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

The sedimentary environment of the Upper Triassic in the southeastern Sichuan Basin is obviously controlled by Luzhou paleo-uplift (LPU). However, the influence of paleo-uplift on the sedimentary patterns of the initial stages of this period in the southeastern Sichuan Basin has not yet been clear, which has plagued oil and gas exploration and development. This study shows that there is a marine sedimentary sequence, which is considered to be the first member of Xujiahe Formation (T3X¹ ) in the southeastern Sichuan Basin. The development of LPU resulted in the sedimentary differences between the eastern and western Sichuan Basin recording T3X¹ and controlled the regional sedimentary pattern. The western part is dominated by marine sediments, but the eastern paleo-uplift area is dominated by continental sedimentation in the early stage of T3X¹, and it begins to transform into a marine sedimentary environment consistent with the whole basin in the late stage of the period recorded by the Xujiahe Formation. The evidences are as follows: (1) time series: based on the cyclostratigraphy analysis of Xindianzi section and Well D2, in the southeastern Sichuan Basin, the period of sedimentation of the Xujiahe Formation is about 5.9 Ma, which is basically consistent with the Qilixia section, eastern Sichuan basin, where the Xujiahe Formation is widely considered to be relatively complete; (2) distribution and evolution of palaeobiology: based on analysis of abundance evolution of major spore-pollen, many land plant fossils are preserved in the lower part of T3X¹, indicates the sedimentary environment of continental facies. In the upper part of T3X¹, the fossil of terrestrial plants decreased, while the fossil of marine and tidal environment appeared, this means that it was affected by the sea water in the late stages of T3X¹ ; (3) geochemistry: calculate the salinity of water from element indicates that the uplift area is continental sedimentary environment in the early stage of T3X¹, while the central and western areas of the basin are marine sedimentary environment. Until the late stage of T3X¹, the southeast of the basin gradually turns into marine sedimentary environment, consisting with the whole basin; (4) types of kerogen: type III kerogen representing continental facies was developed in the early stage of T3X¹ in the uplift area, and type II kerogen, representing marine facies, was developed in the late stage; while type II kerogen was developed in the central and western regions of the basin as a whole in T3X¹ . This study is of great significance for understanding of both stratigraphic division and sedimentary evolution providing theoretical support for the exploration and development of oil and gas. [ABSTRACT FROM AUTHOR]

Cyclostratigraphy is widely applied in establishing high-precision sequence stratigraphic frameworks and astronomical time scales, making it an important field in the quantitative study of sedimentology. A detailed cyclostratigraphic analysis of natural gamma-ray logging data from the upper cretaceous Sifangtai formation in Qian’an area of Songliao basin was conducted in this paper. Spectral analysis results show that Sifangtai formation exhibits sedimentary cycles of 40.2, 10.6-13.1, 3.6-3.8, and 1.79-2.4 m. The ratio of these cycles is approximately the same as the ratio of Late Cretaceous astronomical orbital periods, specifically 20∶5∶2∶1, corresponding to sedimentary cycle periods of 405 ka long eccentricity, about 106 ka short eccentricity, about 38 ka obliquity, and about 21 ka precession cycles. The COCO statistical test results indicate that the sedimentation rate of the Sifangtai formation is about 9.78 cm/ka, which aligns with these astronomical periods. Filtering the sedimentary cycle corresponding to the 405 kyr long eccentricity period, eight sedimentary cycles were identified. Using the 405 kyr long eccentricity period, an astronomical tuning was performed on the GR data sequence, establishing a floating astronomical time scale. This provides a sedimentary duration of 3.23 million years for the Sifangtai formation. By referencing the chronological stratigraphic framework of the Mingshui formation and the Sifangtai formation in the Songke-1 well in the northern basin, the sedimentary duration of the uranium-bearing sand body in the study area was determined. The results show that the optimal sedimentation rate variations of the Sifangtai formation in the study area are consistent with the lithological changes, and can be divided into two high-value zones: the top and the bottom. The bottom high-value zone corresponds to the medium to coarse sandstone section of the lowstand systems tract at the early stage of the Sifangtai formation deposition, which is the main uranium mineralized sandstone layer in the Qian’an area. The top high-value zone corresponds to the regressive systems tract at the end of the Sifangtai formation, which is in conformable contact with the Mingshui formation above it. The thickness of the sandstone revealed by drilling in this section is relatively thin and its distribution is relatively limited. In addition, the sedimentation rate of the lower red mudstone and grayish-white medium to coarse sandstone section of the Sifangtai formation is significantly lower than that of the upper gray mudstone section. This indicates that during this period, under the background of a dry and hot climate, the lake basin shrank, the braided river delta prograded, and the tectonic conditions were stable. The basin accommodation space grew slowly, characterized by overcompensated infilling, and the sedimentary system was stable, favoring the formation of large-scale sand-mud combination structures. This provides favorable strata for the formation of sandstone-type uranium deposits. Uranium mineralization in sandstone in the Qian’an area develops in the lower part of the Sifangtai formation, with the sand body deposition duration estimated to be ((75.36-76.09)±0.40) Ma. The study results indicate that cyclostratigraphic analysis can be effectively applied to the exploration of sandstone-type uranium deposits. It can accurately determine the deposition period of uranium-bearing sandstone layers, making it an effective method for regional target layer identification, comparison, and exploration target area delineation.

The Earth's rotation has been decelerating throughout its history due to tidal dissipation, but the variation of the rate of this deceleration through time has not been established. We present a detailed analysis of eight geological datasets to constrain the Earth's rotational history from 650 to 240 Mya. The results allow us to test physical tidal models and point to a staircase pattern in the Earth's deceleration from 650 to 280 Mya. During this time interval, the Earth-Moon distance increased by approximately 20,000 km and the length of day increased by approximately 2.2 h. Specifically, there are two intervals with high Earth rotation deceleration, 650 to 500 Mya and 350 to 280 Mya, separated by an interval of stalled deceleration from 500 to 350 Mya. The interval with stalled deceleration is attributed mainly to reduced tidal dissipation due to the continent-ocean configuration at the time, not to changes in Earth's dynamical ellipticity from continental assembly or glaciation. Modeling indicates that, except for the very recent time, tidal dissipation is the main driver for decelerating Earth rotation. One potential implication of our findings is that the Earth's tidal dissipation, along with Earth's rotation deceleration, may play a role in the evolving Earth. [ABSTRACT FROM AUTHOR]

