The timing of formation of the low‐gradient, internally drained landscape of the Tibetan Plateau is fundamental to understanding the evolution of the plateau as a whole. Well‐dated sedimentary ...records of internal drainage of rivers into lakes are used to reveal the timing of this evolution. Here we redate the youngest continental sedimentary successions of central Tibet in the Lunpola Basin and propose a new age range of ca. 35 to 9 Ma, significantly younger than previously thought. We demonstrate long‐standing internal drainage in central Tibet since the late Eocene and stable sedimentary environments, source regions, and low topographic relief since at least the early Miocene. We suggest that sediment aggradation of internal drainage and reduction of hillslope gradients by erosion dominate the formation of low‐relief landscapes and that the late Cenozoic drainage basins in central Tibet developed in response to flow in the lower crust and/or mantle lithosphere.
Plain Language Summary
Internal drainage of rivers into lakes is a characteristic of the high plateaus of the world and, most notably, the Tibetan Plateau. Internal drainage generates local perched base levels for Tibetan rivers, enabling geomorphic isolation from the rapidly incising rivers of the Himalaya and surrounding regions. However, the question of when the low‐relief plateau topography was initiated has been largely ignored, and its formation mechanism is controversial. Here we report a detailed investigation in the Lunpola Basin of central Tibet and propose a new depositional age range of ca. 35–9 Ma. We demonstrate that the internal drainage kept eroding the mountain ranges and filling the surrounding lowlands since at least the late Eocene. By no later than the early Miocene, a gentle landscape formed in central Tibet. The late Cenozoic basins in central Tibet developed in response to deep crustal or mantle flow and associated upper crustal deformation.
Key Points
Robust age constraints of the youngest continental stratigraphic unit from the Lunpola Basin in central Tibet are reported
Aggradation and erosion of internal drainage dominated the formation of low‐relief topography in central Tibet by the early Miocene times
Late Cenozoic drainage basins in central Tibet developed in response to flow in the lower crust and/or mantle lithosphere
The Jurassic is a crucial greenhouse period that witnessed a transition from the relatively colder Triassic to the relatively warmer Cretaceous. However, previous studies based on marine sections ...suggest different long-term paleotemperature trends throughout the Jurassic. Oxygen isotope (ẟ18O) values of temperate belemnite and bivalve fossils suggest a general cooling followed by a general warming trend during the Jurassic, whereas TEX86H and clumped isotope sea surface temperature records available for parts of this period appear consistent with a relatively warm and stable climate. The paucity of Middle Jurassic paleotemperature estimates limits efforts to investigate the above disagreement. Here, we apply clumped isotope (Δ47) thermometry to paleosol carbonates from the central part of East China to reconstruct terrestrial paleotemperatures and paleoatmospheric CO2 (pCO2) in the Middle Jurassic. After evaluating potential burial diagenesis and seasonality of soil carbonate accumulation, we suggest that terrestrial mean annual temperatures ranged from 30 ± 4 °C to 34 ± 4 °C and the estimated mean pCO2 was 1219 ± 519 ppmv in mid-latitude East China during the Middle Jurassic. Based on the compiled marine temperatures and our results, we conclude that the paleoclimate was relatively warm and stable from the Middle Jurassic to at least the Earliest Cretaceous (ca. 180–135 Ma). Our estimated Middle Jurassic pCO2 aligns with previous records, revealing minimal variations compared to the pCO2 observed during the Early Cretaceous. These findings imply a link between the consistent temperatures and the relatively stable pCO2 levels from the Middle Jurassic through the Early Cretaceous.
•We analyze clumped isotopes of paleosol carbonates in mid-latitude East China.•The mean annual terrestrial temperatures were 30–34 °C during the Middle Jurassic.•The eatimated pCO2 was 1219 ± 519 ppmv during the Middle Jurassic.•Our results are broadly consistent with coeval sea surface temperatures and pCO2.•The paleoclimate was relatively warm and stable during ca. 180–135 Ma.
As CO2 keeps emitting, it is urgent to project future climatic changes by quantitatively reconstructing deep time paleoclimate in high atmospheric CO2 concentrations. However, there are still ...unneglected discrepancies between the terrestrial temperatures based on the climatic proxies and climate models, especially at low latitudes, which limits our interpretation of the terrestrial responses to global climate changes at low latitudes. In this study, the clumped isotope concentrations (Δ47) and total mercury signals are analyzed for the uppermost Cretaceous-lowermost Paleogene strata in the low-latitude Nanxiong Basin, South China. After excluding the potential diagenesis by both recrystallization and solid-state reordering, our study presents an extremely high mean annual terrestrial temperature of ca. 30 °C in the low latitudes. Our result is significantly higher than the previous estimates and supports a hot and expanded tropics during the latest Cretaceous-earliest Paleocene (i.e., K-Pg boundary interval). In addition, we suggest that the hot climate was plausibly caused by Deccan Traps (DT) volcanism, although the mercury concentrations in the section show relatively low peaks during the main eruptions. We speculate that the mercury sequestration in the Nanxiong Basin may have been affected by the extremely hot and arid regional climate.
