Glacier outburst floods threat

Glaciers can influence societies in their catchment area in different ways, they act as a water storage for dry summers, but glaciers can also trigger geological catastrophes and endanger people.

Glacier outburst floods (GOF) refer to the rapid and sudden discharge of water from within a glacier or from an ice-dammed lake, within minutes to hours a flood wave occurs possibly damaging infrastructures and killing people kilometres away from the glacier which initiated the disaster. In the Alps and North America most outburst floods occur in summertime when during melt-season large quantities of water can accumulate inside the glacier or as ice-dammed lake.

In the Andes and the Himalaya also a second type of floods is common, outbursts from moraine-dammed lakes, referred as glacial lake outburst flood (GLOF).
The area between the moraine and the retreating glacier can be filled with the melt-water, and as the glacier continues to shrink the lake continues to grow. Various processes can lead to the failure of a moraine dam, waves and currents of the lake can erode the dam, ice contained in the dam can melt, the detritus forming the dam can settle with time and so lowering the effective height of the dam.

Fig.1. Laguna Paron (4.140m a.s.l. Cordillera Blanca - Peru, foto from Wikipedia) in 2009, a lake dammed by the debris-mantled glacier Hatunraju with a capacity of 75 million cubic metres before the lake level was lowered by 20 meters artificially by tunnelling through bedrock on the left of the moraine dam. The lake is surrounded by moraines 250m high. It is unknown how stable the moraine of Hatunraju is, if this dam fails a flood of around 50 million cubic metres could sweep downstream and severely damage the town of Caraz, 16 kilometres away.
The worst glacial lake outburst in historic time was caused by the failure of such a moraine-dam in Peru. December 3. 1941 the town of Huaraz was partially destroyed by a flood that killed 60.000 people.

Floods resulting from moraine-dam failure have been increasing in frequency in the Himalaya over the past 70 years or so, although in terms of loss of life they have been by accident much less disastrous then in the Andes.
One of the best-documented outburst floods in Nepal took place on 4. August 1985 when the terminus of the Langmoche Glacier in the Khumbu Himal collapsed into Dig Tsho glacial lake (Video), creating a displacement wave hat overtopped the moraine dam and triggered its collapse. Estimated 10 million cubic metres of water were released - the wave destroyed a power plant and five people were killed and eroded and destabilized the valley floor for 90 kilometres downstream.

This case triggered major research projects of potential dangerous glaciers and glacial lakes, until 2004 more then 20 potentially dangerous lakes in Nepal and 24 in Bhutan were identified, one of the most impressive and dangerous case was lake Tsho Rolpa (4.450m a.s.l.), fed by the Trakarding Glacier. By 2002 the lake was 3,5 kilometres long, 0,5 kilometres width and 135m deep, with an estimated volume of 110 million cubic metres. The moraine damming the lake up was 150m high, with a core of decaying ice.
Emergency measures were initiated with the installation of an early-warning system to detect downstream travelling a flood-wave and later by the construction of an artificial spillway, lowering the lake by 4 metres.
However these are considered only temporary solutions, as a lowering of the lake level by at lest 15 to 20 metres is necessary to prevent spillover or failure of the dam crest, a costly procedure in this region.

This last case shows also the financial problems facing poor countries, often disaster prevention or mitigation are limited by the available resources, and considering the continuing glacier retreat expected in the next decades the increase of problematic lakes (both in number and volume) will by of major concern in the future.

Fig.2. The glacierized Himalayan border region of Bhutan (bottom) and Tibet (top) seen in a satellite image. From the crest of the mountain range clean glaciers flow northwards onto the Tibetan Plateau, while debris-mantled glaciers flow south into densely forested valleys.
At bottom right are a series of moraine-dammed lakes and incipient lakes, formed by the rapid coalescence of supraglacial ponds. The large lake at the very right is lake Luggye Tsho. A breach of the dam in 1994 led to severe flooding and loss of life up to 200 kilometres downstream. (ASTER-image by NASA, 08 June 2006).