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

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

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

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

Studies of Cenozoic lacustrine cyclostratigraphy in northeastern Tibet have been successful in reconstructing the history of precipitation and aridification at astronomical (Milankovitch) time scales. However, the phase relationships between Milankovitch forcing mechanisms and hydrologic changes are ambiguous because of challenges in interpreting climate proxies and dating continental successions. We present an analysis of Miocene red and green mudstone rhythmites in two basins (Jiuxi and Guide, NE Tibet) using a climate proxy based on lithologic color. Time-series analysis of the color proxy indicated a dominance of 405 k.y. cycles, from which we constructed an orbital eccentricity metronome astrochronology from 18 Ma to 10 Ma. Periods of lake expansion and contraction are characterized by the green and red mudstones, respectively, and correspond to orbital eccentricity minima and maxima, respectively. We interpreted the antiphase relationship between orbital eccentricity and hydrologic evolution using a net precipitation model, with low precipitation/evaporation ratio being due to excessively high evaporation during times of high orbital eccentricity, and vice versa. High orbital eccentricity scenarios with strong seasonality and insolation extremes are analogous to anthropogenic global warming, and our results provide insights into a future of Central Asian intensified aridification, following the "drygets-drier" global warming projections and regionally high aridity sensitivity. [ABSTRACT FROM AUTHOR]

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

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

Recent evidence for astronomical-induced cycles in banded iron formations (BIFs) hints at the intriguing possibility of developing astrochronological, i.e. precise time-stratigraphic, frameworks for the earliest Proterozoic as also reconstructed for parts of the Mesozoic and Paleozoic. The Kuruman Iron Formation (IF) (Griqualand West Basin, South Africa) and Dales Gorge Member of the Brockman IF (Hamersley Basin, Western Australia) are of special interest in this regard, given their inferred temporal overlap at ca. 2.47 Ga and similar long-period orbital eccentricity imprint. This suggests that these two BIFs may be correlated on the basis of their large-scale cycle patterns and using additional radio-isotopic age constraints. To examine the possibility of establishing such a framework, we generated and analysed several high-resolution proxy records from both drill-core and outcrop, combined with high-precision U-Pb dating of zircon from interbedded shale horizons. Time-series analysis of these records yields a variety of spectral peaks, of which a prominent ~5 m and ~16 m cycle can be linked to the basic stratigraphic alternations and bundling as observed in the field. New and revised 207Pb/206Pb ages calculated from the U-Pb data of the Dales Gorge Member and Kuruman IF, respectively, indicate a comparable average sedimentation rate of 10 to 12 m/Myr for both units. Based on this depositional rate, we attribute the ~5 m cycle to the long (~405 kyr) orbital eccentricity cycle. More tentatively, we interpret the ~16 m cycle as the very long (presently ~2.4-Myr) eccentricity cycle, having a reduced period of ~1.3 Myr due to chaotic behaviour in the solar system. Other identified cycles (~560 kyr, ~700 kyr and ~1.8 Myr) can be explained in terms of weaker orbital eccentricity components and/or as harmonics and combination tones of these cycles resulting from nonlinear responses. An initial attempt to establish cyclostratigraphic correlations between the Kuruman IF and Dales Gorge Member solely based on their characteristic cycle patterns proved unsuccessful, which may be due to a difference in the recording of the astronomical signal between different depositional environments. Next, we used the zircon ages to first constrain correlations at the scale of the ~16 m cycle, followed by a correlation of the basic ~5 m cycles. The resultant framework remains problematic and debatable at the individual ~405 kyr cycle-level, but provides a starting point for future studies. Particularly, our findings highlight the need for further investigations into how Milankovitch forcing influenced BIF sedimentation and paleoenvironmental conditions at a time when the Earth and solar system behaved fundamentally different from today. [ABSTRACT FROM AUTHOR]

The accurate determination of geological age is a key to understanding the history and process of paleolake evolution and oil and gas exploration in continental lake basin. However, improving the accuracy of geological age has always been a difficult scientific problem. A 609-m-thick, continuous lacustrine mudstone and sandstone succession in Chezhen Sag (eastern China) provides an ideal middle Eocene sedimentary record for establishing a high-resolution stratigraphic chronology framework. Based on spectrum analysis and sliding window spectrum analysis of the natural gamma (GR) logging data of well Che 271 (C271) in Chezhen Sag, the periods of 405 kyr and 40.1 kyr were filtered by a Gaussian bandpass filter, and a "flngting" astrochronological time scale (ATS) was established. The total number of 405 kyr eccentricity cycles were 13.6 and 40.1 kyr obliquity cycles were 138 which recorded from the upper member 4 (Es4U) to the member 3 (Es3) of the Eocene Shahejie Formation, and the depositional duration was 5.53 Myr. Correlation Coefficient (COCO) analysis and evolutionary Correlation Coefficient (eCoCo) analysis found that the optimal sedimentary rate of different strata. Sedimentary noise simulation revealed the history of paleolake water changes in the Middle Eocene in the Chezhen Sag, according to which four sequences are divided. The study shows that the lake level change of Chezhen Sag in the middle Eocene shows prominent 1.2 Myr cycles and an antiphase well-coupled relationship with obliquity modulation. Finally, we propose a model to explain the relationship between the orbital cycle and lake level change in the continental lake basin. When the obliquity of the earth increases, the middle and high latitudes of the earth will be closer to the sun, the direct sunlight will be higher, and the meridional sunshine will increase, thus accelerating the evaporation process of lake basin water. When the seasonal changes are obvious (maximum period of 1.2 Myr ultra-long obliquity), this effect is more significant. The relative lake level change based on the restoration of high-precision ATS has significant scientific and economic value for understanding the vertical evolution of continental stratigraphic sequences and the formation and distribution of oil and gas resources. [ABSTRACT FROM AUTHOR]

The red clay of the Chinese Loess Plateau (CLP) is an important geological archive for understanding the variability in the late Neogene East Asian monsoon. The periodicity of the summer monsoon of the red clay on the eastern CLP is dominated by eccentricity cycles within the constraints of the palaeomagnetic chronological framework, whereas global climate change characteristics represented by the deep-sea oxygen isotope record at that time show a dominating obliquity cycle. Here, we analyzed the East Asian summer monsoon proxies from the Shilou red clay section with the cyclostratigraphy method. The results show that the summer monsoon variation was dominated by obliquity, the optimum deposition rate was 4.451 cm/kyr, and the floating age of the Shilou red clay section was ca. 1.7 Ma. The late Neogene East Asian summer monsoon inferred from the eastern CLP was thus paced by the obliquity cycle, which is consistent with global change.

