Geology museums of mainland Europe: Agios Georgios Cave, Kilkis: 50 years of history – 30,000 years of prehistory
Vassilis Makridis (Greece), Evangelia Tsoukala (Greece), Evangelos Vlachos (Greece), Katerina Tsekoura (Greece), Wilrie van Logchem (The Netherlands) and Dick Mol (The Netherlands)
In northern Greece, 45km north of Thessaloniki, one of the few public caves in Northern Greece is situated in the Agios Georgios Hill, near Kilkis (Figs. 1 and 2). The cave is famous for its stalactites and stalagmites, its cave environment and thousands of fossilised bones. Since 1986, approximately 80,000 people have visited this cave and guided tours are provided by the municipality of Kilkis. During the Late Pleistocene, around 30,000 years ago, this cave used to be a hyena den and remains of Late Pleistocene megafauna have been recovered in the sediments of the cave. These fossils tell a fascinating story about the landscape and its wildlife. In September 2012, a new natural history museum was opened to the public: displaying 50 years of history, and 30,000 years of prehistory.
Introduction
The cave of Kilkis, first described in 1962, developed in an exceptional pattern. It is known among speleologists as a ‘maze cave pattern’. The passages and chambers are developed as a network and are sometimes connected to each other. Maze caves commonly originate from a specific type of speleogenesis. In contrast to the typical karst caves that develop due to dissolution by seeping rain water containing weak carbonic acid, mazes are formed by thermal (hot) water in confined aquifers.
The speleogenesis of the cave of Kilkis took place before the Agios Georgios Hill was formed and when the limestone was located deeper, acting as the host rock for thermal water. Uplifting movements in the region formed the Kilkis Hill and raised the cave to a higher altitude. It then became dry and several entrances opened through erosion of the hill. Speleothems (see below) were formed in the cave-passages and animals entered or were trapped in the cave chambers or passages (Fig. 4).
The deposition of calcium carbonate in caves often creates exciting formations, known as speleothems. Kilkis cave shows a great variety, such as stalactites hanging from the ceiling and stalagmites building up from the cave floor. On closer inspection of the cave walls, one can find even more impressive structures – eccentrites and heliktites that have formed in every direction. The cave is also famous because of the great variety of cave corals – so-called “cave popcorn” – found everywhere on the cave walls (Figs. 5 and 6).
In a cave where regular public tours are conducted, destruction of speleothems is common. This is caused by construction work, the use of artificial lights and the thousands of visitors entering the cave. These activities also distort the balance of the cave’s microclimate. In Kilkis, due to the sensitive microclimate, the number of visitors entering the cave is controlled. Therefore, the speleothems have remained in excellent condition.
During the Late Pleistocene, some 30,000 years ago, the Agios Georgios Cave was a prominent feature in the landscape. It was, among others, used by hyenas as a den and the activities of this animal have resulted in several accumulations of remains of Late Pleistocene faunal elements.
During the past year, a permanent exhibition has been completed at the site. With the help of the Municipality of Kilkis, the upper floor of the old coffee shop on the top of Agios Georgios Hill, close to the cave, has been transformed into a display of the history of Kilkis. No, it is not just a collection of old petrified bones, but a bilingual exhibition of modern design, giving the visitor an overview of the cave’s history, and the work of speleologists and palaeontologists, thereby reconstructing the past in an attractive and easily understood way. The museum has been open to the public since 6 September 2012.
Pleistocene wildlife
During the Pleistocene, 2.58 million to about 10,000 years ago, the world looked completely different from today. The area of Kilkis was a dangerous area and wildlife was characterised by carnivores, such as hyenas, foxes and other animals.
Carnivores feed on other animals (primarily herbivores) and are therefore characterised by sharp teeth. The caves have played an important role in preserving their remains. Inside a cave, there are ideal conditions for fossilisation. Carnivores used caves for protection from extreme weather, for hibernation, and to nest and protect their offspring. In most caves in Europe, the cave bear is the most widely prevalent carnivore, with an excellent fossil record. They are followed by the cave hyena and finally, the felids, such as the cave lion and the European jaguar.
The cave at Kilkis was used as a den by hyenas (see the boxes, The cave hyena and Coprolites: fossilised dung). Hyena bones and their teeth of all ontogenetic stages have been discovered there. Their fossils tell a story about the extinct hyena in Europe, and their associated fauna and environment. They eventually became extinct towards the end of the Pleistocene.
The cave hyena
The cave hyena, Crocuta crocuta spelaea (Fig. p), is one of the best known predators of the Pleistocene. Its name derives from Greek word ‘krokos’ (Latin ‘crocus’) meaning “saffron crocus”, which was a common source of yellow dye in ancient times. The hyena originated in Asia and its range was widespread. Its remains can be found in caves all over Europe. Pleistocene Eurasian hyenas weighed up to 100kg, with a shoulder height of one meter, and they used caves as dens over a period of thousands of years.
