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During the Late Cretaceous, Earth's climate oscillated between warm and cool states, and global oceans changed between anoxic and oxic conditions, resulting in black/gray shales and oceanic red beds (ORBs) deposition, respectively. To understand such climate/ocean dynamics, this study investigated bulk Hg and Hg isotopes, as well as Fe3+/Fe2+ in Upper Cretaceous sediments deposited in southern Tibet and the North Atlantic. In both areas, black/gray shales show much higher Hg concentrations than ORBs, indicating enhanced Hg flux to global oceans during time of black/gray shale deposition. Black/gray shales show lower Fe3+/Fe2+ and positive Δ199Hg, suggesting a significant input of Hg into the anoxic/dysoxic ocean via atmospheric deposition. The isotope values are consistent with a volcanic source for this excess Hg. ORBs show high Fe3+/Fe2+ and negative shifts of Δ199Hg, suggesting that the dominant source of Hg into the oxic oceans was via terrestrial runoff. This study suggests that volcanism was an important driver of the climate/ocean dynamics during the Late Cretaceous. Plain Language Summary: The Late Cretaceous ocean developed widespread black/gray shales and oceanic red beds which were deposited in warm‐anoxic/dysoxic and cool‐oxic oceanic conditions, respectively. The driving force for such climate/ocean dynamics remains unclear. This study demonstrates distinct Hg concentrations and isotopic composition in black/gray shales and oceanic red beds, which suggest that volcanism was a major trigger of the climate/ocean dynamics in the Late Cretaceous. Key Points: The Late Cretaceous black/gray shales and oceanic red beds display opposing mass‐independent fractionation of Hg isotopesChanges in climate/ocean conditions had strong control on the sources of Hg in the Late Cretaceous oceanVolcanism served as an important driving force of the climate/ocean dynamics during the Late Cretaceous [ABSTRACT FROM AUTHOR]

The East Asian coastal mountains have been in place during the Late Cretaceous times, thus substantially influencing the Asian climate. So far, their altitude is uncertain. Here we investigate the influence of such mountains on Asian climate using an atmosphere‐ocean general circulation model, Community Earth System Model version 1.2.2. Simulation results show that extensive deserts would develop over the eastern part of the East Asia if the altitude of the coastal mountains was greater than 2 km. This is due to the pumping effect of the coastal mountains which deprives the moisture from the East Asian interior during summer and autumn, leading to less precipitation and greater potential evapotranspiration. The existence of extensive desert areas would be more consistent with the presented Asian paleoenvironmental reconstructions. Therefore, our results independently indicate that the altitude of the coastal mountains had attained 2 km or more by the early Late Cretaceous. Key Points: The East Asian coastal mountains had risen to 2 km or higher during the early Late CretaceousThe East Asian coastal mountains had a drying effect on the Asian climate during the Late CretaceousThe East Asian coastal mountains decreased the Asian precipitation by means of their pumping effect [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 first and second members of the Nenjiang Formation (K2n1+2) in the Songliao Basin, northeast China, are an interval of dark-colored mudstone. Paleoenvironmental studies of these strata are useful for understanding the terrestrial environment under a greenhouse climate and hydrocarbon accumulation in lake basins. In this study, clay mineralogy of the K2n1+2 from four borehole or outcrop sections is investigated to understand terrestrial paleoenvironment during the depositional period in the Late Cretaceous. In the mudstone samples, smectite and illite are the predominant clay minerals, and were derived from weathering of parent rocks in a temperate, sub-humid to sub-arid climate; kaolinite and chlorite are minor clay species. The difference in the clay-mineral assemblages between the eastern and western margins of the basin was primarily controlled by provenance lithology, and the high smectite content in the western basin resulted from alteration of volcanic rocks exposed in the Greater Xing'an Range area. The increasing illite content and ratio of illite/smectite percentages in the upper part of the first member of the Nenjiang Formation indicate paleoenvironmental change. This temporal change in the clay-mineral composition was primarily caused by a regionally cooler and drier paleoclimate, consistent with previous paleoenvironmental reconstructions. [ABSTRACT FROM AUTHOR]

