Introduction. Volcano-morphological relations of the Nagy Hill

Átírás

1 ACTA GGM DEBRECINA Geology, Geomorphology, Physical Geography Series DEBRECEN Vol. 3, Volcanomorphological concerns of the Nagy Hill at Tokaj and the Cigány Hill near Bodrogszegi village A tokaji Nagy-hegy és a bodrogszegi Cigány-hegy vulkánmorfológiai vonatkozásai Rita Osváth Árpád Csámer 2 Department of Mineralogy and Geology, University of Debrecen, H-032, Debrecen, Egyetem tér. gyopar@gmail.com 2BGT Hungaria Environmental Technology Ltd., H-9, Budapest, Keveháza u. -3. Abstract The Nagy Hill at Tokaj and the Cigány Hill at Bodrogszegi are very close to each other regarding not only location but age of formation and petrographic characters as well. While the Nagy Hill is well explored thanks to the numerous outcrops geological literature of the Cigány Hill is limited. For researching Hungarian volcanic mountains aerial photographss and space images were applied since the 970s. On the basis of GIS methods (Landsat TM-) only the dacite cone of the Nagy Hill was determined to be an explosion centre, however, based on geological descriptions the Cigány Hill at Bodrogszegi was also interpreted as an explosion centre. Numerous grain-size examinations were available related to both hills with the help of which the explosion centre nature of the Cigány Hill could have been justified. By plotting the matrix material content (<0 m) in relation to the SiO 2 content of the samples it can be seen that most of them plot into the volcanic field and only a few plot into the transition zone very close to the boundary of the volcanic field. Grain-size and textural analyses therefore justify the volcanic character of the Cigány Hill thus it can be regarded as a former explosion centre. Összefoglalás A tokaji Nagy-hegy és a bodrogszegi Cigány-hegy földrajzi helyzetüket, keletkezésük korát és k zettani kifejl désüket tekintve is igen közel állnak egymáshoz. Míg a Nagy-hegy a rengeteg feltárásnak köszönhet en jól megkutatottnak számít, addig a Cigány-hegy földtani irodalma meglehet sen sz kös. Vulkáni hegységeink kutatásához az 970-es évek óta használták fel a légifotók, majd az rfelvételek információit. Távérzékeléses módszerekre (Landsat TM-) támaszkodva csupán a tokaji Nagy-hegy dácitkúpjáról sikerült kimutatni annak kitörési centrum jellegét, míg a földtani leírásokon alapuló értelmezések a bodrogszegi Cigány-hegyet is kitörési központként említik. A két hegy területér l számos szemcsenagyság-összetételi vizsgálat állt rendelkezésünkre, ami lehet séget biztosított arra, hogy megvizsgáljuk, vajon alátámasztható-e az a feltételezés, miszerint a Cigány-hegy vulkáni kitörési központ volt. A minták alapanyag-tartalmát (<0 m) SiO 2 -tartalmuk függvényében ábrázolva megállapítható, hogy többségük a vulkáni tartomány mezejébe esik, míg néhány a bizonytalansági sávban, de a vulkáni tartomány határvonalához igen közel található. A szemcseösszetételi-szöveti vizsgálatok eredményei igazolják a Cigány-hegy vulkáni jellegét, azaz a Nagy-hegyhez hasonlóan, egykor kitörési központ lehetett. Keywords: Tokaj Mountains, volcanomorphology, grain-size distribution Tárgyszavak: Tokaji-hegység, vulkánmorfológia, szemcseméret-eloszlás Introduction The Nagy Hill at Tokaj town and the Cigány Hill near Bodrogszegi village are quite close to each other concerning their ages, locations and petrological characters. On the other hand, however, while the Nagy Hill, is wellstudied due to the numerous outcrops and excavations, the Cigány Hill is poorly recorded in the Hungarian geological literature. The Nagy Hill is the southernmost member of the Tokaj-Prešov volcanic range, and the Cigány Hill is located north of it (Fig. ). In the explanatory text of Sátoraljaújhely sheet of the : geological map series of Hungary (966) both hills are described as complex volcanic units formed by subvolcanic activities. This explanatory text mentioned their rock as pyroxene dacite, which is the valid term even today. Added that this term can be basically used as a consequence of their major element composition because the dacite of the Cigány Hill did not contain quartz. In the case of the rock of the Nagy Hill the term of quartz