Sometimes referred to as the "Prehistoric Pompeii", Ipolytarnóc stores 23-17 million year old fossils. These include the teeth of 24 different species of sharks as well as the teeth of crocodiles and dolphins, an almost 100 m tall petrified pine, more than 15,000 subtropical, exotic leaves and 3,000 animal footprints of 11 species. This is one of the world's richest complex fossil footprint find site. The fossils can be viewed thanks to a volcanic catastrophe which buried a whole subtropical jungle under volcanic ash, thus preserving them. The site became protected in 1944 and is managed by the Directorate of the Bükk National Park. It is worth visiting because of the fossils and their high-tech interpretation. As a new development, the Site became the main gateway to the world's second transborder geopark, the Novohrad-Nógrád Geopark, in 2010.
The reworked shoreline sandstone layers of the 23 Ma old sea sediments bear a very rich marine fauna. The so-called "shark toothbearing beds" contain, besides shark teeth, a mixture of bones from rays, dolphins, manatees and crocodilians. After the 1903 description of Koch, the "Ipolytarnóc shark tooth-bearing bed" became the characteristic marker bed of the Eggenburgian stage of the Lower Miocene in the Central Paratethys. The original fauna as described more than 100 years ago was revised recently based on new finds. The result shows a very diverse Lower Miocene shark community that includes 19 genera with 16 certain species.
The giant petrified tree trunk, 42 m long, that bridged a stream of the Borokas ravine was exposed at the beginning of the 19th century. Its discovery initiated the scientific research of the site. The first scientific research activities and excavations began in 1836, led by Ferenc Kubinyi. Later investigations demonstrated that a whole forest was destroyed by the volcanism, the trees were toppled on top of the paleosurface by the nearby volcanic blast. Most of the tree remains are embedded at the sandstone-tuff transition, under the plinian ash fall unit. A detailed analysis of the petrified tree trunks revealed that the 20 Ma old rainforest held at least 7 coniferous, 4 deciduous and 1 palm species.
A recent paleobotanical study identified 64 taxa among the large collection of macrofloral remains, based on a sample of nearly 15 thousand leaves (Hably, 1985). The assemblage is dominated by laurophyllous plants, indicative of a vegetation in a warm and humid, subtropical climate. Most of the abundant plant remains are in the basal part of the rhyolite tuff, but 27 plant species have been identified from leaf imprints on the palaeosurface (footprint sandstone), too.
Abundant and well-preserved fossil vertebrate tracks are exposed on the topmost bedding planes of the Miocene river bank sandstone. The preservation of the tracks has been attributed to volcanic activity that instantly covered the paleosurface. It was Hugo Böckh, who, at the base of the giant tree, originally discovered the prehistoric animal footprints in 1900. The original discovery, a 4x4 m slab with footprints was transported to Budapest within a year, where it is still displayed in the Hungarian Geological Institute's (HGI) well-known lecture hall, hence known as "Footprint Hall." In the 1920s, 30's and 60's Ferenc Nopcsa, and later Tasnádi also enriched the Institute's collections by excavating more footprints (Tasnádi, 1976). In the early 1980s, the footprints were mapped during the construction of the first of several facilities built to protect them; 1298 tracks were registered on the site, while the total number reached 1644, together with the specimens in the HGI collections (Kordos, 1985). Explorations in the 1990s doubled the figure of footprints on the site to 2762. The extent of the known area with footprints explored at Ipolytarnóc in the last hundred years exceeds 1500 sq. m. The whole site, which is estimated as being 50-100 times larger than the currently exposed areas and is mostly continuous can only be explored after removing the rhyolite tuff bed. Such exposure of the surface containing the footprints should only be undertaken if they can be preserved from weathering. Therefore, scientific exploration only takes place gradually, and requires subsequent protective measures. Analysis of the footprints started immediately after their discovery, and it was known a hundred years ago that there were tracks of rhinoceroses, ungulates and birds. The first scientific description of the footprints was in 1935, in a book by Othenio Abel (Abel, 1935), who identified footprints of a rhinoceros, a proboscidean, cervids, an ancestral triungulate horse, a large carnivore as well as birds. He illustrated them with photographs. Following the studies of Tasnádi, the "Ipolytarnóc" monograph of Geologica Hungarica series