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ABSTRACT A precisely constrained and high‐resolution geochronology will enhance our understanding of sedimentary evolution, tectonic influences and climatic variations, all of which contribute to hydrocarbon exploration. According to sedimentary analysis, the North China Craton is believed to have undergone a transition in its sedimentary environment from a marine to a terrestrial lacustrine–fluvial system during the Late Palaeozoic. However, the geochronology and driving forces associated with transgression and regression remain understudied. In this study, we employed a cyclostratigraphic method to analyse the gamma‐ray logging data from a Late Palaeozoic sequence in the Y69 well in the eastern Ordos Basin. We established an astronomical time‐scale for this sequence, spanning approximately 10.83 million years, from ~299.94 ± 0.32 Ma to ~289.11 ± 0.32 Ma, in order to provide a geochronological framework for the evolution of the Ordos Basin. Subsequently, we reconstructed paleolake‐level variations by applying sedimentary noise modelling to the tuned gamma‐ray series and conducted periodicity analysis to identify astronomical signals. Our results indicate that water‐level fluctuations in the eastern Ordos Basin were modulated by ~1.2‐Myr obliquity and ~ 2.4‐Myr eccentricity cycles, suggesting long‐term astronomical forcing on hydrological circulation. The in‐phase correlation between the reconstructed water level and global sea level at ~1.2‐Myr intervals suggests that sedimentation was controlled by oceanic systems through transgression/regression events before ~294 Ma. Conversely, the anti‐phase correlation between the reconstructed water level and global sea level at the same interval indicates that sedimentation was influenced by terrestrial systems through aquifer depletion and recharge after ~294 Ma. This shift in the correlation between water levels and global sea levels reflects the transition from an oceanic to a terrestrial sedimentary environment. These findings provide a high‐resolution geochronological framework for further investigations and offer new insights into hydrological circulation, improving our understanding of the driving mechanisms behind sedimentary evolution in the North China Craton during the Late Palaeozoic Ice Age. [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]

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]

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]

[Display omitted] • A humidification of East China at ∼41.9 Ma. • Obliquity- to eccentricity-dominated transition at ∼41.9 Ma in East Asia. • Intensification of East Asian monsoons responded to the concurrent global warming. Middle Eocene saw several global warming events. However, the terrestrial climate linkage to the warming events is still enigmatic. Particularly, the paleoclimate of middle Eocene East Asia is unclear when the East Asian monsoons started to prevail. Here, we present a combination of high-resolution elemental, compositional and natural gamma-ray (GR) records and conduct an orbital-scale paleoclimate reconstruction for the middle Eocene lacustrine shale dated from 43.4 to 40.9 Ma in the Bohai Bay Basin, East Asia. The results show an obvious shift in orbital variability from obliquity- to eccentricity-dominated cycles and an evident humidification at ∼41.9 Ma in the East Asia. Eccentricity maxima filtered from the terrestrial records coincide with the deep-sea temperature rises during ∼41.9–41.5 Ma. The terrestrial climate transition at 41.9 Ma was most likely attributed to intensification of the East Asian monsoons responding to the elevated atmospheric p CO 2 during the concurrent global warming. [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 short and long eccentricity 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 (DIC) 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.

The genesis of the sedimentary dolomite has been an unexplained mystery for more than two centuries, known as the 'dolomite problem'. There may be some coupling relationship between the Phanerozoic variations in dolomite abundance and major geological events (i.e., mass extinction, oceanic anoxia, global warming, and ocean acidification); but its cause is still not adequately understood, which impedes our understanding of global geochemical cycles and long-term climate change. Understanding the controlling factors of dolomitization variations during global warming periods is the key to resolving this issue. Multiple factors controlling the dolomitization of the Middle Eocene Bohai Bay Basin, Holocene Lake Van, and Permian-Triassic dolomitization event were (re)evaluated in this study using astronomical tuning, correlation coefficient analysis, and multiple regression analysis. We demonstrate that dolomitization is more intense during global warming periods, and that its variation is more affected by temperature and pH cycling resulting from astronomical forcing. These phenomena may be caused by the Cannikin Law or the strengthening of temperature and pH cycling during global warming periods. The elevated atmospheric pCO2 and associated ocean acidification strengthen the temperature and pH cycling, thereby promoting the dolomitization of metastable carbonates by a non-equilibrium cyclic growth and replacement mechanism. This process is an important overlooked reason for the higher dolomite abundance during global warming. This study offers a novel perspective on the ‘dolomite problem’, ocean acidification and their relationship.

Laminated shales are widely developed in the Dongying Sag and have attracted much attention as an oil reservoir. Macroscopically, these shales generally have multi-scale cyclicity, which is closely related to the development of laminae. Therefore, analyzing the origin of their cyclicity is helpful to understanding the formation mechanism of laminated shales and the vertical heterogeneity of shale reservoirs, which are of great significance for continental shale oil exploration and development. In this study, a gamma ray (GR) logging series, high-resolution elemental geochemical data, high-resolution core scanning photos and grayscale data, and mineralogical data were used to characterize the cyclicity of shale at different scales, and their relationship with different astronomical cycles was discussed. The results show that the Es3L and Es4U shale in the Dongying Sag has cyclicity from the meter-scale to the ten-meter scale and then to the hundred-meter scale, which is mainly manifested by periodic changes in organic matter abundance, mineral composition, element abundance, and grayscale. These cycles of different scales coincide with different astronomical periods. Specifically, the hundred-meter scale cyclicity is mainly controlled by the very long orbital period; the ten-meter scale cyclicity is mainly related to the eccentricity cycle; while the precession period is the main driver of the meter-scale cyclicity. Finally, we propose a simplified model for illustrating the formation of rhythmic organic-rich shale. This study is helpful to understanding the origin of continental organic-rich shale and predicting shale reservoir properties. [ABSTRACT FROM AUTHOR]

“'Orbital, the Box”' provides an interactive tool with graphical user interface (GUI) for stimulating active, visual learning for understanding of astronomical climate forcing. This cross-platform tool can be run locally on a personal computer using a standard web browser environment with no need for plugins, thus maximising accessibility for students and teachers alike. The tool facilitates in the development of a holistic and quantitative understanding of astronomical climate forcing by allowing students to independently vary orbital parameters, after which they can instantaneously see the resulting effect upon the seasonal and latitudinal distribution of solar irradiance arriving at the top of the Earth’s atmosphere. Such an approach follows a classic controlled experimental design whereby one parameter can be changed while all others are kept constant. This experimental tool can be deployed as a virtual laboratory, including within a flipped classroom setting, to promote active learning of traditionally challenging concepts such as the roles of eccentricity and precession in astronomical climate forcing, and in particular their interaction with Kepler’s second law and the subsequent consequences for season length.

