Late Paleozoic Ice Age Research Articles

A short-term warming interval during the apex of the late Paleozoic Ice Age: Evidence from geochemical and magnetic records from South China

The Late Paleozoic Ice Age (LPIA) was the longest-lasting icehouse in the Phanerozoic. Previous studies indicated a climate warming interval in the earliest Permian—an apex of the LPIA. To better understand hydroclimatic changes and carbon cycling within this time interval, we conducted a series of high-resolution geochemical and rock magnetic analyses, including magnetic measurements (e.g., magnetic susceptibility, anhysteretic remanent magnetization, hysteresis loops, temperature-dependent susceptibility), ratio of iron to potassium (Fe/K), and carbonate carbon isotope (δ13Ccarb) from a deep-marine section in South China. Calibrated to the published astronomical time scale, a negative δ13Ccarb excursion (−1‰) was identified during 298.4–297.9 Ma, and it was time-equivalent with the warming interval, recognized by a decrease in conodont apatite oxygen isotopes in South China, low-latitude sea-level transgression, and high-latitude deglaciation. The negative δ13Ccarb excursion also coincided with a magmatic pulse of the Skagerrak-Centered Large Igneous Province (LIP), indicating that the perturbation in carbon cycling is likely associated with the release of volcanic CO2. Furthermore, cyclostratigraphic analysis on multiple paleoclimatic proxies, including ferrimagnetic susceptibility, gamma-ray, and Fe/K, suggested that the negative excursion of δ13Ccarb also overlapped with the maximum of the eccentricity cycle. It implied that orbital configurations may amplify the feedback of the LIP, causing this short-term warming interval.

Late Carboniferous marine-continental transitional sediments in the Datong Basin, North China: Mineralogical and geochemical characteristics and paleoenvironmental significance

To understand the sedimentary paleoenvironmental changes in the marine-terrestrial strata of the Upper Carboniferous Taiyuan Formation in the Datong Basin of North China, we generated mineralogical and geochemical data of the Tashan and Emaokou mines in the eastern Datong Basin. The study strata vertically comprise kaolinitic claystones in the upper and lower parts and calcareous mudstones in the middle. The kaolinitic claystones are primarily composed of kaolinite and quartz, with a small amount of illite, feldspar and siderite, whereas the calcareous mudstones comprise mixed-layer illite/smectite (I/S) clay and carbonate minerals, with a minor amount of quartz, kaolinite, feldspar, and siderite. The paleosalinity indicators (B/Ga, Sr/Ba, and paleontological detritus) indicate that kaolinitic claystones are formed in freshwater, whereas calcareous mudstones are formed in marine water. The redox-sensitive trace element ratios (U/Th and Ni/Co) and trace metal enrichment factors (MoEF and UEF) indicate that kaolinitic claystone and calcareous mudstone formed under oxic and anoxic–suboxic conditions, respectively. Clay assemblages, chemical alteration index (CIA), and the Sr/Cu ratios show that kaolinitic claystones and calcareous mudstones were deposited under hot, humid, intense weathering conditions and warm, humid, and moderately weathering conditions, respectively. Based on these data and combined with previous studies, we conclude that transgressive events caused the changes in sediments in the study area, and the occurrence of transgressive events is related to the global glacio-eustatic fluctuation and paleoclimate changes during the Late Paleozoic Ice Age (LPIA). Our results are essential for unraveling the relationship between the study area and global paleoenvironmental changes during the LPIA.

First report of Early Permian Tasmanite oil shales in northern Pangea with global implications

During the Late Paleozoic Ice Age (LPIA; particularly early Permian), organic material of the alga Tasmanites was extensively deposited in sediments of southern Gondwana, which formed the Tasmanite oil shales that have only been identified in Tasmania, Australia. It remains unclear whether other analogous geological records exist worldwide that formed at the same time, and the origin is enigmatic. This paper reports the first discovery of Tasmanite oil shales in northern Pangea, specifically in the Lucaogou Formation of the Junggar Basin, China, deposited during the Artinskian (ca. 290 Ma). The organic petrological features of Tasmanites are clearly visible, including thick-walled disks with tubes and radially arranged channels. These shales have markedly elevated C28/C29 steranes and tricyclic terpanes/hopanes ratios. Based on inorganic geochemical data, the salinity of the paleo-lake during deposition of the Tasmanite oil shale interval decreased abruptly from saline to brackish–freshwater. In addition, the pH changed from alkaline to nearly neutral, while the redox environment changed from anoxic to suboxic. Enhanced continental chemical weathering and the change in salinity of the paleo-lake occurred at the same time as global warming and large-scale glacier melting during the Artinskian, which promoted the habitat of the low-salinity tolerant Tasmanites. Our results provide new geological evidence for another occurrence of early Permian Tasmanite oil shales, indicating that Tasmanites flourishs and the associated oil shales may have been widely deposited at the end of the LPIA. The flourishment of Tasmanites archives biotic–environmental co-evolution.

