Conglomerate (geology)

Classification of Conglomerates: Named and classified by amount and type of matrix present. Classified by composition of gravelsize clasts they contain. Sorted based on size range of gravelsize clasts present. Method depends on type and detail of research being conducted. Named according to roundness of gravel. Conglomerate Texture: Contains at least 30% of rounded to subangular clasts larger than 2mm in diameter. Space between clasts filled by a mixture of silt, sand, and clay known as matrix. Paraconglomerates have gravel clasts floating within the matrix. Orthoconglomerates are typically crossbedded and wellcemented. Reflect differences in deposition: paraconglomerates often glacial tills or debris flow deposits, while orthoconglomerates are associated with aqueous currents. Clast Composition: Classified by composition of clasts as monomict, oligomict, or polymict conglomerates. Source indicated by lithology of gravelsize clasts. Extraformational conglomerates have clasts significantly different from matrix. Intraformational conglomerates have clasts consistent with matrix lithology. Two types: shalepebble and flatpebble conglomerates. Sedimentary Environments: Deposited in deepwater marine, shallow marine, fluvial, alluvial, and glacial environments. Turbidites in deepwater marine settings have wellsorted conglomerates. Basal conglomerates in shallow marine settings represent shoreline positions. Fluvial conglomerates are well rounded and poorly sorted. Fanglomerates in alluvial environments are associated with debrisflow deposition. Examples and Miscellaneous: Various examples of conglomerates found on Earth and Mars. Metaconglomerate: Metamorphic alteration changes conglomerate into metaconglomerate. Related concepts: Puddingstone, Jasper conglomerate. References for further reading on sedimentology and stratigraphy.