Fuzhou landform formation

The geomorphic classification system of Fujian Province is based on "China 1 ∶ 1 10,000 Geomorphic Mapping Specification", combined with the actual situation of the province, and divided according to the distribution law and subordinate relationship by using the method of analysis and combination. * * * is divided into three levels: the first level is mainly based on the development of modern landforms, which are divided into five types: flowing water landform, marine landform, karst landform, aeolian landform and volcanic lava landform. The second level is divided into Zhongshan, low mountain, hill, platform and plain according to the basic morphological characteristics and height (including altitude and relative height). In the third stage, according to the regional characteristics and the requirements of production practice, the flowing water landform is divided into 9 types, the marine landform into 6 types, the karst landform into 4 types, the aeolian landform into 3 types, and the volcanic lava landform into 2 types, totaling 24 landform types.

I. Flowing water landform

Flowing water landform is a landform formed by erosion, transportation and accumulation of surface flowing water, which can be divided into the following types in Fujian:

(1) plain

Refers to the area where the ground is relatively flat, with gentle fluctuation, the average slope is less than 6 degrees, and the relative height is generally not more than 10 meter. According to the different forms and causes, it can be divided into the following categories:

1. alluvial plain

The plains formed by the bending action of rivers and the flood and alluvial action of rivers include flood plains and first-class terraces. Fujian alluvial plains are mainly distributed at the confluence of river tributaries in the lower reaches of major rivers along the eastern coast and inland intermountain basins in the west, such as Fuzhou Plain in the lower reaches of Minjiang River, Quanzhou Plain in the lower reaches of Jinjiang River, Zhangzhou Plain in the lower reaches of Jiulong River and Xinghua Plain in the lower reaches of Mulan River, as well as Wuyishan, Jianyang, Jianou, Shaowu, Jianning, Ninghua, Shaxian, Yong 'an, Liancheng, Shanghang, Longyan, Pinghe and Zhangpu, where the water level is generally higher than that of local rivers. The terrain is low and flat, the soil layer is deep, and the composition materials are mainly fine sand and clay alluvial by rivers in the late Pleistocene and Holocene. The floodplain is mostly developed in the convex bank on both sides of the river bed and the bend section, which is arc-shaped or crescent-shaped, and the surface layer is mainly sand and clay. The initial floodplain was mainly river gravel. The first-class accumulation terrace is 3 ~ 8m higher than the river water level, with layered structure and obvious dual structure, with gravel layer at the lower part and silty clay at the upper part. The groundwater is rich, wide and flat, slightly inclined to the riverbed and downstream, and mostly extends to the foothills on both sides of the valley. The arable layer is between 15 ~ 25 cm, and the soil quality changes from the riverbed outward in turn as sand mixed with mud, mud mixed with sand and mud field. The alluvial plain has a high land utilization rate, which is not only cultivated into paddy fields, but also the producing area of economic crops such as vegetables, fruits and sugarcane.

2. The flood plain

It is deposited by perennial running water and seasonal running water and distributed in front of the foothills. In Fujian, the edges of some large mountain basins are often relatively developed, and the width is not large, generally only 3 ~ 5 kilometers. The composition material is sand and gravel layer, and the lens containing sand and clay has poor sorting and gravel roundness. The surface materials are mainly clayey silt and loam. The ground slope gradually slows down from 1/300 ~ 1/500 to1000, which has obvious slope break at the junction with other types of plains. The diluvial-alluvial plain can be further divided into small alluvial fans, terraces, plains and valleys. Such as the southern foothills of Beiling in Fuzhou Basin, the foothills of tianmashan in the west of Zhangzhou Plain and the foothills of Xianyou Plain in the northwest, all belong to the diluvial-alluvial plain.

3. Valley Plain

It is mainly developed in the valley between mountains and hills, and is mostly a plain formed by river scouring and silting on the basis of structural faults or intermountain fault basins. Distributed in Minjiang River, Jiulong River, Tingjiang River, Jinjiang River and Mulan River basins. Valley plains are generally composed of flood plains and terraces, which are distributed in a strip or beaded shape, with a relative height of about 10 m and a gentle slope with a slope of less than 5. The dual structure is obvious, the soil is fertile, the water is sufficient, and the light and heat conditions are good, so it is an excellent land for agriculture in mountainous areas. Because of the different valley directions, the light and heat conditions in the valley plain are often different. Generally, the daily light time in the north-south valley plain is shorter than that in the east-west valley plain 1 hour, and the average temperature is correspondingly lower. At the same time, the North-South Valley is often a channel for cold air to go south in winter, with strong wind and low temperature. Therefore, the east-west valley plain is superior to the north-south valley plain in production and utilization.