Palaeontologica was issued in 1985, for the Regional Committee on Mediterranean Neogene Stratigraphy (RCMNS) congress, where L. Kordos identified 11 animal species based on all footprints known at the time. The commonest avian species are the medium-sized Ornithotarnocia lambrechti with three toeprints and the similar-sized Tetraorniothopedia tasnadii that left four toeprints behind, while Aviadactyla media is characterized by rod-like, straight toeprints. Tracks of the small songbird Passeripeda ipolyensis are present but not as common as those of the other birds. The most common mammalian footprints include the rounded and three-hooved footprints of adult and juvenile, prehistoric rhinoceroses (Rhinoceripeda tasnadyi) as well as those of smaller (Pecoripeda hamori) and larger (Megapecoripeda miocaenica) ungulates. Numerous carnivores lived here 20 million years ago. Amongst them, the largest footprints belong to the rare Bestiopeda maxima, first illustrated by Abel (1935). Astonishingly fresh-looking and distinct are the three footprints of a single individual of Carnivoripeda nogradensis, the blurry tracks of Bestiopeda tarnocensis, and the clawprints of a peculiar mustelid, Mustelipeda punctata (Kordos, 1985).
Unfortunately, after surviving the volcanic catastrophe and 20 Ma, the fossil finds could not withstand the onslaught of humans. Not just laymen but scientists also caused irretrievable damage to the track and other fossil remains. Devastation already began in the year of discovery of the petrified pine, in 1836. Kubinyi at first thought of ex situ protection. He had the trunk unearthed and dragged out of the ravine by "11 pairs of oxen". The trunk was then broken into pieces, and the number of resulting fragments were then transported to nearby private museums. Later, realizing his mistake, Kubinyi had the remaining exposed parts covered with earth, "lest it fell prey to vandal hands, that are lamentably so common in this country and that let the so-called stonebench come to nothing." Unfortunately, neither Kubinyi's efforts, nor the building, which was erected around 1860 to shelter the most endangered parts of the giant pine, could save the trunk from vandalism. Locals collected fragments of it for building stone and whetstone, swarms of "souvenir collectors" broke pieces from it, local landlords took bigger fragments of it as ornaments for their gardens, and it became a favored material for gravestones. Museums were also frequent visitors and contributed to the damage. Even the protective shelter of the tree was destroyed within two decades after its construction. The shark teeth also attracted the attention of the locals. They imaginatively called them petrified bird tongues and sold them in necklaces to the tourists, who came to visit the wonders of petrified nature. The footprint sandstone proved to be ideal cobble, building stone and was used even for the building of the protective cellar for the fossil tree. Locals held picnics on the eroded surface of the paleosurface and danced on top of the prehistoric footprints. Paleontologists excavated and collected the most exotic tracks, and left the exposed surfaces to weathering and accessible to private collectors. Several tracks were lost, and only sketches of them survive. Those, who cared for the site, stopped publishing papers, because they realized that new discoveries generated a new flow of collectors to the site. The most pro conservation scientists finally decided to stop further excavations, until everything already exposed was sheltered (Tasnádi, 1976). Despite the fact that the site officially became protected in 1944, several decades went by before the protection became effective. Permanent staffing with guided tours along the established geological study trail in the early 1980s was the solution. Excavated areas where tracks were exposed became covered by conservation buildings, and new interpretation trails were opened later. The site has become a favored destination for tourists. Land ownership problems were solved as the area was acquired by the Hungarian state, and the Bükk National Park Directorate (BNPD) gained land manager status; thus the number of factors impeding conservation management was reduced significantly. The site was declared a part of the Pan-European natural heritage by the Council of Europe in 1995. The area is on the tentative list of the world heritage and a European Diploma holding site.
As the scientific and information centre of the Novohrad-Nógrád Geopark, the site provides several programmes for a whole day, including guided tours along its famous geological study trail or world-class 4D movies about the prehistoric past in its Visitor Centre. It is a favourite destination for geotourism, its geological trail was opened to the public in 1986.