Sedimentary rocks Type details, thank you!!

The clastic composition can be divided into sandstone, argillaceous rock, siltstone, conglomerate, claystone.

In the classification of DU with the source of material as the main consideration, sedimentary rocks are divided into three categories, i.e., by parent rocks

Different sedimentary rocks formed by weathered material, Huozhuan detrital material, and biological remains.

The sedimentary rocks formed by the differentiation products of the parent rocks are the most important types of sedimentary rocks, including clastic rocks and chemical rocks. Clastic rocks are subdivided into conglomerate, sandstone, siltstone, and claystone according to grain size; According to the composition, chemical rocks are mainly divided into carbonate rocks, sulfate rocks, halide rocks, silica rocks and some other chemical rocks.

Biosedimentary rocks are caused by the accumulation of living organisms, such as pollen, spores, shells, corals, etc., which are formed by diagenesis.

The four common sedimentary rocks are sandstone, limestone, shale, and conglomerate.

1.Sandstone

Sandstone is a sedimentary rock, mainly cemented by various sand grains, with a grain diameter, of which the sand grain content is greater than 50%, the structure is stable, usually light brown or red, mainly containing silicon, calcium, clay and iron oxide. The vast majority of sandstone is made up of quartz or feldspar.

2.Limestone

Limestone is referred to as limestone, and it is a carbonate rock with calcite as the main component. Sometimes it contains dolomite, clay minerals and detrital minerals, gray, gray-white orange dates, gray-black, yellow, light red, brown-red and other colors, the hardness is generally not large, and there is a violent chemical reaction with dilute hydrochloric acid. It belongs to sedimentary rocks according to its genetic classification.

3.Shale

Shale is a rock formed by dehydration and cementation of clay. It is mainly composed of clay minerals, and has an obvious thin round layer structure.

According to different compositions, it is divided into carbonaceous shale, calcareous shale, sandy shale, siliceous shale, etc. Among them, the siliceous shale is slightly stronger, the rest is weaker, and the compressive strength of the rock block is or lower.

After immersion in water, it is easy to soften and expand, the deformation modulus is small, and the anti-slip stability is very poor. When shale is sandwiched between two hard rocks, it has a great impact on the stability of the building. It should be paid full attention to in the engineering geological survey.

4.Conglomerate

Conglomerate is a type of rock cemented by round muddy gravel (particle size greater than 2 mm), and is a clastic rock with round and sub-circular gravel accounting for more than 30% of the total rock. The clastic components in the conglomerate are mainly cuttings, with only a small amount of mineral debris, and the gap fillers are sand, silt, clay and chemical precipitates.

Knowledge Expansion:

Sedimentary rocks are one of the three major rock groups, also known as aquapogenesis, and are one of the three main rocks that make up the Earth's lithosphere (the other two are magmatic rocks and metamorphic rocks).

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.

On the Earth's surface, 70% of the rocks are sedimentary, but only 5% are sedimentary if you count the entire lithosphere from the Earth's surface to a depth of 16 kilometers. Sedimentary rocks mainly include limestone, sandstone, shale, etc. Sedimentary rocks contain minerals that account for 80% of the world's total mineral reserves.

Sedimentary rock. It is mainly divided into: conglomerate, sandstone, siltstone, carbonate rock (the common rock types are limestone and dolomite.)

Clastic rocks, clastic sedimentary rocks, biosedimentary rocks, etc.

1.Terrigenous clastic rocks (sandstone, conglomerate,).

2.Claystone (mudstone, shale, clay).

3.Volcaniclastic rocks (tuff, volcanic breccia, agglomerates) 4Carbonate rocks (limestone, dolomite).

Multiple stratigraphic units are divided, and the groups, sections and layers of rock strata are the basic units of geological mapping in sedimentary rock areas, especially the sections, strata, informal and special mapping units are the entities of lithological mapping. Through the mapping of formal and informal rock stratigraphic units, the temporal and spatial existence (including morphology, geometric relationship and arrangement law), longitudinal and horizontal variation, interrelationship with other types (especially chronological units) and regional stratigraphic framework are identified. Find out the lithology, main material composition and geochemical characteristics, basic sequence, fossils, sedimentary characteristics (structure, tectonic characteristics), thickness, occurrence, morphology, genesis, minerality, contact relationship, temporal and spatial distribution and changes of rock stratigraphic units. Correctly establish stratigraphic sequences, reasonably divide formal, informal and special rock stratigraphic units, study their relationship with biostratigraphic units and chronostratigraphic units, and conduct division and comparative research on multiple stratigraphic units.

Carry out research on sedimentary facies, sedimentary environment, sedimentation and the formation and development of sedimentary rock layers, establish stratigraphic models, and clarify the formation age, environment, sedimentation of each rock stratigraphic unit, the relationship with other stratigraphic units, as well as the distribution law of regional geological development history and natural resources.

The new mapping method system adopts the multiple stratigraphic division method, strictly defines the rock stratigraphic unit, and clearly stipulates that the rock stratigraphic unit group is the basic formal unit of mapping. As we all know, lithology is an objective entity, which does not vary from person to person and does not change easily, so the map is stable and unchanged. The new method also vigorously advocates the use of informal rock stratigraphic units to fill in the map as much as possible, which enriches the content of the map and increases the geological and mineral information, which can greatly meet the needs of users and fully reflect the nature of "public welfare".

According to the characteristics of sedimentary rocks, such as material**, genesis and material composition, sedimentary rocks can be divided into the types listed in Table 5 1.

Table 5-1 Classification of sedimentary rocks.

It should be noted that if we want to trace the previous generation of endogenous materials, they are also formed by chemical or biochemical precipitation of terrigenous and partly volcanic** dissolved materials in sedimentary basins. Therefore, the endogenous rock system defined in this textbook refers to the minerals formed by the combination of dissolved materials in the water body in the sedimentary basin and the sediments and sedimentary rocks formed by precipitation.

The focus of this book is on terrigenous sedimentary rocks and carbonate rocks, and only some of these types are covered in other endogenous rocks, such as volcaniclastic rocks in the preceding magmatic rocks, but not organic combustible rocks and other economic rocks.