Why are the original occurrences of sedimentary rocks mostly horizontal?

Sedimentary rocks occur at the bottom of the water and are rock layers formed by the gradual hardening of sediment deposited in the water. For example, the sediment in the Yellow River will only be deposited when the drop is small and the water flow is slowed down, and the bottom of the water is close to the horizontal state, so the original occurrence is naturally mostly horizontal.

The construction of sedimentary rocks (that is, paleosedimentary environments) is mostly underwater sedimentary environments (marine facies, river-lake swamp facies, coastal facies), and then consolidated into rocks, mostly with bedding, and it is impossible if its original occurrence is uneven.

Of course, there are also ice, aeolian and volcanic ash accumulations, and its original occurrence is also close to horizontal.

As for the current state of sedimentary rocks that we see today, it is caused by later tectonic movements.

Sedimentary rocks are formed by weathered detrital matter and dissolved materials through annihilation, sedimentation and diagenesis. The formation process is restricted by the geographical environment and tectonic pattern. The influence of paleogeography on the formation of sedimentary rocks is manifold.

The most obvious are the paleogeographic influences on land and sea, outside and within basins.

Stages of formation of sedimentary rocks:

1.Weathering and denudation stage: due to the long-term weathering and denudation of various rocks on the surface of the earth's crust, the original triangular rocks are gradually broken to form a new weathering product.

2.Transportation stage: Except for a part of the state silver products that have been weathered and denuded, most of the broken materials are transported to other places due to the action of flowing water, wind, glaciers and their own gravity.

3.Deposition stage: When the handling capacity is weakened or the physical and chemical environment changes, the carried material is gradually deposited. Sedimentation can generally be divided into three types: mechanical deposition, chemical deposition and biochemical deposition.

4.Hardening stage: the initial sedimentary loose material is covered by subsequent sediments, and under the action of overlying rock lamination and cemented material, the original material is gradually compacted, the pore is reduced, and the harder rock layer is formed by dehydration and consolidation or re-consolidation.

Sedimentary rocks are rocks formed by the consolidation of loose sediments deposited in layers.

The general process of its formation: when the original sediment is continuously covered by new sediments and thickened, it is isolated from the upper layer of water, and under anaerobic environmental conditions, the organic matter decays and decomposes, and various reducing gases are produced; dissolves carbonate minerals into bicarbonates; Reduction of ** oxides of certain metal elements to low-cost sulfides; At the same time, the salinity of the water in the soft mud increases, and the medium also changes from an acidic oxidation environment to an alkaline reducing environment. As a result, sediments recombine and form new secondary minerals, colloids are dehydrated and aged into solids, and detritals are compressed, cemented, etc., and consolidated into rocks.

Under the condition of deep burial, due to the increase of temperature and pressure and the influence of deep moisture, it can also produce the effects of pressure dissolution, metasomatism and recrystallization, so that the sedimentary rock mass is further compacted and the grain is coarse.

The ** of sediments are the products of weathering of pregenetic rocks on the earth's surface, the sediment of volcanic eruptions, various organic matter of biotic origin, and a small number of landfall from the universe. According to the origin and nature of sediments, they can be divided into the following categories:

1.mechanical (detrital) deposits.

2.Chemical deposits.

3.Organic sediments.

a) Basic characteristics of sedimentary rocks.

The material composition of sedimentary rocks is most different from magmatic rocks in that they are rich in secondary minerals and organic matter and the presence of fossils. The occurrence of sedimentary rocks is characterized by layered production.

Sedimentary rocks have a variety of structures, the most prominent of which are bedding and layering.

Bedding can be generally divided into: 1) horizontal bedding, 2) wavy bedding, and 3) cross-bedding.

Horizontal tectonics refers to the impressions and traces left in the upper and lower layers that are related to the origin of the rocks.

The main structural types of sedimentary rocks are: clastic structure, slow filial piety disadvantage argillaceous disturbance structure, chemical structure and biological structure.

b) The main types of sedimentary rocks.

Among the three major rock types, sedimentary rocks have the most extensive distribution area on the surface (about 70). Sedimentary rocks can be divided into the following categories according to their genesis, material composition and structure:

1.Clastic rocks.

According to the genesis, it can be divided into two types: volcaniclastic rocks and normal clastic rocks.

2.Clay rocks.

3.Biochemical rocks.

Sedimentary rocks are formed by weathered detrital and dissolved materials through transport, sedimentation and diagenesis. The formation process is constrained by the geographical environment and the tectonic pattern of the Yinqing land, the most obvious is the paleogeographic influence of land and sea, outside and within the basin. Sedimentary rocks are formed by weathered detrital and dissolved materials through transport, sedimentation and diagenesis.

The formation process is affected by the geographical environment and tectonic patterns'The most obvious constraints are paleogeographic influences on land and sea, outside and within basins.