4. Basins and valley plains

Scattered in the mountainous and hilly areas of the province. Individual areas are not large, the bottom is slightly undulating, and the four sides are slightly inclined to the middle. The basin-valley plain is formed by long-term flowing water erosion and accumulation under the control of regional structure. Due to the different internal and external forces, the shapes of plains are different, some are round and semi-circular, some are rectangular, long and diamond. The sediments are mainly alluvial, diluvial and slope sediments. The basin-valley plain has deep soil layer and fertile soil, which is convenient for irrigation. This is the location of mountainous residential areas, and it is also the main grain and cash crop area.

(2) Taiwan Province

It is a transitional landform type between hills and plains, and it is mostly developed in areas where the crustal movement is relatively stable or slowly rising. The platform is relatively complete, the slope is gentle or undulating, and the dip angle is generally less than 5. The slope of the sill is steep, mostly around 15, and the relative height is 15 ~ 50m. The modern geomorphic process is mainly sheet erosion.

The platforms in Fujian Province are mainly distributed in the southeast coastal areas, starting from Fuqing in the north and reaching Zhao 'an in the south, with a narrow strip-like distribution from northeast to southwest, accounting for about 3.5% of the total area of the province, while Longgao Peninsula in Fuqing City, Hushi Peninsula in Putian City, Xianyou Basin, Hui 'an Peninsula, Jinjiang Peninsula in Xiamen City, Jinmen Island, Zhangzhou Basin, Zhangjiang River, the middle reaches of Dongjiang River and Dongshan Island are relatively concentrated. The platform is mainly composed of Yanshanian granite, with volcanic rocks, sandstone shale, metamorphic rocks and Quaternary alluvial and diluvial rocks in some areas. The platform made of granite has deep weathered layer, stable foundation and high bearing capacity, which is suitable for infrastructure construction. The soil is mainly brick red and red soil, which is acidic. Due to long-term erosion and unreasonable utilization, the fertility is low. Areas with poor vegetation coverage are easy to be washed away by running water, resulting in serious soil erosion. On the platform of Jinjiang Peninsula, shallow depressions are developed due to cutting. There are residual hills in Longgao Peninsula and Hushi Peninsula.

(3) Qiu Ling

It is developed in the area where neotectonic movement is relatively stable or slowly rising, mainly distributed on the mountainside, both sides of the valley, inside the basin and along the eastern coast. Under the long-term erosion and cutting of running water, the shape is broken, and there are no certain veins or veins that are not obvious, and there are often micro-landforms such as dry valleys, gullies and gullies. The slope is generally15 ~ 25, and the altitude is below 500 meters, accounting for about 26% of the total area of the province. According to the size of the terrain, it can be divided into low hills and high hills. The height of the former is less than 250 meters, and the height of the latter is 250 ~ 500 meters. They are all composed of granite, volcanic rocks, red rocks, sand shale and metamorphic rocks.