"Orbital, the Box" provides an interactive tool with graphical user interface (GUI) for stimulating active, visual learning for understanding of astronomical climate forcing. This cross-platform tool can be run locally on a personal computer using a standard web browser environment with no need for plugins, thus maximising accessibility for students and teachers alike. The tool facilitates in the development of a holistic and quantitative understanding of astronomical climate forcing by allowing students to independently vary orbital parameters, after which they can instantaneously see the resulting effect upon the seasonal and latitudinal distribution of solar irradiance arriving at the top of the Earth's atmosphere. Such an approach follows a classic controlled experimental design whereby one parameter can be changed while all others are kept constant. This experimental tool can be deployed as a virtual laboratory, including within a flipped classroom setting, to promote active learning of traditionally challenging concepts such as the roles of eccentricity and precession in astronomical climate forcing, and in particular their interaction with Kepler's second law and the subsequent consequences for season length. [ABSTRACT FROM AUTHOR]

As one of the most important greenhouse gases, CO 2 is considered a major controlling factor of Earth's climate over geological timescales. However, the origins of quasi-periodic fluctuations in p CO 2 on a million-year timescale remain unclear. Here, we used published datasets of atmospheric p CO 2 , oxygen isotopes of benthic foraminifera (δ18O benthic) and global mean sea-level (GMSL) from 23 Ma to the present to explore the pacing of p CO 2 changes and concomitant climatic effects using multiple time series analysis approaches. Our results indicate that the evolution of late Cenozoic p CO 2 and climate was paced by the grand orbital cycles, in particular the ∼4.5 Myr and ∼2.4 Myr eccentricity cycles, and ∼1.3 Myr obliquity cycle. Periodic occurrence of cold conditions was associated with low climate seasonality during the minima of ∼4.5 Myr and ∼2.4 Myr eccentricity cycles. We suggest that cooler conditions are associated with decreased atmospheric p CO 2 as a result of higher organic carbon burial due to lower metabolic rate of heterotrophic bacteria and more organic carbon export to the deep ocean. Furthermore, the buildup of glaciers during the minima of grand eccentricity cycles might lower p CO 2 via increased ice cover and enhanced dust fluxes. In contrast, high seasonal climate may lead to an opposite effect on atmospheric p CO 2 during the maxima of the grand eccentricity cycles. Moreover, we found a distinct shift in the dominant signal from eccentricity to obliquity cycles recorded in the p CO 2 , δ18O benthic and GMSL datasets at ∼13 Ma, a time when perennial sea ice occurred in the Arctic and significant ice growth shown in Antarctica. We suggest that the change in the type and distribution of the ice sheets would shift glacial response to orbital forcing and hence mediated global climate and p CO 2. Our analysis reveals a clear synchrony among atmospheric p CO 2 , climate change, and the grand orbital cycles in the late Cenozoic. • Late Cenozoic changes in p CO 2 and climate were paced by the grand orbital cycles • Astronomically forced seasonal changes modulated global sea surface temperature and ice volume • A switch in the dominant cycle from eccentricity to obliquity was detected at ∼13 Ma [ABSTRACT FROM AUTHOR]

Much has been learned regarding orbital and millennial timescale climate changes after the onset of Northern Hemisphere glaciations (NHG) at ca. 2.7 Ma. By contrast, little is known about these variations before the NHG due to lack of high‐resolution records. Here we report first millennial resolution quantified East Asian summer monsoon (EASM) precipitation record from the north eastern Tibetan Plateau. The record supports astronomical forcing of EASM during the late Miocene, except for the period of 8.13–8.03 Ma when EASM experienced high amplitude variations at the 100‐, 20‐kyr, and suborbital bands, which is in sharp contrast with the damped astronomical forcing. Detection of strong 100‐kyr and millennial cycles during low eccentricity intervals of the warm late Miocene with ephemeral NH ice sheets cast doubt on NH ice sheet size variations as their exclusive forcing in the late Miocene and late Quaternary paleoclimatic records. Plain Language Summary: Millennial and 100‐kyr cycles in paleoclimate records are normally attributed to Northern Hemisphere ice sheet size variations. Here we present the first 1‐kyr resolution quantitative East Asian summer monsoon precipitation record from the northeastern Tibetan Plateau during the late Miocene, when Northern Hemisphere ice sheets were ephemeral. The record demonstrates strong 100‐kyr and clear millennial cycles. Detection of 100‐kyr and millennial cycles in this warm time interval cast doubt on Northern Hemisphere ice sheet size variations as their exclusive forcing in paleoclimatic records. Key Points: First 1‐kyr resolution quantitative northern China precipitation record during the late MioceneThe record reveals strong 100‐kyr and clear millennial cyclesDetection of 100‐kyr and millennial cycles in this warm interval challenges Northern Hemisphere (NH) ice sheet size variations as their exclusive forcing [ABSTRACT FROM AUTHOR]

Given increasing importance of tertiary reservoirs in the Middle East, the Miocene (Upper Aquitanian to mid-Langhian) Dam Formation in eastern Saudi Arabia was cored along a 40 km transect, to develop a high-resolution sequence framework, and examine the role played by astronomical forcing, moderate glacio-eustasy (20- to 40-m sea-level changes), and tectonic deformation in this distal foreland setting. The Dam Formation (up to 80 m thick) contains updip siliciclastics which interfinger downdip with marine carbonates. Siliciclastic facies include paleosol-capped, red mudrock (mudflat), green and gray mudrock (near-shore siliciclastic lagoon), rare mud clast–bearing sandstone (fluvial), and massive very fine to medium sandstone (terrestrial sand sheets, rare tidal channels). Carbonate facies include brecciated carbonates (paleosols), lime/clay-clast quartz wackestone (lag gravel), carbonate laminites and microbial heads and mounds (tidal flat and shallow subtidal), argillaceous quartzose marl (near-shore lagoon), peloid mudstone-wackestone (restricted lagoon), variably quartzose skeletal peloid mudstone to packstone (open lagoon), oolitic grainstone (hypersaline beach, tidal channel), mollusk packstone (hypersaline lagoon border), and foram-mollusk packstone-grainstone (seagrass meadows). The Dam Formation contains eight sequences, each of which contains 2 to 4 parasequence sets or individual parasequences. Sequences and individual parasequences are capped by paleosols and/or erosion surfaces, and microbial laminite caps are rare. Bases of parasequences locally are veneered with ravinement gravel lags or siliciclastics beneath shallowing-upward subtidal carbonates, and lack intercalated deeper water facies. Statistical analysis of core-gamma ray (API) vs depth (m) shows that accumulation rates were ~ 3 to 4 cm/kyr, considerably faster than long-term accommodation rates (~ 1.2 cm/kyr), indicating deposition occurred for only 40% of the time, the remainder of the time being non-depositional during many short-term lowered sea levels, evidenced by the coeval oceanic δ18O curve. Spectral analysis of the core-gamma ray logs show astronomical forcing within the eccentricity, obliquity, and precessional bands. Spectral analysis indicates that the eight Dam sequences (average 10 m thick, range < 5 to 18 m) are a mix of long-term obliquity (~ 1.2 Myr) and long-term eccentricity (400 k.y.) cycles. The 3- to 4.4-m sets/parasequences are short term (~ 100 kyr) cycles, and the 0.7- to 1.25-m parasequences are obliquity and precessional cycles. Given the updip position of the study area, repeated glacio-estutatic sea-level changes caused repeated shallow flooding (< 20 m) and emergence, which generated paleosol-bounded or erosionally capped sequences and parasequences. Although the distal foreland was undergoing synsedimentary deformation and slow but locally variable subsidence, which influenced variable thickness of units, astronomically driven glacio-eustasy was the dominant influence on timing of sequence and parasequence development. [ABSTRACT FROM AUTHOR]