Bibliography:

HAMBREY, M. & ALEAN, J.(2004): Glaciers. 2nd ed. Cambridge University Press: 377
HORSTMANN, B. (2004): Glacial Lake Outburst Floods in Nepal and Switzerland. New Threats Due to Climatic Change. Germanwatch - Bundesministerium für wirtschaftliche Zusammenarbeit und Entwicklung.
KALTENBORN, B. P., NELLEMANN, C., VISTNESS, I. I. (Eds) (2010): High mountain glaciers and climate change - Challenges to human livelihoods and adaptation. United Nations Environment Programme, GRID-Arendal.

The discovery of the ruins of ice

"It has already been said, that no small part of the present work refers to the nature and phenomena of glaciers. It may be well, therefore, before proceeding to details, to explain a little the state of our present knowledge respecting these great ice-masses, which are objects of a kind to interest even those who know them only from description, whilst those who have actually witnessed their wonderfully striking and grand characteristics can hardly need an inducement to enter into some inquiry respecting their nature and origin."

James, D. Forbes (1900): "Travels Trough the Alps." [page 17]

Fig.1. C. Wolf and M. Descourtis "La Grosse Pierre Sur Le Glacier de Vorderaar Canton de Berne Province d'Oberhasli", Amsterdam 1785.

Today worldwide glaciers were studied and monitored as climate proxies, and the recent measurements show that almost all of them are retreating fast. The story about glaciers, their influence on the landscape and their possible use to reconstruct and monitor climate is an intriguing one, with many triumphs, setbacks and changes of mind.

For centuries, if not even millennia, the high altitude belt of mountain ranges were a region visited and travelled by man, however also haunted and forbidding places. The glaciers, masses of ice enclosing peaks and extending their tongues into valleys, were considered the residence of mountain spirits, then during the medieval times the prison of damned souls (the Italian poet Dante Alighieri 1265-1321 imagined the centre of hell as a frozen wasteland) and the playground of demons, who from time to time send avalanches and debris flows into the valley.
Despite these myths there was some early insights of what glaciers actually really are made, the Greek historian and geographer Strabo (63 - 23) describes a voyages trough the Alps during the reign of Augustus and mentions

"…there is no protection against the large quantities of snow falling, and that form the most superficial layers of a glacier…[]. It's a common knowledge that a glacier is composed by many different layers lying horizontally, as the snow when falling and accumulating becomes hard and crystallises...[]."

However the knowledge got lost, and was only rediscovered during the Renaissance. Leonardo da Vinci´s (1452-1519) is considered one of the greatest Renaissance-geniuses, he studied anatomy, biology and geology, however regarding the glaciers of the Alps his ideas were somehow confused, the thought glaciers were formed by not melted hail accumulating through the summer. But soon the study of nature experiences an incredible raise, and glaciers find place in various descriptions of travelling scholars.

Between 1538 and 1548 glaciers were labelled (even if not depicted) with the term "Gletscher" on topographic maps of Switzerland. In his account on the Swiss land the Theologian Josias Simler in 1574 describes the Rhone-glacier.
The first historic depiction of a glacier is considered the watercolour-paint of the Vernagtferner in the Ötztaler Alps from 1601. The Vernagtferner was a glacier that repeatedly dammed up the Rofen-lake (named after the Rofen-valley), which outbursts caused heavy damage and loss of property, particularly in the years 1600, 1678, 1680, 1773, 1845, 1847 and 1848.
In 1642 the Swiss editor Matthaeus Merian the Older in his "Topographie Helvetiae, Rhaetiae et Valesiae" published various copper engravings of glaciers, and in 1706 Johann Heinrich Hottinger is interested to explain the motion of "the mountains of ice" in his "Descriptio Montium Glacialium Helveticorum."
Johann Jakob Scheuchzer, visiting in the year 1705 the Rhône Glacier, published his observations of the "true nature of the springs of the river Rhône" in the opus "Itinera per Helvetiae alpinas regiones facta annis 1702-1711", and confirms the idea that glaciers are formed by the accumulation of snow and they move and flow.