A large body of evidence suggests that there were extensive coastal mountains along the East Asian margin during the Late Cretaceous. However, current knowledge of the paleo-mountains — the period, range, and elevation — is limited. Therefore, direct paleoaltimetry is needed to validate and evaluate the paleo-mountains in East Asia. Our study area is Jiaolai Basin, which is located at the East Asian continental margin. We estimate the paleoelevation of Jiaolai Basin during the Late Cretaceous using carbonate clumped isotope paleothermometry. After correcting for seasonal preference, latitudinal difference, and secular climate change, we conclude that the paleoelevation of Jiaolai Basin was almost certainly ≥2.0 km at ∼80 Ma. Combined with the evidence from stratigraphy, paleogeography, and paleoclimatology, our results suggest that the existence of coastal mountains along East Asia during the Late Cretaceous is likely and the model of Okhotomorsk–East Asia collision is preferred. [ABSTRACT FROM AUTHOR]

Abstract: Cretaceous climate data of the long-lived Cretaceous Songliao Basin (SB) in eastern Asia is correlated and compared with the Western Interior Seaway (WIS) on the northern American plate, in order to understand better the dynamics of the Earth's past ‘greenhouse’ climates. Nearly continuous Late Cretaceous terrestrial deposition in the Songliao Basin is represented by two cores totaling 2431m in length. The Turonian–Maastrichtian age of the section is based on integrated stratigraphy, and is comparable in age with Upper Cretaceous strata in the WIS. Being consistent with global trends, the dynamic Late Cretaceous climates of both the SB and WIS gradually cooled from the warmest Albian–Cenomanian time to the end of the Maastrichtian with several intervening warm periods as did the global climate. However regional differences existed, the Songliao Basin climate was humid to semi-humid, warm temperate–subtropical and the Western Interior Seaway was in the humid, warm temperate zone and experienced only moderate climatic changes. The shifts of oxygen isotope data in the Songliao Basin were frequent and abrupt, whereas WIS records more gradual change affected mainly by fresh-water runoff mixing with southern Tethyan and northern Arctic waters. Sedimentary cycles of eccentricity, obliquity and precession bands are recorded in both the SB and WIS basins. The sedimentary cycles in the WIS and SB are interpreted to be related to variations of the wet/dry runoff cycles, which indicate that orbital forcing played an important role in global climate change in Late Cretaceous. The most favorable condition for organic carbon burial in both the SB and WIS basin was bottom water anoxia regardless of the cause of the anoxia. But the organic carbon burial rate was usually much higher in the Songliao Lake than in the WI epeiric sea suggesting that giant lakes may serve as important sinks of atmospheric CO2. In both basins organic-rich deposits formed during a rise in water level and incursion of saline waters. The integration of paleoclimate data from Cretaceous marine deposits and terrestrial sedimentary record will promote our understanding of the Cretaceous ‘greenhouse’ climate change and may provide insights for a future greenhouse world. [Copyright &y& Elsevier]

Abstract: In order to define the provenance change across the nonconformable boundary between the second and the third members of the Upper Cretaceous Nenjiang Formation (Campanian) in the north-central area of the Songliao Basin, two sandstone samples above (sample a-1 from the fourth member of the Nenjiang) and below (sample z-1 from the first member of the Yaojia Formation) the nonconformity were collected from core holes. U–Pb dating was performed on detrital zircons separated from the three sandstone samples. Detrital zircons from sample a-1 have dominant age populations of 100–110Ma, 190–220Ma, and ~1800Ma, and sample z-1 has dominant ages of 130–150Ma and ~350Ma. This paper demonstrates that the provenance of the fourth member of the Nenjiang Formation is significantly different from the first member of the Coniacian Yaojia Formation. The provenance above the nonconformity became much more complex and the eastern source increased significantly, while the western source sharply declined. The main source areas of the fourth member of the Nenjiang Formation are mainly the Zhangguangcai Range, the eastern Lesser Xiang'an Range and the southeast of Songliao Basin. The dominant provenance of the first member of the Yaojia Formation is the northern, the central and the southern Great Xing'an Range. According to the depositional ages and combining the latest seismic stratigraphic profiles in the Songliao Basin, the tectonic inversion of the eastern Songliao Basin began between 73Ma and 87Ma, which differs from the previous age of 73Ma. [Copyright &y& Elsevier]

