Climatic Cycles Research Articles

Gzhelian cyclothem development in the western North China cratonic basin and its glacioeustatic, tectonic, climatic and autogenic implications

The Gzhelian Ximing Sandstone–to–No. 8 Coal succession of the Taiyuan Formation in the Linxing gas field and adjacent areas records the complex nested architecture of the Palougou Cyclothem and component cyclothems 2–10 developed in the western North China underfilled cratonic basin. Integrated facies and sequence stratigraphic analysis of core, well log, outcrop, and seismic data reveals architectural variation of the Palougou Cyclothem in the study area from southwestward retrograding incised-valley estuary and lagoon (TST) through upward and northeastward prograding coastal plain to epeiric shelf (HST) into downward and eastward prograding open-coast tidal flat and epeiric shelf with aggrading distributive fluvial system (FSST). The component cyclothems vary in the internal architecture through the Palougou Cyclothem from mixed retrogradational–progradational (R–P; R/P > 1) cyclothems 2–4 in the early TST to retrogradation-dominated (R/P ≫1) cyclothems 5–7 in the late TST, progradation-dominated (R/P ≪1) Cyclothem 8 in the HST, and fluvial aggradation-dominated cyclothems 9 and 10 in the FSST. The Palougou Cyclothem and component cyclothems constrained by conodont-bearing limestone marker beds and radiometric dating have been observed to be substantially synchronized with the Gzhelian interglacial–glacial cyclothem and nested 400-kyr cyclothems in the North American Midcontinent and Donets Basin. The cyclic change in accommodation at the scale of the Palougou Cyclothem and component cyclothems has been ascribed to the third-order interglacial–glacial cycle and fourth-order, long eccentricity (ca. 400 kyr)-driven glacioeustatic fluctuations coupled with the tectonically driven source–to–sink reorganization. The progressively decreasing siliciclastic flux and increasing vegetation through both the Palougou Cyclothem and individual component cyclothems have been ascribed to the third- and fourth-order equatorial seasonally dry–wet climatic cycles coupled with the tectonically driven source–to–sink reorganization, in concert with the Gzhelian third- and fourth-order interglacial–glacial eustatic cycles. Both the transgressive fluvial degradation and the falling-stage fluvial aggradation have been ascribed to a higher-gradient fluvial profile relative to the gradient of the receiving North China epeiric shelf. The autogenic shoreline retreat, advance and channel migration modified the depositional response to the third- and fourth-order sea level rise through time. The termination of the falling-stage fluvial channel belts in the lateral and distal floodplain mires has been ascribed to the sustained fluvial aggradation and autodetachment of the fluvial fan from the syn-depositional shoreline in response to steady fall of relative sea level. This study contributes to a proper understanding of the Gzhelian North China intracratonic cyclothem development in response to the coupled glacioeustatic, tectonic, climatic, and autogenic processes at the third- and fourth-order scales, but also provides a context within which to interpret the symbiotic relationship, and predict the distribution, of superimposed coal–sandstone–shale gas reservoirs, and to investigate the impact of depositional heterogeneities on hydrocarbon generation and migration pathways.

The Role of Past Climatic Variability in Fluvial Terrace Formation, a Case Study from River Mureş (Maros), Romania

Fluvial terrace formation is a complex process governed by the interplay of climatic and tectonic forcings. From a climatic perspective, an incision is usually related to climatic transitions, while valley aggradation is attributed to glacial periods. We have reconstructed the formation of Late Pleistocene fluvial terraces along the middle, mountainous section of a temperate zone river (Mureş/Maros) in order to identify the roles of different climatic periods and potential vertical displacement in terrace development. Investigations were based on two profiles representing two different terrace levels. The profiles were subjected to sedimentological and detailed geochronological analyses using optically stimulated luminescence (OSL). The results indicated that the investigated terraces represent different incision events coinciding with climatic transition periods. However, a joint MIS 3 valley aggradation period can be identified at both of them. Thus, the relatively mild but highly variable climate of the MIS 3 facilitated sediment mobilization from upland catchments. On the other hand, there is no evidence of aggradation under the cold and stable climate of MIS 2. However, the tectonic setting favours incision at the site. Based on our results, we concluded that the timing of the main events was controlled primarily by climatic forcing. The terrace formation model recognised might also be applied at other rivers in the region.