Fig.2. The description of the Rhone glacier according to Scheuchzer´s "Itinera per Helvetiae alpinas regiones facta annis 1702-1711", the engraving shows the "false springs at the mountain Furca" (M, N, O - left and right of the picture) and the "true springs" (J, K, L) coming from the snout of the "great glacier" (A-F), surrounded by the "small glacier" (G, H).

The increasing interest to study glaciers in the Alps is also encouraged by enthusiastic travel reports; in his "Voyage pittoresque aux glaciers" the A.C. Bordier of 1773 describes the Bosson glacier as a "huge marble ruins of a devastated city".
The naturalist Horace Benedict de Saussure (1740-1799) is fascinated by the mountains of his homeland, he climbed mountains around Geneva since 1758, and after 1760 he travelled more than 14 times trough the Alps (considering the possibilities in this time an extraordinary achievement). Between 1767 to 1779 the first volume of his "Voyages dans les Alpes" is published, were he reassumes his observations and theories about the visited glaciers, he recognized moraines and large boulders as the debris accumulated by the glacier tongue and proposes to map them to interfere the former extent of glaciers. Despite this exact statement, de Saussure failed to connect large boulders found in the foreland of the mountains to the glaciers of the Alps. He assumed that these rocks were transported on their recent locations by an immense flood. That seemed to explain why most of the boulders found scattered around the plains of Germany came in first place from the regions of Scandinavia, where the same lithology where found in the crystalline continental basement, like Precambrian metamorphic rocks and paleozoic sediments. The theory worked lesser to explain the foreland Alpine rocks - to transport boulders from the Alps the flood at least had to reach 1000 of meters.
The idea of a flood as the explanation for "glacial" deposits became largely accepted, it seemed to fit the description of the biblical flood; even Lyell and Darwin assumed that huge erratic boulders were transported by swimming ice drafts on top of a flood wave.
That glaciers could propagate far out of their valleys was however not an unusual idea for local inhabitants, who observed and experienced the growth and recess of glaciers. In academic circle this approach was a little more difficult.
A contest thought to demonstrate the former extension of Swiss glaciers initiated by the Swiss pastor Jakob Samuel Wyttenbach in 1781 (maybe inspired be the advance of the Alpine glacier in 1770) didn't arise any interest.

"Could it be proven to ourselves on the available documentation that both by the progress of our ice mountains as by our misbehaviour once for pasture most suitable land is currently covered by ice…[]"

There were only careful speculations considering a former expansion of glacier: the geologists James Hutton (1726-1797) and his friend John Playfair (1748-1819) speculated about glaciations of the northern hemisphere. In 1826 a publication by the Danish mineralogist and mountain climber Jens Esmark (1763-1839) was translated into English, in this paper Jesmark discussed the possibilities that glaciers where much greater in the past then today. J.D. Forbes and Robert Jameson (who were the geology professors of Charles Darwin at Edinburgh University, Darwin in his autobiography of 1876 remembers "The sole effect they produced on me was the determination never as long as I lived to read a book on Geology or in any way to study the science.") discussed glacial theories during their lectures. And even Buckland, who still in 1831 argued "northern region of the earth seems to have undergone successive changes from heat to cold", in 1837 was converted to Lyell's uniformatism and considered that sudden changes, like an ice age and glacier expansion, simply don't happen in geology.