Sedimentary rocks are rocks that are deposited and deposited by detritus, organic matter, or chemicals under the action of water or wind. Specifically, its form-forming has gone through the following processes:

1. Erosion and transport: natural forces such as wind, water, and ice in nature will erode the surface of the earth, dispersing boulders, stones, sand and other materials everywhere. These substances are carried away by currents of water or air currents and gradually move elsewhere.

2. Sedimentation: When the migratory material encounters a still water body, it will stop and accumulate together. These sediments can be detrivia, sediment, dust, organic matter, etc.

3. Compaction and solidification: With the continuous accumulation of sediment, the sediment above the Zen sun will compress the sediment below, thus generating pressure. At the same time, the moisture in the sediment is gradually squeezed out, making the sediment denser.

Over time, these sediments have been subjected to sufficient pressure and time to gradually solidify into sedimentary rocks.

4. Metamorphism: Some sedimentary rocks have undergone metamorphism and transformed into metamorphic rocks under the influence of factors such as crustal movement, tectonic changes or thermal action in the earth's interior.

In short, sedimentary rocks are formed through processes of erosion, migration, sedimentation, compaction, and solidification. Among them, sedimentation and compaction are the key links in the formation of sedimentary rocks.

Characteristics of sedimentary rocks

1. Microstructure: sedimentary rocks usually show fine bedding structure and obvious rock chip assemblage. Cuttings of different sizes and shapes, as well as sediments of different colors and textures, are evenly distributed in the rock, forming a unique band texture.

2. Chemical composition: The chemical composition of sedimentary rocks is related to their initial sediments, which usually contain high impurities and organic matter. During the sedimentation process, some ions dissolved in water will be deposited, resulting in sedimentary rocks rich in calcium, magnesium, iron and other elements.

3. Easy stratification: sedimentary rocks have obvious bedding structure, that is, they are formed by the alternating accumulation of different types of sediments. This structure makes it easy for sedimentary rocks to be cut into planar blocks, so it has a wide range of applications in architecture, carving, and decoration.

4. Presence of fossils: Sedimentary rocks usually contain a large number of fossil remains, which are the natural result of their biological activity. Fossils include the fossils of various ancient organisms, such as plant first age, marine organisms, vertebrates, etc., which are of great value for the study of geology and biology.

In conclusion, the characteristics of sedimentary rocks include microstructure, chemical composition, easy stratification, and the presence of fossils, etc., which reflect the formation process and nature of sedimentary rocks.

Sedimentary conglomerate.

Sedimentary rocksIt is a rock composed of clastic material with a grain size in the range of 2 mm. In sandstone, the sand content is usually greater than 50%, and the rest is the base chain and cementitious cavities. The detrital components are mainly quartz and long-called void stone, followed by various rock cuttings and mineral detritus such as mica and chlorite.

The black crystals of the stone are calcite.

It is a rock formed by diagenesis in the process of crustal development and evolution, under the conditions of normal temperature and pressure on the surface or close to the surface of the earth, the products of any pregenetic rock subjected to weathering and denudation, as well as the products of biological and volcanic processes in situ or transported by external forces.

Overview of properties: Sedimentary rocks are rocks formed by the consolidation of loose sediments that are stacked in layers. It used to be called aquamorphic rock.

It is one of the three major rock groups (igneous rocks, sedimentary rocks and metamorphic rocks) that make up the earth's crust. Sediment refers to loose detrital materials such as gravel, paidang, clay, plaster, and biological debris in land or water basins. It is mainly the product of weathering of the parent rock, followed by volcanic eruptions, organic matter, and cosmic matter.

Sedimentary rocks are distributed in the surface layers of the earth's crust. About 75% of the area is exposed on land, and only 25% of igneous and metamorphic rocks. However, the volume of sedimentary rocks in the earth's crust accounts for only about 5%, and the other two types of rocks account for about 95%.

There are many types of sedimentary rocks, the most common of which are shale, sandstone and limestone, which account for 95% of the total number of sedimentary rocks.

The distribution ratio of these three rocks varies with the geological structure and paleogeography of the sedimentary area. In general, shale is the most abundant, followed by sandstone, and limestone is the least abundant. Sedimentary rock formations contain the vast majority of minerals, such as energy, non-metallic, metallic and rare element minerals, followed by fossil groups.

Chemical composition: Varies with the content of major rock-forming minerals in sedimentary rocks. For example, argillaceous rocks are dominated by clay minerals, which are aluminum-silicate minerals, so the total content of SiO2 and Al2O3 in argillaceous rocks is often more than 70%.

Quartz and feldspar are the main ones in sandstone, generally quartz, so the content of SiO2 and Al2O3 can be as high as more than 80%, of which SiO2 can reach 60 95%. Carbonate rocks such as limestone and dolomite, with calcite and dolomite as rock-forming minerals, have a large content of CAO or CAO+MGO, and the content of SiO2, Al2O3 and other contents is less than 10%.