Browsing by Author "Németh, Károly"

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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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    The Arxan-Chaihe Volcanic Field of monogenetic volcanism in intracontinental settings in NE China : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Earth Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2024-02) Li, Boxin
    Pliocene to Recent Arxan-Chaihe Volcanic Field (ACVF) is composed of at least 47 vents, representing various types of volcanism, such as Strombolian style, phreatomagmatic explosive, effusive, and lava-fountaining eruptions. These eruptions produced scoria cones, fissure-aligned spatter cones, and tuff rings with a few surrounding maar craters. Field observations imply that the lava-fountaining eruptions are more common on the western side of ACVF, represented by Yanshan (YS)-the Triple Vent, and Daheigou (DHG). In the southwest part of ACVF, lava flows and loose pyroclastic ejecta, such as scoria, mark the eruption events that took place during the Holocene era about 2000 years ago. Dichi (Earth Pond) Lake, with fissures on its eastern side, formed by lava-effusive eruption styles with spatter rows occurring along a fissure, while the low-lying western side of the vent chain is a maar volcano cut into the pre-eruptive lava sheets. Tianchi (Heaven Lake) Lake and Tuofengling (Camel Hump) Lake on the western side of ACVF preserves a range of well-exposed pyroclastic deposits consistent with edifice-building successions. These are composed of scoriaceous pyroclastic materials, yielding construction histories of complex cones (with both "wet" and "dry" explosive eruptive phases). The most significant and largest vent is in the eastern corner of ACVF, Tongxin Lake, a complex phreatomagmatic eruption-style volcano with a maar crater and thick rim deposits. Tongxin Lake is interpreted to be a maar lake that erupted into an intra-montane basin. Intact pyroclastic deposits are preserved within a km from the crater rim and at least 5 meters thick. Stratigraphic and granulometric analyses from five sites around Tongxin Lake indicate the tuff ring of Tongxin was built by processes associated with magma-water interactions that fueled violent explosive eruptions during distinct syn-eruptive stages. Geochemistry is consistent with at least three magma sources contributing to the formation of the complex eruptive products that build the large tuff ring of the maar edifice. Geomorphology terrain analyses performed through GIS-based applications (QGIS) imply that the diverse range of local geology, especially the pre-eruptive topography, was confined and reshaped by the subsequent Pliocene to Recent volcanism in ACVF. Lava flows within ACVF were emplaced over large areas around the two major fluvial systems: Halaha River in the west and Chaoer River in the east of ACVF. The lava flows in the west of ACVF are generally young and can be modelled using the Q-LavHA plug-in of QGIS. The model has been utilized to simulate lava flow inundation and indicates diverse flow along the flow axis as well as lateral and temporal variations during the evolution of the edifice. Other studies of ACVF, e.g., hazard management, concluded that violent phreatomagmatic explosive events had impacted the fluvial valleys that are commonly associated with structural weakness zones in ACVF. In addition, lava-effusive and lava-fountaining eruptions in urban areas and along major utilities (e.g., roads, geopark facilities or powerlines) also could be heavily impacted by fissure-fed lava flows and potential phreatomagmatic explosions controlled by the local hydrology conditions.
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    Geodiversity estimation of the Coromandel Peninsula through a digital model analysis under special consideration of the geology and geomorphology of this region : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Earth Science at Massey University, Palmerston North, New Zealand, School of Agriculture and Environment
    (Massey University, 2024) Zakharovskyi, Vladyslav
    This thesis has drawn on a wide range of published research in understanding the term geodiversity in a philosophical and scientific context. Geodiversity description is one of the first steps in the establishment of geoparks, as it recognizes and describes the surface evolution of the physical research area. Subsequently it can lead to development of tools for geodiversity assessment and geosite recognition. The Coromandel Peninsula, New Zealand, has been selected as the research area for testing geodiversity description and assessment, because of its variety of geological and geomorphological compositions, formed through volcanic processes shaped by and interacting with a coastal environment. To provide a general scientific context, a literature review has been undertaken, supported by direct field observations. For estimation of geodiversity of the region, a qualitative-quantitative assessment of geodiversity (QQG) has been developed for areas with limited available data. Development of this framework was initiated by an in-depth systematic literature review of terminology relating to geodiversity. In developing this methodology, the abiotic environment has been divided into main and additional values (elements), according to their roles in shaping of geodiversity. This becomes the philosophical foundation for the new qualitative-quantitative methodology for geodiversity assessment. It is not only describing density of geosites in the studied area but also introduces a ranking system for assessing geodiversity. The ranking system applied to geological and geomorphological elements combined, can be used to describe any area globally, making it useful for comparative for assessment of different regions. Meanwhile, additional values are recognized for their impact in shaping and altering surface features. This approach is a completely new way to assess and describe geodiversity and its contribution to geoconservation, geotourism, and geoeducation. The foundation of QQG has been tested, corrected, and improved with several applications utilizing Geographical Information Systems (GIS), and supported by research. The result of this process is a geodiversity model for the whole Coromandel Peninsula, providing a deep description of potential geosites on the northern region of the peninsula. Therefore, the QQG methodology is now fully developed for assessment of territories and highlighting potential geosites, especially in cases where only low amounts of data are available. Our methodology does allow for addition of further data as it comes available, thereby expanding and improving results. Therefore, with enough elements included in the assessment, the methodology can be transformed from a geosite recognition tool to overall geodiversity description and modelling. In developing the methodology, it was also applied to regions outside of the Coromandel Peninsula for comparative testing on a range of differing geological and geomorphological compositions.