Milankovitch Cycles Research Articles

A 650-Myr history of Earth's axial precession frequency and the evolution of the Earth-Moon system derived from cyclostratigraphy.

The preservation of Milankovitch cycles in the stratigraphic record provides independent geological information to study our ancient solar system and can be leveraged to constrain existing theoretical models. Here, we identify 34 high-quality cyclostratigraphic records spanning the past 650 million years and use them to infer the evolution of the Earth-Moon system through a Bayesian inversion method. We reconstruct the time evolution of Earth's axial precession frequency, lunar distance, length of day, and the periods of obliquity and climatic precession cycles. The results indicate an interval of high tidal energy dissipation in the Earth-Moon system at ~300 to 200 million years ago, and are broadly consistent with an independently calculated tidal evolution model. Our results provide an improved determination of the past periods of obliquity and climatic precession for astrochronology applications and yield important constraints on the history of tidal energy dissipation during the Phanerozoic Eon.

High-precision cyclic correlation as a basis for detailed paleoclimatic reconstructions for the Pliocene-Quartenary sections of Eurasia

An astrochronological (cyclostratigraphic) binding of the lithological and geochemical characteristics of Pliocene-Quaternary sediments of the Eurasian sections to the Milankovich cycles (eccentricity, obliquity of the ecliptic, precession) was carried out, an analysis of the relationship between the established variations in climate and paleotemperature with the moments of coincidence of different-order cycles of eccentricity and their paleoclimatic characteristics was given. The results of the implementation of the results obtained during the practice in geology at the Moscow State University in Chashnikovo are shown. During the research, materials from the exposition space of the Department of Regional Geology and Earth History and the Museum of Earth Science were used. The results of the study were used in conducting an educational practice in geology in Chashnikovo, and can also be used in the dismemberment and regional and global correlation of sections, in conducting geological surveys, creating cyclostratigraphic scales of the plains and mountainous regions of Eurasia, as well as in the creation and further development of the exposition space of museums — Moscow State University Gymnasium for example.

Investigation of orbital and sub-orbital Milankovitch cycles from borehole logging data: Examples from Cretaceous and Quaternary lake sediments

Investigation of orbital and sub-orbital Milankovitch cycles from borehole logging data: Examples from Cretaceous and Quaternary lake sediments

Cyclostratigraphy of late Cambrian marine sedimentary records and reconstruction of Earth-Moon system parameters

The Cambrian period is an important era in geological history, marked by numerous major geological and biological events. To better understand these events, it is important to establish a high-precision chronostratigraphic framework. An astronomical time scale can be created by the identified Milankovitch cycles in well-preserved stratigraphic successions. Duibian B section in Jiangshan (Zhejiang Province, China) is the global stratotype section and point (GSSP) for the Jiangshanian Stage, and this section provides well-preserved records covering the upper Paibian to lower Jiangshanian stages. In this study, we use high-resolution magnetic susceptibility record to conduct cyclostratigraphic analysis of the Duibian B section. Our results indicate that the 2.44 m, 0.84–0.73 m, 0.20–0.19 m, and 0.12–0.09 m sedimentary cycles may represent long-eccentricity, short-eccentricity, obliquity, and precession cycles, respectively. Using the stable 405-kyr eccentricity cycles, we constructed an ∼5.96 Myr floating astronomical time scale to calibrate agnostoid trilobite zones. In addition, we reconstructed the precession rate k from geological records, and our result provides an insight into the Earth-Moon distance and length of day in the late Cambrian (Paibian–Jiangshanian, ∼494.2 Ma). It enriches our understanding of the Earth-Moon evolutionary history in deep time.

Cretaceous cyclic peritidal carbonates of the Apulia Carbonate Platform (Apulia, southern Italy) in a hierarchical sequence‐stratigraphic perspective: A case study from the Murge area (the Giovinazzo sea‐cliff section)