The Western Pacific Warm Pool (WPWP) constitutes an important component within the global climate system by providing an enormous amount of heat and moisture to the global atmosphere. Nevertheless, past variability of oceanography and climate across the WPWP is still debated. Here, we compile newly generated and published surface and thermocline temperature and seawater stable oxygen isotope (δ18OSW) records from the WPWP north and south of the equator to monitor its variability, particularly in response to astronomical forcing, over the last glacial‐interglacial cycle. We find a coherent first‐order variability in all records from the northern and southern WPWP sites over the past 160 kyr indicating a relatively stable WPWP spatial structure. The second‐order variability is modulated by regionally varying influences. Precipitation varied uniformly across the WPWP marine realm. Thermocline records illustrate the influence of both northern and southern Pacific waters on the WPWP. Differences between the thermocline temperature records are attributed to the differing effect of obliquity on the thermocline water masses influencing the individual sites. Precession exerts an influence on the thermocline at both northern and southern WPWP sites. Variations in thermocline conditions in the precession band are attributed to a combination of modifications in the thermocline source waters, changes in the regional atmospheric circulation and the El Niño‐Southern Oscillation regime. Key Points: The spatial structure of the Western Pacific Warm Pool remained relatively stable over the past 160 kyrPrecipitation over the Western Pacific Warm Pool (marine realm) varied coherently and is mainly controlled by precessionThe thermocline across the WPWP is influenced by water masses of both North and South Pacific origin and modulated by astronomical forcing [ABSTRACT FROM AUTHOR]

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

Metre‐scale cycles are a common feature in Precambrian and Phanerozoic shallow water carbonate successions, and astronomically forced changes in sea‐level (Milankovitch cycles) may have been an important driver controlling their deposition. Nevertheless, the degree to which potentially low amplitude astronomically paced sea‐level oscillations may have controlled carbonate accumulation in deep time is unclear. In this study, a stochastic model of carbonate accumulation demonstrates how metre‐scale exposure‐bound sequences can be generated under conditions of random sea‐level change. These sequences have characteristic durations close to Milankovitch cycles, despite the absence of any astronomical control on their formation. Metre‐scale sequences with sub‐Milankovitch (millennial‐scale) durations can also be generated by the model, potentially shedding light on the origin of sub‐Milankovitch sequences such as those recorded on the Middle Triassic Latemar platform of Northern Italy. Sensitivity tests demonstrate how shallow water carbonates may be very sensitive to weak (i.e. low amplitude) astronomically forced sea‐level oscillations. Notably, strong statistical evidence (P < 0·01) for astronomical cycles can be preserved in modelled successions even when astronomical forcing contributes <1% of the sea‐level variance on million year timescales. Taken together, metre‐scale cycles with Milankovitch‐scale durations in ancient carbonate successions may reveal very little about the amplitude, or even the existence, of astronomical forcing as a sea‐level driver. [ABSTRACT FROM AUTHOR]

• A continuous grayscale scan is produced from the 2.5 Ga Dales Gorge Member BIF 'type section' to capture chert-iron banding patterns. • Spectral analysis reveals systematic and persistent banding and bundling patterns throughout the 135-m thick section with Milankovitchian affinities. • Cyclicity consists of 1–2 cm light–dark (chert-iron) bands bundled into 5 cm and/or 10–15 cm cycles, and superbundled into 30–45 cm cycles. • Banding patterns progressively organize into well-defined 10–15 cm cycles toward the top of the section. The Dales Gorge Member (DGM) of the Brockman Iron Formation (Hamersley Basin, Western Australia) is a classic banded iron formation (BIF) that was deposited during the Archean-Proterozoic transition just prior to the Great Oxidation Event. The goal of this study is to apply modern cyclostratigraphic principles to investigate the possible origins of the characteristic stratigraphic banding in this BIF, which indicates the influence of quasi-regular cyclic processes in the deposition of iron-rich and chert-rich lithologies. A grayscale scan series of the DGM 'type section' 47A* drillcore photographs from three cores drilled in the Wittenoon Gorge vicinity is examined using well established methods of time series analysis. Complex banding patterns suggest that Milankovitch forcing may have taken place with orbital-rotational parameters that were significantly modified from the present-day due to continuous planetary tidal dissipation over the past 2.5 billion years. The banding patterns change systematically and dramatically within the member in response to slowly varying environmental conditions, which are interpreted to be related to low-frequency sea level changes and/or tectonic evolution of the Hamersley Basin. [ABSTRACT FROM AUTHOR]

Deposition of the organic-rich shales of the Wufeng and lowermost Longmaxi formations (late Katian through Hirnantian) occurred in a relatively stable tectonic setting and commenced at approximately 4.5 Myr prior to the end-Ordovician glacial maximum. These organic-rich shales are important because they provide a continuous sedimentary record of high-frequency eustatic changes associated with ice-sheet expansion and shrinkage. Here, we carried out a high-resolution cyclostratigraphic study of Fe3+ series and associated geochemical analysis of the Wufeng and lowermost Longmaxi shales in order to better understand sea-level cyclicity in the late Katian through Hirnantian ocean. The organic-rich shales deposited during this interval in the EHD1 drill core (Yichang, China) record four major Myr-scale eustatic cycles, which were associated with third-order sea-level fluctuations. Within each of these major cycles, 3–4 minor eustatic cycles corresponding to 405-kyr long eccentricity astronomical cycles were recognized and representing fourth-order eustatic changes. The cyclostratigraphic age of this study is generally in agreement with the radiometric dates in GTS2012, although the duration of the Hirnantian stage is ~0.5 Myr longer than previously thought. This study also infers glacial controls on the depositional environment of the organic-rich shales, as enhanced cooling triggered ice-sheet expansion and concurrent sea-level fall, leading to higher thermohaline circulation intensity and enhanced paleoproductivity through upwelling and terrestrial influx. In contrast, warming intervals led to ice-sheet shrinkage and concurrent deepening characterized by water column stratification and reduced nutrient supply. The results provide evidence in support of continuous continental glaciation in the late Katian through Hirnantian. • A floating astronomical time scale (ATS) for the Late Ordovician was successfully established. • The sea-level oscillations in the Late Ordovician were likely driven by orbital cycles. • A close link between orbitally-forced climate change and organic-rich Wufeng shale was built. • This study supports a continuous continental glaciation during the Late Ordovician. [ABSTRACT FROM AUTHOR]