550‐Year Climate Periodicity in the Yunnan‐Guizhou Plateau During the Late Mid‐Holocene: Insights and Implications

AbstractSignificant multi‐centennial climate oscillations have been documented in a number of well‐dated climate records across the Holocene epoch and left various imprints in human cultural history. In this study, we developed speleothem δ13C, δ18O, trace elements, and lamina thickness records from the Yunnan‐Guizhou Plateau (YGP). Our high‐resolution and precisely dated records show a significant ∼550‐yr cycle as the dominant pattern of regional temperature and vegetation variations between ∼5,870 and ∼3,670 years ago. The phase analyses of the 550‐yr cycles among our speleothem records, other Northern Hemisphere climate records, solar activity index, and Atlantic meridional overturning circulation (AMOC) variations suggest that this climate cycle has a large spatial extent, and may be causally linked to the AMOC changes through coupled oceanic‐atmospheric processes. Additionally, the first cold phase of the ∼550‐yr cycle in our records coincides with the major cultural development on the YGP at ∼5,500–5,000 years ago, suggesting a critical relationship between climate and prehistorical cultural changes in the region.

Astronomically forced saline lake deposition and paleoclimatic response in the Huanggang Basin during the Paleogene, Eastern China

Halite is a type of evaporite that can be processed into refined salt for food processing, and used as an important raw material in the chemical industry. However, our understanding of the astronomical forcing pattern on halite formation at the sedimentary basin scale is still limited. Here, we present a halite-rich lacustrine record from the middle-late Eocene through the early Oligocene of the Dawenkou Formation in the Huanggang Basin, Eastern China. A ∼ 6.5-Myr-long floating astronomical time scale was constructed based on a 405-kyr orbital eccentricity cycle tuning of gamma-ray (GR) series measured from the Upper and Middle members of the Dawenkou Formation. Our results indicate that halite intervals in the Middle Member of the Dawenkou Formation correspond well with the minima of the 100 kyr orbital eccentricity, suggesting the short eccentricity-induced climatic cycles forcing of halite formation by impact on seasonal contrasts. Our work provides essential context for understanding the pattern of halite deposits from the aspect of climate cycles at the sedimentary basin scale.

Renovation wave of the residential building stock targets for the carbon-neutral: Evaluation by Finland and Türkiye case studies for energy demand

The recent EU energy efficiency goals and renovation wave have called attention to the building stock's energy-demand-saving potential. Finland and Türkiye, with two contrasting perspectives on climate zones and building typologies in the EU, were chosen to analyse energy-demand potential. The study's scope was restricted to the residential building stock, a significant portion of the overall building stock. The latest residential building stock data and regulations history was gathered via a bottom-up approach. Then three representative buildings for each typology were energy demand simulated for climatic regions and periods. Thirdly, the area-weighted energy needs difference values for each decade (1960–2020) and climatic zone were multiplied with the building stock data to predict saving potential. Fourth, the impact of factors on energy demand was assessed using full-factorial analysis. Lastly, the main factors were parametrically simulated and compared with mandatory limits. The substantial energy-demand-saving potential existed in both countries. The findings highlighted the following: (1) the energy demand saving potential for the Finnish and Turkish building stocks were calculated as 10,176.9 GWh/year (30 %) and 124,889.3 GWh/year (50 %), respectively; (2) energy demand in Finland is dependent strongly on the climatic zone; (3) the optimum thermal insulation thickness for Finnish buildings is likely to be at the current level or even below it, while Türkiye's insulation limits are climatic zone based but not sufficient for carbon neutral; (4) Surprisingly for both countries, the most important factors to consider when renovating buildings were the thermal insulation level of the walls and roof in single-family buildings and the thermal insulation level of the walls in multi-family buildings and the airtightness of the building envelope. It should be noted that for Finland, building energy efficiency regulations will differ on the climate zone. Türkiye's newly published NZEB values should become mandatory lower limits for all residences because current legislative limits are insufficient and date back to the 2000s.

