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The study of fine-grained sedimentation has consistently concentrated on investigating the mechanisms and principles governing the enrichment of organic matter. However, the lack of unified stratigraphic framework has always existed as fine-grained sedimentation covers two distinct grain-size grades, namely, mud and silt, which has impeded the progress of subsequent production research. This study exemplified this issue by analyzing the first member of the Qingshankou Formation in the southern Songliao Basin. We established reconstructed gamma and density curves that mitigated filter noise interference, integrated high-resolution sequence results with astronomical cycle divisions, and created a high-frequency isochronous stratigraphic framework for clastic fine-grained sedimentation by leveraging the weak sensitivity of sandstone density curves and the robust stability in eccentricity cycle extraction. This approach addresses the inconsistencies in stratigraphic division methodologies and mismatched outcomes stemming from the use varying techniques to delineate mud and silt components within clastic fine-grained sedimentary sequences. Furthermore, it elucidates how tectonic-scale variations in sediment supply coupled with potential accommodation changes dictate macroscopic stacking patterns within strata, whereas climate fluctuations on orbital time scales govern sand-mud progradation degrees within these layers, culminating in periodic rhythmic characteristics characterized by vertical sand-mud interbedding. A model for stratigraphic development pertaining to lake delta systems constrained by a "synchronous heterotopy" paradigm is proposed for the southern Songliao Basin. The organic matter enrichment pattern aligns with its filling dynamics, indicating an "overfilling" type developmental pattern at lower strata levels where organic material predominantly originates from terrestrial plant debris external to the basin; this material accumulates primarily within silty zones along layers—with areas exhibiting heightened enrichment values slightly lagging behind short-eccentric maxima positions. In contrast, under an upper "balanced filling" type developmental framework, sources of organic matter are derived both internally and externally relative to the basin—exhibiting substantial heterogeneity—and regions marked by elevated organic matter concentrations are directly associated with locations identified as short-eccentric maxima. [ABSTRACT FROM AUTHOR]

The Messinian-Zanclean boundary in the Mediterranean basin marks the end of the Messinian salinity crisis (MSC) at approximately 5.33 Ma. The mechanism behind the return to normal marine conditions after the MSC are debated, with two main hypotheses proposed: an instantaneous reflooding of the Mediterranean at the base of the Zanclean, following its near-complete desiccation, or a gradual sea level rise in a non-desiccated basin during the late MSC phase (Lago-Mare). Our objectives are to refine the age model of the Pollenzo section in the Piedmont basin, Italy, and to elucidate environmental variability during this phase. We employ high-resolution biomagnetostratigraphic and cyclostratigraphic analyses, integrated with statistical multivariate and cluster analyses, and tie the results with other Italian Mediterranean reference sections of the basal Zanclean. The proposed age model is based on biostratigraphic markers (planktic foraminifera and calcareous nannofossils), alongside the identification of the base of the Thvera subchron. Although no astrochronological tuning was proposed, the influence of orbital parameters variation on calcareous plankton was noted, especially at tie of eccentricity maxima. Our results indicate a gradual restoration of open marine conditions after the MSC, spanning from 5.33 to 5.23 Ma. We observe a transition from a more marginal environment to more open marine conditions at the termination of MSC. Our findings challenge the notion of an abrupt transition at the end of the MSC, emphasizing the gradual nature of environmental change in the northernmost Mediterranean basin, from the late Messinian to the early Zanclean. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Paleoclimate proxy records from regions sensitive to humidity/aridity extremes provide crucial insights into the natural forcing mechanisms underlying long‐term climate variability in broader regions. One such area is Northwest Australia, where the Australian monsoon impacts its northernmost fringes, which are bordered by the Great Sandy Desert inland. Marine sediments from the Australian Northwest Shelf record fluvial run‐off and eolian dust input during the wet and dry seasons, respectively. The location is therefore ideal for investigating long‐term variability in the Australian monsoon and Northwest Australian dust flux over orbital timescales. However, there are few continuous, high‐resolution paleoclimate records from this region spanning the early Pleistocene, when strong ice‐climate feedbacks of the late Pleistocene did not yet dominate global climate. Here, we present geochemical and environmental magnetic proxy records that reveal %CaCO3 and dust‐flux variability between 2.9 and 1.6 million years (Myr) ago from International Ocean Discovery Program Expedition 356 Site U1464 on the Australian Northwest Shelf. We establish a new, orbitally‐tuned chronology for Site U1464, primarily based on ∼400 thousand year (kyr) eccentricity cyclicity in %CaCO3, and observe strong obliquity variability (41 and 54 kyr periodicities) but almost no precession signal in the dust‐flux records. We propose that the 41 kyr cycle in Northwest Australian dust flux could be a linear response to East Asian winter monsoon intensity and/or the summer inter‐tropical insolation gradient (SITIG), whereas the 54 kyr cyclicity might be a non‐linear response to obliquity amplitude modulation via the SITIG effect on the cross‐equatorial atmospheric circulations. Key Points: This study establishes a new orbitally‐constrained chronology for International Ocean Discovery Program Site U1464Australian Northwest shelf sediments preserve ∼400 kyr eccentricity cycles in %CaCO3 and ∼41 kyr obliquity cycles in dust proxy recordsObliquity in Northwest Australian dust flux may be related to the East Asian winter monsoon and summer inter‐tropical insolation gradient [ABSTRACT FROM AUTHOR]

Our understanding of the paleoclimate of Mars and the dominant forcing functions that drive large‐scale changes largely remains a mystery. However, the Martian Polar Layered Deposits (PLD) offer a promising avenue for unraveling the planet's recent paleoclimate history. Despite recent progress to detect a climate signal in the PLD, definitive evidence of a correlation between the stratigraphic record and Mars' recent orbital history remains elusive. We utilized new and updated techniques, including high‐resolution stratigraphic reconstruction from High Resolution Imagine Science Experiment stereo imagery and digital terrain models, combined with a technique of variable dip correction to account for three dimensional bedding orientations. Signal processing methods, such as wavelet and Fourier analysis, were applied to perform detailed time‐series analysis. These analyses revealed a quasi‐periodic signal indicative of fine bedding at a scale of approximately 2 m. Based on previously proposed deposition rates, these fine layers appear to correspond to timescales centering around 4,000 years. This suggests that the meter‐scale layers may not be the result of orbital forcing and hint at an unknown sub‐Milankovitch climate forcing mechanism. We discuss potential exogenic causal mechanisms, such as cyclic variations in solar activity, and endogenic factors, including large‐scale changes in dust distribution. Understanding the formation processes of these fine layers may significantly enhance our knowledge of Martian climate history and its driving forces. Plain Language Summary: In this paper, we investigate the presence, distribution, and significance of small‐scale layers in the northern polar layered deposits (PLD) of Mars. Solar radiation is a key variable in determining the long‐term evolution and stability of the polar caps, and it is closely linked to changes in the planet's orbit, such as precession, eccentricity, and obliquity. We argue that the thickness and periodicity of these fine layers reflect a causal mechanism that cannot be attributed solely to climate changes resulting from the long‐term evolution of Mars' orbit. Based on proposed accumulation rates of the polar ice, we suggest that the quasi‐periodic bedding may represent a climate signal occurring on timescales several orders of magnitude shorter than those of the orbit changes in Mars, centering around 4,000 years. These observations help to characterize and better understand the PLD and their formation. Key Points: Meter‐scale bedding is widespread throughout Mars northern polar layered depositsUsing image and topographic data, we show that the fine bedding is quasi‐periodic within a confined range of wavelengths from 1.5 to 3 mUnder previous deposition rate estimates, meter‐scale bedding corresponds to ∼ ${\sim} $4,000‐year, sub‐Milankovitch timescales [ABSTRACT FROM AUTHOR]

While the Cretaceous Normal Polarity Superchron has documented instances of brief reversed polarity intervals, the absence of accurate age determinations for such abrupt shifts poses a challenge in leveraging them as reliable reference tiepoints. This study presents a cyclostratigraphic analysis of gamma‐ray data from the DSDP Site 402A. The identification of Milankovitch cycles allowed us to construct a 405‐kyr astronomically‐tuned age model for two reversed events that occurred in the Aptian. Our results estimate an age of 117.03 ± 0.14 Ma for the Chron M"‐1r" or ISEA and 116.17 ± 0.14 Ma for reversal "2," with timespans of ∼20 and ∼10 kyr, respectively. Sedimentation patterns are influenced by orbital eccentricity cycles with an average sedimentation rate of 5 cm/kyr. The short time intervals related to these reversals exposes the difficulty in their detection in cores through paleomagnetic analysis as well as in deep‐tow surveys. Plain Language Summary: The Cretaceous Normal Polarity Superchron (CNPS) was characterized as a "quiet zone," which includes no geomagnetic reversals during ∼38 Myr. A number of studies propose significant fluctuations in geomagnetic intensity, with distinct features observed in paleosecular variations, including periods of reversal events, and the actual occurrence, timespan and ages for these rapid magnetozones have been under debate in literature. This paper provides the age and constrains the timespan of two of these debated reversals (i.e., M"‐1r" or ISEA, and "2") during the CNPS. The determination of the age of the reversals during the CNPS is a fundamental support for global correlations. Key Points: Orbital tuning for M‐1r (ISEA) has an age of 117.03 ± 0.14 Ma and a timespan of 20 kyrThe reversal "2" has an age of 116.16 ± 0.14 Ma and a minimum timespan of 10 kyrDSDP Site 402A has an average 5 cm/kyr sedimentation rate and eccentricity Milankovitch cycles rules sedimentation patterns [ABSTRACT FROM AUTHOR]