In 1815 Jean Pierre Perraudin, a chamois hunter in the Val de Bagnes, told to the engineer Ignatz Venetz his theory that the glaciers once covered the entire valley, and Venetz mapped features that made him even recognize that once the entire Swiss was covered by ice. Vernetz´s lecture on the assembly of the Swiss association for natural history in 1829 found little interest, only Jean de Charpentier, director of the salt mine in the city of Bex (Western Swiss), who 14 years earlier had meet and discussed with Perraudin, this time accepted and got interested in this theory.
He begun a detailed mapping project, and in 1834 Charpentier presented again before the Swiss association the results of his investigations, but the flood theory had still much supporter. One of the critics in the public was a former student of Charpentier, named Jean Louis Rodolphe Agassiz, respected palaeontologist by the establishment. Charpentier invited Agassiz to visit the city of Bex and surrounding mountains, and to observe glaciers.
In the following year (1837) Agassiz held an enthusiastic lecture about glaciers, ice ages and ice shields, and in 1840 published a detailed study of modern glaciers, their deposits and their spurs in his "Etudes sur les glaciers."
Agassiz experienced the same scepticism as many other ice-age proponents before.

"I think that you should concentrate your moral and also your pecuniary strength upon this beautiful work on fossil fishes .... In accepting considerable sums from England, you have, so to speak, contracted obligations to be met only by completing a work which will be at once a monument to your own glory and a landmark in the history of science ...[ ]...No more ice, not much of echinoderms, plenty of fish..."
Alexander von Humboldt in a letter to Agassiz on 2. December 1837

However Agassiz had good connections to the most important geologist of his time. Soon he could persuade William Buckland and later Charles Lyell. After that the most respected geologist gets convinced, the rest, as always, is history:

"advice - never try & persuade ye world of a new theory - persuade 2 or 3 of ye tip top men - & ye rest will go with ye stream, as Dr B. did with Sir H. Davy and Dr. Wollaston in case of Kirkdale Cave"
Edward Jackson, about an advice given by his professor Buckland in 1832

Fig.3. Reconstruction of the glacier that filled the valley of St. Amarin (southern Vosges, France), probably the first tentative reconstruction of an ice age glacier - from COLLOMB (1847): "Preuves de l´existence d´anciens glaciers dans les vallées des Vosges."

Agassiz research on the Unteraar-glacier established the foundations of glaciology; he recorded the dimension of the glacier, his velocity and even ventured inside the glacier by passing trough a glacial mill. Soon after 1850 the measurements methods introduced by Agassiz were carried out on various glaciers of the Alps and repeated nearly every year.

Fig.4. The Hintereis-glacier (in the centre of the picture), Hochjoch-glacier (left) and the Kesselwand- glacier, drawing by Schmetzer 1891, the Hintereis-glacier is one of the glacier with the longest active monitoring program, values about his length change reach back to 1848, since then the glacier lost 3km of his tongue.
"Aus den tiroler Alpen: Der Abschluß des Oetzthales mit dem Hochjochgletscher (links), dem Hintereisferner (in der Mitte) und dem Kesselwandferner (rechts oben). Nach der Natur gezeichnet von K. Schmetzer (1891)."

These records showed various fluctuations, but from 1850 onward a general trend of recession of glaciers in the Alps is observable. This trend has experienced a strong increase in the last 50 years, causing concern for the fast change in the landscape, the destabilisation of the rock walls once supported by the melting glaciers and the alteration of the discharge and hydrology of mountain ranges.

Fig.5. Temperature rise in the Alps and length loss of the glaciers of the Ötztaler Alps (western Austria) in the period 1900-2010. The valley glaciers with their tongues extending in the valleys showed the strongest retreat and degradation of the studied Austrian glaciers.

Landslide of Leisach (Austria)

A landslide near the village of Leisach (East-Tyrol, Austria;46°48`36`` N / 12°45`02`` E), occured in the night between the 19. and 20. february, has dammed up the river Drau and buried the street and trainrails between Italy and Austria. The landslide is 100m wide and 10m thick.
I´m expecting more to come in the next weeks and months...

