Shuanghe Karst Cave National Geopark takes Shuanghe Karst Cave Group in the hot spring area as the core, including many hot spring groups with abundant water and high quality, the well-preserved Guangshui National Primitive Ecological Forest Park, and the rich history, culture and simple folk customs in northern Guizhou. Suiyang, an ancient cultural city with a long history, has outstanding people and outstanding people. Since the new century, the rapid development of social economy has provided good conditions for the establishment of geological parks. The establishment of Shuanghedong National Geopark will surely bring great vitality to the social and economic development of this area.
1 exploration and identification of the longest cave system in China
Because of the rich nitrate soil in Shuanghe Cave, local residents entered the cave long ago to carry out nitrate activities and dug up a lot of gypsum in the gypsum cave. Until April 1988, Guizhou Academy of Sciences received a report from the local government that a large cave was found in Wenquan Town, Suiyang County, and immediately began to investigate and detect Shuanghe Cave.
1In August, 988, a "Sino-Japanese Cave Expedition Team" composed of Institute of Mountain Resources of Guizhou Academy of Sciences, Tokyo University of Japan and Waseda University investigated and explored the Shuanghe Cave System, and the cave length was measured to be 25000m·m m. ..
1In August, 1992, the cave investigation team organized by Guizhou Cave Society investigated and measured the cave system again, and the newly measured cave length was 10200m. Through the analysis of the geological landform in this area, it is preliminarily determined that the development of tunnels in Shuanghe cave system is connected by hydrological network and may belong to the same cave system. During the period of 1994 ~ 1996, the researchers of Guizhou Institute of Mountain Research systematically explored and studied the origin and evolution of Shuanghe cave system. During this period, the geography department of Guizhou Education College organized teachers and students to go to Shuanghe Cave for field teaching practice, and made a preliminary analysis of the shape and causes of Shuanghe Cave.
From 200/kloc-0 to 2005, the Guizhou Cave Society and the French Cave Union led by Bi Potanz formed a Sino-French joint cave expedition to carry out further exploration activities and connect all caves with the hydrological network, so that the total length of Shuanghe Cave System increased from 70.502km in 200/kloc-0 to 89km in 2005, and the total length of Shuanghe Cave has jumped to the highest in China. So far, cave exploration has been carried out. Up to 2005, it has been preliminarily proved that Shuanghe Cave System consists of 168 caves, which are mainly distributed in Shuanghe and Longtangzi areas east of Rang Shuicao Valley, with the distribution density of 1.5 /km2, making it a natural cave museum. In particular, the cave system is mainly developed in the paleostrata dominated by dolomite from Middle-Upper Cambrian to Lower Ordovician. It is a cave system with complicated structure of water tunnel and trunk tunnel, which is distributed in a tree-like network. It has been proved that 23 caves, 4 underground rivers and 1 18 branches with different sizes are interconnected. Underground river is a perennial river with an average annual flow of about 5m3/s. The tunnel can be divided into four layers. The upper and lower layers are connected by inclined tunnels, with a relative height difference of 240m, a tunnel width of 10 ~ 20 m, a maximum width of more than 40m, a tunnel height of more than 10m and a maximum height of more than 60 m. The tunnel is often divided by vertical shafts or steep cliffs, with a general depth of 15 ~ 30 m and a maximum shaft.
The development scale of ancient dolomite strata is so huge, and the secondary carbonate deposition forms are rich and colorful, so it is very rare to preserve the original cave system in cave ecology.
Shuanghe Cave in Suiyang, Guizhou Province is the longest cave after Asia (length 109hm, depth 355. 1m), and the ranking of long caves in the world has risen from the previous 20 to 17.
2. Development of Shuanghe Cave System
2. 1 regional geological and geomorphological background
The development and evolution of Shuanghe cave system is closely related to regional geological background, tectonic events in geological history and paleogeographic environment.
