No full-text available
To read the full-text of this research,
you can request a copy directly from the author.
Mio/Pliocene phreatomagmatic volcanism in the Western Pannonian Basin
Abstract
Published 3.6. Fisica del vulcanismo
... Ma (Balogh et al., 1986;Wijbrans et al., 2007), than the cones which have been analysed by morphometrically elsewhere (Wood, 1980b). At least ten scoria cone remnants, with an addition of two deeply eroded cones (Tihany and Kab-hegy) and a further two covered by thick Quaternary sediments have been recognised at BBHVF through detailed investigations over the past decade (Martin and Németh, 2004;Auer et al., 2007). Of these fourteen scoria cones, this study deals with the morphometry of seven selected locations (Fig. 2), which have identifiable/visible geologically well-defined boundaries and available, reliable K-Ar and/or Ar-Ar ages. ...
... 3A-B), interbedded coherent lava units (Fig. 3C), and various types of scoriaceous lapilli-dominated cone-building pyroclastic successions ( Fig. 3D-F). These types of deposits are typical of Strombolian-style explosive eruptions, Hawaiian-style lava fountaining and lava effusion (Martin and Németh, 2004). The majority of these processes have been inferred to take place during the cone-building eruptive phases, except for post-eruption mass-movement, and are together responsible for the complex cone-building events. ...
... Measured (Martin and Németh, 2004) resulting in the accumulation of ≤0.365 km 3 lava (Table 2). Explosive volcanic activity of Agár-tető is characterised by Strombolian-and Hawaiian-styles that produced scoriaceous fall beds interbedded with agglutinated lava spatter (Martin and Németh, 2004;Csillag et al., 2008). ...
Conference title - 7th international conference on Geomorphology, Copyright - GeoRef, Copyright 2012, American Geosciences Institute., Date revised - 2010-01-01, Language of summary - English, Pages - Abstract no. 54, ProQuest ID - 742922477, SubjectsTermNotLitGenreText - Agar-teto; Bakony Mountains; Bakony-Balaton Highland volcanic field; Balaton region; Bondoro; Carpathian Basin; Cenozoic; Central Europe; complexes; erosion; Europe; geomorphology; Hungary; igneous rocks; Kopasz-hegy; lapilli; Miocene; Neogene; Pliocene; pyroclastics; scoria; shield volcanoes; slopes; Tertiary; volcanic features; volcanic fields; volcanic rocks; volcanoes; volume, Last updated - 2012-06-07, CODEN - #05080, Corporate institution author - Kereszturi, G; Nemeth, K; Anonymous, DOI - 2010-065642; #05080
... As the syn-volcanic palaeosurface was higher than it is today, currently visible edifices correspond to both former intrusive bodies as well as preserved maars, scoria cones and lava fields (Martin and Németh 2004). Only the largest lava bodies were big enough to resist erosion and maintain a well-preserved edifice (Martin and Németh 2004). ...
... As the syn-volcanic palaeosurface was higher than it is today, currently visible edifices correspond to both former intrusive bodies as well as preserved maars, scoria cones and lava fields (Martin and Németh 2004). Only the largest lava bodies were big enough to resist erosion and maintain a well-preserved edifice (Martin and Németh 2004). Visited sites are described in the following: ...
Columnar Jointing (CJ) is commonly observed in slowly cooling lava
bodies. The characteristic diameter of the columns is thought to depend
on the cooling rate, faster (respectively slower) cooling resulting in
larger (smaller) thermo-elastic strain yielding more slender (stout)
columns. One of the goals of our CJ project is to analyse whether the
characteristic diameter of the columns is also dependent on other
factors, such as the chemical composition of the lava and the setting of
the cooling lava body. While the laboratory measurements are finished
and the bibliography compiled, we present our field measurements
including photos, methods and first results. In order to compare
different CJ sites, we develop a procedure to quantitatively
characterize the columns. On the field, we collect photos with a well
visible scale, either perpendicular or parallel to the columns. Then we
use a self-developed, interactive software that processes the photos and
performs statistical analyses on the average length of a side (L), on
the average cross-sectional area (A), and on the number of sides of
columns (N). Using these values, the parabolic relation between A and L2
is determined as a function of N, and compared to ideal polygons. Data
from 25 sites across Europe show that the observed areas are smaller
than those of the ideal polygons by about 7%. To be able to use photos
taken from the side, we calculate the ratios of the distance to the 2nd
and 3rd vertices to L, again as a function of N. The averages of these
ratios are as those of ideal polygons, but their standard deviations
suggest that the geometry of individual column cross-sections is
anisotropic in a random direction. This explanation also underlines the
previous result of smaller areas compared to ideal, and suggests that
for a given area, the total length of joints is not fully minimized.
This is in line with earlier and also present observations that the
average number of sides at any CJ site is less than 6. Preliminary
results show that CJ sizes are not directly dependent on chemical
composition. The range of L at most sites varies between 8±3 cm
to 50±15 cm, although we observed a few sites with column sizes
in the order of 1-3 m. The major element composition measurements on
rock samples from site where this information was previously not
available will help to conclude on this question. Composition, however,
may play an important role in an indirect way on the size of CJ. Our
field observations show that CJ occurs in different geological settings
(lava flow, lava lakes, necks and dykes), and that these might strongly
influence the size of CJs by defining the boundary conditions of the
cooling lava body. Compilation of our observations and further reading
on visited CJ site geology will allow concluding on this question.
... In Western Hungary, two distinct monogenetic volcanic fields are recognized as Bakony-Balaton Highland and Little Hungarian Plain Volcanic Fields [65,66] (Figure 2). Both fields display a typical landscape formed by numerous eroded monogenetic volcanoes. ...
