Managing and Surveying the Geological Garden at Tata (Northern Transdanubia, Hungary)
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The Geological Garden at Tata is an open-air geological museum where a spectacular succession of Tethyan Mesozoic sedimentary rocks, characteristic of the Alpine-Carpathian region, is finely exposed in abandoned quarries and cleaned rock surfaces. In addition to geological values, the area houses copper-age chert mines, the only ones accessible to the wider public in Hungary. Due to financial problems, however, maintenance of the site was more or less confined to mowing for more than 20 years. Renewal of the Geological Garden began in 2015 when large-scale cleaning as well as detailed surveying was carried out. Removing the soil and loose rock debris provided opportunity to study the effects of weathering and growth of vegetation. Near 60 m3 of rock debris and soil had been accumulated on approx. 5000 m2 rock surface over the decades of obligate deterioration. Lower Jurassic marl and Middle Jurassic radiolarite chert beds as well as Middle Jurassic limestones proved to be especially deeply weathered. The cleaning action raised the question whether the sub-horizontal rock surfaces can be conserved for a long time in their present state or not. Lessons drawn from the latter can serve as a basis for future maintenance activities as well as for plans aiming at developing geosites.
KeywordsOpen-air geological museum Geosite maintenance Surveying Peri-Tethyan Mesozoic Prehistoric mining Hungary
Introduction and Historical Background
The territory of Hungary, although characterized by surface rocks and sediments of Neogene and Quaternary age, is relatively rich in scientifically important and/or spectacular geosites representing earlier periods of Earth history, and some of them were given statutory protection long ago. Recently, Horváth and Lóczy (2015) gave a detailed overview about the state of geoconservation in Hungary, with special reference to the history, legal background and organization of geoheritage protection. The Act on Nature Conservation (53/1996), in force since 1996, provides the basis for protection of “geological formations and scientifically important geological exposures as well as of major localities of rare minerals or fossils” (https://net.jogtar.hu/jogszabaly?docid=99600053.TV). Nowadays, the Ministry of Agriculture holds responsibility for nature conservation and maintains a public database of protected geosites, available only in Hungarian. According to it, about three-fourths of the 195 important geological exposures located in areas protected by a specific law, such as national parks, landscape protection areas and nature conservation areas, are Palaeozoic and/or Mesozoic suites (http://www.termeszetvedelem.hu/index.php?pg=menu_2237). Another 88 geosites are protected by a specific law as nature monuments, about 28 of which are also outcrops of pre-Neogene rocks (http://www.termeszetvedelem.hu/orszagos-jelentosegu-egyedi-jogszaballyal-vedett-termeszeti-teruletek). The number of Palaeozoic and Mesozoic exposures located in protected natural areas of local interest is around ten. Abandoned quarries receive less attention than underground mines if their protection and conservation is considered, as a rule (Storemyr 2006). In Hungary, however, they are well represented among protected geosites.
The 1950s of the twentieth century saw a renewed interest in the Mesozoic of the Kálvária Hill, resulting in the comprehensive papers of Fülöp (1954) and Szabó (1961). József Fülöp (1928–1994), an almost plenipotentiary actor in geology from the early 1950s to the end of 1980s, i.e. the time of changing in society in Hungary, had the opportunity to make large rock surfaces clean in order to study Middle and Upper Jurassic rocks that have never been quarried being unsuitable for building. Detailed geological survey carried out by him has lead to the recognition of scientific and educational importance of the Kálvária Hill Mesozoic succession, and a part of the hill was declared to be a nature conservation area in 1958. In the course of geological study, two chert mining pits dug by the Copper Age man in Middle Jurassic radiolarite were discovered in the late 1960s (Fülöp 1973). The pits, now protected by an exhibition building, are the only prehistoric mining sites accessible to visitors in Hungary. In addition to the geological and archaeological exploration, Fülöp intendedly converted the dusty abandoned quarries into a garden in every sense. As a result of this effort, the Geological Garden now houses a wealth of botanical values.
Quarrying came to an end completely in the late 1970s. By this time, the extent of the protected area had increased step-by-step to 3.5 ha and since 1976, it acts as an open-air geological museum, founded by the former Hungarian Geological Institute. The management of the site, now called at full-length “ELTE Tata Geological Garden—Nature Conservation Area and Open-Air Geological Museum”, was taken over by the Eötvös University in 1994. Since then, it functions as a place for public outreach, recreation and teaching. In addition to its educational and cultural importance, the Kálvária Hill holds scientific values and is considered as a geosite sensu Brilha (2016, 2018). Its extent, visibility and accessibility (corresponding to “potential use values” in Beranová et al. 2017) make the Geological Garden one of the most valued Hungarian geosites.