The tectonic system in Shuanghe area belongs to the west of the northeast tectonic deformation zone of Fenggang on the Yangtze platform, and its geological history has experienced many structural changes and changes in sedimentary environment. The tectonic movement is dominated by vertical oscillation and block movement, and the sedimentary environment is dominated by marine facies. There are two major fold orogenic movements, namely, the Xuefeng movement about 1.4-0.8 billion years ago and the Yanshan movement about 2,543.8+0.3 billion years ago. The Xuefeng movement formed the platform basement, which remained in a relatively stable shallow marine sedimentary area for a long time. Until the Silurian Guangxi movement (450 million years), several thousand meters of early Paleozoic carbonate rocks and clastic rocks were deposited together, which lasted for about 400 million years. The thick carbonate rocks dominated by dolomite from Middle-Upper Cambrian to Ordovician are the material basis for karst landforms and cave development.
Yanshan movement is another important folding orogeny in this area, which made the strata before Cretaceous generally rise to the land and separated from the marine sedimentary environment for hundreds of millions of years, accompanied by strong folds and faults. There are synclines of anticlinorium and Tu Ping of Huangyuhe River in Shuanghe area, and the anticlinorium of Huangyuhe River is generally NNE. The folded open strata are gently inclined, and the dip angle is less than 20. Due to the strong interference of Cathaysian system, the secondary folds are strongly distorted and chaotic. Tu Ping syncline generally extends along the northeast direction of 10, with dip angles ranging from 40 to 70, and its axis is nearly steep. Due to the strong influence of Neocathaysian structure, the distribution direction of faults is mostly northeast, and the direction of structural line and its derived secondary faults control the development of landform and karst. For example, the Gongping fault is a zigzag longitudinal fault. The length of the faults in the north-south direction and the north-east direction is nearly 30 kilometers, and the dip angle is 60. There are no large faults in Shuanghe area, but there are low-level faults with small fault distance and large fault dip angle. For example, the upper wall of Shuanghe Tian Jiagou small fault inclines 80 to the northwest, rising by about 0. 1m, which means that the thrust fault runs through the whole mountain. A fault with dip angle of 70 and southeast 140 can be seen next to Caozhiba Highway in Shuanghe, with a bandwidth of about 4m, which is a compressive fault.
Joints are important structural features that control the development and distribution of cave systems. The joint direction is mostly NE and NW, and the joint density is 1.2 ~ 8 joints /m, and the two groups of joints mostly cross in an "X" shape. These yoked joints control the extension direction of underground surface water system, the development of karst caves and the deposition of karst caves.
The above geological structure background has a profound influence on the change of geographical environment and the process of karst. From the end of Mesozoic to the Quaternary, the climate has gradually changed from warm and humid to warm and cool, especially since the Quaternary (2 million years), Himalayan tectonic movement has strongly affected this area, showing many intermittent uplifts. In the intense uplift stage, the external force is active, and the river erosion and karstification are intensified, forming a multi-layer and multi-stage karst mountain canyon landform and karst cave system. This area can clearly see the multi-level geomorphic planation plane, showing different geomorphic characteristics. For example, in the Daloushan period, the plateau plane remained at an altitude of 1300 ~ 1500m in the Jinzhong mountain area, and in the basin period, the planation plane was at an altitude of 900 ~ 1300m, with flush karst peaks and many horizontal karst caves, until the elevation dropped to 900 in the gorge period (Wujiang period). Neotectonic movement rises strongly, the cutting of hydrodynamic active surface intensifies to form deep valleys, and surface water flows deep to form complex hydrological network and underground river system. The complex multi-layer and multi-branch karst cave system in Shuanghe area is related to this special geological and geomorphological evolution background, and traces of geomorphological environment evolution can be seen everywhere.
2.2 Spatial distribution characteristics of cave system
The formation process of Shuanghe cave system is very complicated, with tree-like grid-like plane distribution and multi-layer vertical distribution pattern.
The development of cave system is related to the evolution of underground river system in the upper reaches of Chiwuxi River and the special geological and geomorphological background.
Before the Pleistocene, there were three major rivers in Shuanghe area, which flowed to the northeast and east longitude. Long-term erosion is represented by the planation plane with an altitude of about 1300 ~ 1500 m.