Stratigraphic distributions of biomarkers and carbon isotopes in coals constrain the Permo-Carboniferous climatic changes and floral turnovers in the north China block

The intricate relationship between climate and vegetation dynamics, particularly during the late Paleozoic ice age marked by multiple icehouse-greenhouse transitions, is a compelling aspect in Earth's historical narrative. In this study, we decipher the interactions between the Permo-Carboniferous climate fluctuations and floral turnovers within the North China Craton, based on the stratigraphic distributions of biomarkers and carbon isotopes from cored coals in Huainan coalfield, North China. Our findings reveal that the changes in n-alkane, terpane, sterane, and polycyclic aromatic hydrocarbon (PAH) distributions result from a confluence of maturation, depositional environment, and organofacies effects. Molecular maturity-sensitive ratios align with the maturity stage determined by Rock-Eval pyrolysis and petrography, categorizing the coals as high volatile bituminous A/B with a composite organic matter derived from terrestrial plants and marine algae. Notably, the 18α-22,29,30-trisnorneohopane (Ts) to 17α-trisnorhopane ratio (Ts/(Ts + Tm)), as well as C31–C34 22S/(22S + 22R) hopanes and C29 20S/(20S + 20R) steranes ratios exhibit moderate correlations with %Ro, indicative of epimerization reactions induced by maturation processes. The stratigraphic variations in pristane to phytane ratios (Pr/Ph), Pr/n-C17, Ph/n-C18, C30 αβ/(αβ+βα) hopanes, and organofacies sensitive PAH indices collectively capture a paleoenvironmental shift from reducing to oxic conditions attributed to marine regression. The systematic changes in PAH concentrations and their maturity indices reflect condensation and dealkylation reactions during the maturation process. The δ13C signature manifests a negative excursion in coals of the Artinskian Shanxi Formation and a subsequent positive excursion in the Capitanian Upper Shihezi Formation coals, respectively, reflecting changes in the δ13C values of contemporaneous atmospheric CO2 in response to regional aridity fluctuations.

Provenance shifts in bauxitic clay from Zibo, North China Craton, links tectonics and climate to environmental perturbation

Abstract In the eastern North China Craton, the Zibo bauxitic clay deposits are situated between Permian sandstones. These deposits exhibit distinct characteristics in two horizons. The lower horizon consists of disordered kaolinite with anhedral–subhedral, rounded morphologies that indicate a detrital origin. The upper horizon, however, contains ordered kaolinite. Detrital zircon grains in the lower horizon indicate a unimodal age spectrum with a mean age of ca. 290 Ma and εHf(t) values ranging from −20.8 to −6.0. These findings suggest a continental volcanic arc source on the northern margin of the North China Craton. In contrast, detrital zircon grains in the upper section exhibit a multi-modal detrital age spectrum with significant age peaks at 2500 Ma, 1850 Ma, and 310 Ma that originates from the local basement. The zircon dating establishes a maximum depositional age of ca. 280 ± 3 Ma, which indicates denudation of the source area in the northern North China Craton during the Artinskian stage. The relative abundance of detrital kaolinite indicates a warm and humid climate during the late Artinskian (ca. 283 Ma) to Early Kungurian (ca. 280 Ma), while cold and dry conditions prevailed during the mid–late Kungurian (ca. 277 Ma). The northern North China Craton, which supplied source material to the lower section of Zibo bauxitic clay, experienced rapid uplift and exhumation and underwent intense weathering under high humidity and warm temperatures during the late Artinskian to Early Kungurian. However, the source area shifted from the north to a more central region as the climate transitioned to cold and dry conditions in the mid–late Kungurian. Considering that detrital clay formation is indicative of specific climatic conditions, the Permian bauxitic clay deposits in Zibo provide a valuable record of environmental changes during the late Paleozoic ice age (LPIA; ca. 360–260 Ma).

