Conglomerate

Classification：Sedimentary Rock

Rock formed by lithitization of round rock fragments or mineral particles larger than 2mm. There are smaller particles in the gap of
conglomerate. The environment formed by river bed, cobblestone beach or other debris is circular.

Conglomerate is a sedimentary rock, broken down from the parent rock, the particle diameter more than 2 millimeter, through transport, deposition, compaction, cementation, the formation of rock, the average diameter of gravel in 1-10 millimeters, fine gravel, 10-100 millimeter called coarse gravel, more than 100 millimeter as boulder. Conglomerate may also be a clastic rock. Its cements often contain minerals, and Conglomerate can be used as building materials. Conglomerate is rough, and it can see obvious gravel. If the gravel that has been cemented has edges and corners, it is called angle Conglomerate.

The circular and sub circular gravel with a diameter larger than 2 mm takes up more than 30% of the total amount of clastic rock. The detrital components in Conglomerate are mainly cuttings, with only a small amount of mineral clasts. The interstitial products are sand, silt, clay and chemical precipitates. According to the size of the gravel, Conglomerate is divided into Boulder (>256 mm) Conglomerate, large boulder (64~256 mm) Conglomerate, pebble (4~64 mm) Conglomerate and fine gravel (2~4 mm) Conglomerate. According to the complexity of gravel composition, Conglomerate can be divided into single component Conglomerate and compound Conglomerate. According to the location of Conglomerate in geological section, it can be divided into bottom Conglomerate and interlayer Conglomerate. The bottom Conglomerate is located at the bottom of transgressive sequence, which is unconformity or falsely contact with underlying rocks, representing a sedimentary gap in a certain geological period. Such as Tangshan, Hebei, Sinian bottom, the Great Wall, quartzite Conglomerate. The interlayer Conglomerate integration is located inside the formation, and does not represent any erosion interruption. Such as North China Cambrian and Ordovician bamboo leaf limestone.

The cause of formation:
The formation of Conglomerate depends on 3 conditions:
1. There are source areas for the supply of debris;
2. There is a flow of water enough to carry debris.
3. A sedimentary area with gradual attenuating energy.
Therefore, in the mountainous area with steep terrain and dry climate, the active fault scarp and the backward rocky shore are favorable conditions for the formation of Conglomerate. The thick Conglomerate layer is usually formed after large-scale orogeny. It is a strong evidence for the strong crust uplift. The composition, structure and arrangement of gravel of Conglomerate and the form of Conglomerate body reflect the natural conditions such as the composition of the parent rock, the velocity of denudation and deposition, the moving distance, the direction of the flow and the boundary of the basin. The closer the basin boundary is, the larger the particle size of sediments is, the higher the total content of terrigenous clasts. These researches on lithofacies and palaeogeography are very important. In addition, the palaeo gravel layer is often an important reservoir, and the Conglomerate's fillings are often gold, platinum, diamond and other precious minerals, and Conglomerate can also be used as a building material.

Classification:
The Conglomerate of different genesis has obvious difference in the composition maturity, grain size distribution, shape and roundness surface characteristics of gravel, and the spatial arrangement of gravel. According to 4 genetic markers of support type, sorting, fabric and sedimentary creation, Conglomerate can be divided into 6 genetic types. In the genetic classification of F.J. Pei Zhuang's Conglomerate and corner Conglomerate, the rock is first classified as force and debris source, and the rocks are divided into 4 categories, namely, external clastic, pyroclastic, crushing and meteorites; secondly, according to the source of debris, the external detritus is divided into layers and layers; and then according to the number of impurities. We further divide the intra layer Conglomerate into positive Conglomerate and sub Conglomerate (see table).
The normal quartzite Conglomerate is mainly composed of high stability quartzite and a small amount of flint, quartz and other debris. It is supported by particles, and has fewer fillings and is often cemented by siliceous. Gravel good sorting, high roundness, gravel particle size smaller, thinner layer thickness Conglomerate. Quartzite Conglomerate often forms bottom Conglomerate. There are quartzite Conglomerate at the bottom of the Great Wall in northern China. The gravel compositions of Conglomerate are mostly unstable components, such as Xuan Wuyan, granite and limestone. The gravel size of the debris Conglomerate is larger, the thickness of the Conglomerate layer is larger, the gravel separation and the roundness are poor, which reflects that the debris is not far away, and it is often accumulated rapidly in the edge of the basin or in the adjacent area. Most of the cuttings Conglomerate are continental origin. The lamellar clastic mudstone contains coarse and granular detritus, with hetero base having lamination, and laminae convex and concave on the larger gravel. This rock is often symbiotic with moraine. If the dispersed gravel crumbs are embedded in the miscellaneous base without lamination, the mudstone is called massive gravelly mudstone, which is mainly underwater gravity flow deposition. If the rock blocks with polished surfaces and scratches, the instructions for the glacial origin. The gravel of the river Conglomerate is usually complex and stable and unstable. The debris separation is poor, the roundness is low, the long axis is perpendicular to the direction of the flow, the flat surface of the gravel tends to be upstream, and the dip angle is generally 15 to 30 degrees, and the bottom of the Conglomerate body often has a erosion surface. The shoreline Conglomerate is formed in the coastal area and Binhu area. The gravel composition is single, most of which are hard rock. The separation is good, the roundness is high, the long axis is parallel to the direction of the shore line, the largest flat is inclined to the sea direction, and the dip angle is generally 7 to 8 degrees. The Conglomerate layer usually occurs as thin lens, and is often associated with quartz sandstone. Coastal Conglomerate contains marine fossils.
According to geological conditions and formation conditions, Conglomerate has many other types. Debris flows with large viscosity developed in large areas with large elevation, and slide along slopes, can form debris flows Conglomerate and Conglomerate. The coarse debris transported by the river is stacked on the Piedmont slopes of the Piedmont, forming fan Conglomerate and angle Conglomerate. Glacial action can form moraine Conglomerate and angle Conglomerate. The typical moraine angle Conglomerate is not sorted, and the sharp edges and corners of the gravel are typical "Ding" scratches in the part of moraine Conglomerate.