Volcaniclastics are geologic materials composed of broken fragments (clasts) of volcanic rock.[1] These encompass all clastic volcanic materials, regardless of what process fragmented the rock, how it was subsequently transported, what environment it was deposited in, or whether nonvolcanic material is mingled with the volcanic clasts.[2] The United States Geological Survey defines volcaniclastics somewhat more narrowly, to include only rock composed of volcanic rock fragments that have been transported some distance from their place of origin.[3]
The Espinaso Formation includes a wide variety of volcaniclastic materials.
Volcaniclastics make up more of the volume of many volcanoes than do lava flows. Volcaniclastics may have contributed as much as a third of all sedimentation in the geologic record.[2]
Volcaniclastics are composed of a range of pyroclastic detritus mixed with epiclastic sediments and formed in variable depositional environments.[7][8] Volcaniclastics include pyroclastic rock and tephra; volcanic autoclastic, alloclastic, and epiclastic materials; and fault gouge where faults displace volcanic rock.[2] All are defined below. These can be divided into primary volcaniclastics and secondary volcaniclastics (epivolcaniclastics).[9]
Primary versus secondary volcaniclastic rocks
Primary volcaniclastic deposits
(Characteristic clasts must be more than 75% of volume)
Pyroclastic material is composed of rock fragments produced by explosive volcanism and erupted from the vent as individual particles,[1] without reference to the particle origin or the nature of the eruption.[2] These may include particles of country rock entrained within the vent.[10] Accumulations of pyroclastic material that have not been consolidated are described as tephra, while those that have undergone significant consolidation are described as pyroclastic rock.[2][11] Hydroclastic material is a special case of pyroclastic material produced by a variety of processes at magma-water interfaces.[1]
Autoclasticedit
'A'a lava flow with capping breccia at Kīlauea volcano
Autoclastic volcanic material is produced by processes active during movement of solid or semisolid lava. These include rock fragments that are produced within volcanic vents but not extruded,[1] rock fragments produced by motion or gas explosions within volcanic flows, or rock fragments produced by gravitational collapse of lava domes or spines.[2] The characteristic basal and capping breccia of ʻaʻā lava flows[12] are autoclastic volcaniclastics.
Other kinds of volcaniclastic materialedit
Alloclastic volcanic material is formed by fragmentation of existing igneous rock by subsurface igneous activity that may or may not involve magma intrusions. Fault gouge produced by motion along a fault in volcanic rock is also a type of volcaniclastic material.[2]
Epivolcaniclasticsedit
Volcanic epiclastic material (epivolcaniclastics[13]) contains a substantial fraction of epiclasts (rock fragments produced by weathering and erosion) derived from volcanic rock.[2]
Mixed pyroclastic-epiclastic rocksedit
The Washburn Group of Yellowstone National Park includes volcaniclastic conglomerate.Tuffaceous sandstone layers in New Mexico
Deposits containing pyroclastic material that has been reworked in stream or lake environments or mingled with epiclastic material (whether volcanic or nonvolcanic) pose a special difficulty and are among the materials most usefully described simply as volcaniclastic.[14] A more specific classification is problematic for these cases.[11][15][16] The Espinaso Formation of New Mexico is an example of a rock unit that is composed of a complex mixture of pyroclastic and volcanic epiclastic material and so is described simply as volcaniclastic.[17] Another is the Washburn Group of the Yellowstone area, which includes debris flows of reworked volcanic ash and volcanic epiclastic rock.[18]
Mixed pyroclastic-epiclastic deposits may be classified by average clast size and percentage of pyroclastic material.[11]
^ abcdFisher, Richard V. (1961). "Proposed classification of volcaniclastic sediments and rocks". Geological Society of America Bulletin. 72 (9): 1409. Bibcode:1961GSAB...72.1409F. doi:10.1130/0016-7606(1961)72[1409:PCOVSA]2.0.CO;2.
^"Volcaniclastic". Volcanic Hazards Program. United States Geological Survey. 2012. Retrieved 28 September 2020.
^Vincent, Pierre (2000). Volcaniclastic rocks, from magmas to sediments(PDF). Amsterdam, the Netherlands: Gordon and Breach Science Publishers. p. 1. ISBN9056992783. Retrieved 28 September 2020.
^Ross, Clarence S.; Smith, Robert L. (1961). "Ash-flow tuffs: Their origin, geologic relations, and identification". USGS Profession Paper Series. Professional Paper (366). doi:10.3133/pp366.
^De Ros, L. F., S. Morad, and I. S. Al-Aasm, 1997, Diagenesis of siliciclastic and volcaniclastic sediments in the Cretaceous and Miocene sequences of the NWAfrican margin (DSDP Leg 47A, Site 397): Sedimentary Geology, v. 112, no. 1–2, p. 137–156,
^Olavsd�ottir, J., M. S. Andersen, and L. O. Boldreel, 2015, Reservoir quality of intrabasalt volcaniclastic units onshore Faroe Islands, North Atlantic Igneous Province, northeast Atlantic: AAPG Bulletin, v. 99, no. 3, p. 467– 497,
^ abcSchmidt, R. (1981). "Descriptive nomenclature and classification of pyroclastic deposits and fragments: recommendations of the IUGS Subcommission on the Systematics of Igneous Rocks". Geology. 9: 41–43. doi:10.1007/BF01822152. S2CID 128375559. Retrieved 27 September 2020.
