Browsing by Author "Martin, Ulrike"

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    40Ar/39Ar geochronology of Neogene phreatomagmatic volcanism 3 in the western Pannonian Basin, Hungary
    (Elsevier, 2007) Németh, Károly; Wijbrans, Jan; Martin, Ulrike; Balogh, Kadosa
    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.
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    Depositional record of a Pliocene nested multivent maar complex at Fekete-hegy, Pannonian Basin, western Hungary.
    (Massey University., 2002-01-01) Martin, Ulrike; Nemeth, Karoly; Auer, Andreas; Breitkreutz, Christoph; Csillag, Gabor
    No abstract available
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    Eruptive mechanism of phreatomagmatic volcanoes from the Pinacate Volcanic Field: comparison between Crater Elegante and Cerro Colorado, Mexico.
    (Massey University., 2004-01-01) Martin, Ulrike; Nemeth, Karoly
    No abstract available
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    Gerce, Hungary - Tapolca basalt formation (a) and pula alginite formation
    (Regional Committee on Mediterranean Neogene Stratigraphy, 2005) Nemeth, Karoly; Martin, Ulrike; Magyar, Imre
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    Influence of titanomagnetite composition on the magnetic anisotropy in a dyke-sill complex in Hungary
    (Massey University., 2006-01-01) Renk, Danny; de Wall, Helga; Martin, Ulrike; Nemeth, Karoly
    In the last decades low-field magnetic susceptibility measurements have become an increasingly attractive method for geological studies which use the scalar values (bulk susceptibility) as well as the directional information, the anisotropy of magnetic susceptibility (AMS). Because of the potential for detecting weak fabric anisotropies, AMS has become a routine method for assessing flow directions in magmatic bodies. Sources of AMS in ferrimagnetic basaltic rocks are mainly titanomagnetites. After Jackson et al. (1998) and de Wall (2000), the magnetic susceptibility (MS) of titanomagnetite varies strongly with mineral composition and is in the low-field range strongly depending on the field amplitude of the inducing magnetic field. Here we present a systematic study to record the effects of field dependence on AMS of dykes, sills and lava flows. Variation in MS characteristics have been found indicative for lava emplacement and flow dynamics (Cañón-Tapia et al. 1997, Cañón-Tapia & Pinkerton 2000). The contribution of the effect of field dependence on MS and AMS in titanomagnetite-bearing volcanic rocks needs to be assessed for a reliable interpretation of AMS variations. The key study has been carried out at the Ság-hegy volcanic complex in the Little Hungarian Plain. It is composed of a phreatomagmatic tuff ring, formed during the pliocene-miocene period. After meteoric water supply ended, the phreatomagmatic eruptive style changed into an effusive behaviour and the tephra ring was filled with a lava lake and a dyke-sill complex transected the pyroclastic successions. We report AMS characteristics of sills, dykes and lavas from the lake interior and outflowing lava deposits. Furthermore we discriminated samples that represent the transition from dykes to sills and from intrusive (dyke) to effusive (lava flow) emplacement, respectively. The MS has been measured by a KLY-4S kappabridge (AGICO, Brno) which allows a record of the AMS at a high sensitivity and in various field amplitudes (2 to 450 A/m).
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    Interaction between lava lakes and pyroclastic sequences in phreatomagmatic volcanoes: Haláp and Badacsony, Western Hungary.
    (Massey University., 2002-01-01) Martin, Ulrike; Nemeth, Karoly
    No abstract available
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    Large hydrovolcanic field in the Pannonian Basin: general characteristics of the Bakony- Balaton Highland Volcanic Field, Hungary.
    (Massey University., 1999-01-01) Nemeth, Karoly; Martin, Ulrike
    No abstract available
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    Lepusztult maar/diatrema szerkezetek a Bakony-Balaton Felvidék Vulkáni Területröl (Eroded maar/diatrema structures from the Bakony-Balaton Highland Volcanic Field).