andesite would have been a petrographically more precise name. The main mass of the hills were formed in the Sarmatian, however, K/Ar radiometric age of the Nagy Hill indicates that its formation could be extended in the beginning of the Pannonian (SZÉKYNÉ et al. 98, PÉCSKAY et al. 987). Volcano-morphological relations of the Nagy Hill The Nagy Hill (or Kopasz [Bald] Hill) aroused the interest of travellers and scientists as early as the late 8 th century. The first petrographic description and chemical analysis of the dacite was published by TOWNSON (797), and he recognised the volcanic origin of the hill (SZÖ R et al. 999). BEUDANT (822) also introduced the rock in details, and it resembled him the rock found near Schemnitz, Bohunitz and Ribnik. According to KUBINYI (8) it is formed by black trachyte, and its peak region is similar to a collapsed crater. József Szabó, the most eminent Hungarian geologist in the 9 th century spent longer time in the area. During his several field trips he collected several samples of inclusions in the southern side of the hill (SZABÓ 866). On the basis of his experiences gained in the Nagy Hill, he described the phenomenon of the magma-mixing in one of his latest papers (SZABÓ 89). The first volcano-morphological summary on the Nagy Hill was published by Gyula Simkó. In his opinion, the Nagy Hill is a lava core originally covered by tuffaceous material, which was prepared from its stratovolcanic structure by denudation and erosion (SIMKÓ 926). The hill was built by one short eruption cycle; moreover, he describes remnants of three craters in the recent peak region. He regards the central peak as the source region of 27

2 ACTA GGM DEBRECINA Geology, Geomorphology, Physical Geography Series Vol the lava mass, and the area above m interprets as a rounded plateau formed during solidification of the lava mass. In his opinion, the main valleys originally had tectonic origin, and then were formed by erosion and weathering, and finally the loess also appeared as morphogenetic factor. According to FÖLDVÁRI (92) the Nagy Hill is a laccolith. This finding can be read in the explanation to the : geological map of the Tokaj Mountains, too (BALOGH, 966). 2 B C 3 D Legend : Holocene and Pleistocene fluvial and terrestrial sediments 2: Upper Sarmatian siliceous rocks, quartzites 3: Lower Sarmatian dacite : Lower Sarmatian acidic pyroxene andesite : Lower Sarmatian redeposited, air-fall, and welded rhyolite tuff 6.: Lower Sarmatian ignispumite and perlite 6 A: Nagy Hill B: Cigány Hill C: Hosszúmáj D: Poklos 0 km A 3 Figure Geological sketch of Nagy Hill and Cigány Hill (based on the : geological map series of the Hungarian Geological Institute). ábra A tokaji Nagy-hegy, a Cigány-hegy és környékének földtani felépítése (MÁFI es földtani térképe alapján) MOLNÁR (96) described lava channels in the Nagy Hill near Tarcal village. In his opinion, their formation were due to the fact that lava in the centre of the lava flow was hotter and less viscous than in the margin, and, as a consequence, it was more rapid and flew further there. On the basis of drilling data, SZLABÓCZKY (970, 97, 97, 2006) estimated the thickness of the dacite near Tarcal village to be about 00m. He suggests that the rock mass, which useful for quarrying can be found in fossil lava flows. Inclination of these flows is steeper than that of the recent surface; therefore, they became thinner and thinner toward the peak. He describes terrace-like plateaus, and assumed that they are remnants of former parasitic cones because the rock became harder here due to post-volcanic silicification processes. GYARMATI (97, 977) also mentioned dacite lava flows, and regards the rock mass of the Tarcal III quarry as one lava flow filling a former valley (Fig. 2). Precise extension of the lava flows of the Nagy Hill beneath the recent surface of the Great Hungarian Plain (90 00m above the sea level) has not been known. Since some water exploring drillings penetrated dacite in some ten meters beneath the surface, however, it can be supposed that some lava flows extend as deep as 0 60m above the sea level. Morphology of the hill is basically determined by spatial distribution