^Schmincke, Hans-Ulrich (2003). Volcanism. Berlin: Springer. p. 130. ISBN9783540436508.
^Schmincke, Hans-Ulrich (2003). Volcanism. Berlin: Springer. pp. 137–138. ISBN9783540436508.
^Kautz, P. F.; Ingersoll, R. V.; Baldridge, W. S.; Damon, P. E.; Shafiqullah, M. (December 1981). "Geology of the Espinaso Formation (Oligocene), North-Central New Mexico". GSA Bulletin. 92 (12_Part_II): 2318–2400. Bibcode:1981GSAB...92.2318K. doi:10.1130/GSAB-P2-92-2318.
^Smedes, H.W.; Prostka, H.J. (1972). "Stratigraphic framework of the Absaroka Volcanic Supergroup in the Yellowstone National Park region". U.S. Geological Survey Professional Paper. Professional Paper. 729-C: C-19. doi:10.3133/pp729C.
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January 01, 1970
volcaniclastics, geologic, materials, composed, broken, fragments, clasts, volcanic, rock, these, encompass, clastic, volcanic, materials, regardless, what, process, fragmented, rock, subsequently, transported, what, environment, deposited, whether, nonvolcani. Volcaniclastics are geologic materials composed of broken fragments clasts of volcanic rock 1 These encompass all clastic volcanic materials regardless of what process fragmented the rock how it was subsequently transported what environment it was deposited in or whether nonvolcanic material is mingled with the volcanic clasts 2 The United States Geological Survey defines volcaniclastics somewhat more narrowly to include only rock composed of volcanic rock fragments that have been transported some distance from their place of origin 3 The Espinaso Formation includes a wide variety of volcaniclastic materials In the broad sense 2 4 of the term volcaniclastics includes pyroclastic rocks such as the Bandelier Tuff 5 cinder cones and other tephra deposits the basal and capping breccia that characterize ʻaʻa lava flows and lahars and debris flows of volcanic origin 6 Volcaniclastics make up more of the volume of many volcanoes than do lava flows Volcaniclastics may have contributed as much as a third of all sedimentation in the geologic record 2 Contents 1 Classification of volcaniclastics 1 1 Pyroclastic 1 2 Autoclastic 1 3 Other kinds of volcaniclastic material 1 4 Epivolcaniclastics 1 5 Mixed pyroclastic epiclastic rocks 2 See also 3 ReferencesClassification of volcaniclastics editVolcaniclastics are composed of a range of pyroclastic detritus mixed with epiclastic sediments and formed in variable depositional environments 7 8 Volcaniclastics include pyroclastic rock and tephra volcanic autoclastic alloclastic and epiclastic materials and fault gouge where faults displace volcanic rock 2 All are defined below These can be divided into primary volcaniclastics and secondary volcaniclastics epivolcaniclastics 9 Primary versus secondary volcaniclastic rocks Primary volcaniclastic deposits Characteristic clasts must be more than 75 of volume Secondary volcanic deposits epivolcaniclastic deposits Pyroclastic tuff or tephra Pyroclastic deposit Autoclastic rock or loose deposit Hyaloclastic rock or loose deposit Hyaloclastite Redeposited pyroclastic tephra Redeposited autoclastic loose deposit Redeposited hyaloclastic loose deposit Epiclastic deposits have more than 75 epiclasts in the general case They are epivolcanicastic deposits if they have recognizable volcanic fragments in any proportion Pyroclastic edit nbsp The Bandelier Tuff is an example of a pyroclastic rock formation Main articles Tephra and Pyroclastic rock Pyroclastic material is composed of rock fragments produced by explosive volcanism and erupted from the vent as individual particles 1 without reference to the particle origin or the nature of the eruption 2 These may include particles of country rock entrained within the vent 10 Accumulations of pyroclastic material that have not been consolidated are described as tephra while those that have undergone significant consolidation are described as pyroclastic rock 2 11 Hydroclastic material is a special case of pyroclastic material produced by a variety of processes at magma water interfaces 1 Autoclastic edit nbsp A a lava flow with capping breccia at Kilauea volcano Autoclastic volcanic material is produced by processes active during movement of solid or semisolid lava These include rock fragments that are produced within volcanic vents but not extruded 1 rock fragments produced by motion or gas explosions within volcanic flows or rock fragments produced by gravitational collapse of lava domes or spines 2 The characteristic basal