AbstractCretaceous cyclic peritidal carbonates form the bulk of the Apulia Region in Italy and represent the vestiges of the Apulia Carbonate Platform. To show from a sequence stratigraphic perspective the architecture of peritidal carbonates, the 17 m thick Albian Giovinazzo sea‐cliff section was studied at a centimetre detail, aiming to: (i) describe cyclic facies organisation in beds and bedsets; (ii) reconstruct the relative sea‐level curve and its evolution over time; (iii) interpret the long‐term evolution of the accommodation space in terms of sequence stratigraphy. The hierarchical stacking pattern of facies in beds and bedsets reveals Milankovitch cyclicity. As a working hypothesis, elementary sequences are assumed to represent the precession cycle (ca 20 kyr) and small‐scale and medium‐scale sequences the short (ca 100 kyr) and long (ca 400 kyr) eccentricity cycles, respectively. Four different types of elementary sequences (condensed, catch‐down, catch‐up and give‐up) are recognised and interpreted in terms of relative sea‐level changes to reconstruct the relative sea‐level curve of the entire succession. The envelope of the reconstructed relative sea‐level curve is used to represent the long‐term accommodation change on the platform, which covers a time span of approximately 1.8 Myr. Most of this time was spent in subaerial exposure, as approximately 1.2 Myr was predicted to be condensed in a stratigraphic interval encompassing both the sequence‐boundary zone/falling stage deposits and the lowstand deposits. Moreover, it was interpreted that about two‐third of the total thickness of the succession was formed in only 280 kyr and consisted of both transgressive and maximum‐flooding deposits. The main implication of this study is that unconformities do not necessarily correspond to single surfaces but, rather, to very amalgamated intervals or unconformity zones. Moreover, based on biostratigraphic constraints, there is a correlation between the unconformity zone of the studied succession and the third‐order KAl4 sequence boundary of the Cretaceous eustatic cycle chart.

Orbital forcing and paleoenvironmental changes across the upper Ordovician glaciation-lower Silurian hot shale in the Risha gas field, northeast Jordan

This paper presents a comprehensive analysis of sedimentary successions and paleoenvironmental indicators in two wells, Rh3 and Rh46, located in NE Jordan, within the context of the Ordovician-Silurian boundary transition. By integrating spectral analysis, cyclostratigraphy and sedimentary architecture, significant shifts and cyclical patterns are identified, shedding light on paleoenvironmental changes and orbital forcing dynamics. The study reveals distinct lithological and geochemical signatures at the Risha/Mudawwara (Hirnantian/Rhuddanian) boundary, indicative of major shifts in depositional environments. Analysis of Milankovitch cycles suggests orbital forcing as a driver of sedimentary cyclicity, with implications for understanding climatic variations during the Ordovician-Silurian transition. Spectral analysis revealed significant cycles with different periodicities. Testing the sediment accumulation rates (SAR) revealed an optimum SAR at 5.9 and 4.6 cm/kyr in Rh3 and Rh46 wells, respectively. A new refined astronomical time scale (ATS) is created based on the 100 kyr eccentricity cycle. The new ATS assigns the Risha Formation to the Hirnantian age and revealed a probable time gap at the base of Risha Formation of about 0.3 myr in Rh46 well; deposition of the Risha Formation commenced at 444.88 myr and 444.58 myr in Rh3 and Rh46 wells, respectively, with sedimentation continuing up to the Ordovician/Silurian boundary at 443.07 myr. The Ordovician/Silurian transition experienced shortening in the obliquity and precession cycles. The tuned data show that the 41, 36 and 31 kyr obliquity cycles, in addition the 21, 19 and 16 kyr precession cycles, were recognised. Furthermore, 740, 425, 250, 147 and 100 kyr eccentricity cycles were also recognised. Notably, the study identifies the glacial/fluvioglacial Risha Formation is bounded by g4-g3 eccentricity nodes coinciding with Hirnantian stage boundaries that correspond to significant geological events, such as the Late Ordovician Mass Extinction and the Hirnantian glaciation events. The g4-g3 eccentricity cycle is estimated to be 1.8 myr. Surprisingly, the lower Silurian OAE coincided with the g4-g3 eccentricity node at the Ordovician/Silurian transition. Additionally, the application of DYNOT modelling has elucidated sea-level fluctuations and their relationship with sedimentary sequences, highlighting the role of tectonic and climatic factors in shaping the sedimentary architecture. Furthermore, the investigation of Th/U and Th/K ratios provides insights into marine and terrestrial depositional settings.