Fig.1. Foto/Copyright: Robert Gutwenger Lienz (source)

Maierato landslide-aftermath

Fig.1. The Maierato-landslide today. LINK and LINK2

Landslide in Calabria

Landslide in Calabria (South-Italy), town of Maierato (38°42`29``N 16°11`33``E) - 15.02.2010:

UPDATE 17.02.2010: Video of landslide-aftermath

UPDATE 16.02.2010: Mass evacuation of all 2.300 inhabitants of Maierato, a town in the province of Vibo Valentia: an entire side of the mountain which is located near the town collapsed yesterday morning and caused a huge landslide. The landslide - says the mayor Sergio Rizzo - threatens an important part of town and we have unfavourable weather conditions, so we decided not to risk. The first 300 people were evacuated from their homes yesterday evening, but this morning began the evacuation of the entire town. Rainy weather and resulting mass wasting has caused problems also in other parts of Calabria and Sicily.

Fig.2. Carta Geologica della Calabria Foglio 241 1:25.000 (click to enlarge)

The landslide developed in Pliocene-Miocene marls and argillaceous deposits, and showed first signs of reactivation 10 days ago.

Fig.1. Extract of the geological map of Maierato, by Dr. E. Bonino. M= Miocene, P= Pliocene, d= recent deposits. Area of landslide red contour. See also this WebGIS application.

UPDATE: Map of MAIERATO with preliminary risk zonation and delimination of landslides

VIDEO (16.10.2010)

VIDEO released 15.02.2010:

debris flow calendar

The past weekend strong rainfalls caused various debris flows in my near surrounding area, with significant damages and one roadmen missing after a debris flow hit the street he was clearing from detritus.

To understand where and when these events hit is vital for appropriate response tactics and risk evaluation for urban areas. Thereby, the frequency and magnitude of debris flow events are of especial interest, also in view of climate change and human impact.
Information for past debris flow events in historic time can be obtained by studying archives or contemporaneous eyewitness reports/images. Prehistoric events can be reconstructed by 14C-dating of buried soils, dendrochronolgy or lichenometry. The disadvantage of these approaches is their limited time span and coarse resolution.

In the bottom sediments of the lake of Braies, in the Dolomite Alps, another possible long term record was, and still is, studied (IRMLER 2003; IRMLER et al. 2006). The lake Braies is an alpine lake on 1.492m a.s.l. with a maximum area of nearly 36ha and a catchment area of 30 square kilometres. It is surrounded by mountains up to 2.800m, dominated by dolo- and limestone formations. Several debris flow cones extend from the slopes of the mountains to the southern and eastern shores of lake Braies.

View to south with the main debris flow cones entering the lake Braies.

Simplified geological map of the lake and surrounding area (after IRMLER 2003).

In thin sections recovered from cores taken from the bottom lake sediments between annual laminations several "event layers", representing debris flows, were recognised.
Entering the lake, the debris flow brought more fine sediments in the lake then the average sedimentation rate of some millimetres per year. Under the microscope graduated layers, with progressive fining upward sequence, from well-sorted fine to middle sand at the base to silt and clay on the top could be recognized. Load casts and flame like structures support reconstructed rapid deposition. These structures indicate that the sediment moved as underflow (hyperpycnal flow - density current) into the lake basin.
A second category of layers lacked the above mentionetd characteristics, nevertheless these layers show a graduation and are much thicker than the surrounding lamination - up to seven times. These sediments are interpreted as deposits of overflow currents (hypopycnal or homopycnal flow).

Example of the studied core with recognizable annual lamination (from IRMLER 2003).

Erosive contact between annual lamination and a debris flow layer. The base of a debris flow layer is usually very coarse and the single grains more or less the same size.
Photo C) and D) shows so-called "flame structures" and small grooves - caused by the erosion of a debris flow event (Picture size ca 3.9 mm), from IRMLER 2003.