1. Low hills

It is mainly distributed around the valley plain, the outer edge of high hills and the eastern coastal areas, with an altitude below 250m, a relative height below150m and a slope of15 ~ 20. The hills are isolated and scattered, often circular, with some ridges and hills, gentle ups and downs, broken and scattered, hills and valleys crisscross, and gullies and depressions between hills are relatively developed. The modern geomorphic process is dominated by flowing water erosion and erosion, with strong sheet erosion and local gully development. Granite low mountains are mainly developed around the continental basin-valley plain and on both sides of the valley plain, such as Pucheng, Guangze, Hotan and other granite areas. In addition to being distributed around larger plains such as Fuzhou, Puxian, Quanzhou and Zhangzhou, some islands and peninsulas also have granite hills, such as Longgao Peninsula, Hushi Peninsula, Hui 'an Peninsula, Jinjiang Peninsula and Haitan Island, Xiamen Island, Dongshan Island and Rinan Island. The tops of granite hills are mostly round with gentle undulations. The hillside is mostly below 20, with strong weathering, sandy and acidic surface, and poor water and fertilizer conservation. The granite hills distributed in coastal areas are characterized by strong external force, poor vegetation coverage, obvious cracking and bare bedrock. As a result of spherical weathering, they often develop into stone egg landforms, such as Wanshiyan on Haitan Island and Sunlight Rock on Gulangyu Island, which have been turned into tourist attractions. Volcanic low hills are mainly composed of Changlin Formation, Nanyuan Formation and Shimaoshan Group, which are mainly distributed in the mountainous basin-valley plains and coastal areas on the east side of Fujian-Zhongshan System, such as the basin-valley plains in Bandong, Minqing, the banks of Shacheng Bay and the Cisse area. Scattered distribution, gentle shape, shallow cutting, mostly arranged in ridges, the slopes are all below 20, the weathering crust is 2 ~ 5 meters, the surface layer develops into red soil, the texture is slightly sticky, slightly acidic, and the organic matter content is medium, which is mostly used as economic forests and tea gardens. Hongyan low hills are distributed in the large and small Hongyan basins west of Jiufeng Mountain-Daiyun Mountain-Bopingling Mountain range in central Fujian, mainly including Shenxianyan in Pingding Township of Pucheng, Wuyishan in Wuyishan City, Komatsu in Jian 'ou, Levin in Shunchang, Jinhu in Taining, Chengguan in Shaxian County, Yong 'an and Liancheng in Ninghua, Hekou, Anyuan and Shuiqian, the ancient city of Changting, Xiyuan Township in Zhangping, Baisha and Shanghang in Longyan. It is mainly composed of Shaxian Formation of Cretaceous with soft lithology. Under the long-term external force, most of them are flat-topped gentle slopes with thick weathered layers. A few are monoclinic low hills with a relative height of 50 ~ 100 m. Valley between hills is developed, and the valley is wide and flat, mostly paddy fields. Red rock hilly soil is purple soil, rich in potassium, which can develop economic forests and fruit trees, such as tea, camellia oleifera and citrus. Sandstone and shale are low mountains and hills, with a small distribution area, mainly distributed around Zhangping, Longyan, Yongdingkan, Jiangle and other basins and valley plains. It is composed of strata such as Wenbishan Formation, Xikou Formation, Lishan Formation and Zhangping Formation, most of which are arranged in a ridge shape. Weathered crust is 3-5 meters, and the surface layer is mostly sandy red soil, with loose structure and acidity. The hills are mostly terraced fields, which are suitable for dry farming. Metamorphic rocks are low mountains and hills, distributed on both sides of Jianxi and Futunxi valley plains and around some mountain valley plains. Most of them are composed of metamorphic rock series. Hills are often ridged, and the weathering crust is 3-8 meters thick. They developed into red soil, with yellow soil on the surface, sticky texture, organic matter content of 3%-3.5%, good natural fertility, which can be converted into agricultural land and suitable for dry farming.

2. High mountains

Widely distributed, the area is larger than the low hills, accounting for about 20% of the total area of the province. The inland areas are mainly distributed on both sides of the valley of Jianxi, Futunxi, Shaxi, Tingjiang and its larger tributaries and around the valley plain between mountains. Fuding in the north and Zhaoan in the south are distributed along the coast, especially in the middle and lower reaches of major rivers such as Shacheng Port, Sandu 'ao, Saijiang, Huotongxi, Aojiang, Minjiang, Mulan River, Jinjiang, Jiulong River, Zhangjiang River and Dongxi River. The absolute heights of hills and hills are all below 500m, and the relative heights are 100 ~ 200m, but there are differences in different places. Generally, the farther away from the sea, the smaller the relative height, while the relative height in coastal areas is relatively high, with a slope of 20 ~ 25, and some hills are above 30. Most of them are short strips, often connected with mountains or extended by mountain branches, and some are round.

