FASCICULI INSTITUTI GEOLOGICI HUNGARIAE AD ILLUSTRANDAM NOTIONEM GEOLOGICAM ET PALAEONTOLOGICAM GEOLOGICA HUNGARICA SERIES GEOLOGICA TOMUS 26 Mio/Pliocene Phreatomagmatic Volcanism in the Western Pannonian Basin by Ulrike Martin and Károly Németh BUDAPEST, 2004 © Copyright Geological Institute of Hungary (Magyar Állami Földtani Intézet), 2004 All rights reserved! Minden jog fenntartva! Serial editor: TAMÁS BUDAI Revised by Chapter 1 — GÁBOR BADA (Vrieje Universität, Amsterdam, Netherland) and CSABA SZABÓ (Eötvös University, Budapest, Hungary) Chapter 2 — FERENC MOLNÁR (Eötvös University, Budapest, Hungary) Chapter 3 — MURRAY M. MCCLINTOCK (Otago University, Dunedin, New Zealand) and KURT GOTH (Landesamt für Umwelt und Geologie, Freiberg, Germany) Chapter 4 — JAMES D. L. WHITE (Otago University, Dunedin, New Zealand) Chapter 5 — IAN SKILLING (Pittsburgh University, Pittsburgh, Massachusetts) General revision by: VOLKER LORENZ (Würzburg University, Germany) TAMÁS BUDAI (Geological Institute of Hungary, Budapest) Technical editor: OLGA PIROS DEZSÕ SIMONYI DTP: OLGA PIROS, DEZSÕ SIMONYI Cover design: DEZSÕ SIMONYI Digital Map Production Assistance: GÁBOR CSILLAG (Geological Institute of Hungary, Budapest) and ÁKOS NÉMETH (Hungarian Meterological Service, Budapest) Published by the Geological Institute of Hungary — Kiadja a Magyar Állami Földtani Intézet Responsible editor: KÁROLY BREZSNYÁNSZKY Director HU ISSN 0367–4150 ISBN 963 671 238 7 Geologica Hungarica series Geologica Tomus 26. 3 Contents Preface of Volker Lorenz . 5 Volcanology and its importance in Hungary (Károly Brezsnyánszky) . 7 Introduction . 9 Chapter 1 Phreatomagmatic volcanic fields in a Mio/Pliocene fluvio-lacustrine basin, western Pannonian Basin, . Hungary: a review . 11 Colour Plates . 49 Chapter 2 Late Miocene to Pliocene palaeogeomorphology of the western Pannonian Basin based on studies of volcanic erosion remnants of small-volume intraplate volcanoes . 57 Colour plates . 69 Chapter 3 Mio/Pliocene phreatomagmatic volcanism in the Bakony – Balaton Highland Volcanic Field, Hungary . 73 Colour plates . 109 Chapter 4 Shallow sub-surface intrusive processes associated with phreatomagmatic volcanism north of the Keszthely Mountains, Hungary . 133 Colour plates . 141 Chapter 5 Mio/Pliocene phreatomagmatic volcanism in the Little Hungarian Plain Volcanic Field (Hungary) and at the western margin of the Pannonian Basin (Austria, Slovenia) . .153 Colour plates . 173 Chapter 6 Concluding remarks . 185 Colour plate . 191 Geologica Hungarica series Geologica Tomus 26. Preface On the occasion of the Second International Maar Conference held in Hungary in September 2004, the Geologica Hungarica, series Geologica presents this monograph on the Mio/Pliocene (8- 2 My) small volume intraplate alkaline volcanism in the western Pannonian Basin. The volcanic activ- ity occurred in the Bakony – Balaton Highland Volcanic Field (BBHVF) just north of Lake Balaton, in the smaller Little Hungarian Plain Volcanic Field (LHPVF) just to the north, and in the Styrian Basin Volcanic Field barely reaching into westernmost Hungary. The western Pannonian Basin is underlain by Neogene siliciclastic sediments which overlie Mesozoic karstic limestones which in turn overlie crystalline basement rocks. As volcanism was active during and after deposition of the Neogene sili- ciclastic sediments, volcanicity was largely synsedimentary and consequently effected, more or less, by the unconsolidated water saturated sediments. The volcanic fields of the western Pannonian Basin will be visited during two identical volcanological field trips run prior and after the conference. In this monograph the present state of physical volcanological research (over the last 10 years) on the volcanism of the western Pannonian Basin is presented. The authors of the several papers present the relevant details and interpretations of the regional geology, of the volcanic fields and also of the many individual volcanoes and their various phreatomagmatic and magmatic eruption styles. In addition, the authors compare the western Pannonian volcanic fields with other volcanic fields in the world many of which they know from personal aquaintance and studies. The list of ref- erences contains not only very informative Hungarian publications but also a wealth of internation- al publications relevant to the understanding of volcanological processes generating maars, tuff- rings, diatremes, scoria cones, lava lakes and their tephra and volcanic rocks, but also relevant to the understanding of volcanic fields. The overview publications and detailed descriptions of the individual volcanoes of the three vol- canic fields provide the reader with a state of the art view on the volcanicity of the Neogene volcan- ism of the