Geoheritage is an important aspect in developing workable strategies for natural hazard resilience. This is reflected in the UNESCO IGCP Project (# 692. Geoheritage for Geohazard Resilience) that continues to successfully develop global awareness of the multifaced aspects of geoheritage research. Geohazards form a great variety of natural phenomena that should be properly identified, and their importance communicated to all levels of society. This is especially the case in urban areas such as Auckland. The largest socio-economic urban center in New Zealand, Auckland faces potential volcanic hazards as it sits on an active Quaternary monogenetic volcanic field. Individual volcanic geosites of young eruptive products are considered to form the foundation of community outreach demonstrating causes and consequences of volcanism associated volcanism. However, in recent decades, rapid urban development has increased demand for raw materials and encroached on natural sites which would be ideal for such outreach. The dramatic loss of volcanic geoheritage of Auckland is alarming. Here we demonstrate that abandoned quarry sites (e.g., Wiri Mountain) could be used as key locations to serve these goals. We contrast the reality that Auckland sites are underutilized and fast diminishing, with positive examples known from similar but older volcanic regions, such as the Mio/Pliocene Bakony–Balaton UNESCO Global Geopark in Hungary.
... The Mesozoic carbonate blocks of the Keszthely Hills are surrounded by Miocene sediments and Pliocene basalt volcanoes, maars, and diatremes (Budai et al., 1999;Martin and Németh, 2004). To the north and east, boreholes revealed marine sedimentation during part of the middle Miocene, when two connected grabens, the Tapolca and Várvölgy grabens developed (Fig. 11). ...
The formation and deformation history of back-arc basins play a critical role in understanding the tectonics of plate interactions. Furthermore, opening of extensional back-arc basins during the overall convergence between Africa and Europe is a fundamental process in the overall tectonic evolution of the Mediterranean and adjacent areas. In this frame, Miocene tectonic evolution of the western Pannonian Basin of Central Europe and its connection to inherited Cretaceous structures of the Eastern Alpine nappes are presented.
Revision of published and addition of new structural and thermochronological data, as well as seismic profiles from the western Pannonian Basin is complemented by high-resolution thermo-mechanical numerical modeling in order to propose a new physically consistent tectono-sedimentary model for the basin evolution. The onset of extension is dated as ~25–23 Ma, and higher rates are inferred between 19 and 15 Ma at the south-western part of the area (Pohorje, Kozjak Domes, Murska Sobota Ridge, and Mura-Zala Basin). Rift initiation involved the exhumation of the middle part of the Austroalpine nappe pile along low-angle detachment faults and mylonite zones. The Miocene low-angle shear zones could reactivate major Cretaceous thrust boundaries, the exhumation channel of ultra-high-pressure rocks of the Pohorje Dome, or Late Cretaceous extensional structures. Miocene extension was associated with granodiorite and dacite intrusions between 18.64 and 15 Ma. The Pohorje pluton intruded at variable depth from ~4 to 16–18 km and experienced ductile stretching, westward tilting, and asymmetric exhumation of its eastern side. Terrestrial early Miocene (Ottnangian to Karpatian, 19–17.25 Ma) syn-rift depositional environment in supradetachment basins evolved to near-shore and bathyal one by the middle Miocene (Badenian, 15.97–12.8 Ma). Deformation subsequently migrated eastwards to the western part of the Transdanubian Range (Keszthely Hills) and to newly formed grabens. In this formerly emerged terrestrial area active faulting started at 15–14.5 Ma and continued through the late Miocene almost continuously up to ~8 Ma but basically terminated in the Mura-Zala Basin by ~15 Ma (early Badenian). These observations suggest a ~200 km shift of active faulting, basin formation, and related syn-tectonic sedimentation from the SW (Pohorje and Mura-Zala Basin) toward the Pannonian Basin center. Building on the above described observational and modeling data makes the Pannonian Basin an ideal natural laboratory for understanding the coupling between deep Earth and surface processes.
... Ma(Ruszkiczay- Rüdiger et al., 2011, Fig 1A, site 3). In this region basalt volcanism preserved past surface positions and landforms(Martin and Németh, 2004;Csillag, 2004) enabling the estimation of ~50 m/Ma for cumulative surface denudation rate for the last ~3-4 Ma period (Ruszkiczay-Rüdiger et al., 2011). Further to the west, the combined CRN and luminescence age determination of Danube terraces in the Vienna Basin suggest differential incision rates of ~81 m/Ma and 23 m/Ma during the last 340 ka and 250 ka, respectively (Braumann et al., 2019). ...
The cumulative incision rates of ~50–70 m/Ma integrating over the last ~3 Ma have been derived from published terrace-chronological data of the Danube river in the Western Pannonian Basin. An apparent acceleration of uplift rates was observed for shorter timescales culminating at ~200 m/Ma over the last ~140 ka. An examination of the change of the incision rates through time revealed that the incision rate was fairly constant at ~50 m/Ma from ~3 Ma to ~140 ka, and the faster rates are valid only for the last ~140 ka. These findings suggest that the long-term uplift rate of the northwestern limb of the Transdanubian Range is ~50 m/Ma, and the apparent acceleration of river incision during the Late Pleistocene is considered as the result of faster, most probably climate-driven incision during the last glacial cycle, outpacing the long-term uplift rate. The observed upper crustal neotectonic faults are not sufficient to accommodate the deformation necessary for the reported Pliocene to Quaternary vertical motion. The geodynamic model for the explanation of the magnitude and pattern of surface uplift in the western Pannonian Basin involves a complex interplay between (1) deep lithosphere-asthenosphere dynamics, (2) structural inversion governed by the northward drift of Adria, (3) inherited geological structures and (4) climate driven surface processes (denudation and sediment loading).
... Due to the different typesof volcanic activities and the degree of erosion of the volcanic formations, the remnants of the basalt volcanoes are made up of rocks from diverse depositional environments. The most typical eruption type was maar-volcanism (MARTIN, NÉMETH 2004). The craters thus formed were mostly filled with lava flows and lava lakes. ...
... Previous volcanological studies also argued that the alkaline basaltic activity was mainly tectonically controlled because both the magma flux and output rate were low (Kereszturi et al., 2010). Martin and Németh (2004) also proposed that the tectonic inversion in the CPR might have played a role in the formation of alkaline basalts of the BBHVF as well. ...