Paleogeographic records of glacial and terminal glacial palynozones related to the Late Paleozoic Ice Age in the Brazilian portion of the Paraná Basin, Western Gondwana

Among the four palynozones established for the Pennsylvanian–Permian sedimentary succession of the Paraná Basin, two are related to the glacial (AcZ: Ahrensisporites cristatus and CmZ: Crucisaccites monoletus zones) and one is related to the following terminal glacial phase (VcZ: Vittatina costabilis Zone) in this portion of Gondwana. The AcZ and the CmZ are typically recognized within the basal and middle portions of the Itararé Group and the Aquidauana Formation, while the VcZ corresponds to the upper portions of both units. In this paper we present a palynostratigraphic analysis of all occurrences of these palynozones from 66 boreholes and 29 outcrops. Two paleogeographic maps are depicted showing the distribution of all sections where the palyonozones related to glacial and terminal glacial sections occur within the Itararé Group and the Aquidauana Formation. Glacial palynozones (AcZ and CmZ) are recognized from outcrops and boreholes from Santa Catarina, Paraná, São Paulo, Mato Grosso do Sul, Mato Grosso and Goiás states, encompassing the thickest portion of the Itararé Group and the Aquidauana Formation. The terminal glacial palynozone (VcZ) was recognized from several boreholes and outcrops, well distributed throughout the basin, from the Rio Grande do Sul, Santa Catarina, Paraná, São Paulo and Mato Grosso do Sul states. Reworked palynomorphs from Devonian and Mississippian strata found together with indigenous species in assemblages assigned to the glacial palynozones (AcZ and CmZ) are used herein as a tool for interpretation of the source area and as indicators of transport direction. As observed elsewhere in Gondwana, palynozones related to the glacial and terminal glacial phases present dominance of spores and monosaccate pollen grains, whereas those linked to the latter phase record the income and the quantitative increase of certain species indicative of progressive climate amelioration. Further sedimentary and stratigraphical aspects are also discussed.

Enhanced Denudation of the Emeishan Large Igneous Province and Precipitation Forcing in the Late Permian

AbstractHydroclimate is an important factor controlling landscape evolution. But establishing the impact of hydroclimate is complicated by the influences of other processes and is especially hard to prove for those in deep time from geological record. During the late Permian, voluminous basaltic sediments were derived from the erosion of the Emeishan large igneous province in western South China. They provide a unique record critical in understanding the responses of tropical basaltic erosion to hydroclimate change without impacts of orogenic uplift, lithologic variation, vegetational difference and glacial‐interglacial change. Sampled successions define a negative carbon isotope excursion capable of making regional and global stratigraphic correlations in the middle Wuchiapingian interval corresponding to the final phase of the late Paleozoic ice age. This interval is associated with a petrofacies shift and a decreasing source weathering intensity, a downward shift of erosion loci, and a reduced coastal water paleosalinity. Applying present‐day temperature dependence pattern of basaltic weathering and using land surface temperatures approximated from nearby paleo‐seawaters, denudation rates were calculated for the Emeishan basaltic province and shows an increase from ∼71 to ∼107 m/Ma. This erosional acceleration is temporally correlated with a decrease in paleosalinity and likely linked to enhanced freshwater discharge in the middle Wuchiapingian. Scaling and landscape erosion modeling suggest ∼80%–130% increase in catchment precipitation could have driven this acceleration in denudation. Our work provides a positive test for the hydroclimate forcing on landscape erosion in deep time and underlines the mechanistic linkage of sediments with erosion and climate change.

Palynological analysis (biochronostratigraphy and paleoenvironments) from a fossil-Lagerstätte section within the Late Paleozoic Ice Age unit of the Paraná Basin (Itararé Group), Western Gondwana