•We analyze clumped isotopes and total mercury signals in low-latitude Nanxiong Basin.•The mean annual terrestrial temperature was ∼30 °C during the K-Pg boundary interval.•The low-latitude continents were extremely hot during the K-Pg boundary interval.•The mercury sequestration may had been affected by the hot and arid climate.
In parallel with pronounced cooling in the oceans, vast areas of the continents experienced enhanced aridification and restructuring of vegetation and animal communities during the Late Miocene. ...Debate continues over whether pCO2-induced global cooling was the primary driver of this climate and ecosystem upheaval on land. Here we present an 8 to 5 Ma land surface temperatures (LST) record from East Asia derived from paleosol carbonate clumped isotopes and integrated with climate model simulations. The LST cooled by ~7 °C between 7.5 and 5.7 Ma, followed by rapid warming across the Miocene–Pliocene transition (5.5 to 5 Ma). These changes occurred synchronously with variations in alkenone and Mg/Ca-based sea surface temperatures and with hydroclimate and ecosystem shifts in East Asia, highlighting a global climate forcing mechanism. Our modeling experiments additionally demonstrate that pCO2-forced cooling would have altered moisture transfer and pathways and driven extensive aridification in East Asia. We, thus, conclude that the East Asian hydroclimate and ecosystem shift was primarily controlled by pCO2-forced global cooling between 8 and 5 Ma.
In parallel with pronounced cooling in the oceans, vast areas of the continents experienced enhanced aridification and restructuring of vegetation and animal communities during the Late Miocene. ...Debate continues over whether
CO
-induced global cooling was the primary driver of this climate and ecosystem upheaval on land. Here we present an 8 to 5 Ma land surface temperatures (LST) record from East Asia derived from paleosol carbonate clumped isotopes and integrated with climate model simulations. The LST cooled by ~7 °C between 7.5 and 5.7 Ma, followed by rapid warming across the Miocene-Pliocene transition (5.5 to 5 Ma). These changes occurred synchronously with variations in alkenone and Mg/Ca-based sea surface temperatures and with hydroclimate and ecosystem shifts in East Asia, highlighting a global climate forcing mechanism. Our modeling experiments additionally demonstrate that
CO
-forced cooling would have altered moisture transfer and pathways and driven extensive aridification in East Asia. We, thus, conclude that the East Asian hydroclimate and ecosystem shift was primarily controlled by
CO
-forced global cooling between 8 and 5 Ma.
•A hybrid deep learning approach was proposed for multi-attribute data.•Data with different formats were processed by specific neural units.•Temporal and spatiotemporal relations were captured by the ...proposed model.•The model had small errors in train delay prediction.•The model was robust for modeling complex data with different sizes and dimensions.
Dynamical systems that contain moving objects generate multi-attribute data, including static, time-series, and spatiotemporal formats. The diversity of the data formats creates challenges for the accurate modeling of these systems, for example, the state/location/trajectory prediction of moving objects. We developed a deep learning (DL) approach that combines 3-dimensional convolutional neural networks (3D CNN), long short-term memory (LSTM) recurrent neural network, and fully-connected neural network (FCNN) architectures to address this problem. The proposed model, named CLF-Net, uses individual factors with different attributes as input to achieve better predictions. The spatiotemporal features are fed into the 3D CNN, the time-series variables are fed into the LSTM, and the non-time-series factors are fed into the FCNN, respectively. A case study of train delay prediction for four railway lines with different operational features shows that the CLF-Net outperforms conventional machine learning models and the state-of-the-art DL models with regard to the performance metrics of the root mean squared error and mean absolute error.
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•The N-species in NG-T can be fine-tuned by the pyrolysis conditions, facilitating differentiating functions among different N-species.•The C atoms next to the graphitic-N species ...serves as active sites for efficient CO2 conversion.•The optimized catalyst is capable of achieving a selectivity of 95.0 % in converting CO2 into CO, comparable to the metal-based catalysts.
For metal-free nitrogen(N)-doped carbon catalysts, diverse N-bearing species embedded in the carbon framework are generally regarded as chemical promoters that can upgrade their catalytic performance for CO2 electroreduction reaction (CO2RR). However, it is still a controversy as to which N species plays a dominant role. Herein, a type of large surface area (371 m2/g), N-rich (11.0 wt%) graphene-like carbon electrocatalyst (NG-1000) is fabricated via facile pyrolysis from a precursor composite of dicyandiamide and phthalocyanine. The N-species in the NG-T (T = 700–1000 °C) can be fine-tuned, thus facilitating differentiating functions of the various N-species. Based on the comprehensive analysis of original Pc/CNTs and NG-T catalysts, we identified that the C atoms next to the graphitic-N species in NG-1000 serves as the main active species for CO2RR. In addition, such a non-metal based electrocatalyst is capable of achieving an excellent selectivity of 95.0 % at −0.72 V versus RHE to convert CO2 into CO, with a CO current density of 9.07 mA cm−2, comparable to the state-of-the-art metal-based electrocatalysts.
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