Extensive soft-sediment deformation and peperite formation at the base of a rhyolite lava: Owyhee Mountains, SW Idaho, USA
23
Citation
53
Reference
10
Related Paper
Citation Trend
Keywords:
Lava dome
Breccia
Caldera
Breccia
Pumice
Debris flow
Cite
Citations (50)
Pyroclastic material of a rhyolite type is present in some thin layers in the upper part of the De Geerdalen Formation in the Sassenfjorden area. This is the first evidence of late Triassic (Norian.Rhaetian) volcanic activity in Svalbard.
Cite
Citations (3)
Caldera
Bonito
Cite
Citations (2)
Southren Kyushu has been the region of intense volcanism at least since Pliocene time. One of the most characteristic features is the prevalence of the large-scale pyroclastic flow eruptions which originated from such gigantic calderas as Aira, Ata, Kikai and Kakuto.There exist a considerable number of literature on the stratigraphic sequence and distributions of the pyroclastic flow deposits in South Kyushu. However, relatively small number of reports are available on air-fall tephra deposits, which are useful for establishing Quaternary chronology both of source volcanoes and of marine or fluvial sediments in the coastal regions such as the Miyazaki Plain. In this study, each bed of maker-tephras which erupted during the time from ca. 100, 000 to 25, 000y.B.P., is precisely discriminated and described in the northern part of the Osumi Peninsula, Kagoshima Prefecture first. And then each tephra is traced northeastward along the main axis of distributions to the Miyazaki Plain.Of many tephras, the following four well-dated tephras are used as fundamental timemakers because of their widespread occurence; Ata pyroclastic flows, originated from Ata caldera in 95, 000-90, 000y.B.P. ; Kikai-Tozurahara ash falls, originated from Kikai caldera in 75, 000y.B.P. ; Aso-4 pyroclastic flows, originated from Aso caldera in 70, 000y.B.P.; Ito pyroclastic flows and AT ash, originated from Aira caldera in 22, 000-21, 000y.B.P. Several air-fall tephras from the Aira and Kirishima volcanic centers are identified in detail and roughly dated from their stratigraphic positions between these fundamental maker-beds.About 75, 000-70, 000y.B.P., explosive activity of Aira caldera occurred resulting in the formation of plinian pumice fall deposit, Fukuyama pumice falls, which is found from the Osumi Peninsula to the Miyazaki Plain. During ca. 60, 000-25, 000y.B.P., intermittent eruptions occurred forming five sheets of tephras, of which the Iwato eruption was greatest in producing pumice falls, pyroclastic surges and pyroclastic flows. Iwato pumice falls mantle extensive area from the Osumi Peninsula to the Miyazaki Plain. Cataclysmic eruption occurred from Aira caldera, producing Osumi pumice falls, Tsurnaya and Ito pyroclastic flows and AT ash 22, 000-21, 000y.B.P. Most of these eruptions were accompanied with phreatomagmatic ones.Eruptive history of Kirishima volcano is divided into two stages deduced from the tephra sequence. At ca. 40, 000 y.B.P., older stage of activity started with ejection of relatively felsic pumice falls, Iwaokoshi pumice fall, and graded to more mafic and frequent eruptions, Awaokoshi scoria fall. Younger stage began with the plinian eruption of Kobayashi pumice fall at ca. 15, 000y.B.P.Of many terraces in Miyazaki Plain, Sanzaibaru terrace is the most extensive one and is accompanied with transgressive marine deposits. Stratigraphic relation with tephra sequence shows that Sanzaibaru terrace was emerged before the Ata pyroclastic flow eruption, ca. 95, 000y.B.P., probably indicating the Last Interglacial Stage. Most of terraces younger than Sanzaibaru are of fluvial origin, except for Nyutabaru II and probably III terraces which are partly of marine origin, and are largely devided into two groups, older and younger. Older terraces, Nyutabaru terrace group, formed during the time from the Ata eruption to the Aso-4 eruption, were chracterized by the profiles with more gentle gradient. Younger ones which were chracterized by the profiles with steeper gradient, were formed after the Aso-4 eruption and before the Kobayashi pumice fall. The difference of their profiles reflects the sea level after the maximum stage in the Last Interglacial Age.
Caldera
Pyroclastic fall
Tephrochronology
Peninsula
Cite
Citations (6)
Summary Glass-breccias and volcanic glass from Marysvale are shown to be welded ash-flow tuffs of rhyolitic composition. They are interpreted as resulting from intermittent volcanic activity.