A diverse and exceptionally preserved fossil association occurs in Campáleo Outcrop black shales of the upper Itararé Group, correlated to the Lontras Member, considered representative of the Pennsylvanian–Permian transition in the Paraná Basin, Brazil. In this paper, we present the palynological records from 20 stratigraphic horizons of these shales and related strata, which revealed 21 taxa of spores, 33 of pollen grains, two species of fungi, one species of Chlorophyceae and two species of Prasinophyceae. The section is correlated to the Vittatina costabilis Zone, due to the records of certain guide species, such as Converrucosisporites confluens, Illinites unicus and several species of Vittatina. An additional subsurface section (TC-4 core) partially correlated with the Campáleo Outcrop and comprising the passage of the Crucisaccites monoletus and Vittatina costabilis palynozones was also studied in order to support the stratigraphic positioning. Once combined with the stratigraphic positioning in the basal portion to the Lontras Shale, it allows us to consider it around the Pennsylvanian–Permian boundary, probably in the Gzhelian to age of the Campáleo Outcrop. We observed distinct palynofloristic compositions from (i) the rhythmic shale with dropstones (basal portion) and from (ii) the fossiliferous black shales (upper portion). The former presents a large dominance (about 90 %) of pollen grains (xerophylous elements) and low frequency (about 7 %) of spores (meso-hygrophylous), while the results of the latter are conversely. Marine palynormorphs were recorded herein only from the rhythmic shale. The palynological assemblages on the base of the Campáleo Outcrop demonstrated a more intense sediment supply, bringing sporomorphs from more distant regions being represented mainly by xerophylic flora, indicating the existence of regions devoid of ice cover, where forests could develop, as occur in seasonal climate regions. The upper level of the Campáleo Outcrop characterizes one of the predominance of spores (hygrophylic communities) in these palynological associations supported by the large number of insects found that indicates proximity to the coastline, little transport (spore tetrads), poor contribution of more distant continental sediments (low expressiveness of pollen grains) and low salinity water, due to the absence of marine palynomorphs, representing a reducing restricted marine environment. This data integrated with the stratigraphic context and other geological data evidenced changes in sea level due to the climatic oscillations in the course of the LPIA that influenced the sediment supply and the distance of the coastline in this region of the Paraná Basin.

Tracking the Eurydesma Fauna transgression across southwestern Gondwana

The cold water Eurydesma Fauna, consisting of bivalves, brachiopods, and scarce gastropods, has been associated in several basins of Gondwana with the terminal phase of the Late Paleozoic Ice Age (LPIA). The Eurydesma Fauna-bearing transgression has been identified in basins of South America and southern Africa. In western Karoo Basin of South Africa four phases of ice growth and decay have been proposed for the Dwyka Group on the basis of interstratified glaciogenic diamictites overlain by non-glaciogenic, ice rafted debris free mudstones. Each of these phases is assigned to deglaciation sequences (sensu Visser, 1997) and has been proposed to be incomplete, third order sequences made up of a basal lowstand systems tract (LST) followed by a transgressive systems tract (TST) or exclusively by a thick TST. The correlation of these deglaciation sequences has been extended to the adjacent Aranos-Kalahari basin and to the Paraná Basin (Itararé Group) in South America. Recent high-precision UPb ages on single crystal chemical abrasion, isotope dilution-thermal ionization mass spectrometry (CA-IDTIMS) have helped to refine the diachronous demise of the LPIA and the age of the Eurydesma transgression. Tentative correlations with the glaciogenic section (Sauce Grande Formation) in the Ventana Fold belt (VFB) and Malvinas/Falkland Islands (Fitzroy Tillite Formation) are supported by radiometric ages, and similar facies associations respectively. This interbasinal correlation of deglaciation sequences and radiometric ages allowed to constrain the occurrence of this fauna in southwestern Gondwana to the Asselian.The postglacial nature of the Eurydesma Fauna transgression in South American basins, particularly in the VFB-Claromecó Basin of Argentina, is in contrast with its interglacial character in the Southern African basins, where the Eurydesma transgression caps the deglaciation sequence 3 and underlies the deglaciation sequence 4.

Exploring the restricted Lontras Shale fossil record: Data biases or preservational casualties?

Throughout the Phanerozoic, numerous well-preserved fossiliferous sites have provided valuable insights into the evolution of ecosystems and organisms. Among these sites, the Lontras Shale Lagerstätte (LSL) within the Lontras Member in southern Brazil stands out as a rare glimpse into Carboniferous ecosystems of western Gondwana. The LSL is renowned for its diverse array of well-preserved fossils like insects, wood, fishes, larval cases, and poriferans, with different types of preservational pathways. Moreover, the Lontras Member is considered a maximum flooding surface that marks an interglacial warming peak of the final Late Paleozoic Ice Age, highlighting its paleoclimatological and paleogeographical relevance. However, the occurrence of fossils within the extensive Lontras Member is restricted to a few sites, raising questions about the factors influencing this constrained lateral and vertical distribution. Through meticulous literature review, this study aims not only to solidify the understanding of the Lontras Member's lithostratigraphy and paleontology but also to explore its broader implications and paleoenvironmental significance. We propose a comprehensive stratigraphic section for the Lontras Member, integrating local and regional sections from Santa Catarina and Paraná States, surveying paleontological sites and fossils exhaustively. By examining two additional fossil-rich sites in addition to the Lagerstätte outcrop, and analyzing vertical and horizontal distributions of the Member, we thoroughly explore the methodological, paleoenvironmental, and taphonomic factors that restricts this fossil record. This analysis extends beyond comparisons with paleontological insights from other units, locations, and Lagerstätten, encompassing modern analogous environments. The methodological biases are tied to stratigraphic focus, fieldwork scale, fossil size, and weathering degree of outcrops, constraining new fossil discoveries. Paleobiological and paleoclimatological factors, like transitional climatic conditions, limited organism diversity, inhospitable deep environments distant from the coast, and anoxic bottoms impact organism distribution and fossil recovery. The fossil transportability and the compositional resilience under widespread anoxia contributed as preservational constraints. While the LSL offers unique conditions for the proliferation and preservation of organisms, limiting the taphonomic window, facies of more energetic depositional conditions in other Lontras Member sites is more likely to harbor fossils, particularly transportable fragments and disarticulated pieces of chitinophosphatic or phosphatic composition. Addressing these biases unveils insights into flourishing ecosystems and organisms during this specific time period.