    (Massey University., 2003-01-01) Nemeth, Karoly; Martin, Ulrike; Csillag, Gabor
    The Bakony - Balaton Highland Voclanic Field (BBHVF) is a Late Miocene/Pliocene alkaline basaltic intraplate monogenetic volcanic field comprises variable eroded maars, tuff rings, cinder cones and valley-ponded lavaflows/fields. Large volcanic edifices are relatively well studied in volcanological point of view but smaller occurrences of pyroclastic rocks have not yet been dealt with at Bakony - Balaton Highland Voclanic Field. However, their presence could give a good reference for erosion rate calculations of the syn-volcanic (Pliocene) landscape and develop better understanding of the eruption mechanism of phreatomagmatic volcanoes. Five, small volume pyroclastic rock occurrences have been mapped and studied. Each of these pyroclastic rock locations are ellipsoid in plane and seems to exhibit angular contact with the pre-volcanic rock units. The identified pyroclastic rocks are predominantly lapilli tuffs and minor pyroclastic breccias. They are rich in accidental lithic fragments picked up from the former conduit wall-forming rock units. All of the lapilli tuffs are rich in juvenile fragments. Juvenile fragments are both tachylite and sideromelane glass shards, indicative for variable degree of magma/water interaction as well as variable travelling time through air by the clasts. The two major types of juvenile fragments are 1) clear, light yellow, slightly microvesicular, and microcrystalline sideromelane glass shard and 2) strongly oriented, textured, trachytic textured, dark colour, slightly vesicular lava, and/or tachylite glass shards. The presence of this type of juvenile fragments, especially the presence of sideromelane, suggests sudden cooling and fragmentation of the intruding melt due to phreatomagmatic magma/water interaction. The composition of the volcanic glass shards is predominantly tephrite, phonotephrite (light colour, chilled, microlite-poor shards) or trachybasalt (trachytic texture, microlite-rich shards). However, the composition and texture of the glass shards are often affected by variable degree of palagonitization, which proccess clearly occurs in larger glass shards, leaving intact only the interior of the shards, and creating darker yellow rim around the glass shard. The glass shards, both sideromelane and tachylite, contain a large number of entrapped sedimentary clasts, vesicle-filling xenoliths. These xenoliths are both 1) pre-volcanic fluvio-lacustrine, shallow marine silts, sand or mud and 2) pyroclastic unit-derived fragments. Their presence marks the importance of the interaction and possible pre-mixing prior to phreatomagmatic fragmentation and disruption of the bedrocks by the intruding alkaline basaltic magma and water-rich slurry. The slurry is inferred to be a volcanic conduit-filling mixture of fluvio-lacustrine/shallow marine siliciclastic and pyroclastic debris, rich in water from different sources, such as ground-water, valley floor occupied swamp, creek, or small lake water. The lapilli tuffs contain both shallow-level pre-volcanic and deep-level basement rock fragments, indicating that the explosion locus migrated during eruption and sampled a thick section of the pre-volcanic rock units. Sedimentary clasts are common from the immediate pre-volcanic rock unit (Pannonian sand), regardless that they are already eroded in the areas or just represented by thin veneers. This finding suggests that these sediments were widespread in syn-volcanic time. Based on the textural characteristics, field relationships and the micro-textures of the studied pyroclastic rock exposures, they are interpreted to be deeply eroded sub-surface structures of phreatomagmatic volcanoes. According to the unsorted, chaotic features of these pyroclastic rocks, they are inferred to be exposed lower diatremes. Steeply dipping beds of near-vent base surge and air-fall beds interpreted to be collapsed and later subsided blocks of crater-rim deposits.