Under the background of global warming, the impact of climate change in the densely populated North China Plain is becoming increasingly prominent. Cenozoic deposits in this area can provide insights into the evolution of the monsoon and the associated climate changes. This study focused on the SYZK01 borehole in the Beijing Plain area, primarily consisting of fluvial-lacustrine sediments. By employing detailed magnetic stratigraphy and multi-dating methods, we determined the age of the deposits to be approximately 0–3.3 Ma. Grain size and spontaneous potential logging were selected as proxies for paleoclimate. Our results reveal a strong coupling between the 0.063–0.25 mm grain size component, spontaneous potential logging and deep-sea δ18O in the overall sediment, confirming that glacial-interglacial cycles are the most significant form of climate change affecting the sedimentation process in the North China Plain. We observed a dominant 100 kyr eccentricity cycle within the 0.063–0.25 mm grain size component through the spectral analysis of the time-domain series of grain size indicators. In comparison, the 41 kyr cycle exhibited significant influence only from 1.1 to 0.6 million years ago. Notably, our study highlights that the SYZK01 borehole records the "late Pliocene-early Pleistocene 100 kyr problem," characterized by phase and amplitude variations that do not align with Earth's orbital eccentricity. • A drill core on the northern edge of the North China Plain was constrained to 0– 3.3 Ma. • Spectral analyses revealed dominant influences of 100 kyr eccentricity cycles between 0 – 3.3 Ma. • The phase and amplitude variation at the 100 kyr band in our record mismatch that of eccentricity. [ABSTRACT FROM AUTHOR]

Bedding-parallel fibrous calcite veins are commonly found in low-permeability strata rich in organic matter from various geological periods. Despite their importance in examining the fluid flow in sedimentary basins, dynamics of crustal permeability and mineralization, microbial mineralization, detection of early life signatures, and hydrocarbon production and accumulation, the growth processes of these veins remain inconclusive. Here we show a two-stage model to explain the growth of bedding-parallel fibrous calcite veins, by analyzing a wide range of organic geochemical, elemental, isotopic, and petrographic data from both new and published sources. This model consists of the early diagenetic stage and oil-generative window, with a focus on samples from the middle Eocene strata of the Bohai Bay Basin and the Cavan Bluff Limestone. This study emphasizes the crucial role of early diagenetic processes, such as anaerobic microbial activities, in initiating the formation of bedding-parallel fibrous calcite veins at the sediment-water interface. Additionally, the further modification and secondary enlargement of these veins by fluids generated from hydrocarbon production and clay evolution are described. While this model may not be applicable to all bedding-parallel fibrous calcite veins, it provided valuable insights and helped reconcile seemingly contradictory findings regarding these veins. Furthermore, the study indicates the potential of bedding-parallel fibrous calcite veins in paleoenvironmental reconstruction and emphasizes the significance of reevaluating certain existing knowledge within the fields that employ these veins as specimens. [Display omitted] • The growth of bedding-parallel fibrous calcite veins occurs in distinct stages. • The earliest origin of bedding-parallel fibrous calcite veins can be traced back to the synsedimentary period. • Bedding-parallel fibrous calcite veins grow at a rate ranging from ∼ 5 to 7 μm/kyr during the early diagenetic stage. • The origin of bedding-parallel fibrous calcite veins is dependent on anaerobic microbial processes. [ABSTRACT FROM AUTHOR]

The continental shelf and slope, with upwelling systems, are usually accompanied by the formation of oxygen minimum zones, thereby stimulating marine paleoproductivity and promoting organic matter (OM) enrichment. However, due to a more oxygen-enriched environment, a distinct paleoecological characteristic, and the uncertainty of upwelling effects, it remains ambiguous whether a similar mechanism of OM preservation occurs in the adjacent carbonate platform. Here, limestone–marl alternations (LMAs) that developed in the Yangtze Carbonate Platform (YCP) during the Middle Permian were selected as the research object and compared with the chert–mudstone alternations developed on the Lower Yangtze continental shelf (LYCS). Both sets of rhythmites belong to the contemporaneous products of the Permian Chert Event in South China. Considering that the Middle Permian rhythmites in South China contain the Milankovitch record and that upwelling was controlled by astronomically forced monsoons, this study investigated the impact of upwelling on the carbonate platform by adopting astronomical cycle research. Based on GR data, a framework of astronomical cycles was established. The suboxic to anoxic conditions of the YCP are supported by evidence from syngenetic pyrite framboids, Ce/Ce* ranges, and U EF –Mo EF covariation. Upwelling geochemical indicators and the detection of a pivotal (∼210-kyr) astronomical cycle regarding upwelling indicate that the YCP was affected by upwelling. The paleoproductivity/OM/fossil-related data exhibit this ∼210-kyr astronomical cycle, and the correspondence between the converted AMs determines that upwelling enhanced marine primary paleoproductivity and OM preservation. However, the intensities of short eccentricity cycles exceed those of the ∼210 kyr cycle in the time series analyses of data from the nearshore YCP. Additionally, the covariations between the upwelling proxy and total fossil content confirm the impact of upwelling on biomass of benthic organisms. Therefore, the (monsoon-driven) upwelling system in the continental shelf can extend to the carbonate platform. After reaching the platform, under the control of a (an) (astronomically forced) climatic–oceanic system, limited upwelling can stimulate primary productivity and marine OM preservation; however, upwelling reduces biomass in the bottom water. In the nearshore side of the platform, detrital dilution likely replaces upwelling as the primary stimulus for productivity. Moreover, this study reveals and explains the ∼200-kyr cycles in the Permian strata of South China for the first time. [Display omitted] • The ∼200-kyr cycles are first revealed and explained in the Permian strata of South China. • Limited upwelling increases productivity and OM preservation in the carbonate platform. • Upwelling promotes productivity and thus depletes oxygen, reducing benthic biomass in the platform. • A model for the effect of the upwelling systems along continental shelves on carbonate platforms is proposed. • Milankovitch cycles are the basis of the Maokou LMAs forming a set of source rocks. [ABSTRACT FROM AUTHOR]

