【摘 要】
：
The Silurian-Devonian interval is an essential period in Earth history for witnessing the rise of sarcopterygian fishes and terrestrial vascular plants.In addition to its implication in global stratigraphic correlation,the precise location of the Silurian
【机 构】
：
Key CAS Laboratory of Vertebrate Evolution and Human Origins,Institute of Vertebrate Paleontology an
论文部分内容阅读
The Silurian-Devonian interval is an essential period in Earth history for witnessing the rise of sarcopterygian fishes and terrestrial vascular plants.In addition to its implication in global stratigraphic correlation,the precise location of the Silurian-Devonian boundary(SDB)in East Yunnan closely relates to the minimal and maximal estimated dates for the lungfish-tetrapod split.Several geochemical indicators including the values and curves of δ13Corg,δ13Ccarb and TOC are obtained from the continuous SDB sequence in Dahe,Yiliang County,East Yunnan.The results reveal the significant positive δ13Corg shifts in the upper part of the Yulungssu Formation and the lower part of the Xishancun Formation,and the peak value(-20.0‰)in the sample YD-25 from the lowermost of the Xishancun Formation,replicating the δ13Corg variation trend from the uppermost Silurian to the lowermost Devonian worldwide.The δ13Corg variation across the SDB at the Dahe Section resembles the SDB curve from the borehole Klonk-1 drilled at the top of the Klonk GSSP in the Prague Basin,Czech Republic.As such,we place the SDB in the Dahe Area between the samples of YD-17 and YD-18 from the lowermost part of the Xishancun Formation.This SDB assignment is corroborated by new findings of Early Devonian thelodont Parathelodus from the lower part of the Xishancun Formation in Qujing Area.The resolution of the SDB in Dahe,coupled with available paleontological data and the biostratigraphic zonation in East Yunnan,has provided vital data for the geological ages of the fish-bearing strata in East Yunnan.The earliest rhipidistian Youngolepis from the Xishancun Formation(Lochkovian,Devonian)and earliest stem-sarcopterygian Psarolepis from the Kuanti Formation(Ludfordian,Silurian)in East Yunnan indicate that the split between lungfish and tetrapods occurred between 426.5 and 416.0 Ma.
其他文献
Although alpine ecosystems have been commonly recognized as sensitive to recent climate change,few studies have examined its impact on the long-term productivity of vegetation and soil erosion.Using paleoecological records,these two aspects were examined
Terahertz(THz)multiuser massive multiple-input multiple-output(MIMO)has been envisioned as a promising technique to support massive connectivity in next-generation wireless networks.However,due to ultra-high frequency band,the path attenuation of THz chan
Software defined networking(SDN)and network function virtualization(NFV)as new tech-nologies have shown great potential in improving the flexibility of resource management for network service provisioning.As traffic dynamics may cause violation of rigid s
In this paper,we investigate a user scheduling algorithm for massive multiple-input multiple-output(MIMO)systems over more general correlated Rician fading channels.To achieve low latency and high throughput,a new user scheduling algorithm based on deep l
Recent studies have revealed that long-term financial news can affect stock markets.However,previous research mainly focuses on modeling the short-term effects of financial news and suffers from the weak ability of quantifying the time-decaying influence
Emerging non-volatile memory (NVM) technologies promise high density,low cost and dynamic random access memory (DRAM)-like performance,at the expense of limited write endurance and high write energy consumption.It is more practical to use NVM combining wi
Reconfigurable intelligent surface(RIS),one of the key enablers for the sixth-generation(6G)mobile communication networks,is considered by designers to smartly reconfigure the wireless propagation environment in a controllable and programmable manner.Spec
A robust static output feedback(SOF)Stackelberg game with multiple followers in stochastic linear parameter varying(LPV)systems is investigated.The conditions for the existence of a robust SOF Stackelberg strategy set under H∞ constraints are established
Introducing reconfigurable intelligent surfaces(RISs)greatly improves the wireless propagation environment.Limited to feedback overheads and computing power,the low-complexity precoding and the cost-effective beamforming implementation are urgently demand
Flying ad hoc networks are used for many critical tasks.The network formation for routing data becomes difficult because of the mobility of unmanned aerial vehicles(UAVs).To solve the communication issue,we propose an intelligent cluster routing scheme fo