Mountains as only witnesses

Like islands in the sea small hills, only some dozen meters in height, rises from the flat landscape of the "Orla-valley" south of Weimar. These “mountains” consists of limestone of ancient reefs, growing once in the Permian "Zechstein - sea". Tectonic and erosion have done they dirty work since them, leaving behind only isolated “Zeugenberge” (rude translated in Witnesses mountains) from the marine deposits.

The archeological site "Gamsenberg".

In a flat landscape every vantage point, that enables a hunter to overlook a vast territory, is of strategic importance. And in fact during the last ice age early man observed from this Zeugenberge the glacial steppe in search for the big herds of mammals.

Today the summits of these hills are mostly flat, covered by dense shrubby vegetation, and the surrounding landscape is characterized by villages, fields and scattered trees.
During excavations in a depression on the summit of the “Gamsenberg” – presumably in a karst depression or a collapsed cave - underlying 1,5m thick Loess deposits from the last glacial, a fossil soil was discovered, that contained lithic artefacts, bone fragments and charcoal. This paleosoil developed under warm climatic conditions on rubble of the underlying limestone, this rubble also shows cryoturbation.

The stratigraphic section of the archeological site "Gamsenberg". The upper part consists of Loess deposits, that overlay periglacial displaced rubble and rock fragments (cryoturbation).

Dating of glacial loess samples resulted in ages between 44.700+-4.500 and 41.900+-4.600 years. Between this stratigraphic layer and the horizon with the artefacts bones of micro mammals were found, especially the remains of pika (Ochotona) and lemming (Lemmini) indicate dry, cold conditions. Dating of the layer with the artefacts gave an age of 52.500 to 70.900 years, the bone fragments in this layer belong to animals like elk (Alces), horse (Equus hydruntinus and taubachensis), stag (Cervus elaphus), deer (Capreolus capreolus), auerochs (Bos) or bison (Bison) and a undetermined proboscidean (Mammuthus ?).
This animal assemblage is indicative for a dry, continental to boreal climate, with a mosaic of tree spots and steppe areas. The paleobotanic remains are also indicative to a climate with warm summers, but an annual average temperature to low to permit the establishment of deciduous tree forests.

The only time period that coincide with the radiometric ages, and also with a change between warm to cold climate temperatures, like indicated by the sedimentological and paleontological evidences, is the Odderade interstadial between 70 to 60kyrs during the Weichsel ice age.

Humans, presumably Neanderthals, used the Zeugenberge as ideal vantage point to overlook the steppe with sparse wood spots during an interstadial of the last glacial period. Here they prepared their tools, using rocks like flintstone (found in morainic deposits 20 kilometres away), quartz, greywacke and siliceous schist. After spotting a herd of animals, and (hopefully) successful hunt, they returned and butchered their prey on this site. Then, during full glacial conditions some 50.000 years ago wind transported dust covered the abandoned site, and only today, the karst fissures return their hidden secrets.

References:

WEBER, T. (1996): Das Paläolithikum und das Mesolithikum in Mitteldeutschland. Archäologie in sachsen-Anhalt Nr.6. Archäologische Gesellschaft in Sachsen-Anhalt, Halle

Dating cave sediments

The decay chains between radioactive and a series of daughter isotopes is a useful tool to date sediments and rocks.

The radioactive decay process of uranium (238U and 235U) and thorium (in the form of either 230Th or 232Th) were investigated in 1938, but only in the 1950s and 1960s the method was applied to date lacustrine carbonates, marine sediments, corals and cave calcite deposits.

Thorium is a daughter product in the 238U decay chain. This element is much less soluble in water than uranium and is not found in groundwater, thus, speleothems (including flowstones, stalagmites and stalactites) formed in caves as a result of precipitation of calcium carbonate from aqueous solutions, will show an uranium-, but no thorium content. Thorium will be produced only as the uranium isotopes decay with time, providing a dating tool for such materials in the age range for some 100ka.

Speleothems are well suited for this dating method because their calcite crystals are usually large and have little tendency to recrystallize after deposition, forming so a "closed" system, where no contamination can "enter", and no information can "escape".
When viewed in cross section many speleothems display a prominent laminated structure (growth layers), caused by variation of the deposition conditions and so the deposited material (p.e. amount of fluid inclusions or organic matter).