• New astrochronology, carbon isotope, and Hg isotope data on the CPE. • ∼1.2 Myr obliquity cycles significantly dominated sea level oscillations. • Orbital forcing amplified the climatic and environmental response of the CPE. Global climate change has profound implications for human survival and prosperity. The Carnian (early Late Triassic, ∼233 Ma) was a time of global environmental perturbations, climatic change, and biotic turnover, commonly known as the Carnian Pluvial Episode (CPE). However, the understanding of possible triggering mechanisms of the CPE is still partially untraveled due to the lack of a high-resolution chronostratigraphic framework. Here we present an astrochronology of episodic negative carbon isotope excursions (NCIEs) observed in the shallow marine sediments of the Bagong Formation in the Qiangtang Basin (Tibetan Plateau, China) to explore the role of orbital forcing during the CPE. This study marks the first identification of five episodic NCIEs in the Carnian strata of the Bagong Formation. These NCIEs correspond with five distinct periods of increased detrital influx. The coupling relationship between each phase of NCIE and related terrigenous input indicates that episodic NCIEs may be influenced by pulses of active continental weathering. Mercury isotope is contemporaneous with the active volcanism that triggered the onset of the NCIEs; however, the impact of volcanism in the Qiangtang Basin was weak and almost non-existent at this time. An anchored floating astronomical timescale (ATS) for the episodic NCIEs is established, revealing evidence for a 405 kyr eccentricity in high-resolution gamma ray data series using time series analysis. A ∼13.16 Myr-long ATS of the Bagong Formation is developed by astronomical tuning of gamma ray logs to the stable 405-kyr long-eccentricity cycles. This floating ATS takes the U-Pb zircon as its anchor point and establishes an anchored floating ATS of the Bagong Formation from 233.16 ± 1.37 Ma to 220.4 ± 1.1 Ma. The innovative astrochronology approach, employing a sedimentary noise model, has successfully reconstructed sea-level changes during the Late Triassic period. These findings align well with the documented global sea-level fluctuations of the same era. The antiphase relationship of the filtered ∼1.2 Myr cycles between the sedimentary noise model sea-level curve and the obliquity modulation cycles demonstrates that the ∼1.2 Myr modulation cycles may be the main driver of sea level changes during the Late Triassic. The ∼1.2 Myr obliquity modulation maxima correlate well with the high sea level, episodic NCIEs, global warming, and marine life crisis, suggesting that obliquity forcing could have played a prominent role during the CPE. Our results reveal that the orbital forcing enhanced the hydrological cycle during the CPE, which provides a broader perspective of the CPE-related to the astronomical forcing. [ABSTRACT FROM AUTHOR]

The latest Paleocene to early Eocene was an interval of globally warm climate. However, the driving mechanisms regulating climate across this interval remain unclear due to the paucity of well-dated and stratigraphically continuous records from terrestrial basins. In this study, we present a continuous ∼430-m lacustrine core record from the QY-1 borehole spanning the late Paleocene-Early Eocene in the Subei Basin, East China. This unique record can be used to better elucidate the response of terrestrial sedimentation to astronomically forced climate change. A 4.54 Myr long astronomical time scale spanning 57.1 to 52.56 Ma is constructed for the second member of the Funing Formation (E f 2) based on magnetostratigraphy and cyclostratigraphy. Low-latitude summer insolation via eccentricity modulation of precession controlled paleolake evolution in the basin during the studied interval. At the same time, we show that the climate system during this greenhouse state was sensitive enough to respond to the small changes in insolation associated with 200-kyr eccentricity cycles. Evidence from gamma ray data suggests that the climate in the Subei Basin changed from warm and humid to arid at ∼54.1 Ma. • Establish an ATS with magnetostratigraphy and cyclostratigraphy for E f 2 in Subei Basin, East China. • A record of astronomically forced climate changes in the late Paleocene to early Eocene terrestrial succession in the Subei Basin was conformed. • The climate system during this greenhouse state was sensitive enough to respond to the small changes in insolation associated with 200-kyr eccentricity cycles. [ABSTRACT FROM AUTHOR]

Abstract This paper addresses two fundamental issues in cyclostratigraphy and paleoclimatology: identification of astronomical forcing in sequences of stratigraphic cycles, and accurate evaluation of variable sedimentation rates. The technique presented here considers these issues part of an inverse problem and estimates the product-moment correlation coefficient between the power spectra of astronomical solutions and paleoclimate proxy series across a range of test sedimentation rates. The number of contributing astronomical parameters in the estimate is also considered. Our estimation procedure tests the hypothesis that astronomical forcing had a significant impact on proxy records. The null hypothesis of no astronomical forcing is evaluated using a Monte Carlo simulation approach. The test is applied using a sliding stratigraphic window to track variable sedimentation rates along the paleoclimate proxy series, in a procedure termed “eCOCO” (evolutionary correlation coefficient) analysis. Representative models with constant and variable sedimentation rates, and pure noise and mixed signal and noise series are evaluated to demonstrate the robustness of the approach. The method is then applied to Cenozoic, Mesozoic and Paleozoic paleoclimate series. The Cenozoic case study focuses on a high-resolution Paleocene–Eocene iron concentration series from ODP Site 1262 (Leg 208) covering the Paleocene–Eocene Thermal Maximum and Eocene Thermal Maximum 2 events. The eCOCO time-calibrated iron series confirms previous findings of a role for long-term astronomical forcing of these Eocene events. The Mesozoic case study applies eCOCO to the classic Late Triassic Newark depth rank series of eastern North America. The estimated high-resolution sedimentation rate map in this case demonstrates a causal link between variations in depositional environment and sedimentation rate. Finally, the Paleozoic case study supports the cyclostratigraphic interpretation of a Devonian magnetic susceptibility series at La Thure, Belgium and provides new insights into changes of the depositional setting at this location. Taken together, eCOCO is a powerful tool for simultaneously evaluating sedimentation rates and astronomical forcing for paleoclimate series throughout the Phanerozoic. Highlights • The “ECOCO” method is developed to track sedimentation rate changes in astronomically forced paleoclimate series. • A null hypothesis of no astronomical forcing is evaluated using Monte Carlo simulation. • ECOCO is applied to Cenozoic, Mesozoic, and Paleozoic paleoclimate series. • ECOCO sedimentation rates provide insights into stability of depositional environments. [ABSTRACT FROM AUTHOR]

