infilling of depressions in the lower reaches of the Yellow River and thus accelerated the formation of the North China Plain, but also drove humans to migrate from the piedmont area of the Taihang Mountains to the hinterland of the central North China Plain.

yellow river
channel avulsion
drainage pattern
north china plain
late holocene


Upper Triassic (middle Norian) conodont biostratigraphy succession from Qamdo, eastern Tibet

Abstract: The Late Triassic is a critical period that witnessed major biological and environmental events. The geographic range and taxonomic diversity of conodonts were significantly changed during the Late Triassic, with the geographic range contracting prior to complete extinction of the group near the end of the Triassic. In the present study, we recognize for the first time a continuous middle Norian (Upper Triassic) conodont succession from the Qamdo (Changdu) area, eastern Tibet (Xizang), which was part of the North Qiangtang and Qamdo-Simao Block (NQ-QSB) located in the northeastern Tethys Ocean during the Late Triassic. Four conodont zones are established from the middle Norian (Alaunian) of the Chaiwei section in Qamdo, and in ascending order these are: the Epigondolella spiculata Zone, the Orchardella elongata Zone, the Mockina postera Zone, and the E. serrulata Zone; the neighboring Tuoba section also records these four zones, in addition to the upper lower Norian (upper Lacian) Ancyrogondolella uniformis Zone. All of these zones (except for the M. postera Zone) have been recognized for the first time in eastern Tibet. The Lacian-Alaunian boundary is tentatively placed at the level of sample CW-3 at the Chaiwei section and at the level of sample TBL-36 at the Tuoba section by the first occurrence (FO) of E. spiculata in each section. The position of the Alaunian-Sevatian boundary (ASB) is uncertain since the conodont assemblage from the top of the Bolila Formation at the study sections lacks age-diagnostic elements. The conodonts recovered from the Qamdo area have not only dated the Bolila Formation but also refined the conodont biostratigraphic zonation of the Alaunian in the study area. This allows improved correlation between the faunas of Qamdo and their counterparts elsewhere in Tibet and Europe, although the conodont zonations from these regions display lower precision than those established from North America. The Alaunian conodont faunas at Chaiwei and Tuoba appear to be dominated by juvenile specimens; this often appears to be the case in the Alaunian of the Tethyan Realm, but seems not occur in North America. This may suggest that the conodonts living in these two realms may have inhabited different ecological environments. The faunal turnover around the Lacian-Alaunian transition, with the evolution of Epigondolella, Orchardella, and Mockina from Ancyrogondolella, can be recognized in both study sections, although it is more remarkable in the Tuoba section. Although the lack of previous detailed studies of Norian conodont biostratigraphy from Tibet hampers correlation in this region and beyond, this study demonstrates the possibility of establishing high-resolution conodont biostratigraphic successions from Tibet in the future, since the conodont faunas recognized from Tibet and adjacent areas (e.g., Baoshan) suggest that relatively complete Norian strata exist in these regions. Overall, this study also provides new data to improve our understanding of conodont evolution during the Alaunian, and is significant in providing palaeontological data for studying the palaeogeographic evolution of eastern Tethyan ocean basins in the Late Triassic.

late triassic
conodont biostratigraphy
changdu basin
north qiangtang
tethys


Phosphorus cycling during the Hirnantian glaciation

Abstract: Unlike other mass extinctions of the Phanerozoic, the Late Ordovician mass extinction took place during an icehouse interval, accompanied by the glaciation of Gondwana. Ice sheets reached their maximum during the Hirnantian and global sea-level dropped substantially. Consequently, the shallow tropical shelf environments of Laurentia and Baltica became subaerially exposed or remaining submerged shelves were characterized by very shallow water-depths. Redox proxies suggest that most shallow shelf settings were well oxygenated to that time, while the global extent of anoxic environments increased, implying that deoxygenation was confined to the open ocean. We speculate that the burial rate of the nutrient phosphorus (P) on shelves was minimal during the Hirnantian glacial maximum (HGM) due to bypass of the shelves in respect to the incoming riverine dissolved load. Hence, a large excess of bioavailable P entering the open ocean would have stimulated phytoplankton production which lowered oxygen concentrations by aerobic respiration. In order to test this hypothesis, we determined reactive P (Preact) contents in two low-latitude carbonate successions (Anticosti Island and Estonia) spanning the HGM. Moreover, we measured total organic carbon (C) concentrations and calculated C/P ratios to evaluate the burial efficiency of P. Samples from both sites are characterized by overall low Preact contents. We observe a decreasing trend in Preact towards the HGM, reaching a minimum during the initial transgression thereafter. C/P ratios suggest efficient P-burial throughout the study interval and, hence, Preact contents are assumed to be a direct measure of primary productivity, P-availability, and P-burial. Using the Preact concentrations, we modeled shelf P-burial fluxes with estimates for global shelf area and sedimentation rates. The model suggests that shelf P-burial fluxes around the HGM were approximately halved due to a reduced shelf area and minimum Preact contents. With the assumption of a constant P-input to the ocean, the proposed scenario serves as a plausible explanation for the observed redox gradients.