The Earth has witnessed the emergence of continental-sized ice sheets, starting with Antarctica and gradually extending to both hemispheres over the past 40 million years. These ice accumulations have had a dramatic impact on both paleoclimate and sea level, substantially influencing sediment deposition in the continental margins. However, understanding sediment accumulation on an orbital scale in continental margins remains limited because of the scarcity of high-resolution, chronologically constrained sedimentary records. Here, we conducted a highly resolved cyclostratigraphic analysis based on natural gamma radiation (GR) series in depth domain at the continental margin of the South China Sea. We established a 22.8 m.y.-long high-resolution astronomical time scale spanning from the Miocene to the Quaternary by tuning the GR records to the global deep-sea benthic foraminifera carbon isotope curves and the 405 k.y. eccentricity cycles. The m.y.-scale sea-level changes since the Miocene were reconstructed through the sedimentary noise modeling of the 405-k.y.- tuned GR series. These reconstructions aligned with regional and global sea-level changes. The phase correlation between the filtered 1.2 m.y. cycles of sea-level change curves (dynamic noise after orbital tuning and ρ1 median models) from δ13Cbenthic and tuned GR series and the 1.2 m.y. obliquity amplitude modulation cycles revealed a shift from an anti-phase to an in-phase relationship across the middle Miocene climate transition (ca. 13.8 Ma), suggesting extensive expansion of the Antarctic ice sheet played a key role. In addition, a shift from an in-phase to an anti-phase relationship during the late Miocene (ca. 8 Ma and 5.3 Ma), indicating ephemeral expansion of the Arctic ice sheets or the changes in carbon cycle involving the terrestrial and deep ocean carbon reservoirs, might be the primary driver of eustatic changes. Furthermore, obliquity forcing and changes in meridional gradients in insolation that transported poleward flux of heat, moisture, and precipitation increased ice accumulation in both pole ice sheets and nonlinearly transferred high-latitude signals to low-latitude regions. This phenomenon is supported by the observation of strong obliquity signals in low latitude during global climate cooling interval. Our results suggest that m.y.-scale sea-level variations respond to astronomically induced climate change and ice sheet dynamics of both poles. This work contributes a highly resolved low-latitude geological archive to the future reconstruction of paleoclimate evolution on a global scale. [ABSTRACT FROM AUTHOR]

East Asia experienced complex climatic changes during the Eocene. Due to the lack of a high‐precision time framework covering the Eocene, the characteristics of sedimentary and climate evolution in this period remain unclear. The Jianghan Basin (Central China) developed an Eocene continental succession, which is composed of lower red beds and upper salt‐lake deposits exhibiting clear sedimentary rhythms, making these strata an ideal target for astronomical cycle analysis. Based on the established floating astronomical timescale, the lower red beds in the basin formed during the early–middle Eocene and were dominated by eccentricity cycles. The upper salt‐lake deposits formed during the middle–late Eocene and recorded obliquity cycles. The change in facies indicates that the climate transitioned from continuously arid to less arid with periodic relative wetness, which was forced by orbital cycles. Significant obliquity signals recorded by salt rhythmites responded to Eocene global temperature changes and Tibetan region uplift, which can be important markers of a monsoon‐like climate. Comparing the sedimentary and climatic characteristics of other Eocene lake basins in East Asia, the extension of the Eocene East Asian monsoon may have initiated during ca 43.6 to 40.0 Ma. This study provides a new perspective for understanding the early evolution of the East Asian monsoon. [ABSTRACT FROM AUTHOR]

Numerical forward modelling and laboratory experiments suggest that autogenic factors in the sediment routing system serve as long‐pass filters, preserving only orbital cycles with a period exceeding the compensation timescale, Tc, or thickness in the depth domain exceeding the compensation depth scale, Hc. For a specific orbital cycle with a certain period, this preservation in alluvial strata occurs unless it exhibits a sufficiently large amplitude. This study stratigraphically confirms, for the first time, the long‐pass filtering of autogenic dynamics using elemental data from the alluvial–lacustrine Sifangtai and Mingshui formations in the Songliao Basin. Spectral analysis of the Si and Zr series in coarse‐grained sediments reveals no cyclic signal with thicknesses below the estimated lower limits of Hc. This implies that the spatial storage threshold for orbital cycles in proxies of the coarse‐grained sediment component is equal to or less than Hc. However, cyclic signals of obliquity and precession with smaller thicknesses are identified in Ti, Fe and Al enriched in the fine‐grained sediment components of the stratigraphy. Notably, previously reported proxies preserving high‐frequency orbital cycles are derived from fine‐grained sediment components, differing from the sedimentation rate series used in the reported experimental studies. Therefore, the authors hypothesize a grain‐size component‐dependent storage threshold, suggesting that the storage threshold of orbital cycles in proxies associated with fine‐grained components is lower. This hypothesis arises from the weaker effect of autogenic dynamics on the content of fine‐grained sediment components transported to the sampling site by a suspended load compared to coarser components that are subjected to stronger autogenic dynamics within or near channels. The hypothesis and model presented propose a dynamic process elucidating the nuanced roles of autogenic dynamics in preserving orbital cycles. This perspective, considering sediment composition, inspires prioritizing proxies enriched in the fine‐grained fraction for identifying allogenic cycles in alluvial strata. [ABSTRACT FROM AUTHOR]

Cyclostratigraphy is an important observational window into the history of the Earth-Moon system. However, there is limited information from the Mesoproterozoic era (1.0 to 1.6 billion years ago); accordingly, only weak constraints on Earth-Moon separation and tidal dissipation are available for this time. To close this knowledge gap, we analyze cyclostratigraphy from the Yemahe Formation (~1.2 billion years ago), Wumishan Formation (~1.5 billion years ago), and Chuanlinggou Formation (~1.6 billion years ago) in China. We use a Bayesian inversion method to analyze the three cyclostratigraphic sections. We combine previous results with these three estimates to construct an updated Earth-Moon system evolution and tidal dissipation history after 2.5 billion years ago. The results show a tidal dissipation peak that is consistent with the model predictions within the error range but also that there may be an additional resonance fluctuation in the Mesoproterozoic era. [ABSTRACT FROM AUTHOR]

The article focuses on climate cycles during the middle Cambrian period in the Marjum Formation of Utah, using sedimentological and geochemical data to understand the impact of Milankovitch forcing on sedimentation patterns. It identifies millennial-scale rhythmite couplets and interprets their formation as a result of interactions between local sediment transport processes and regional climatic variations, including shifts in monsoon intensity and sea-level changes.

Alluvial stratigraphy builds up over geologic time under the complex interplay of external climatic and tectonic forces and internal stochastic processes. This complexity makes it challenging to attribute alluvial stratigraphic changes to specific factors. Geological records indicate pronounced and persistent climatic changes during the Phanerozoic, while the effects of these changes on alluvial stratigraphy remain insufficiently documented. We provide evidence for 405 k.y. long-eccentricity climate forcing of alluvial stratigraphy in the lower Eocene Willwood Formation of the Bighorn Basin, Wyoming (USA). Two ∼90-m-thick intervals, characterized by a relative paucity of sand, dominance of sinuous-river channels, and floodplain sediments with better-developed paleosols, coincide with eccentricity maxima as determined through integrated stratigraphic methods. These intervals are interspersed with three contrasting intervals, marked by relatively high sand content, prevalent braided-river channels, and less-developed paleosols, corresponding to eccentricity minima. A comprehensive genetic model that integrates climate, source-to-sink system, and alluvial dynamics to explain these findings remains to be elucidated. Given the consistent presence of the 405 k.y. eccentricity cycle throughout Earth’s history, it is plausible to infer that its influence may be discernible across a wide array of alluvial stratigraphic records. [ABSTRACT FROM AUTHOR]

Astronomical cycles reliably identified in the sedimentary record are useful for their paleoclimatic interpretations and construction of astrochronology. However, the depositional response and burial-diagenesis processes play a crucial role in distorting the time scales of geological records and introducing noise to orbital signals. How to evaluate the response of varied depositional environments to astronomical forcing remains a challenge. We developed the random-length average orbital power ratio calculation (RAOPR) method to evaluate average orbital power ratio distributions within a specific time interval and applied this new method to the theoretical eccentricity-tilt-precession (ETP) plus noise series and an astronomically tuned Cretaceous terrestrial stratigraphic record spanning ~24 m.y. (92-65 Ma, except for an ~3.8 m.y. gap from ca. 79.9 Ma to 76.1 Ma). Using the merged ETP plus noise series, we observed different orbital power ratio distributions for different background noise intervals. For the Cretaceous terrestrial Songliao Basin, we retrieved long-term orbital variations and used the RAOPR method to calculate the average orbital power ratios in different depositional environment intervals. Our results suggest that unusually high precession power in the Yaojia Formation resulted, in part, from autogenic processes, and unusually low precession power in the Nenjiang Formation can be attributed to marine incursion events. The eccentricity power of the meandering river facies was much higher than observed in other facies intervals. Conversely, the lowest precession power in the meandering facies may be attributed, in part, to the erosion "clipping" effect, which decreases the high-frequency precession band power and increases low-frequency eccentricity band power. [ABSTRACT FROM AUTHOR]