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]

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

[Objective] This study aims to conduct an in-depth investigation into the large set of rhythmicallycharacteristic lacustrine fine-grained sedimentary rocks rich in carbonate materials and organic matter developed in the Dongying Sag area of the Bohai Bay Basin in eastern China, exploring their genetic mechanisms as well as characteristics of paleoclimate and paleoenvironment changes. [Methods] Based on core and thin-section observations, we classified the lithofacies according to sedimentary structural features and mineral component content. Considering the differences in sedimentary environment and deposition rate, the target interval was divided into four units. The Multi-Taper Method (MTM) was applied to perform segmented spectral analysis on the natural gamma (GR) logging curve from the upper Fourth member of the Shahejie Formation (Es4u) to the lower Third member (Es3l) in well Fanye 1 (FY1). [Results] Through macroscopic and microscopic sedimentary observations, we identified five types of fine-grained rocks in the Dongying Sag area: laminar argillaceous limestone, laminar calcareous mudstone, weakly laminar calcareous mudstone, lenticular argillaceous limestone and massive mudstone. Spectral analysis results revealed that all four units recorded Milankovitch cycles, including periods of 125 kyr, 38.7 kyr, and 18.7 kyr. Based on volcanic ash dating data, we established a "floating" astronomical timescale with a precision of 38.7 kyr and determined that the total duration of fine-grained sedimentary deposition from the upper Es4 to the lower Es3 in the Dongying Sag was 5.3 Myr. Further analysis indicated a good correspondence between the 18.7 kyr precession cycle and changes in carbonate content, suggesting a significant influence of Earth's orbital parameters on the deposition of carbonate-bearing fine-grained sedimentary rocks. [Conclusions] Utilizing the theory of cyclostratigraphy, this study revealed characteristics of paleoclimate and paleoenvironment changes in lacustrine sediments from the perspective of astronomical cycles controlling sedimentation. Our analysis showed that Earth's orbital parameters, particularly the 18.7 kyr precession cycle and the 125 kyr eccentricity cycle, jointly drove climate changes, which in turn controlled the deposition of carbonate-bearing fine-grained sedimentary rocks. Specifically, at maxima of precession or minima of eccentricity, increased sunlight and warmer lake water temperatures favored the crystallization of calcite and the deposition of limestone. Conversely, at minima of precession or maxima of eccentricity, decreased sunlight and cooler lake water temperatures resulted in fine-grained material being predominantly derived from terrestrial sources, with mudstone deposition dominating. This research has important scientific and guiding implications for unconventional oil and gas exploration and development. [ABSTRACT FROM AUTHOR]

The late Asbian appears to mark the initial, well‐documented, onset of far‐field glacio‐eustatic changes in equatorial Mississippian strata. This work unravels the nature of cyclicity in upper Asbian shallow marine carbonates, using a combination of petrographic study, rock magnetic proxies and astrochronological testing on samples from the Trowbarrow section, NW England. Rock magnetic data express the content of two types of siliciclastic sources; a marine‐delivered magnetite‐dominated source, and an eolian‐delivered, hematite‐dominated source. The eolian‐sourced material generally peaked during regressive and low‐stand parts of the carbonate rhythms. Astrochronologic testing methods based around the average spectral misfit and TimeOpt methodology show the magnetite abundance proxies are principally carrying the astronomically forced signal. Two likely sedimentation rate models are derived from the five better magnetic proxies using evolutive methods. In addition, a set of three likely major hiatus levels are inferred in the sedimentation rate models, based on testing possible major hiatus scenarios with TimeOpt methods, using eccentricity modulation. From these, using the three best proxies, an average astrochronologic duration for the Trowbarrow section suggests a late Asbian duration of 1976 ± 86 kyr (1σ), and a basal late Asbian age of 334.48 ± 0.35 Ma (2σ). Coupled atmosphere‐ocean models for the late Paleozoic, suggest that lows in short eccentricity correspond to glacials, when inferred delivery of siliciclastic sediment to the carbonate ramp is generally at a maximum. The glacial and lower sea‐level intervals also coincide with maximum delivery of eolian siliciclastics, likely linked to increased aridity and less vegetation cover on adjacent and distal parts of Laurentia. Plain Language Summary: Around 332–333 million years ago changes in sea‐level driven by changes in polar ice volume were an important control on the sedimentation patterns through time in carbonates from low paleolatitudes. Understanding the pacing of these changes has implications for timescales and paleoceanographic processes. These cyclical changes in carbonate lithology are related to changes in magnetic properties within the late Asbian (late Visean) section at Trowbarrow in NW England. The magnetic changes principally express differences in the small content of silica‐based clastics, but also reflect changing Fe‐oxide mineralogy between times of hematite‐rich and magnetite‐rich clastic input. The changes are responding to differences in eolian delivery and marine dispersal of the clastics. Eolian delivery of clastics was at its peak near sea‐level lowstands, when nearby terrestrial systems were the most arid and supplying the most dust. Statistical assessments show that the magnetite abundance signal principally expresses changes in astronomical eccentricity. Primarily using the expected eccentricity pacing, two age models are constructed, which includes three levels of detectable hiatus in the section. Using these two age models and the three best magnetic proxies, the average late Asbian duration is 1976 ± 86 kyr, with the base of the late Asbian at 334.48 ± 0.35 Ma. Key Points: Rock magnetic properties show the included siliciclastics are from hematite‐rich eolian dust and marine‐dispersed sourcesThe magnetite mineral abundance proxies principally carry the primary eccentricity‐driven astronomical signalAn astrochronology for the late Asbian indicates its duration is 1976 ± 86 kyr [ABSTRACT FROM AUTHOR]

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

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

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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]

The RO drilling is located in the Ivorian Onshore Basin in the Aboisso area. To find a suitable area to meet the potable water needs of Abidjan city, litho-granulometric and log analyzes were carried out on forty-three (43) samples, to understand the sedimentary cyclicities in the establishment of hydraulic reservoirs (aquifers) along the borehole. The lithological results reveal six (6) lithologies which are among others sandy gravels, gravelly sands, kaolins, quartz sands, sandy-muddy gravel, and silty-clayey sand, which alternate all along drilling. These different alternations allowed the establishment of 42 lithological cycles, of which 35 were binary cycles, 6 ternary cycles, and a single quaternary cycle. The grain size results show that the sand fractions of these lithologies are coarse to very coarse, moderately graded to poorly graded, Platikurtic, with negative to positive asymmetries. Through these granulometric parameter arrangements, 23 cycles of grain size, 30 cycles of classification, 27 cycles of asymmetry, and 9 cycles of kurtosity were counted. The log signatures show 12 cylindrical shapes, 4 bell shapes, 3 jagged shapes, 3 egg shapes, and one funnel shape giving a total of 23 cycles. They indicate the existence of anastomosing and meandering fluvial systems. [ABSTRACT FROM AUTHOR]