Theory of continental drift – causes of the motion. Historical review and observations

The theory of continental drift was published as early as 1912, but the mechanism and energy source of this motion has not yet been elucidated. In many cases, the generally accepted model of convection currents in the mantle contradicts observations such as the spreading of the ocean floor, the extension of rifts from triple points to all sides, the more or less unilateral movement of the lithosphere relative to the mantle, and others. In the first part of the double article, the evolution of views on this issue is shown, as well as measured data that document the important role of extraterrestrial energy sources for the movement of lithospheric plates in daily, annual and long-term climate cycles. In the second part of the two-part article, the entire theory of the mechanism of lithospheric plate motion will be outlined, based on the accumulation of incoming energy from the Sun in crustal rocks, the ratcheting mechanism, and the thermoelastic wave penetrating from the Earth's surface through the entire crust.

Safe and just Earth system boundaries

The stability and resilience of the Earth system and human well-being are inseparably linked1–3, yet their interdependencies are generally under-recognized; consequently, they are often treated independently4,5. Here, we use modelling and literature assessment to quantify safe and just Earth system boundaries (ESBs) for climate, the biosphere, water and nutrient cycles, and aerosols at global and subglobal scales. We propose ESBs for maintaining the resilience and stability of the Earth system (safe ESBs) and minimizing exposure to significant harm to humans from Earth system change (a necessary but not sufficient condition for justice)4. The stricter of the safe or just boundaries sets the integrated safe and just ESB. Our findings show that justice considerations constrain the integrated ESBs more than safety considerations for climate and atmospheric aerosol loading. Seven of eight globally quantified safe and just ESBs and at least two regional safe and just ESBs in over half of global land area are already exceeded. We propose that our assessment provides a quantitative foundation for safeguarding the global commons for all people now and into the future.

Influence of a Rapidly Uplifting Orogen on the Preservation of Climate Oscillations

AbstractClimate oscillations preserved in sedimentary archives tend to decrease in resolution further back in Earth's history. High‐frequency climate cycles (e.g., ∼20‐Kyr precession cycles) are especially prone to poor preservation due to sediment reworking. Recent studies have shown, however, that given sufficient basin accommodation space and sedimentation rate, shallow‐marine paleoclimate archives record precession‐driven hydroclimate change in mid‐low latitude regions. Our study evaluates how the evolution of a rapidly uplifting orogen influences the recording of astronomical climate forcing in shallow‐marine sedimentary strata in the Taiwan Western Foreland Basin (WFB). Time‐series analysis of gamma‐ray records through the late Miocene–Pliocene Kueichulin Formation shows that during early stages of Taiwan orogenesis (before 5.4 Ma), preservation of precession‐driven East Asian Summer Monsoon variability is low despite increasing monsoon intensities between 8 and 3 Ma. The Taiwan Strait had not formed, and the southeast margin of Eurasia was open to the Pacific Ocean. Consequently, depositional environments in the WFB were susceptible to reworking by large waves, resulting in the obscuration of higher‐frequency precession cycles. From 5.4 to 4.92 Ma, during early stages of emergence of Taiwan, basin subsidence increased while sedimentation rates remained low, resulting in poor preservation of orbital oscillations. After 4.92 Ma and up to 3.15 Ma, Taiwan became a major sediment source to the WFB, and sheltered the WFB from erosive waves with the development of Taiwan Strait. The elevated sediment influx, increased basin accommodation as the WFB developed, and formation of a semi‐sheltered strait, resulted in enhanced preservation of precession‐driven East Asian Summer Monsoon variability.

Diel variation of the epibenthic community associated with seagrasses in a subtropical biosphere reserve

We evaluated the diel variability of abundance and species diversity of the epibenthic community associated with seagrasses in Los Petenes Biosphere Reserve (LPBR) in the southwestern Gulf of Mexico. For this purpose, four collection campaigns were conducted (rainy season: October 2011 and June 2016, dry season: March 2012 and 2016) in a diel cycle with a periodicity of 3 h. Our results showed significant differences in diversity, richness, and abundance as a function of the diel cycle (p < 0.05), and in the community structure as a function of the diel cycle and the climatic sampling periods. Two different benthic assemblages, one for the day and the other for the night period were identified. Each assemblage varies on its species composition according to the climatic periods but maintains the general day-night pattern at all the sampled years. The abundance of diurnal species was significantly (p < 0.01) associated with the temperature, salinity, oxygen, and depth values. Our results suggest that the epibenthic community associated with seagrass habitats shows significant diurnal and nocturnal changes in community composition and abundance due to changes in light intensity that favors the appearance of characteristic species in each period. Understanding such community changes will allow us to establish the baseline parameters for assessing the environmental health of the benthic habitats of the LPBR with greater accuracy.