Abstract An unusually short glaciation interrupted the warm Pliocene around 3.3 Ma (Marine Isotope Stage (MIS) M2). Different hypotheses exist to explain why this glaciation event was so pronounced, and why the global climate system returned to warm Pliocene conditions relatively quickly afterwards. One of these proposed mechanisms is a reduced equator-to-pole heat transfer, in response to a tectonically reduced Indonesian Throughflow (ITF). The ITF is a critical part of the global thermohaline ocean circulation, transporting heat from the Indo-Pacific Warm Pool to the Indian Ocean. When ITF connectivity is reduced, the water and heat supply for the Leeuwin Current, flowing poleward along Australia's west coast, is also diminished. To assess the possible relationship between mid-Pliocene glaciations and latitudinal heat transport through the Indonesian Throughflow, we constructed a multi-proxy orbital-scale record for the 3.7–2.8 Ma interval from International Ocean Discovery Program (IODP) Site U1463, off northwest Australia. The comparison of the Site U1463 record with paleoclimate records from nearby Site 763 and West Pacific Warm Pool Site 806 allows for a detailed regional reconstruction of Pliocene paleoceanography and thus for testing the proposed hypothesis. An astronomically-paced decrease in potassium content characterizes the late Pliocene interval of U1463. This record documents the increasing aridity of northwest Australia, periodically alleviated by reinforced summer monsoon precipitation under summer insolation maxima. The δ 18 O record of the planktonic foraminifer Globigerinoides sacculifer correlates exceptionally well with the sea surface temperature (SST) record from Site 806 in the West Pacific Warm Pool, even during MIS M2. Hence, Site U1463 preserves an uninterrupted ITF signal even during Pliocene glaciations. However, the U1463 δ 18 O G.sacculifer record exhibits a 0.5‰ offset with the nearby Site 763A record around MIS M2. This implies that Site 763A, about 500 km west of U1463, more closely tracks Indian Ocean SST records across MIS M2. The U1463 data reveal that heat-transport through the Indonesian Throughflow did not shut down completely during MIS M2, but rather its intensity decreased prior to and during MIS M2, causing Site 763A to temporarily reflect an Indian Ocean, rather than an ITF signal. We conclude that ITF variability significantly influenced latitudinal heat transport by means of the Leeuwin Current and hence contributed to the relative intensity of MIS M2. We propose the ITF valve between the Pacific and Indian Ocean as a positive feedback mechanism, in which an initial sea level lowering reduces ITF heat transport, in turn amplifying global cooling by advancing the thermal isolation of Antarctica. Highlights • The ITF is a tectonically-controlled modulator of orbital-scale climate variability. • At 3.3 Ma, ITF heat transport is reduced, but the Leeuwin Current continues to exist. • At 3.3 Ma, latitudinal heat transport declines and amplifies global cooling. • Late Pliocene humid-to-arid transition in NW Australia is paced by orbital forcing. • Site U1463 unceasingly displays a Warm Pool signal throughout the Late Pliocene. [ABSTRACT FROM AUTHOR]

Abstract: The astronomical timescale accuracy generally exceeds other dating methods. Precise age models are pivotal for paleoclimatic research. The middle Eocene astronomical timescale has been poorly constrained due to scarcity of suitable records leading to the so call “Eocene astronomical timescale gap.” We present magnetic susceptibility and color proxy records from an expanded 60 m long cyclic hemipelagic succession from the Oyambre Cape in northern Spain (∼1.3 My long stratigraphic section tuned to the ∼43.1–44.4 Ma interval in the Lutetian stage). We use the strong eccentricity amplitude modulation of precession in the sedimentary record for orbital tuning. The tuned record is correlated at precession level with previously tuned Ocean Drilling Program (ODP) Site 1260 from the equatorial Atlantic (the only oceanic record that registers geochemical variations in the precession band) and to other lower resolution deep‐sea records at eccentricity level from the Southern Atlantic. Our data is consistent with a very long eccentricity minimum (driven by a ∼2.4 My periodicity) at 43.15 Ma in the orbital solutions and an age for the C20n/C20r reversal boundary at ∼43.45 Ma. However, we challenge previous correlations between these Atlantic sites (shifts of one 100 ky eccentricity cycle). Data allows to rule out correlation to either younger or older 405 ky eccentricity cycles, which constrains chronologies for the middle Eocene, emphasizing the need for consistent astrochronological frameworks involving expanded outcrops. This should aid to overcome oceanic drilling shortcomings and sedimentary complexities. Our study highlights this integration need to achieve accuracy and stability of orbital timescales underpinning Eocene paleoclimatic records. [ABSTRACT FROM AUTHOR]

North Atlantic Deep Water (NADW) currently redistributes heat and salt between Earth's ocean basins, and plays a vital role in the ocean-atmosphere CO 2 exchange. Despite its crucial role in today's climate system, vigorous debate remains as to when deep-water formation in the North Atlantic started. Here, we present datasets from carbonate-rich middle Eocene sediments from the Newfoundland Ridge, revealing a unique archive of paleoceanographic change from the progressively cooling climate of the middle Eocene. Well-defined lithologic alternations between calcareous ooze and clay-rich intervals occur at the ∼41-kyr beat of axial obliquity. Hence, we identify obliquity as the driver of middle Eocene (43.5–46 Ma) Northern Component Water (NCW, the predecessor of modern NADW) variability. High-resolution benthic foraminiferal δ 18 O and δ 13 C suggest that obliquity minima correspond to cold, nutrient-depleted, western North Atlantic deep waters. We thus link stronger NCW formation with obliquity minima. In contrast, during obliquity maxima, Deep Western Boundary Currents were weaker and warmer, while abyssal nutrients were more abundant. These aspects reflect a more sluggish NCW formation. This obliquity-paced paleoceanographic regime is in excellent agreement with results from an Earth system model, in which obliquity minima configurations enhance NCW formation. [ABSTRACT FROM AUTHOR]

A high-resolution carbon isotope record is presented for Campanian strata of the Bottaccione section (Umbria-Marche Basin), through an interval that constitutes the standard reference section for the geomagnetic polarity time scale. The identification of prominent δ 13 C excursions and high frequency variations allows the establishment of robust stratigraphic markers to link this new Tethyan δ 13 C record with the Boreal realm (Lägerdorf-Kronsmoor section, Northwest Germany and the Trunch borehole, Norfolk, UK). A decoupling of baseline δ 13 C values between the Boreal and the Tethyan realm is observed during the mid-Campanian, reflecting a plausible change in intermediate/deep-water mass exchange due to a more restricted Tethyan gateway; this is hypothesized to be a consequence of northward movements of Africa associated with opening of the South Atlantic Ocean. Statistical evaluation of a segment of the δ 13 C dataset with the TimeOpt method for astrochronologic testing provides strong evidence of astronomical forcing, and underscores the potential for development of a complete astronomically tuned Campanian Stage at Bottaccione, allowing astronomical calibration of key geomagnetic and paleobiologic datums. [ABSTRACT FROM AUTHOR]

A prevailing viewpoint in paleoclimate science is that a single paleoclimate record contains insufficient information to discriminate between typical competing explanatory models. Here we show that, by using the algorithm SMC2 ('sequential Monte Carlo squared') combined with novel Brownian-bridge-type proposals for the state trajectories, it is possible to estimate Bayes factors to sufficient accuracy to be able to select between competing models, even with relatively short time series. The results show that Monte Carlo methodology and computer power have now advanced to the point where a full Bayesian analysis for a wide class of conceptual climate models is possible. The results also highlight a problem with estimating the chronology of the climate record before further statistical analysis: a practice which is common in paleoclimate science. Using two data sets based on the same record but with different estimated chronologies results in conflicting conclusions about the importance of the astronomical forcing on the glacial cycle, and about the internal dynamics generating the glacial cycle, even though the difference between the two estimated chronologies is consistent with dating uncertainty. This highlights a need for chronology estimation and other inferential questions to be addressed in a joint statistical procedure. [ABSTRACT FROM AUTHOR]