Abstract: In this study, the East Asian climate during the Late Cretaceous (ca 80 Ma) is examined by using the Community Climate System Model Version 2 (CCSM2) from the National Center for Atmospheric Research (NCAR) and the reconstructed palaeogeographic data. The simulation results indicate that the large-scale prevailing wind directions and pressure systems over East Asia showed a remarkable seasonal variation during 80 Ma, so that it can be inferred that there existed a monsoon circulation over East Asia at that time. Compared to the present climate, the atmospheric circulation systems over the Eurasian continent in the Late Cretaceous showed a stronger meridional feature, which was possibly correspondent to a smaller lateral extension of the Eurasian continent at that time. Moreover, under a warmer background in the Late Cretaceous, the winter and summer monsoons over East Asia showed a synchronous variation, with a stronger winter monsoon as well as a stronger summer monsoon. The pattern of annual mean precipitation was similar to that of the present climate, with the maximum precipitation appearing in the intertropical convergence zone (ITCZ) between 10°S and 10°N. There was also more precipitation over the eastern coasts of the continent adjacent to the western Pacific, with the central value exceeding 1200 mm, and there was less precipitation in the midlatitudes of the inland areas. Although a more precipitation belt also appeared near 30°N over the western Pacific, which was similar to the present climate, there was no high precipitation belt over the land of East Asia. This feature implies that the uplift of the Tibetan Plateau plays an important role in the formation of the present baiu (plum rains). Moreover, the simulated climate over East Asia during 80 Ma was warmer relative to the present and the surface air temperature was 2 °C higher at the same latitudes compared to the present climate. This simulation result is closer to the estimation from the geological evidences. [Copyright &y& Elsevier]

Abstract: Red marine mudstones intercalated with pelagic marlstones, limestones and radiolarian cherts comprise the Chuangde Formation, which overlies mid-Cretaceous dark grey shales in the northern subzone of the Himalayan Tethys of southern Tibet. The red mudstones reflect deposition below the carbonate compensation depth (CCD) in a deep oceanic basin. The intercalated, thin-bedded marlstones represent fine-grained turbidites derived from the upper slope and transported into the adjacent deep basin. Planktonic foraminifera and nannofossils in the marlstones indicate a Santonian–early Campanian age for the formation. The red beds of the Chuangde Formation were deposited in a highly oxygenated deep-sea environment. This is confirmed by the high iron-trioxide content, the negative Cerium anomaly at the bottom of the red sequence, and the very low total organic carbon content (TOC 0.01–ca. 0.14%). Deposition of the red beds coincided with a Santonian–early Campanian diversity peak of planktonic foraminifera. The environmental interpretation is supported by the bulk carbon isotope δ13C value of carbonate turbidites that becomes more positive stratigraphically up from the base of the formation. The highly oxygenated bottom-water conditions were not restricted to a deep ocean basin, but extended up to the continental rise/slope, as indicated by synsedimentary red marls incorporated in slumps and olistoliths near the top of the formation. This indicates that not only the bottom waters but also intermediate waters were highly oxygenated. Deposits of the Chuangde Formation are similar to Upper Cretaceous oceanic red beds (CORBs) in Western Europe, such as the Scaglia Rossa in Italy and the Capas Rojas in southern Spain. They represent the easternmost occurrence of Upper Cretaceous pelagic red beds of the Tethys. Late Cretaceous oxic oceanic conditions extended into the southern Tethys because the formation was deposited in southern palaeolatitudes. Therefore, the change from a dysoxic/anoxic to an oxic bottom ocean environment during the Late Cretaceous was at least hemiglobally if not globally wide. The change to oxic bottom conditions occurred later in the southern Tethys than in the western Tethys, where it began during the late Turonian. Several different earth processes could have caused such change. We suggest that the oxidized character of these deep-sea deposits was a result of a combination of various processes, among which very low sedimentation rates and changes in bottom ocean circulation may have been the most important. [Copyright &y& Elsevier]