phosphorus cycle
hirnantian
glaciation
primary productivity
sea level
anoxia


Climate-induced surface water variability at Monte San Nicola type-section (Sicily, southern Italy): New data across the Gelasian GSSP

Abstract: We present the first high-resolution results on planktonic foraminiferal stable oxygen isotopes and calcareous plankton assemblages at the Monte San Nicola GSSP section (near Gela, Sicily), the type-section for the Lower Pleistocene Gelasian Stage. The oxygen isotope profile is remarkably similar to the Eastern Mediterranean oxygen isotope record and indicates that the studied section, extending from marine isotope stage (MIS) G4 to MIS 103, clearly records glacial-interglacial variability. Cyclic changes of calcareous plankton assemblages (calcareous nannofossils and foraminifera) indicate that warmer and stratified surface waters occurred during interglacials, while cooler and unstable conditions developed during glacial phases. Signatures of further increase in surface water stratification are also captured by our surface water proxies and are coeval with enhanced monsoon run-off, developed during precession minima/insolation maxima. The surface water changes recorded at the Monte San Nicola section are in phase with North Atlantic climate variability, even at suborbital scale, and reveal evidence of the first significant southward migration of the Subarctic Front in the mid-latitudes during MIS 104, slightly below the GSSP. The overall dataset provides precise alignment of the Gelasian GSSP within MIS 103 as well as new climatostratigraphic constraints, close to the GSSP, thus improving its correlation potential outside the type-area.

lower pleistocene gssp
mediterranean area
stable oxygen isotope
calcareous plankton
paleoclimate
north hemisphere glaciation


Permian post-orogenic terrestrial successions in the western and northern peripheral orogens of the Junggar Basin: Records of sedimentary provenance, paleogeographic and tectonic changes

Abstract: The Permian terrestrial successions were deposited in peripheral orogens of the main Junggar Basin, including the West Junggar and Chinese Altai orogens. These successions probably marked the termination of the Paleozoic orogeny in the SW Central Asian Orogenic Belt and document paleogeographic and tectonic changes during that time. However, comprehensive research of these successions is still lacking. This study investigated representative sections and outcrops of Permian successions in West Junggar and Chinese Altai, and we present a detailed sedimentological comparison in the specific chronological framework according to new zircon U-Pb ages of syn-depositional volcanics. This comparison shows that the Lower Permian successions consist of almost equal amounts of sedimentary rocks (46–56

post-orogenic sedimentation
permian terrestrial succession
provenance analysis
paleogeographic pattern
west junggar
chinese altai


Miocene ant species of the genus Forelius Emery, 1888 (Hymenoptera: Formicidae: Dolichoderinae) from Mexico

Abstract: The first fossil ant species of the New World genus Forelius (Formicidae: Dolichoderinae) is described. The type material is a Miocene amber inclusion from the Montecristo mine near Simojovel, Chiapas, southwestern Mexico. The new species is named Forelius chenpauch sp. nov. It differs from its congeners by having a unique combination of characters: antennal scapes reaching the posterior margin of the head; pronotum with six erect hairs; mesonotum with four erect hairs; propodeum with four erect hairs; front and dorsum of head, dorsum of pronotum, dorsum of mesonotum and propodeum covered with a fine striation. Forelius chenpauch sp. nov. has a rounded spiracle, which could be considered a plesiomorphic character closely related to the Forelius group from the north of the Amazon basin. Accordingly, the current divergence estimates of Forelius as a single genus from the Leptomyrmex + Forelius + Dorymyrmex clade (ca. 27 Ma) and the occurrence of Forelius chenpauch sp. nov. in the fossil record (ca. 23 Ma), may suggest that the rounded spiracle is a plesiomorphic state probably widespread since the Miocene from southern Mexico to northern South America.