The middle to late Eocene marked a key transition from greenhouse to coolhouse. However, a lack of high-resolution and temporally well-constrained continental records hinders our understanding of the driving mechanisms of climate change during this period. In this study, we combined magnetostratigraphy and cyclostratigraphy to establish a high-resolution astronomical time scale spanning the middle to late Eocene (∼42.4 Ma to ∼35.3 Ma) through a 214-m succession of the continental Honghe Formation in the Weihe Basin, North China. Our results show that variability in the hydroclimate of the Weihe Basin at this time was dominated by eccentricity (∼405 kyr and ∼100 kyr) and obliquity (∼1.15 Myr and ∼173 kyr) forcing. Meridional insolation gradient variations controlled by obliquity, and low-latitude summer insolation via eccentricity modulation of precession jointly controlled paleolake evolution in the basin during the ∼42.4 Ma to ∼35.3 Ma interval, rather than being controlled by eccentricity or obliquity as previously inferred. Our study provides new insights into the driving mechanisms of orbital-scale hydroclimate evolution in continental lake basins during the ice-free middle to late Eocene. • Astronomical time scale for the middle to lower Honghe Formation of the Weihe Basin, North China. • Obliquity and Eccentricity jointly controlled paleolake evolution in the Weihe basin during middle to late Eocene. [ABSTRACT FROM AUTHOR]

Milankovitch cycles are quasi-periodic fluctuations in insolation forced by variations in the Earth's astronomical parameters, inducing climate change, and in turn affecting sedimentation and the formation of cyclostratigraphy. Astronomical calibration of the cyclostratigraphy can be exploited as a high-resolution (0.02–0.4 Myr) astronomical time scale (ATS), facilitating the reconstruction of Earth's evolutionary history. The ATS is already an important geochronometer for the Cenozoic and Mesozoic eras, however, the ATS for the Paleozoic Era has yet to be fully constructed. Radioisotopic age-calibrated Milankovitch cycles have been detected in Paleozoic strata, linked to the hierarchy of sedimentary cycles deposited in the continental, paralic, and marine environments. The orbital eccentricity metronome (i.e., 405-kyr cycle) has already been used to construct the ATS for the timing of Paleozoic geological and climatic events. Here, we review Paleozoic cyclostratigraphy and develop a provisional ATS from published paleoclimatic proxy time series, which results in revisions to the timing of key geological events in the Paleozoic Era. [ABSTRACT FROM AUTHOR]

The Miocene Hanjiang Formation of the Pearl River Mouth Basin (PRMB) forms one of the most productive hydrocarbon reservoirs in China. Sparse biostratigraphic age control and limited dating hinder a thorough understanding of sea-level change and its sedimentary expression through this formation. To establish the relationship between third-order sea-level changes, their expression in the lithological record and astronomical forcing, a sequence stratigraphic and cyclostratigraphic analysis has been conducted through the Hanjiang Formation in the LF14 borehole. One second-order sequence and six third-order sequences are recognized based on gamma ray (GR) data, vertical lithofacies changes and sedimentary stacking patterns. Time series analysis of the GR data and subsequent interpretation allows recognition of approximately eighteen 405 kyr long eccentricity cycles. Based on this cyclostratigraphy, we constructed a ∼7.22-Myr floating astronomical time scale (ATS) for the Hanjiang Formation. We anchored this timescale to globally significant biostratigraphic events preserved in the basin to build an absolute ATS spanning 17.423 ± 0.4 to 10.221 ± 0.4 Ma. A prominent ∼1.2-Myr periodicity is identified in the amplitude modulation (AM) envelope curves of ∼41-kyr obliquity cycles preserved in the record. This ∼1.2-Myr periodicity shows good agreement with our sequence stratigraphic analysis and global eustatic curves. Our results suggest that ∼1.2-Myr obliquity AM was the main driver of third-order sea-level change and sequence development in the PRMB. Combined application of cyclostratigraphic and sequence stratigraphic analysis (utilizing INPEFA and wavelet transform methods) are demonstrated to be useful for understanding the drivers and subdivisions of third-order sequence evolution on a regional scale. • Astronomical calibration of the middle Miocene succession in the Pearl River Mouth Basin. • Long-period ∼1.2-Myr cycles control on third-order sequences and sea-level change. • Third-order sequences subdivision by an integrated INPEFA–wavelet transform–cyclostratigraphic method. [ABSTRACT FROM AUTHOR]

[Display omitted] • The duration of the Middle and Upper Dawenkou Formation is 6.5 ± 0.4 Myr. • Halite-gypsum mudstone-mudstone rhythms are paced by astronomical forcings. • Halite deposits occurred during periods of minima short eccentricity. • Warm/dry winters and cool summers led to halite deposition. Halite is a type of evaporite that can be processed into refined salt for food processing, and used as an important raw material in the chemical industry. However, our understanding of the astronomical forcing pattern on halite formation at the sedimentary basin scale is still limited. Here, we present a halite-rich lacustrine record from the middle-late Eocene through the early Oligocene of the Dawenkou Formation in the Huanggang Basin, Eastern China. A ∼ 6.5-Myr-long floating astronomical time scale was constructed based on a 405-kyr orbital eccentricity cycle tuning of gamma-ray (GR) series measured from the Upper and Middle members of the Dawenkou Formation. Our results indicate that halite intervals in the Middle Member of the Dawenkou Formation correspond well with the minima of the 100 kyr orbital eccentricity, suggesting the short eccentricity-induced climatic cycles forcing of halite formation by impact on seasonal contrasts. Our work provides essential context for understanding the pattern of halite deposits from the aspect of climate cycles at the sedimentary basin scale. [ABSTRACT FROM AUTHOR]

The Early Jurassic ( ca 201 to 174 Ma) was marked by a series of rapid perturbations in climate, the environment and global geochemical cycles, which have been linked to volcanic outgassing and the release of biogenic or thermogenic methane into the ocean-atmosphere system. The state of the global carbon cycle and prevailing climatic and environmental conditions that existed at this time are, however, poorly constrained. Here, mudrocks of the Lower Sinemurian Arietites bucklandi ammonite Biozone at coastal exposures at Kilve, Somerset, UK, have been studied. This succession includes laminated organic-rich black shales, which are present throughout the Bristol Channel Basin, and coincides with a 2 to 3‰ negative carbon-isotope excursion, distinct changes in inferred land vegetation and abundant marine prasinophytes (green algae). The event itself does not represent a single perturbation of the regional environment, but follows in a sequence of eccentricity-modulated, precession-paced perturbations that occur throughout the preceding Hettangian stage, with the periodic formation of organic-rich laminated black shales in the Bristol Channel Basin. However, the Early Sinemurian event studied herein is more extreme in nature, with sedimentary total organic carbon values of 5 to 11% persisting over about 2 m, representing ca 100 kyr, possibly in phase with short ( ca 100 kyr) and long ( ca 405 kyr) eccentricity forcing. The formation of methane-seep carbonate-cemented mounds took place relatively soon after the deposition of laminated black shales. Biogenic methane probably formed in response to microbial methanogenesis in the organic-rich black shale, which was subsequently channelled to the sediment-water interface approximately 5 m above the source bed, and ca 200 kyr after cessation of formation of the black shale. [ABSTRACT FROM AUTHOR]