The rhythmic evaporation cycle is an ideal recorder of astronomical cycle signals, but studies on cyclostratigraphy have yet to be directly conducted on halite-rich strata. The Qianjiang Depression of the Jianghan Basin is a representative Eocene East Asian halite-rich basin, and the salt rhythmites that developed therein are important recorders of climate evolution in East Asia. This study selected five wells for basin-scale cyclostratigraphy analysis, taking the Lower Qian 4 member of the Qianjiang Formation as the research object. This study found that the basinal salt lake facies were dominated by obliquity cycles, whereas the shallow-water deposits mainly recorded short eccentricity cycles. The study also found that s3-s6 obliquity cycles could be detected throughout the salt lake sedimentary record. Therefore, a stepwise astronomical tuning scheme was adopted. First, the target intervals in different sedimentary areas were preliminarily tuned to s3-s6 obliquity cycles, and stratigraphic correlation was performed. Then, the tuned data were further adjusted using obliquity cycles to reveal the impact of obliquity on the development of salt rhythmites and establish a floating astronomical time scale (ATS). Sedimentary noise models and pollen analysis further demonstrated that obliquity amplitude modulation cycles drove periodic changes in hydrology and climate. Based on the spatiotemporal distribution of salt rhyth-mite-rich strata in Paleogene East Asia, this study proposes that the development of rhythmic evaporites can reveal the existence of a monsoon-like climate. Astronomical influence was an important driving force for developing the middle Eocene East Asian monsoon. [ABSTRACT FROM AUTHOR]

Lower Pliensbachian hemipelagic successions from the northern Iberian palaeomargin are characterized by the occurrence of organic-rich calcareous rhythmites of decimetre-thick limestone and marl beds as well as thicker black shale intervals. Understanding the genetic mechanisms of the cyclic lithologies and processes involved along with the nature of the carbon cycle is of primary interest. This cyclostratigraphic study, carried out in one of the black shale intervals exposed in Santiurde de Reinosa (Basque–Cantabrian Basin), reveals that the calcareous rhythmites responded to periodic environmental variations in the Milankovitch-cycle band and were likely driven by eccentricity-modulated precession. The main environmental processes that determined the formation of the rhythmite were deduced on the basis of the integrated sedimentological, mineralogical, and geochemical study of an eccentricity bundle. The formation of precession couplets was controlled by variations in carbonate production and dilution by terrigenous supplies, along with periodic changes in bottom-water oxygenation. Precessional configurations with marked annual seasonality increased terrigenous input (by rivers or wind) to marine areas and boosted organic productivity in surface water. The great accumulation of organic matter on the seabed eventually decreased bottom-water oxygenation, which might also be influenced by reduced ocean ventilation. Thus, deposition of organic-rich marls and shales occurred when annual seasonality was maximal. On the contrary, a reduction in terrestrial inputs at precessional configurations with minimal seasonality diminished shallow organic productivity, which, added to an intensification of vertical mixing, contributed to increasing the oxidation of organic matter. These conditions also favoured greater production and basinward export of carbonate mud in shallow marine areas, causing the formation of limy hemipelagic beds. Short eccentricity cycles modulated the amplitude of precession-driven variations in terrigenous input and oxygenation of bottom seawater. Thus, the amplitude of the contrast between successive precessional beds increased when the Earth's orbit was elliptical and diminished when it was circular. The data also suggest that short eccentricity cycles affected short-term sea level changes, probably through orbitally modulated aquifer eustasy. [ABSTRACT FROM AUTHOR]

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 1/100 th 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. [ABSTRACT FROM AUTHOR]

Late Pleistocene glacial terminations are caused by rising atmospheric CO2 occurring in response to atmospheric and ocean circulation changes induced by increased discharge from Northern Hemisphere ice sheets. While climate records place glacial terminations coincident with decreasing orbital precession, it remains unclear why a specific precession minimum causes a termination. We compare the orbital and ice volume configuration at each precession minima over the last million years to demonstrate that eccentricity, through its control on precession amplitude, period and coherence with obliquity, along with ice sheet size, determine whether a given precession minimum will cause a termination. We also demonstrate how eccentricity controls obliquity maxima and precession minima coherence, varying the duration of glaciations. Glaciations lasting ∼100 thousand years are controlled by Earth's eccentricity cycle of the same period, while the shortest (20–40 ka) and longest (155 ka) occupy the maxima and minimums of the 400 thousand year eccentricity cycle. Plain Language Summary: The Milankovitch theory of the ice ages predicts that the growth and collapse of Pleistocene ice sheets is paced by the cycles in high latitude solar insolation that accompany variations in Earth's orbital motion. The orbital modes that dominate frequencies of incoming solar radiation are obliquity and precession, which operate at periodicities of approximately 40 and 20 thousand years, respectively. The dominant frequency at which ice sheets grow and collapse over the last million years is, however, approximately 100 thousand years, a closer match to eccentricity, an orbital period near absent from past solar radiation. Through a comparison between Earth's orbital configuration and an approximation of past global ice volume, we identify that the precession minima that trigger ice sheet collapse occur at distinct configuration of eccentricity and ice sheet size. In most cases terminations occur when precession minima align with obliquity maxima. We find that this coherence is influenced by the duration of precession cycles, which is in turn controlled by eccentricity. From these observations, we conclude that orbital eccentricity, through its control on both the amplitude and period of precession, paces the timing of glacial terminations and the size of Late Pleistocene ice sheets. Key Points: Late Pleistocene glacial terminations occur at distinct configurations of orbital precession, obliquity, eccentricity and ice volumeEccentricity controls the duration of precession cycles, and therefore the coherence of obliquity and precessionOrbital eccentricity, through its control on the amplitude and period of precession, paces Late Pleistocene glaciations [ABSTRACT FROM AUTHOR]

The coal‐bearing series of the Eocene Pinghu Formation is one of the focused reservoir exploration in the Xihu Sag. This study conducted a cyclostratigraphy time series analysis using natural gamma‐ray (GR) logging data from four boreholes of the Xihu Sag. The spectral analysis shows a good match with the La2004 orbital solution. The sedimentation duration calculated by the astronomical age models spans at least 4.31–5.94 Myr, with an average sedimentation rate of 13.47–18.57 cm/kyr. The Pinghu Formation is subdivided into 1 second‐order, 3 third‐order and 14 fourth‐order sequences within seismic, well logging and 405 kyr‐long cycles constraints. Based on available age‐control data, the Pinghu Formation is corresponding to the middle‐late Eocene. The floating astronomical timescale of XH‐3 borehole now provides a new age constraint for the Pinghu Formation. There are four shorter‐term (<2 Myr) regional sea‐level cycles in the Pinghu Formation, which are similar to the calibrated global sea‐level fluctuations. Inconsistencies between reconstructed sea‐level curve by sedimentary noise modelling and true sea level inferred from lithology and sequence reveal various sources of noise in the sedimentary record. Variations in the distribution and thickness of coal seams in the Pinghu Formation appear to be a stratigraphic response to astronomical and non‐astronomical forcing such as regional tectonicssm and facies changes. [ABSTRACT FROM AUTHOR]

The type-Silurian Cellon section in the Carnic Alps in Austria underpins much of the current Silurian conodont zonations, forming the basis for the Silurian timescale. However, the Silurian record of the Cellon section lacks radiometric and astrochronological age constraints, making it difficult to gain insights into the processes pacing Silurian (anoxic) events. To attain age constraints and investigate the pacing Silurian (anoxic) events by astronomical cycles, a cyclostratigraphic study was conducted on high-resolution pXRF (CaO, Al2O3, and Fe2O3) and induration records spanning the Ludlow and Pridoli parts of the Cellon section. Astronomical cycles ranging from precession to the 405-kyr eccentricity cycle were first recognised visually in the field and in proxy records. The visual detection of astronomical cycles served as an input for the WaverideR R package, enabling the tracking of the 405-kyr eccentricity period in each proxy's continous wavelet transform scalograms. These tracked period curves were combined with external age controls through multiple Monte Carlo simulations, generating an (absolute) age model. This age model is used to assign ages and durations and their respective uncertainties to a hiatus in the Ludfordian, conodont zones, lithological units, geochronological units and events, yielding new ages for Silurian stage boundaries (e.g., Gorstian-Ludfordian boundary at 425.92 ± 0.65 Ma, the Ludfordian-Pridoli boundary at 423.03 ± 0.53 Ma, the Silurian-Devonian boundary at 418.86 ± 1.02 Ma), and new durations for the Ludfordian at 2.89 ± 0.35 Myr and Pridoli at 4.24 ± 0.46 Myr. Furthermore, the imprint of astronomical cycles in the Cellon section itself indicates that the Linde, Klev and Silurian-Devonian boundary events all occur after a 2.4-Myr eccentricity node, indicating pacing by astronomical forcing, similar to other Devonian and Cretaceous anoxic events. The Lau event, however, does not appear to coincide with a 2.4-Myr eccentricity node. [ABSTRACT FROM AUTHOR]