Economic problems related to the democratic transformation in Hungary dramatically influenced the history of the conservation of geosites including that of the Geological Garden. Until 1992, technicians from the Geological Institute cleared away the soil and loose rock pieces as well as plants from the rock surfaces in the summer months. Around 1600 man-hours were needed once in 2 years to keep the area clean. In addition to the termination of this service, budget cuts resulted in the reduction of the staff members from 5 to 2, making maintenance rather difficult. Rocky surfaces became more and more vegetated and covered with loose rock pieces and soil. Reconstruction of the Geological Garden began in 2015 in form of a large-scale cleaning and surveying action. Lessons drawn from the latter, reviewed below, can serve as a basis for future maintenance activities as well as for plans aiming at developing geosites.
Stratigraphy and Significance of the Kálvária Hill Mesozoic Succession
Macro- and microfossils indicate a Rhaetian, i.e. Late Triassic age of it. A wide variety of sedimentary environments ranging from areas exposed sub-aerially at times to lagoons of some metre depth are represented in the succession. Beds deposited in lagoons are the most frequent and contain abundant megalodontid bivalves (Fig. 4), studied in detail by Végh-Neubrandt (1982).
The older part of the Middle Jurassic series, attributed to the Tölgyhát Limestone Formation, is proved to be considerably diverse in facies: red, marly limestone rich in Fe–Mn oxide nodules, crinoidal layers as well as beds containing small-sized bivalve shells in rock-forming quantity occur. In the second half of the Middle Jurassic, the nature of sedimentation changed fundamentally: accumulation of calcium carbonate was largely replaced by silica-rich deposits now forming the Lókút Radiolarite Formation. The material of the minute siliceous tests of radiolarians was usually dissolved during diagenesis and has been precipitated as chert layers and nodules later exploited by the Late Neolithic men.
The origin of the enigmatic “Oxfordian Breccia” (also known as “Oxfordian Bed”), a widespread member in the Gerecse Jurassic characterized in detail by Fodor and Főzy (2013), is still to be found. According to Fodor and Főzy (2013), it represents most probably a single depositional event, e.g. gravity-driven re-deposition of lime mud. On the other hand, δ13C values usually show a systematic shift through the bed, indicating deposition over an extended period (Price 2013). Higher parts of the Upper Jurassic as well as the lowermost Cretaceous are developed in a thin succession of pelagic limestone. Bedding planes of the condensed Pálihálás Limestone of Kimmeridgian age appear as “ammonite pavements” and are highlights of the Geological Garden. The Jurassic/Cretaceous boundary can be drawn within the Calpionellid-rich Szentivánhegy Limestone. The latter represents the Tithonian, Berriasian and partly Valanginian stages and has been named after the medieval settlement (Szentivánhegy) once located on the Kálvária Hill, that time called Szentiván Hill. Jurassic/Cretaceous boundary beds were studied in detail recently by Szinger et al. (2007) and Tithonian bivalves were described by Szente (2013). Unfortunately, the rich and well-preserved Upper Jurassic ammonite assemblage collected bed-by-bed and studied by Gyula Vigh has remained documented only in form of faunal lists published in Fülöp (1976) until now.
Tata Limestone, once exploited in the “Bluestone Quarry” at the Kálvária Hill, is the youngest known example of the vanished lithofacies “regional encrinite” sensu Ausich (1997), i.e. a crinoidal formation of several tens of meters thickness and several tens of kilometres areal extent, which has no counterpart in modern seas. Type sections of the Szentivánhegy and Tata Limestones have been designated in the “Bluestone Quarry” by Fülöp (1976).
The Cleaning Action of 2015: Observations and Results in Geosite Conservation
In 2014, Eötvös University received a grant of 175,300 € from the European Union in the frame of the programme “Environment and Energy Operational Programme” (Project “Reconstruction of Key Geological Sections at the Tata Nature Conservation Area”). Due to the nature of the administration process related to the project, the work began as late as July of 2015. Thus, largely 2 months was available for the realization of the project instead of the one and a half year originally planned.
In addition to cleaning, representative rock surfaces easily accessible to visitors have been polished and informative boards have been placed. Other results of the renewal include the discovery of a chert mine located outside of the archaeological exhibition building.
The project provided opportunity to renew the drainage system of the archaeological exhibition building as well. Previously, the rainwater accumulated on a large part of the upper cleaned surface was thought to be piped through a tube made of asbestos, laid beneath the ground of the exhibition building. In 2015, the old pipe, presumably cracked, was found to be near completely closed up by an 8-m-long tissue of fine roots. The new pipe bypasses the building and cleaning sockets have also been installed.
Results of the Geodetic Survey
Land registry maps, as plots, buildings, parcel numbers
Orthophoto made in 2013, available at http://www.fentrol.hu/en/
Digital terrain model and contour lines
Fences, buildings, inner roads, most important trees
Important geological objects, such as Triassic/Jurassic boundary
Surprisingly, the surveying resulted in recognition of considerable difference between the extent of the area really occupied by the Geological Garden (3.5 ha) and that indicated by the land registry (2.8 ha). The difference largely lies in the fact that some 0.7 ha, owned by the town, was fenced by the Hungarian Geological Institute in the 1970s. After recognizing this problem, negotiations were initiated between the stakeholders and since then, the municipality of Tata voted to assign the right of management of the area to Eötvös University.