Geographic variability in dust and temperature in climate scaling regimes over the Last Glacial Cycle

Abstract. Temperature and mineral dust records serve as valuable palaeoclimatic indicators for studying atmospheric variability across different temporal scales. In this study, we employed Haar fluctuations to analyse global spatiotemporal atmospheric variability over the Last Glacial Cycle, capturing both high- and low-frequency information within the records, regardless of uniform or non-uniform sampling. Furthermore, we utilised Haar fluctuations to compute fluctuation correlations, thereby enhancing our understanding of palaeoclimate dynamics. Our findings reveal a latitudinal dependency in the transition from macroweather to climate regimes (τc), with polar regions experiencing shorter transitions compared to the tropics and mid-latitudes. These transitions occur at approximately 1/100th of glacial cycle length scales, suggesting a dominant forcing mechanism beyond Milankovitch cycles. Additionally, our analysis shows that polar regions have larger fluctuation amplitudes than lower latitudes as a consequence of the polar amplification effect. Furthermore, fluctuation correlations demonstrate faster synchronisation between the poles themselves compared to lower-latitude sites, achieving high correlation values within 10 kyr. Therefore, our findings suggest a consistent climate signal propagating from the poles to the Equator, representing the first empirical evidence supporting the hypothesis that the poles play a pivotal role as climate change drivers, influencing the variability in climatic transitions worldwide.

Paleozoic Equatorial Records of Melting Ice Ages (PERMIA): calibrating the pace of paleotropical environmental and ecological change during Earth's previous icehouse

Abstract. The upper Paleozoic Cutler Group of southern Utah, USA, is a key sedimentary archive for understanding the Earth-life effects of the planet's last pre-Quaternary icehouse–hothouse state change: the Carboniferous–Permian (C–P) transition, between 304 and 290 million years ago. Within the near-paleoequatorial Cutler Group, this transition corresponds to a large-scale aridification trend, loss of aquatic habitats, and ecological shifts toward more terrestrial biota as recorded by its fossil assemblages. However, fundamental questions persist. (1) Did continental drift or shorter-term changes in glacio-eustasy, potentially driven by orbital (Milankovitch) cycles, influence environmental change at near-equatorial latitudes during the C–P climatic transition? (2) What influence did the C–P climatic transition have on the evolution of terrestrial ecosystems and on the diversity and trophic structures of terrestrial vertebrate communities? The Paleozoic Equatorial Records of Melting Ice Ages (PERMIA) project seeks to resolve these issues in part by studying the Elk Ridge no. 1 (ER-1) core, complemented by outcrop studies. This legacy core, collected in 1981 within what is now Bears Ears National Monument, recovered a significant portion of the Hermosa Group and the overlying lower Cutler Group, making it an ideal archive for studying paleoenvironmental change during the C–P transition. As part of this project, the uppermost ∼ 450 m of the core were temporarily transferred from the Austin Core Repository Center to the Continental Scientific Drilling Facility at the University of Minnesota for splitting, imaging, and scanning for geophysical properties and spectrophotometry. Here we (1) review the history of this legacy core, (2) introduce recently obtained geophysical and lithologic datasets based on newly split and imaged core segments to provide a sedimentological and stratigraphic overview of the Elk Ridge no. 1 core that aligns more accurately with the currently recognized regional lithostratigraphic framework, (3) establish the position of the boundary between the lower Cutler beds and the overlying Cedar Mesa Sandstone in the core, and (4) outline our ongoing research goals for the core. In-progress work on the core aims to refine biostratigraphic and chemostratigraphic age constraints, retrieve the polarity stratigraphy, interrogate preserved cyclostratigraphy, analyze sedimentary structures and paleosol facies, investigate stable isotope geochemistry, and evaluate elemental abundance data from X-ray fluorescence (XRF) scanning. Together with outcrop studies throughout Bears Ears National Monument and its vicinity, these cores will allow the rich paleontological and paleoenvironmental archives recorded in the continental Carboniferous–Permian transition of western North America to be confidently placed in a robust chronologic context that will help test hypotheses relating ecosystem evolution to the Carboniferous rainforest collapse, initial decline of the Late Paleozoic Ice Age, and long-wavelength astronomical cycles pacing global environmental change.