of the dacite (length, width, thickness and direction of the lava flows) and the erosion-denudation conditions; this pattern is slightly modified by the young (Pleistocene) loess-cover characteristically some metres thick. Since the end of the Pleistocene some parts of the plain foreland has undergone slight tectonic vertical movement, however, these movements have no significant influence on the morphology of the hill. Figure 2 The Tarcal III quarry, which is excavated in a lava flow filling a former valley 2. ábra A Tarcal III. bánya, mely egy egykori völgyet kitölt lávafolyást tár fel The eight radial ridges coming from the peak are the most eye-striking morphological units of the Nagy Hill. On the basis of the exposures, it can be stated that these ridges are built up by several lava flows, which vertically and 28

3 Osváth, R. & Csámer, Á.: Volcanomorphological concerns of the Nagy Hill GENERAL GEOMORPHOLOGY horizontally touch and, partly, overlap each other. Volcanological and petrographical studies of the Tarcal III quarry (KOZÁK et al. 980, KOZÁK & RÓZSA 98) suggest that the lava flows of elliptically flattened cross-section show quite distorted cylindrical symmetry. Beside the ridges, the main and subordinate valleys between them form another main geomorphological group. In the formation of the valleys, the Pliocene-Pleistocene erosion played the main role. Regarding the eruption type the Miocene volcano of the Nagy Hill could be similar to the Strombolian type. Traces of explosive activity can be hardly observed; amounts of pyroclasts are quite subordinate. Essentially, the volcanism could be only one eruption series with short interruptions. The Nagy Hill, regarding its general appearance, rocks, and the lava/pyroclast ratio, can be related to the smaller stratovolcanoes essentially built up by lava (KOZÁK & RÓZSA 982). Volcano-morphological relations of the Cigány Hill Due to fact that there are very few natural of artificial outcrops, the Cigány Hill belongs to the less studied parts of the Tokaj Mountains. During his field trip in the Tokaj- Hegyalja, JÓZSEF SZABÓ (866) studied the contact of andesite trachyte and rhyolite tuff in the hill. GYARMATI (977) regards the Vár Hill near Erd bénye village as an independet volcanic centre, while he suggests the Vár Hill (south of the Cigány Hill near Bodrogkisfalud village) as well as dacite bodies of the Lapis, Kakas and Nyerges to be erosion remnants of a former extended sheets formed by lava flows (Fig. 3). Similarly, MÁTYÁS (978) regards the small pyroxene dacite bodies (Kakas, Nyerges, Hosszúmáj) to be lava flows filling valleys, i.e. volcanic appendices of the former Cigány Hill volcano. RÓZSA & BARTA (98) has similar opinion, however, they do not regard the former lava flow system as a volcanomorphological unit. Figure 3 Areal extension of the intermediate volcanic rocks of the Cigány Hill (based on the Mád and Olaszliszka sheets of the :2000 geological map series of the Hungarian Geological Institute). The arrows indicate the possible lava flow directions 3. ábra Az intermedier vulkanitok kiterjedése a Cigány-hegy környékén (a Tokaji-hegység :2 000-es földtani térképsorozatának Mád és Olaszliszka lapjai alapján). A nyilak a feltételezett lávafolyás-irányokat jelzik Volcano-morphological results of remote sensing studies Information coming from aerial and satellite photographs has been used for research of the Hungarian volcanic mountains since the 970s (CZAKÓ 973). These methods can be applied for identification of larger homogeneous bodies as well as detection of recognisable tectonic elements. These studies, connecting to the reinterpretation of geological mapping and aerogeophysical data, were also begun in the Tokaj Mountains (HORVÁTH et al. 989, FEGYVÁRI et al. 990). On basis of remote sensing (Landsat TM-), 37 palaeovolcanic structures have been detected in the Tokaj Mountains, comparing these results to field observations and geological interpretations further structures can be identified (ZELENKA 2000). The Miocene volcano of the Nagy Hill can be identified by remote sensing, however, the Cigány Hill is not listed among them. On the other hand, considering geological conditions, it can be regarded as a palaeovolcanic centre (ZELENKA 2000) (Fig. ). 29

