@秦楚刊号
The Quaternary is the latest geological epoch in the history of the earth, which began about 2.6 million years ago and has continued to the present; during this period, the earth's climate, environment, and biology have undergone significant changes; China, as one of the countries in the world with complex geological conditions and diverse landforms, has particularly prominent Quaternary geological characteristics. China has a vast territory, complex and diverse topography, from plateaus to plains, from mountains to basins, and all kinds of geological environments, which provide a rich material basis for the development and evolution of Quaternary geological processes.
1. The division of Quaternary geological time
(1) Basis for the division of geological time
The classification of Quaternary geological age is mainly based on the characteristics of stratigraphy, sediments, paleontology, paleoclimate, etc. Stratigraphic characteristics are the basis for dividing geological ages, and the boundaries of different geological epochs can be preliminarily determined through the accumulation sequence, thickness changes, lithological characteristics, etc. of strata strata; sediment characteristics are an important basis for dividing geological epochs, and changes in paleoenvironment and paleoclimate can be inferred through the types, compositions, and structures of sediments; paleontological characteristics are the auxiliary basis for dividing geological epochs. Paleoclimatic characteristics are an important reference for the division of geological time, and the impact of climate change on the division of geological time can be revealed through the analysis of paleoclimate records.
Fig. 1: Quaternary comprehensive stratigraphic chronological framework of China
(2) The division of Quaternary geological time
1. Pleistocene
The Pleistocene was the main period of the Quaternary and was characterized by the alternation of warm and cold climates and the emergence of glacial ages. In China, the Pleistocene is divided mainly according to the alternation of glacial and interglacial periods and the corresponding changes in the sedimentary environment. According to the characteristics of the glacial period, the Pleistocene can be divided into multiple glacial and interglacial periods, such as the Dali glaciation, the Lushan glaciation, the Dagu glaciation, etc. The occurrence of these ice ages is closely related to global climate change and reflects the complexity and sensitivity of the Earth's climate system.
(1) Early Pleistocene: This period is mainly characterized by glacial-interglacial cycles, with large climate fluctuations and various sediment types, including moraine and fluvial facies deposits.
(2) Middle Pleistocene: During this period, the climate deteriorated further and glacial activity intensified, forming extensive ice sheets and ice edge landforms. At the same time, human ancestors began to appear and gradually develop in the Chinese region.
(3) Late Pleistocene: During this period, the climate gradually warmed, glaciers began to retreat, and lake and fluvial facies deposits developed extensively. Human culture began to sprout and develop rapidly, forming a rich prehistoric cultural site.
Figure 2: Human evolutionary development
2. Holocene
The Holocene is a geological epoch after the Pleistocene, characterized by a relatively stable climate and a gradual increase in human activity. In China, the Holocene is classified mainly according to the type and distribution of sediments and the remains of human activity. Holocene sediments mainly include loess, fluvial sediments, lacustrine sediments, etc., which record climate change and environmental evolution since the Holocene. At the same time, the Holocene is also an important period in the development of human culture, and through archaeological excavations and records of historical documents, we can understand the trajectory of human activities and cultural characteristics in this period.
The Holocene was the last period of the Quaternary Period, and it was also a period of rapid development of human civilization. During this period, the climate was relatively stable, suitable for human habitation and agricultural development. At the same time, with the intensification of human activities, the impact on the natural environment is gradually emerging.
Figure 3: Quaternary geological map of China
2. Quaternary sedimentation and environment
(1) The type and distribution of Quaternary sediments
The Quaternary sediments in China are rich in types, including loess, fluvial sediments, lacustrine sediments, glacial sediments, and aeolian sediments. These sediments are spatially distributed, reflecting the climatic, topographical, and geomorphological conditions of different regions during the Quaternary period. Loess is mainly distributed in the Loess Plateau and is a typical representative of aeolian sedimentation (loess and aeolian sand are distributed in the arid-semi-arid areas of Northwest China; the Lower and Middle Pleistocene loess is thick and is hydro-aeolian-aeolian; the Upper Pleistocene-Holocene is dominated by aeolian formation, and the formation of loess needs to go through the late carbonate stage.
The development of deserts and Gobi in the early and middle Pleistocene was very limited; in the late Pleistocene, large areas of desert were formed in the northwest region); fluvial sediments were widely distributed in major river basins, recording the evolution history of rivers; lacustrine sediments were mainly distributed in inland lake areas, reflecting the hydrological changes and environmental evolution of lakes (in the early Pleistocene, lacustrine sediments developed, such as Qaidam Ancient Lake, Sanmenxia Ancient Lake, Large lakes were developed in the ancient lakes of Xigeda and Dongting Lake, and in the late period, they were gradually replaced by fluvial sediments, while glacial sediments were mainly distributed in alpine areas, which are important records of glacial activity.