and capping breccia of ʻaʻa lava flows 12 are autoclastic volcaniclastics Other kinds of volcaniclastic material edit Alloclastic volcanic material is formed by fragmentation of existing igneous rock by subsurface igneous activity that may or may not involve magma intrusions Fault gouge produced by motion along a fault in volcanic rock is also a type of volcaniclastic material 2 Epivolcaniclastics edit Volcanic epiclastic material epivolcaniclastics 13 contains a substantial fraction of epiclasts rock fragments produced by weathering and erosion derived from volcanic rock 2 Mixed pyroclastic epiclastic rocks edit nbsp The Washburn Group of Yellowstone National Park includes volcaniclastic conglomerate nbsp Tuffaceous sandstone layers in New Mexico Deposits containing pyroclastic material that has been reworked in stream or lake environments or mingled with epiclastic material whether volcanic or nonvolcanic pose a special difficulty and are among the materials most usefully described simply as volcaniclastic 14 A more specific classification is problematic for these cases 11 15 16 The Espinaso Formation of New Mexico is an example of a rock unit that is composed of a complex mixture of pyroclastic and volcanic epiclastic material and so is described simply as volcaniclastic 17 Another is the Washburn Group of the Yellowstone area which includes debris flows of reworked volcanic ash and volcanic epiclastic rock 18 Mixed pyroclastic epiclastic deposits may be classified by average clast size and percentage of pyroclastic material 11 Terms for mixed pyroclastic epiclastic rocks Pyroclastic Tuffites mixed pyroclastic epiclastic Epiclastic volcanic or nonvolcanic Average clast size mm Agglomerate agglutinate pyroclastic breccia Tuffaceous conglomerate tuffaceous breccia Conglomerate Breccia gt 64 Lapillistone 2 64 Coarse ash tuff Tuffaceous sandstone Sandstone 0 0625 2 Fine ash tuff Tuffaceous siltstone Siltstone 0 004 0 0625 Tuffaceous mudstone tuffaceous shale Mudstone shale lt 0 004 75 100 pyroclasts 25 75 pyroclasts 0 25 pyroclastsSee also editPeperite TuffiteReferences edit a b c d Fisher Richard V 1961 Proposed classification of volcaniclastic sediments and rocks Geological Society of America Bulletin 72 9 1409 Bibcode 1961GSAB 72 1409F doi 10 1130 0016 7606 1961 72 1409 PCOVSA 2 0 CO 2 a b c d e f g h i Fisher Richard V Schminke H U 1984 Pyroclastic rocks Berlin Springer Verlag ISBN 3540127569 Volcaniclastic Volcanic Hazards Program United States Geological Survey 2012 Retrieved 28 September 2020 Vincent Pierre 2000 Volcaniclastic rocks from magmas to sediments PDF Amsterdam the Netherlands Gordon and Breach Science Publishers p 1 ISBN 9056992783 Retrieved 28 September 2020 Ross Clarence S Smith Robert L 1961 Ash flow tuffs Their origin geologic relations and identification USGS Profession Paper Series Professional Paper 366 doi 10 3133 pp366 Vincent 2000 pp 27 28 De Ros L F S Morad and I S Al Aasm 1997 Diagenesis of siliciclastic and volcaniclastic sediments in the Cretaceous and Miocene sequences of the NWAfrican margin DSDP Leg 47A Site 397 Sedimentary Geology v 112 no 1 2 p 137 156 Olavsd ottir J M S Andersen and L O Boldreel 2015 Reservoir quality of intrabasalt volcaniclastic units onshore Faroe Islands North Atlantic Igneous Province northeast Atlantic AAPG Bulletin v 99 no 3 p 467 497 Vincent 2000 pp 17 19 Vincent 2000 p 22 a b c Schmidt R 1981 Descriptive nomenclature and classification of pyroclastic deposits and fragments recommendations of the IUGS Subcommission on the Systematics of Igneous Rocks Geology 9 41 43 doi 10 1007 BF01822152 S2CID 128375559 Retrieved 27 September 2020 Schmincke Hans Ulrich 2003 Volcanism Berlin Springer p 130 ISBN 9783540436508 Vincent 2000 p 19 Fisher and Schminke 1984 p 90 Fisher and Schminke 1984 pp 89 90 Schmincke Hans Ulrich 2003 Volcanism Berlin Springer pp 137 138 ISBN 9783540436508 Kautz P F Ingersoll R V Baldridge W S Damon P E Shafiqullah M December 1981 Geology of the Espinaso Formation Oligocene North Central New Mexico GSA Bulletin 92 12 Part II 2318 2400 Bibcode 1981GSAB 92 2318K doi 10 1130 GSAB P2 92 2318 Smedes H W Prostka H J 1972 Stratigraphic framework of the Absaroka Volcanic Supergroup in the Yellowstone National Park region U S Geological Survey Professional Paper Professional Paper 729 C C 19 doi 10 3133 pp729C nbsp Wikimedia Commons has media related to Volcaniclastic rocks Retrieved from https en wikipedia org w index php 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