Cretaceous basaltic phreatomagmatic volcanism in West Texas: Maar complex at Peña Mountain, Big Bend National Park

Befus, Kenneth S.; Hanson, Richard E.; Lehman, Thomas M.; Griffin, William R.

doi:10.1016/j.jvolgeores.2008.01.021

Cited by 41 publications

(30 citation statements)

References 57 publications

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“…Moreover, due to the lateral continuity of the bed series, their good sorting and the low bedding inclination, L 1 may correspond to deposition from a surge that was probably segregated into different eddies or organised into a turbulent and high-concentration head followed by a lower concentrated tail [10]. Similar stratification was identified in the basaltic phreatomagmatic deposit of the Peńa Mountain (West Texas) and also ascribed to deposition from high-concentration deflating base surges, in which rapid suspension sedimentation prevented tractional reworking of particles [42]. However, the presence of unconsolidated and consolidated beds indicates that L 1 is a succession of dry fall deposits (Fig.…”

Section: Unit 1 (U 1 )mentioning

confidence: 70%

Eruptive history of the Barombi Mbo Maar, Cameroon Volcanic Line, Central Africa: Constraints from volcanic facies analysis

et al. 2013

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his study presents the first and detail field investigations of exposed deposits at proximal sections of the Barombi Mbo Maar (BMM), NE Mt Cameroon, with the aim of documenting its past activity, providing insight on the stratigraphic distribution, depositional process, and evolution of the eruptive sequences during its formation. Field evidence reveals that the BMM deposit is about 126m thick, of which about 20m is buried lowermost under the lake level and covered by vegetation. Based on variation in pyroclastic facies within the deposit, it can be divided into three main stratigraphic units: U 1 , U 2 and U 3 . Interpretation of these features indicates that U 1 consists of alternating lapilli-ash-lapilli beds series, in which fallout derived individual lapilli-rich beds are demarcated by surges deposits made up of thin, fine-grained and consolidated ash-beds that are well-defined, well-sorted and laterally continuous in outcrop scale. U 2 , a pyroclastic fall-derived unit, shows crudely lenticular stratified scoriaceous layers, in which many fluidal and spindle bombs-rich lapilli-beds are separated by very thin, coarse-vesiculatedash-beds, overlain by a mantle xenolith-and accidental lithic-rich explosive breccia, and massive lapilli tuff and lapillistone. U 3 displays a series of surges and pyroclastic fall layers. Emplacement processes were largely controlled by fallout deposition and turbulent diluted pyroclastic density currents under "dry" and "wet" conditions. The eruptive activity evolved in a series of initial phreatic eruptions, which gradually became phreatomagmatic, followed by a phreato-Strombolian and a violent phreatomagmatic fragmentation. A relatively long-time break, demonstrated by a paleosol between U 2 and U 3 , would have permitted the feeding of the root zone or the prominent crater by the water that sustained the next eruptive episode, dominated by subsequent phreatomagmatic eruptions. These preliminary results require complementary studies, such as geochemistry, for a better understanding of the changes in the eruptive styles, and to develop more constraints on the maar's polygenetic origin.

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Section: Unit 1 (U 1 )mentioning

confidence: 70%

Eruptive history of the Barombi Mbo Maar, Cameroon Volcanic Line, Central Africa: Constraints from volcanic facies analysis

et al. 2013

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“…Unlike pheatomagmatic deposits which are formed as a result of rising magma-ground water interaction (e.g., Ngwa et al, 2010, Befus et al, 2008, the Batoke pyroclastic deposit resulted from magma-surface water interaction. The presence of the lava flow flanked by the pyroclastic deposit (Fig.…”

Section: Discussionmentioning

confidence: 98%

“…Thus, we conclude that due to the lack of the above mentioned depositional features, the presence of impact sags under bombs is rather an indication of deformation during fall. Studies elsewhere (e.g., Befus et al, 2008) have shown that the presence of impact sags in phreatomagmatic deposit is typical evidence of direct fallout from eruption columns during pulsatory phreatomagmatic eruptions. Impact sags are also indicative of the plastic deformation of beds underneath the blocks (Lorenz, 1985) as well as the energy of ejection.…”

Section: Discussionmentioning

confidence: 99%

Physical Volcanology of Pyroclastic Tephra Deposit at Batoke Mt. Cameroon, West Africa: An Over View.

Ngwa¹,

Nche²,

Suh³

2013

Glo Jnl Geo Sci

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In this contribution, we report an overview of the physical attributes of pyroclastic deposit at the foot of Mt. Cameroon, West Africa. In the deposit three facies types; which are the lava flow, the lapilli and ash are common. The ash is the dominant facies and occurs irregularly in alternation with the lapilli. The most common types of depositional features include cm-dm planar beds and impact sags. We infer from field observations of facies types, clasts types and depositional features that this deposit is a phreatomagmatic fall deposit which resulted from an interaction between lava flow and surface water. The occurrence in the deposit of accretionary lapilli, impact sags, fragments of country-rock and juvenile clasts is ambiguous evidence in support of phreatomagmatic activity. The presence of a lava flow flanked by the tephra pile, the lack of accidental clasts, and the scarcity of bombs are evidence in support of a surface water-lava flow interaction.