Synopsis of Upper Tukau Deposits along the Sungai Rait Road, Miri District, Sarawak, Malaysia

The Upper Tukau Formation is exposed along the Sungai Rait Road and can be described as follows: the lowermost member is formed by soft clay and silt, the “Brick Shale”, and contains meandering sandy channels. The clay is thoroughly excavated in the area and used as raw material for bricks. The second and hilltop-forming layer is built by relatively hard amalgamated, and partly channelized sandstone layers, often lined with diagenetically precipitated iron minerals (i.e., pyrite and siderite concretions). The youngest member is characterized by intertidal channels and mud flats. Geochemical studies point to a polymictic source of already recycled sediments, deposited in predominantly oxic, partly suboxic environments, with rapid transitions observed from one milieu to the other. In broad terms, the entire sequence appears to be a shallowing-upwards cycle, leading from subtidal to intertidal realms. The surprising sharp boundaries between clay and sand packages are discussed and may be related to climate cycles.

Late Pleistocene Altitudinal Segregation and Demography Define Future Climate Change Distribution of the Peromyscus mexicanus Species Group: Conservation Implications.

Mountains harbor a significant number of the World's biodiversity, both on tropical and temperate regions. Notably, one crucial gap in conservation is the consideration of historical and contemporary patterns influencing differential distribution in small mammal mountain species and how climate change will affect their distribution and survival. The mice Peromyscus mexicanus species group is distributed across mountains in Guatemala-Chiapas and Central America, which experienced significant effects of glacial and interglacial cycles. We determined phylogeographic and demographic patterns of lowlands and highlands mountain lineages, revealing that the radiation of modern P. mexicanus lineages occurred during the Pleistocene (ca. 2.6 mya) along Nuclear Central America. In concert with climatic cycles and the distribution of habitats, lowland and highland lineages showed recent population size increase and decrease, respectively. We also estimated the current and future distribution ranges for six lineages, finding marked area size increase for two lineages for which vegetation type and distribution would facilitate migrating towards higher elevations. Contrastingly, three lineages showed range size decrease; their ecological requirements make them highly susceptible to future habitat loss. Our findings are clear evidence of the negative impacts of future climate change, while our ability to manage and conserve these vulnerable ecosystems and mountain species is contingent on our understanding of the implications of climate change on the distribution, ecology, and genetics of wildlife populations.

Paleohydrologic history of pluvial lake San Agustin, New Mexico: Tracking changing effective moisture in southwest North America through the last glacial transition

Paleoclimate records across the Intermountain West region of North America show significant regional variation in timing and magnitude of wet conditions that accompanied the last glacial-interglacial transition. To understand the climate controls on paleohydrologic change, well-dated records are needed across the region. The Plains of San Agustin (New Mexico, USA) is a closed-basin watershed of the American Southwest influenced by both winter westerly and summer North American Monsoon precipitation. The flat valley floors of the Plains contain lake and groundwater discharge deposits that record multiple periods of past wet climate. We present a record of hydroclimate for the past 26,000 years based on radiocarbon, U–Th series, and OSL dating of these deposits and stratigraphic correlation across the three sub-basins of the lake system. We find that two major lake oscillations occurred, coincident with the global Last Glacial Maximum (∼23–18 ka) and with Heinrich Stadial 1 (∼17–14 ka). The LGM lake cycle created a deep lake in the lowermost sub-basin, fed by marsh/lake overflow in the upper sub-basins. The Heinrich Stadial 1 wet interval attained the highest recorded lake level between ∼17.0 and 15.3 ka, merging the lower two sub-basins into one lake. Both lake cycles agree well in timing and magnitude with other lake-based records from the southwestern U.S., supporting previous interpretations that a south-shifted cool season storm track brought a dipole-like pattern of enhanced moisture to the southwest at the expense of drier conditions in the northwest during the LGM and deglaciation. A transition from lake to groundwater discharge conditions followed during the Bølling-Allerød (14.7–12.9 ka) across the study area. Wet meadows prevailed in the lower sub-basin during the Younger Dryas (12.9–11.7 ka), with marsh and open lake conditions in the upper and middle sub-basins, respectively. During the early Holocene, discrete wet intervals are recorded by ages for wet meadow deposits in all sub-basins with centennial-millennial frequency at 9.9, 8.8, 8.2 ka. These events agree well with other Intermountain West records showing wetter-than-present conditions prior to 8 ka. Two additional wet periods, centered at 6.8 and 5.4 ka, occurred during the driest known interval of the middle Holocene, and likely were partly supported in the Plains of San Agustin by summer moisture associated with the peak strength of the North American Monsoon. Our record highlights that both winter and summer moisture support water resources in New Mexico watersheds.