The amount of radiative energy received at the Earth's surface depends on two factors: Earth–Sun distance and sunlight angle. Because of the former, high-eccentricity cycles can induce the appearance of seasons in the tropical ocean. In this paper, we use the Earth system model IPSL-CM5A2 to investigate the response of the low-latitude ocean to variations in Earth's orbit eccentricity. Sea surface temperature (SST) and primary production (PP) were simulated under six precession configurations at high eccentricity and two configurations at low eccentricity, representing extreme configurations observed over the past 1 million years. Results show that high eccentricity leads to increased seasonality in low-latitude mean SST, with an annual thermal amplitude of approximately 2.2 °C (vs. 0.5 °C at low eccentricity). Low-latitude mean PP, which already exhibits inherent seasonality under low-eccentricity conditions, sees its seasonality largely increased under high eccentricity. As a consequence, we show that on long timescales the intensity of SST seasonality exhibits only the eccentricity frequency, whereas that of PP additionally follows precession dynamics. Furthermore, the seasonal variations in both SST and PP at high eccentricities are influenced by the annual placement of the perihelion with its direct impact of radiative energy received in tropical regions. This leads to a gradual and consistent transition of seasons within the calendar. We introduce the concept of "eccentriseasons", referring to distinct annual thermal differences observed in tropical oceans under high-eccentricity conditions, which shift gradually throughout the calendar year. These findings have implications for understanding low-latitude climate phenomena such as the El Niño–Southern Oscillation (ENSO) and monsoons in the past. [ABSTRACT FROM AUTHOR]

The sedimentary cycle of Fengcheng Formation in Junggar Basin changes rapidly and is difficult to identify. The low classification accuracy of high-frequency fine-grained sedimentary cycles restricts the exploration of unconventional shale oil and gas. Full-interval coring of well Maye 1 provides a solid foundation for small-layer research. In this paper, the high-frequency sedimentary cycle of Milan kovitch in Fengcheng Formation is studied by means of spectral analysis and wavelet transform, and the shale sweet spot is identified. The long period of eccentricity of 405ka, short period of eccentricity of 100ka and long period of axis slope of 42736a can be used as semi-quantitative basis for the classification of the fourth, fifth and sixth sequences. The Fengcheng Formation can be divided into 2 quaternary sequence cycles, 9 quaternary sequence cycles and 16 quaternary sequence cycles. A long period of eccentricity of 405ka can identify large-scale lake recessional and recessional, and there is a maximum lake flooding surface in the middle of the second Fengcheng Formation, which corresponds to high abundance of organic matter and high hydrocarbon generation potential. The 100ka short period eccentricity can identify the sweet spot layer, and there are 8 sweet spots in the well Maye 1, which is consistent with the results of nuclear magnetic interpretation. The research results provide a semi-quantitative basis for the classification of high-frequency sedimentary cycles and the identification of sweet spots of Fengcheng Formation in Mahu Sag, Junggar Basin. [ABSTRACT FROM AUTHOR]

Paleoclimate data have yielded variations with periods of ~23, ~40, and ~100 ky. Thermodynamic changes resulting from orbital eccentricity, obliquity, and precession have been ascribed as the cause of the variations although processes within the oceans and atmosphere may have too short memory to explain such variations. In this work, the dynamics of Sun‐Moon gravitation (SMG) were explored for a rotating Earth and were determined to have a long memory in magma, a mostly ignored geophysical fluid with a mass ~3,400 times that of the atmosphere plus the oceans. Using the basic motion and gravitation (including obliquity) of the Sun and the Moon, we determined that SMG‐induced magma motion could produce paleoclimatic variations with multiple periods (e.g., ~23, ~40, ~80, and ~100 ky), with considerable power for Earth's heat. Such "reproducible" power could possibly maintain an energetic Earth against collapse, radioactivity, and cooling. [ABSTRACT FROM AUTHOR]

We constructed a record of percent biogenic silica (opal) accumulation at Ocean Drilling Program Site 745B located in the Indian Ocean sector of the Antarctic Zone of the Southern Ocean. The record spans the majority of the early Pleistocene (1.1–2.6 Ma). Orbital‐scale sampling affords a look at the relative importance of obliquity versus precession variability through a time interval that is characterized by obliquity pacing in early Pleistocene δ18O records. Variations in the site's magnetic susceptibility record closely resemble those in the benthic foraminiferal δ18O stack (Lisiecki & Raymo, 2005, https://doi.org/10.1029/2004pa001071) and provide orbital‐scale age control. Between 1.1 and 1.8 Ma, obliquity‐related 41 kyr spectral peaks dominate with relatively little power at precession periods (23–19 kyr) in all records. Between 1.8 and 2.6 Ma, only the δ18O and magnetic susceptibility data display a distinct 41 kyr peak, while the opal lacks spectral power at any of the orbital periodicities. The lack of more pronounced precession‐scale variations in the two proxy records is consistent with observations in foraminiferal δ18O records. A low or absent response to precession in these records appears to be due to environmental control. Lack of orbital forcing in the opal record before 1.8 Ma may reflect both a more southerly location of the polar frontal zone with respect to the site, and thus the site's position outside the region of wind‐driven upwelling, and/or upwelling waters undersaturated with respect to silica prior to the establishment of the opal belt at about 2 Ma. Key Points: Orbital‐scale variations in magnetic susceptibility resemble those in benthic foraminiferal δ18O and provide orbital‐scale age controlBiogenic silica lacks a consistent response to precession between 1.1 and 2.6 Ma; obliquity‐scale variability begins at 1.8 MaResults support that lack of more pronounced precession in early Pleistocene δ18O records may not be solely due to a muting of the signal [ABSTRACT FROM AUTHOR]

Astronomical (or Milanković) forcing of the Earth system is key to understanding rhythmic climate change on time scales ≳104 y. Paleoceanographic and paleoclimatological applications concerned with past astronomical forcing rely on astronomical calculations (solutions), which represent the backbone of cyclostratigraphy and astrochronology. Here we present state‐of‐the‐art astronomical solutions over the past 3.5 Gyr. Our goal is to provide tuning targets and templates for interpreting deep‐time cyclostratigraphic records and designing external forcing functions in climate models. Our approach yields internally consistent orbital and precession‐tilt solutions, including fundamental solar system frequencies, orbital eccentricity and inclination, lunar distance, luni‐solar precession rate, Earth's obliquity, and climatic precession. Contrary to expectations, we find that the long eccentricity cycle (LEC) (previously assumed stable and labeled "metronome," recent period ∼405 kyr), can become unstable on long time scales. Our results reveal episodes during which the LEC is very weak or absent and Earth's orbital eccentricity and climate‐forcing spectrum are unrecognizable compared to the recent past. For the ratio of eccentricity‐to‐inclination amplitude modulation (recent individual periods of ~2.4 and ~1.2 Myr, frequently observable in paleorecords) we find a wide distribution around the recent 2:1 ratio, that is, the system is not restricted to a 2:1 or 1:1 resonance state. Our computations show that Earth's obliquity was lower and its amplitude (variation around the mean) significantly reduced in the past. We therefore predict weaker climate forcing at obliquity frequencies in deep time and a trend toward reduced obliquity power with age in stratigraphic records. For deep‐time stratigraphic and modeling applications, the orbital parameters of our 3.5‐Gyr integrations are made available at 400‐year resolution. Key Points: We provide orbital eccentricity, inclination, oliquity, and climatic precession for use in paleostudies/climate models over the past 3.5 GyrThe long eccentricity cycle (previously used as "metronome") can become unstable on long time scalesEarth's past obliquity forcing/amplitude was significantly reduced. We predict reduced obliquity power with age in stratigraphic records [ABSTRACT FROM AUTHOR]

We present the glacial history of the Makarov Basin (western Arctic Ocean) during the last ∼1.1 Myr, with sediment provenances using the newly refined chronostratigraphy of core ARA03B‐41GC02. According to the principal component analysis of the bulk mineral assemblages, felsic minerals were dominant, and their ratios (K‐feldspar/plagioclase and quartz/feldspars) indicated that sediment supply to the Makarov Basin was mainly from the Siberian margin and partly from northern North America, including the Canadian Arctic. However, their occurrence did not vary significantly between interglacials and glacials due to the mixed sources. In contrast, clinopyroxene and dolomite indicated specific sediment origins from the eastern Siberian margin and northern North America, respectively. The clinopyroxene content followed an eccentricity cycle (∼100‐Kyr) during the early to middle Pleistocene, suggesting that the eustatic sea level changes may have influenced its input from the eastern Siberian margin. The dolomite, transported primarily by icebergs from the Arctic sector of the Laurentide Ice Sheet (LIS) in northern North America, has also followed the same cycle since the early Pleistocene. Thus, the mineralogical signals highlight that sediment origins and transport processes in the Makarov Basin were related to ice sheet evolution at the eccentricity cycle. In addition, dolomite deposition in the Makarov Basin began by the early Pleistocene (∼790 ka), ∼150 ka earlier than in previous North Atlantic records (∼640 ka), indicating the earlier LIS calving in the Arctic sector than in the Atlantic sector. Plain Language Summary: We investigated past mineralogic changes in the Makarov Basin (western Arctic Ocean) over the last 1.1 million years using marine sediment core ARA03B‐41GC02. Bulk mineral analysis revealed that sediments in the Makarov Basin mainly originated from the Siberian margin, with a partial contribution from northern North America. However, sediments deposited during interglacial and glacial periods were mixed from different sources. Nevertheless, specific minerals such as clinopyroxene and dolomite allow us to distinguish different sediment sources between the eastern Siberian margin and northern North America. The clinopyroxene content fluctuated on a cycle of ∼100‐Kyr during the early to middle Pleistocene, suggesting an association with global sea level changes. The variation in dolomite content followed the same cycle, indicating that sediments containing dolomite were mainly transported by icebergs from the Laurentide Ice Sheet (LIS) in northern North America. These results linked sediment sources and transport processes to glacier evolution over cycles of ∼100‐Kyr. Interestingly, our study shows that dolomite deposition in the Makarov Basin began about 790,000 years ago, which is about 150,000 years earlier than previously reported (∼640 ka) in the North Atlantic, suggesting an earlier LIS calving into in the Arctic sector than in the North Atlantic sector. Key Points: Sediment provenances of clinopyroxene and dolomite are different (eastern Siberian margin and North America) in the Makarov BasinVariations in dolomite and clinopyroxene during the Pleistocene follow a ∼100 Kyr cycle of eccentricityDolomite in Makarov Basin ∼150 Kyr earlier than N. Atlantic implies Laurentide Ice Sheet calved into Arctic before extending to N. Atlantic [ABSTRACT FROM AUTHOR]

