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Ocean Drilling Program Site 1143 of Leg 184 in the southern South China Sea (SCS) recovered a continuous sedimentary sequence since the Late Miocene (~ 10 Ma), which provides a unique record for better understanding the tectonic, environmental, and climatic evolution in the southern part of the SCS. In this study, we conducted a detailed rock magnetism and paleomagnetism study on 637 discrete samples taken from 512.1 m cores of Hole 1143C. Rock magnetic measurements indicate that the main magnetic mineral is single domain magnetite for samples from the upper 200 mcd (meter composite depth). All samples were subjected to stepwise alternating field demagnetization. The demagnetization behaviors of the samples below 200 mcd were erratic and unstable, owing to very weak remanent magnetization. A total of 15 reliable magnetic reversal events were identified in the upper 190 mcd cores of Hole 1143C based on the declination variations of the characteristic remanent magnetization, which can be correlated very well with the Geomagnetic Polarity Time Scale 2012 in combination with biostratigraphic data and astronomical time scales. Our new magnetostratigraphic results provide a more confident age framework for the southern SCS since the Early Pliocene. [ABSTRACT FROM AUTHOR]

Integrated Ocean Drilling Program (IODP) Site C0002 was cored in the Kumano Basin, which is a forearc basin in the Nankai margin of southwest Japan. The uppermost 1052.5 m of sediment in the accretionary prism, slope, and overlying forearc basin was recovered discontinuously during Expedition 315. Magnetic minerals from Site C0002 were studied to understand sedimentary, tectonic, and diagenetic processes in this forearc environment. Four rock magnetic units (A, B, C, and D) are identified. In the forearc basin sediments of Unit A, high concentrations of detrital magnetic iron oxides in surface sediments give way to progressive diagenetic dissolution with depth. Nevertheless, large titanomagnetite particles survived diagenetic dissolution along with magnetic nanoinclusions within host silicates that preserve a relict magnetic signal that records climatic modulation of sediment delivery to the Kumano Basin. The authigenic iron sulphides, ferrimagnetic greigite and paramagnetic pyrite, formed in association with gas hydrates and anaerobic oxidation of methane in the forearc basin sediments of Unit B. Methane venting from deeper within the slope sediments of Unit C and accretionary prism sediments of Unit D has given rise to formation of pyrite aggregates along sediment fractures and has contributed to further diagenetic depletion of magnetic signals in these units. Structural evolution of the Kumano Basin has caused migration of the gas hydrate stability zone (GHSZ) through time so that the Site C0002 sediments record both the present and fossil GHSZ positions. Magnetic properties of Kumano Basin sediments provide insights into the interplay between diagenetic, climatic, and tectonic processes that controlled the sedimentary evolution of this forearc basin. [ABSTRACT FROM AUTHOR]

The Kuroshio Current (KC) is the biggest western boundary current in the northwest Pacific Ocean and plays an essential role in the Cenozoic climate evolution and ocean circulation changes. Paleoceanography of the Shikoku Basin, located downstream of the KC region, is sensitive to the evolution of the KC. In this study, the Miocene hemipelagic sediment supply in the Shikoku Basin has been investigated on sediments from lithologic Unit III of IODP Site C0011 using a combination of rock magnetism, Sr isotope composition, grain size analysis, and calcareous nannofossil study. Integrated results reveal that multidomain (MD) (titano-) magnetite concentration increases in the upper part of Unit III since ~10–11 Ma with elevated 87Sr/86Sr values (0.712–0.714) and fining up sediment grain size. Magnetic parameters, Sr isotope composition, and grain size, as reliable indicators of sediment sources, have been used to discriminate the geological sources of the sediments and attribute the increase in MD (titano-) magnetite concentration to the increasing detrital input from the East China Sea (ECS), which is rich in fine-grained particles and coarse-grained magnetite and have high 87Sr/86Sr ratio (0.712–0.727). Furthermore, the intensified western boundary current later became known as the KC is interpreted as a plausible reason for increasing fine-grained flux from the ECS. Our study provides a much earlier record of the KC at ~10–11 Ma, giving new insight into understanding the Cenozoic ocean circulation changes and climate evolution in the northwest Pacific Ocean. • The Miocene hemipelagic sediment supply of the Shikoku Basin was comprehensively studied on sediments from Site C0011. • Sediments from the East China Sea are rich in fine particles and multidomain magnetite and have high 87Sr/86Sr (0.712–0.727). • Sediments from Japan are rich in coarse-grained particles and fine-grained magnetite and have low 87Sr/86Sr (0.709–0.712). • The Miocene Kuroshio Current evolution was identified by the hemipelagic sedimentary provenance from the Shikoku Basin. [ABSTRACT FROM AUTHOR]