Holostratigraphic research of continental-shelf deltas in graben basins needs to be further studied. Taking a typical foreign continental-shelf delta as an example, based on the classic sequence stratigraphic theory, combined with the seismic reflection termination relationship, the third-order sequence and system tract were identified and divided, and the sequence stratigraphic framework was established. Based on cyclostratigraphy, the Milankovitch cycles within the gamma-ray curve of the drilling were identified by wavelet transformation, spectral analysis and inverse Fourier transformation filtering, and the absolute astronomical time scale was established by combining the geological-time reference point. The holographic stratigraphic framework was established by integrating chronostratigraphy, lithostratigraphy, magnetic stratigraphy, sequence stratigraphy, cyclostratigraphy and seismic stratigraphy, and the methodology and suggestion for dating the sequence boundary of continental-shelf deltas in graben basins were proposed. The results show that Neogene strata can be divided into 5 third-order sequences and 15 individual system tracts. Taking 23. 03 Ma as the reference point, the absolute geological ages of the top boundary of CS1, CS2 and CS3 sequences are 13. 93, 9. 13 and 2. 13 Ma, respectively, and the absolute geological ages of their corresponding maximum flooding surface are 20. 03, 12. 13 and 6. 13 Ma, respectively. Aiming at the characteristics of progradation and lateral growth of continental-shelf deltas during the thermal depression period of graben basins, holographic stratigraphic research suggests that the geological age of the truncated top surface can be calculated by using the cyclostratigraphy of the drilling under the constraint of sequence framework in combination with magnetic stratigraphic dating and global sea level curve. If the outcome is basically consistent with the age of magnetic stratigraphy, the oblique sequence interface closest to the truncated top surface of the drilling may represent the true isochronous surface. [ABSTRACT FROM AUTHOR]

The Qiongdongnan Basin, located in the sea between Hainan Island and the Xisha Islands, is a faulted Cenozoic basin on the northern continental margin of the South China Sea. The Changchang Sag, situated in the eastern part of the central depressional zone in the deepwater area of the Qiongdongnan Basin, exhibits a near EW-striking morphology and represents an important potential target for oil/gas exploration. However, the age of the interface of the Lingshui Formation remains controversial, which hinders a comprehensive understanding of the tectonic evolution and hydrocarbon accumulation pattern in the Changchang Sag. This study focuses on well A, located in the depositional center of the Changchang Sag, and employs cyclostratigraphic analysis to identify cyclic signals of the Milankovitch cycles recorded in the sedimentary strata. Spectral analysis of natural gamma logging data from this well reveals the presence of 405 kyr long eccentricity cycles, 100 kyr short eccentricity cycles, 39.3 kyr obliquity cycles, and 20.58 kyr age precession cycles. By employing astronomical tuning, a "floating" astronomical time scale of the Lingshui Formation spanning 5.483 million years (Myr) is established. The top interface of the Oligocene in the International Geological Time Scale 2020 (GTS2020), with a geological age of 23.03 Ma, is used as the time anchor to establish a high-precision absolute astronomical age framework for the Lingshui Formation. The results indicate that the bottom interface of the first member of the Lingshui Formation is dated at 23.79 Ma, the bottom interface of the second member is dated at 25.08 Ma, and the bottom interface of the third member is dated at 28.51 Ma. Additionally, the average sedimentation rate during this period is estimated to be 9.261 cm/kyr. Furthermore, paleoclimate and paleoenvironmental reconstructions were carried out through quantitative analysis of spore and pollen assemblages, as well as foraminifera within the Lingshui Formation. These analyses suggest that the deposition of the Lingshui Formation occurred under warm and humid temperate climatic conditions. The results of paleoclimate proxy analysis and comparative fitting analysis of the astronomical time scale confirm that the climate evolution during this period was influenced by astronomical orbital forces, such as eccentricity and precession. [ABSTRACT FROM AUTHOR]

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

A significant shift in Earth's climate characterizes the Neogene, transitioning from a single‐ice‐sheet planet to the current bipolar configuration. This climate evolution is closely linked to changing ocean currents, but globally‐distributed continuous high‐resolution sedimentary records are needed to fully capture this interaction. The Ocean Drilling Program (ODP) Site 752, located on Broken Ridge in the Indian Ocean, provides such a Miocene‐to‐recent archive. We use X‐ray fluorescence (XRF) core scanning to build an eccentricity‐tuned age‐depth model and reconstruct paleoceanographic changes since 23 Ma. We find two intervals of enhanced productivity, during the early and middle Miocene (18.5–13.7 Ma) and late Pliocene/early Pleistocene (3–1 Ma). We also report a mixed eccentricity‐obliquity imprint in the XRF‐derived paleoproductivity proxy. In terms of grain size, three coarsening steps occur between 19.2–16 Ma, 10.8–8 Ma, and since 2.6 Ma. The steps respectively indicate stronger current winnowing in response to vigorous Antarctic Intermediate Water flow over Broken Ridge in the early Miocene, the first transient onset of Tasman Leakage in the Late Miocene, and the intensification of global oceanic circulation at the Plio‐Pleistocene transition. High‐resolution iron and manganese series provide a detailed Neogene dust record. This study utilized a single hole from an ODP legacy‐site. Nevertheless, we managed to provide novel perspectives on past Indian Ocean responses to astronomical forcing. We conclude that Neogene sediments from Broken Ridge harbor the potential for even more comprehensive reconstructions. Realizing this potential necessitates re‐drilling of these sedimentary archives utilizing modern drilling strategies. Plain Language Summary: This study looks into how the Indian Ocean changed since the start of the Neogene (last 23 million years). We use X‐ray fluorescence (XRF) analyses to measure the chemical composition of a marine sediment core (ODP Site 752), drilled on Broken Ridge at 1,086 m water depth. Our results show that the central Indian Ocean had overall higher productivity levels between 18.5–13.7 million years ago, but productivity levels varied significantly on timescales from ten thousand to hundred thousand years. These changes were influenced by variations in the Earth's orbit around the Sun. The grain size of the sediment became coarser at three intervals during the last 23 million years, which is thought to be caused by stronger ocean currents over Broken Ridge at those times. Overall, the study suggests that the Indian Ocean has gone through significant changes in the past and that the sediment from this site could be useful for further paleoceanographic research. Key Points: Ocean Drilling Program Site 752 is marked by a 405 and 100‐kyr eccentricity and obliquity imprint in X‐ray fluorescence (XRF)‐derived recordsLate Miocene Biogenic Bloom is absent at Broken Ridge according to the XRF‐derived paleoproductivity proxyShift in inter‐ocean connectivity to the middle latitudes modified current intensity over Broken Ridge throughout the Miocene [ABSTRACT FROM AUTHOR]

