Base surge deposits, eruption history, and depositional processes of a wet phreatomagmatic volcano in Central Anatolia (Cora Maar)

Gençalioğlu-Kuşcu, Gonca; Atilla, Cüneyt; Fernand, Raymond Alexander; Kuşcu, İ̇lkay

doi:10.1016/j.jvolgeores.2006.06.013

Cited by 42 publications

(30 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Layer L 11 has, as L 1 , a series of paralleled thinly stratified and alternating medium and fine grain-supported beds, with single beds being well-defined, laterally continuous and presenting no traction at their surface, also suggesting deposition from a surge. However, in contrast to L 1 in which the deposition was under dry conditions, the presence of accretionary lapilli, mud-cracks and impact sags in L 11 typically suggest that it was deposited under wet conditions [19,43], probably by gentle settlement of particles from steam-rich phreatomagmatic eruption columns [15,18], or from convecting pyroclastic surge clouds in which there was abundant moisture and/or continuous vapour condensation [11].…”

Section: Unit 3 (U 3 )mentioning

confidence: 96%

“…The abundance of lithic fragments, their angular morphology and the relatively low degree of vesicularity of the juvenile clasts in the upper part (L 2 ) suggest that the fragmentation process was dominated by phreatomagmatic activity. Moreover, the importance of lithic clasts indicates significant quarrying of the vent zone [43,45,46] due to an energetic phreatomagmatic explosion. The style of phreatomagmatic fragmentation and the resulting eruption can be highly influenced by the host rock environment (e.g., hard or soft rock) through which the magma must penetrate [5,47,48].…”

Section: Eruptive History Of the Bmmmentioning

confidence: 99%

See 1 more Smart Citation

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

et al. 2013

View full text Add to dashboard Cite

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.

show abstract

Section: Unit 3 (U 3 )mentioning

confidence: 96%

Section: Eruptive History Of the Bmmmentioning

confidence: 99%

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

et al. 2013

View full text Add to dashboard Cite

show abstract

“…Those correspond to what is often described or interpreted as so-called "chute-and-pools", a term that implies deposition dominated by a Froude-jump (a jump in flow Froude-regine, like a hydraulic jump), and thus intrinsically contains a non-proven interpretation (see e.g. Schmincke et al 1973, Gençalioğlu-Kuşcu et al 2007. Interestingly, the erosive-based backsets are visible at multiple scales with invariant morphology, and span over two orders of magnitude with trough-to-crest heights ranging from less than 5 cm (Fig 5c) to >1 m (Fig 5a).…”

Section: Erosive-based Backsetsmentioning

confidence: 98%

“…a jump of the Froude regime from supercritical to subcritical) in some basal layer of the flow (e.g. Schmincke et al 1973, Gençalioğlu-Kuşcu et al 2007. Recently, most characteristics of such stoss-side truncations, in particular their abrupt and steep termination, could be reproduced using experimental short-lived air bursts unrelated to a jump in flow regime (Douillet et al 2017).…”

Section: Erosional Structures From Turbulent Pyroclastic Currentsmentioning

confidence: 99%

Pyroclastic dune bedforms: macroscale structures and lateral variations. Examples from the 2006 pyroclastic currents at Tungurahua (Ecuador)

Douillet¹,

Bernard²,

Bouysson³

et al. 2018

Preprint

View full text Add to dashboard Cite

Pyroclastic currents are catastrophic flows of gas and particles triggered by explosive volcanic eruptions. For much of their dynamics, they behave as particulate density currents and share similarities with turbidity currents. Pyroclastic currents occasionally deposit dune bedforms with peculiar lamination patterns, from what is thought to represent the dilute low concentration and fluid-turbulence supported end member of the pyroclastic currents. This article presents a high resolution dataset of sediment plates (lacquer peels) with several closely spaced lateral profiles representing sections through single pyroclastic bedforms from the August 2006 eruption of Tungurahua (Ecuador). Most of the sedimentary features contain backset bedding and preferential stoss-face deposition. From the ripple scale (a few centimetres) to the largest dune bedform scale (several metres in length), similar patterns of erosive-based backset beds are evidenced. Recurrent trains of sub- vertical truncations on the stoss side of structures reshape and steepen the bedforms. In contrast, sporadic coarse-grained lenses and lensoidal layers flatten bedforms by filling troughs. The coarsest (clasts up to 10 cm), least sorted and massive structures still exhibit lineation patterns that follow the general backset bedding trend. The stratal architecture exhibits strong lateral variations within tens of centimetres, with very local truncations both in flow-perpendicular and flow-parallel directions. This study infers that the sedimentary patterns of bedforms result from four formation mechanisms: (i) differential draping; (ii) slope-influenced saltation; (iii) truncative bursts; and (iv) granular-based events. Whereas most of the literature makes a straightforward link between backset bedding and Froude-supercritical flows, this interpretation is reconsidered here. Indeed, features that would be diagnostic of subcritical dunes, antidunes and ‘chute and pools’ can be found on the same horizon and in a single bedform, only laterally separated by short distances (tens of centimetres). These data stress the influence of the pulsating and highly turbulent nature of the currents and the possible role of coherent flow structures such as Görtler vortices. Backset bedding is interpreted here as a consequence of a very high sedimentation environment of weak and waning currents that interact with the pre-existing morphology. Quantification of near-bed flow velocities is made via comparison with wind tunnel experiments. It is estimated that shear velocities of ca 0.30 m.s-1 (equivalent to pure wind velocity of 6 to 8 m.s-1 at 10 cm above the bed) could emplace the constructive bedsets, whereas the truncative phases would result from bursts with impacting wind velocities of at least 30 to 40 m.s-1.

show abstract

“…Maar crater shapes can also be strongly controlled by the presence of any pre-volcanic lithological situations, including older cones that might have been dissected by the maar-forming eruption, or when explosions occur in a preexisting crater form by previous activity (e.g., [128]). The initial shape of the crater might even change with time due to erosion and slumping of the walls and tephra ring (e.g., [18,79,[129][130][131]), shallowing the crater slope and reducing the relief. Older maar basins, for example, could have strong erosion modification along their margins and also could be filled with post-eruptive debris, enlarging the original size of the crater.…”

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

View full text Add to dashboard Cite

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.

show abstract

Base surge deposits, eruption history, and depositional processes of a wet phreatomagmatic volcano in Central Anatolia (Cora Maar)

Cited by 42 publications

References 23 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

Pyroclastic dune bedforms: macroscale structures and lateral variations. Examples from the 2006 pyroclastic currents at Tungurahua (Ecuador)

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

Contact Info

Product

Resources

About