The surface uplift of the Tibetan Plateau (TP) and its geomorphology evolution has triggered aridification of Asia's interior and drainage development at the eastern margin of the plateau. However, how the pre-Cenozoic early growth histories of the TP impact the drainage system and climate is poorly constrained. The Late Mesozoic Lacustrine evaporite-bearing basins on the eastern margin of the TP record significant information on the uplift of the source terranes, source-to-sink system development and climate change. In this study, we presented detrital zircon U–Pb ages from the Upper Cretaceous Yunlong Formation in the Lanping Basin, as well as Hf isotopic, petrographic, direct statistical, and multidimensional scaling analyses, and use them to characterize the provenance and reconstruct the drainage system. All of the samples have five major age peaks at 200–290 Ma, 400–490 Ma, 750–1000 Ma, 1750–1950 Ma, and 2400–2600 Ma with mostly negative ɛ Hf (t) values (81%). We infer the sediments are primarily derived from recycled sediments of the Songpan-Garze terrane, and partly from the Sichuan Basin and the Southern Qiangtang terrane, as well as the exposed magmatic rocks of the Yidun Arc and Songpan-Garze terrane. The provenance features of the contemporaneous sediments from the Sichuan, Xichang, Chuxiong, and Simao basins indicate a complex hierarchical drainage pattern on the eastern margin of the TP during the Late Cretaceous. The hierarchical drainage system exhibits a complete gradational cycle of lake-basin types from overfilled freshwater Sichuan Basin through balanced fill saline Xichang Basin and underfilled hypersaline Chuxiong, Lanping, Simao, and Khorat Plateau basins from proximal to distal. The early growth of the TP primarily controlled the drainage and lake-basin evolution by not only causing the uplift and exhumation of the source areas and providing large amounts of clastic material to the proximal sub-drainage areas but also intensifying the aridity and deposition of evaporites. [Display omitted] • The Upper Cretaceous strata in the Lanping Basin are mostly recycled from the Songpan-Garze terrane. • A hierarchical drainage pattern and a gradational cycle from overfilled to underfilled existed. • Tectonic uplift of the source terrane primarily control the drainage development. [ABSTRACT FROM AUTHOR]

As a typical greenhouse period, the Late Cretaceous was characterized by an extremely warm and arid climate. In this period, intermontane deserts were widely distributed in South China, which can be used to inform the evolution of the palaeogeography and palaeo-wind patterns during the hot climate of the Late Cretaceous. The Jurong Basin is located at the eastern margin of South China and close to the palaeo-Pacific Ocean; it has typical aeolian deposits but is hitherto less studied. In this study, four sedimentary facies (aeolian dune, dry/damp/wet interdune, sandsheet, and desert lake facies) and three forms of aeolian dunes (simple, compound, and complex) are identified in the Upper Cretaceous Chishan Formation, confirming the development of an intermontane desert in the Jurong Basin. The dynamic evolution models show that the intermontane desert transitioned from a lacustrine-dominated to an aeolian-dominated system, which indicates a gradual drying trend. We suggest that the development of the Chishan intermontane desert was controlled by the Late Cretaceous greenhouse climate, the accelerated aridification of the subtropical high, and the rainshadow effect of the coastal mountains. Palaeo-wind directions in the Chishan desert show westerlies and possible palaeo-monsoon wind patterns. The input of palaeo-monsoon moisture led to the development of desert lake and damp/wet interdune deposits in the Chishan desert, which indicates that the Jurong Basin might have been on the windward side of the coastal mountains during the Late Cretaceous. Our study extends the eastern boundary of the South China intermontane desert system during the Late Cretaceous. [Display omitted] • Late Cretaceous intermontane desert developed at the east margin of South China. • Dynamic evolution models of the intermontane desert are reconstructed. • Hot climate and tectonism led to the development of intermontane deserts. • Wind pattern dual controlled by the westerlies and palaeo-Pacific monsoon. • Rain shadow effect in the windward side of the coastal mountains. [ABSTRACT FROM AUTHOR]