There are few documentations of far‐field effects of coolhouse glaciation and its signature preserved within Middle Jurassic carbonate platforms. Through outcrop logging and time series analysis we document the cyclostratigraphy of the upper Bajocian‐Bathonian interval of the Adriatic Platform, Croatia. The 200 m thick, ∼3.3 Myr duration cyclic platform record consists of peritidal carbonate parasequences (n = 109) with high‐energy grainstone‐rudstone bases fining up into micritic carbonate caps. There is little evidence of long‐term exposure near purported sequence boundaries, indicating the succession is conformable above the parasequence scale. Time series were constructed using Dunham rank and stratigraphic position, and parasequence thickness and stratigraphic position. A statistical estimation of accumulation rates using average spectral misfit (ASM) and correlation coefficient (COCO) methods that compare spectral peaks with an astronomical model at various sedimentation rates suggests that these rates ranged from 4.5 to 6 cm/kyr, which is compatible with long‐term rates based on thickness divided by duration. The time series analysis of rank series and cycle thickness series indicates long‐term obliquity modulation (∼1 Myr), short obliquity modulation (173 kyr), strong obliquity, and weak precession. The 173 kyr cycle is particularly evident in the cycle thickness series. The similarity of the spectra to the obliquity‐dominated Cenozoic coolhouse supports moderate southern hemisphere glaciation driving glacioeustatic sea level changes during the Middle Jurassic. Plain Language Summary: Earth's climate has been paced by eccentricity of its orbit (periods of 405,000 and 100,000 years) which modulates precession (or wobble, ∼20,000 years), and the tilt (obliquity) of its axis (∼40,000 years), with tilt and wobble being slightly shorter as we go back in time. We examined the succession of carbonate rocks in a 166–169.5 million‐year‐old, Middle Jurassic carbonate platform in Croatia, deposited during a time when there is evidence of moderate glaciation at the poles. The results indicate that the rock record was dominated by the tilt signal with little evidence of eccentricity. This is very similar to the deep sea record from 2 million to 700,000 years ago, which also is dominated by obliquity associated with moderate glaciation at both poles. The results strongly support the contention of moderate glaciation during the Middle Jurassic. Key Points: Middle Jurassic Bajocian‐Bathonian dominated by obliquity forcing of climate/sea levelOrbital signal is dominated by ∼1 Myr long obliquity cycle, short (173 kyr) obliquity modulation cycle, obliquity, and minor precessionObliquity forcing supports the existence of moderate ice sheets at high latitudes in the Middle Jurassic [ABSTRACT FROM AUTHOR]

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

A cyclostratigraphic study of the Late Precambrian Zhuya Group (Nikolskoye and Chencha Formations), and Torgo formation in the southern part of the Siberian Platform was carried out to determine the duration of the C-isotope anomaly imprinted in them. The similarity of the ratios of the period lengths of the cyclic components of the magnetic susceptibility in the coeval deposits of the remote sections of the Nikol'skoye and Torgo Formations indicates the connection between the revealed cyclicity and the basin-scale environment changes. According to the astrochronological model, the duration of the formation of the studied intervals of the Nikol'skoye (57 m) and Chencha (147 m) formations was 850 and 2500 ky, respectively. Extrapolation of the data obtained shows that the duration of the C-isotope anomaly of the Zhuya Group in the Vendian reference section on the Ura uplift was about 10 My, which is consistent with most estimates of the Shuram anomaly's duration and its stratigraphic analogues. [ABSTRACT FROM AUTHOR]

The Paleoproterozoic was an important stage in the evolution of life and the environment during Earth's history. Understanding astronomical rhythms and solar system behavior in the Paleoproterozoic is often challenging. In this study, ∼190 m high‐resolution magnetic susceptibility (MS) and ∼30 m high‐resolution Ba/Al data are used to conduct cyclostratigraphic analyses of the Chuanlinggou Formation in the Yanliao Rift, North China Craton. Spectral analysis indicates significant peaks at wavelengths of 12.1–7.7, 2.8–1.6, 0.58–0.33, and 0.29–0.22 m, which matches well with the astronomical cycles predicted by Waltham for ∼1,640 Ma. A 9.9‐Myr astronomical time scale is constructed by tuning the MS series to the 405‐kyr‐long eccentricity cycle. The geological records show ∼1.56‐Myr very long eccentricity period and ∼1.0‐Myr very long obliquity period (close to 3(s4 − s3) − 2(g4 − g3) = 0) in the Paleoproterozoic. The sea‐level change curve predicted by dynamic noise models reveals a significant ∼1.0‐Myr period, indicating that sea level fluctuation may have been driven by the very long obliquity period. Bayesian inversion is used to further estimate the evolution of the ancient Earth‐Moon orbital parameters, constraining a precession rate of 87.14 ± 0.25 arcsec/year and an Earth‐Moon distance of 341,530 ± 390 km for the Paleoproterozoic Changcheng System. These results indicate that astronomical orbital forcing may have played an important role in climate and sea‐level changes in the Precambrian, increasing the understanding of the fundamentals of global sea level fluctuations, orbitally driven mechanisms and the chaotic behavior of the Precambrian solar system. Plain Language Summary: Orbital parameters and long‐term behavior have changed during geological history. For the first time, we found new resonance states between Mars and Earth (i.e., a very long eccentricity period of ∼1.56 Myr and a very long obliquity period of ∼1.0 Myr) from the geological records of the Paleoproterozoic Changcheng System in the Yanliao Rift of the North China Craton. The reconstructed sea‐level change curve shows a significant ∼1.0‐Myr period, indicating that sea level fluctuations may have been driven by the very long obliquity period in the Precambrian. The orbital parameters in the Paleoproterozoic are recovered using Ba/Al ratios, and the calculated precession constant is 87.14 ± 0.25 arcsec/year. The Earth‐Moon distance was 341,530 ± 390 km, and the length of day (LOD) was 18.06 ± 0.05 hr, which indicates that lunar recession may have been slower in deep time. These results increase the understanding of astronomical rhythms and the chaotic behavior of the solar system in the Precambrian. Key Points: A new Earth‐Mars resonance state (3(s4 − s3) − 2(g4 − g3) = 0) is revealed from the Precambrian geological recordsThe ∼1.0‐Myr very long obliquity period significantly affected sea level fluctuations under the Mesoproterozoic greenhouse climate [ABSTRACT FROM AUTHOR]