Detailed analysis of tropical climate dynamics is lacking for the Early to Middle Miocene, even though this time interval bears important analogies for future climates. Based on high‐resolution proxy reconstructions of sea surface temperature, export productivity and dust supply at Ocean Drilling Program Site 959, we investigate astronomical forcing of the West African monsoon in the eastern equatorial Atlantic across the prelude, onset, and continuation of the Miocene Climatic Optimum (MCO; 18–15 Ma). Along with previously identified eccentricity periodicities of ∼400 and ∼100 kyr, our records show that climate varied on ∼27–17 kyr, ∼41 kyr, and ∼60–50 kyr timescales, which we attribute to precession, obliquity, and their combination tones, respectively. The relative contribution of these astronomical cycles differed between proxies and through time. Three intervals with distinct variability were recognized, which are particularly clear in the temperature record: (a) strong eccentricity, obliquity, and precession variability prior to the MCO (18.2–17.7 Ma), (b) strong influence of obliquity just after the onset of the MCO (16.9–16.3 Ma) concurring with a 2.4 Myr eccentricity minimum, and (c) dominant eccentricity and precession variability during the MCO between 16.3 and 15.0 Ma. Sedimentation at Site 959 was influenced by astronomically paced variations in upwelling intensity and North African aridity related to West African monsoon dynamics. Continuously present patterns of precession imply low‐latitude forcing, while asymmetric eccentricity and obliquity imprints and strong obliquity influence suggest that Site 959 was also affected by high‐latitude, glacial‐interglacial dynamics. Key Points: The West African monsoon drove astronomically paced variations in upwelling intensity, productivity, and dust supply between 18 and 15 Ma60–50 kyr cyclicity between 16.9 and 16.3 Ma resulted from precession‐obliquity combination tones within a 2.4 Myr eccentricity minimumAsymmetric eccentricity and obliquity cycles suggest an influence of high‐latitude, glacial‐interglacial variability [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Intensification of northern hemisphere glaciation (iNHG), ~2.7 million years ago (Ma), led to establishment of the Pleistocene to present-day bipolar icehouse state. Here we document evolution of orbital- and millennial-scale Asian winter monsoon (AWM) variability across the iNHG using a palaeomagnetically dated centennial-resolution grain size record between 3.6 and 1.9 Ma from a previously undescribed loess-palaeosol/red clay section on the central Chinese Loess Plateau. We find that the late Pliocene–early Pleistocene AWM was characterized by combined 41-kyr and ~100-kyr cycles, in response to ice volume and atmospheric CO2 forcing. Northern hemisphere ice sheet expansion, which was accompanied by an atmospheric CO2 concentration decline, substantially increased glacial AWM intensity and its orbitally oscillating amplitudes across the iNHG. Superposed on orbital variability, we find that millennial AWM intensity fluctuations persisted during both the warmer (higher-CO2) late Pliocene and colder (lower-CO2) early Pleistocene, in response to both external astronomical forcing and internal climate dynamics. Persistent millennial Asian winter monsoon variability is shown to be superposed on orbital 41-kyr and 100-kyr cycles across the Pliocene–Pleistocene glacial intensification using a paleomagnetically dated high-resolution Chinese Loess Plateau grain size record. [ABSTRACT FROM AUTHOR]

Many have tagged the Younger Dryas Impact Hypothesis (YDIH), a supposition, lacking convincing evidence in support. The core of criticism lies squarely on uniformitarianism, that is, uniform processes moving uniformly with no room for catastrophic events, specifically cosmic catastrophic forces. Beyond philosophically based aversion to the YDIH, specific criticism comes from megafauna and archaeologic corners, related to the near coeval disappearance of specific Late Pleistocene species on the one hand, and relation to disruption and temporary disappearance of the Clovis people et al. on the other. The Younger Dryas geologic paradigm, originally in place with meltwater release into the Atlantic in tow, attention slowly drifted to explanation of an innocuous looking, thin (~1–3 cm), black sediment bed found in lacustrine and fluvial deposits of the American southwest, and other intercontinental places. Thus, with thin dark beds of Gubbio in mind, the quest to explain black mat (BM) beds took on a cosmic aspect, one with growing, supporting evidence on several continents. The impossible hypothesis, now the probable explanation of the Younger Dryas climatic reversal, is at center stage, set at 12.8 ka, with a burgeoning corpus of evidence its cornerstone. [ABSTRACT FROM AUTHOR]

Theory suggests that the response time of alluvial channel long-profiles to perturbations in climate is related to the magnitude of the forcing and the length of the system. Shorter systems may record a higher frequency of forcing compared to longer systems. Empirical field evidence that system length plays a role in the climate periodicity preserved within the sedimentary record is, however, sparse. The Toro Basin in the Eastern Cordillera of NW Argentina provides an opportunity to test these theoretical relationships as this single source-to-sink system contains a range of sediment deposits, located at varying distances from the source. A suite of eight alluvial fan deposits is preserved along the western flanks of the Sierra de Pascha. Farther downstream, a flight of cut-and-fill terraces have been linked to eccentricity-driven (100-kyr) climate cycles since ca. 500 ka. We applied cosmogenic radionuclide (10Be) exposure dating to the fan surfaces to explore (1) how channel responses to external perturbations may or may not propagate downstream, and (2) the differences in landscape response to forcing frequency as a function of channel length. We identified two generations of fan surfaces: the first (G1) records surface activity and abandonment between ca. 800 and 500 ka and the second (G2) within the last 100 kyr. G1 fans record a prolonged phase of net incision, which has been recognised throughout the Central Andes, and was likely triggered by enhanced 100-kyr global glacial cycles following the Mid-Pleistocene Transition. Relative fan surface stability followed, while 100-kyr cut-and-fill cycles occurred downstream, suggesting a disconnect in behaviour between the two channel reaches. G2 fans record higher frequency climate forcing, possibly the result of precessional forcing of climate (ca. 21/40-kyr timescales). The lack of a high-frequency signal farther downstream provides field support for theoretical predictions of a filtering of high-frequency climate forcing with increasing channel length. We show that multiple climate periodicities can be preserved within the sedimentary record of a single basin. Differences in the timing of alluvial fan and fluvial terrace development in the Toro Basin appears to be associated with how channel length affects fluvial response times to climate forcing as well as local controls on net incision, such as tectonic deformation. [ABSTRACT FROM AUTHOR]

The Messinian-Zanclean boundary in the Mediterranean basin marks the end of the Messinian salinity crisis (MSC) at approximately 5.33 Ma. The mechanism behind the return to normal marine conditions after the MSC are debated, with two main hypotheses proposed: an instantaneous reflooding of the Mediterranean at the base of the Zanclean, following its near-complete desiccation, or a gradual sea level rise in a non-desiccated basin during the late MSC phase (Lago-Mare). Our objectives are to refine the age model of the Pollenzo section in the Piedmont basin, Italy, and to elucidate environmental variability during this phase. We employ high-resolution biomagnetostratigraphic and cyclostratigraphic analyses, integrated with statistical multivariate and cluster analyses, and tie the results with other Italian Mediterranean reference sections of the basal Zanclean. The proposed age model is based on biostratigraphic markers (planktic foraminifera and calcareous nannofossils), alongside the identification of the base of the Thvera subchron. Although no astrochronological tuning was proposed, the influence of orbital parameters variation on calcareous plankton was noted, especially at tie of eccentricity maxima. Our results indicate a gradual restoration of open marine conditions after the MSC, spanning from 5.33 to 5.23 Ma. We observe a transition from a more marginal environment to more open marine conditions at the termination of MSC. Our findings challenge the notion of an abrupt transition at the end of the MSC, emphasizing the gradual nature of environmental change in the northernmost Mediterranean basin, from the late Messinian to the early Zanclean.

