| As an important transformation period in geological history,the Late Permian witnessed environmental changes before and after two biological extinction events,of which paleoclimate was a key influence on the two extinction events,but the current paleoclimate studies in this period mainly focus on the vicinity of the two extinction events,and lack of attention to the evolution of the Late Permian paleoclimate,and the paleoclimate changes in this period and the evolution of the Earth system,especially with the orbital perihelion period The relationship between paleoclimate changes and the evolution of the Earth system during this period,especially during the orbital cycle,deserves in-depth attention.The Western Guizhou region,which is part of the South China plate during the Late Permian,is an ideal area to study the Late Permian paleoclimate changes and its evolutionary mechanisms because of its continuous development of the Late Permian coal system.Therefore,based on the theories and methods of petrology,cyclic stratigraphy,paleoclimatology,and stratigraphic stratigraphy,this paper combines data from more than 20 boreholes and four field sections in Western Guizhou area,as well as the geophysical,mineralogical and geochemical characteristics of typical boreholes,to carry out a study on the palaeoenvironmental changes,sedimentary sequence evolution,chronostratigraphy,paleoclimatic spatial and temporal evolution of the Late Permian coal system in Western Guizhou and its coupling relationships with geological events,sea level changes,and astronomical orbits.The palaeoenvironmental changes,sedimentary sequence evolution,chronostratigraphy,paleoclimate spatial and temporal evolution and their coupling with geological events,sea level changes and astronomical orbits were studied,and the evolution of the Late Permian paleoclimate in the study area and the influence of the Earth system on paleoclimate in different periods were discussed.In terms of sedimentary environment,three major lithologic types of sandstone,mudstone,and limestone,as well as three sedimentary types of carbonate tidal ping,barrier-lagoon,and shallow water delta,were identified in the Late Permian coal system of the study area,and the sedimentary evolution of the four phases of the Late Permian in the study area was discussed.In terms of cyclic stratigraphy,the astronomical age scale of the Late Permian coal system in the study area was established by extracting the frequency of stable long eccentricity cycles in each sequence using PC sequences incorporating various types of paleoclimate information as the basic sequence,4 types of indicators containing different paleoclimate information as the tuning sequence,and reliable zircon ageing results of specific layers as the constraint.Based on the vertical changes of typical rock types,paleontological assemblages,geochemical characteristics and clay mineral contents,four paleoclimatic types,mainly warm and humid,with small climate fluctuations and relatively hot top and bottom,were distinguished in the Late Permian coal system in the study area.The paleoclimate of Western Guizhou also has a consistent trend of change.As for the astronomical driving mechanism,through the framework of geological events of the Late Permian coal system in the study area,the construction of the sea level change model and the energy ratio of orbital cycles in different stages,it is inferred that there is a certain coupling relationship between various types of evolution of the Earth system.The mechanism of paleoclimate evolution in the Late Permian of Western Guizhou.The paper has 35 figures,10 tables,and 135 references... |