With this approach a debris flow calendar for the last 2250 years could be reconstructed. (IRMLER et al. 2006). During this time the recurrence interval of debris flows varies between 1 and 127 years. At an average of every 16 years a debris flow was deposited. The comparison with climatic phases, from the "Medieval Warm Period" to the "Little Ice Age" showed no significant correlation of events in the catchment area of lake Braies with climatic phases.
The study shows that lake sediments represent a good archive for reconstructing debris flows. In doing so, the record provides the possibility of estimation from the past the threat posed by natural hazards and gives important data for future hazard prediction assessment.

References:

IRMLER, R.; DAUT, G. & MÄUSBACHER, R. (2006): A debris flow calendar derived from sediments of lake Lago di Braies (N. Italy). Geomorphology 77:69-78
IRMLER (2003): Seesedimente als natürliches Archiv zur Erstellung eines Murkalenders am Beispiel des Pragser Wildsees (Norditalien). Ph.D. Thesis, University of Jena, Germany.

Glacier Erosion

Forms of glacial erosion represent some of the most widely distributed and recognizable indicators for past glacier extent. The discovery that polished rock surfaces were formed trough glacier abrasion, and the subsequent mapping of this feature on valley floors very distant from recent glaciers, was vital for the support of the "glacial theory" in the mid-1800s by the geological community.

The glacial striations of Le Landeron on Lake Biel, visited by the participants of the excursion of the Société Géologique in 1838, in a representation of Agassiz's work Etudes sur les glaciers of 1840.

Abrasion is the process of (frictional) wear, produced by surface rubbing against each other, and is achieved in the subglacial environment by sliding of debris-charged ice across the rock-bed.
Roches moutonées are the classical example of subglacial bedrock erosion, with abrasion dominating on the upstream (stoss) side and plucking (material pull off) on the lee side. This results in a highly unsymmetrical form, with a plain, upward side and a step to vertical termination.


To be continued...

Geologists Who Say "Nye"

Roches moutonnées of the last glacial maximum seen by the "Geotope Fischbach" (Bavaria) with Nye channels (after a British physicist) - subglacial channels eroded by meltwater under high pressure in the limestone formation of the "Wettersteinkalk".

In warm-based glaciers, also called temperate glaciers - with the bottom near or slightly above the freezing temperature, water flows in or on the bottom of the glacier forming subglacial streams in channels, that finally join at the snout, forming a glacier outlet.

There are three types of subglacial channels, depending on such factors like glacier movement, bedrock topography and lithology:

N-channel or Nye-channel: incised in the underlying bedrock.

R-channel or Röthlisberger-channel: incised in the ice (and so not found in "fossil" form).

C-channel or Clarke-channel: partly incised in the bedrock and ice, a combination of the formerly mentioned types.

Ecce Homo!

The site of Bilzingsleben is located on the northern bordere of the Thruringian basin, today on a small mound in the middle of pastures, fields and villages.
370.000 years ago in contrast it was the bottom of a valley with springs located on the border of the slopes, feeding creeks that flowed in a lake. Only thousand of years of erosion have switched the topography, eroding softer rocks and letting over only hard lithologies, like the calcareous tufas that remain from this past world.

Fossils of the interglacial period of the Holsteinian can found principally in tufa sands, deposited originally on an alluvial fan and the shore of the ancient lake. This deposition is extremely rich on bones of mammals, and as distinctive feature skull fragments, teeth’s and stone tools of Homo erectus.

The incredible concentration of bones seduced some authors to interpret this site as hunt and butcher-place of the early man. They also saw in the accumulation of stones and bones signs of “fundaments” of huts – at least three of them. But this interpretation is not widely accepted, new excavations and observations on the site showed that the “fundaments” and the “flagged floor” are distributed in a range of 1m of the geologic column, not on a single horizon. Also the position of bones, attribute to human butchering, is straight north-south trending, a clue that provides more for fluvial, rather than anthropogenic induced orientation.