western Pannonian Basin which for many decades has been almost unknown to volca- nologists from many countries. The monograph has been organized in such a way that it contains both the overview publications but also the publications of the individual volcanoes and their out- crops so that the publications can easily be used as field guides for volcanological field trips of groups but also for individuals. The various levels of erosion of the many individual volcanoes make the volcanic fields of the western Pannonian Basin very informative in respect to research of maars, diatremes and lava lakes, and complimentary to other volcanic fields displaying monogenetic volca- noes exposed at different levels of erosion, as, e.g. the maar volcanoes visited on the occasion of the First International Maar Conference in the West Eifel Volcanic Field in 2000. This monograph is also complimentary to the field guide published on the volcanic field in southern Slovakia, also vis- ited prior and after the Second International Maar Conference. Würzburg, 15th of June 2004. PROF. DR. VOLKER LORENZ Institute for Geology University of Würzburg, Würzburg, Germany Geologica Hungarica series Geologica Tomus 26. Volcanology and its importance in Hungary Magmatism and volcanism played an important role in the geological development of Hungary. The formation of acidic rocks due to volcanic activity during the Variscan cycle can be found in the Velence–Balaton and the Mecsek area south-west of Hungary. Typical “Pietra verde” type pyroclas- tic rocks, displaying a distinctively alkaline-trachytic character, are intercalated in the Middle Triassic carbonat sequence in the South Bakony Mts north of Lake Balaton. Middle Triassic to Jurassic basic and ultrabasic suites in different tectonic units of NE Hungary are commonly intercalated with deep- sea sediments. The Tisza Tectonic Megaunite south-east of the Hungary is related to basic-alkaline volcanism in the Early Cretaceous. Volcanic rocks are best exposed in the Mecsek Mts and they extend as far as to the basement of the Great Plain. In the Eocene andesitic-type volcanism occurred both in the Transdanubian Range and the Mecsek Mts. Intermediate volcanism during the Miocene is of particular importance. In Hungary occurrences of Miocene volcanic rocks are distributed in a broad belt from Dunazug–Börzsöny Mts to the Zemplén Mts, basically from Budapest to the north-east tip of Hungary. Furthermore volcanic rocks are covered under thick Neogene to Quaternary sediments in the northern part of the Great Plain, which form all together the innermost zone of the volcanic belt of the Inner Carpathians. Particularly important are metallic ore deposits of Hungary that are associated with this Miocene volcanic belt. The latest volcanic activity, occurred in several regions of Hungary, and has been dated to be of Mio/Pliocene age. One of the most important volcanic regions in relation to the Second International Maar Meeting 2004 is the western Pannonian Basin, also because of the scenic impression of indi- vidual volcanic mountains in the Tapolca Basin, west of the Bakony – Balaton Highland area. Volcanological research in Hungary has of long tradition, first of all because of the old mining of metallic ore deposits related with the Neogene volcanism. Professor József Szabó (1822–1894) is know well in the scientific community as “father of Hungarian geology”, the first teaching geology in Hungarian language at the university. He established an internationally recognized petrographic system of trachytic rocks. For long time after Szabó’s activity the descriptive petrology prevailed in the Hungarian geology. In addition, the contribution of Lajos Lóczy sen. has a great importance. He studied the morpholog- ical development of the Balaton Highland, in particular, the basaltic volcanoes of the Tihany Peninsula. Since the late 1970’s, early 1980’s new trends of volcanological studies are appeared in Hungary, focusing on the Neogene intraplate basalt volcanism. On one hand petrogenetic studies, based on detailed mineralogical, chemical and isotope geochemical investigations, have been car- ried out. On the other hand investigations and new theories tried to support interpretation of tecton- ic, geodynamic position and significance of the volcanism in the geological evolution of the area. A new detailed morphogenetic approach and the theory of phreatomagmatic volcanism con- ducted by Ulrike Martin and Károly Németh gave way to a new view in interpreting basaltic volcan- ism of the western Pannonian Basin. We strongly believe that the IAVCEI–CVS–IAS Second International Maar Conference held in Hungary jointly organised with Slovakia and Germany will pro- mote both the scientific and the educational activity in