Results of the geodetic survey and 3D scan are the basis of a digital 3D geological model, whose development is in progress. Geological results of the surveying include ascertainment of the structure of the rock mass forming the lower yard of the Geological Garden as well. Triassic/Jurassic boundary can be well identified both in the “Whitestone Quarry” and in the quarry situated in the lower yard. The characteristic points of this boundary were measured in three dimensions, and a regression plane was determined on the measured points using GeoEasy software (Siki 2018). The residuals of this regression plane are at decimetre level, and the parameters of the regression plane fits the one determined by Fülöp (1976), indicating that there is no fault between the quarries mentioned.
Present-Day Activities and Planning for the Future
The last 2 years saw a welcome increase in the number of the staff that makes maintenance much more efficient as compared to the preceding decades. Since 2016, one of the staff members has been working in the frame of the programme “Workfare work in museums”, coordinated by the Hungarian National Museum, and another one is employed by the local community of Tata. Additional to that, since that year, the botanical values of the Geological Garden have been maintained by a gardener expert employed by the University. As a consequence of the work carried out by the staff, long unremembered stairways and paths have been re-conquered from the vegetation since 2016. Two more years seem necessary, however, to clean up the garden entirely. Recently, however, a new gardening problem has arisen. When forming the garden at the lower yard of the Geological Garden in the early 1980s, different trees have been planted in 1 × 1-m pits sunk into Dachstein Limestone using explosives. Some trees have already outgrown their pits and withered. Finding the fittest species and planting them are tasks for the future.
The chert pit discovered in 2015 was excavated in 2017 and 2018, in co-operation with the Hungarian National Museum. The majority of the work was done by the enthusiastic volunteers during the camps organized in the hottest summer weeks by the distinguished archaeologist Katalin Biró-T. The main results of the recent three-year excavation series are three antler tools, reconstructed from chips and deposited in the Neolithic Collection of the Hungarian National Museum (Biró-T et al. 2018).
Although some stratigraphic intervals of the Mesozoic succession of the Kálvária Hill have been studied in very detail in the past, some important questions are still unanswered. The cleaning action served as a good opportunity to collect rock samples from the Middle Jurassic succession whose stratigraphy is poorly known. Identification of the Tithonian bed from which the calcareous alga Clypeina jurassica was mentioned by Szabó (1961) is also a challenge, this tantalizing record being the first-found evidence of photic zone in the Upper Jurassic of the Transdanubian Range.
Maintenance of the newly excavated chert pit as well as the state of the sub-horizontal cleaned rock surfaces raised the question whether they can be conserved for a long time in their present state or not. 3D scanning and filling them seem to be an alternative. In that case, visitors could see the rocks lying beneath their feet using VR glasses.
In the last years, efforts were made by the management of the Geological Garden to obtain financial assistance for building a visitor centre involving a lecture room necessary for developing new geoeducational programmes.
Discussion and Conclusions
As in most countries, geology does not appear as an independent discipline in primary and secondary school curricula in Hungary and is taught in the frame of “Earth and environment”, a subject whose proportion has been reduced in the last decades if the total number of lessons is considered. It is therefore of primary importance to utilize the educational opportunity provided by the elements of the geological heritage. Geosites, if appropriately selected and maintained, offer especially good opportunities to teach geology to students (Meléndez et al. 2007). Abandoned quarries often serve as valuable resources for education (e.g. Macadam and Shail 2002; Stefano and Paolo 2017; Prosser 2019).The Geological Garden well fulfils the criteria of pedagogical geosite and widely used as locale of open-air geological lectures. In the last 4 years, altogether more than 1000 students, corresponding to about 15% of the visitors, learned geology over there.
The Geological Garden of Tata in its renewed form provides visitors a unique opportunity in Hungary to study a spectacular succession of Mesozoic marine sedimentary rocks, as well as prehistoric chert mines, in easily accessible abandoned quarries and other exposures concentrated in a well-groomed garden environment. Keeping rocky surfaces clean, however, would require regular removal of loose rocks, soil and plants. More than 20-year-long pause in this kind of maintenance had resulted in considerable fragmentation of rocky surfaces and lead to the aesthetic deterioration of the Geological Garden. Observations made during the large-scale cleaning action of 2015 clearly indicate that suitably frequent removal of vegetation would be fundamentally important. Obtaining financial assistance to build a visitor centre with a lecture room is another challenging task for the future.
Thanks to Zoltán Varga, keeper of the Geological Garden, for his help and hospitality. Thanks to Dóri Farkas, as well, for taking part in the geodetic survey and preparing an excellent diploma thesis. Constructive comments by Ewa Głowniak and Kevin Page editors as well as by three anonymous referees are also gratefully acknowledged herein. Cleaning and surveying work was supported by KEOP-3.1.2/2F/09-11 project.
Open access funding provided by Eötvös Loránd University (ELTE).
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