• The Chuburi pluton has an emplacement age of 73 Ma. • The Chuburi pluton is composed of highly fractionated I-type granites. • The Chuburi pluton was generated by magmatic mixing of mantle and lower crust. • The generation of the Chuburi pluton was associated with lithospheric delamination. The tectonic evolution of the Lhasa and Qiangtang collision zone is poorly understood due to a lack of pivotal magmatic records and complex geology in central Tibet. In this study, we present zircon U–Pb ages, whole-rock major and trace elements, and Sr–Nd–Pb isotopic data for the newly discovered Chuburi pluton in the southern Qiangtang block. Zircon U–Pb data reveal that the Chuburi pluton was emplaced during the Late Cretaceous (ca. 73 Ma). Bulk-rock analyses show that this intrusion is characterized by high SiO 2 , Na 2 O and K 2 O, but low MgO, CaO and P 2 O 5. The granites are enriched with large-ion lithophile elements and light rare earth elements, with marked Eu anomalies, and there are few heavy rare earth elements and high field strength elements. These geochemical features indicate that the Chuburi pluton is a highly fractionated I-type granite. The nine granitic samples show high (87Sr/86Sr) i ratios (0.7064–0.7089), negative εNd(t) values (−1.94 to −5.59) and have Nd isotopic model ages ranging from 0.76 to 0.97 Ga. The initial Pb isotopic ratios of the Chuburi pluton is uniform: (206Pb/204Pb) t = 18.774–18.884; (207Pb/204Pb) t = 15.695–15.713; (208Pb/204Pb) t = 39.362–39.613. Based on geochemical characteristics of the Chuburi pluton, and consideration of the region geological setting, we suggest that the parent magma was generated by magmatic mixing of mantle and lower crust, and then undergoing extensive fractional crystallization with removal of K-feldspar, plagioclase, mafic mineral and minor accessory mineral. The crust beneath the central Tibet may have been significantly thickened following the final Lhasa-Qiangtang amalgamation. We argue the generation of the Chuburi pluton can be interpreted as a result of regional lithospheric delamination. [ABSTRACT FROM AUTHOR]

The tectonic evolutionary history of the Lhasa and Qiangtang collision zones remains hotly debated because of the lack of pivotal magmatic records in the southern Qiangtang subterrane, central Tibet. We present zircon U–Pb dating, whole-rock major and trace-element geochemical analyses, and Sr–Nd isotopic data for the newly discovered Biluoco volcanic rocks from the southern Qiangtang subterrane, central Tibet. Zircon U–Pb dating reveals that the Biluoco volcanic rocks were crystallized at ca. 95 Ma. The samples are characterized by low SiO 2 (50.26–54.53 wt%), high Cr (109.7–125.92 ppm) and Ni (57.4–71.58 ppm), and a high Mg# value (39–56), which plot in the magnesian andesites field on the rock classification diagram. They display highly fractionated rare earth element patterns with light rare earth element enrichment ([La/Yb] N  = 21.04–25.24), high Sr/Y (63.97–78.79) and no negative Eu anomalies (Eu/Eu* = 0.98–1.04). The Biluoco volcanic rocks are depleted in Nb, Ta and Ti and enriched in Ba, Th, U and Pb. Moreover, the eight samples of Biluoco volcanic rocks display constant ( 87 Sr/ 86 Sr) i ratios (0.70514–0.70527), a positive ε Nd (t) value (2.16–2.68) and younger Nd model ages (0.56–0.62 Ga). These geochemical signatures indicate that the Biluoco volcanic rocks were most likely derived from partial melting of the mantle wedge peridotite metasomatized by melts of subducted slab and sediment in the subducted slab, invoked by asthenospheric upwelling resulting from the slab break-off of the northward subduction of the Bangong–Nujiang oceanic lithosphere. Identification of ca. 95 Ma Biluoco magnesian andesites suggests they were a delayed response of slab break-off of the northward subduction of the Bangong–Nujiang oceanic lithosphere at ca. 100 Ma. [ABSTRACT FROM AUTHOR]

Abstract: Utilizing the Community Climate System Model version 2 from the National Center for Atmospheric Research (NCAR) and the reconstructed paleogeographic data, we simulate East Asian climate in the Late Cretaceous (66Ma) and investigate the impacts of atmospheric CO2 concentration on climate. The simulations show that the large-scale pressure systems and prevailing wind directions showed a remarkable seasonal variation over East Asia at 66Ma, which indicates a monsoon feature over East Asia. The East Asian winter and summer monsoons showed a synchronous variation, that is, a strong (weak) winter monsoon accompanied a strong summer (weak) monsoon. At 66Ma, there was more precipitation over the eastern coasts of Asia and less precipitation in the mid-latitudes of the inland areas, but there was no meiyu rainy belt in the subtropics of the East Asian land like the present climate. Moreover, the simulated Cretaceous climate over East Asia was warmer relative to the present day. Annual mean surface air temperature was higher over Asia at that time and close to the estimation from the geological evidence. In the Late Cretaceous, when atmospheric CO2 concentration is reduced, the East Asia climate has a significant change, with weaker winter and summer monsoons over East Asia. Annual mean surface air temperature and annual total precipitation reduce in most of land and ocean. Negative difference of surface water budget appeared mainly in the eastern part of East Asia, indicating a drier soil surface, while positive differences appeared in the mid‐latitudes of central-western Asia, indicating a wetter soil surface. [Copyright &y& Elsevier]