We present a new model for the formation of Plio-Pleistocene alkaline basalts in the central part of the Carpathian-Pannonian region (CPR). Based on the structural hydroxyl content of clinopyroxene megacrysts, the 'water' content of their host basalts is 2.0-2.5 wt.%, typical for island arc basalts. Likewise, the source region of the host basalts is 'water' rich (290-660 ppm), akin to the source of ocean island basalts. This high 'water' content could be the result of several subduction events from the Mesozoic onwards (e.g. Penninic, Vardar and Magura oceans), which have transported significant amounts of water back to the upper mantle, or hydrous plumes originating from the subduction graveyard beneath the Pannonian Basin. The asthenosphere with such a relatively high 'water' content beneath the CPR may have been above the 'pargasite dehydration' (< 90 km) or the 'nominally anhydrous' (> 90 km) solidi. This means that neither decompressional melting nor the presence of voluminous pyroxenite and eclogite lithologies are required to explain partial melting. While basaltic partial melts have been present in the asthenosphere for a long time, they were not extracted during the syn-rift phase, but were only emplaced at the onset of the subsequent tectonic inversion stage at ~8-5 Ma. We propose that the extraction has been facilitated by evolving vertical foliation in the asthenosphere as a response to the compression between the Adriatic indenter and the stable European platform. The vertical foliation and the prevailing compression effectively squeezed the partial basaltic melts from the asthenosphere. The overlying lithosphere may have been affected by buckling in response to compression, which was probably accompanied by formation of deep faults and deformation zones. These zones formed conduits towards the surface for melts squeezed out of the asthenosphere. This implies that basaltic partial melts could be present in the asthenosphere in cases where the bulk 'water' content is relatively high (> ~200 ppm) at temperatures exceeding ~1000-1100 °C. These melts could be extracted even under a compressional tectonic regime, where the combination of vertical foliation in the asthenosphere and deep fractures and deformation zones in the folded lithosphere provides pathways towards the surface. This model is also valid for deep seated transpressional or transtensional fault zones in the lithosphere.
... Basalt volcanism in the Little Hungarian Plain and the nearby Bakony-Balaton Highland Volcanic Field involved large range of eruption styles and associated volcanic forms, from maars through lava lake-filled tuff rings and scoria cones to shield volcanoes (Harangi et al. 1994;Németh and Martin 1999;Németh et al. 2001;Martin and Németh 2004;Németh 2012). Shallow, but broad tuff ring volcanoes in LHPVF have been formed due to the phreatomagmatic explosive eruption caused by mixing between uprising hot basaltic magma and water-saturated clastic sediments in areas where thick Neogene siliciclastic units build-up shallow pre-volcanic strata (Harangi and Harangi 1995;Németh 2004, 2005). ...
Three-dimensional geophysical modelling of the early Late Miocene Pásztori volcano (ca. 11–10 Ma) and adjacent area in the Little Hungarian Plain Volcanic Field of the Danube Basin was carried out to get an insight into the most prominent intra-crustal structures here. We have used gridded gravity and magnetic data, interpreted seismic reflection sections and borehole data combined with re-evaluated geological constraints. Based on petrological analysis of core samples from available six exploration boreholes, the volcanic rocks consist of a series of alkaline trachytic and trachyandesitic volcanoclastic and effusive rocks. The measured magnetic susceptibilities of these samples are generally very low suggesting a deeper magnetic source. The age of the modelled Pásztori volcano, buried beneath a 2 km-thick Late Miocene-to-Quaternary sedimentary sequence, is 10.4 +/− 0.3 Ma belonging to the dominantly normal C5 chron. Our model includes crustal domains with different effective induced magnetizations and densities: uppermost 0.3–1.8 km thick layer of volcanoclastics underlain by a trachytic-trachyandesitic coherent and volcanoclastic rock units of a maximum 2 km thickness, with a top situated at minimal depth of 2.3 km, and a deeper magmatic pluton in a depth range of 5–15 km. The 3D model of the Danube Basin is consistent with observed high ΔZ magnetic anomalies above the volcano, while the observed Bouguer gravity anomalies correlate better with the crystalline basement depth. Our analysis contributes to deeper understanding of the crustal architecture and the evolution of the basin accompanied by alkaline intraplate volcanism.
... In well-drained areas with large volumes of near-surface and/or ground water, tuff rings and/or maar volcanoes form (Martin and N emeth, 2004). The presence of subordinate phreatomagmatic volcanoes in a volcanic field could indicate variations in hydrogeology of the volcanic field, or variations of the water saturation state of the sub-surface sediments or rock units over time (Aranda-Gomez and Luhr, 1996;Gutman, 2002). ...
... The sample locality is within the Neogene–Quaternary Bakony– Balaton Highland Volcanic Field (BBHVF), which is situated within the ALCAPA tectonic unit, north of the Middle Hungarian Zone (Fig. 1a). The studied xenoliths were collected near the village of Szigliget (Fig. 1b) in an alkaline basaltic tuff deposit related to phreatomagmatic volcanism (Martin and Németh, 2004) that was active from 4.08 to 4.53 Ma (Wijbrans et al., 2007). ...
Coexisting fluid inclusions and silicate melt inclusions, trapped as primary inclusions in clinopyroxene rims and as secondary inclusions along healed fractures in orthopyroxene, were studied in two amphibole-bearing spinel lherzolite peridotite xenoliths from the Bakony–Balaton Highland Volcanic Field (western Hungary). The composition of both Cpx-hosted and Opx-hosted inclusions suggests that they were entrapped from the same silicate melt, which was saturated in volatiles at mantle P–T conditions. Raman spectroscopy, combined with microthermometry and FTIR analyses, proved the existence of CO2, H2O and H2S in the fluid inclusions. Trace element compositions of silicate melt and fluid inclusions were determined by LA–ICP–MS, although the results of fluid inclusions are only semi-quantitative. Trace element distributions revealed significant similarities in the compositions of silicate melt and fluid inclusions, especially with respect to K, Rb, Sr, Pb, Nb, Th and U content. This confirms the same parental melt for both silicate melt and fluid inclusions and suggests that the trace element content of the CO2-rich end-member (containing some dissolved melt) resulted from high P–T immiscibility in deep lithospheric environments and is controlled by the trace element content of the parent silicate melt.