This reinterpretation has maybe also important repercussions on the theory of early man as great hunter, forcing the pleistocene megafauna to extinction.

Silex - artefact from the site of Ehringsdorf (ca. 200.000y) by (presumably by Homo neanderthalensis), showing that central Europe was inhabitat by man for more then 400.000 years.

Our geological heritage

A new geo-journal dedicated to and about protecting geotopes - “GeoHeritage” – the first issue is free for evaluating purpose.

One of the artciles features the pale mountains :
“The Geomorphodiversity of the Dolomites (Italy): A Key of Geoheritage Assessment“

The Ehringsdorf-Formation: or travertine trouble

Even if the first descriptions of the travertine* deposits from Weimar can be traced back to J.C.W.Voigt (1781), and later Goethe draw the first stratigraphic section, only in the years after 1965 they were studied intensively and with modern methods.

STEINER (1983) described three facies in the travertine body, that in 2007 was defined as Ehringsdorf-Formation.

Spring near or marginal facies: characterized by a low topographic gradient and slow running water. In the developing shallow ponds Chara “lawn” developed and fine chalk sand or lake marls were deposited

Slope facies: strong topographic gradient with riffle-pool sequence, the water flows fast and loosing his dissolved carbonate deposits compact travertine layers, the calcification of organic material is very strong.

Valley facies: the slope changes in the broad alluvial plain of the Paleo – Ilm River, the travertine interfingers with loamy and pebbly river sediments. Then follows an alternation of lake marls, an travertine with imprints of reed.

The three-dimensional standard section of the Pleistocene travertine near Weimar is distinguished by three facies ranges following one after another in the direction of the flow of the karst spring waters which are characterized by characteristics or type rocks showing typical structural marks. From the results of the investigation the conclusion is that other occurrences of travertine probably have a similar facial, and, by this, stratigraphically complicated division. This must be taken in consideration much more than until now in all further discussions of stratigraphic questions, also in the discussion of the dating and the absolute age and coordination of paleontological finds in geological sections.

Idealized cross section trough the travertine deposits of Ehringsdorf (after STEINER 1979). White= travertine, black= "Pariser". Notable the coal bearing horizonts in the lower travertine, showing human presence.

The age of the travertine of Ehringsdorf is highly controversial. The position between sediments deposited in cold environments (the fluvial conglomerate represents a braided river system, the uppermost loess layers show ice wedges and cryoturbation) let conclude an interglacial age.

The faunal assemblage supports in part an interglacial position, with the upper part belonging to the Eemian (ca. 130.000y), and the lower part, or at least the base, dating back much further to an Intrasaalian age (OIS7 - 200.000y). The presence of Cricetus major in the soil of the Pariser seems in part to support an Eemian or older date for the upper part of the formation. The malacology on the other side seems to support older ages for both travertine bodies, typical Eemian species are lacking.
The study of human "Präneanderthalian"artefacts, with wedge like utensils and scrapers/spires showed similarities with artefacts found in Eemian to early Würmian (or in this case better Weichsel) ages sites.

The radiometric dating in 2000 using the U/Th method resulted in ages of 236+-13ka for the lower, and 198+-10ka BP for the upper travertine. Unfortunately these results are not universally accepted, the travertine is not a closed system, and water can easily enter the rock and falsifying the isotopic composition.

So still the age remains a trouble.

References:

KATZSCHMANN (2007): The Ehringsdorf Formation. In LithoLex [Online-Datenbank]. Hannover: BGR. Last updated 30.11.2007. [cited 20.06.2009]. Record No. 1000002

*Unfortunately the term “travertine” is somehow vague in different languages. Travertine limestone in English is referred to form around hot springs or by inorganic processes. Calcareous tufa forms by precipitation of calcium carbonate from “cool” springs and river waters, also improved by organic processes. To remain as near as possible to the meaning and use of the word “Travertin” in German, where the distinction is not so clear, here also travertine is used in sense of calcareous tufa.