Over the last 66 million years, Earth has undergone dramatic climate changes, shifting from a warm greenhouse to the more recent cold icehouse with polar ice caps in both hemispheres. Geological records show that the transition between these equilibrium states caused significant long‐term eustatic sea‐level and atmospheric CO2 decline paced by external orbital motions. Such eustatic variability influenced the stacking pattern of sedimentary successions, generating cyclic sequence boundaries that may be globally correlated. However, the impact of such oscillation along the Brazilian margin is largely unknown. This study used the natural gamma‐ray log from a well (ES‐2) at the offshore Espírito Santos Basin (western South Atlantic) measured between late‐Palaeocene and late‐Miocene. Null hypothesis tests ‐ evolutionary Average Spectral Misfit and Correlation Coefficient of no orbital modulation ‐ were executed to confirm the influence of astronomical parameters. The evolutionary Time Optimization algorithm was used to extract the sedimentation rate and depositional time. The anchored timescale shows a chronological interval placed between 58.97 and 7.72 ± 0.1 Ma (mid‐Thanetian – late Tortonian), mostly influenced by long‐eccentricity and short‐eccentricity (405 kyr and ca 100 kyr, respectively) and obliquity (ca 40 kyr) and their respective amplitude modulations (ca 2.4 Myr and 1.2 Myr). Applying the Integrated Prediction Error Filter Analysis and a high‐resolution age model, this study identified main depositional trends through time and correlated them to global sea‐level change. The correlation indicates that several intervals of global sea‐level reduction agree with a regressive trend at the ES‐2 site, but this relation is affected during enhanced regional tectonic activity intervals, as related to the emplacement of the Abrolhos Archipelago. The strategy adopted here is a way to join cyclostratigraphy and sequence stratigraphy, and promotes high‐resolution local‐to‐global correlation by identifying key stratigraphic surfaces. This will be relevant for palaeoclimatic studies and the geoscientific industry. [ABSTRACT FROM AUTHOR]

Data on the magnetic properties and composition of chemical elements in the stratotype of the Belogrodni Formation (Danian Stage) were obtained and their cyclostratigrapic analysis was carried out. Based on the Fourier transforms of vertical sequences of petromagnetic and geochemical parameters, cycles corresponding to the long and short eccentricity periods of Earth's orbit were identified in the section and the sedimentation time (~2.1 myr) and glauconite formation rate (~1 cm/kyr) were estimated. [ABSTRACT FROM AUTHOR]

The Qaidam Basin, as the largest inland basin within the Tibetan Plateau, has accumulated more than 10,000 m of Cenozoic continental sediments. It serves as a crucial research area for documenting Cenozoic climate changes and plateau uplift processes in the Asian interior. Additionally, the basin holds vast reserves of oil and gas resources, making high-resolution drilling data invaluable for studying paleoclimate. In this study, the longsequence lacustrine deposits of JS1 drill core across the Shizigou Formation in the Yiliping Depression at the western center of the basin were studied, aiming to establish an astronomical timescale for the Shizigou Formation and investigate the characteristics of paleoclimatic changes during the late Miocene to the Pliocene for the Asian interior. The analysis was carried out using high-resolution natural gamma ray (GR) data sequences, employing techniques such as spectral analysis, filtering, and wavelet analysis in cyclostratigraphy. The results indicated the presence of a stable Milankovitch orbital signal was perfectly recorded in the Shizigou Formation, primarily influenced by eccentricity cycles, with weaker obliquity and precession cycles. Using the stable and continuous 405 ka eccentricity cycle in astronomical tuning, a "floating" astronomical timescale with a duration of 6.1 Ma for the Yiliping depression's Shizigou Formation has been established. With reference to previously established stratigraphic age anchor points, an absolute astronomical timescale (2.5-8.6 Ma) has been ultimately provided for the Shizigou Formation. Simultaneously, a clear 100 ka short eccentricity cycle record has been identified during the Pliocene (5.3-2.5 Ma), which corresponds in time with the aridification within the basin during this Pliocene period. In addition, a comparison of the Pliocene natural gamma ray curve of the Qaidam Basin with global ice volume variations indicated that the basin's aridification was influenced by global cooling, with eccentricity-modulated precession cycles controlling solar radiation and subsequently affecting the evolution of lakes in the arid region of Inner Asia. [ABSTRACT FROM AUTHOR]

We present high‐resolution (every 2 cm) magnetic susceptibility (MS) data from the Sancerre‐Couy drill core (Paris Basin), spanning the latest Sinemurian to the earliest Aalenian (Early Jurassic). This record allows to build a 20‐million‐year cyclostratigraphic interval using the stable 405 kyr (g2–g5) orbital eccentricity cycle and to focus on long‐period cyclicities and their potential implications for the chaotic diffusion in the inner Solar System and sea‐level changes. Time series analysis indicates evidence of two long‐period cyclicities of 1.6 and 3.4 Myr. These Early Jurassic cyclicities likely correspond to the Cenozoic orbital cyclicities of 2.4 Myr (g4–g3) and 4.7 Myr eccentricity terms. Shortening of eccentricity terms during the Early Jurassic is potentially related to the chaotic orbital motion of the inner planets expressed in the resonant argument θ = 2(g4–g3) − (s4–s3). The 1.6 Myr (g4–g3) cycle matches the third‐order eustatic sequences, whereas the 3.4 Myr cycle has no equivalent in the reference eustatic chart. These cycles of several million years are superimposed a cyclicity of ca. 7.5 Myr, which may correspond to the eccentricity term of 9.5 Myr, previously detected in the Cenozoic. Such cyclicity matches the global, 'shorter' second‐order sea‐level sequences and is strongly documented in the sedimentological and mineralogical proxy data, hence supporting the potential key role of orbitally paced climate and sea‐level changes at this timescale. [ABSTRACT FROM AUTHOR]