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    MAAR conference in Hungary
    (Massey University., 2005-01-01) Martin, Ulrike; Nemeth, Karoly
    No abstract available
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    Magnetic characteristics of the Ság-hegy volcanic complex, little Hungarian Plain
    (Massey University., 2006-01-01) Dvorazik, Nina; Auer, Andreas; Martin, Ulrike; Nemeth, Karoly; de Wall, Helga; Rolf, Christoph
    The Ság-hegy volcanic complex is located in the little Hungarian Plain Volcanic Field (LHPVF). An 39Ar/ 40Ar geochronolgy gave an isochron age of 5,42 ±0,06 My for the Ság- hegy (Wijbrans et al. 2004). Evolution of the volcano included two clearly distinct events. At first ascending magma entered meteoric water in a fluvio-lacustrine environment. Fuel-coolant interaction (FCI) of water (water saturated sediment) and magma led to the formation of a phreatomagmatic tuff ring. After water supply was used up the interior of the tephra ring was filled by a lava lake. Locally the tuff ring wall collapsed and subsequently lava was able to flow out of the tuff ring. Due to intensive quarrying most of the effusive rocks have been removed, giving excellent insight to emplacement processes of feeder dykes, sills and lava lake remnant (Martin and Németh, 2004). Pyroclastic rocks include massive and bedded units of lapilli stone, lapilli tuff/ tuff as well as pyroclastic breccias. Varying proportions of accidental lithic clasts indicate excavation of basement rocks during the erruption. Juvenile clasts comprise mainly of angular, blocky sideromelane glass shards with nearly equent shapes and a minor proportion of tachylite. A high amount of water within the systeme is evidenced by soft sediment deformation and accretionary lapilli in the pyroclastic bedsets. Dune and antidune bedding, chute and pool structures grading and sorting features suggest that the tuff ring was gradually built up by base surge and intercalated fallout deposits. Subsequent to the phreatomagmatic stage the inner crater has been filled with a lava lake which morphology was determined by the tephra deposits. At contacts to the pyroclastics a chilled margin of several cm thickness is developed which shows platty (onion shaped) jointing. A high number of dykes and sills were injected into adjacent bedsets. These shallow intrusive bodys can be found throughout the whole complex truncating and dissecting the pyroclastic units. In cases where pyroclastic units comprised a high amount of water this included even mingling with the wet tephra, leading to the formation of peperites. The uppermost units were represented by thick lava flows, which covered all underlaying units. These rocks were quarryed out already a century ago except a large strombolian spatter cone which is now exposed at the uppermost level of the quarry as a big sliced remnant including its large multiple feeder dyke. This setting offers a perfect opportunity to study the relationship between dyke and sill enplacement with transitions from vertical to bedding-parallel geometries. Dimensions of the volcanic bodies range from cm thickness of small apophyses from the lava lake into the pyroclastic rocks up to dykes and sills of several m. We performed a detailed study on a section of pyroclastic rocks truncated by dykes and sills and have evaluated the magnetic characteristics. Preliminary results show that magnetic susceptibility of all the pyroclastic units is in the range of ferrimagnetic susceptibility and varies between 2 to 20 x 10-3 SI. (Fig.1). Magnetic fabric anisotropy is generally low (< 5 %) and in the field of oblate fabric geometries, in bedded tuffs a significantly higher (5 to 10 %) but also oblate anisotropy is realized. Magnetic lineations indicate a consistent NE (020) directed material transport for the whole succession. Remanence intensities are quite high with values of 1 to 15 A/m In the pyroclastic units a stable magnetic remanence characterized by a single vector component has been measured, MDF values are in the range of 30 to 160 mT. The field vector has exclusively reversed polarity and steep inclination, which is in agreement with the paleofield direction and therefore is regarded as natural remanent magnetization aquired during deposition of the pyroclastic successions. In the dykes and sills, however, remanence direction scatter significantly and display geometries ranging from steep to flat orientations and show also strong variations in the declination. Coercitivity of magnetic carriers is significanty lower as indicated by the lower MDF values which are in the range of 8 to 30 mT in the dykes and 15 to 30 mT in sills. Beside a minor contribution of a viscose component the remanence vector in the dykes and sills is characterized by a stable single component. However, further investigations are needed to fully understand and interpret the results
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    Mio/Pliocene phreatomagmatic volcanism in the Western Pannonian Basin
    (Massey University., 2004-01-01) Martin, Ulrike; Nemeth, Karoly
    No abstract available
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    Peperites and soft sediment deformation textures of a shallow subaqueous Miocene rhyolitic cryptodome and dyke complex, Pálháza, Hungary
    (Massey University., 2006-01-01) Nemeth, Karoly; Pecskay, Zoltan; Martin, Ulrike; Gmeling, Katalin; Molnar, Ferenc; Cronin, Shane J.
    Miocene rhyolitic shallow intrusions, cryptodomes and domes emplaced into soft, wet sediment in shallow subaqueous environment form a large intrusive complex in the NE side of the Tokaj Mts. at Pálháza in NE-Hungary. The intrusive complex show interaction textures with the host sediment where blocky peperites formed in a dm-scale, however, irregular contacts closely resembling globular mega-peperites are prominent in the tens of metres scale. The more than 200 m thick succession of intrusive complex interpreted to be a generally steadily growing shallow dyke, cryptodome, and dome complex in a shallow subaqueous environment, similar to those reported from Ponza, Italy.
