In geology, conglomerate refers to a coarse-grained sedimentary rock that resembles concrete. Conglomerate is considered a clastic rock because it contains an abundance of gravel-sized (greater than 2 mm diameter) pebbles called clasts. Sand, silt, or clay sediment, called matrix, fills the spaces between the clasts and cements them together Show Conglomerate is relatively uncommon. In fact, geologists estimate only about one percent of all sedimentary rock is conglomerate.
Over time, pebbles on a beach may form conglomerate rock. Howard Pugh (Marais) / Getty Images Conglomerate rock forms when gravel or even boulders are transported far enough from their original source to become rounded, or are subjected to wave action. Calcite, silica, or iron oxide fills in the spaces between the pebbles, cementing them together. Sometimes all the clasts in conglomerate are the same size, but usually there are smaller pebbles filling in part of the spaces between larger clasts. Regions likely to produce conglomerate include beaches, riverbeds, and glaciers.
The following characteristics are used to classify and categorize conglomerate rock:
The key characteristic of conglomerate is the presence of readily visible, rounded clasts bound within a matrix. The clasts tend to feel smooth to the touch, although the matrix can be either rough or smooth. The hardness and color of the rock is highly variable. When the matrix is soft, conglomerate may be crushed for use as a fill material in the construction and transportation industries. Hard conglomerate may be cut and polished to make dimension stone for interesting-looking walls and floors. Santa Maria de Montserrat Abbey, Barcelona, Spain was built from conglomerate rock. Paul Biris / Getty Images Conglomerate rock is found in areas where water once flowed or where glaciers were found, such as Death Valley National Park, the cliffs along the east coast of Scotland, the dome-shaped hills of Kata Tjuta in Australia, the underlying anthracite of the coal fields of Pennsylvania, and the base of the Sangre de Cristo mountains of Colorado. Sometimes the rock is strong enough to be used for construction. For example, The Santa Maria de Montserrat Abbey was constructed using conglomerate from Montserrat, near Barcelona, Spain. Conglomerate rock on Mars (left) compared with conglomerate on Earth (right). NASA Mars Curiosity Rover Earth isn't the only place to find conglomerate rock. In 2012, NASA's Mars Curiosity Rover captured photographs of conglomerate rock and sandstone on the Martian surface. The presence of conglomerate is compelling evidence that Mars once had flowing water: the pebbles in the rock are rounded, indicating they were transported along a current and rubbed against one another. (Wind isn't strong enough to move pebbles this large.) Conglomerate has rounded clasts, while breccia contains angular clasts. Scientifica / Getty Images Conglomerate and breccia are two closely related sedimentary rocks, but they differ significantly in the shape of their clasts. The clasts in conglomerate are rounded or at least partially rounded, whereas the clasts in breccia have sharp corners. Sometimes sedimentary rock contains a mixture of round and angular clasts. This type of rock may be called breccio-conglomerate.
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Conglomerate is a clastic sedimentary rock that shaped from rounded gravel and boulder sized clasts cemented or in a matrix supperted. The rounding of the clasts show that rocks have been transported a long way from their source or on a seaside tide to wave movement. The clast cement is usually calcite, silica or iron oxide but the matrix can consist only of the cementing cloth, however can also include sand and / or silt sized clasts cemented together the various coarser clasts. Class: Conglomerate may be divided into large lessons: Texture: Clastic (coarse-grained). Grain size: > 2mm; Clasts easily visible to the naked eye, should be identifiable. Hardness: Soft to hard, dependent on clast composition and strength of cement. Colour: variable, dependent on clast and matrix composition. Clasts: variable, but generally harder rock types and / or minerals dominate. Other features: Clasts generally smooth to touch, matrix variable. Classification of ConglomerateConglomerates named and classifield by the
A sedimentary rock consisting mainly of gravel is first named according to the roundness of the gravel. If the gravel clasts that form it are well-rounded to subrounded, to a large extent, it is a conglomerate. If the pebble clips forming it are largely angular, it is a breccia. Such breccias may be called sedimentary breccias to distinguish them from other breccia types.