The International Continental Scientific Drilling Project of Cretaceous Songliao Basin has recovered a complete Cretaceous terrestrial sedimentary record in northeastern China, providing a unique opportunity to understand the terrestrial climate change during the Cretaceous period. In this study, we present high-resolution geochemical records from Members 3 and 4 of the Quantou Formation in the SK-1 South borehole. The findings show that samples from Members 3 and 4 of the Quantou Formation originated from a source area of a homogeneous composition. Most of the samples were sediments that underwent the first round of weathering. The geochemical proxies (Th, CIA, CIW, τ Na) and average value of the CIA proxy indicate that the strata have been subjected to moderate chemical weathering. The weathering intensity trend was divided into four evolutionary stages based on the CIA proxy: the steady lower part (1915–1878 m), the slowly rising lower and middle part (1878–1815 m), the middle and upper part (1815–1800 m) showing the highest values, and the gently fluctuating upper part (1800–1783 m). Precession, obliquity, and short-eccentricity signals were recognized in the proxies of Th, τ Na , corrected CIA, and corrected CIW from Members 3 and 4 of the Quantou Formation, including about seven short-eccentricity cycle periods with a duration of ∼700 ka. The high peaks in short-eccentricity correspond to the high values of Th, corrected CIA, and corrected CIW proxies, and are consistent with the amplitudes of precession signals preserved in τ Na during humid periods. During strong precession, the enhanced seasonal contrasts increased humidity, which intensified chemical weathering. The paleoclimatic pattern of interaction between the monsoon-like system and westerlies in the Cretaceous Songliao Basin may be the underlying interpretation that causes cyclic variation in the chemical weathering proxies in Members 3 and 4 of the Quantou Formation. • Reconstruction of historical chemical weathering using multiple weathering proxies. • Humid climate derived from a non-linear response of the climate system to precession. • Interaction between the monsoon-like system and westerlies may be the interpretation causing cyclic variation. [ABSTRACT FROM AUTHOR]

The Songliao Basin (SLB) in Northeast China has a succession of terrestrial sedimentary deposits that span much of the Cretaceous. The sedimentary records recovered from SLB allow us to investigate the relationship between astronomically forced climate and clastic sediment accumulation in a terrestrial setting from the mid to high latitudes. Here, we compiled high-resolution X-Ray Fluorescence (XRF) datasets (K/Ti, Rb/Sr, Ca/Ti), and gamma ray (GR) logging data from Member 2 of the Nenjiang Formation in the SK-1n borehole. Power spectral analysis of the GR data revealed that sedimentary cycles had wavelengths of 27.4 m, 6.56 m, 2.60 m, and 1.27 m. These wavelengths are interpreted as the orbital cycles of long-eccentricity, short-eccentricity, obliquity, and precession, respectively. We established an astronomical time scale by assuming that the 27.4 m cycles represent ~405 kyr eccentricity. We also applied correlation coefficient (COCO) analysis to identify the astronomical forcing periods. The chemical weathering history was classified by the relative changes of Rb/Sr and K/Ti ratios. The lower Rb/Sr and higher K/Ti values correspond to weak weathering, interpreted as arid periods, and vice versa. Ca/Ti ratios correlate with the humid periods and we attribute this correspondence to a salinity control on Ca/Ti. Furthermore, the unconventional 173-kyr obliquity cycle associated with the secular frequency interference of orbital inclinations between Earth and Saturn was recognized and manifested by humid/arid cliamtic oscillations, suggesting that high obliquity contributed to strengthening the hydrological cycles in SLB and bringing more precipitation and runoff towards the basin. The unique paleogeographic location and the existing paleoclimate simulations of SLB further demonstrated the existence of paleomonsoon variations in East Asia during the Late Cretaceous. • Sedimentation rate from 5.1 to 8.3 cm/kyr was simulated by three proxies. • The chemical weathering suggested humid-arid changes related to the paleomonsoon. • The ~173 kyr cycle was recognized and associated with the humid-arid changes. • High obliquity contributes to strengthening the hydrological cycles in Songliao Basin. [ABSTRACT FROM AUTHOR]