Then, after a long period of erosion and dissolution, the crust rose greatly, the downward erosion intensified, and many shafts and sinkholes were formed in karst development. Three ancient rivers dive underground to form three underground river systems: one is the gypsum cave underground river, which flows in the direction of Longtangzi-Linshan Cave-Gypsum Cave-Luojiao Cave and joins Chiwuchi near Guihua Village; The other is Mahuangdong underground river, which mainly flows into Chiwu River along the direction of Honghuazidong-Mahuangdong upper hole. The third is the ancient underground river in the upper layer of Xiao Pi Cave, and the gypsum crystal cave is the largest branch cave that flows into Chiwu River along the river corner-Egou direction. During this period, the topography increased the development of surface valleys, with an altitude of about 800 ~ 1000 meters.
In the late Late Pleistocene, about 200,000 years ago, the crust continued to rise and the surface and underground rivers continued to cut down. The upper caves of Linshan Cave, Gypsum Cave, Foothold Cave, Xiao Pi Cave, Hongqizi Cave and Mahuang Cave all rose to dry caves, which is an important period of cave chemical deposition. The underground river flows out of Yinhe Cave and finally flows into Chiwu Creek. Gypsum Cave in the uplift of the earth's crust The ancient underground river has formed three independent caves, namely, Foothold Cave, Gypsum Cave and Forest Cave, with an altitude of about 650 ~ 780 meters. ..
With the evolution of regional geological and geomorphological environment, the surface underground river system has been diverted many times, gradually forming a complex hydrological network, and three independent underground rivers are connected with each other to form a network underground river system. Through field investigation and connectivity test, it is confirmed that there is an underground river system named Longtangzi, whose main stream flows out of the surface and flows into Chiwu River near Longtangzi Water Cave-Foothold Cave-Shuanghe Water Cave-Linshan Cave, and the top of some underground rivers collapses, which is very spectacular. The other is the Yinhe Cave, and the lower cave of Xiao Pi Cave-Shanwang Cave flows into Chiwuxi in Guihua Village, and the lower cave of the big wind tunnel is its main branch.
(Attached: distribution map of proven caves in Shuanghe Cave System)
2.3 Main strata and dissolution mechanism of cave system development
2.3. 1 widely distributed early Paleozoic dolomite-dominated strata.
The main material basis for the development of Shuanghe cave system is the strata of Loushanguan Formation of Middle-Upper Cambrian and Tongzi Formation of Lower Ordovician in Early Paleozoic, and the lithology is dolomite and dolomitic limestone during platform evaporation. The development of caves is closely related to the structure and composition of strata. The stratum of Daloushan Formation is the most developed, because it generally contains gypsum and salt, its texture is old and brittle, its occurrence is gentle (dip angle is 6 ~ 65438+02), and the rate of karst caves in joints and fractures is high.
Loushanguan Group of Middle and Upper Cambrian (∈2-3 1s)
The stratum is 725 ~ 790 meters thick and can be divided into three sections according to lithology:
In the third section, the light gray thick layer and medium thick layer are mainly fine-grained dolomite mixed with flint nodules, locally mixed with dolomite limestone, and the bottom is clastic dolomite, syngenetic breccia dolomite or oolitic and oolitic dolomite;
In the second section, the light gray thick-layer and medium-thick-layer fine-grained dolomite is mainly siliceous dolomite, the lower part is mainly thin-layer fine-grained dolomite, and the bottom is 1 ~ 5m chronosandstone, calcareous chronosandstone, dolomite chronosandstone and thin-layer fine-grained dolomite;
The first gray medium-thick layer is sandwiched with thin-layer micro-dolomite, the lower part is mainly thin-layer fine-grained dolomite, and the bottom is 1 ~ 5m timely sandstone, calcareous timely sandstone, dolomite timely sandstone and thin-layer fine-grained dolomite.
Lower Ordovician Tongzi Formation (O 1t)
The contact between platform facies deposits and underlying CAMBRIAN system is mainly dark gray and gray-black dolomite limestone with dark gray limestone and bioclastic limestone, and the formation thickness is 18 1 ~ 225m.
2.3.2 High-strength dissolution process
According to analysis; Chemical composition of micrite dolomite in Loushanguan Group;
Calcium oxide 29.6 1%, magnesium oxide 1.96%, silica 29.34%, silica 2 1.87%, calcium oxide/magnesium oxide 1.53.