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“…Nevertheless, the consequence of the poly-activity within small volcanoes is the construction of complex stratigraphic sequences. These complex volcanoes usually display packages or depositional units made of erupted materials that in some cases can be directly apparent on the field by deposit textural differences, chaotic deposits separated by a lava flow horizon (e.g., [97]), and/or a dike cutting through the deposit units (e.g., [98]). Textural differences in pyroclastic sequences can also show altered or palagonized juvenile-rich deposits that underlie a fresh surge or fall unit within the same eruptive sequence (e.g., [33,97,99]) or the presence of centimeter-to decimeter-thick light brown to yellowish pedogenized ash horizons in some deposits [21].…”

Section: Features Of Complex Maar Volcanoesmentioning

confidence: 99%

“…These complex volcanoes usually display packages or depositional units made of erupted materials that in some cases can be directly apparent on the field by deposit textural differences, chaotic deposits separated by a lava flow horizon (e.g., [97]), and/or a dike cutting through the deposit units (e.g., [98]). Textural differences in pyroclastic sequences can also show altered or palagonized juvenile-rich deposits that underlie a fresh surge or fall unit within the same eruptive sequence (e.g., [33,97,99]) or the presence of centimeter-to decimeter-thick light brown to yellowish pedogenized ash horizons in some deposits [21]. Well-marked structural discordant contacts or truncation surface or erosional limits between the deposit packages (e.g., [26,34,66,76,92,100]) are some of the main features observed within the stratigraphic sequence.…”

Section: Features Of Complex Maar Volcanoesmentioning

confidence: 99%

How Polygenetic are Monogenetic Volcanoes: Case Studies of Some Complex Maar‐Diatreme Volcanoes

Tchamabé¹,

Keresztúri²,

Németh³

et al. 2016

Updates in Volcanology - From Volcano Modelling to Volcano Geology

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The increasing number of field investigations and various controlled benchtop and largescale experiments have permitted the evaluation of a large number of processes involved in the formation of maar-diatreme volcanoes, the second most common type of smallvolume subaerial volcanoes on Earth. A maar-diatreme volcano is recognized by a volcanic crater that is cut into country rocks and surrounded by a low-height ejecta rim composed of pyroclastic deposits of few meters to up to 200 m thick above the syn-eruptive surface level. The craters vary from 0.1 km to up to 5 km wide and vary in depth from a few dozen meters to up to 300 m deep. Their irregular morphology reflects the simple or complex volcanic and cratering processes involved in their formation. The simplicity or complexity of the crater or the entire maar itself is usually observed in the stratigraphy of the surrounding ejecta rings. The latter are composed of sequences of successive alternating and contrastingly bedded phreatomagmatic-derived dilute pyroclastic density currents (PDC) and fallout depositions, with occasional interbedded Strombolian-derived spatter materials or scoria fall units, exemplifying the changes in the eruptive styles during the formation of the volcano. The entire stratigraphic sequence might be preserved as a single eruptive package (small or very thick) in which there is no stratigraphic gap or significant discordance indicative of a potential break during the eruption. A maar with a single eruptive deposit is quantified as monogenetic maar, meaning that it was formed by a single eruptive vent from which only a small and ephemeral magma erupted over a short period of time. The stratigraphy may also display several packages of deposits separated either by contrasting discordance surfaces or paleosoils, which reflect multiple phases or episodes of eruptions within the same maar. Such maars are characterized as complex polycyclic maars if the length of time between the eruptive events is relatively short (days to years). For greater length of time (thousands to millions of years), the complex maar will be quantified as polygenetic. These common depositional breaks interpreted as signs of temporal interruption of the eruptions for various timescales also indicate deep magma system processes; hence magmas of different types might erupt during the formation of both simple and complex maars. The feeding dikes can interact with groundwater and form closely distributed small craters. The latter can coalesce to form a final crater with various shapes depending on the distance between them. This observation indicates the significant role of the magmatic plumbing system on the formation and growth of complex and polygenetic maar-diatreme volcanoes.

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Cretaceous basaltic phreatomagmatic volcanism in West Texas: Maar complex at Peña Mountain, Big Bend National Park

Cited by 41 publications

References 57 publications

Eruptive history of the Barombi Mbo Maar, Cameroon Volcanic Line, Central Africa: Constraints from volcanic facies analysis

Eruptive history of the Barombi Mbo Maar, Cameroon Volcanic Line, Central Africa: Constraints from volcanic facies analysis

Physical Volcanology of Pyroclastic Tephra Deposit at Batoke Mt. Cameroon, West Africa: An Over View.

How Polygenetic are Monogenetic Volcanoes: Case Studies of Some Complex Maar‐Diatreme Volcanoes

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