Reinterpreting glacial deposits as a MTD ponding sediment gravity flows in the upper Mojón de Hierro Formation (Tepuel–Genoa Basin, Argentina)

The Late Paleozoic Ice Age (LPIA) was the longest and most extensive glacial interval during the Phanerozoic, lasting from the Late Devonian to the late Permian (362–254 Ma). Numerous questions remain on the spatial and temporal extent of the ice centers, the timing of expansion and contraction of the ice sheets, and the distribution of ice across Gondwana through time. The Tepuel–Genoa Basin, in Patagonia (Argentina) was situated within the paleo South Polar Circle and contains a nearly continuous lower Carboniferous (Tournasian) to lower Permian (Artinskian) succession. The Mojón de Hierro Formation has been described as both non-glacial and glacial in origin, but lacks detailed sedimentological descriptions. This research investigates a ∼50 m succession with sedimentological and geochemical analysis within strata in the upper portion of the Mojón de Hierro Formation at Arroyo Garrido (Chubut Province). Five stratigraphic sections were measured and the strata were categorized into five lithofacies: 1) deformed sandstones, 2) thin-bedded diamictites, 3) graded rhythmites, 4) laminated mudstones with dispersed clasts, and 5) laminated mudstones. Deposition occurred in a slope environment from debris flows, turbidity currents, mass-movements, hemipelagic sedimentation, and ice rafting. The Chemical Index of Alteration (CIA) indicates values similar to average marine shales, which suggests that the muds were supplied from temperate terrestrial sediment sources. This indicates that icebergs from a distant source transited the basin and grounded glaciers were not present in the catchment area. Vanadium/chromium ratios (V/Cr) indicate dysoxic (restricted water circulation) values in samples between the mass-transported blocks and oxic values (well circulated water) in samples stratigraphically above the filled/leveled ponded mini basin. These oxygenation conditions suggest that the mass-transport deposit formed a topography on the sea floor, resulting in a mini basin that ponded sediments within the blocks. A local glacial source was not substantiated for the upper Mojón de Hierro Formation at Arroyo Garrido neither through the detailed facies analysis nor through geochemical proxies.

Orbitally-paced coastal sedimentary records and global sea-level changes in the early Permian

Orbital forcing affects climate system by regulating the amount of solar radiation received at the Earth's surface, which is vital for global hydrological cycles. However, a systematic understanding of the global water cycle with synergistic changes in ice sheets and sea levels under orbital forcing during the late Paleozoic ice age (LPIA) remains elusive. Here, we perform cyclostratigraphic analysis and sedimentary noise modeling for coastal sedimentary records (Well Greer #2 in the Permian Basin) from the early Permian and two sets of high-resolution paleoclimate simulation experiments using the Community Earth System Model. We provide the first high-resolution absolute astronomical time scale for the Permian Basin, which suggests that the timing of the early Permian Lower Leonard and Upper Wolfcamp Formations range from 286.29 ± 0.55 Ma to 289.05 ± 0.55 Ma, and the Lower Wolfcamp Formation ranges from 292.97 ± 0.16 Ma to 298.9 ± 0.15 Ma, respectively. In addition, we find a coupled phase relationship between high sea levels and eccentricity maxima, suggesting that eccentricity may have played a critical role in the early Permian sea-level oscillations. Paleoclimate simulations show that eccentricity and obliquity maxima lead to an overall increase in global mean temperature. Significant changes in surface temperature at middle to high latitudes are manifested as the polar amplification effect during the LPIA. Compared with obliquity, eccentricity leads to higher annual and summer variability in global surface temperature, and enhanced polar amplification results in ice retreat and sea-level rise. Evidence from Earth system modeling elucidates the phase relationship between orbital cycles and sea levels. Therefore, eccentricity, as the leading driving force in low latitudes, may dominate climate changes in the Earth's climate system and regulates global hydrological cycles during the LPIA.