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    Pitfalls in erosion level calculation based on remnants of maar and diatreme volcanoes (Les pièges de la reconstitution des topographies d'érosion initiales fondée sur les vestiges des maars et diatrèmes volcaniques)
    (Massey University., 2007-01-01) Nemeth, Karoly; Martin, Ulrike; Csillag, Gabor
    Abstract Erosion estimates based on geometrical dimension measurements of eroded maar/diatreme volcanoes are useful methods to determine syn-volcanic surface level and syn-volcanic bedrock stratigraphy. However, such considerations on volcanic architecture should only be employed as a first-order approach to determine the state of erosion. We demonstrate, on both young and eroded maar/diatreme volcanoes, that establishing the volcanic facies architecture gives vital information on the environment in which the volcano erupted. In 'soft' rocks, maar volcanoes are broad and underlain by 'champagne glass'-shaped diatremes. In contrast, the crater wall of maar volcanoes that erupted through "hard rocks" will be steep, filled with lacustrine volcaniclastic deposits and underlain by deep diatremes. Résumé L'estimation de l'érosion fondée sur la géométrie des volcans de type maar-diatrème est une méthode applicable à la reconstruction de la surface syn-volcanique et de la stratigraphie de la série sous-jacente. Toutefois les considérations relatives à l'architecture volcanique doivent seulement être utilisées comme une première approche pour déterminer le niveau initial de la surface aujourd'hui érodée. Nous démontrons que la détermination des faciès volcaniques, tant dans les maars-diatrèmes récents que dans les systèmes érodés de ce type, donne des informations fondamentales sur la nature des roches encaissantes au sein desquelles l'éruption volcanique s'est produite. Dans les roches encaissantes meubles, les maars sont larges avec un diatrème sous-jacent en forme de « coupe de champagne». Au contraire, au sein de roches plus résistantes, les cratères de maars sont entourés de parois raides et bien souvent remplis de dépôts lacustres d'origine volcanoclastique qui masquent des diatrèmes profonds.
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    Pliocene crater lake deposits and soft sediment deformation structures associated with a phreatomagmatic volcano, Pula maar, western Hungary.
    (Massey University., 2002-01-01) Nemeth, Karoly; Martin, Ulrike; Csillag, Gabor
    No abstract available
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    Practical volcanology - Lecture notes for understanding volcanic rocks from field based studies.
    (Geological Institute of Hungary, 2007) Martin, Ulrike; Nemeth, Karoly
    Volcanic rocks are important in compiling geological records because of their characteristic chemistry, relatively fast accumulation and great variety; however, recognizable facies diversity may be useful for reconstructing not only the volcanic processes but also the eruptive environment where the volcanism take place. Volcanic rocks that are significantly fragmented are important from a stratigraphic point of view and they can be used to study palaeoenvironments where these volcanic deposits formed. The increasing importance of fragmental volcanic rocks in geological research is clearly demonstrated by the increasing number of publications that have appeared over recent decades dealing with volcaniclastic deposits and rocks. Different volcanological schools and associated textbooks have been published since the 1980s. Among the many that have become available four are of particular significance These are Fisher and Schmincke(1984): Pyroclastic Rocks; CAS and WRIGHT (1987) Volcanic Successions; MCPHIE et al. (1993) Volcanic Textures; and SIGURDSSON et al (2000) Encyclopedia of Volcanoes. The aforementioned are among the many textbooks that are widely accepted and used in volcanology courses at different levels. The volume Practical Volcanology, as a textbook, does not intend to substitute any of the above books; rather, it tries to deal with volcanic geology from a slightly different aspect from those already cited. Practical Volcanology is a direct result of a series of short courses offered for first time in 2001 at the Geological Institute of Hungary, Budapest, primarily for geologists working in ancient volcanic terrains, and their main aim is general mapping. In addition, these short courses also intended to draw the attention of undergraduate students, postgraduates and research students who came across volcanic rocks during their research. The basic idea of Practical Volcanology is included in a study guide and lecture notes which could be used as a self-standing guide for interpreting volcanic processes and the resulting deposits and rocks. To take full advantage of this book a preliminary geological background is necessary for the user, especially in the field of classic sedimentology, petrology and geochemistry. However, a limited background of geological knowledge would enough to get a basic idea of field-based volcanology in its simplest aspects. The book's main aim is to introduce basic field volcanology research from a theoretical point of view right through very practical elements. The basic philosophy of the book is that, especially in ancient terrains, the volcanologist's basic