The article provides an overview of the book "Introducing Old Testament Theology" by W.H. Bellinger, Jr. The book explores different themes in the Old Testament, such as creation, history, the Psalms, wisdom literature, and prophecy. However, the book is criticized for being difficult to read and for the author's unclear views on creation and Genesis. Bellinger's interpretation of the Pentateuch and the creation account is also questioned, particularly his denial of physical death in Genesis 2-3, which could be seen as supporting evolutionary views. The article argues against Bellinger's approach to Old Testament theology, specifically his emphasis on the Psalms instead of Genesis, and refutes his claims about the existence of two creation accounts and the interpretation of Genesis 1. It concludes that the book lacks value and compromises the Old Testament by rejecting a literal interpretation of Genesis. [Extracted from the article]

The Late Pliocene marks the intensification of Northern Hemisphere Glaciation, offering a unique opportunity to study climate evolution and ice-sheet related feedback mechanisms. In this study, we present high-resolution Mg/Ca-based sea surface (SST) and subsurface temperatures (SubT) derived from foraminiferal species Globigerinoides ruber and Globorotalia hirsuta , respectively, at the Integrated Ocean Drilling Project (IODP) Expedition 306 Site U1313 in the mid-latitudinal North Atlantic during the early Late Pliocene, 3.65 – 3.37 million years ago (Ma). We find distinct differences between our new G. ruber Mg/Ca-based SST record and previously published alkenone-based SST record from the same location. These discrepancies in both absolute values and variations highlight distinct seasonal influences. The G. ruber Mg/Ca-based SST data, reflecting summer temperatures, were primarily influenced by local summer insolation, showing a dominant precession cycle. Conversely, the variations in alkenone-based SST are found to be more indicative of cold season changes, despite previous interpretations of these records as reflecting annual mean temperatures. A simultaneous decline in Mg/Ca-based SST and SubT records from 3.65 to 3.5 Ma suggests a diminished poleward oceanic heat transport, implying a weakening of the North Atlantic Current. A comparison with early Pleistocene G. ruber Mg/Ca-based SST records shows a shift in the dominant climatic cycle from precession to obliquity, alongside a marked increase in amplitude, indicating an enhanced influence of obliquity cycles correlated with the expansion of Northern Hemisphere ice sheets. [ABSTRACT FROM AUTHOR]

Extraterrestrial chrome spinel and chromite extracted from the sedimentary rock record are relicts from coarse micrometeorites and rarely meteorites. They are studied to reconstruct the paleoflux of meteorites to the Earth and the collisional history of the asteroid belt. Minor element concentrations of Ti and V, and oxygen isotopic compositions of these relict minerals were used to classify the meteorite type they stem from, and thus to determine the relative meteorite group abundances through time. While coarse sediment‐dispersed extraterrestrial chrome‐spinel (SEC) grains from ordinary chondrites dominate through the studied time windows in the Phanerozoic, there are exceptions: We have shown that ~467 Ma ago, 1 Ma before the breakup of the L chondrite parent body (LCPB), more than half of the largest (>63 μm diameter) grains were achondritic and originated from differentiated asteroids in contrast to ordinary chondrites which dominated the meteorite flux throughout most of the past 500 Ma. Here, we present a new data set of oxygen isotopic compositions and elemental compositions of 136 grains of a smaller size fraction (32–63 μm) in ~467 Ma old pre‐LCPB limestone from the Lynna River section in western Russia, that was previously studied by elemental analysis. Our study constitutes the most comprehensive oxygen isotopic data set of sediment‐dispersed extraterrestrial chrome spinel to date. We also introduce a Raman spectroscopy‐based method to identify SEC grains and distinguish them from terrestrial chrome spinel with ~97% reliability. We calibrated the Raman method with the established approach using titanium and vanadium concentrations and oxygen isotopic compositions. We find that ordinary chondrites are approximately three times more abundant in the 32–63 μm fraction than achondrites. While abundances of achondrites compared to ordinary chondrites are lower in the 32–63 μm size fraction than in the >63 μm one, achondrites are approximately three times more abundant in the 32–62 μm fraction than they are in the present flux. We find that the sources of SEC grains vary for different grain sizes, mainly as a result of parent body thermal metamorphism. We conclude that the meteorite flux composition ~467 Ma ago ~1 Ma before the breakup of the LCPB was fundamentally different from today and from other time windows studied in the Phanerozoic, but that in contrast to the large size fraction ordinary chondrites dominated the flux in the small size fraction. The high abundance of ordinary chondrites in the studied samples is consistent with the findings based on coarse extraterrestrial chrome‐spinel from other time windows. [ABSTRACT FROM AUTHOR]

In this paper, we report on a biostratigraphic, magnetostratigraphic, and stable isotope (δ13C and 3He) analysis across three pelagic limestone sections of the Campanian Scaglia Rossa Formation exposed in the classic Bottaccione Gorge at Gubbio (Umbria region), near the village of Furlo, and near the town of Apiro (both in the Marche region), all located in the Umbria-Marche basin of the northeastern Apennines of central Italy. These sections record the coincidental occurrence of an extraterrestrial 3He (3HeET) anomaly known as K1 and a negative shift in the δ13C record known as the early Campanian event. Cyclostratigraphic spectral analysis of the Furlo section based on a highresolution magnetic susceptibility record in these pelagic limestones revealed that the regular orbitally forced Milankovitch cycles are somewhat disturbed or blurred through the interval of the coincident 3HeET K1 anomaly and the early Campanian event isotopic anomaly, suggesting a causal effect resulting from the enhanced influx of extraterrestrial material (i.e., interplanetary dust particles and a myriad of small meteorite impacts). This would have altered the transparency of the atmosphere, causing a short-lived climate change event. [ABSTRACT FROM AUTHOR]

Previous studies of rapid geomagnetic changes have highlighted the most extreme changes in direction and field strength found in paleomagnetic field models over the past 100 ky. Here we study distributions of rates of change in both time and space. Field models based on direct observations provide the most accurate values for rates of change, but their short duration precludes a complete description of field behavior. Broader representation is provided by time‐varying paleofield models, here including GGF100k, GGFSS70, LSMOD.2, CALS10k.2, HFM.OL1.A1, pfm9k.2, and SHAWQ‐iron age although variability across models and lack of temporal and spatial resolution of fine scale variations make direct comparisons difficult. For the paleofield we define rapid changes as exceeding the peak overall value of 0.4° yr−1 for directional changes and 150 nT yr−1 for intensities as established by the gufm1 model spanning 1590–1990 CE. We find that rapid directional changes are associated with low field strength and can spread across all latitudes during such episodes. Distributions of directional rates of change exhibit high skewness for models that include excursions. Rates of change in field intensity exceeding 150 nT yr−1 arise in brief intervals during the Holocene particularly associated with the strong field Levantine Iron Age Anomaly. Around the Laschamp excursion there are also rare localized occurrences of rapid intensity change. Limitations in current models make it difficult to define absolute rates for past changes, but we see that rapid changes are essential field characteristics not observed in the modern field that should nevertheless be regarded as an essential for Earth‐like dynamo simulations. Plain Language Summary: Earth's magnetic field is generated by fluid motions in its liquid outer core lying deep below the surface. Changes in the modern field are well‐mapped using low earth orbiting satellites and ground observations, but these are very modest. The largest changes over the past hundred thousand years occur on geological time scales predating the era of direct observations. These include geomagnetic excursions, periods characterized by low field strength and unstable directions, and intensity spikes when the field is unusually strong. To study the rates at which field changes occur we use a range of global time‐varying magnetic field models constructed from paleomagnetic and archeomagnetic records. These are much less detailed than modern data, but after accounting for their lesser resolution can still provide key insights into the occurrence of the most rapid changes. We find that high rates of change are an essential characteristic of the geomagnetic field over 0–100 ka that should be reproducible in Earth‐like dynamo simulations. Anomalously large rates of directional change are associated with weak field intensities surrounding geomagnetic excursions. Rapid intensity changes occur in brief intervals associated with the strongest fields found during the past few thousand years. Key Points: Rapid changes are an essential characteristic of the geomagnetic field over 0–100 kaAnomalously large rates of directional change are associated with weak field intensityRapid intensity changes occur in brief intervals associated with strong fields [ABSTRACT FROM AUTHOR]

Astronomical cycles recorded in stratigraphic sequences offer a powerful data source to estimate Earth's axial precession frequency k, as well as the frequency of rotation of the planetary perihelia (gi) and of the ascending nodes of their orbital planes (si). Together, these frequencies control the insolation cycles (eccentricity, obliquity and climatic precession) that affect climate and sedimentation, providing a geologic record of ancient Solar system behavior spanning billions of years. Here, we introduce two Bayesian methods that harness stratigraphic data to quantitatively estimate ancient astronomical frequencies and their uncertainties. The first method (TimeOptB) calculates the posterior probability density function (PDF) of the axial precession frequency k and of the sedimentation rate u for a given cyclostratigraphic data set, while setting the Solar system frequencies gi and si to fixed values. The second method (TimeOptBMCMC) applies an adaptive Markov chain Monte Carlo algorithm to efficiently sample the posterior PDF of all the parameters that affect astronomical cycles recorded in stratigraphy: five gi, five si, k, and u. We also include an approach to assess the significance of detecting astronomical cycles in cyclostratigraphic records. The methods provide an extension of current approaches that is computationally efficient and well suited to recover the history of astronomical cycles, Earth‐Moon history, and the evolution of the Solar system from geological records. As case studies, data from the Xiamaling Formation (N. China, 1.4 Ga) and ODP Site 1262 (S. Atlantic, 55 Ma) are evaluated, providing updated estimates of astronomical frequencies, Earth‐Moon history, and secular resonance terms. Plain Language Summary: Earth's transit through our Solar system is ever evolving, and so are such seemingly unwavering planetary characteristics as the number of hours in a day. For example, it is well known that the length of the day generally increases with time as Earth's rotation rate decreases from tidal interactions with our orbiting Moon. But the ability to chart out this evolution over the history of the Solar system has been hampered by limitations of both data and theoretical models. This study presents a computational approach to map out the history of Solar system motions and the history of the Earth‐Moon system, including the length of a day, by leveraging geological data and astronomical theory within a statistical framework that fully accounts for uncertainties. As such, the approach provides a means to use the geological archive as an astronomical observatory, allowing us to explore Solar system and Earth‐Moon dynamics throughout their long history. Key Points: We present two updated methods for Bayesian astrochronology: TimeOptB and TimeOptBMCMCTimeOptB simultaneously estimates the Earth's axial precession frequency and the sedimentation rate from cyclostratigraphic dataIn addition, TimeOptBMCMC simultaneously estimates Solar system g‐frequencies and s‐frequencies from cyclostratigraphic data [ABSTRACT FROM AUTHOR]