Hyenas are specialised carrion feeders, able to crack large bones to get at the nutritious marrow and spongy bone tissues. As an adaptation for this way of life, their cheek teeth have evolved into powerful, conical structures. The leftovers from a hyena meal are easily recognisable – their molars will leave characteristic grooves and bite marks on the bones (Fig. 10). Above all, hyenas are hunters and scavengers of carrion; and they made an essential contribution to the reconstruction of ecosystems.
During the Late Pleistocene in northern Europe, hyenas also hunted large hoofed mammals. As a result, they play an important role as a bone collector, which benefits the fossil record. Although a hyena will mutilate the bones, it always leaves the teeth intact and, systematically, they are the most important part of the skeleton. Therefore, the activities of hyenas in caves have been of great importance for our knowledge of bone accumulations and Pleistocene fauna.
Coprolites: fossilised dung
Cave hyenas fed on carcasses and did not just devour the soft tissues (meat, skin and tendons), but also the bones. Therefore, the characteristic that most often distinguishes the coprolites of hyenas from coprolites of other carnivores is their chemical composition and mineralogy, due to the very high bone content in the hyena diet (Fig. 11). The coprolites are largely composed of apatite, which is a complex mineral form of calcium phosphate, indicating digestion of all the organic constituents of the bone, leaving only the inorganic fraction in a reconstituted form. This high inorganic content makes the coprolites extremely durable, which is undoubtedly a factor in their preservation in the fossil record (Larkin et al., 2000 and Lewis, 2011).
Hyenas were also feeding on vegetation like plants, seeds and fruits. In addition, it is known that they fed on the intestines of their prey containing the remains of vegetation. The tough remains of the plants, like pollen, can be easily preserved in their droppings. These droppings, particularly in caves, are often well preserved. Hyena droppings are very characteristic and can easily be distinguished from those of other carnivores. Analyses of these fossil droppings provide valuable information, which is useful for reconstructing the palaeoenvironment in which these animals lived.
More mammals
From the cave at Kilkis, other carnivores are represented by fossilised bones and teeth. A lower jaw with dentition has been identified as belonging to the robust polecat (Mustela putorius robusta). This mustelid animal was quite rare and, so far, the discovery in the cave is the only one in Greece.
For some of the fossil record from the cave of Kilkis, it is unclear what its geological age is. This is true for a smaller cat, but also for non-carnivores, like leporids (for example, rabbits and hares) and some bird remains.
Bovids
The extinct species, Bos primigenius (aurochs), was very robust, with a height at the shoulders of two meters, and was three meters in length. It was widespread in Europe, Asia and northern Africa and is well known from the cave art of Palaeolithic man, who depicted the animal in many rock paintings and rock engravings. Bulls are often depicted in black and the cows in red. Apparently, the colour of the fur in females was a reddish brown and the bulls were much darker. Theauroch was probably a grassland or open woodland animal. This indicates the dominance of a mild climate and probably open woodland environment.
Aurochs derive from Bos planifronsand are considered to be the ancestor of domestic cattle (Bos taurus). True Bos primigenius survived in Europe until 1627. The last European record, a female individual, died in the Jaktorow Forest in Poland. The skull is in the collection of the Royal Armoury Museum, Stockholm in Sweden.
Skeletal remains of the aurochs found in the Kilkis cave show a lot of gnaw marks caused by hyenas, indicating that these predators were feeding on this large bovid.
Deer
During the Pleistocene, the area of Kilkis was a sort of paradise for deer. Two species of deer have been recovered from the cave – the extinct giant deer (Megaloceros giganteus), with a shoulder height of over two meters, and the smaller red deer (Cervus elaphus). The latter still exists and is common in Europe.
The skeletal parts of these two artiodactyls (even-toed ungulates) can be distinguished from each other. Those from the giant deer are much larger than those from the red deer. In both species, only males developed large branching antlers, shedding them every year. The antlers of the giant deer could span more than three meters. For that reason, the giant deer must have been adapted to open environments. The dentition of its molars shows that the animal was a mixed feeder, feeding on grasses, but also leaves and twigs of shrubs and trees. The giant deer survived the Pleistocene and finally became extinct around 8,000 years ago in Russia.
Remains of red deer can be found in Late Pleistocene sediments all over Europe, indicating that the animal was an animal common in the landscape. Like most cervids, it was adapted to forested areas and, like the giant deer, it is a mixed feeder. Fossil remains of red deer have been found in many localities in Greece. It survived the dramatic climate changes at the end of the Pleistocene and was successful throughout the entire Holocene.