Research over decades confirms the geological values of the Papuk UNESCO Global Geopark (Croatia) as a unique place in the regional frame where several orogenic events left their traces through the formation of diverse lithologies. The important part of the geological mosaic, at least in the western part of the Geopark, is the variety of igneous (sub)volcanic rocks. Albite rhyolite at Rupnica and Trešnjevica geosites formed in the Late Cretaceous (~81 Ma), recording the geological event(s) associated with the closure of the Neotethys Ocean. At that time, acidic silicate melt rose fast from the deep crustal levels to the near surface, where cooling caused regular cracking and the development of columnar jointing. Today, these geosites attract the attention of visitors and therefore they are important landmarks that contribute to local (geo)tourism. They are also used as educational sites for both higher education and schoolchildren with Rupko's Geological School, in which the development of columnar jointing is explained popularly, further enhancing public awareness of the geodiversity and geoheritage of the Mt. Papuk area. The recently opened Geo-info Center in Voćin significantly enhances the geoheritage presentation at the Geopark.
We describe volcanic inverted relief sites around the world, making a comparative analysis of those most significant sites found from literature and our own search on imagery and global topographic maps. Over fifty significant areas of volcanic inverted relief were found. The comparative analysis is based on geoscience values defined by the main geological and landscape elements that define inverted relief. This subjective analysis is open and can be verified and extended if other significant sites emerge, thus forming the basis of a future, exhaustive global comparison of this important geomorphological feature. Inverted relief occurs when valleys transform to ridges due to differential erosion of relatively resistant valley-fill, and weaker slope lithologies. It is found in various geological settings, and it is very common in volcanic terrains, especially monogenetic volcanic fields, where most examples are inverted lava flows. Relief inversion provides a clear indication of slow geological changes and landscape evolution through erosion and can be thought of in popular terms as a geological clock. Volcanic inverted relief was recognised in the 18th - 19th centuries in the Chaîne des Puys (Auvergne, France), and used as evidence to first support plutonism by Nicolas Desmarest and then support uniformitarianism by George Poulett Scrope. We review the geological and geomorphological features of volcanic inverted relief world-wide, with an emphasis on the classical Auvergne. We explore how volcanic relief inversion chart geological changes, and their value for studying geological systems and landscape evolution. With our comparative analysis we can propose sites with the greatest geoheritage potential for representing inverted relief globally and suggest how this can be valued as geoheritage. As volcanic inverted relief is an important sub-set of all inverted relief, and is generally associated with important surface, volcanic and tectonic processes, and is often ongoing, it can be an important geoheritage component in natural sites. We suggest that it should should be present in the International Union of Geological Sciences (IUGS) Global Geosite list, can be a component of geosites in UNESCO Global Geoparks. It is also a feature for geological criteria (viii) in UNESCO World Heritage sites, where it fulfils all the requirements being both a major geomorphological feature and a fingerprint of significant geological processes in Earth evolution.
Western Saudi Arabia is the home of extensive volcanic fields with hundreds of well-preserved volcanic landforms (Camp and Roobol 1989a; Camp et al. 1991; Camp and Roobol 1992; Camp et al. 1992; Alwelaie 1994; Bosworth et al. 2005).
Tihany is a spectacular volcanic peninsula of Lake Balaton, where more than a hundred cones deposited by thermal waters rise. The calcareous and siliceous building materials overlie basaltic tuff layers of maar-type volcanism. Their formation is related to the existence of an underlying magma chamber, which heated up the surrounding karst water. Hot karst waters spouted to the surface, where the dissolved silica and carbonates precipitated and deposited. During the stage of mofetta development hot spring water accumulated in ponds where organic limestone deposited. The further heating of karst water modified the composition of spring water and, in parallel, the composition of the cones. The mofetta stage was succeeded by the fumarola stage, when siliceous minerals precipitated from spring water and added further substances to the spring cone edifices. These minerals supplanted the calcites and filled cavities and cracks.
The main objective of this study is to determine the depositional mechanisms, the environment and controlling factors producing the architecture of the Kálla Gravel, which unconformably overlies the SW rim of the Transdanubian Range. The gravel crops out in large, actively quarried and small abandoned pits near to Lesenceistvánd and Uzsabánya. Three main architectural units can be distinguished based on facies, dip of strata and surfaces of toplap, downlap and/or erosional truncation. The lowermost 4-15 m-thick unit is built up of 0.2-0.8 m thick, steep (20-30°), southward dipping beds of clastsupported gravel or sandy gravel. Pebbles commonly show a(t)b(i)-type imbrication. The facies of the middle units are the same, but their respective thicknesses vary between 1-5 m and show significantly different dip directions towards N, NE. The uppermost unit is made up of horizontally-bedded sand, pebbly sand and sandy pebble. The steeply-dipping gravelly units are interpreted as foresets of a shallow-water, Gilbert-type delta prograding - in the case of the thick, lower unit - southward, and for the middle units strangely sideward to north-east. The horizontal beds of the upper unit were deposited on the flat-lying delta-plain. These units represent different phases of delta development. The lowermost units reveal the first step of a relative lake-level rise, followed by deltaic progradation due to a high rate of sediment input. The upper unit is mainly aggradational, indicating continued lake-level rise; the latter was again balanced by sedimentation. Although many small-scale deformational structures (slumps, slides, dewatering) can be seen, these are connected to rapid deposition. Evidence of synsedimentary faulting has not been exposed so far. Therefore the reconstructed, relative lake-level changes are interpreted as an indication of basin-wide subsidence combined with climatically induced (increased humidity) water-level rise.