The Songke-1 north (SK-1n) borehole recovered a continuous, 1541.66 m Late Santonian–Early Danian terrestrial succession in Songliao Basin (SB), northeastern China. It provides a unique record for improving our understanding of continental paleoclimate and ecological system in Cretaceous greenhouse world. Here we use thorium (Th) logging data as a paleoenvironmental and paleoclimatic proxy to conduct a detailed cyclostratigraphic study on the SK-1n core. Power spectra, evolutionary fast Fourier transformation and wavelet analysis all reveal significant decameter- to meter-scale sedimentary cycles in the Nenjiang (K 2 n), Sifangtai (K 2 s) and Mingshui (K 2 m) formations. The ratios of cycle wavelengths in these stratigraphic units are ∼20:5:2:1, and are interpreted as Milankovitch cycles of 405 kyr and 100 kyr eccentricity, 38.4 kyr obliquity and 20 kyr precession cycles, respectively. An astronomical time scale (ATS) is established by tuning filtered 405 kyr eccentricity cycles to a target curve of the astronomical solution La2010d based on the magnetostratigraphic time framework of the SK-1n borehole. This ATS provides precise numerical ages for stratigraphic boundaries, biozones, geological and geophysical events, and serves as a basis for correlation of strata and events between marine and terrestrial systems. The Cretaceous/Paleogene (K/Pg), Campanian/Maastrichtian, Santonian/Campanian boundaries are estimated at core depths of 318 m, 752.8 m and 1751.1 m, respectively. A ∼3.8 myr-long hiatus between the Nenjiang (K 2 n) and Sifangtai (K 2 s) formations occurs from 76.1 to 79.9 million years ago. The ages and durations of magnetochrons C33r to C30n are precisely estimated and provide new constraints on the Late Cretaceous Geomagnetic Polarity Time Scale (GPTS) and South Atlantic sea-floor spreading rates. [ABSTRACT FROM AUTHOR]

Abstract: The first complete Early Turonian–Early Campanian lacustrine succession has been recovered from the SK-I south (SK-Is) borehole in the Songliao Basin (SLB), northeastern China. We conducted a detailed cyclostratigraphic study of natural gamma-ray (GR) log, thorium (Th) log, and magnetic susceptibility (MS) data from this core. Spectral analysis of the upper Quantou Formation (K2q3+4), Qingshankou Formation (K2qn), Yaojia Formation (K2y), and lower Nenjiang Formation (K2n1+2) reveals a hierarchy of meter- to decameter-scale cycling in the data. The wavelength ratios of the cycles in these stratigraphic units are ~20:5:2:1, corresponding with those of Milankovitch cycle periods of 405kyr (long eccentricity):100kyr (short eccentricity):37kyr (obliquity):20kyr (precession), indicating astronomical control on sedimentation. An astronomical time scale (ATS) was established by tuning interpreted 405kyr cycles to a 405kyr orbital eccentricity target curve, and to four SIMS U–Pb zircon radioisotope ages. This ‘absolute’ ATS provides precise numerical ages for stratigraphic boundaries, biozones, geological and geophysical events, and serves as a basis for correlation of strata and events between marine and terrestrial systems. The ages of the C33r/C34n geomagnetic polarity boundary in K2n2 and three short reversal events in K2y are estimated as 83.633Ma, 84.819–84.862Ma, 84.982–85.092Ma and 85.240–85.629Ma, respectively. Long-period amplitude modulations in the obliquity and eccentricity bands of the 405-kyr-tuned GR-Th series provide strong evidence that long-period orbital forcing influenced climate change and depositional processes in the SLB. The extracted amplitude modulations provide evidence that the orbits of Earth and Mars were not in secular resonance, and were undergoing chaotic interactions during this time, although the modulations do not match those of recent astronomical models. [Copyright &y& Elsevier]

