World heritage !

The Dolomites on Friday 26.06.2009 were accepted to enter the list of the UNESCO World’s heritage, not only for their natural, but also cultural importance.

The Dolomites played and play a central role for the history of geology and paleontology.

The stratigraphic succession of the Schlern mountain in a book of general geology of 1907.

The area of the Dolomites in the Southern Alps has attracted geologists since the early 19th Century, the vast outcrops and the sudden change of different lithologies – and so sedimentation conditions – was an ideal field for studying sedimentological and also tectonic questions. One of the most important achievements’ was the recognition that the outstanding carbonatic peaks and mountain groups are remains of ancient carbonate platforms and coral reefs. In early days of geology less was known about sedimentation in oceans, only selective probing was possible by dragging samples of the bottom of the sea, and so only in 1842 Darwin formulated a first hypothesis on atoll formation. Influenced by this model, intensive field mapping was carried out, and in 1860 the German geologist Ferdinand von Richthofen (1833-1905) recognised as first the organic origin of the carbonate rocks of the Schlern, in the valley of Fleims and Fassa. In the work of Johann August Edmund von Mojsisovics (1839-1907) “Die Dolomitriffe von Südtirol und Venetien” (1879), where he described the stratigraphic succession of the reef built-up and basin succession, the research on old reefs gave back important impulses to the interpretation of modern reefs.

In Leopold von Buch´s work "Esquisse d´une carte geologique de la parte meridionale du Tyrol" (1822) the author distinguishes carbonatic from dolomitic rocks.

In the map of Edmund Mojsisovics (1878) he distinguishes different formations by various different colors.

The outcrops in the Dolomites also helped to clarify an ongoing quarrel between geologist, proponents of the Plutonism, and geologist, proponents of Neptunism. The questions were if all know rocks have either a pure volcanic origin, or were deposited in an aquatic milieu.
The Italian mining engineer Conte Giuseppe Marzari-Pencati observed in 1806 in the valley of Fassa that granite covered carbonates, so the first has to be originated later. An impossibility for the scientific hypothesis of Neptunism of that time.

Sketch of the outcrop with granitic rocks protruding in calcareous rocks by Marzari-Pencati (1849).

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.

The riddle of the Sphinx, or, what we (still) don´t know about earth

Once, to enter the city of Theben in Greek every traveller had to answer the riddle of the terrible Spinx. However dared to give the wrong answer was engulfed by the terrible demon.

In a survey carried out on 753 scientist from different nations around the globe , the german magazine "Spiegel" asked for the greatest - still unresolved problems in geosciences.

Here the rank list with percent of answers (or questions?) :

No. 1 (20,8%) How can we predict earthquakes?

No. 2 (19,8%) What processes control climate in detail?

No.3. (10,4%) How came life to being?

No. 4 (9,4%) What exactly happens inside earth?

No. 5. (7,3%) How can mankind provide enough green energy for it´s needs?

No. 6. (6,2%) How can we predict volcanic eruptions?

No. 7. (5,2%) Plate tectonics, have we solved all problems?

No. 8. (3,6%) How looked primordial earth?

Algas Rocks!

Spring tufa forms by precipitation of calcium carbonate from supersaturated waters. Supersaturation is mostly attained, or is highest in some distance downstream the emergence of the spring or within streams in areas of rapids or water falls. The most important factor for tufa formation is degassing of carbon dioxide, so the water reaches the necessary degree of supersaturation for precipitation of calcium carbonate. Degassing can be achieved by physical processes, like highly turbulent flowing water, or biological processes, by presence of vegetation or microorganisms.

Riffle-pool sequence, the water flows fast and loosing his dissolved carbonate deposits tufa layers, the calcification of organic debris is very strong.

Rivularia sp. encrusting a tufa coated boulder.

Plants or autotrophic organisms, especially very small ones, like algae, can influence the hydrochemistry by changing the amount of dissolved carbon dioxide by their metabolism.

Also secreted extracellular substances, for example by Cyanobacteria, common in creeks and ponds, can profoundly modify the shape of crystallized calcium carbonate. Microbial induced tufa is widespread and can comprise the major part of total carbonate volume found in the surroundings of a spring.

Near “Teufelskanzel” – a small spring in a carbonatic catchement examined in 2006 - especially on the rock wall rigth of two small waterfalls modern tufa precipitation takes place. On the left side of the waterfall the scarp is overgrown by the moss species Eucladium verticillatum and Cratoneuretum sp., in contrast on the rigth part of the scarp, an algae mat was established.


In Tab.1 the found algae are listed following a transsect that stretches from the vicinity of the waterfall to the distant, respectively from to wet to dry: Locations 1 and 2 are located directly under the waterfalls, number 3 is influenced by spume of the waterfall and number 4 is already dry. Under wet conditions Phormidium incrustans and P. autumnale were quite common. In sample 2 Leptolyngbia perforans was recognised, in the green layer, incrusting the moss tufa. Also Chamaesiphon rostafinski was found attached to a Pseudoscytonema.


The observed algae mats, growing on 1,5 – 2,5 mm thick tufa layers are approximately 1000 μm thick layers, composed of Scytonema sp., Petalonema sp. and Crooccocales, including rhombohedral shaped cristales. The aerophilic Gloeocapsa rupestris and also Nostoc sp. were found under dry conditions in the algal mat.


In microscopic mounts of the algae mat, two types of cristal structures were observed in contact/related to the algae species Scytonema sp.:

(1) Rhombohedric (euhedral = with cristal faces) single cristals. Some of them are rounded, likely by chemical and mechanical erosion. In many cristaly wholes were observed, which may resemble with imprints of algal filamtents. Thus it can be supposed, that the nucleation of the cristal grain starts at the algal filament.
(2) As a second observed type, consistet of aggregate of cristals, that grew radially around the ending of some filaments.


This first observations shows that algae can play an important role for the nucleation and growth of cristal growth and so for tufa formation.

References:

SANDERS, D.; UNTERWURZACHER, M. & RÜF, B. (2006): Microbially induced calcium carbonate in tufas of the western Eastern Alps: a first overview. Geo.Alp, Vol.3: 167-189

SCHLETTERER, M.; PERNEGGER, L. & BRESSAN, D. (2006): Tuff production at the "Teufelskanzel", Mühlauer Klamm. Unpublish. report "Cyanobacteria and calcification, an introductory course for Biologists and Earth Scientists."

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.

Accretionary Warp

It´s an ice wedge... no wait - it´s an Accretionary Wedge...