Alkaline basaltic volcanism has been taking place in the Carpathian–Pannonian region since 11 Ma and the last eruptions occurred only at 100–500 ka. It resulted in scattered low-magma volume volcanic fields located mostly at the margins of the Pannonian basin. Many of the basalts have compositions close to those of the primitive magmas and therefore can be used to constrain the conditions of the magma generation. Low-degree (2–3 %) melting could occur in the convective asthenosphere within the garnet–spinel transition zone. Melting started at about 100 km depth and continued usually up to the base of the lithosphere. Thus, the final melting pressure could indicate the ambient lithosphere–asthenosphere boundary. The asthenospheric mantle source regions of the basalts were heterogeneous, presumably in small scale, and included either some water or pyroxenite/eclogite lithology in addition to the fertile to slightly depleted peridotite. Based on the prevailing estimated mantle potential temperature (1,300–1,400 °C) along with the number of further observations, we exclude the existence of mantle plume or plume fingers beneath this region. Instead, we propose that plate tectonic processes controlled the magma generation. The Pannonian basin acted as a thin spot after the 20–12 Ma syn-rift phase and provided suction in the sublithospheric mantle, generating asthenospheric flow from below the adjoining thick lithospheric domains. A near-vertical upwelling along the steep lithosphere–asthenosphere boundary beneath the western and northern margins of the Pannonian basin could result in decompressional melting producing low-volume melts. The youngest basalt volcanic field (Perşani) in the region is inferred to have been formed due to the dragging effect of the descending lithospheric slab beneath the Vrancea zone that could result in narrow rupture at the base of the lithosphere. Continuation of the basaltic volcanism cannot be excluded as inferred from the still fusible condition of the asthenospheric mantle. This is reinforced by the detected low-velocity seismic anomalies in the upper mantle beneath the volcanic fields.
The occurrence, shape, structure and eruption style of monogenetic volcanoes, such as maars, tuff rings, tuff cones and scoria cones, are generally governed by several internal (composition of the magma, magmatic flux, ascent rate, viscosity, volatile contents) and external conditions (regional and local tectonics, topography, and the presence of surfacial, ground and meteoric water). These controlling factors are together responsible for the eruption style, distribution pattern, volcanic facies architecture and morphology of the monogenetic volcanic landforms.
The United Nations Educational, Scientific and Cultural Organization promotes conservation of geological and geomorphological heritage through the promotion and protection of sites of importance and the development of educational programs under the umbrella of geoparks. Here, we identify significant volcanic features that could be organised and promoted as the first geopark in the Kingdom of Saudi Arabia. The Al Madinah Volcanic Field, or Harrat Al Madinah, has numerous volcanic geosites relevant to the understanding of the evolution of intraplate volcanic fields dominated by Hawaiian and Strombolian style eruptions, and includes the location of the last historically erupted volcanoes in the Arabian Peninsula. The unique volcanic features of the proposed Harrat Al Madinah Volcanic Geopark (HAMVG) are organised within three precincts, each with specific volcanic phenomena. The first and most accessible precinct, defined as the “Historic Eruption Precinct—1256 AD and 641 AD Historic Eruption Sites”, contains two major geotops with numerous individual geosites representing the youngest volcanoes of the Arabian Peninsula, including the lava spatter and scoria cones of the 1256 AD eruption just 10 km SE of Al Madinah city. The second precinct, “Lava Lakes, Lava Fountains and Volcano Spreading Precinct—The Mosawdah Volcano”, provides an in-depth view of an eruption that produced low lava fountains, clastogenic lava flows, agglutinated lava spatter cones and extensive lava flows from a central, lava lake-occupied crater. In the third precinct, referred to as “Silicic Lava Domes and Explosion Craters Precinct”, the results of explosive eruptions are visible, with deep craters and ash blankets around the vents. Here, there is also evidence for how trachytic lava can protrude from single and multiple vents to build lava domes. This precinct also offers the most dramatic landscape and adventure volcano tourism opportunity in this arid environment. This three-level hierarchy of the proposed HAMVG fits well with the gradual educational program proposed here to demonstrate the recent and potential future volcanism of the region, from the most common but less destructive to the less common but more hazardous eruptions. The proposed HAMVG will promote the protection of this globally unique, young volcanic landscape and offer geoeducational opportunities to the general public and to the scientific community. The Harrat Al Madinah is also located in a culturally significant place near to Al Madinah city, which is one of the holiest places to Muslims. The proposed geopark is easily accessable through highways (and by train in the near future) and it could provide a significant economic benefit to Al Madinah city.