The growth of speleothems depends not only from the presence of water, but also of it’s content of dissolved CO2. Before percolating through the bedrock, surface water is exposed first to atmospheric CO2 and then to soil gases enriched in biogenic CO2, from where most dissolved CO2 in groundwater comes.

The stratigraphy of the Conturines cave was recorded during the excavations conducted from 1988 to 1990, from 1996 to 1998 and in 2001. As excavation site the first encountered area with the scattered bones and skulls, where the small conduit opens in the much larger main hall of the cave – denominated conveniently “hall of skulls”- was chosen. The floor of the upper parts of the cave is covered by up to 2m thick flowstone that shows a fine lamination, maybe representing annual cycles.


It is overlain in turn by sand, fossiliferous dolomitic sand, again sand without fossil and finally large blocks.
The presence of such thick flowstone implies, that there were abundant precipitation and conditions favourable to develop soil horizons and vegetation cover in the catchment area of the cave. This limits the period of flowstone genesis to an interglacial or a warm interstadial period.
The fossils of cave bear are found only in the sand overlying the flowstones, implying that this deposit is younger. Cave bears were herbiverous animals, but today vegetation can found only 1.000m lower. During the occupation of the cave by the cave bear, vegetation was aviable in immediate vicinity, this also let´s assume that this deposits represents another warm period, with a shrub- and treebelt extending much higher then today.

So at least we need two periods were the temperatures reached higher values then today on this site – this was the case during the interglacials of the Eemian (130 to 120kyr) and the Holstein (350-300kyr). The comparation of the anatomical features of the Conturines bear with other high alpine extinct bear species seemed to confirm an minimal age between 65.000 to 30.000 years, implying a hypotetical warm and icefree period just before the glacial maximum 20.000 years ago.

So it is possible by the stratigraphy and the evolution “niveau” of the bear fossils to restrict the sedimentation phase in the cave to a period between 300kyr and 30.000 years ago.

It’s notable that the radiometric dating method confirmed in part this hypothesis. The dates of the flowstone samples resulted beyond the range of dating of 350kyr by the thorium - uranium method. The bone-bearing sands are much younger, the two oldest dates obtained by dating the bones are 87+-5kyr and 108+-8/-7kyr. Similar to the flowstone dates, the C14 method applied to the bones resulted in an age older then 39.000 years - beyond the limit of this method.
Even if this shifts the possible ages for the first sedimentation phase considerably to older ones, the flowstone still could be deposited during, or slightly before the Holstein, or – and this would be very exceptional, during the Cromer interglacial (800kyr).
Then a sedimentation phase follows, with the deposition of grey, yellow and red sand, containing no fossils, overlaid by the fossil bearing sand and rubble layer. The radiometric results seems to confirm an age for the occupation of the cave by the bear during, or just after the Eemian.
Then erosion removes and reworks in part the fossiliferous sandy layers – channels forms, which later were refilled with an grey sandy material, again lacking fossils.

This example shows how the limitations of the different dating methods can be compensated in part by careful observations and the “strengths” of other methods, and many different results are needed to reconstruct the sedimentation history in a "restricted" environments like caves.


References:

SCHWARCZ, H. Speleothems. In (ed): ELIAS, S.A. (2006): Encyclopedia of quaternary science. Elsevier : 290-300
SPÖTL et al.(2006): The last and the Penultimate Interglacial as Recorded by Speleothems From a Climatically Sensitive High-Elevation Cave Site in the Alps. In SIROCKO, F. et al. (ed): The climate of past interglacial. Developments in Quaternary Science 7.

Cave bear Cave

From the old things and old times I have heard, and I will now tell.

In August 1987 the fossil and mineral collector Willy Costamoling was exploring the area of the Conturines Mountains in the South Tyrolean Dolomites.

The Conturines mountains, the name derives from the ladinic language "con turrines", meaning "with towers". Especially the south wall of the migthy dolomite mountain are structured by numerous cliff towers.

The "Piz Taibun" (on the right), and "Piz dles Conturines" (on the left), surrounding the glacial excavated cirque of "the cave".