data is found through fieldwork, and they are looking for volcanic rocks, especially fragmented ones. This book intends to demonstrate the link between the field subject, a volcanic rock and the volcanic process that may have formed that rock. Such textbooks or study guides are relatively rare these days and often they are too detailed or complicated for undergraduate students or interested amateurs. This book consists of 8 chapters. Each chapter is fully referenced in order to give a very detailed guide to any user and it clear where the individual citaitons/statements come from. This allows the user to go deeper into the scientific problems such processes, deposits, or the relevant terminology itself. Each chapter is accompanied with figures widely used and referred to in the international literature and there are full colour plates of textures, volcanic activity and the 3D architecture of volcanic deposits. The figures and colour plates are fully explained and referenced. In addition, each chapter has a locality map allowing the user to identify the site locations for future references. At the end of the book there is a detailed glossary along with a collection of terms from widely accepted textbooks, articles, and web resources. The book also contains a detailed index for quick search through the chapters for key volcanological terms. The 8 chapters set a logical path from an introduction, a key of terminological issues right through to different volcanic processes. The first chapter deals with a short summary and referenced description of major volcanic terminological systems. This chapter also gives a detailed insight of the usage of different terminologies and their potential for futureresearch documentation. The second chapter is a detailed summary of active volcanism and its relationship to volcanic deposits. This chapter intends to make clear the connection between active volcanism and the volcanic rocks that most mapping geologists deal with in the field. The third chapter focuses on fragmented volcanic rocks. Beside its classification scheme and a presentation of the common features of fragmented volcanic rocks this chapter provides a clear guide about the information which can be obtained from fragmented volcanic deposits and rocks. This chapter also gives indication of the limitation the information with respect to its use for inferring volcanic processes and eruptive environments. The fourth chapter gives an introduction to volcanic facies analysis which one of the main goals of studying volcanic rocks in the field. Volcanic facies analysis is the basic tool for broad making interpretations and can be connected to palaeoenvironmental reconstructions. The fifth and sixth chapters concentrate on summarising volcanic processes and the resulting volcanic deposits and rocks which are associated with the two major types of volcanism on Earth: i.e. monogenetic and polygenetic volcanism. In these two chapters not only field examples are given but also a large collection of young deposits and volcanic processes are examined to demonstrate clearly the connection between volcanic processes and the resulting deposits and rocks. The seventh chapter deals with processes which act on volcanic terrains and which can significantly modify the original primary volcanic landforms. Also in this chapter a basic concept - derived from those few studies dealing with the topic - of the erosion of volcanic terrains is introduced. The eighth chapter gives a concise summary of the potentially most widespread, but less known type of volcanism which occurs in subaqueous environments. Probably in ancient terrains the majority of volcanic rocks represent deposits that may have formed in some sort of subaqueous environment. In addition this type of volcanism has the potential to generate volcanic deposits that can host valuable ore minerals. The book is based on the expertise of two authors gathered over the past 15 years of their work in the field of volcanic geology. The authors have primarily used their own research data to demonstrate key features but where useful these have been collated with other field information from other researchers. The majority of the field and textual data has been provided by the authors. The figure collection is based on published and usually well-accepted research papers or textbooks in order to facilitate the user's ability to connect their own work to individual researchers and their publications. Practical Volcanology is a study guide which it is hoped will provide a good basis for developing short courses.
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    Quaternary phreatomagmatic volcanoes of southern Tenerife, Spain: Montana Pelada tuff ring and Caldera del Rey Maar.
    (Massey University., 2004-01-01) Martin, Ulrike; Nemeth, Karoly
    No abstract available
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    Subaqueous volcaniclastic successions in the Middle Triassic of Western Hungary
    (Geological Institute of Hungary, 2004) Budai, Tamas; Nemeth, Karoly; Martin, Ulrike; Piros, Olga
    No abstract available
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    Understanding the evolution of maar craters
    (Massey University., 2006-01-01) Haller, Miguel J.; de Wall, Helga; Martin, Ulrike; Nemeth, Karoly
    No abstract available