In recent years, Beijing has been shown to suffer one of the most serious air pollution problems of any major world city. The concentrations of particulate matter (PM) pollutants, PM 2.5–10 and PM 2.5 , are commonly used as air pollution indexes. We conducted a detailed environmental magnetism study to investigate possible sources of air pollution in Beijing, China, using 283 pairs of the PM 2.5 and PM 2.5–10 samples collected daily from July 2010 to June 2011. Rock magnetic measurements, including magnetic susceptibility, anhysteretic remanent magnetization, isothermal remanent magnetization, saturation isothermal remanent magnetization, hysteresis loops, first-order reversal curves (FORCs), and thermomagnetism, indicate that the main magnetic mineral is low-coercivity pseudo-single domain (PSD) magnetite. Scanning electron microscope (SEM) observations and energy dispersive X-ray spectroscopy (EDS) analyses on the PM indicate that the major magnetic phase is coarse-grained magnetite, which is most likely from automobile exhausts and braking system debris. Magnetic parameters of PM 2.5 and PM 2.5–10 show significant seasonal patterns that may be attributed to domestic heating enhancing magnetization of the PM during late autumn to early spring. Power spectral analyses and box–whisker plots indicate that the magnetic parameters have strong weekly variations that may be due to traffic emissions. These results indicate that magnetic parameters can be used as efficient proxies for monitoring Beijing's air pollution, and that the atmospheric environment may be improved by controlling vehicle emissions. [ABSTRACT FROM AUTHOR]

In contrast with its decrease in western China deserts, the dust storm event in eastern China, Korea, and Japan shows an increase in frequency. Although the drylands in northeastern China have been recognized as an important dust source, the relative contributions of dust transport from the drylands and deserts are inconclusive, thus the quantification of dust storm sources in downwind area remains a challenge. We measured the 14 C and 13 C contents in carbonates of dust samples from six sites in China, which were collected for the duration of dust storm events in drylands, deserts, and urban areas. The δ 13 C of the dryland dust samples considerably varied in a range of − 9.7 to − 5.0‰, which partly overlapped the desert dust carbonate δ 13 C ranges. The 14 C content of the dryland dust carbonates showed a narrow range of 60.9 ± 4.0 (as an average and 1 SD of five samples) percent modern carbon (pMC), indicating the enrichment of modern carbonate. Dust samples in desert regions contained relatively aged carbonates with the depleting 14 C showing of 28.8 ± 3.3 pMC. After the long-range transport of the western China desert dust plume, the carbonates collected at the southern China remained the depletion of 14 C (33.5 ± 5.3 pMC) as in the desert regions. On the other hand, the samples of dust storm events at the urban areas of eastern China showed an enrichment of 14 C contents (46.2 ± 5.0 pMC, n = 7), which might be explained by the stronger contribution of modern-carbonate-rich dryland dust. [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]

Boronizing treatment has been considered as a promising strategy to enhance the surface hardness, self-lubrication and wear resistance of high entropy alloy (HEA), endowing the advancements of HEA in engineering applications. However, the anti-friction, anti-wear and corrosion resistance properties of the boronized HEA in sulfuric acid and seawater environments remain unclear. Here, the self-lubrication and corrosion resistance of the boronized CoCrFeNiMn HEA in these corrosive media were studied to assess the applicable environments. Firstly, a boronized layer with thickness of approximately 25 μm on the CoCrFeNiMn HEA surface was fabricated using the powder-pack boronizing treatment. Tribological assessments demonstrated exceptional self-lubricating properties of boronized HEA in various liquid conditions, with over 30 % reduced friction coefficients and over 80 % decreased wear rates. XPS analysis confirmed the formation of a boron-containing tribofilm, enhancing self-lubrication and reducing friction and wear in liquid environments. However, electrochemical tests indicated that the corrosion resistance of the boronized HEA was significantly affected by the liquid medium. The impedance value (|Z|) of boronized HEA decreased to 4.6 % of that of the original HEA in 3.5 wt% NaCl solution, revealing poor corrosion resistance. Conversely, an enhancement of corrosion resistance was observed in 0.05 M H 2 SO 4 solutions with the increase of the |Z| value by 8 times. Therefore, for applications requiring service safety, boronizing HEAs are more suitable for acidic environments, but not in seawater environments, offering valuable insights for the industrial application of CoCrFeNiMn HEA in reducing friction and wear. • The COF of boronized HEA is over 30 % lower than original HEA in liquid conditions. • The tribofilm (composed of H 3 BO 3 and B 2 O 3) significantly reduce friction and wear. • Boronized HEAs are more suitable for acidic environments, but not in seawater. [ABSTRACT FROM AUTHOR]