A comparison of the climate and carbon cycle effects of carbon removal by afforestation and an equivalent reduction in fossil fuel emissions

Abstract. Afforestation and reduction of fossil fuel emissions are two major components of climate mitigation policies. However, their effects on the Earth's climate are different because a reduction of fossil fuel emissions directly alters the biogeochemical cycle of the climate system and modifies the physics of the atmosphere via its impact on radiation and the energy budget, while afforestation causes biophysical changes in addition to changes in the biogeochemical cycle. In this paper, we compare the climate and carbon cycle consequences of carbon removal by afforestation and an equivalent fossil fuel emission reduction using simulations from an intermediate complexity Earth system model. We performed two major sets of idealized simulations in which fossil fuel emissions follow extended Shared Socioeconomic Pathway (SSP) scenarios (SSP2-4.5, 3-7.0, and 5-8.5), and equal amounts of carbon are removed by afforestation in one set and by a reduction in fossil fuel emissions in another set. Our simulations show that the climate is cooler by 0.36, 0.47, and 0.42 ∘C in the long term (2471–2500) in the case of reduced fossil fuel emissions compared to the case with afforestation when the emissions follow the SSP2-4.5, SSP3-7.0, and SSP5-8.5 scenarios, respectively. The global mean surface temperature is cooler in the reduced fossil fuel emissions case compared to the afforestation case because the net biophysical effect of warming from afforestation partly offsets the biogeochemical cooling effect of afforestation. Thus, in terms of climate benefits, reducing fossil fuel emissions could be relatively more beneficial than afforestation for the same amount of carbon removed from the atmosphere. However, a robust understanding of the processes that govern the biophysical effects of afforestation should be improved before considering our results for climate policy.

A seasonal analysis of aerosol NO3− sources and NOx oxidation pathways in the Southern Ocean marine boundary layer

Abstract. Nitrogen oxides, collectively referred to as NOx (NO + NO2), are an important component of atmospheric chemistry involved in the production and destruction of various oxidants that contribute to the oxidative capacity of the troposphere. The primary sink for NOx is atmospheric nitrate, which has an influence on climate and the biogeochemical cycling of reactive nitrogen. NOx sources and NOx-to-NO3- formation pathways remain poorly constrained in the remote marine boundary layer of the Southern Ocean, particularly outside of the more frequently sampled summer months. This study presents seasonally resolved measurements of the isotopic composition (δ15N, δ18O, and Δ17O) of atmospheric nitrate in coarse-mode (&gt; 1 µm) aerosols, collected between South Africa and the sea ice edge in summer, winter, and spring. Similar latitudinal trends in δ15N–NO3- were observed in summer and spring, suggesting similar NOx sources. Based on δ15N–NO3-, the main NOx sources were likely a combination of lightning, biomass burning, and/or soil emissions at the low latitudes, as well as oceanic alkyl nitrates and snowpack emissions from continental Antarctica or the sea ice at the mid-latitudes and high latitudes, respectively. Snowpack emissions associated with photolysis were derived from both the Antarctic snowpack and snow on sea ice. A combination of natural NOx sources, likely transported from the lower-latitude Atlantic, contribute to the background-level NO3- observed in winter, with the potential for a stratospheric NO3- source evidenced by one sample of Antarctic origin. Greater values of δ18O–NO3- in spring and winter compared to summer suggest an increased influence of oxidation pathways that incorporate oxygen atoms from O3 into the end product NO3- (i.e. N2O5, DMS, and halogen oxides (XO)). Significant linear relationships between δ18O and Δ17O suggest isotopic mixing between H2O(v) and O3 in winter and isotopic mixing between H2O(v) and O3/XO in spring. The onset of sunlight in spring, coupled with large sea ice extent, can activate chlorine chemistry with the potential to increase peroxy radical concentrations, contributing to oxidant chemistry in the marine boundary layer. As a result, isotopic mixing with an additional third end-member (atmospheric O2) occurs in spring.