(2) The relationship between Quaternary sediments and the environment
There is a close relationship between Quaternary sediments and the environment. On the one hand, the type, composition and structure of sediments are controlled by environmental conditions, such as climate, topography, landform and other factors. On the other hand, the sediment itself also records the change information of the environment, and by analyzing the physical properties, chemical composition, biological fossils, etc. of the sediment, it is possible to reveal the history of climate and environmental evolution in the past.
1. Sediment-climate relationship
The alternation of warm and cold climates in the Quaternary had a profound impact on the formation and distribution of sediments. During the glacial period, the climate was cold and dry, and glacial activity was frequent, forming a large number of glacial deposits, while during the interglacial period, the climate was warm and humid, and rivers, lakes and other water bodies were active, forming rich river sediments and lake deposits. Through the analysis of these sediments, the change law of paleoclimate can be revealed, which provides an important reference for understanding modern climate change.
2. Sediment-to-geomorphological relationship
The evolution of Quaternary landforms is closely related to the formation of sediments. Under the action of tectonic movements, the terrain fluctuates, providing space for the accumulation of sediments. At the same time, the accumulation of sediments also affects the morphology of the landform. For example, the accumulation of loess has formed a unique loess plateau landform, river erosion and accumulation have shaped the river landform, and glacial landform has been formed by glacial erosion and accumulation. Therefore, through the study of sediments, the evolutionary history of the landform can be revealed.
3. Sediment-ecological relationship
A large number of paleontological remains and relics have been preserved in the Quaternary sediments, and these biological information reflect the characteristics of the paleoecological environment. For example, pollen in lake sediments records the succession of paleovegetation, while fossils in river sediments reveal the distribution and migration patterns of paleozoa. Through the analysis of these biological information, we can understand the changes of the paleoecological environment and provide a scientific basis for modern ecological protection and restoration.
(3) Genesis and environmental evolution of Quaternary sediments
The genesis of Quaternary sediments is closely related to environmental evolution. The genesis of loess is mainly affected by wind and climate change, and its accumulation process records the fluctuation and evolution of paleoclimate; the formation of fluvial sediments is related to the hydrodynamic conditions of rivers and the geological environment in the basin, and its changes reflect the evolution of river systems and the shaping of landforms; and lake sediments are affected by lake water level, Affected by various factors such as water quality and human activities in the basin, the sedimentary sequence records the evolution of the lake environment and the impact of human activities; glacial sedimentation is the product of glacial movement and melting, and its distribution and characteristics reflect the scope and intensity of glacial activity; and coastal sedimentation is affected by various factors such as ocean dynamics, sea level change and human activities, and its changes record the changes of the marine environment and the transformation of the coastal zone by human beings.
The Quaternary environmental evolution in China was affected by a variety of factors, including climate change, tectonic movements, and human activities. In terms of climate change, the onset of glacial periods and the alternation of interglacial periods have had a profound impact on the environment. During ice ages, temperatures drop, glaciers expand, and sea levels fall, leading to significant changes in the environment. During the interglacial period, the climate is relatively warm and humid, which is conducive to the growth and reproduction of organisms. Tectonic movements also have an important impact on the environment, such as the rise and fall of the earth's crust, fractures, etc., which will change the topography and sedimentary environment. Human activities are one of the important factors in the evolution of the Quaternary environment, with the development of human society, the transformation and utilization of the natural environment are becoming more and more intense, resulting in significant changes in the environment.
3. Quaternary glaciers and climate
(1) Distribution and characteristics of Quaternary glaciers
The Quaternary glaciers in China are widely distributed and diverse, including mountain glaciers, ice caps, ice sheets and other types. Among them, the glaciers in the Qinghai-Tibet Plateau and its surrounding areas are the most developed and large-scale, which have a profound impact on the local climate and ecological environment.
On the Qinghai-Tibet Plateau, glaciers are widely distributed in the Himalayas, Kunlun Mountains, Qilian Mountains and other mountain ranges, forming a spectacular glacial landscape. These glaciers are known for their large accumulation area, small melting area, and slow movement speed, which play an important role in local water conservation, river recharge, and ecological balance. In addition, there are also a certain number of glaciers in the Tianshan, Altai Mountains, Qinling Mountains and other mountain ranges, although they are smaller, but they also have a significant impact on the local climate and environment.