The chaotic behavior of the Solar System prevents the prediction of the precise evolution of the planetary secular frequencies. Here we use four cyclostratigraphic sequences, ∼259 Ma Wujiaping Formation, ∼455 Ma Pingliang Formation, ∼655 Ma Datangpo Formation and ∼2,465 Ma Dales Gorge Member, and Bayesian inversion to provide powerful geological constraints to this problem. The inversion provides constraining estimates for the Solar System fundamental secular frequencies g1, g2, g3, g4, and g5, and the Earth's precession rate k from 105.26 ± 2.68 (2σ) arcseconds/year at ∼2,465 Ma to 55.86 ± 2.60 (2σ) arcseconds/year at ∼259 Ma. Stochastic monotone interpolation enables the reconstruction of Earth‐Moon distance from 2.5 billion years to the present. Calculation of tidal dissipation supports the ocean model before 1.4 Ga, but is outside the error range after ∼1.8 Ga, suggesting lower tidal dissipation in the early Proterozoic Eon, and a possible high value in the early Paleozoic. Plain Language Summary: The chaotic history of the Solar System imposes unknown uncertainties on the fundamental secular frequencies of the planets over most of geologic time. This is complicated by a lack of knowledge about the evolution of Earth‐Moon distance, Earth's length of day and tidal dissipation. Geological evidence provides powerful constraints on all of these parameters. To shed light on the parameters, here we carry out Bayesian inversion of fundamental secular frequencies and Earth precession rate on four cyclostratigraphic sequences, and stochastic monotone interpolation to reconstruct Earth‐Moon distance from 2.5 billion years ago to present. From these results we estimate the Earth's tidal dissipation variation, which we compare with theoretical models. Our results provide critical geological constraints for paleotidal simulation, and shine a light on the unique potential of cyclostratigraphy to constrain Earth‐Moon system history across geologic time. Key Points: We obtain new estimates of Earth‐Moon and Solar System dynamical parameters from cyclostratigraphy at four ages from ∼2.5 Ga to ∼259 MaWe interpolate Earth‐Moon distances inferred from the cyclostratigraphy to reconstruct a continuous history from ∼2.5 Ga to the presentWe estimate Earth's tidal dissipation variations from ∼2.5 Ga to the present [ABSTRACT FROM AUTHOR]

The Ocean Drilling Program (ODP) Leg 184 recovered a continuous sedimentary sequence since Miocene at Site 1148 in the northern South China Sea (SCS), which provided a unique record for better understanding the tectonic, environmental and climatic evolution of the SCS. In this study, we report a detailed paleomagnetic study on 881 discrete samples from the upper 460 m cores of Hole 1148A through stepwise alternating field demagnetization (AF) or thermal demagnetization (TD). Rock magnetic results from isothermal remanent magnetization (IRM) acquisition, temperature dependence magnetic susceptibility (κ-T) and hysteresis loop parameters of representative samples indicate that the main magnetic mineral is low coercivity pseudo-single domain magnetite. The characteristic remanent magnetization (ChRM) with moderate downward or upward inclinations was identified after removing a low-stability drilling-induced remanence with steep downward inclinations. A new 23 Myr magnetostratigraphic time framework was established by correlating the magnetic polarity sequence to the Geomagnetic Polarity Time Scale 2012 (GPTS 2012; Ogg, 2012 ) in combination with biostratigraphic data. The mean sediment accumulation rates for lithostratigraphic Units V and IV, Unit III and lower Unit II, upper Unit II, Unit IB and Unit IA are calculated as ∼20.8 m/Myr, ∼15–17 m/Myr, 24.18 m/Myr, 17.07 m/Myr and 49.01 m/Myr, respectively. [ABSTRACT FROM AUTHOR]