Urban effects on local cloud patterns

Urbanization extensively modifies surface roughness and properties, impacting regional climate and hydrological cycles. Urban effects on temperature and precipitation have drawn considerable attention. These associated physical processes are also closely linked to clouds' formation and dynamics. Cloud is one of the critical components in regulating urban hydrometeorological cycles but remains less understood in urban-atmospheric systems. We analyzed satellite-derived cloud patterns spanning two decades over 447 US cities and quantified the urban-influenced cloud patterns diurnally and seasonally. The systematic assessment suggests that most cities experience enhanced daytime cloud cover in both summer and winter; nocturnal cloud enhancement prevails in summer by 5.8%, while there is modest cloud suppression in winter nights. Statistically linking the cloud patterns with city properties, geographic locations, and climate backgrounds, we found that larger city size and stronger surface heating are primarily responsible for summer local cloud enhancement diurnally. Moisture and energy background control the urban cloud cover anomalies seasonally. Under strong mesoscale circulations induced by terrains and land-water contrasts, urban clouds exhibit considerable nighttime enhancement during warm seasons, which is relevant to strong urban surface heating interacting with these circulations, but other local and climate impacts remain complicated and inconclusive. Our research unveils extensive urban influences on local cloud patterns, but the effects are diverse depending on time, location, and city properties. The comprehensive observational study on urban-cloud interactions calls for more in-depth research on urban cloud life cycles and their radiative and hydrologic implications under the urban warming context.

Features of the processes of convection and water intrusion at the boundary of the hydrogen sulfide contamination layer in the Black Sea in the climatic period 1991—2020

The comparison of modern hydrophysical conditions in the Black Sea with the previously analyzed period of 1903—1982 was carried out based on the materials of the recently created (1991—2020) climate array of average monthly thermohaline characteristics of waters. The dynamic of processes in the upper 150-meter layer (halocline) of the Black Sea was evaluated based on the analysis of climatic materials on the vertical distribution of the depth of the maximum water salinity gradient, which is interpreted as the upper boundary of the hydrogen sulfide layer in the Black Sea. The comparison of state and seasonal fluctuations of this characteristic during the analysis of average monthly maps was carried out by their averaging. According to modern data(1991—2020), in the open part of the sea, a more intense intrusion of these waters up to a horizon of 40 m was found, as well as single cases of natural release of hydrogen sulfide from the depth to the surface. There is a clearly pronounced semi-annual cyclicity in temporal variability; however, in the modern period, the shift was for the whole season: in 1903—1982, the convection (the downwelling of these waters) occurred during autumn-winter, and intrusion (upwelling) — during spring-summer; in 1991—2020 according to the same climatic data, convection occurs during winter-spring, and intrusion occurs during summer-autumn, with the maximum depth of occurrence during the period of winter-spring convection and the minimum during the period of summer-autumn water intrusion. The axes of the northern and southern convergence zones laying near the corresponding coasts of the sea, and the axis of the zone of central divergence is close to open areas in its middle part. By these axes, the differences in the depth of occurrence between the period of convection and intrusion in the northern and southern convergence zones were 21.5 and 17.5 m, respectively; for the central divergence zone, it was 7.5 m.