The characteristics of China's Quaternary glaciers are mainly manifested in the following aspects: first, the glaciers are huge in scale and have accumulated a large amount of ice and snow materials, which provide a steady stream of water for the local rivers; second, the glaciers are active in their movements, constantly shaping the surface morphology, forming a unique glacial landform; third, glaciers are sensitive to climate change, and their advance and retreat changes are often closely related to climate fluctuations.
(2) The interrelationship between glaciers and climate in the Quaternary period
There is a close correlation between the Quaternary glaciers and the climate in China. On the one hand, the development and distribution of glaciers are controlled by climatic conditions, and on the other hand, the evolution and retreat of glaciers also have an impact on the climate.
First of all, climatic conditions play a decisive role in the development and distribution of glaciers. In cold, dry climates, glaciers are formed and expand due to greater snowfall than melt, while in warm, humid climates, snowfall decreases and melt increases, and glaciers retreat. Therefore, the distribution and size of Quaternary glaciers in China are closely related to the climatic conditions at that time.
Secondly, the advance and retreat of glaciers also have an impact on the climate. When glaciers expand, large amounts of snow and ice cover the surface, reflecting more solar radiation, causing surface temperatures to drop, and at the same time, fresh water from melting glaciers is injected into the oceans, affecting ocean circulation and global climate. Conversely, when glaciers retreat, the surface is exposed, absorbing more solar radiation, leading to higher surface temperatures, while melting glaciers produce less fresh water and have a correspondingly less impact on ocean circulation and global climate.
In addition, the interaction between glaciers and climate manifests itself in other ways. For example, glacial meltwater provides a continuous source of water for rivers, affecting the hydrological characteristics and ecological environment of rivers, while glacial changes also affect regional precipitation distribution and atmospheric circulation patterns.
Fourth, Quaternary geomorphology and tectonics
(1) Quaternary landform types and their characteristics
The Quaternary landforms in China are rich and diverse, mainly including mountains, plateaus, basins, plains, rivers and lakes. These landform types show different distribution characteristics in space, reflecting the complex geological tectonic background and climatic environment in China.
Mountains and plateaus are an important part of China's Quaternary landforms. The Qinghai-Tibet Plateau, the Tianshan Mountains, the Qinling Mountains and other terrains are towering, the climate is cold, and the glaciation is strong, forming a unique glacial landform. The geomorphology of these areas is diverse, including glacial troughs, moraines, and glacial erosion landforms, which provide rich materials for the study of Quaternary glaciation.
Basins and plains are mostly found in the eastern and central regions of China. The Sichuan Basin, the North China Plain and other places have flat terrain, mild and humid climate, and the river action is significant, forming river landforms and lake landforms. The river landforms in these areas include alluvial fans, alluvial fans, river terraces, etc., while the lacustrine landforms include lake sedimentation and shoreline changes.
In addition, China's rivers, lakes and other water landforms also have unique characteristics. The Yangtze River, the Yellow River and other major rivers pass through the land of China, forming spectacular river valleys and river deltas. These river landforms not only reflect the erosion, transport and accumulation of rivers, but also record climate change and tectonic movements over geologic history.
(2) Quaternary tectonic movements and their characteristics
Quaternary tectonic movements in China ((1) the middle and late Upper Pleistocene to the early early Pleistocene, the neotectonic movements are manifested in: (1) the Qinghai-Tibet Plateau was uplifted violently, and the major mountain systems such as the Tianshan Mountains and the Qilian Mountains were also strongly uplifted, (2) some intermountain basins were formed, such as the Yuanmou Basin in Yunnan and the Xigeda Basin in Sichuan, (3) the southern part of the Loess Plateau was subsided, and (4) the Qinghai-Tibet Plateau, Northeast China, and North China had strong volcanic activity.
(2) Early Pleistocene and Late Pleistocene. The neotectonic movement is manifested in the following aspects: (1) the Qinghai-Tibet Plateau continues to uplift, the Upper Pleistocene-Lower Pleistocene facies strata in northern Tibet are tilted, and the gravel layers of the Yumen Formation around the plateau are dislocated, (2) some lakes disappear, such as Xigeda Lake, (3) the Loess Plateau rises in the north and declines in the south, (4) some strata are interrupted, such as in the Weinan area, and (5) there is a strong basalt flow overflow in North China. (3) Middle Pleistocene.