From the latest Cretaceous (late Campanian to Maastrichtian, ~75–66 Ma) to the earliest Paleogene, fluctuations in greenhouse climate, inferred primarily from marine sediments, have been linked to volcanism, the Chicxulub asteroid impact, and the Cretaceous-Paleogene (K-Pg) mass extinction. In this paper, we summarize terrestrial climate records in mid-latitude East Asia during the latest Cretaceous and across the K-Pg boundary, based on a multi-proxy approach from the geochronologically well-constrained Sifangtai and Mingshui formations (SMF), accessed by scientific drilling of the Songliao Basin in northeastern China. Evolution of sedimentary environments is characterized by five depositional units of fluvial-deltaic-lacustrine facies. Development of four types of paleosols, including Inceptisols, Aridisols, Vertisols and Alfisols, is interpreted to primarily reflect climatic changes. Correlations among sedimentary facies, paleosol features, illite chemistry index, chemical index of alteration, as well as stable and clumped isotopes of pedogenic carbonates and clay minerals of the SMF validate their reliability for paleoclimate reconstruction, and indicate significant fluctuations in terrestrial climate and sedimentary environment. During global warming intervals possibly triggered by volcanism (e.g. ~69.5–68.5 Ma), the Songliao Basin experienced a warmer and wetter climate with stronger terrestrial chemical weathering and more monsoon-derived moisture sourced from the Pacific. In contrast, during global cooling intervals (e.g. ~70.5–69.5 Ma and ~ 68.5–66.5 Ma), the SMF record a cooler and drier climate with less intensive chemical weathering and more westerlies-derived moisture. Across the K-Pg boundary, dramatic changes in land temperatures and hydroclimate correspond to the latest Maastrichtian warming episode (~66.4–66.1 Ma), the transient cooling preceding the K-Pg boundary (~66.1–66.0 Ma), and the earliest Paleogene warming interval (~66.0–65.7 Ma). Temporal correlation of weathering index changes with the Deccan Traps volcanism suggests that volcanism and subsequent intensified weathering played a major role for climatic changes across the K-Pg boundary. The integrated records of sedimentological and geochemical datasets from the Songliao Basin robustly demonstrate that the terrestrial climate of mid-latitude East Asia responded strongly to greenhouse climate changes and to the catastrophic geological events from the latest Cretaceous to the earliest Paleogene. [ABSTRACT FROM AUTHOR]

• Milankovitch cycles were recorded in Rb/Sr series from Member 1 (K 2 n1) and Member 2 (K 2 n2) of the Nenjiang Formation. • K 2 n1 experienced a longer humid period and more pronounced climatic fluctuation than K 2 n2. • The mean sedimentation rates of 6.577 and 8.369 cm/ka for K 2 n1 and K 2 n2 were provided by ASM method. • The collectively regulation of obliquity and precession amplified the paleomonsoon effect during humid periods in K 2 n1 and K 2 n2. Cretaceous terrestrial sedimentary records are crucial for our understanding of geological systems' responses to past climate change under greenhouse condition. Numerous publications have documented that Milankovitch cycles were a dominant climate driver over multi-millennial timescales. However, most of these orbital signals were derived from marine records obtained during the Cenozoic geological period, whereas knowledge of Milankovitch cycles preserved in lacustrine sediments prior to the Cenozoic is limited due to the lack of a precise chronological framework, poor preservation rate of terrestrial sediments, limited records, and fewer experts in this research area. This paper reports high-resolution X-ray fluorescence (XRF) elemental records of K, Ti, Rb, Sr, Zr, Zr/Rb, Rb/Sr, and K/Ti from Member 1 (k 2 n1) and Member 2 (k 2 n2) of the Nenjiang Formation, which were obtained from a near-continuous SK-2 East (SK-2e) borehole drilled in the Songliao Basin (SB) of northeastern (NE) China. Variations of the elemental records reveal a humid-arid-humid-semiarid climatic evolution throughout the deposition of k 2 n1 and a humid-arid-humid-arid climatic variation throughout the deposition of k 2 n2. In this context, K 2 n1 experienced a relatively longer humid period and more pronounced climatic fluctuation than K 2 n2. A method of average spectral misfit (ASM) was adopted to successfully identify two optimal sedimentation rates of 6.577 and 8.369 cm/ka for K 2 n1 and K 2 n2, respectively. Based on these two sedimentation rates, nearly all significant Milankovitch cycles preserved in the Rb/Sr record were recognized. It is suggested that westerly wind was the main climatic driving factor of climate evolution in the SB under the forcing of Milankovitch cycles. The collectively regulation of obliquity and precession increased the seasonal contrasts during humid periods in the Nenjiang Formation and thereby amplified the paleomonsoon effect, thus bringing more moisture towards the SB and lead to enhanced rainfall. [ABSTRACT FROM AUTHOR]