Granite hills are widely distributed in Fujian province, and coastal counties (cities) such as Xiapu, Luoyuan, Lianjiang, Changle, Hui 'an, Xiamen, Changtai, Longhai, Zhangpu and Zhao 'an have large areas. Inland areas are concentrated in counties such as Guangze, Yongding, Shanghang and Wuping. Mainly composed of Yanshanian granite, the dome is round and the weathering crust is deep, ranging from several meters to dozens of meters. The soil is mostly red soil, latosol and sandy, and Pinus massoniana grows well. The granite hills in coastal areas are mostly isolated hills. Under the action of hot and humid air and strong wind, there is strong physical weathering besides chemical weathering. In some areas where vegetation is destroyed, bedrock is exposed and soil erosion is serious, many huge granite stone eggs are formed on hilltops and hillsides, which have become special landscapes of granite stone eggs, such as Longgang Peninsula, Hui 'an, Xiamen, Changtai, Longhai and Fuqing Dongshan. Volcanic rocks are high-hilly, mainly distributed in the coastal areas east of the mountain system in central Fujian, among which Fuding, Xiapu Yantian, the lower reaches of Saijiang River, Jianjiang Peninsula, the middle and upper reaches of Aojiang River, Zhanghuban to the banks of Baisha Valley in Minjiang River, the middle and lower reaches of Dazhangxi River, Putian, Baisha, Yongchun, Anxi, Nan 'an and Xiao Yun are concentrated, and are composed of Changlin Formation, Nanyuan Formation and Shimaoshan Group. Most of them are above 150m, and the slope is often around 25. The slope is gentle, and the weathered layer is 3 ~ 5m. Red soil and lateritic red soil are developed, with good vegetation coverage. Timber forests and firewood forests are more developed, and economic forests and fruits can be developed in the foothills. The distribution of red rock high hills and red rock low hills is basically the same, but most of them are developed in the axial area of red rock basin. It is composed of thick red glutenite, conglomerate and some mudstone strata from Late Cretaceous to Early Tertiary, with different occurrences, dip angle of 10 ~ 30, vertical joints developed and composed of calcium, mud, iron and silica gel. Under the influence of neotectonic movement, the typical "Danxia landforms" such as Tianyou Peak, Tiepan Peak, Lion Rock, Matouyan in Wuyishan, Eighteen Scenes in Yong 'an Taoyuan Cave, Baizhangyan, Lianhua Village, fairy sticks, Maoeryan and Ganlu on both sides of Taihu Lake in Taining are famous scenic spots in the province and the whole country, and have now been developed into tourist attractions. In red rock hills, due to the development of vertical joints in rock strata, some alleys and valleys with steep slopes and narrow bottoms are often formed, with steep cliffs on both sides and narrow and flat bottoms, which are generally several meters to tens of meters wide. Gravel stratum with a thickness of about 2-4m is accumulated at the bottom, silty loam is developed, and the water and humidity conditions are good. Tea trees and dry farming are planted in the ditches in the Hongyan high hill in Wuyishan. Sand shale hills are mostly distributed on the edge of low mountains and both sides of river valleys, and are mainly composed of Mesozoic and Late Paleozoic glutenite and sand shale, which are often distributed in groups. Although the peak line is discontinuous, there are still some veins to be found, such as the high hills on both sides of Jianxi Valley between Lukou and Changkeng, and the high hills in Jiangle, Zhangping and Nanjing counties, which are composed of Zhangping Formation, Lishan Formation and Wenbishan Formation. Generally, the high hills composed of sand shale are strongly weathered, and the weathering crust can reach 4 ~ 8m. The soil layer is thick, mostly red soil, and the vegetation coverage is good, which is suitable for forest growth. Metamorphic high hills are mostly distributed between Wuyishan and Jiufeng Mountain, and are the front or extension of the mountains composed of ancient metamorphic rock series in the early Paleozoic and before, especially in Jianyang, Jian 'ou, Shaowu, Shunchang, Nanping, Jiangle and other counties (cities), and there are also small areas along the coast. The top of the high mound of metamorphic rocks fluctuates gently and has strong cutting. The hills are mostly banded and round, with developed weathering crust, thick slope and residual products. The developed red soil is loose in texture, good in permeability, slightly acidic and high in organic matter content, about 4%, which is suitable for the growth of pine, fir, bamboo and broad-leaved forest. Most of the fast-growing and high-yield forests in this province grow in the hilly areas of metamorphic rocks.