Variations in solar insolation caused by changes in the Earth's orbit—specifically its eccentricity, obliquity, and precession—can leave discernible marks on the geologic record. Astrochronology leverages these markers to establish a direct connection between chronological measurements and different facets of climate change as recorded in marine sediments. This approach offers a unique window into the Earth's climate system and the construction of high-resolution, continuous time scales. Our study involves comprehensive bulk carbonate analyses of 390 discrete samples from core SCS1, which was retrieved from the deep-sea floor of the northern South China Sea. By utilizing carbonate stratigraphic data, we have developed a carbonate stratigraphic age model. This was achieved by aligning the carbonate sequence from core SCS1 with the established carbonate standard stratigraphic time scale of the South China Sea. Subsequently, we construct an astronomically tuned time scale based on this age model. Our findings indicate that sediment records in this core have been predominantly influenced by a 20,000-year cycle (precession cycle) throughout the Late Pleistocene. We have developed an astronomical time scale extending back approximately 110,000 years from the present, with a resolution of 280 years, by tuning the carbonate record to the precession curve. Time-domain spectral analysis of the tuned carbonate time series, alongside the consistent comparability of the early Holocene low-carbonate event (11–8 kyr), underscores the reliability of our astronomical time scale. Our age model exposes intricate variations in carbonate deposition, epitomizing a typical "Pacific-type" carbonate cycle. Previous research has illustrated that precession forcing predominantly influences productivity changes in the South China Sea. The pronounced precession-related cycle observed in our record suggests that changes in productivity significantly impact carbonate content in the area under study. Furthermore, the clear precession period identified in the carbonate record of core SCS1 reflects the response of low-latitude processes to orbital parameters, implying that carbonate deposition and preservation in core SCS1 are chiefly influenced by the interplay between the Intertropical Convergence Zone (ITCZ) and the monsoon system within the precession band. Our astronomical time scale is poised to enhance paleoceanographic, paleoclimatic, and correlation studies further. Additionally, the independent evidence we provide for using proxy records for astronomical age calibration of marine sediments lends additional support to similar methods of astronomical tuning. [ABSTRACT FROM AUTHOR]

Astronomical cycles are strongly expressed in marine geological records, providing important insights into Earth system dynamics and an invaluable means of constructing age models. However, how various astronomical periods are filtered by the Earth system and the mechanisms by which carbon reservoirs and climate components respond, particularly in absence of dynamic ice sheets, is unclear. Using an Earth system model that includes feedbacks between climate, ocean circulation, and inorganic (carbonate) carbon cycling relevant to geological timescales, we systematically explore the impact of astronomically‐modulated insolation forcing and its expression in model variables most comparable to key paleoceanographic proxies (temperature, the δ13C of inorganic carbon, and sedimentary carbonate content). Temperature predominately responds to obliquity and is little influenced by the modeled carbon cycle feedbacks. In contrast, the cycling of nutrients and carbon in the ocean generates significant precession power in atmospheric CO2, benthic ocean δ13C, and sedimentary wt% CaCO3, while inclusion of marine sedimentary and weathering processes shifts power to the long eccentricity period. Our simulations produce reduced pCO2 and dissolved inorganic carbon δ13C at long eccentricity maxima and, contrary to early Cenozoic marine records, CaCO3 preservation in the model is enhanced during eccentricity modulated warmth. Additionally, the magnitude of δ13C variability simulated in our model underestimates marine proxy records. These model‐data discrepancies hint at the possibility that the Paleogene silicate weathering feedback was weaker than modeled here and that additional organic carbon cycle feedbacks are necessary to explain the full response of the Earth system to astronomical forcing. Plain Language Summary: The Earth's tilt and orbit around the Sun change periodically, influencing the amount and distribution of solar energy that reaches the surface over time. We use a numerical model to simulate how changes in solar radiation impact the surface climate, ocean circulation, and the carbon cycle. Our model output shows that global mean surface temperatures are mainly controlled by obliquity (a measure for how tilted the Earth is), changing every 40,000 years. Changes in the carbon cycle are mainly controlled by precession (a measure for the direction in which the Earth is tilted relative to the Sun), changing approximately every 20,000 years. However, precession cycles are not well preserved in geological records because, (a) the large total mass of carbon in the atmosphere and ocean means that small fluxes over 20,000 years are insufficient to cause drastic changes, and (b) mixing of marine sediments distorts the signal. We also find that modeled variations in the climate‐carbon cycle are smaller than those observed in geological records. This suggests that other processes not modeled here, such as burial and release of organic carbon, are important to explain the full astronomical climate‐carbon cycle variability. Key Points: Time‐varying astronomical forcing simulated on a multi‐million‐year timescale using an Earth system model of intermediate complexityStrong 100 kyr power present in temperature and wt% CaCO3 is absent from δ13C cycles in the inorganic carbon reservoirAdditional organic carbon feedbacks and a reduced weathering feedback likely played a role in early Cenozoic climate‐carbon cycle dynamics [ABSTRACT FROM AUTHOR]

Understanding orbital-scale changes in East Asian summer monsoon (EASM) precipitation is a fundamental issue in paleoclimate research for assessing the response of the East Asian monsoon to different climate forcings, such as insolation, ice volume, and greenhouse gases. However, owing to the inconsistencies between different proxies, the fundamental driving force for EASM variability remains controversial. In the present study, the global climate under the given insolation changes over the past 450 kyr was calculated using a climate model, Meteorological Research Institute Coupled General Circulation Model version 2.3 (MRI–CGCM2.3). The calculated change in summer precipitation is dominated by a 20-kyr precession cycle over China, highly consistent with cave δ18O records in southeast China. The proxy data from northern China (Chinese Loess Plateau) and Japan (Lake Biwa) cannot be fully explained by the calculation results, implying the importance of other forcing such as ice-sheet volume. A strong positive correlation was observed between insolation and precipitation over the coastal area of China and a negative correlation between insolation and precipitation around Japan. The results imply that the EASM is affected by the insolation intensity; however, the effect can vary between regions. The positive correlation between boreal summer insolation and precipitation over China results from the atmosphere-ocean interaction over the Indian Ocean and the western Pacific. Under intense insolation, the northern shift of the monsoon front associated with the intensification of the North Pacific subtropical high causes an increase in rainfall in the coastal area of China. The intensification of the subtropical high is caused by the integration of local wind–evaporation–sea surface temperature (WES) feedback with the Kelvin wave response to the warm Indian Ocean (IPOC mode). In contrast, the EASM intensity around Japan was affected by the strength of the North Pacific High. Under strong insolation, the North Pacific High intensified, causing a decrease in summer precipitation around Japan. [ABSTRACT FROM AUTHOR]

The cycle of precipitation change is key to understanding the driving mechanism of the East Asian summer monsoon (EASM). However, the dominant cycles of EASM precipitation revealed by different proxy indicators are inconsistent, leading to the "Chinese 100 kyr problem". In this study, we examine a high-resolution, approximately 350,000-year record from a low-latitude loess profile in China. Our analyses show that variations in the ratio of dithionite−citrate−bicarbonate extractable iron to total iron are dominated by the ~20-kyr cycle, reflecting changes in precipitation. In contrast, magnetic susceptibility varies with the ~100-kyr cycle and may be mainly controlled by temperature-induced redox processes or precipitation-induced signal smoothing. Our results suggest that changes in the EASM, as indicated by precipitation in this region, are mainly forced by precession-dominated insolation variations, and that precipitation and temperature may have varied with different cycles over the past ~350,000 years. Earth's orbit has tuned the variations of the East Asian summer monsoon. Here, a low latitude loess palaeoclimate record provides evidence that variation in monsoon rainfall is dominated by the precession cycle. [ABSTRACT FROM AUTHOR]