Kungurian (Cisuralian) conifers and environmental changes: a negative δ13C shift in the flora of Tregiovo (Northern Italy)

The Le Fraine fossil locality, near the Tregiovo village (Trento Province, northern Italy) yields two of the best documented Kungurian (early Permian) plant fossil assemblages of eastern palaeoequatorial Pangea. Both plant assemblages (Tregiovo A and B) are dominated by walchian and voltzian conifers but differ in the relative abundance of the major plant groups. Analyses of the δ13C of the bulk organic carbon throughout the entire stratigraphic succession of Tregiovo show a negative trend towards the upper part of the succession. Several conifer taxa are recognized and taxon-specific δ13C analyses of the conifer remains in both plant fossil assemblages shows the same trend in all taxa. This correlation between the negative shift of the bulk organic carbon and the taxon-specific δ13C analysis shows that the negative δ13C shift recorded along the stratigraphic section is not the result of change in relative abundance within the plant assemblages but instead has an external cause, likely the δ13C values of atmospheric CO2. These results agree well with a negative shift observed in other Kungurian continental successions (e.g., China, South Africa, Australia), supporting a global perturbation in the carbon cycle. The negative shift in δ13C could very well record the last deglaciation phases of the Late Paleozoic Ice Age and the rise of the atmospheric pCO2.

Carbon Isotope Stratigraphy across the Devonian–Carboniferous Boundary in the East Paleo-Tethys Realm, Tibet, China

The Devonian–Carboniferous boundary is one of the most important turning points in geological history, marked by the Late Paleozoic Ice Age and Late Devonian extinction. This study investigates the carbon isotope stratigraphy across the Devonian–Carboniferous boundary in Lhasa block, Tibet, China, which was part of the Gondwana continent during that time. The carbon isotope curves show a significant negative excursion trend, consistent with those of the South China block and other regions on the Laurentia continent. This global negative shift may be attributed to the burial of significant amounts of 12C-rich organic matter in strata, a consequence of the Late Devonian extinction event. Based on the carbon isotope curve and stratigraphic data of the Lhasa block, this study determined, for the first time, the specific horizon of the Devonian–Carboniferous boundary in Tibet, which is located between grayish white bioclastic limestone and yellowish-brown sandy limestone in the upper part of the Chaguoluoma Formation (D1C1ĉ). These findings provide a new reference for the international stratigraphic community to reconsider the position of GSSP on the Devonian–Carboniferous boundary, as well as study the Late Devonian mass extinction and Late Paleozoic glaciation.

Carboniferous-Permian high-resolution conodont biostratigraphy and paleoclimate change in North China

The Carboniferous-Permian transition is a critical period for the Late Paleozoic Ice Age that evolved from an acme to the subsequent demise with the initiation of long-term drying in low latitudes. During this time interval, extensive epicontinental deposition occurred in North China in the eastern tropical Tethyan region, and archived important information of climate and sea-level changes. Though several high-precision zircon UPb ages have been reported, they have some conflicts with previously defined biostratigraphic correlations, especially for the Taiyuan Formation. Lack of high-resolution conodont biostratigraphy has impeded the correlation with other well-studied Pangean records. In this study, five conodont zones were established for the successions of the Taiyuan Formation in southern North China. They are Streptognathodus wabaunsensis, S. isolatus, S. sigmoidalis, S. constrictus and S. fusus biozones in ascending order, constraining a late Gzhelian to late Asselian age for the Taiyuan Formation in southern North China, which is consistent with published high-precision zircon UPb ages. The Unitary Association (UA) analysis was used to reconcile the conodont biostratigraphy of the Taiyuan Formation in North China, and was combined with previously published high-precision UPb ages to construct a new chronostratigraphic framework for the Carboniferous-Permian strata across North China. It explicitly indicates an earlier initiation of climate aridification in the northern part than in the southern part of North China possibly due to northward drift and/or increased atmospheric pCO2 and associated global warming.