Conference title - Second international maar conference, Copyright - GeoRef, Copyright 2012, American Geosciences Institute. Reference includes data supplied by Hungarian Geological Library, Budapest, Hungary, Date revised - 2009-01-01, Language of summary - English, Pages - 50, ProQuest ID - 50553330, SubjectsTermNotLitGenreText - Cenozoic; cores; Europe; geomorphology; maars; Neogene; Pannonian Basin; Pliocene; Pula Maar; Tertiary; three-dimensional models; volcanic features; volcanoes, SuppNotes - Pieces: 107., Last updated - 2012-06-07, CODEN - #05177, docISBN - 9636712409, Corporate institution author - Csillag, Gabor; Nemeth, Karoly; Martin, Ulrike; Goth, Kurth; Suhr, P, DOI - 2009-000407; 9636712409; #05177
Copyright - GeoRef, Copyright 2012, American Geosciences Institute. Reference includes data supplied by Institute of Geological and Nuclear Sciences Limited (GNS Science), Lower Hutt, New Zealand, Date revised - 2012-01-01, Language of summary - English, Number of references - 115, Pages - 34, ProQuest ID - 916836417, Document feature - illus., SubjectsTermNotLitGenreText - Australasia; base surges; Cenozoic; diatremes; erosion; field trips; guidebook; igneous rocks; intrusions; maars; Miocene; Neogene; New Zealand; Otago New Zealand; phreatomagmatism; pyroclastics; scoria; South Island; Tertiary; tuff; volcanic rocks; volcanism; Waipiata volcanic field, SuppNotes - Field trip 9. Field guide accompanies the Geological Society of New Zealand and New Zealand Geophysical Society joint annual conference, held in Oamaru, Nov. 23-27, 2009. Accessed on Dec. 28, 2011, Last updated - 2012-06-07, docISBN - 9781877480089, Corporate institution author - Nemeth, Karoly; White, James, DOI - 2012-011594; 0113-1532; 9781877480089
Cited By (since 1996): 5, Export Date: 4 January 2013, Source: Scopus, doi: 10.1016/j.geomorph.2011.08.005, Language of Original Document: English, Correspondence Address: Kereszturi, G.; Volcanic Risk Solutions, Institute of Natural Resources, Massey University, PO Box 11 222, Palmerston North, New Zealand; email: kereszturi_g@yahoo.com, References: Auer, A., Martin, U., Németh, K., The Fekete-hegy (Balaton Highland Hungary) soft-substrate and hard-substrate maar volcanoes in an aligned volcanic complex-implications for vent geometry, subsurface stratigraphy and the paleoenvironmental setting (2007) Journal of Volcanology and Geothermal Research, 159, pp. 225-245;
The Fekete-hegy volcanic complex is located in the centre of the Bakony Balaton Highland Volcanic Field, in the Pannonian Basin, which formed from the late Miocene to Pliocene period. The eruption of at least four very closely clustered maar volcanoes into two clearly distinct types of prevolcanic rocks allows the observation and comparison of hard-substrate and soft-substrate maars in one volcanic complex. The analyses of bedding features, determination of the proportion of accidental lithic clasts, granulometry and age determination helped to identify and distinguish the two types of maar volcanoes. Ascending magma interacted with meteoric water in karst aquifers in Mesozoic carbonates, as well as in porous media aquifers in Neogene unconsolidated, wet, siliciclastic sediments. The divided basement setting is reflected by distinct bedding characteristics and morphological features of the individual volcanic edifices as well as a distinct composition of pyroclastic rocks. Country rocks in hard-substrate maars have a steep angle of repose, leading to the formation of steep sided cone-shaped diatremes. Enlargement and filling of these diatreme is mainly a result of shattering material by FCI related shock waves and wall-rock collapse during downward penetration of the explosion locus. Country rocks in soft-substrate maars have much shallower angles of repose, leading to the formation of broad, bowl shaped structures or irregular depressions. Enlargement and filling of these diatremes is mainly the result of substrate collapse, for example due to liquefaction of unconsolidated material by FCI-related shock waves, and its emplacement by gravity flows. The Fekete-hegy is an important example illustrating that the substrate of a volcanic edifice has to be taken into account as an important interface, which can have major control on phreatomagmatic eruptions and the resulting characteristics of the volcanic complex.
Bondoró Volcanic Complex (shortly Bondoró) is one of the most complex eruption centre of Bakony-Balaton Highland Volcanic Field, which made up from basaltic pyroclastics sequences, a capping confined lava field (~4 km 2) and an additional scoria cone. Here we document and describe the main evolutional phases of the Bondoró on the basis of facies analysis, drill core descriptions and geomorphic studies and provide a general model for this complex monogenetic volcano. Based on the distinguished 13 individual volcanic facies, we infer that the eruption history of Bondoró contained several stages including initial phreatomagmatic eruptions, Strombolian-type scoria cones forming as well as effusive phases. The existing and newly obtained K-Ar radiometric data have confirmed that the entire formation of the Bondoró volcano finished at about 2.3 Ma ago, and the time of its onset cannot be older than 3.8 Ma. Still K-Ar ages on neighbouring formations (e.g. Kab-hegy, Agár-teto) do not exclude a long-lasting eruptive period with multiple eruptions and potential rejuvenation of volcanic activity in the same place indicating stable melt production beneath this location. The prolonged volcanic activity and the complex volcanic facies architecture of Bondoró suggest that this volcano is a polycyclic volcano, composed of at least two monogenetic volcanoes formed more or less in the same place, each erupted through distinct, but short lived eruption episodes. The total estimated eruption volume, the volcanic facies characteristics and geomorphology also suggests that Bondoró is rather a small-volume polycyclic basaltic volcano than a polygenetic one and can be interpreted as a nested monogenetic volcanic complex with multiple eruption episodes. It seems that Bondoró is rather a "rule" than an "exception" in regard of its polycyclic nature not only among the volcanoes of the Bakony-Balaton Highland Volcanic Field but also in the Neogene basaltic volcanoes of the Pannonian Basin.
Columnar jointing is a common feature of solidified lavas, sills and dikes, but the factors controlling the characteristic
stoutness of columns remain debated, and quantitative field observations are few in number. In this paper, we provide quantitative
measurements on sizing of columnar joint sets and our assessment of the principal factors controlling it. We focus on (1)
chemistry, as it is the major determinant of the physical (mechanical and thermal) properties of the lava, and (2) geology,
as it influences the style of emplacement and lava geometry, setting boundary conditions for the cooling process and the rate
of heat loss. In our analysis, we cover lavas with a broad range of chemical compositions (from basanite to phonolite, for
six of which we provide new geochemical analyses) and of geological settings. Our field measurements cover 50 columnar jointing
sites in three countries. We provide reliable, manually digitized data on the size of individual columns and focus the mathematical
analysis on their geometry (23,889 data on side length, of which 17,312 are from full column sections and 3,033 data on cross-sectional
area and order of polygonality). The geometrical observations show that the variation in characteristic size of columns between
different sites exceeds one order of magnitude (side length ranging from 8 to 338cm) and that the column-bounding polygons’
average order is less than 6. The network of fractures is found to be longer than required by a minimum-energy hexagonal configuration,
indicating a non-equilibrium, geologically quick process. In terms of the development and characteristic sizing of columnar
joint sets, our observations suggest that columns are the result of an interplay between the geological setting of emplacement
and magma chemistry. When the geological setting constrains the geometry of the emplaced body, it exerts a stronger control
on characteristic column stoutness. At unconstrained geometries (e.g. unconfined lava flows), chemistry plays the major role,
resulting in stouter columns in felsic lavas and slenderer columns in mafic lavas.