Millennial-scale climate cycles modulated by Milankovitch forcing in the middle Cambrian (ca. 500 Ma) Marjum Formation, Utah, USA

Abstract Middle Cambrian offshore deposits of the Marjum Formation, Utah, USA, are characterized by four scales of superimposed cyclicity defined by varying fine siliciclastic versus limestone abundances; these include limestone-marl couplets (rhythmites; 5–10 cm), which are bundled into parasequences (1–2 m) and small-scale (5–10 m) and large-scale (20–40 m) sequences. Time series analysis of SiO2 and lithologic rank stratigraphic series reveal cycles consistent with Milankovitch periods corresponding to Cambrian orbital eccentricity (20 m, 405 k.y.; 6 m, 110 k.y.), obliquity (1.8 m, 30 k.y.), climatic precession (1.15 m, 18 k.y.), and half-precession (0.64 m, 7 k.y.). Astronomical calibration of the lithologic rank series indicates that the main sub-Milankovitch cycle at 0.065 m represents ~1 k.y. and corresponds to the basic rhythmite couplet. All scales of cyclicity are interpreted as the result of wet versus dry monsoonal climate oscillations controlling the abundance of fine siliciclastic sediment influx to the basin. A plausible millennial-scale climate driver is solar activity. These results describe one of the oldest known geological candidates for solar-influenced climate change modulated by Milankovitch forcing.

Unveiling chromaticity and Milankovitch cycles in sedimentary rocks via unmanned aerial vehicle photogrammetry

Unveiling chromaticity and Milankovitch cycles in sedimentary rocks via unmanned aerial vehicle photogrammetry

The ∼170 kyr astronomical cycle in the Early Permian Lucaogou Formation of the Junggar Basin

According to Milankovitch’s theory, periodic climate change in Earth’s history is controlled by the periodic changes in the Earth’s orbit and axis of rotation. Milankovitch cycle include eccentricity, obliquity, and precession cycles. In addition to them, there are also some amplitude modulation (AM) cycles that affect the climate system through a series of “nonlinear” feedback processes, such as the 173 kyr obliquity AM cycle. Previous studies have demonstrated that the ∼170 kyr cycle modulate the paleoclimate and carbon cycle at mid-high latitude regions in the Meso-Cenozoic. However, due to the limitation of astronomical solutions and the lack of high-resolution geological records, the ∼170 kyr cycle has been less reported in the Paleozoic Era. In this study, cyclostratigraphic analysis of natural gamma ray (GR) logging data from four wells (Ji30, Ji31, Ji32, and Ji174) and total organic carbon (TOC) data from well Ji174 penetrating the Early Permian Lucaogou Formation in Jimusar Sag, Junggar Basin suggests preservation of eccentricity, obliquity, and precession cycles, and the ∼170 kyr AM cycle. Through the astronomical tuning of GR logging data obtained from four wells to eccentricity target cycles, we established the floating astronomical time scale (ATS). The results indicate an average sedimentation rate ranging from 7.4 to 9.5 cm/kyr and a duration from 2.8 to 3.2 million years (Myr) for the Lucaogou Formation. The differences in sedimentation rate and duration among these four wells may result from different well locations. Moreover, the ∼170 kyr cycle signal has been identified in the detrended GR logging and TOC data series, and its obliquity AM series. This signal might be attributed to the obliquity AM cycles originated from the interaction between s3 and s6 (s3 and s6 represent the precession of nodes of Earth and Saturn), which was recorded in the GR logging and TOC data time series due to nonlinear responses within the depositional system.

Assessing Water Deficit Induced Water Stress of Households and their Welfare in Small Cities of Nepal

This study investigates water deficit-induced stress in 12 small cities within Nepal's Marshyangadi River Basin, crucial for sustainable water management amid global water scarcity concerns. Employing the Milankovitch Theory, it explores Earth-Sun relationships and their impact on long-term climate changes, shaping societal adaptation strategies. Utilizing the Water Deficit Model, the study unveils the multifaceted consequences of water scarcity of Gandaki Province's Marshyangdi River basin. The study employs a comprehensive design, sampling 317 households across diverse ecological zones and elevations. The study finds the existing month-long water deficit in these cities to the higher water demand of households, along with water stress in the cities of Himal and Terai more than in the Hill. Water deficit is higher in Himal than in Hill and Terai because of lower water availability in Himal (below average 0.9). The people of Himal and Terai have extremely high stress but the people of Hills are comfortable without stress, except in Bandipur for drinking and cleanliness. In the 20 litres per capita per day water, water stress is found mixed. Five small cities in Himal and Terai are extremely stressed, meanwhile, 7 small cities in the Hill are not stressed, except two cities, Bandipur and Marshangdi. Relatively, the water deficit in the Hill is less than Himal and Terai. Similarly, in 20 liters per capita per day water, it is good for households but most cities have extreme water stress. The Hill’s water stress is lower than that of the Himalayan and Terai. By WHO’s standard (50 liters-100 liters per day per capita), all cities are extremely water deficient and critically water stressed. The findings reveal a direct correlation between water deficit and stress, impacting survival, hygiene, and living standards. The study concludes that despite ample water resources, poor governance and inadequate policies contribute to extreme water deficit, challenging SDG targets and living standards. It urges urgent action, accountability, budgeting, and a comprehensive plan for water poverty reduction.