He was looking for calcareous concretions that form in dolomitic sands and rubble deposited in caves and fissures, denominated, after a valley where they are usual found and their sometimes unusual form “Travenanzes dolls”. Ascending to the “Piz Taibun” - a secondary summit of Conturines, he noted a cave at the very end of a glacial carved cirque.

The entrance of the cave at the end of the glacial cirque...

... and the very first meters inside it.

He decided to try his luck, and return with appropriate tools to explore the cave. On September 23. finally he stood in more then 2.700m altitude before the 5m high, and 10m broad portal. Behind the entrance a vast, empty cavity, at the first glance only some meters deep and then delimited by a rock wall, but then - on the left side a dark passage seemed to go further inside the mountain. Here the darkness, illuminated only by the headlamp, and large boulders on the cave bottom made it difficult to proceed. After 160m, and a height difference of 60m, the conduit seemed to open in a larger hall. At the entrance of this underground hall – like an old guardian- stood a bulky stalagmite.

"The guardian".


Behind it the cave bottom was covered by smooth flowstones and dolomitic sand, and scattered around … bones, a lot of large bones. The discoverer attributed them first to a recent bear, only after he showed some teeth that he brought back home to a other collector they realized that the bones were from the extinct cave bear.
And if this discovery seemed not surprisingly enough, at the very end of this mountain hall stood, some meters high, an impressing, beautiful cascade of stalagmites and stalactites.

After a legendery, secret and long lost treasure, consisting of a precious stone hidden deep inside the Dolomite mountains, it was called "Raetia" :

Introducing the cave bear

On October 22 of the year 1794 a young German medicine student submitted his “dissertatio” to the philosophical faculty of the University Leipzig. In this work, the 23 year old Johann Christian Rosenmüller described a well preserved skull of a bear discovered in a cave near the village of Burggaillenreuth in the Franconian Alb (Central Germany). Caves and fossil bones are widespread in this region, already in 1774 the german priest Johann Friedrich Esper (1732 – 1781) , recognising that the bones do not belong to a brown bear, claims – missing other material to compare - that they represent remains of a polar bear. In the following years other authors agree that the fossils can not attributed to known bear species, but only Rosenmüller describe this “unknown creature” as a new species – and because of the rich discoveries in caves – he names it “cave bear” Ursus spelaeus ROSENMÜLLER 1794.

The illustration of the holotype - skull for the species Ursus spelaeus in the work of ROSENMÜLLER 1795 from the “Zoolithenhöhle” near Burggaillenreuth (Franconian Alb). The specimen today is lost.

In 1795 Rosenmüller, after supplementary studies, publish a second description and confirmation for the new established species. He also rejects the contemporary speculations about the genesis of the bone accumulations as result of a flood catastrophe, and propose simply a slow, but consistent accumulation and deposition trough animals dying by natural causes inside the caves:

„Wir können das Dasein einer solchen Menge fossiler Knochen nicht leichter erklären, als wenn wir annehmen … daß die Tiere, von denen sie sind, in denen Höhlen gelebt, sich daselbst fortgepflanzt haben und drinnen größtenteils gestorben sind” (We can easily explain the existence of such a quantity of fossil bones, as if we assume that the animals, from which they come, have lived in those caves, have reproduced in them and have finally also died inside them).
ROSENMÜLLER 1795

250 years later the Cave bear is one of the best studied mammals of the ice age, and among others one of the best known by a broader audience. This results surely by the large number of bones found of this animal, and also the location of the remains in caves, where it maybe influenced the legends of “cave occuping dragons”.

Arnold Böcklin (1827 - 1901).