ant fossil
amber-lagerstätte
chiapas amber
leptomyrmecini tribe
new species


Two exceptional Balaenomorpha (Cetacea: Mysticeti) from the Biemenhorst Subformation (middle/late Miocene) of Bocholt (W Münsterland, Germany) with a critical appraisal on the anatomy of the periotic bone

Abstract: Here we present two new Miocene basal balaenomorph mysticetes recognized by periotic bones with a unique combination of characters. The fossil periotics originated from former shallow marine sediments and were discovered in a suburban quarry of Bocholt in the German Münsterland holding a number of remains of a multispecies community of mysticetes. A detailed accompanying analysis of the internal and external structures of mysticete periotics resulted in a critical review and revision of two important characteristics of the pars cochlearis. The partition between the openings for the facial nerve and the vestibulocochlear nerve, named here ‘bony septum’ for baleen whales, has been developed so prominently during mysticete evolution that the crista transversa is no longer recognizable in derived forms, as it lies deep inside the inner ear canal and within the fundus of the internal acoustic meatus where it separates the cochlear nerve from the inferior vestibular nerve. We show that the designation of the opening for the superior vestibular nerve as ‘foramen singulare’ is misleading since this term describes the opening for the nerve to the posterior semicircular canal within the fundus of the internal acoustic meatus.

diorocetidae
breda formation
iam
bony septum
crista transversa


Miocene decapod crustacean faunas from Cyprus – Part 1. Geographical-stratigraphical setting and Anomura

Abstract: Study of high-diversity Miocene decapod crustacean faunas has resulted in the recognition of several new species from a range of localities across Cyprus. Anomuran taxa collected comprise Paguristes joecollinsi, Dardanus cyprioticus sp. nov., Dardanus plevrotos sp. nov., Galathea weinfurteri, Palmunidopsis muelleri, Petrolisthes haydni, Petrolisthes magnus and Petrolisthes mitseroensis sp. nov. The presence of Petrolisthes magnus in upper Chattian-middle Burdigalian strata documents the oldest stratigraphical occurrence of that species to date. Anomuran taxa recognised in the lower Miocene are also present in upper Miocene reefal facies; the latter illustrate the highest anomuran diversity.

mediterranean sea
cenozoic
paguroidea
galatheoidea
new species


Report from the 8th Symposium on Fossil Decapod Crustaceans, Zaragoza (Spain), June 2022

Abstract: Decapod crustaceans are an important component in modern ecosystems with a rich fossil record spanning more than 400 million years. Last summer (19th-24th June 2022) the 8th Symposium on Fossil Decapod Crustaceans took place in Zaragoza (Spain), a meeting covering all aspects of studies on fossil decapod crustaceans, including information from modern representatives. The Symposium was organized by the Spanish Research Council (CSIC) and the University of Zaragoza with collaboration of organizers from universities of the Basque Country, Alabama, and Barcelona, and the support of the regional Government of Aragón.

decapoda
mesozoic
cenozoic
evolution
field trip


Bioerosion traces on the Campanian turtle remains: New data from the lagoonal deposits of the Quseir Formation, Kharga Oasis, Egypt

Abstract: The uppermost part of the Campanian Quseir Formation of Kharga Oasis, Egypt, contains a concentration of turtle skeletal remains in a lagoon setting. They appear as three successive horizons (I‒III), alternated between the variegated shales and the glauconitic mudstones and conglomeratic layers within the Hindaw Member. However, bones recovered in horizon III present a higher preservation potential than the others. Therein, turtle remains are represented by mostly complete shells, partial shells and many scattered and weathered shell fragments. The studied turtles lived in small ponds and marshes and were deposited as autochthonous to parautochthonous relics. Their bones display significant bioerosion signatures on both carapace and plastron. The morphological analysis of the bioerosion structures preserved revealed 11 ichnospecies, belonging to nine ichnogenera. Eight of these ichnotaxa are recorded for the first time in turtle bones of Egypt. The recognised bioerosional structures appear as borings, shallow chambers, grooves, and punctures produced by ticks, beetles, polychaete worms, fishes/crocodile, and gastropods. They were attributed to the ichnogenera Karethraichnus, Cubiculum, Osteocallis, Radulichnus, Osteichnus, Osedacoides, Sulculites, and Machichnus. In addition, some bite marks assigned to Nihilichnus also occur on a carapace peripheral. This grade of bioerosion was likely caused by relatively long exposure time before the final deposition or burial. In some cases, borings may be produced during the host’s lifetime. The new material considerably expands the stratigraphic and geographic distribution of this trace fossil assemblage and reveals that their producers may have been able to survive in other palaeoenvironmental conditions.