The neotectonic movement is manifested in the following aspects: (1) the Tibetan Plateau continues to rise, (2) the northern part of the Loess Plateau declines, and (3) there are strong volcanic activities in eastern and southwestern China, such as Wudalianchi, Datong, Leizhou Peninsula and Tengchong area. (4) Late Pleistocene-Early Holocene. The neotectonic movement is manifested in the following aspects: (1) the strong uplift of the Qinghai-Tibet Plateau, with an uplift range of about 800-1000m, (2) the overall uplift of the Loess Plateau, (3) the occurrence of large transgression in North China and northern Jiangsu, (4) the formation of the Songliao watershed in Northeast China, (5) strong volcanic activity, (6) the Yellow River and the Yangtze River eventually run through all the mountains and lakes in the Quaternary to form a large river), which are mainly manifested by the uplift, fault and fold of the earth's crust. These tectonic movements not only directly shape the landform, but also affect environmental factors such as climate and hydrology.
The upward and downward movement of the earth's crust is one of the main factors leading to landform change. In the Qinghai-Tibet Plateau and other regions, the strong uplift of the earth's crust has caused significant changes in the surface morphology, forming landforms such as mountains and valleys. In areas such as the North China Plain, the relative subsidence of the earth's crust flattened the surface and formed vast plains.
Fault structures play an important role in the Quaternary landforms of China. Fault zones are areas of stress concentration and release in the earth's crust, and they often control the development and distribution of landforms. Many large fault zones in China, such as the Tanlu Fault Zone and the Kunlun Fault Zone, have had a profound impact on the local landforms. These fault zones not only control the formation and distribution of mountains and basins, but also affect the development and evolution of water bodies such as rivers and lakes.
The fold movement is also an important manifestation of the Quaternary tectonic movement in China. The fold movement caused the earth's crust to bend and deform, forming landform types such as folded mountains and folded basins. These folded landforms not only have unique morphological characteristics, but also contain rich geological information, which provides an important basis for us to understand the history of the earth and predict geological disasters.
(3) The interrelationship between Quaternary landform and tectonics
There is a close correlation between Quaternary landforms and tectonics. Tectonic movement is the basis of the formation and evolution of landforms, and landform morphology reflects the characteristics and processes of tectonic movements.
On the one hand, tectonic movements provide the impetus for the formation of landforms. Tectonic movements such as crustal uplifting, fracture and folding have led to significant changes in the surface morphology, forming various landform types. These landform types not only have unique morphological characteristics, but also contain rich geological information, which provides an important basis for us to understand the history of the earth and predict geological disasters.
On the other hand, the geomorphology also records the history of tectonic movements. Through the observation and analysis of geomorphology, we can infer information such as the type, scale and time of tectonic movements. This information is important for understanding the evolution of the Earth's surface, predicting future geomorphological changes, and formulating regional development plans.
In addition, the Quaternary climate also had an impact on the interrelationship between geomorphology and tectonics. Climate change affects not only weathering, erosion and accumulation of the surface, but also the degree and mode of activity of tectonic movements. Therefore, when studying Quaternary landforms and tectonics, we need to fully consider the influence of climatic factors.
(4) The evolution of Quaternary landforms and tectonics
The evolution of Quaternary geomorphology and tectonics in China is a complex and changeable process, which is affected and restricted by a variety of factors. During the period of geological history, China has experienced many tectonic movements and climate changes, and these events have had a profound impact on the formation and evolution of landforms.
During the glacial period (traditionally, there were at least four glacial periods according to moraines: from early to late, the Xixia Bangma Ice Age, the Nie Niexiongla Ice Age, the Jilong Temple Ice Age and the Rongbu Temple Ice Age in the west, and the Poyang Ice Age, Dagu Ice Age, Lushan Ice Age and Taibai Ice Age in the east), the climate was cold and dry, and the glaciation was strong, which had a significant impact on the landform of the mountains and plateaus. Glacier erosion and accumulation have formed unique glacial landforms, such as cirques, horn peaks, and U-shaped valleys. At the same time, glacial meltwater also shapes water landscapes such as rivers and lakes.
During the interglacial period, the climate was warm and humid, and the development of water landforms such as rivers and lakes was more significant. River erosion and sedimentation have created landform types such as alluvial plains and river deltas. Lakes record changes in climate and environment through rising and falling water levels and changes in the shoreline.