Chrysophyte cyst fossils were widely pyritized and preserved in black shales from the seventh member (Ch7 Mbr) of the Yanchang Formation in the Ordos Basin. The age, pyritization, and preservation model of these fossils have not been studied previously. In this study, the astronomical orbital cycles of the Ch7 Mbr were determined based on the gamma ray series of the Yan56 and Zhen 421 wells. An astronomical time scale (ATS) analysis revealed that the depositional duration of Ch7 Mbr was approximately 5 Ma. According to the 206Pb/238U radiometric dating of zircons using laser ablation inductively coupled plasma mass spectrometry (La-ICP-MS), the tuffs at the bottom of Ch7 Mbr were crystallized at 234 Ma, which served as a geological anchor. The ages of three submembers in Ch7 Mbr were estimated at 234.0–232.4 Ma, 232.4–230.8 Ma, and 230.8–229.1 Ma based on ATS analysis. In addition, chrysophyte cyst fossils were well preserved by pyritization in the Ch7 Mbr black shales. There were six types of microscopic morphologies with different pores, collars, and surface ornamentation under scanning electron microscopy (SEM). The age of the chrysophyte cyst fossils was at least 233.6 Ma in the Triassic Carnian Pluvial Episode (CPE) based on the 405 kyr tuned ATS. Moreover, the paleoredox conditions in Ch7 Mbr were reconstructed, and a preservation model of chrysophyte cyst fossils was established based on geochemical analyses. Fossil pyritization was caused by bacterial sulfate reduction near the water-sediment interface under suboxic to anoxic environmental conditions. Pyritization was initiated on the walls of the chrysophyte cysts by the formation of microcrystalline pyrite. Because of the gradual pyritization of the chrysophyte cyst wall, the organic matter in the interior of the fossil was well preserved. [ABSTRACT FROM AUTHOR]

The article focuses on the history of Earth's atmospheric thermal tide, its composition, and mean temperature. It mentions the study explores the hypothesis that an atmospheric oscillation resonated with the Solar driving around 600 million years ago, affecting the length of the day. It highlight ny using global circulation models and geologic data, the researchers find evidence supporting the resonance hypothesis and provide insights into the Earth-Moon system's history.

In this communication, Earth temperature series in air and soil are analyzed and features that become convoluted with the known earth cycles of day-night and its orbit around the sun are separated. Atmospheric carbon dioxide concentrations are also considered. Earth weather changes (e.g., cloud, wind, rain, polar jet streams, and atmospheric pressure) in real time affect daily temperatures in a complex manner. A statistical model that accounts for autocorrelation and linear trend is evaluated together with empirical description of the series. Further graphical analysis is used to enhance remaining features and extreme events. Gaussian bell-shaped curve modeling of each year's daily profile is described. Further, Gaussian parameter-based anomalies are introduced together with soil anomalies at 30 cm depth. Semi-variogram components are shown along with folded percentile or mountain plots for data visualization. The Chow test is described for detection of any structural changes in data series. For much of the statistical analysis, temperatures observed daily are most appropriate because they carry variation due to earth, sea and sky weather over a single day-night earth rotation cycle. Also, the ever changing earth position along its orbital path captures a varying amount of solar energy, hence the shape of the temperature cycle as one sees it. Human activity and climate changing factors appear to affect temperature cycles within and over years. A double bell-shaped Gaussian curve fit can indicate climate changing effects of Earth life. [ABSTRACT FROM AUTHOR]

The plate movement during the Paleogene created the tectonic framework of the Bohai Bay basin with alternating depressions and uplifts. It is necessary to study the sequence stratigraphic framework of a single lake basin and its internal sedimentary response from the perspective of geochronology. Taking the Eocene sedimentary series in the Gaoliu area of the Nanpu sag for example, the preprocessed gamma-ray curve of the standard well was used to identify the Milankovitch cycles using spectral analysis, continuous wavelet transformation and evolutionary spectral analysis. Based on the anchor point of absolute geological age, the astronomical timescale was established and the sedimentation rate was estimated. The paleo-lake level change and the paleo-sediment supply rate were reconstructed. From the perspective of regional sedimentary evolution, the indicative significance of Milankovitch records of depositional response was discussed. The results show these as follows. Eocene sedimentary sequence is controlled by long eccentricity, short eccentricity, obliquity and precession. 20 long eccentricity periods and 85 short eccentricity periods were identified, totaling 8. 1 Ma. The absolute geological ages of the top boundaries of Es1 3, Es2, Esx 1 and Esz 1 are 33. 3 Ma, 31. 9 Ma, 30. 5 Ma and 29. 5 Ma respectively. The average sediment accumulation rate is about 124. 2 m / Ma. The lake level rose in a large scale from 36. 6 Ma to 33. 3 Ma, and continued to fall from 33. 3 Ma to 30. 5 Ma, and slightly rose again from 30. 5 Ma to 28. 5 Ma. The continuous activities of the Xinanzhuang fault and the Baigezhuang fault from 36. 6 Ma to 28. 5 Ma strengthed the sediment supply rate of the ancient Yanshan Mountains. The response of depositional evolution to tectonic signal is stronger than that to climate signal, which leads to the middlescale fan deltas during the early Eocene and large-scale braided-river deltas during the middle and late Eocene in the Gaoliu area. [ABSTRACT FROM AUTHOR]

Catchment erosion not only shapes various landforms of the earth's surface but also affects the rates of chemical weathering and CO2 absorption by controlling the exposure of rock fragments, and thus acts as a regulator of the global climate. Therefore, studying the occurrence and controlling factors of catchment erosion can improve our understanding of topographic evolution and long-term climate change. This paper introduces the "comminution age" method based on (234U/238U) of sediment detrital components and its applications to indicate the catchment erosion depth, which is widely applied to different depositional environments. In tectonically stable regions, where there is shallow erosion, the sediment output from the catchment is usually accompanied by a low (234U/238U). On the other hand, where there is deep erosion, the (234U/238U) of the downstream sediments is usually high. In tectonically active regions, deep erosion is common, and the sediment erosion process is subject to rapid material transport, such as landslide-induced sediment displacement. Since the sediment exposure history is short, the (234U/238U) of the detrital components is close to 1, thus reaching "secular equilibrium". The comminution age method is promising in terms of tracing catchment erosion depths at the orbital scale. Furthermore, this method is also sensitive to the erosion changes caused by rapid climate changes and human activities. [ABSTRACT FROM AUTHOR]

The semi‐enclosed marginal Japan Sea is sensitive to global changes and responds to orbital‐scale variability. Sediment core samples from Integrated Ocean Drilling Program Site U1423 were processed for detrital grain size and semi‐quantitative mineral analysis to assess the sediment characterization and depositional environment in the Japan Sea over the last 1200 ka. The mean grain data suggest the dominance of the silt size fraction over sand and clay in the whole period, while sand content increases dramatically between 600 and 150 ka. The end‐member energy modelling of grain size data suggests that sediment deposition took place under two energy conditions over the last 1200 ka. The low‐energy conditions observed during the middle Pleistocene transition (MPT) is mainly related to the wind deposition with the sediment characteristics being moderately to poorly sorted and coarse to nearly symmetrical skewed during global cooling and enhanced East Asian Winter Monsoon (EAWM) winds in the northern Japan Sea. Post MPT, periodic fluctuations between higher and lower energy conditions are observed, and the depositional environment is controlled by the EAWM wind, and precipitation intensity, glacio‐eustatic sea‐level changes and sea‐ice volumes. During the period, detrital sediments are poorly sorted and nearly symmetrically skewed, marked by the dominance of quartz, plagioclase and k‐feldspar. The spectral analysis grain size‐related data shows the presence of 228, 41 and 23 kyr orbital paced cycles, which are also observed in the Chinese Loess Plateau's normalized quartz mean grain size. This study is the first report of 228 kyr cycles from the Pleistocene Japan Sea sediments indicate that sediment deposition in the Japan Sea is associated with ~200 kyr eccentricity cycle as in the Chinese Loess Plateau. [ABSTRACT FROM AUTHOR]