(4) Mountains

It is a combination of mountains and valleys. Usually located in areas where tectonic movement and denudation are active. High terrain, deep cutting depth and complex geological structure. Above 500 meters above sea level, the slope is usually greater than 25. The mountainous area of this province is large, mainly distributed in Wuyishan, Jiu Feng, Dai Yun, Bopingling, Taimu, Guishan and other places, accounting for about 53% of the total area of the province. Most of them are composed of volcanic rocks, granite, sand shale and metamorphic rocks, and some are red rocks. According to different heights, mountains are divided into low mountains and Zhongshan mountains.

1. Low mountain

The altitude is less than 1000 meters, and the relative height difference is over 200 meters. It has a vein-like trend and relatively continuous terrain. The low mountains in this province are widely distributed, mostly at the outer edge of Zhongshan or between Zhongshan and hills, accounting for about 32.5% of the total area of the province. The modern geomorphological process in low mountain areas is dominated by streamline erosion, with strong weathering and deep weathering crust. The soil is mainly red soil, and yellow red soil is also distributed at the top. Annual accumulated temperature is high and rainfall is abundant. It is an area where single and double cropping rice is planted alternately, and trees such as pine, fir and bamboo grow well.

The low mountains composed of volcanic rocks are mainly distributed on both sides of Taimu Mountain, Jiufeng Mountain and Daiyun Mountain, as well as on the outer edge of the northern section of Wuyi Mountain. They are mainly composed of Mesozoic Changlin Formation, Nanyuan Formation, Shimaoshan Group and ShishNiu Shan Formation. The lithology is relatively hard, the cutting is moderate, and steep rock walls and peaks are often formed, with a slope of about 30 and a relative height difference of 300-400 meters. There are basin and valley plains. Most of the mountains strike northeast or northwest, which is generally consistent with the tectonic line. Volcanic rocks, with good vegetation coverage and dense forests, are the main forest areas in this province. Granite low hills are widely distributed in granite bodies of different periods in this province, among which the low hills are mainly composed of Yanshanian granite, with round top, thick weathered crust, few outcrops of bedrock, slope often ranging from 20 to 30, well-developed drainage system, deep cutting and V-shaped valleys. There are basin and valley plains in mountainous areas, and there are first-class landforms at an altitude of 500 ~ 650 meters. The soil layer is deep and sandy, mostly red soil or yellow red soil, with local yellow soil development, dense vegetation and good hydrothermal conditions. It is also the main forest area in this province. The low mountains composed of metamorphic rocks are mainly distributed between Wuyishan, Jiu Feng and Daiyun Mountain, and are mostly composed of ancient metamorphic rock series before Late Paleozoic, which is the main type of low mountain landforms in northern Fujian and western Fujian. Under the long-term action of internal and external forces, the mountain is steep, the top is gently undulating, the weathering is strong, the weathering crust is thick, the cutting depth varies from 200 to 600 meters, the slope is often around 30, and the valley is mostly V-shaped. Deep soil layer, good natural fertility, high organic matter content and moderate hydrothermal conditions are suitable for the growth of Chinese fir, bamboo and evergreen broad-leaved forest. This is the "golden zone" of forestry development and is known as the "green treasure house". Hongyan low mountain is not widely distributed in this province. Red basins distributed in Wuyishan, such as Sanyangfeng (7 17.7m), Fengfeng (530m) and counties (cities) such as Taining, Ninghua, Shaxian, Liancheng, Wuping and Zhangping, are all composed of red rocks with dense lithology and vertical joints, and monoclinic areas are mostly unilateral. The top of the mountain is gentle, the hillside is steep and the cutting is intense. Most of the valleys are U-shaped or alley valleys, which often form a typical Danxia landform with flat top, steep body and slow feet. Sandstone and shale are low mountains, mainly distributed in western Fujian and southwestern Fujian, with only a small amount in other areas. The mountain trend is mostly northeast, which is generally consistent with the direction of the tectonic line. The ridge line is obvious, and it is mostly composed of sandstone, gravel and shale. Often controlled by structure, the trace is clear. Some mountains are one-sided, some are folded and folded, and the mountains are magnificent. The valley is deep and there are many canyons, which belong to the middle cut low mountain.