KeywordsColumnar jointing–Factors influencing column size–Column size measurements–Chemical composition–Geological setting–Geometry of the emplacement–Cooling rate
The Plio-Pleistocene Llancanelo Volcanic Field, together with the nearby Payun Matru Field, comprises at least 800 scoria cones and voluminous lava fields that cover an extensive area behind the Andean volcanic arc. Beside the scoria cones in the Llancanelo Field, at least six volcanoes show evidence for explosive eruptions involving magma–water interaction. These are unusual in the context of the semi-arid climate of the eastern Andean ranges. The volcanic structures consist of phreatomagmatic-derived tuff rings and tuff cones of olivine basalt composition. Malacara and Jarilloso tuff cones were produced by fallout of a range of dry to wet tephra. The Malacara cone shows more evidence for a predominance of wet-emplaced units, with a steep slump-slope characterized by many soft-sediment deformation structures, such as: undulating bedding planes, truncated beds and water escape features. The Piedras Blancas and Carapacho tuff rings resulted from explosive eruptions with deeper explosion loci. These cones are hence dominated by lapilli tuff and tuff units, emplaced mainly by wet and/or dry pyroclastic surges. Carapacho is the only centre that appears to have started with phreatomagmatic eruptions, with lowermost tephra being rich in non-volcanic country rocks. The presence of deformed beds with impact sags, slumping textures, asymmetrical ripples, dunes, cross- and planar lamination, syn-volcanic faulting and accretionary lapilli beds indicate an eruption scenario dominated by excessive water in the transportational and depositional regime. This subordinate phreatomagmatism in the Llancanelo Volcanic Field suggests presence of ground and/or shallow surface water during some of the eruptions. Each of the tuff rings and cones are underlain by thick, fractured multiple older lava units. These broken basalts are inferred to be the horizons where rising magma interacted with groundwater. The strong palagonitization at each of the phreatomagmatic cones formed hard beds, resistant to erosion, and therefore the volcanic landforms are well-preserved.
Neogene alkaline basaltic rocks in the western Pannonian Basin are eroded remnants of maars, tuff rings, tuff cones, scoria cones and lava fields. The erosion level of these volcanoes is deep enough to expose diatreme zones associated with the phreatomagmatic volcanoes. The erosion level is deeper yet in the west, exposing shallow dyke and sill swarms related to former intra-plate volcanoes. The basanitic sills are irregular in shape and their lateral extent is highly variable. Individual sills reach a thickness of a few tens of metres and they commonly form dome-like structures with rosette-like radial columnar joint patterns. The largest sill system identified in this region is traceable over kilometres, and forms a characteristic ridge running north-east to south-west. Elevation differences in the position of the basanitic sills within an otherwise undisturbed “layer cake-like” siliciclastic succession indicate emplacement of the basanite magma at multiple levels over kilometre-scale distances. The margins of sills in the system are irregular at a dm-to-mm-scale. Undulating contacts of the sills together with gentle thermal alteration in the host sediment over cm-to-dm distances indicate the soft, but not necessarily wet state of the host deposits at the time sills were intruded. Parts of the sill complex show a complicated relationship with the host sediment in form of peperitic zones and irregularly shaped, disrupted, peperite textures. This is interpreted to reflect inhomogenities in water content and rheology of the siliciclastic deposits during intrusion. The current summit of the longest continuous ridge preserves a small diatreme that seems to cut through an otherwise disk-like sill indicating of relationship between sill emplacement and phreatomagmatic explosive eruptions.
Pula maar is a partially eroded Pliocene maar-diatreme volcano, part of the Mio-Pliocene Bakony-Balaton Highland Volcanic Field. The surficial remnant of the maar-diatreme volcano consists of (1) a distinct depression with a thick post-eruptive lacustrine alginite sediment infill interbedded with coarse-grained volcaniclastic sediments, (2) a narrow marginal zone inside the depression consisting of primary pyroclastic rock units that are interpreted to be partly collapsed and subsided blocks of entire sections from the tephra ring formerly surrounding the maar crater depression, and (3) coarse-grained volcaniclastic debris-flow deposits closely associated with the collapsed primary pyroclastic rock units in the marginal zone. The presence of coherent lava rocks below the crater-fill units, their distribution pattern and their association with scoriaceous beds indicate that, after the maar-diatreme-forming phreatomagmatic explosive activity, small (100 m-scale) scoria and/or spatter cones erupted in the maar crater. These cones are the likely source of the lava flows that partially filled the maar crater basin. The widespread dm-to-m thick basaltic sand and/or silt units at the base of the post-eruptive crater-filling sedimentary succession are interpreted to be reworked volcaniclastic material from the intra-maar scoria/spatter cones as well as from the tephra ring. Based on comparative analyses of 53 core descriptions, this study reveals that the original maar crater basin was larger than previously suggested. The deep level of the maar crater is reconstructed to be a northeast–southwest elongated depression, currently forming a c. 50-m-deep basin. Geomorphological considerations suggest that most of the phreatomagmatic pyroclastic rocks are composed of base surge and tephra fall deposits around the deep maar depression. These allochthonous rock units form a 50–400 m wide zone of proximal tuff-ring sequences. The formation of this zone is inferred to be a result of a combination of syn-eruptive subsidence due to mass deficit in the rigid Triassic dolomite basement caused by the phreatomagmatic explosions as well as post-eruptive subsidence of the crater- and diatreme-filling successions due to diagenetic compaction. The facies in the centre of the maar lake is a soft laminated “alginite” (mainly Botryococcus colonies, diatom frustles, calcium carbonate crystals, clay minerals). In the section exposed in the Pula open cast mine, a single turbiditic layer is present. This layer originated in a landslide, which possibly could have been caused by either syn-eruptive earthquake and/or a sudden post-eruptive subsidence event of the diatreme fill.