Climate oscillations preserved in sedimentary archives tend to decrease in resolution further back in Earth's history. High‐frequency climate cycles (e.g., ∼20‐Kyr precession cycles) are especially prone to poor preservation due to sediment reworking. Recent studies have shown, however, that given sufficient basin accommodation space and sedimentation rate, shallow‐marine paleoclimate archives record precession‐driven hydroclimate change in mid‐low latitude regions. Our study evaluates how the evolution of a rapidly uplifting orogen influences the recording of astronomical climate forcing in shallow‐marine sedimentary strata in the Taiwan Western Foreland Basin (WFB). Time‐series analysis of gamma‐ray records through the late Miocene–Pliocene Kueichulin Formation shows that during early stages of Taiwan orogenesis (before 5.4 Ma), preservation of precession‐driven East Asian Summer Monsoon variability is low despite increasing monsoon intensities between 8 and 3 Ma. The Taiwan Strait had not formed, and the southeast margin of Eurasia was open to the Pacific Ocean. Consequently, depositional environments in the WFB were susceptible to reworking by large waves, resulting in the obscuration of higher‐frequency precession cycles. From 5.4 to 4.92 Ma, during early stages of emergence of Taiwan, basin subsidence increased while sedimentation rates remained low, resulting in poor preservation of orbital oscillations. After 4.92 Ma and up to 3.15 Ma, Taiwan became a major sediment source to the WFB, and sheltered the WFB from erosive waves with the development of Taiwan Strait. The elevated sediment influx, increased basin accommodation as the WFB developed, and formation of a semi‐sheltered strait, resulted in enhanced preservation of precession‐driven East Asian Summer Monsoon variability. Plain Language Summary: Rhythmic changes in the shape of Earth's orbit (eccentricity, ∼100‐Kyr cycles), tilt (obliquity, ∼41‐Kyr cycles), and axial rotation (precession, ∼20‐Kyr cycles) drive climate change that may be preserved in sedimentary records. Orbital climate cycles are recorded in clastic shallow‐marine strata where the amount of sediment transported from land to sea and space available for deposition in the basin are sufficiently high. Our study of the Kueichulin Formation in the Taiwan Western Foreland Basin (WFB) shows how a rapidly uplifting orogen influences the preservation of different climate cycles in the shallow‐marine realm. During early Taiwan orogenesis (before 5.4 Ma) when the Taiwan Strait did not exist, sediment in the WFB were susceptible to reworking by erosive waves generated in the Pacific Ocean, which obscured higher‐frequency precession cycles. From 5.4 to 4.92 Ma, Taiwan began to emerge from the Pacific Ocean and the WFB began to subside, but sedimentation rates were low, so climate cycles were poorly preserved. After 4.92 Ma, rapid uplift and erosion of Taiwan and WFB subsidence continued, resulting in increased sedimentation to the sea, increased sediment accumulation space, and the formation of a strait that sheltered the WFB from waves, which all served to enhance the preservation of precession. Key Points: Preservation of different climate cycles in shallow‐marine records is influenced by a rapidly uplifting orogenDuring early uplift of Taiwan (before 5.4 Ma), only eccentricity and obliquity were preserved due to low sedimentation/basin accommodationFormation of a sheltered strait and increased sediment flux/basin subsidence as Taiwan uplifted enhanced preservation of precession cycles [ABSTRACT FROM AUTHOR]

The Zhujiang Formation in the Baiyun Sag, Pearl River Mouth Basin, China, is formed primarily in a deep-water continental slope environment. Its chronostratigraphic framework is based on biostratigraphy and sequence stratigraphy, and its geological dating is based on micropaleontological data. This makes it difficult to obtain precise absolute ages for various geological events. In this study, gamma ray (GR) well log data from Wells Y1, Y2, and Y3 were used as paleoclimate proxies, and spectral and wavelet analyses were used to conduct cyclostratigraphic research. The results show that the Milankovitch cycles were preserved in the Zhujiang Formation in the Baiyun Sag. Stratigraphic cycles controlled by 405 and 95 ka orbital eccentricity, 40.4 ka orbital obliquity, and 23.5 ka orbital precession cycles can be identified; the signal of stratigraphic cycles controlled by the 405 ka long eccentricity cycle is the strongest. The floating astronomical time scale is constructed based on 405 ka orbital eccentricity cycle tuning of the GR series. The precise durations of the Zhujiang Formation in Wells Y1, Y2, and Y3 are 7.13, 6.93, and 7.18 Ma, and the average deposition rates are 4.68, 5.91, and 5.33 cm/ka, respectively. The Zhujiang Formation was divided into 17 fourth-, 76 fifth-, and 174 sixth-order cycles using the 405, 95, and 40.4 ka orbital periods as the dividing scales, respectively. This study provides a quantitative method for high-precision isochronous stratigraphic division and correlation in deep-water sedimentary systems.

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]

There are key patterns of variation in the (litho‐) stratigraphical record, which, with advances in computing technology in recent decades, have become amenable to objective numerical analysis. This research has chiefly focused on the search for spatially regular cycles in the sedimentary rock record, since there are theoretical grounds for believing that these would be periodic and thus provide a means of time‐calibrating the stratigraphical records in which they occurred. Less popular lines of research consider the scaling relationships of the tangible, measurable sedimentary rock layers, and of the hiatuses, individually of indeterminate length, that punctuate these layers. Objective source data for all these analyses is provided, on limited (usually decametre) scales, by detailed lithological logging, sampling and dating of sections provided by exposures and cores. An objective global lithostratigraphical database, with larger, kilometre scales, is provided by the widespread practice of electric (wire‐line) logging of deep wells. This involves measurement, at 6‐inch (~15 cm) depth intervals of lithology‐related petrophysical properties. Rapid desk top computer analysis of the hundreds or thousands of readings that comprise these two data series, searches for patterns of variation. This review considers the published evidence for 'ubiquitous' cyclicity and its use in chronostratigraphy, despite the contrary claims that stratigraphical records are predominantly random in character. [ABSTRACT FROM AUTHOR]