Wildfire activity and impacts on palaeoenvironments during the late Paleozoic Ice Age - New data from the North China Basin

The Late Paleozoic is widely recognized as a ‘high-fire’ world. However, the impact of wildfires on the vegetational change as well as the relationship between fire and low atmospheric pCO2 and high pO2 in the Late Paleozoic remains a matter of debate. New data on fossil charcoal and pyrogenic PAHs in coal deposits from the Yuzhou Coalfield, the southern part of the North China Basin, are integrated into previous studies to increase our current understanding of the role of wildfires on land and in marine environments during the late Carboniferous and early Permian. Analyses of bulk petrographic and organic geochemical data indicate that during deposition of the Taiyuan Formation (late Gzhelian and early Asselian Stage) wildfires were more prevalent and were characterized by a large proportion of crown fire. A previous plant macrofossil assemblage study of the Taiyuan and Shanxi formations, together with fire traits of ancient plant lineages, indicates that wildfire may likely be one of the major drivers of the thriving of the Cathaysian Flora during this period. Wildfire and post-wildfire processes might have acted as important controlling factors for organic carbon burial. Persistent organic carbon sequestration (as coals or charcoal) on land and increasing organic carbon burial in the ocean are coincident with the peak in pO2 during the apex of the Late Paleozoic Ice Age.

Lithofacies and sequence stratigraphic analysis of the glaciomarine lower Wynyard Formation (Pennsylvanian–early Permian, Tasmanian Basin)

Glaciation during the Late Paleozoic Ice Age climatic interval (~370–260 Ma) was likely dynamic; consisting of numerous ice centers that grew and shrank asynchronously through time. Improvements in understanding of the spatial and temporal depositional complexity of glaciomarine sedimentary systems have shown that in order to characterize the conditions of Late Paleozoic glaciation, glaciogenic depositional systems and their stratigraphy must fundamentally be understood at the local level. To that end, this study reexamines the physical sedimentology and sequence stratigraphy of the type-section of the Permo-Carboniferous, glaciomarine Wynyard Formation (Wynyard Tillite) of the Tasmanian Basin by describing a 415 m thick interval of the formation, beginning at its basal erosional unconformity with the Proterozoic Burnie (Oonah) Formation.The glaciogenic nature of the Wynyard Formation stratigraphy is indicated by the characteristics of clasts throughout the succession (striated, faceted, angular, and variable lithologies and grain sizes). Three glacial depositional environments were interpreted: a grounding zone wedge deposited in an ice-contact setting, glacier-proximal portion of a grounding line fan and/or morainal bank, and cyclopelites deposited in a glacier-intermediate to glacier-distal setting. Mass transport and turbidite deposits are common throughout all facies associations, as is soft sediment deformation likely caused by slumping. Several boulder pavements occur throughout the succession, indicating periodic glacier grounding. Together, these facies associations indicate that this Wynyard Fm succession is composed of glaciogenic sediments that were deposited in sub-aqueous, marine, predominantly proglacial environments. The sequence stratigraphic analysis indicates that this entire succession of the Wynyard Fm was likely deposited during the single retreat phase of the “Wynyard Glacier”, with one notable readvance over the area.The interpretations made by this work enhance the understanding of glaciation of the Tasmanian Basin during the LPIA through facies analyses and a sequence stratigraphic approach, which allowed for detailed subdivision of lithologies that enabled inferences regarding the type, timing, and extent of the “Wynyard glacier”. This Wynyard Fm succession was likely deposited during a single glacier retreat with some minor readvances that may have occurred on the order of decades to years. Additionally, the glacier's grounding line was likely never more than a few kilometers upglacier (south) of this location during deposition.These findings are significant, because the massive diamictites that comprise this succession had previously been considered homogenous and therefore resisted detailed interpretations. Constraining the often-complex depositional histories of glaciogenic strata in similar fashions across the Tasmanian Basin allows us to better understand how these glaciogenic deposits fit into the global climate system of the Late Paleozoic Ice Age.

Did sea level change drive carbon isotopic trends in the Madison Shelf? Sequence stratigraphy and carbon isotopes in the Mississippian Lodgepole Formation of southwest Montana

The Lower Mississippian Lodgepole Formation of Montana and Wyoming records one of the largest positive carbon isotopic excursions of the Phanerozoic. This globally recognized up to 7‰ increase in δ13Ccarb values occurs across the North American Kinderhookian-Osagean boundary (referred to as the KO excursion). It has been argued to reflect significant organic carbon burial, possibly linked to the onset of the Late Paleozoic Ice Age. Previously proposed correlations between carbon isotopic patterns and the sequence stratigraphic framework within these strata suggests that changes in sea level could have played a significant role in the expression and/or magnitude of the KO excursion in the Madison Shelf. This study explores the relationship between carbon isotopic values and sea level change at multiple scales. To accomplish this, we provide a comprehensive overview of the sedimentological and stratigraphic framework and address uncertainty about the number of sequences in the Lodgepole Formation. Our results support a three-sequence model for the Lodgepole Formation. Based on the number of sequences and the placement of sequence stratigraphic surfaces, we see little evidence of statistically significant correlation between carbon isotopic trends and the sequence stratigraphic framework. We argue that sea level change was not the primary driving mechanism for carbon isotopic trends in the Madison Shelf, nor the KO excursion. Instead, we support models that invoke global ocean anoxia and/or destabilization of the global carbon cycle due to land plants.