The Late Paleozoic Ice Age (LPIA) was the longest-lasting icehouse in the Phanerozoic. Previous studies indicated a climate warming interval in the earliest Permian—an apex of the LPIA. To better understand hydroclimatic changes and carbon cycling within this time interval, we conducted a series of high-resolution geochemical and rock magnetic analyses, including magnetic measurements (e.g., magnetic susceptibility, anhysteretic remanent magnetization, hysteresis loops, temperature-dependent susceptibility), ratio of iron to potassium (Fe/K), and carbonate carbon isotope (δ13C carb) from a deep-marine section in South China. Calibrated to the published astronomical time scale, a negative δ13C carb excursion (−1‰) was identified during 298.4–297.9 Ma, and it was time-equivalent with the warming interval, recognized by a decrease in conodont apatite oxygen isotopes in South China, low-latitude sea-level transgression, and high-latitude deglaciation. The negative δ13C carb excursion also coincided with a magmatic pulse of the Skagerrak-Centered Large Igneous Province (LIP), indicating that the perturbation in carbon cycling is likely associated with the release of volcanic CO 2. Furthermore, cyclostratigraphic analysis on multiple paleoclimatic proxies, including ferrimagnetic susceptibility, gamma-ray, and Fe/K, suggested that the negative excursion of δ13C carb also overlapped with the maximum of the eccentricity cycle. It implied that orbital configurations may amplify the feedback of the LIP, causing this short-term warming interval. • High-resolution carbon isotope and magnetic record in the earliest Permian. • Transient climate warming interval is documented in the earliest Permian. • LIP and orbital forcing were critical drivers of the earliest Permian warming. [ABSTRACT FROM AUTHOR]

Magnetic enhancement of Chinese loess‐paleosol sequences has been used extensively as a proxy for East Asian summer monsoon variations. However, the pedogenic magnetic particles contributing to this magnetic enhancement are difficult to extract, so it is not clear how they formed. In this study, we reveal pedogenic magnetite and hematite using electron microscopy, synchrotron radiation X‐ray diffraction, and rock magnetic methods. First‐order reversal curves indicate that superparamagnetic/single domain/vortex state magnetic properties dominated both loess and paleosol samples. Samples of muscovite and chlorite, which are paramagnetic, have weak spontaneous magnetization. The 1‐ to 10‐μm‐sized fraction of host silicatesis responsible for most of the magnetic enhancement of paleosols. In the paleosol fraction, we found weathered phyllosilicates (muscovite/chlorite), including many elongated submicron to a few microns authigenic magnetite and hematite particles between layers; however, few such interlayer particles were found in phyllosilicates of the loess fraction. The concentration of magnetite/hematite particles within paleosol muscovite/chlorite grains and in aggregates of phyllosilicate fragments is much higher than that of the submicron iron oxides found on silicate surfaces. Interlayer magnetite particles are dominantly prism‐shaped with aspect ratios >~4. The authigenic magnetite must be mainly responsible for the spontaneous magnetization of the muscovites and chlorites and the paleosol magnetic properties. The protective silicates account for the low extraction efficiency and also the near absence of surface oxidation of pedogenic magnetite. Based on our results, we suggest that magnetite/hematite in weathered phyllosilicates contribute significantly to the magnetic enhancement of mature paleosols. Key Points: Hundreds of nanometer‐micron‐sized authigenic magnetite/hematite particles are highly concentrated in paleosol muscovite/chlorite grainsThe authigenic iron oxides are mainly responsible for the weak spontaneous magnetization of weathered muscovite and chlorite grainsElongated authigenic magnetites account for the dominant single domain/vortex state magnetic property and magnetic enhancement in paleosols [ABSTRACT FROM AUTHOR]