The environment that deposited the material. Conglomerates may form from glacial, alluvial, fluvial, deepwater marine, or shallow marine environments. Conglomerate CompositionConglomerate can have a variety of compositions. As a clastic sedimentary rock, it can contain clasts of any rock material or weathering product that is washed downstream or down current. The rounded clasts of conglomerate can be mineral particles such as quartz, or they can be sedimentary, metamorphic, or igneous rock fragments. The matrix that binds the large clasts together can be a mixture of sand, mud, and chemical cement. FormationConglomerate can be formed at an areas where strong water current exist like mountain down slope where water has enough current flow that it can carry the rock fragments above 2 millimetre. It can also be formed at beaches where water current is strong and rock fragments are available to be accumulated for forming conglomerate. Conglomerate is formed when large clast pebble or cobble size fragments transported and deposited than the finer grained fills the spaces in between the clast. Where is it foundConglomerates are deposited in various sedimentary environments. Deepwater marineIn turbidites, the basal part of a bed is typically coarse-grained and sometimes conglomeratic. In this setting, conglomerates are normally very well sorted, well-rounded and often with a strong A-axis type imbrication of the clasts. Shallow marineConglomerates are normally present at the base of sequences laid down during marine transgressions above an unconformity, and are known as basal conglomerates. They represent the position of the shoreline at a particular time and are diachronous. FluvialConglomerates deposited in fluvial environments are typically well rounded and well sorted. Clasts of this size are carried as bedload and only at times of high flow-rate. The maximum clast size decreases as the clasts are transported further due to attrition, so conglomerates are more characteristic of immature river systems. In the sediments deposited by mature rivers, conglomerates are generally confined to the basal part of a channel fill where they are known as pebble lags. Conglomerates deposited in a fluvial environment often have an AB-plane type imbrication. AlluvialAlluvial deposits form in areas of high relief and are typically coarse-grained. At mountain fronts individual alluvial fans merge to form braidplains and these two environments are associated with the thickest deposits of conglomerates. The bulk of conglomerates deposited in this setting are clast-supported with a strong AB-plane imbrication. Matrix-supported conglomerates, as a result of debris-flow deposition, are quite commonly associated with many alluvial fans. When such conglomerates accumulate within an alluvial fan, in rapidly eroding (e.g., desert) environments, the resulting rock unit is often called a fanglomerate. GlacialGlaciers carry a lot of coarse-grained material and many glacial deposits are conglomeratic. Tillites, the sediments deposited directly by a glacier, are typically poorly sorted, matrix-supported conglomerates. The matrix is generally fine-grained, consisting of finely milled rock fragments. Waterlaid deposits associated with glaciers are often conglomeratic, forming structures such as eskers. Characteristics and PropertiesConglomerate is a sedimentary rock that looks like concrete. It consists of large, rounded pebbles (clasts) cemented by a matrix made of calcite, iron oxide, or silica. Conglomerate rock occurs where gravel can become rounded by traveling distances or being subjected to tumbling. Beaches, riverbeds, and glaciers can produce conglomerate. The properties of conglomerate rock depend on its composition. It can be found in any color and may be either hard or soft. Conglomerate can be used as a fill material for roads and construction. Hard rock may be cut and polished to make dimension stone. Conglomerate UsesConglomerate has very few uses because of it not clean breakage and fine particles are unreliable. It can only be used as a crush where low performance material is wanted. Conglomerate has very few commercial uses. Its inability to break cleanly makes it a poor candidate for dimension stone, and its variable composition makes it a rock of unreliable physical strength and durability. Conglomerate can be crushed to make a fine aggregate that can be used where a low-performance material is suitable. Many conglomerates are colorful and attractive rocks, but they are only rarely used as an ornamental stone for interior use. Analysis of conglomerate can sometimes be used as a prospecting tool. For example, most diamond deposits are hosted in kimberlite. If a conglomerate contains clasts of kimberlite, then the source of that kimberlite must be somewhere upstream. Conglomerate and BrecciaConglomerates and breccias are two sedimentary rocks close to each other, but differ significantly in the form of clasts. Clasts in the conglomerate are rounded or at least partially rounded, whereas the clast in the breccias have sharp corners. Sometimes sedimentary rocks contain a mixture of round and angled buckles. This type of rock can be called breccio-conglomerate. Facts
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