Organic matter accumulation as a convergence response to astronomical forcing: Insights from Milankovitch periods and sea-level fluctuations during the early Cambrian

The accumulation of organic matter (OM) in marine sediments is a vital part of the global carbon cycle today and on ancient Earth, and is driven by a cumulative shift of organic carbon flux through oceans to marine sediments. This shift is a complicated process that is known to be influenced by the biological pump, diagenesis, and thermal alteration, so is affected by oceanic conditions and palaeo-climate, but less attention has been paid to the triggers of OM accumulation. Here, a set of marine sedimentary rocks from the early Cambrian in the southwestern part of the Yangtze Platform in China was used to search for clues to the triggers of OM accumulation. The effect of astronomical forcing, which potentially is a major control on Earth's oceanic conditions, was assessed via frequency analysis based on a high-resolution log dataset from a borehole in Yunnan Province. An astronomical time scale was constructed based on a 405,000 year-tuned filter. Palaeo-oceanic sedimentary conditions and palaeo-climate, which were recorded in the sedimentary rocks, were determined through geochemical analyses of major, trace, and rare earth elements. The mutual influence of astronomical forcing and the early Earth oceanic sedimentary conditions and paleoclimate were examined though Pearson Correlation analyses to provide evidence for the intensity of alteration of sedimentary conditions and the forces impacting the shift of organic carbon in the marine ecosystem. The results show that two convergence responses of OM accumulation were associated with ca. 1.5 and 2.4 million year (Myr) Milankovitch cycles. Fluctuations in sea level establish a connection between Milankovitch forcings and changes in sedimentary conditions, thereby providing evidence for the triggering of a cumulative shift of OM flux to sediments, and the effect of astronomical forcing on the organic carbon cycle.

Deep-sea hiatus record reveals orbital pacing by 2.4 Myr eccentricity grand cycles

Astronomical forcing of Earth’s climate is embedded in the rhythms of stratigraphic records, most famously as short-period (104–105 year) Milankovitch cycles. Astronomical grand cycles with periods of millions of years also modulate climate variability but have been detected in relatively few proxy records. Here, we apply spectral analysis to a dataset of Cenozoic deep-sea hiatuses to reveal a ~2.4 Myr eccentricity signal, disrupted by episodes of major tectonic forcing. We propose that maxima in the hiatus cycles correspond to orbitally-forced intensification of deep-water circulation and erosive bottom current activity, linked to eccentricity maxima and peaks in insolation and seasonality. A prominent episode of cyclicity disturbance coincides with the Paleocene-Eocene Thermal Maximum (PETM) at ~56 Myr ago, and correlates with a chaotic orbital transition in the Solar System evident in several astronomical solutions. This hints at a potential intriguing coupling between the PETM and Solar System chaos.

Zanclean to gelasian high-frequency sequences of the crotone basin (southern Italy): Architectural variability and forcing mechanisms

The Zanclean Belvedere Formation and the Gelasian Strongoli Sandstone, cropping out in the Neogene to Quaternary Crotone Basin, southern Italy, exhibit a high-frequency cyclicity consisting of 10°–101 m sequences, which stack in an aggradational to progradational pattern. These high-frequency sequences are bounded by ravinement surfaces and are usually composed of transgressive and regressive deposits of similar thickness. In particular, the high-frequency sequences of the Belvedere Formation are composed of a transgressive systems tract and of a highstand systems tract, whereas those of the Strongoli Sandstone likely record also forced regression in their upper part. Due to the vertical repetition of the studied high-frequency sequences and their similar architecture despite the different tectonic settings in which the two formations accumulated, a climatic/glacio-eustatic control associated with earth-orbital parameters is very likely, as also documented in coeval successions worldwide. This contribution refines the correlation between shallow-marine sequences and their deep-water counterparts, which preserve a better record of the Milankovitch cyclicity.