A continuous terrestrial succession was recovered from the Songke‐2 (SK‐2) borehole in the Songliao Basin, Northeastern China. This borehole provides a unique material for further research on the continental paleoclimate during Cretaceous greenhouse period, following a series of achievements of the Songke‐1 (SK‐1) core. In this study, thorium (Th) logging data were chosen as a paleoclimate proxy to conduct a detailed cyclostratigraphic analysis. The Th series varies quasi‐periodically; power spectra and evolutionary fast Fourier transformation (FFT) analysis reveal significant cycles in the Quantou (K2q), Qingshankou (K2qn), Yaojia (Ky and Nenjiang (K2n) formations. The ratio of cycle wavelengths in these stratigraphic units is approximately 20:5:2:1, corresponding to long orbital eccentricity (405 kyr), short orbital eccentricity (100 kyr), obliquity (37 kyr), and precession cycles (22.5 kyr and 18.4 kyr). The durations of the K2n, K2y, K2qn and K2q are estimated as 6.97, 1.83, 5.30 and 4.52 Myr, respectively, based on the constructed ∼18.62 Myr "floating" astronomical time scale (ATS). Comparison of the durations between the SK‐1 s and SK‐2 boreholes exhibits a slight difference of 0.06 Myr and 0.459 Myr for K2qn and K2y. Nevertheless, our ATS of K2n supports the chronostratigraphic frame constructed by the CA‐ID‐TIMS data of the SK‐1s borehole. This new "floating" ATS provides precise numerical ages for stratigraphic boundaries, biozones and geological events in the Songliao Basin, and can serve as a basis for correlation of strata and events between marine and terrestrial systems. [ABSTRACT FROM AUTHOR]

The article focuses on the Upper Ordovician (Sandbian-Katian) Pagoda and Linhsiang formations in the Yichang Area of South China. It reports that Sandbian-Katian formations have been investigated for its biostratigraphic correlation. The formations were measured using three proxy series of time series analysis of cyclostratigraphy, magnetic susceptibility (MS) and natural gamma-ray intensity (GR).

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 anaerobic oxidation of methane, a key geochemical process that is involved in the cycling of sulfate and iron (oxyhydr)oxides in marine sediments, results in the formation of iron sulfides. Although ferrimagnetic iron sulfides have been identified in seepage systems, the link between iron migration and sediment magnetic properties remains poorly understood. Here, we investigate two cores from the Sea of Marmara to evaluate biogeochemical iron cycling and iron sulfide mineralogy in gas hydrate-bearing sediments. Magnetic analyses indicate the presence of greigite and pyrrhotite in a core from a hydrate-rich site with a high hydrocarbon flux, which contrasts with a lack of these minerals in a core characterized by only mild seepage. This is supported by the results of rock magnetic and scanning electron microscope analyses of the sediments. The presence of authigenic greigite is critical for assessing local redox records and together with the occurrence of monoclinic pyrrhotite may suggest specific diagenetic processes in gas hydrate environments. Our analysis demonstrates the usefulness of these ferrimagnetic minerals, with a high saturation isothermal remanent magnetization to magnetic susceptibility ratio (SIRM/χ > 15 kAm−1) and a high index of hysteresis parameters (D JH > 0.2) indicative of magnetic mineralogy changes, for evaluating variability in the intensity of seepage fluxes and for estimating gas hydrate distributions. • Two sediment cores with a similar original terrigenous source have contrasting magnetic properties. • A reducing and strong flux environment caused iron-driven AOM and formation of authigenic magnetic minerals in the sediments. • Greigite and monoclinic pyrrhotite are identified as the major magnetic minerals formed in hydrate-bearing sediments. [ABSTRACT FROM AUTHOR]

Organic matter (OM) sequestration acts as a significant sink of the CO 2 in Earth's carbon cycle and is tightly associated with the climate and depositional environments. However, the dominant factors controlling OM burial in different depositional settings and the orbitally forced variations in the lacustrine OM accumulation remain poorly constrained. Here, we investigate the depositional environment of the Lucaogou Formation in southern Junggar Basin, northwestern China and further decipher the astronomically forced OM accumulation in different depositional environments. Sedimentological and cyclostratigraphic studies show that both shallow lake and semi-deep to deep lake deposits recorded significant Milankovitch signals among of which ∼405 kyr, ∼91 kyr, 34.5–37.4 kyr, and 17.3–22.8 kyr are interpreted to be long eccentricity, short eccentricity, obliquity, and precession cycles, respectively. A linkage among the lithofacies, natural gamma ray (NGR), and total organic carbon (TOC) content suggests that the depositional environment and OM accumulation were in pace with the hydrological cycle and lake-level changes, in response to the astronomically forced changes in the ice volume and monsoonal intensity. In the semi-deep to deep lake, TOC content tightly tracks the lithofacies and shows an in-phase relationship with NGR. However, this phase relationship has changed with sedimentary facies. The gypsiferous shale deposited in the restricted environment during lowstand intervals has higher TOC content than highstand dolomitic mudstone, demonstrating an anti-phase relationship with NGR data. Our study indicates that the OM sequestration is a dynamically cumulative process of supply and degradation. The different responses of the OM sequestration to the climate change in different environments suggest that detailed sedimentological studies are essential for the cyclostratigraphic analysis. • A deep-time example for the OM burial in the continental basins was provided. • OM accumulation was orbitally forced in the Lucaogou Formation. • Dynamics of insolation-induced OM accumulation changes with sedimentary environments. [ABSTRACT FROM AUTHOR]