Breccia
Volcanic glass
Volcanic ash
Cite
Citations (2)
Caldera
Pyroclastic fall
Volcanic hazards
Volcanology
Cite
Citations (43)
Voluminous silicic volcanism of the Mahogany Mountain--Three Fingers rhyolite field (MM--TFrf) is spatially and temporally associated with mid-Miocene flood basalts of the Columbia River Basalt province. Early studies of the area advocated for a two-caldera model consisting of the Mahogany Mountain and the slightly younger Three Fingers caldera with pre- and post-caldera effusive rhyolite eruptions. Although close in time, the calderas were thought to be spatially offset producing the tuff of Leslie Gulch and the tuff of Spring Creek. Finding that the tuff of Spring Creek, that is exposed in Leslie Gulch, is an altered product of the tuff of Leslie Gulch, Benson & Mahood (2016) suggested only one large caldera with pre- to post-caldera lavas. With the new data of my study, building on results by Marcy (2013), we can address key outstanding questions regarding the stratigraphic and geochemical evolution of mid-Miocene rhyolite volcanism at the MM--TFrf. Abundant and compositionally variable effusive rhyolites largely postdate the tuff of Leslie Gulch, including the Mahogany Mountain as well as the McIntyre Ridge rhyolite that were considered pre-caldera before. New ages of the Mahogany Mountain rhyolite suite (15.82-15.71 Ma) and stratigraphic, mineral & compositional data, and age relationships along Succor Creek indicate both rhyolites are post-caldera. The only rhyolite underlying the tuff of Leslie Gulch was identified in the Leslie Gulch locality itself, yielding an age of 16.02 Ma. Stratigraphic data reveal that the tuff of Leslie Gulch is a complex, multi-phase deposit with eruptive breaks in between. There are additional discrete explosive events with deposits along Succor Creek and north of Leslie Gulch that are distinguished by age or composition. Similarly, geochronological and compositional data can be used to identify distinct post-caldera rhyolite magmas. In summary, the MM--TFrf represents a prolific rhyolite center that was active from 16.02 to 15.71 Ma thus shifting initiation of rhyolite activity back, to the end of Grande Ronde Basalt volcanism. Rhyolite eruptions recommenced in the SW of the field with the eruption of the 14.94 Ma Birch Creek rhyolite, and 14.42 Ma McCain Creek rhyolite.
Caldera
Silicic
Cite
Citations (0)
ABSTRACT Black mudstones in marine volcaniclastic environments have been interpreted both as non‐volcanic ‘background’sedimentation and as fine grained vitric dust from the waning stages of primary volcanism. Although difficult to distinguish by standard petrographic techniques, differentiation between the two is crucial when attempting to determine sedimentation rates or to infer periods of volcanic quiescence. In the Ordovician Lower Rhyolitic Tuff Formation of North Wales such a fine grained black unit at Cwm Idwal is geochemically similar to an underlying rhyolite ash flow tuff. Its chemical index of alteration (CIA) is identical to that of the tuff. These data suggest that the black mudstone unit is a vitric tuff related to the underlying ash flow tuff. Use of a CIA in addition to trace element geochemistry should, in most cases, serve to distinguish tuffs from silicified mudstones.
Volcanic ash
Sedimentation
Cite
Citations (12)
This chapter contains sections titled: Introduction Precaldera Events The Osumi Pumice Fall Tsumaya Pyroclastic Flow Kamewarizaka Breccia Ito Pyroclastic Flow Nature of the Magma Formation of the Aira Caldera Post-Aira Caldera Activity Funnel-Shaped Underground Structure of the Aira Caldera and Other Japanese Calderas Conclusion
Caldera
Pumice
Breccia
Cite
Citations (2)
Abstract The widespread shower-bedded deposits of Rotoehu Ash consist of multiple airfall pyroclastic units (tephras) which underlie, are interbedded within and mantle the less widespread rhyolitic pyroclastic flow deposits of the Rotoiti Breccia Formation (late Pleistocene). No significant time intervals are recorded within the Rotoehu Ash, showing that the thick pyroclastic flow breccia deposits enclosed by the Rotoehu Ash units were also erupted in a short time interval. Recognition of the multiple nature of Rotoehu Ash has proved necessary in correlation of breccia deposits in the Rotorua area.
Breccia
Pyroclastic fall
Volcanic ash
Cite
Citations (46)