How did the geological structure of Feilaifeng come into being?

"nappe structure" casts Feilai peak

In the late 1920s, Chinese geologists first discovered "Feilaifeng" in Pengzhou, and after being confirmed by many Chinese and foreign geologists, they recorded "Feilaifeng" in geological textbooks. Longmen Mountain is about 500 kilometers long and 30-70 kilometers wide. Such a long area is located at the junction of the edge of the eastern Yangtze paraplatform and the Tethys Sea, forming a large-scale tectonic belt napped from northwest to southeast.

Some experts believe that the Longmenshan nappe structural belt was formed after many geological structures, and it is a unique type of geological structural belt in the world after the typical geological structures of the European Alps and the Cordillera Mountains in North America. Feilaifeng is a geomorphic feature formed by nappe structure. Under the tectonic movement of the earth's internal force, the surrounding mountains pushed in a certain direction from bottom to top, and finally the nappe structure was denuded in the later stage, and its remaining old strata (Permian or Carboniferous, etc. ) covers a new stratum, so it is called "Feilaifeng". It has a completely different genetic mechanism from the "glacier boulder" formed by the external force of the large ice sheet through the handling process. Although both may be "Lao Zi" over "Son", there will be no fault between the old and new classes in the latter.

The second view

"Glacier boulders" form Feilai Peak

Another part of experts believe that the fact that Feilai Peak is constantly found in Quaternary ice water accumulation strata in Pengzhou and Shifang areas is explained by the internal force of crustal movement. There are too many problems, and Feilai Peak can only be explained more reasonably by "glacier boulder". For example, no overthrust fault remains can be found at the contact between Feilai Peak and the underlying stratum. Because of the low temperature and slow speed, ice water is involved, and the bottom of Feilai Peak is in "cold contact" with the Quaternary ice water accumulation layer, so there are no thermodynamically metamorphic minerals, fault breccia and missonite. Judging from the occurrence of Feilai peak, whether it is a group flight or a single Feilai peak, it is high in the northwest and low in the southeast, and the contact surface between Feilai peak and the underlying stratum is inclined to the southeast, which is contrary to and contradictory to the rock mass layout formed by the structural nappe from west to east and the inclined occurrence of a single rock mass. Without the "protection" of ice solidification, the limestone body of Feilaifeng can't stand the collision of running water or gravity collapse.

Expert knowledge

Feilaifeng is a rare geological wonder in the world.

In addition to the above two mainstream views, some experts put forward the view of "the origin of Feilai Peak in Longmen Mountain", and there are different opinions. Some of them are the result of Baishuihe fault overthrust, some of them are the result of Wenchuan fault nappe, and some of them are considered to be the result of partial tearing of Paleozoic rock blocks connected with Tangwangzhai and Baoxing complex nappe, forming large and small flying peaks, and the superposition of nappe and detachment.

However, no matter how heated the discussion and debate, experts have formed a * * * knowledge, that is, Feilai Peak in Longmen Mountain, whether formed by nappe structure, glacier boulders or other reasons, is a rare geological wonder in the world and has great protection and development value. Wang Lansheng, a doctoral supervisor at the School of Environmental Engineering, Chengdu University of Technology, said: "Academic arguments have always been widespread, which has caused many academic viewpoints to collide with each other. For earth scientists, it is very normal to have different understandings of a geological phenomenon and can better promote each other. "