Chemical constituents of dolomite in Tongzi Formation;
CaO37.92、MgO 12.80、SiO27.5 1、CaO/MgO2.96。
Through the study of carbonate dissolution strength, it is pointed out that the correlation coefficient between the percentage content of dolomite in carbonate and the specific dissolution degree is R = 0. 173, and the general change trend is that the specific dissolution degree decreases with the increase of magnesium content in rocks. When the calcium-magnesium ratio is greater than 4, the specific corrosion degree is higher, and when the calcium-magnesium ratio is less than 4, the average specific corrosion degree is between 0.05 and 0.63, and the specific corrosion degree of pure dolomite is 0.50. The dolomite-dominated strata in Shuanghe area show a high-intensity action process, which is mainly related to its special geological environment. In Shuanghe area, apart from the development of stratigraphic structural fractures, the increase of neotectonic movement intensity and the rapid alternating circulation of surface water and groundwater, it is more important that dolomite contains gypsum layer and aqueous solution containing SO42-, and magnesium carbonate has a high solubility in groundwater containing SO42-. Due to dissolution, ca2+ in water almost completely precipitates. In Shuanghe area, more groundwater rich in so42- moves upward under pressure, and the content of so42- in groundwater will increase rapidly after interaction with CaSO42H2O in rock mass. In the process of replacing limestone with CaSO _ 4·2H2O, the cavity will remain unchanged and expand due to expansion and gravity collapse.
The dissolution process of calcium carbonate is as follows:
Calcium carbonate+carbon dioxide +H2O = calcium (HCO-3)2
CaCO3+h2so 2+2H2O = caso 4·2H2O+H-+HCO-3
2.4 rich gypsum and carbonate sedimentary forms
Gypsum Crystal Cave is a cave in Shuanghe Cave System, which contains nearly 30,000 ㎡ gypsum crystal flowers with different shapes and dazzling colors, such as dovetail gypsum, gypsum stone pillars and gypsum curtain. Shell-shaped gypsum and fibrous, needle-shaped and flocculent gypsum crystal clusters enter the gypsum crystal cave, just like a magical crystal palace. Such a well-developed and well-preserved gypsum crystal cave is very rare at home and abroad. Not only the deposition process of gypsum can be seen in the cave, but also the pore-forming effect under gypsum infiltration can be seen. Gypsum oozing from rock stratum or joint surface produces great expansion force during crystallization, which leads to the crushing, extrusion and caving of rock stratum and promotes the development of cavities.
Many caves in Shuanghe cave system have special hydrochemical environment, and the sedimentary forms of carbonate are rich and colorful. The most distinctive is Shanwang Cave, which is called Crystal Palace. All kinds of white and transparent stalactites, stalagmites, stone pillars, all kinds of small spherical stone flowers and perfect basin sedimentary forms are concentrated in 400-meter-long caves. The most unusual thing is that the curled stones in the cave are densely covered with the top wall of the cave and the stalactite surface. Curly stones can only be formed in an environment where calcite crystals are not disturbed by airflow, the pressure field changes little, the relative humidity is above 95%, and evaporation is weak. The distribution of spherical carbonate sediments is very common, including: stone flower, stone coral and stone grape. Stone mushrooms and cave beads, etc. Its formation process is due to the free diffusion of capillary water or condensed water oozing from the surface of calcium carbonate deposits through capillary action.
Pool deposition is another feature of carbonate deposition. For example, calcite crystal clusters and lotus leaves floating on the water surface in Ruwangdong and Luojiaodong basins run on the gas-liquid interface near the water surface due to CO2 escape and calcium carbonate deposition, and there are countless cave beads and stone balls of different sizes in the basins. The most spectacular "horizontal terrace" in the gypsum cave, which is more than 400 meters long and surrounded by stone dams, is called "Qianqiu Bang".
Large-scale stalactites, stalagmites and stone pillars are distributed in the big wind tunnel, footfall cave and Linshan cave. Some stone pillars are called Optimus Prime with a height of 10 ~ 20m and a diameter of 80 ~ 100 cm, which are of great ornamental value.
From: http://www.globalgeopark.org/publish/portal0/tab514/info1772.htm.