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.
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•A hierarchical climate paleogeography knowledge graph is established.•The strengths and weaknesses of the 5 paleoclimate classifications are evaluated.•The concepts of ...paleoclimatology through the Late Cretaceous are unified.
The climate paleogeography, especially the climate classifications, helps to interpret the global and regional climate changes and intuitively compare the climate conditions in different regions. However, the application of climate classification in deep time (i.e., climate paleogeography) is prohibited due to the usually qualitatively constrained paleoclimate and the inconsistent descriptions and semantic heterogeneity of the climate types. In this study, a climate paleogeography knowledge graph is established under the framework of the Deep-Time Digital Earth program (DDE). The hierarchical knowledge graph consists of five paleoclimate classifications based on various strategies. The classifications are described and their strengths and weaknesses are fully evaluated in four aspects: “simplicity, applicability, quantifiability, and comparability”. We also reconstruct the global climate distributions in the Late Cretaceous according to these classifications. The results are compared and the relationships among these climate types in different classifications are evaluated. Our study unifies scientific concepts from different paleoclimate classifications, which provides an important theoretical basis for the application of paleoclimate classifications in deep time.
Deserts are among the most important terrestrial sedimentary environments and have existed in all periods throughout Earth’s history. In contrast to modern deserts, the ability to quantitatively ...evaluate the area and desertification degrees of ancient deserts is limited due to the lack of unambiguous proxies. Dune morphology and their spatial arrangements directly reflect the degree of desertification of deserts. Recently, a methodology for obtaining the morphological parameters of dunes was established, although it has not been applied to ancient dunes and deserts in deep time. In the Ordos Basin, both the Early Cretaceous desert and modern deserts (Hobq Desert and Mu Us Desert) were well developed and exposed, which makes the Ordos Basin an ideal place to quantitatively evaluate the paleo-desert based on the proposed methodology. In this study, a total of 698 and 1,490 morphological parameters reflecting the Early Cretaceous desert and modern deserts in the Ordos Basin were obtained, respectively. For the Ordos paleo-desert, our results show that its area was larger and its degree of desertification was more severe than those of modern mid-latitude deserts, including the modern desert in the Ordos Basin, but were similar to those of the modern low-latitude deserts. Our results, therefore, suggest that the Ordos paleo-desert was a non-negligible and large desert during an interval of Earth’s history. Since the other controlling factors, such as regional geography and sources of both the ancient and modern deserts in the Ordos Basin, have remained nearly unchanged, we speculate that it may have been the relatively high temperature, high levels of atmospheric carbon dioxide and relatively low precipitation during the greenhouse period (i.e., Early Cretaceous) that led to the large area and severe degree of desertification of the Ordos paleo-desert.
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•Clumped isotope paleothermometry is applied to paleosol in the Liuqu Conglomerate.•The estimated maximum burial temperature of the Liuqu Conglomerate is ∼97 °C.•The maximum burial ...depth of the Liuqu Conglomerate was up to 3.7–4.3 km.•The model of outward growth of the Tibetan Plateau is preferred.
The Liuqu Conglomerate, exposed along the Yarlung Zangbo suture zone (YZSZ) in southern Tibet, archives not only the process of the India-Asia collision, but also the exhumation history of the India-Asia collision zone. The burial and exhumation history of the Liuqu Conglomerate thus could potentially provide clues to the India-Asia collision and orogeny. Low-temperature thermochronometric data indicate that maximum burial temperatures of the Liuqu Conglomerate ranged from 80 to 110 °C; however, the exact burial history is not well constrained. Here, we examine the burial conditions of the Liuqu Conglomerate by applying clumped isotope thermometry to paleosol carbonates. Extensive microcrystalline recrystallization indicates that the samples have been diagenetically altered during burial. Moreover, the clumped isotope temperatures (ranging from ∼48 to ∼97 °C) are clearly above Earth surface conditions, indicating the original climatic information was overwritten by alteration at higher burial temperatures. Nevertheless, the calculated diagenetic water δ18O values represent maximum meteoric water values that can be used to broadly constrain the paleoelevation. The highest clumped isotope temperature implies that the maximum burial temperature of the Liuqu Conglomerate was at least ∼97 °C. We conclude that the Liuqu Conglomerate was buried as deeply as 3.7–4.3 km during the latest Paleocene to Eocene, and then exhumed during the Miocene (∼10–12 Ma). Incision of the paleo-Yarlung River was likely responsible for erosion and exhumation of the Liuqu Conglomerate, which suggests that the drainage system of Paleo-Yarlung River was similar to that of today and supports the model of outward growth of the Tibetan Plateau.
In deep time, climates are mainly classified by climatically sensitive deposits, paleontological evidences, and modeling. However, they only have limited applicability in deep time studies. Here, we ...propose a new paleoclimate classification based on the widely used Köppen climate classification. The proposed new classification is simple and quantitative, but bridges the gap between modern and deep time climate studies. The new classification is closely related to but differs from that of Köppen by changing some limits. A world map using the new classification shows the same patterns as the world map of the Köppen climate classification. Using the new classification, we are able to solve a long-standing problem about the climates of East Asia during the Eocene. We found that East Asia shared the same climate type (Ca: Subtropical) at all studied locations, supporting the hypothesis of monsoon or monsoon-like climate that prevailed there during the Eocene.
•We propose a new paleoclimate classification for deep time.•It is a simplification of the complex modern climate classification.•The new classification indicates monsoon climate in East Asia during Paleogene.
The results of detailed studies on the beam quality of a non-chain pulsed electric discharged DF laser based on a compact inner cavity confocal positive branch unstable resonator were presented ...herein. The theoretical and experimental divergence angles for magnification M = 1.65, 1.85, 2.05, and 2.25 were calculated according to Fraunhofer diffraction and measured by the method of calibrated apertures. The smallest divergence of θ = 0.66 mrad was obtained with M = 2.25 in our experiment, which is 1.95 times the theoretical value. The corresponding far-field energy density at 10 km distance from the laser exit was 82.8 mJ/m2. The beam quality and energy density were increased by 11 and 91 times, respectively, compared with a similar stable resonator in our lab.
Nanotechniques for curcumin (Cur) encapsulation provided a potential capability to avoid limitations and improve biological activities in food and pharmaceutics. Different from multi-step ...encapsulation systems, in this study, zein-curcumin (Z-Cur) core-shell nanoparticles could be self-assembled within Eudragit S100 (ES100) fibers through one-pot coaxial electrospinning with Cur at an encapsulation efficiency (EE) of 96% for ES100-zein-Cur (ES100-Z-Cur) and EE of 67% for self-assembled Z-Cur. The resulting structure realized the double protection of Cur by ES100 and zein, which provided both pH responsiveness and sustained release performances. The self-assembled Z-Cur nanoparticles released from fibermats were spherical (diameter 328 nm) and had a relatively uniform distribution (polydispersity index 0.62). The spherical structures of Z-Cur nanoparticles and Z-Cur nanoparticles loaded in ES100 fibermats could be observed by transmission electron microscopy (TEM). Fourier transform infrared spectra (FTIR) and X-ray diffractometer (XRD) revealed that hydrophobic interactions occurred between the encapsulated Cur and zein, while Cur was amorphous (rather than in crystalline form). Loading in the fibermat could significantly enhance the photothermal stability of Cur. This novel one-pot system much more easily and efficiently combined nanoparticles and fibers together, offering inherent advantages such as step economy, operational simplicity, and synthetic efficiency. These core-shell biopolymer fibermats which incorporate Cur can be applied in pharmaceutical products toward the goals of sustainable and controllable intestine-targeted drug delivery.
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