2. Zhongshan

It was formed under the long-term erosion of external forces such as tectonic movement and flowing water cutting. The altitude is between1000 ~ 2000m, and the mountain strike is consistent with the main tectonic lines, and the structural features are obviously reflected in the landform. Ridges are generally pointed or round, with overlapping peaks, continuous veins and magnificent momentum. The main peak 1500m or more, and the slope is above 30. Zhongshan area is mostly the upstream and source of rivers. The water system is dendritic, right-angled, annular and radial, with strong undercutting of the river bed, V-shaped valley and frequent canyons and gullies. Zhongshan is widely distributed in this province, accounting for about 20.5% of the total area of the province. The vertical natural zoning is obvious, and the temperature decreases continuously from the foot of the mountain. On the whole, the altitude rises by 100 m, and the annual average temperature drops by 0.5℃ ~ 0.6℃. Rainfall increases with the elevation. Four rainy areas in the province (northwest of Wuyishan, near Zhouning, west of Dehua and west of Nanjing) are all in the Zhongshan belt. Due to the difference of vertical hydrothermal conditions in Zhongshan, the vertical zonation of soil and vegetation is also obvious.

Zhongshan, which is composed of volcanic rocks, is the most widely distributed in the Fujian-Zhongshan system, and Wuyishan vein is also distributed. It is the main landform type that constitutes Jiufeng Mountain, Daiyun Mountain, Bopingling Mountain, Taimu Mountain and Niu Shan. It consists of Nanyuan Formation, Shimaoshan Group and Niu Shan Formation. Its lithology is hard, its structure is compact, and its joints are developed. Under the influence of neotectonic movement and uplift, the river cuts strongly, and the cutting depth often reaches 500-800 meters. The strike of mountains is consistent with the structural direction, mainly northeast-southwest, followed by northwest-southeast, forming a landscape criss-crossing, alternating mountains and valleys, and overlapping mountains. Most of the peaks above 1800 meters in the province belong to volcanic mountains, such as Huanggang Mountain (2 158 meters above sea level), and Daiyun Mountain (65438 meters above sea level). Multi-level landforms in mountainous areas, with altitudes of 1600 ~ 1800 m, 1200 ~ 1400 m,1000 ~100 m respectively. Granite mountainous areas are mainly distributed in the west of the mountain belt in central Fujian and around Kameyama Mountain, such as Shita Mountain, Shangpingshan Mountain, Kuzhulinjian (elevation1666m), Huanglianyu (elevation1807m) and Shimen Mountain (elevation 18 165438). Granite mountain is tall and majestic, with tall and straight peaks, hard lithology, developed vertical joints, steep slopes and deep valleys. There are exposed bedrock on the top of the mountain, mostly round, which often develops into a "tile" or "stone egg" landscape. Metamorphic rocks are mainly distributed in the area between Wuyishan Vein and Fujian-Zhongshan Belt, and are mostly composed of metamorphic rock series before the Early Paleozoic. The former is a tall mountain because of its hard lithology, strong anti-corrosion ability and the uplift of neotectonic movement. The mountain is steep, with rapids, canyons and valleys. Because of the good soil and water conditions, it is beneficial to the growth of plants that like humidity and acid, and suitable for the growth of Chinese fir, pine and other trees. Zhongshan, which is composed of pre-Sinian and Sinian metamorphic rock series, has been weathered for a long time, the top of the mountain is gentle, the slope is relatively small, the soil layer is deep, the cutting is intense, there is a small basin plain, only rice can be planted in one season, the top of the mountain is windy, the temperature is low, and the hillside is suitable for forest growth. It is also the main forest area in this province. Zhongshan is mainly composed of sand shale, mainly distributed in southwest Fujian, with a small area, which is composed of sandstone and glutenite in late Paleozoic and Mesozoic. Ridges are mostly distributed in the northeast-southwest direction, which is consistent with the direction of tectonic lines. The slope is steep, mostly above 35 degrees, gentle in the forward direction, steep in the reverse direction and deep in the valley, mostly in a "V"-shaped canyon. Although the mountains are not high, the peaks are towering. The vegetation cover is good, and the soil is mainly red and yellow soil, with sticky texture and good fertility, which is suitable for the growth of pine, fir and broad-leaved forest.