A high-precision time framework is critical for improving our understanding of three major events: the Late Ordovician mass extinction, the Hirnantian glaciation, and the Hirnantian isotopic carbon excursion (HICE). In the present study, we conducted detailed cyclostratigraphic analysis of a high-resolution (1–2-cm intervals) anhysteretic remanent magnetization series obtained from the Wanhe section in South China, covering the lower Katian through Hirnantian. Power spectra and derived average spectral misfit results show that the section records the ensemble of Milankovitch cycles with 405-kyr (long-eccentricity), 93–125-kyr (short-eccentricity), 33.8-kyr (main obliquity), and 17–22-kyr (precession) periods. The obliquity period of 33.8 ± 0.46 kyr indicates a precession constant k of 57.19 ± 0.53 arcsec/yr, a length of day of 22.37 ± 0.12 h, and an Earth–Moon distance of 375,330 ± 722 km (vs. 384,000 km today) during the Late Ordovician (445 Ma). The ratios of obliquity band power to total power reveal periodicities of 1.32 Myr for the s 4 – s 3 term and 173.4 kyr for the s 3 – s 6 term. Aided by the highly fluctuating magnetic susceptibility (MS), we recognized a series of 1.32-Myr obliquity-forced glacio-eustatic cycles with three intervals of sea-level rise and climate warming trend characterized by high MS values and two episodes of sea-level fall and climate cooling trend before the Hirnantian. The 405-kyr and subsequent 33.8-kyr calibrations produce an ~7.36-Myr floating astronomical time scale (FATS) for the studied succession, indicating that the estimated durations for the Hirnantian Stage, the worldwide Hirnantian glaciation, and the first and second phases of the Late Ordovician mass extinction were ~1225 kyr, ~830 kyr, ~440 kyr, and ~540 kyr, respectively. This work provides a reliable high-resolution time framework for further investigation of the major geological events occurred in the Late Ordovician, and improves our knowledge of Solar System behaviour and Earth–Moon history during that period. • An ~7.36 Myr ATS was constructed for the early Katian through Hirnantian. • The durations of Hirnantian Stage, glaciation and mass extinction were estimated. • Earth–Moon evolution was constrained for the Late Ordovician. • Obliquity forcing controlled the Late Ordovician glacio-eustasy. [ABSTRACT FROM AUTHOR]

The Cambrian is the first period of the Phanerozoic during which numerous major geological and biological events occurred. Understanding these events requires a high-resolution time scale. The Luoyixi section in Guzhang (Hunan Province, China) is the global stratotype section and point (GSSP) for the Guzhangian Stage. Here, magnetic susceptibility and δ13C data were used to conduct cyclostratigraphic analyses covering the upper Drumian through lower Guzhangian stages. The results of the power spectral analyses and average spectral misfit analyses indicate that the 25–25.53 m, 6.25–6.91 m, 1.90–2.03 m, and 1.08–1.19 m sedimentary cycles may represent long-eccentricity, short-eccentricity, obliquity and precession cycles, respectively. A ~1400 kyr floating astronomical time scale was constructed using the stable 405-kyr eccentricity cycles to calibrate the agnostoid trilobite zones. The obtained fundamental obliquity period (30.7 ± 0.7 kyr) implies 370,180 ± 1220 km (vs. 384,000 km for present day) for the Earth–Moon distance and 21.58 ± 0.18 h (vs. 23.93 h for present day) for the length of day during the middle Cambrian (500 Ma). • Reliable Milankovitch cycles were identified in the Middle Cambrian marine strata. • An ~1400 kyr ATS was constructed for the Drumian–Guzhangian transition. • The durations of the two complete agnostoid trilobite biozones were estimated. • Deep-time evolution of the Earth–Moon system was reconstructed. [ABSTRACT FROM AUTHOR]