References:

ROSENMÜLLER, J.C. (1794): Quaedam de ossibus fossilibus animalis cuiusdam, historiam eius et cognitionem accuratiorem illustrantia, dissertation, quam 22. Octob. 1794 ad disputandum proposuit Ioannes Christ. Rosenmüller Heßberg-Francus, LL.AA.M. in Theatro anatomico Lipsiensi Prosector assumto socio Io. Chr. Aug. Heinroth Lips. Med. Stud. Cum tabula aenea. O.V. Leipzig
ROSENMÜLLER, J.C. (1795): Beiträge zur Geschichte und näheren Kenntniß fossiler Knochen. Georg Emil Beer. Leipzig

Fissures, holes and caves II

Bone accumulations in caves were known since antiquity – Greek sailors tell that they found the bones of Cyclops in caves on the island of Sicily. Some centuries later, the German Jesuit Athanasius Kircher visited and studied this bones, and in 1678 he published an extensive report , the “Mundus subterraneus”, on this matter, proclaiming that the remains represent at least the bones of four different kind (and sizes) of prehistoric giants. Only more centuries later the fossils were recognised to belonging to Pleistocene elephants.

In the 18th and 19th century the bones were mostly attributed to belong to victims of the biblical flood – this idea also should explained the transport and the deposition in caves of the remains.
Until 1970 bone accumulations – recognised as fossils – were mostly attributed to human activity, even if earlier observations showed how carnivores can gather and process bones in similar way as expected for human behaviour.

I have had an opportunity of seeing a Cape hyaena at Oxford...I was enabled also to observe the animal´s mode of proceeding in the destruction of bones: the shin bone of an ox being presented to this hyaena, he began to bite off with his molar teeth large fragments from its upper extremity, and swallowed them whole as fast as they were broken off. On his reaching the medullary cavity, the bone split into angular fragments...he went on cracking it till he had extracted all the marrow... this done, he left untouched the lower condyle, which contains no marrow, and is very hard. The state and form of this residuary fragment are precisely like those of similar bones at Kirkdale; the marks of teeth on it are very few...these few, however, entirely resemble the impressions we find on the bones of Kirkdale; the small splinters also in form and size, and manner of fracture, are not distinguishable from the fossil ones...there is absolutely no difference between them, except in point of age.
BUCKLAND 1823 Reliquiae Diluvianae, or, Observations on the Organic Remains attesting the Action of a Universal Deluge

The modern (re)interpretation of fossil bearing sites let conclude that the interaction between prehistoric humans and animals is complex and an ever-changing one. In the locality of Zhoukoudian (China) 42 hominid skeletal elements were found, 28 of them showing hyenid tooth marks – gnawing, biting, chewing, punctures, even regurgitation. On the other side, rhinoceros bones at the same locality show no activity by predators, but display cut marks – implying that early paleolithic humans are both predator/scavengers and preys. Nevertheless it is assumed that during later time periods humans become active and successful hunters, and lesser prey.

Fissures that act as sediment and also bone accumulation traps can develop not only in carbonates, but also in evaporitic sediments. Near the small village of Westeregeln (Thuringia, Germany) past quarrying activity for clay has exposed underlying Mesozoic gypsum and limestone formations, which in the upper part show an intensive “karst” network, refilled with Pleistocene sediments and fossils.


The uppermost part of the stratigraphic column of the infilling sediments is represented by a postglacial soil, developed on Loess – aeolian sediment deposited during the last great glacial period. These sediments cover ancient matrix supported breccias, presumably generated by partial collapse of former caves or fissures. Between these breccias, mostly on the top of the deposits, lithic artefacts, bones of ice age mammals and hyena coprolites are found exclusively in pebbly horizons.


Remarkable is - by a preliminary result - a human rib enclosed, how it seems, in a hyena coprolite. From the hyena were also discovered at least ten skulls, attributed to the ice age hyena Pachycrocuta brevirostris.

The site is still under examinations, so it is not clear if the apparent simultaneous presence in one layer of lithic artefacts/ humans bones and hyena bones mean also coexistence during the same time of this two species. Also the possible engulfed human bone can be explained by hyenas actively hunting humans, scavenging human remains, or simply -as artefact of the disturbed startigraphy and subsequent diagenesis.

The site of Westeregeln is interesting also for another “kind of fissures”. In red clays, colluvial material derived from the weathering of underlying sandstones, during the last glacial maximum an extensive ice wedge net developed. After the ice that created this wedges melted, the remaining fissure was filled by Loess. Today these ice wedges casts are easily eroding, and reveal not only loam and sand, but also lithic artefacts, that thousand of years ago felt into the open cracks and were “accumulated” and preserved trough time.