4 ACTA GGM DEBRECINA Geology, Geomorphology, Physical Geography Series Vol Bodrog Tisza 0 km Figure Paleovolcanic structures in the southern part of the Tokaj Mountains (according to ZELENKA 2000). ábra Paleovulkáni szerkezetek a Tokaji-hegység déli részén (ZELENKA 2000 nyomán) Jelmagyarázat/Legend:. Tokaji Nagy-hegy, dácit Nagy Hill, dacite; 2. Tarcal, Terézia kápolna, riolit Tarcal village, Terézia Chapel, rhyolite; 3. Mád-Diósd andezit és riolit Mád village, Diósd, andesite and rhyolite;. Bodrogszegi Cigány-hegy, dácit Bodrogszegi village, Cigány Hill, dacite;. Erd bénye-fürd, riolit Erd bénye Bath, rhyolite; 6. Erd bénye, Mulató-hegy, andezit szubvulkán Erd bénye village, Mulató Hill, andesite subvolcano; 7. Erd bénye, Szokolya, olivines andezit Erd bénye village, Szokolya Hill, olivine-bearing andesite; 8. Apróhomoki fedett olivinbazalt Sárospatak town, Apróhomok, olivine basalt (covered); 9. Zalkodi fedett andezit, dácit Zalkod village, andesite, dacite (covered) Volcano-morphological interpretation of grain-size distribution of the dacites from the Cigány Hill On the basis of both geological and remote sensing data, the Nagy Hill can be certainly regarded as palaeovolcanic centre. In the case of the Cigány Hill, however, basically geologically evidences can be considered. Since several grain-size distribution data concerning the pyroxene dacite types of the Cigány Hill are available (Fig. ), it seems to be reasonable to investigate whether these data support or not the volcanic origin of the Cigány Hill. Because different cooling histories and different types of nucleation can lead to different grain size distribution, thus textures of magmatic rocks may be related to volcanic, hypabyssal and plutonic types. In the case of the Tokaj Mountains, experiences show that volcanic and hypabyssal rocks proved to be most separable when the groundmass (less than 0 micrometer) is plotted against their SiO 2 content recalculated on a H 2 O- and CO 2 -free basis (RÓZSA & PAPP 988, 996). As Figure 6 shows positions of pyroxene dacite samples from the Cigány Hill are quite similar to that of the pyroxene dacite from the Nagy Hill (sample 9). Moreover, pyroxene andesite samples from the Várhegy and the small hill north of it (samples and 2) are in the volcanic field, too. It means that grain-size distribution of most samples indicates volcanic origin. Some samples are in the transition (or uncertainty) zone, however they are quite close to the volcanic field. In our opinion, the boundary line between the volcanic field and the uncertainty zone should be specified by using further grain-size distribution data of rocks from undoubtedly volcanic centres. Figure Textural types of pyroxene dacite and pyroxene andesite of the Nagy Hill and Cigány Hill based on their grain-size distribution (based on RÓZSA & KOZÁK 980 and RÓZSA & BARTA 98). ábra A tokaji Nagy-hegy és a bodrogszegi Cigány-hegy területén piroxén-dácit és piroxén-andezit k zeteinek szemcseösszetételi-szöveti típusai (RÓZSA & KOZÁK 982 és RÓZSA & BARTA 98 alapján) 30

5 Osváth, R. & Csámer, Á.: Volcanomorphological concerns of the Nagy Hill GENERAL GEOMORPHOLOGY <0 micrometer (%) volcanic field 7 8 transition (uncertainty) field subvolcanic field SiO2 (%) Figure 6 Proportion of the groundmass (<0 m) versus silica contents in the samples from Nagy Hill and Cigány Hill 6. ábra Az alapanyag (<0 m) aránya a SiO 2 tartalom függvényében nagy-hegyi és cigány-hegyi k zetmintákban Conclusions According to the most recent studies both large dacite bodies in the southern end of the Tokaj Mountains can be regarded as volcanic centre. In the case of the Nagy Hill this opinion is supported by geological observation and remote sensing data. The Cigány Hill, however, has not been listed as a volcanic centre by former remote sensing observations. Several grain-size distribution data of the rocks from the Cigány Hill are available. In the groundmass (< 0 m) versus silica diagram they essentially belong to the volcanic field, i.e. grain-size distribution data of the rocks suggest that similarly to the Nagy Hill also the Cigány Hill