Toward generalized Milankovitch theory (GMT)

Abstract. In recent decades, numerous paleoclimate records and results of model simulations have provided strong support for the astronomical theory of Quaternary glacial cycles formulated in its modern form by Milutin Milankovitch. At the same time, new findings have revealed that the classical Milankovitch theory is unable to explain a number of important facts, such as the change in the dominant periodicity of glacial cycles from 41 to 100 kyr about 1 million years ago. This transition was also accompanied by an increase in the amplitude and asymmetry of the glacial cycles. Here, based on the results of a hierarchy of models and data analysis, a framework of the extended (generalized) version of the Milankovitch theory is presented. To illustrate the main elements of this theory, a simple conceptual model of glacial cycles was developed using the results of an Earth system model, CLIMBER-2. This conceptual model explicitly assumes the multistability of the climate–cryosphere system and the instability of the “supercritical” ice sheets. Using this model, it is shown that Quaternary glacial cycles can be successfully reproduced as the strongly nonlinear response of the Earth system to the orbital forcing, where 100 kyr cyclicity originates from the phase locking of the precession and obliquity-forced glacial cycles to the corresponding eccentricity cycle. The eccentricity influences glacial cycles solely through its amplitude modulation of the precession component of orbital forcing, while the long timescale of the late Quaternary glacial cycles is determined by the time required for ice sheets to reach their critical size. The postulates used to construct this conceptual model were justified using analysis of relevant physical and biogeochemical processes and feedbacks. In particular, the role of climate–ice sheet–carbon cycle feedback in shaping and globalization of glacial cycles is discussed. The reasons for the instability of the large northern ice sheets and the mechanisms of the Earth system escape from the “glacial trap” via a set of strongly nonlinear processes are presented. It is also shown that the transition from the 41 to the 100 kyr world about 1 million years ago can be explained by a gradual increase in the critical size of ice sheets, which in turn is related to the gradual removal of terrestrial sediments from the northern continents. The implications of this nonlinear paradigm for understanding Quaternary climate dynamics and the remaining knowledge gaps are finally discussed.

Orbital and Millennial‐Scale Cycles Through the Hirnantian (Late Ordovician) in Southern China

AbstractThe Hirnantian period, making the end of the Ordovician with significant mass extinctions and large ice‐sheets, is a critical interval for studying paleoclimate variations. This research represents the first cyclostratigraphic study of this period, utilizing high‐resolution (1 mm sampling rate) geochemical data from the ∼7‐m thick SH‐1 drill core, capturing the latest Ordovician glaciation. Our analysis identifies the presence of Milankovitch cycles with periods of 17–21, ∼33, and ∼100‐kyr, suggesting an optimal sedimentation rate of 3.1 m/Myr. Notably, we detected signals of millennial‐scale variability, aligning with the ∼1.5‐kyr Dansgaard‐Oeschger and ∼2.4‐kyr Hallstatt heliomagnetic cycles, even in deposits lacking visible laminae alternation. This finding bolsters the hypothesis of an external origin for these millennial‐scale features. Additionally, our reconstruction of sea‐level variations, using principal component analysis and sedimentary noise modeling, reveals two intervals of sea‐level fall and one sea‐level rise, linked to an astronomical forcing cycle of ∼1.2‐Myr. The obliquity band power‐total power ratios correspond to ∼1.2‐Myr periodicities for s4‐s3 term. The synchronization of ∼1.2‐Myr cycle minimum with a sea‐level drop (low PC1 value) suggests that glacio‐eustatic variations were influenced by ∼1.2‐Myr obliquity modulation cycles. This research enhances our understanding of glacio‐eustasy during the latest Ordovician from an astronomical perspective, offering valuable insights into the interplay between orbital cycles and Earth's paleoclimate.