References:

BOYLE (2007): Vertebrate studies: Interactions with Hominids. In: (ed.) ELIAS: Encyclopaedia of Quaternary Science. Elsevier

Fissures, holes and caves

Most extensive cavity networks occur in water soluble lithology, like carbonatic or evaporitic formations, but smaller fissures and gorges can develop also by mechanical erosion or physical degradation of the underground, for example melting of ice (thermokarst).

Fissures can gather animals’ remains over a certain time interval simply by animals falling and/or remaining entrapped inside, and being otherwise inaccessible the bones are also protected from scavengers.

An important site of this type is represented by Pirro Nord, situated in a quarry at the north-western margin of the Gargano promontory, close to the village of Apricena in the italian province Apulia.

Here in sediments filling an extensive karst network, discovered during quarrying of limestone, a very diverse and now well-documented fossil vertebrate assemblage was discovered. This sediments returned also lithic artifacts, estimated in an interval between 1,3 and 1,7 Ma, documenting an early hominin occurrence in the older part of the Early Pleistocene, and thus now constitute the oldest record in Europe.
The karst network developed during two phases. The first, Miocene in age, extents in the mesozoic limestone of the „Sannicandro Formation“ (Cretaceous), and consists of red clays (terra rossa) in part reworked and redeposited with a hughe diversity of vertebrates remains assigned to the „Mikrotia-Fauna“, after a an endemic rodent genus.
The second phase of karst development occurred after a tectonic uplift of the Gargano peninsula during the Pliocene, extending in formerly deposited Pliocene sediments and protruding in the Sannicandro Formation. Fissures can also show in the lower part fossils attributed to the Mikrotia – Fauna, and in the upper parts of the Villafranchian mammal age (Upper Pliocene and Lower Pleistocene, 3.6–1.2 Ma ago).

The stratigraphic succession of the Apricena horst in the „Cava Passalacqua”, as seen in the vast quarry dominating the landscape near Apricena. In the lower part the quarried Mesozoic limestone’s of the “Sannicandro Formation”, truncated by Miocene red clays and karst infillings of the “Terre rosse”, covered by the yellow Pliocene deposits of the “Lago di Varano Formation” and finally sandstones of the “Serracapriola Formation”.

Detail of the “Sannicandro Formation” with extensive karst network development.

Balanus sp. occurrence in the Pliocene cover units.

The accumulation of large mammals has been due the infall or entrapment of carcasses within the wider cavities, and by subsequent transport within the karst network when it was flooded. The occurrence of a number of articulated skeletons is suggestive of accumulation of carcasses also without transport.

Karst fissure with extensive infill of red, sandy clays - "Terra Rossa", and also bones:
A teeth of Deinogaleryx, an giant hedgehog...

...and Hoplitomeryx, an endemic Miocene artiodactyl.

The abundance of bones and coprolites of Pachycrocuta brevirostris, as well as the occurrence of numerous gnawing and bite marks on fossil bones, suggests that this giant hyaenid species played an important role in local bone accumulation.

The Pirro Nord fauna mammal fauna is uncommonly diverse, until now 20 species of amphibians and reptiles, 47 species of birds and over 40 mammal species were described, some of them though to be endemic to the Gargano.
The nature of the landscape of the „catchment area“ of the ancient caves 2 Ma ago can be inferred from the composition of it´s vertebrate assemblage. The occurrence of perissodactyls, cheetah, large sized porcupine, abundant vole of the genus Allophaiomys and presence of bird species of the families Otidae, Pteroclidae and Alaudidae are all suggestive of open landscape with a basically arid climate.

Mandible with teeth from a Pleistocene bat.

References:
ARZARELLO et al. (2007): Evidence of earliest human occurrence in Europe: the site of Pirro Nord (Southern Italy). Naturwissenschaften 94: 107-112
PAVIA & ZUNINO (2009): Giornate di paleontologia IX edizione Apricena (FG), 28-31 Maggio 2009 – Guida alle escursioni 30 e 31 maggio 2009.

See part II

Alpine tundra

Saponaria pumila (Caryophyllaceae)

Loiseleuria procumbens (fruit) (Ericaceae)

Sphagnum (rubellum / magellanicum ?)