can be regarded as a Miocene volcanic eruption centre. References BALOGH K. (ed.) 966: Magyarázó a Magyarország es földtani térképsorozatához. M-3-Sátoraljaújhely. Publication of the Geological Institute of Hungary, Budapest, 99 p. BEUDANT, F.S. 822: Voyage minéralogique et géologique en Hongrie, pendant l année 88. Paris CZAKÓ T. 973: Légifényképek földtani értelmezésének folyamata és szerepe a Cserhát és a Börzsöny hegység térképezésénél. Annual Report of the Geological Institute of Hungary on the year 97, 2 28 FEGYVÁRI T., HORVÁTH J., ZELENKA T. 990: A paleovulkáni szerkezetek a Tokaji-hegységben r- és légifénykép alapján. Földtani Kutatás, 33(3), 23 2 FÖLDVÁRI A. 92: Jelentés az M. Kir. Földtani Intézet Igazgatóságának rendelete értelmében Sima, Erd bénye és Szegilong között az 937. évben végzett kaolin kutatásról. Annual Report of the Geological Institute of Hungary on the year 97, GYARMATI P. 977: A Tokaji-hegység intermedier vulkanizmusa. Geological Institute of Hungary yearbook, 8, Budapest, 9 p. + mellékletek HORVÁTH, J., FEGYVÁRI, T. ZELENKA, T. 989: Paleovolcanic structures in the North-Tokaj mountains interpreted on the basis of satellite imagery and aerial photography. Acta Geologica Hungarica, 32( 2), KOZÁK M., PUSKÁS-H GYES I., RÓZSA P. 980: A Tokaji- Nagyhegy k zeteinek genetikai és k zetfizikai vizsgálata. Épít anyag, 32, 8 KOZÁK M., RÓZSA P. 982: A Tokaji-Nagyhegy földtani fejl déstörténete és morfogenetikai vázlata. Acta Geographica ac Geologica et Meteorologica Debrecina, 20, KUBINYI F. 8: A Hegyalja földismei tekintetben. Yearbook of the Hungarian Scientific Association, (80-2), 6, MOLNÁR J. 96: A Tokaji-hegység déli részének szerkezeti felépítése. Annual Report of the Geological Institute of Hungary on the year 96, MÁTYÁS E. 978: A bodrogszegi kaolinos nemesagyagel fordulás földtani-teleptani jellemzése. Bányászati és Kohászati Lapok Bányászat,, PÉCSKAY Z., BALOGH K., SZÉKY-FUX V., GYARMATI P. 987: A Tokaji-hegység miocén vulkánosságának K/Ar kronológiája, Földtani Közlöny, 7 p. RÓZSA P., KOZÁK M. 982: A tokaji-nagyhegyi dacittípusok k zettani viszonyai. Acta Geographica ac Geologica et Meteorologica Debrecina, 20, 9 2 RÓZSA P., BARTA I. 98: A Bodrogszegi Cigány-hegy és környéke intermedier vulkanitjai. Acta Geographica ac Geologica et Meteorologica Debrecina, 23, RÓZSA P., PAPP L. 988: Tokaji-hegységi vulkáni és szubvulkáni k zetek elkülönítése szemcsenagysági összetételük alapján. Földtani Közlöny, 8, RÓZSA, P., PAPP, L. 996: A diagram for distinction between calc-alkalic volcanic and hypabyssal rocks. Theophrastus. Contributions to Advanced Studies in Geology I SIMKÓ GY. 926: A Tokaji-Nagyhegy (Kopasz) és vidékének földrajzi morfológiája. Publication of the Tisza István Scientific Association, II. kötet, 7. füzet, Debrecen 6 p. SZABÓ J. 866: Tokaj-Hegyalja és környékének földtani viszonyai. Mathematikai és Természettudományi Közlemények,, SZABÓ J. 89: Típuskeveredés a Tokaj-hegyalján. In: Típuskeveredések a dunai trachytcsoportban. Földtani Közlöny, 2, 7 72 SZÉKY-FUX V., BALOGH K., SZAKÁLL S. 98: A Tokajihegység intermedier és bázisos vulkánosságának kora és id tartama K/Ar vizsgálatok tükrében. Földtani Közlöny,, 3 23 SZLABÓCZKY P. 970: Tarcali k bányák kutatási terve. Manuscript, Geological Institute of Hungary SZLABÓCZKY P. 97: Földtani jelentés és készletszámítás a Tarcal I, II, III. k bányák felderít fúrású kutatásáról. Manuscript, Geological Institute of Hungary SZLABÓCZKY P. 97: Északk Tarcal III dácitbánya el készít részletes fázisú kutatásának jelentése. Manuscript, Geological Institute of Hungary SZLABÓCZKY P. 2006: Természeti értékek a Tokaj- Zempléni-hegység felhagyott k bányáiban. Folia Hist. Nat. Musei Matraensis, 30, SZÖ R, GY., BARTA, I., RÓZSA, P. 999: "Geochemical" concerns of Townson's Travels in Hungary. In Rózsa 3

6 ACTA GGM DEBRECINA Geology, Geomorphology, Physical Geography Series Vol P. (ed): Robert Townson magyarországi utazásai Robert Townson's travels in Hungary. Kossuth University Press, Debrecen, 9 7 TOWNSON, R. 797: Travels in Hungary in the year 793. London. ZELENKA T. 2000: A Tokaji-hegység vulkáni szerkezeteinek távérzékeléses ( r- és légifotó) vizsgálatai. Földtani Kutatás, 37(),