In addition, tectonic movements have also affected the evolution of landforms to varying degrees. The upward and downward movement of the earth's crust changes the surface morphology and structure, which provides a basis for the development of landforms. Tectonic movements, such as faults and folds, provide important geological context for the evolution of landforms by changing the continuity and integrity of strata.
5. Human activities and the Quaternary environment
(1) The impact of human activities on the Quaternary environment
1. Land use and vegetation change
With the growth of population and the development of society, the demand for land of human beings is increasing. Large-scale agricultural reclamation, urban sprawl, and infrastructure development have led to land-use changes and a decline in vegetation cover. These activities not only destroy the original ecological environment, but also affect the distribution and circulation of natural elements such as soil, water and climate.
2. Development and utilization of water resources
Water is the source of life and an indispensable resource for human activities. In the Quaternary period, with the development and utilization of water resources by human beings, rivers, lakes and other water bodies were disturbed and damaged to varying degrees. Excessive groundwater extraction and the construction of reservoirs and dams have changed the natural flow and distribution of water bodies, affecting the stability and health of aquatic ecosystems.
3. Development and utilization of mineral resources
During the Quaternary period, humans began to exploit mineral resources on a large scale to meet society's demand for energy and raw materials. The exploitation and utilization of fossil fuels such as coal, oil, and natural gas produce a large amount of waste and pollutants, causing serious pollution and damage to the atmosphere, water and soil environment. At the same time, the exploitation of mineral resources has also led to the change of land surface morphology and the destruction of ecosystems.
4. Climate change and anthropogenic emissions
The impact of human activities on the climate is becoming increasingly significant. Large amounts of greenhouse gases have changed the composition and structure of the atmosphere, leading to global warming and frequent extreme weather events. These climate changes have not only affected the living environment and quality of life of human beings, but also had a profound impact on the Quaternary environment.
(2) The impact of environmental changes on human activities in the Quaternary period
1. The carrying capacity of the natural environment
The carrying capacity of the Quaternary environment is limited. Human activities must follow the laws of nature and respect the carrying capacity of the environment. Excessive exploitation and utilization of natural resources will lead to environmental degradation and resource depletion, which will ultimately restrict the development of human society.
2. Impact on agricultural production
Changes in the Quaternary environment had an important impact on agricultural production. Climate warming leads to longer crop growth cycles and more pests and diseases, soil erosion and soil degradation reduce land fertility and crop yields, and water scarcity and water pollution restrict agricultural development.
3. Impact on the human living environment
Changes in the Quaternary environment also had an impact on the human living environment. Extreme weather events such as heavy rains, floods, and droughts pose a threat to human habitation, while air pollution and acid rain endanger human health, and environmental changes may lead to human migration and urban planning adjustments.
4. Socio-economic impact
Changes in the Quaternary environment also had socio-economic implications. Resource scarcity and environmental problems restrict the sustainable development of the economy, disaster risks caused by climate change increase social costs, and environmental problems also arouse social concern and public participation, and promote the formulation and implementation of environmental protection policies.
(3) Human activities and the sustainable development of the Quaternary environment
In the face of the impact of human activities on the Quaternary environment and the constraints of the Quaternary environment on human activities, it is necessary to seek the path of sustainable development.
1. Rational use and protection of natural resources
Formulate scientific and rational resource utilization policies and management measures to ensure the sustainable use of resources and environmental protection. At the same time, strengthen the research and application of resource recycling and energy-saving and emission reduction technologies to reduce the negative impact of human activities on the environment.
2. Respond to climate change and extreme weather events
Accelerate the construction of climate change monitoring and early warning systems, and improve the ability and level of response to extreme climate events. At the same time, we will promote green and low-carbon development, reduce greenhouse gas emissions, and alleviate the trend of global warming.
3. Protect ecosystems and biodiversity
Protect the integrity and stability of ecosystems, promote the conservation and sustainable use of biodiversity, and maintain the balance and health of the earth's biosphere.
4. Raise public awareness and participation in environmental protection
To raise public awareness and concern about environmental issues, encourage the public to actively participate in environmental protection actions and volunteer service activities, and jointly promote the harmonious coexistence of human beings and the Quaternary environment.
VI. Concluding remarks
Quaternary geology in China is a complex and important field of study, involving multiple disciplines and aspects. Through the study of Quaternary strata, glacial age, paleoclimate, human activities, etc., we can gain an in-depth understanding of the evolution of the earth's history and the interrelationship between human beings and the natural environment. In the future, with the progress of science and technology and the changes of social needs, the Quaternary geological research in China will usher in a broader development prospect.