Exponential feedback effects in a parametric resonance climate model

The variations in the distribution of solar radiation due to the ~ 105 years Milankovitch cycle, which is connected to the Earth eccentricity variation, cannot explain the sharp drop in temperature of 6 °C ÷ 10 °C that marks the transition from the interglacial to the glacial age registered in the last ~ 5.5 106 years temperature variation behavior. More specifically, neglecting other effects, only a temperature variation of 0.2 °C ÷ 0.3 °C can be attributed to this cycle and, therefore, positive feedback effects should be taken into account to explain the registered effect. In the present work, a comparative Wavelet-Fourier analysis of the Vostok recontructed temperature record, for which different sampling steps are taken into account, is performed. Then, a study of exponential feedback effects within a climate parametric resonance model is dealt and discussed. The obtained findings put into evidence an exponential amplification of the temperature variation from the interglacial to the glacial age supporting the hypothesis that the system energization be connected to periodic variations in the internal solar system parameters. More in details, it is shown that, following the parametric resonance climate model, even small oscillations increase over time proportionally to the system energy itself, i.e. exponentially, and hence, a series of connected resonances is able to energize the climate system.

Milankovitch cycles recorded by the Late Permian volcanic ash layers in southwestern China

The volcanic activity during the Cenozoic is thought to be forced by Earth's orbit, as it exhibits the Milankovitch cycle. However, the pattern of volcanic activity before the Cenozoic is still unclear. In this study, we studied the volcanic ash-bearing layers preserved in Upper Permian in Southwestern China and analyzed the cycle of volcanic activity from Emeishan Large Igneous Province (ELIP) during the waning stage of Emeishan mantle plume activity. Mineralogy, geochemistry, and gamma-ray (GR) data were used for high-resolution identification of volcanic ash-bearing layers. Al2O3/TiO2, aluminum normalized Th and Sn, and positive anomalies GR data can reflect volcanic ash input. The 206Pb/238U weighted age of zircon ranges from 256.00 ± 2.00 Ma to 251.47 ± 1.29 Ma, indicating synsedimentary volcanic ash. We apply cyclostratigraphic analysis to convert data from the depth domain to the time domain, and then utilize the multitaper method to analyze the cycle of volcanic activity of ELIP. Spectral analysis results reveal that the volcanic activity has long eccentricity (405-kyr), obliquity (∼33-kyr), and precession (∼20-kyr) periods. We propose the astronomical orbital forcing in volcanic activity during the Late Permian, and we have discovered volcanic activity cycles on a larger timescale of astronomical orbital periods (405-kyr long eccentricity). Volcanic activity was significantly correlated with sea level and climate change. During periods of low sea levels, the hot climate causes rapid sea level change, leading to rapid changes in crustal stress and strong volcanic activity. The absolute sea level controls volcanic activity, and the high sea levels suppress volcanic activity.

Turbulent paleoenvironment linked to astronomical forcing during the Permian–Triassic transition

The Milankovitch cycles are essential for establishing high-resolution chronological frameworks, which can provide a reliable timescale for biological and environmental events. However, astronomical solutions for the Paleozoic are still imperfect. Moreover, global paleoenvironmental turbulence during the Permian-Triassic (PT) transition caused interference with most proxies reflecting astronomical cycles. This study discovered that the Sb/Cd series can reflect astronomical cycle signals through a time-series analysis of geochemical elemental data from cores around the Lopingian–Lower Triassic in the Lower Yangtze region. Combined with zircon SHRIMP dating of volcanic ashes, a reliable absolute astronomical timescale with a duration of 2.5 Myr was established from 100-kyr eccentricity-tuned results. Based on the coupling analysis of palaeoenvironmental proxies, this study evaluated the effect of astronomical forcing and volcanism on the paleoenvironment. The sea level change was influenced by obliquity during the Lopingian–Early Triassic. During the Wuchiapingian–Changhsingian (WC) and PT transitions, regional volcanic activities at South China and the Siberian Traps Large Igneous Province (STLIP) intervened the normal trend of a low-temperature arid climate dominated by the obliquity forcing, respectively. Thus, South China exhibited a hot humid climate during the WC and PT transitions. Conversely, the low-temperature climate in South China was significantly modulated by obliquity forcing during the middle Changhsingian. Besides the influences of intense igneous activities and related environmental effects, disruption the long-term stable low-temperature environment by the abnormal high-temperature around the PT transition was a tremendous challenge to the biological ecological adaptation, and thereby may have contributed to the end-Permian mass extinction.