The Late Albian- Early Turonian Formation is the second-largest carbonate reservoir in the South and Southwest of Iran hosting significant accumulations of hydrocarbons deposited on the edge of the Neotethys. The purpose of this study is to analyze the sequence stratigraphy and Milankovitch cycles of the Sarvak Formation in three wells of the Anaran exploration block by using the Maximum Entropy Spectral Analysis (MESA) of gamma ray logs and integration with core studies to achieve a comprehensive understanding of the formation. The study of 353 microscopic samples led to the identification of 8 microfacies including (a) mudstone to oligostigenid wackestone with benthic and pelagic foraminifera, (b) packstone-rudstone, (c) rudistic with benthic foraminifers, (d) bioclast intraclast, (e) grainstone with benthic foraminifers, (f) peloid Wackestone to peloid wackestone with low benthic foraminifera diversity, (g) Peloid packstone with diverse benthic Foraminifers and (h) Bioclast Wackestone, which are distributed in three facies belts ranging from lagoon to shoal and open marine settings. In addition to four third-order sedimentary sequences were also identified based on facies changes combined with the Prediction Error Filter Analysis (PEFA), Integrated Prediction Error Filter Analysis (INPEFA) diagrams. Examining the Milankovitch cycles based on the analysis of the distances between gamma peaks and MESA revealed 100 thousand year cycles. Orbital dating according to the counting of the Milankovitch cycles indicates the equivalent age of 11 to 12 million years for the Sarvak Formation. [ABSTRACT FROM AUTHOR]

Repeated carbon isotope excursions and widespread organic-rich shale deposition mark the Middle and Upper Devonian series. Various explanations such as extensive volcanism and land plant evolution have been given for these perturbations and the general sensitivity of the Devonian oceans to the development of anoxia, but their repeated nature suggests that astronomical forcing may have controlled their timing. Here, a cyclostratigraphic study of the Kellwasser Crisis at the Frasnian–Famennian stage boundary (ca. 372 Ma) is carried out. The Kellwasser Crisis was one of the most ecologically impactful of the Devonian perturbations and is ranked among the "Big Five" Phanerozoic mass extinctions. The studied site is the Winsenberg roadcut section in the Rhenish Massif, Germany, which represents a quiet tropical shelf basin setting. Centimetre-scale elemental records, generated by portable X-ray scanning, allow for testing of the hypothesis that a 2.4 Myr eccentricity node preceded the Upper Kellwasser event. The study's results are supportive of this hypothesis. We find enhanced chemical weathering (K 2 O / Al 2 O 3) during the period leading up to the Upper Kellwasser and a peak in distal detrital input (SiO 2 / CaO) and riverine runoff (TiO 2 / Al 2 O 3) just prior to the start of the Upper Kellwasser event. We interpret this pattern as the long-term eccentricity minimum facilitating excessive regolith build-up in the absence of strong seasonal contrasts. The Earth's system coming out of this node would have rapidly intensified the hydrological cycle, causing these nutrient-rich regoliths to be eroded and washed away to the oceans, where they resulted in eutrophication and anoxia. An astronomical control on regional climate is observed beyond this single crisis. Wet–dry cycles were paced by 405 kyr eccentricity, with both the Lower and Upper Kellwasser events taking place during comparatively drier times. A precession-sensitive monsoonal climate system prevailed on shorter timescales. Intensification of this monsoonal system following the node may have caused the widespread regolith erosion. We estimate the total duration of the Kellwasser Crisis at ca. 900 kyr, with the individual events lasting for ca. 250 and 100 kyr, respectively. If astronomical control indeed operated via regolith development in monsoonal climates, then land plants may have played an important role. This would not have been through evolutionary steps directly triggering Kellwasser perturbations but by gradually strengthening the climatic response to orbital forcing via soil development – creating soils thick enough to meaningfully respond to orbital forcing – and intensifying the hydrological cycle. [ABSTRACT FROM AUTHOR]

In areas of low uplift rate on the Pacific Coast of North America, reoccupation of emergent marine terraces by later high sea‐stands has been hypothesised to explain the existence of thermally anomalous fauna (mixtures of warm and cool species) of last interglacial age. If uplift rates have been low for much of the Quaternary, it follows that higher (older) terraces should also show evidence of reoccupation. Strontium isotope analyses of fossils from a high‐elevation marine terrace on Anacapa Island, California, yield ages ranging from ~2.4–2.3 Ma to ~1.4–1.5 Ma. These results indicate that terrace reoccupation and fossil mixing on Anacapa Island could have taken place over several interglacial periods in the early Pleistocene. Terrace reoccupation over this time period is likely a function of both a low uplift rate and the timing of orbital forcing of glacial–interglacial cycles. Climate change in the early Pleistocene was modulated by the 41 ka obliquity cycle, and glacial–interglacial cycles were much shorter than later in the Pleistocene. Nearby San Miguel Island also has evidence of terrace reoccupation, with Sr isotope ages of shells from several high‐elevation terraces ranging from ~1.21–1.25 Ma to ~0.43–0.50 Ma. However, the frequency of terrace reoccupation was lower than on Anacapa Island. The uplift rate of San Miguel Island is higher than that of Anacapa Island and terraces formed when glacial–interglacial cycles were longer. The frequency of marine terrace reoccupation is controlled by the rate of tectonic uplift and the timing of orbital forcing of sea level change during glacial–interglacial cycles. [ABSTRACT FROM AUTHOR]

The Early Eocene Climatic Optimum (EECO) may be a potentially useful analog for future global warming under high CO2 concentrations. However, a paucity of orbital‐scale terrestrial records limits our understanding of how the hydrological cycle responded during this protracted (∼4 Myr) interval of global warmth. In this study, we combine zircon U‐Pb dating and cyclostratigraphy to establish a high‐resolution astronomical timescale spanning the EECO (∼52.9 Ma to ∼49.9 Ma) through a >1 km fluviolacustrine succession from the Gonjo Basin, Southeast Tibet. Our results suggest that hydroclimate variability in the region during this interval was strongly controlled by eccentricity forcing (∼405 Kyr, ∼135–100 Kyr, and possibly ∼200 Kyr cycles). The dominance of eccentricity forcing in our record is consistent with coeval marine records, and indicates that modulation of low‐latitude summer insolation through nonlinear interactions with the global carbon cycle likely controlled hydroclimate and paleolake level in the Gonjo basin during the EECO. Our study offers new perspectives for the forcing mechanisms of terrestrial hydroclimate changes of East Asia in response to subtle changes in insolation during the EECO. Plain Language Summary: High resolution and relatively long‐duration terrestrial paleoenvironmental records across an interval of extreme warmth ∼50 million years ago (called the EECO) are rare, limiting our understanding of how the hydrological cycle operated during this time interval. In this study, we present high‐resolution geochemical data through a succession of continental sedimentary rocks from the Gonjo Basin (Southeast Tibet) spanning the EECO. Our data suggest that EECO hydroclimate was dominated by climate forcing controlled by variations in Earth's eccentricity, emphasizing the importance of eccentricity modulation of low‐latitude summer insolation through nonlinear interactions with the global carbon cycle. This finding is consistent with coeval marine records. Our study provides new insights into the forcing mechanisms of terrestrial paleoclimate change in East Asia under warm climate conditions and high CO2. Key Points: Astronomical timescale spanning the Early Eocene Climatic Optimum (EECO) established in East Asia terrestrial recordRelatively wetter and warmer climate during ∼52.9–52.39 Ma and ∼50.34–49.9 MaEccentricity forcing of EECO terrestrial climate, consistent with coeval marine records [ABSTRACT FROM AUTHOR]

Lake-level changes can significantly affect paleoenvironmental evolution, resource occurrence, terrestrial carbon budget, and biodiversity in continental basins. Climate is one of the most critical factors controlling lake-level changes. Paleoclimate of the Early Jurassic has been evidenced by oscillating icehouses to (super) greenhouses with interrupted intermittent extreme climatic events (hyperthermal and cooling), e.g., the Toarcian oceanic anoxic event (~183 Ma) and the late Pliensbachian cooling event (~185 Ma). Lake-level evolution and hydrologic cycling on Earth's surface during the Early Jurassic icehouses-to-(super)greenhouses are thus far poorly understood due to a lack of continuous high-resolution nonmarine evidence. Here we present a super-long nonmarine lake level record for this pivotal interval from the early Pliensbachian to Toarcian by sedimentary noise modeling, and construct a 16.7-Myr-long astronomical time scale (174.2 Ma to 190.9 Ma) based on cyclostratigraphy analysis of rock color datasets (CIE b*) of the Qaidam Basin. Our results document lake-level oscillations on a 5-to 10-million-year (Myr) scale which shows a pronounced correlation with long-term climate variation and extreme climatic events, and 1- to 2.5-Myr-scale lake-level changes that are prominently paced by the 2.4-Myr long-eccentricity forcing and the 1.2-Myr obliquity forcing. At the Pliensbachian Stage, the 1.2-Myr-scale lake-level changes are in phase with the coeval sea-level variations. Orbitally forced growth and decay of the ephemeral or permanent ice sheets in polar regions are interpreted to control the synchronous ups-and-downs of continental lake level and global sea level. However, during the Toarcian ice-free greenhouses to (super)greenhouses, the 1.2-Myr-scale lake-level variations show an anti-phase relationship with global sea level, indicating a 'seesaw' interaction between continental reservoirs (lakes and groundwater) and global oceans. The 2.4-Myr long-eccentricity cycles mainly regulate variations of lake level and sea level by controlling the growth and decay of small-scale continental ice sheets, which is especially notable during the Pliensbachian Stage. These findings indicate a remarkable transition of hydrological cycling pattern during the Pliensbachian-Toarcian icehouses to (super)greenhouses, which provides new perspectives and evidence for investigating the hypothesis of global sea-level changes (e.g., glacio-eustasy and aquifer-eustasy) and long-period astronomical forcing in nonmarine stratigraphy. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]