The Keivy Domain of the Kola Granulite–Gneiss Area on the Baltic Shield: Most Ancient Median Massif of the Continental Crust

Studies of lithotectonic formations within the Keivy domain of the NE Baltic Shield have shown that the domain was tectonically overlapped by adjacent microcontinents during regional collision processes in the Late Archean. As a consequence, the continental crust of the Keivy domain was submerged, relative to other blocks of the continental crust, and the described domain acquired the features of a classical median massif. Surrounded on all sides by collision systems, the Keivy median massif entered the cratonization regime. This led to intensive processes of denudation of the surrounding domains of the crust and the accumulation of a thick sedimentary cover on the surface. The described processes occurred during the formation of the first supercontinent (Monogea) in the history of the Earth and the manifestation of the Early Precambrian Huronian glaciation, which left its traces on most domains of the Earth’s continental crust. Thus, the processes of peneplain formation within the Keivy massif occurred under the cold weather conditions, high volcanic activity in the peripheral zones, and sedimentary cover saturation with the products of the physical and chemical mineral transformation of tonalite–trondhjemite and greenstone rock assemblages. The unique combination of certain geodynamic and climatic cycles on the Baltic Shield in the Late Archean led to the accumulation of extensive stratiform deposits of alumina raw materials within the Keivy median massif.

OSL dating of coastal dunes on the southeastern coast of Hainan Island, China

Coastal dune sediments and landforms offer a unique opportunity to understand climate change and sea level change on the centennial-millennial time scale. However, there is a paucity of chronological studies on the effects of storms on the evolution of coastal dunes along the temperate coastline of China. In this study, optically stimulated luminescence (OSL) dating of sand dunes was conducted to investigate the process and mechanism of coastal dune evolution on the southeastern coast of Hainan Island, China. The results show that the coastal dune evolution experienced three rapid accumulation periods: 28-21 ka, 14-4 ka, and 3.0 ka-present. The three rapid accumulation periods correspond to the last glacial maximum, the late Pleistocene/early-mid Holocene, and the late Holocene climatic dry-cold period, respectively. Sea level change and the East Asian winter monsoon, in conjunction with the enhanced storminess, play a key role in driving the sand dune evolution on the south-eastern coast of Hainan Island. These findings are of great significance for regional planning and coastal defense schemes.

Stalagmite multi-proxy records of weak Asian summer monsoon interval during Termination III as an analogue to Termination I

Multi-proxy analysis of abrupt climate change during Ice Age Termination III (T-III) is necessary to understand Asian summer monsoon (ASM) characteristics and mechanisms. We present 230Th dates and δ18O, δ13C, with equilibrium diameter, carbonate deposition amount and lithological characteristics from an annually laminated stalagmite (No. YXB) in Yongxing Cave, central China. Our multi-proxy records span 243.90 to 239.20 ka before present, falling within T-III/Marine Isotope Stage 7e. The changes in δ18O, equilibrium diameter, carbonate deposition amount, and lithological characteristics suggest a weak ASM interval during T III. By comparing these results with records from Ice Age Termination I (T-I), we find that the weakened ASM event during T-III is similar to the Younger Dryas (YD) event in terms of duration and structure. This result suggests that the YD-like event could be an inherent feature of glacial-interglacial climate cycles in the middle and late Pleistocene. The YXB δ13C sequence, without YD-like events, is broadly similar to the δ18O record on orbital timescale, indicating that variations in local vegetation could be driven by rising CO2 during ice age terminations.

Prolonged South Asian Monsoon variability and weakened denitrification during Mid-Pleistocene Transition

During Mid-Pleistocene Transition (MPT, 0.68 to 1.16 million years ago, Ma), the earth's climate cycle shifted from 41 kyr (thousand years) to quasi-100 kyr cyclicity. The South Asian Monsoon (SAM) variability and its forcing factors during MPT are not fully understood. We present a multiproxy record of productivity and denitrification related to SAM variability from the eastern Arabian Sea (IODP Expedition 355, Site 1457) during MPT. The denitrification and productivity vary distinctly during the early (1.19 Ma to 0.95 Ma), mid (0.95 Ma to 0.79 Ma), and late (0.79 Ma to 0.68 Ma) MPT. The long-term SAM variability followed the prolonged glacial-interglacial cycle as it shifted to quasi-100 kyr periodicity at 0.95 Ma. The SAM was strong (weak) during the interglacials (glacials) of MPT. During early MPT, the SAM intensity was high during one of the glacial periods (MIS 30) due to precessional and CO2 forcing. At mid-MPT, the denitrification anomalously decreases, possibly, due to enhanced oxygen solubility during the extended glacial period. During the various phases of MPT, both the dynamic (precession, interhemispheric insolation gradient) and the thermodynamic (CO2 variability) effects govern the SAM.