Conglomerate Rock in Geology – Meaning, Uses, Facts, & Color

Clasts:

In conglomerate rocks, the main framework grains are clasts, and those are always rounded or semi-rounded in shapes. [If clasts in a sedimentary rock have sharp corners, it is known as Breccia.] If a mixture of both kinds of clasts occurs in sedimentary rock, it refers to Breccia—Conglomerate Rock.

• Rounded clasts may be mineral particles including Feldspar or Quartz.
• The clasts may be fragments of Metamorphic or Igneous rocks.
• The most common rocks forming clasts are
  • Quartzite
  • Sandstone
  • Limestone
  • Granite
  • Basalt
  • Gneiss

Matrix:

The following components are forming a matrix of the conglomerate rocks.

• Sand
• Silt
• Clay/mud
• Chemical cement

Cementing chemicals like NaCl and CaO bind the clasts together.

Asia:

• China
• India
• Kazakhstan
• Mongolia
• Russia
• Uzbekistan

Africa:

• Namibia
• Nigeria
• South Africa

Europe:

• Austria
• Denmark
• Germany
• Great Britain
• Netherlands
• Norway
• Poland
• Sweden
• Switzerland
• United Kingdom

North America:

• Canada
• USA

South America:

• Brazil

• New South Wales
• New Zealand

It is a matrix-supported type of conglomerate rock. When the percentage of the matrix in the rock is at least 15% and more, it terms as matrix supported.

This type of rocks is further classified into laminated (Cemented Clasts) & non-laminated. Tillites & Tilloids are respective examples of both.

On the contrary, these types of rocks have less than 15% matrix, and mass is dominated with clasts. Therefore, its terms as a clasts-supported conglomerate.

Many natural stones have less withstanding capacities against weathering than others. When such clasts are present in conglomerate rocks those term as Petromict. Limestone, dolomite, shale, and similar stone clasts have low resistance power.

On the contrary, some clasts have high-resistance capacities and withstand against natural erosion and weathering impacts. For instance, quartz, chert, basalt, and others. When such clasts exist in the rock, those are term as Oligomict conglomerates.

When conglomerate rocks have the same kind of clasts and matrix, which originated from the same environment, those term as intraformational conglomerates. For example, a siliceous matrix with quartz and jasper clasts. Here, both rocks are of siliceous types and embedded into the siliceous matrix.

On the contrary, extra formational conglomerate rocks have different origin or types of clasts than the matrix. It is because clasts have transported from a kind of rock type area during matrix from another area. For instance, basalt clasts transported in a calcareous matrix area.

The same types of clasts found in the rock or parent material, it is monomictic conglomerates. Here, Mono means single and same.

When clasts are consisting of two types of parent rocks, it is a diamictic conglomerate. Here, Di- means two. For instance, quartz and Jasper clasts type found in the same conglomerate rock.

When numerous types of clasts exist in the same conglomerate rock, it is a polymictic conglomerate. Here, Poly- means many or multiple. For instance, quartz, basalt, limestone, and chert types of clasts are existing in the same conglomerate rock.

Clasts size greater than 256 mm

Clasts size in the range of 64-256 mm

Clasts size between 4-64 mm

Clasts size between 2-4 mm

The resulting rocks have an inter-growth texture between the clasts, which used to found in low-metamorphosed stones. For example, when a sandstone converted to marble and clay in the rocks turned into slate.

Such metamorphosed conglomerate rocks are known as Meta-conglomerate.

Shallow Water Marine Environment:

At the coastal beach where the rocky edge is present, or river delta occurs, oceanic tidal waves are tumbling the gravels and pebbles and make well-rounded clasts with back-forth movements of water ripples. The deposition takes place with the pace of time and forms conglomerate rocks at the beach.

Similarly, in the lagoon, the formation of well-rounded, well-sorted, and fine-grained clasts takes place, and depositions along with sands, slits, and mud resulting in conglomerate rocks at the sea bed, coastal edges, and reef edges.

Deep Water Marine Environment:

At the delta region of a river mouth, clasts flow along with river flood currents and settle in the deep sea with each flood flow. It resulting into smaller but rounded and silt, clay, and sand rich conglomerate depositions in the deeper section of the sea.

Glacial Environment:

In high mountains, snow deposited during winter and forms glacial rivers or sheets of ice, which slowly flows toward the glacier mouth.

During the ice formation, the sediments that fall on the surface are being plucked by the solid ice and carrying along with during the journey of glacial mass.

When ice melts at the mouth, the “Glacial Till” is depositing on the ground and clasts are forming conglomerate rocks over time. Rocks are sorted poorly and coarse-grained in nature.

Alluvial Environment:

At the mountain front, streams are moving fast and empty in the plane lands. Force of water or water movement is slowing down, and water is dispersing in a broad area.

It eventually is resulting in depositions of mostly large and some small clasts. With the pace of time sedimentation process takes place and conglomerate rocks form.

Fluvial Environment:

In Latin, fluvial mean riverine environment. During floods in the river, a variety of clasts tumbled and transported further. Deposition of the moving mass takes place in the period in between the floods.
Transportation takes place for a long period, so it is resulting in the sorting and shredding of the size of clasts further, it makes clasts smaller more rounded in shape than at the upper stream of the river.

Therefore, the lacustrine environment yields graded bedding of conglomerate deposits.

In Construction of Historic Buildings:

Near Barcelona, Spain, The Santa Maria de Montserrat Abbey was constructed using Conglomerate rocks obtained from Montserrat.

In Preparation of Construction of Aggregates:

Crushed conglomerates are excellent construction aggregate material for road and building construction industries. Conglomerates also used in cement manufacturing industry.

As Dimension Stones:

Conglomerates with smaller clasts size can cut easily in required shapes. If those are with good cementing material, the application as dimension stone for flooring and veneer on walls and roof tiles is possible.

As Decorative Material in interior and Exterior Application:

Clasts of conglomerate rocks have different parent material from a variety of natural stones. Therefore, those are coming in different colors, textures, and styles.

When cut in the right ways, these conglomerate rocks prove a decent decorative material for interior and exterior application in building construction industry.

As Architectural Stones for Curbing:

The entrance front always demands something different and unique to create great curbing appeal, and a conglomerate of different types provides enough options to go using the reliable and right materials.

As Antiquity Material:

Conglomerates are providing the best material for artifacts, monuments, sculpture formation, and in the creation of small figurines.

In Other Commercial Applications:

In the past and present, conglomerate rocks are in use for cemetery markers, in the construction of aquifers, and tombstones.