Whether during past climate stages or into a progressively warming world, changes in precipitation constitute a key component of climatic change. Quantitative proxies for palaeo-precipitation are relatively rare. The magnetic properties of the windblown loess units and interbedded palaeosols of the famous Chinese Loess Plateau provide key palaeo-precipitation data for this populous, monsoon-dominated region. The loess/palaeosol sediments record rainfall totals, directly complementing the oxygen isotope records of Chinese speleothems. These isotopic records predominantly reflect moisture source, and hence large-scale atmospheric circulation changes. The two major Asian monsoon systems appear to display antiphase behaviour. Dominance of the Indian summer monsoon system seems associated with minimum precession/maximum northern hemisphere summer heating; dominance of the East Asian summer monsoons with maximum precession. At ∼2.8 Ma, more intense development of the East Asian winter monsoon initiated major increases in dust deposition rates, and formation of relatively unweathered loess layers. Glacial-stage loess units then interleaved with interglacial/interstadial-stage palaeosols throughout the Quaternary period. Decoupling of the loess/palaeosol rainfall records from the Chinese cave records of moisture source shows that the Indian and East Asian monsoon winds were continuously driven by precessional forcing while summer monsoonal rainfall was greatly suppressed during cool, glacial stages. The timing of these East Asian climatic transitions, the subsequent intensification of northern hemisphere glaciations, and the association between monsoon circulation changes and North Atlantic temperatures, indicates a possibly leading global role for these monsoonal changes via alterations in the poleward distribution of heat and moisture. [ABSTRACT FROM AUTHOR]

The Green River Formation (GRF) provides one of the premier paleoclimate archives of the Early Eocene Climatic Optimum (∼50 Ma), representing the apex of the early Cenozoic greenhouse climate. Rhythmic lake-level variability expressed in the GRF has inspired numerous hypotheses for the behavior of the Eocene hydrologic cycle, including its linkage to astronomical forcing, solar variability, and the El Niño Southern Oscillation (ENSO). However, the lack of sufficient proxy data to document atmospheric water-mass transport and the geographic pattern of evaporation/precipitation/runoff has made it difficult to discriminate between different models for astronomical forcing. Variable 87 Sr/ 86 Sr ratios of bedrock that encompass the GRF provide an opportunity to reconstruct the spatial expression of the Eocene hydrologic cycle and its linkage to lake level. Here Sr isotope data from the Wilkins Peak Member, a rhythmic succession that has been demonstrated to record Milankovitch forcing of lake levels, indicate that high lake levels reflect an increased proportion of runoff from less radiogenic rocks west of the basin, eliminating a number of the existing astronomical-forcing hypotheses. The 87 Sr/ 86 Sr variability is consistent with a change in mean ENSO state, which is predicted by climate models to be linked to orbital-insolation. Thus, the 87 Sr/ 86 Sr data reveal a coupling of high frequency (ENSO) and low frequency (astronomical) climate variability, and also predict the existence of sizable astronomically-forced alpine snowpack during the last greenhouse climate. More broadly, this study demonstrates the utility of 87 Sr/ 86 Sr as a powerful tool for reconstructing the deep-time hydrologic cycle. [ABSTRACT FROM AUTHOR]

The Oligocene-Miocene transition period was characterized by a decrease in global CO levels, expansion of polar ice sheet, fall in global sea-level, etc. However, the reasons for, and mechanisms of, this global, extreme-cold climate change event (Mi-1) still remain controversial. Our samples from the core of the Ocean Drilling Program (ODP) Leg 154, Site 926, located in the equatorial Atlantic, mainly consist of light-gray, nannofossil chalk with foraminifers interbedded with green-ish-gray, clayey, nannofossil chalk sediments. Color variation from light-gray layers (up to 80% carbonate content) to dark layers (∼60% carbonate content) was observed to occur cyclically at the meter scale. Therefore, we chose color reflectance lightness ( L*) data as the paleoclimate proxy on which to perform cyclostratigraphic analysis because it could reflect carbonate content changes. Based on the recognition of the 405 kyr long eccentricity and ∼40 kyr obliquity cycles of the L* series, we tuned the series to establish an absolute astronomical time scale using the published age of the Oligocene-Miocene boundary (OMB) as the anchor for an absolute age control point. The power spectra of the tuned L* series showed that the long eccentricity signals became significantly weak, while the obliquity signals became strong, from the Late Oligocene to the Early Miocene. The 405 kyr long eccentricity minimum coincided with the 1.2 Myr obliquity node at the OMB, and similar convergences might be closely related to other extreme-cold events in Earth's history. In addition, the sedimentation accumulation rate, oxygen isotopes of benthonic foraminifers, and rodents' per-taxon turnover rate from Central Spain showed the same ∼2 Myr cyclicity, which indicates the significant influence of Earth-orbital forcing on the Earth system and ecological evolution on the million-year time scale. [ABSTRACT FROM AUTHOR]

The late Ordovician Pingliang Formation on the southwestern margin of the Ordos Basin, North China, consists of rhythmic alternations of shale, limestone, and siliceous beds. To explore the possible astronomical forcing preserved in this lithological record, continuous lithological rank and magnetic susceptibility (MS) stratigraphic series were obtained from a ~ 34 m thick section of the Pingliang Formation at Guanzhuang. Power spectral analysis of the MS and rank series reveal 85.5 cm to 124 cm, 23 cm to 38 cm, and 15 cm to 27 cm thick sedimentary cycles that in ratio match that of late Ordovician short eccentricity, obliquity and precession astronomical cycles. The power spectrum of the MS time series, calibrated to interpreted short orbital eccentricity cycles, aligns with spectral peaks to astronomical parameters, including 95 kyr short orbital eccentricity, 35.3 kyr and 30.6 kyr obliquity, and 19.6 kyr and 16.3 kyr precession cycles. The 15 cm to 27 cm thick limestone–shale couplets mainly represent precession cycles, and siliceous bed deposition may be related to both precession and obliquity forcing. We propose that precession-forced sea-level fluctuations mainly controlled production of lime mud in a shallow marine environment, and transport to the basin. Precession and obliquity controlled biogenic silica productivity, and temperature-dependent preservation of silica may have been influenced by obliquity forcing. [ABSTRACT FROM AUTHOR]