Horses
Horses belong to an Order known as Perissodactyla (odd-toed ungulates), which all share hoofed feet and an odd number of toes on each foot, as well as mobile upper lips and a similar cheek tooth structure. The perissodactyls originally arose in the Late Palaeocene (about 55mya). This group of animals appears to have been originally specialised for life in tropical forests, while modern horses are adapted to life on drier land, in the much harsher climatic conditions of the steppes. Other species of Equus are adapted to a variety of intermediate conditions (see box, The extinct wild ass).
The early ancestors of the modern horse walked on several spread-out toes, an accommodation to life spent walking on the soft, moist grounds of primeval forests. As grass species began to appear and flourish, the equids’ diets shifted from foliage to grasses, leading to larger and more durable teeth. At the same time as the steppes began to appear, the horse’s predecessors needed to be capable of greater speeds to outrun predators. This was attained through evolving longer limbs and the raising of some toes from the ground, in such a way that the weight of the body was gradually placed on one of the longest toes – the third.
The extinct wild ass
The European wild ass (Equus hydruntinus) is a distinct, horse-like species, somewhat intermediate between the Asiatic wild ass (Equus hemionus)and true donkeys(Equus asinus), more closely related to the former (Fig. 12). Τhe limb bones are slender, resembling those of Asiatic asses, and the ‘microdont’ teeth are lightly built and are of the same type as in the African forms (Fig. 13). This is an extinct species of equid whose cursorial (adapted specifically to run) body proportions suggest an adaptation to semi-arid conditions.
The European wild ass was a member of the so-called ‘Mammoth Fauna’, roaming the cold, dry steppes of the Late Pleistocene. Skeletal remains, which are rare, are easily distinguishable from other horse species. It finally became extinct at the end of the Pleistocene.
The Kilkis wild ass material is considered to be among the best preserved in Europe, which contributes to our knowledge of the biology and the appearance of this animal. Hundreds of thousands of remains of Late Pleistocene wild horses have been trawled from the seabed of the North Sea between the British Isles and The Netherlands. Less than 50 specimens, mainly metacarpal and metatarsal bones, have been attributed, based on their slender and long morphology, to the European wild ass. In contrast to Kilkis Cave, these animals were not very common in north-western Europe.
Absolute age
Absolute dating can tell us about the age of the fossil bones and teeth. Samples of dental elements of the cave hyena and the European wild ass have been radiocarbon dated at three different laboratories. This has resulted in an age of 12,500 BP and 29,349 BP for the cave hyena and 28,530 BP for the European wild ass.
Visit the cave and museum
When visiting northern Greece, we highly recommend a guided tour of the Agios Georgios Cave, which includes a visit to the museum. When entering Kilkis, you are directed by road signs to the cave on the top of Agios Georgios Hill.
Further reading
Bassiakos, J. & Tsoukala, E., 1996. ESR dating suitability of Quaternary fossil remains; a hyaenid tooth example and new data on the fauna from the Agios Georgios Cave, Kilkis (Macedonia).Proceedings of the 2nd Symposium 1993 of the Hellenic Archaeometrical Society: 59-76, Thessaloniki.
Kurtén, B. 1968. Pleistocene mammals of Europe. Aldine Publishers company, Chicago, pp. 1-317.
Larkin, N.R., J. Alexander & M.D. Lewis, 2000. Using experimental studies of recent faecel material to examine hyaena coprolites from the West Runron Freshwater Bed, Norfolk, UK. Journal of Archaeological Science 27: 19-31.
Theodorou, G., 1981-82. The importance of cave fossil fauna. Bull. Soc. Spel. Grèce, 18(1/2): 232-244, Athens.
Tsoukala, E., 1991. Contribution to the study of the Pleistocene fauna of large mammals (Carnivora, Perissodactyla, Artiodactyla) from Petralona cave (Chalkidiki, N. Greece). Preliminary report. – Compte Rendus à l’Académie des Sciences de Paris, 312: 331-336. Note présenté par Yves Coppens.
Tsoukala, E., 1992. The Pleistocene large mammals from the Agios Georgios Cave, Kilkis (Macedonia, N. Greece). Scientific Journal: Geobios, 25 (3): 415-433.
Tsoukala, E., 1992. Quaternary faunas of Greece. Courier Forsch.-Inst. Seckenberg, 153: 79-92, Frankfurt a. M.
Van Asperen, E.N., Stefaniak, K., Proskurnyak, I. & Ridush, B., 2012. Equids from Emine-Bair-Khosar Cave (Crimea, Ukraine): co-occurrence of the stenonid Equus hydruntinus and the caballoid E. ferus latipes based on skull and postcranial remains. Palaeontologia Electronica, 15(1); 5A, 28p; palaeo – electronica.org/content/2012-issue-1-articles/124 -equids-from-emine-bair-khosar.