The palaeogeographic evolution of the Paratethyan and Mediterranean realms are reconstructed with three maps ranging from the Late Miocene to the Middle–Late Pliocene. The maps are based on the facial analysis of selected deposits, clastic input, slope-slide process analyses as well as biogeographic data of the planktic, benthic and terrestrial biota. Characteristic fossil assemblages are used for palaeobathymetric and palaeohydrologic interpretations, restoration of palaeogeographic connections. The palaeogeographic reconstructions are palinspastically restored (after [Dercourt, J., Ricou, L.-E., Vrielynck, B. (Eds.), 1993. Atlas Tethys Palaeoenvironmental Maps. Gauthier-Villars, Paris, pp. 1–307, 14 maps; The Paleogeographic Atlas of Northern Eurasia, 1997. Inst. Tectonics Lithospheric Plates. Moscow. 26 maps], with modifications). Maps have been prepared for the terminal Tortonian/early Messinian–Late Pannonian/early Maeotian, Late Messinian–Pontian (salinity crisis time) and Piacenzian/Gelasian–Akchagilian. They illustrate the Neogene palaeogeographic evolution during and after the Attic orogenesis. Though the emerging mountain system of the Alpine foldbelt increasingly separated the Paratethys from the Mediterranean, Tethys–Paratethys connections remained extant and sufficiently effective for limited communication between both basins. They governed many features of the cyclic depositional history and biogeographic evolution of the Eastern Paratethys.
Neogene alkaline basaltic volcanic fields in the western Pannonian Basin, Hungary, including the Bakony–Balaton Highland and the Little Hungarian Plain volcanic fields are the erosional remnants of clusters of small-volume, possibly monogenetic volcanoes. Moderately to strongly eroded maars, tuff rings, scoria cones, and associated lava flows span an age range of ca. 6 Myr as previously determined by the K/Ar method. High resolution 40Ar/39Ar plateau ages on 18 samples have been obtained to determine the age range for the western Pannonian Basin Neogene intracontinental volcanic province. The new 40Ar/39Ar age determinations confirm the previously obtained K/Ar ages in the sense that no systematic biases were found between the two data sets. However, our study also serves to illustrate the inherent advantages of the 40Ar/39Ar technique: greater analytical precision, and internal tests for reliability of the obtained results provide more stringent constraints on reconstructions of the magmatic evolution of the volcanic field. Periods of increased activity with multiple eruptions occurred at ca. 7.95 Ma, 4.10 Ma, 3.80 Ma and 3.00 Ma.These new results more precisely date remnants of lava lakes or flows that define geomorphological marker horizons, for which the age is significant for interpreting the erosion history of the landscape. The results also demonstrate that during short periods of more intense activity not only were new centers formed but pre-existing centers were rejuvenated.
Kissomlyó volcano is a Pliocene erosion remnant of an alkaline basaltic tuff ring, belonging to the Little Hungarian Plain Volcanic Field. Late Miocene shallow subaqueous, fluvio-lacustrine sand and mud units underlie sub-horizontally bedded lapilli tuff and tuff beds with an erosional contact. The pyroclastic units, a sequence up to ∼20 m thick, constitute a semi-circular mound with gentle (< 5°) inward-dipping beds. Sedimentary features and field relationships indicate that the pyroclastic units were formed in a terrestrial setting. Phreatomagmatic explosions occurred at a shallow depth, producing a large amount of juvenile ash and lapilli, which were transported and deposited predominantly by pyroclastic density currents, subordinate fallout and reworked by gravity currents. The tuff ring is overlain by a 5 m thick sequence of cross- and parallel laminated siltstone and mudstone deposited in a lake inferred to have developed in a crater. The textural and structural differences between the lacustrine units beneath and above the tuff ring sequences suggest that they did not belong to the same lacustrine environment. The post-tuff ring lacustrine sequence is invaded by basanite pillow lava. The lava shows a basal peperitic margin partially destroying the original structure of the lacustrine beds due to fluidisation. The time gap between the tuff ring formation and the emplacement of the lava flow is estimated to be in the order of thousands of years.
The study of peperite is important for understanding magma–water interaction and explosive hydrovolcanic hazards. This paper reviews the processes and products of peperite genesis. Peperite is common in arc-related and other volcano-sedimentary sequences, where it can be voluminous and dispersed widely from the parent intrusions. It also occurs in phreatomagmatic vent-filling deposits and along contacts between sediment and intrusions, lavas and hot volcaniclastic deposits in many environments. Peperite can often be described on the basis of juvenile clast morphology as blocky or fluidal, but other shapes occur and mixtures of different clast shapes are also found. Magma is dominantly fragmented by quenching, hydromagmatic explosions, magma–sediment density contrasts, and mechanical stress as a consequence of inflation or movement of magma or lava. Magma fragmentation by fluid–fluid shearing and surface tension effects is probably also important in fluidal peperite. Fluidisation of host sediment, hydromagmatic explosions, forceful intrusion of magma and sediment liquefaction and shear liquification are probably the most important mechanisms by which juvenile clasts and host sediment are mingled and dispersed. Factors which could influence fragmentation and mingling processes include magma, host sediment and peperite rheologies, magma injection velocity, volatile content of magma, total volumes of magma and sediment involved, total volume of pore-water heated, presence or absence of shock waves, confining pressure and the nature of local and regional stress fields. Sediment rheology may be affected by dewatering, compaction, cementation, vesiculation, fracturing, fragmentation, fluidisation, liquefaction, shear liquification and melting during magma intrusion and peperite formation. The presence of peperite intraclasts within peperite and single juvenile clasts with both sub-planar and fluidal margins imply that peperite formation can be a multi-stage process that varies both spatially and temporally. Mingling of juvenile clast populations, formed under different thermal and mechanical conditions, complicates the interpretation of magma fragmentation and mingling mechanisms.