turtles
bioerosion
trace fossils
campanian
kharga oasis
egypt


Forelimb motion and orientation in the ornithischian dinosaurs Styracosaurus and Thescelosaurus, and its implications for locomotion and other behavior

Abstract: The range of motion (ROM) in the forelimb has previously been studied in many saurischian dinosaur species but only a few ornithischian dinosaur species. Here, we fill in some of the blanks in current knowledge of ornithischian forelimb function by investigating the range of shoulder motion and the orientation of the humerus, radius, and ulna in the centrosaurine ceratopsid Styracosaurus albertensis and the basal ornithopod Thescelosaurus sp. Manual manipulation of forelimb bones, using the margins of bony articular surfaces to delimit the range of motion, shows that humeral ROM and forearm orientation in S. albertensis resemble those previously found in chasmosaurine ceratopsians. Locomotion occurred with the elbows tucked in at the sides and with the radius anterior to the ulna, without pronation. The animal was also capable of splaying its forelimbs with the elbows strongly everted, so that elbow flexion and extension produced side-to-side or up-and-down movements of the torso and head. Thescelosaurus sp. had limited humeral ROM and could not swing its humerus forward through the parasagittal plane as far as a vertical orientation. While being swung upward through the transverse plane, the humerus could not move as high as a horizontal position. Skeletal proportions and spinal curvature indicate that the forelimbs of Thescelosaurus could contact the ground while the animal stood. However, the animal is unlikely to have used quadrupedal locomotion, because its palms faced medially, and its fingers would have flexed through the transverse plane and therefore would not have provided forward propulsion.

styracosaurus thescelosaurus ceratopsia ornithopoda ornithischia forelimb


An overview of crawling water beetle larvae and a first possible record from 100-million-years-old Myanmar amber

Abstract: The group Coleoptera contributes heavily to the modern-day species diversity and biomass. Most individuals in the modern fauna are present as larvae, since these live for quite long in some cases, and a lot of individuals never reach adulthood. Despite this fact, the larval stages often get less attention compared to the adults. The group of crawling water beetles, Haliplidae, is an ingroup of Adephaga, living mainly in freshwater as adults. The larvae also live in water, but do not swim like the adults; instead, they move over the surface of the ground and climb on water plants. The larvae develop through three larval stages; all have an elongated shape, and in most species the trunk end is strongly elongated, bearing numerous setae. Herein, we review the entire record of water crawling beetle larvae, report possible fossils, and compare the shape of their overall body outlines using an elliptic Fourier analysis. The fossils show a lower variation in comparison to modern fauna; the shapes of the fossils are well represented in the modern fauna. A minor difference is rather elongate thorax segments of the fossils in comparison to their extant counterparts. The new fossils expand the record of fossil adephagan larvae.

haliplidae
coleoptera
cretaceous
diversity
burmese amber
larva


A fossil locality predictive model using weighted suitability analysis for the Early Cretaceous Cedar Mountain Formation, Utah, USA

Abstract: Hard work and chance are nearly always among the deciding factors in finding new, important, and productive paleontological localities. Fossil locality predictive models have the potential to maximize field time and increase chances to find important localities. This study uses remotely sensed data to design and test a fossil locality predictive model for the Early Cretaceous Cedar Mountain Formation. Landsat 8 OLI/TIRS data from known localities were summarized, reclassified, and used in a weighted suitability analysis to categorize fossil locality potential of the study area. Field work was conducted to test model functionality. Field observations were used to refine the weighted suitability analysis. Landsat 8 OLI/TIRS data alone offers a less accurate prescription of fossil locality potential. Additional physical and environmental factors play a role in determining the chance of finding fossils. Slope degree and aspect data from known localities were summarized and analyzed to further refine the model. Forty percent of existing fossil localities within the final model boundaries were located on areas having the highest fossil locality potential as identified by the model. The usefulness of fossil locality predictive models is dependent upon the quality of input data and methods used to determine fossil locality potential. To fully determine the quality of a fossil locality predictive model, field testing is ideal.

cedar mountain formation
gis
predictive model
landsat 8
remote sensing
weighted suitability analysis