Paleo-environmental conditions and organic carbon accumulation during glacial events: New insights from saline lacustrine basins

Organic carbon accumulation was common during glacial events, but previous studies have focused primarily on marine facies and few have investigated lacustrine facies. This study investigates the sedimentation and organic matter accumulation during the Late Paleozoic Ice Age (LPIA; Late Carboniferous–Early Permian) in the Junggar Basin of China, which was located in a mid-latitude region of Northern Pangea at the time. Organic-rich hydrocarbon source rocks in three sags were examined. Our findings indicate that the Fengcheng Formation (ca. 300 Ma) in the Mahu Sag was deposited in a saline (carbonate content = 40.8 ± 18.4 wt%), sub-oxic–anoxic (total S/Fe [TS/Fe] = 0.5 ± 0.3), and highly alkaline (δ15N = 19.6‰ ± 2.6‰) lacustrine environment. The Lucaogou Formation (ca. 290 Ma) in the Jimusaer Sag was deposited in a freshwater–saline (carbonate content = 28.9 ± 15.6 wt%), oxic–anoxic (TS/Fe = 0.4 ± 0.8), and circum-neutral–highly alkaline (δ15N = 10.7‰ ± 3.2‰) lacustrine setting. The Lucaogou Formation in the Fukang Sag was deposited in a freshwater–saline water (carbonate content = 11.5 ± 4.3 wt%), oxic–sub-oxic (TS/Fe = 0.1 ± 0.1), and relatively neutral pH (δ15N = 7.0‰ ± 0.9‰) lacustrine environment. The source rocks in these three sags represent a completely evolutionary sequence of a saline lacustrine basin, as the saline degrees follow the order of the Lucaogou Formation in the Fukang Sag < the Lucaogou Formation in the Jimusaer Sag < the Fengcheng Formation in the Mahu Sag. The co-evolution of depositional environment, particularly pH, and source rock quality is shown as the abundance of organic matter and hydrocarbon-generating potential first increasing and then decreasing with increasing pH, as the type of organic matter first became increasingly oil prone and then remained unchanged. This reflects the interplay between the bio-precursors, paleo-environment, and organic C accumulation. This may be a common feature of saline lacustrine basins throughout geological time worldwide, such as the Eocene Piceance Basin in USA (the Green River Formation), the Cretaceous Campos Basin in Brazil (the Itapema and Barra Velha formations), and the Eocene saline lacustrine basins in China (e.g., the Shahejie, Qianjiang, and Xiaganchaigou formations). During glacial periods, it is common for lacustrine basins to undergo salinization, which ultimately leads to such basins being ideal for fossil energy exploration. The accumulation of organic carbon drove and responded to the glacial period by sequestrating atmospheric CO2, and was thus an important part of the global carbon cycle that requires further research.

Effects on global warming by microbial methanogenesis in alkaline lakes during the Late Paleozoic Ice Age (LPIA)

Methane (CH4) is an important greenhouse gas, but its behavior and influencing factors over geological time scales are not sufficiently clear. This study investigated the Late Paleozoic Ice Age (LPIA), which is thought to have experienced an interval of rapid warming at ca. 304 Ma, that may have been analogous to modern warming. To explore possible causes of this warming event, we investigated ancient alkaline lakes in the Junggar Basin, northwestern China. Results show that microbial CH4 cycling here was strong, as evidenced by carbonate δ13C (δ13Ccarb) values of &amp;gt;5‰, ∼+0.6‰ offsets between pristane δ13C (δ13CPr) and phytane δ13C (δ13CPh) values, a 3β-methylhopane index of 9.5% ± 3.0%, and highly negative δ13C values of hopanes (−44‰ to −61‰). Low sulfate concentrations in the alkaline lakes made methanogenic archaea more competitive than sulfate-reducing bacteria, and the elevated levels of dissolved inorganic carbon promoted methanogenesis. Biogenic CH4 emissions from alkaline lakes, in addition to CO2, may have contributed to rapid climate warming.