Accretionary Wedge #25: Geo-Image

The current edition of the "Accretionary Wedge" is hosted by Highly Allochthonous. The motif this month is to gather geology-related images. Outcrops, sections, satellite images, minerals, fossils, seismic images, diagramms etc.

Here is mine: The Permian-Triassic transition epxosed at the Northface of the "Aferer Geisler" (Dolomites, Northern Italy).

The Bellerophon Formation (the brown/yellow succession in the lower part) represents late Permian (Changhsingian) shallow marine to marginal marine environments that yield insight into the pre-extinction world. The end-Permian mass extinction is suggested to have wiped out about 95% of all marine species, and thus is considered as the most severe biotic crisis that metazoan life encountered on our planet. The Werfen Formation (the grey to reddish slope in the middle part of the picture) extends from the latest Permian (latest Changhsingian) to the lower Triassic (Induan/Olenkian) and is one of the best studied succession of the end-Permian mass extinction and its aftermath. In this picture, the extinction level is exposed approximately where the trees end. The steep cliffs forming the top of this range are composed of reef carbonates for which the Dolomites are so noted.

The Dolomite region has been selected as a Unesco World Heritage site. Besides the breath-taking beauty of this landscape, the significance of this region for earth sciences has also been taken into account.

Chirotherium World Tour

A team of scientists from the TU Freiberg recently unearthed well-preserved tetrapod footprints from the Triassic of the High Atlas (Morocco). Surprisingly, this ichnofauna is dominated by the ichnogenus Chirotherium, wich is suggested to present an exclusive element of North-Pangean or Laurasian localities that are nowadays associated to Europe, China and North America. Although the scientists are aware that similar trackways were reported from western Gondwana (Argentina; Peabody, 1955), it was stated by several local newspapers that the imprints represent the first occurrences of such traces from Gondwana.

Fig. 1: Pes (the big one) and manus imprint of the ichnogenus
Chirotherium from the Triassic of Morocco (courtesy of Jan Fischer).

Extensive field work yielded several well-preserved imprints and trackways that can be assigned to the ichnospecies Chirotherium barthii (fig. 1), which is described from (watch out, confusing terms) upper Lower Triassic (Olenekian) to lower Middle Triassic (Anisian) rocks like the Moenkopi Formation of the western U.S. or the Buntsandstein of Central Europe (Klein & Haubold, 2007; and references therein).

As noted above, at least the ichnogenus seems to occur in Argentina as well but the new data from Morocco now strongly support the hypothesis of Peabody (1955) that Chirotherium is a track with a global distribution and its archosaurian producer inhabited the northern and southern hemisphere (see a reconstruction of the palaeoenvironment in fig. 2).

All specimens are currently under investigation by Hendrik Klein, Sebastian Voigt and Jörg Schneider of the TU Freiberg and I expect some interesting papers to be published in near future. For instance, the age of these findings will play an important role in unravelling the evolutionary history of archosaurs.

Fig. 2: A reconstruction of the palaeoenvironment based on the
geological context and sedimentary analysis of the track bearing interval.
Drawn by F. Spindler (taken from Sächsische Zeitung, march 20/21, 2010).

References

Peabody, F.E., 1955: Occurrence of Chirotherium in South America: Geological Society of America Bulletin, v. 66, p. 239-240.

Klein, H., Haubold, H., 2007: Archosaur footprints - potential for biochronolgy of Triassic contintal sequences. In Lucas, S.G., Spielmann, J.A., (eds): The Global Triassic. New Mexico Museum of Natural History and Science Bulletin 41.

Run crinoid, run!

This one has been posted already here and there on the net and actually, the paper was published 2.5 years ago. However, this report really surprised me and I want to share my amazement.

Fig. 1: Gif-movie showing crawling crinoid in quick motion.
Picture from cover of Palaeontologia Electronica Vol 10/1

Baumiller and Messing (2007) report that extant isocrinids are able to move as fast as 10 - 30 mm per second using their "arms" to crawl over the seafloor (fig. 1). Although some groups of crinoids were suggested and proven to perfom some sort of locomotion, the authors provide evidence for an almost "benthic-vagile" lifestyle of a group of organisms that is largely recognized as de facto sessile.

This contribution concerns me for two reasons. First, I am highly interested if there are some trace fossils that were found to represent crinoid locomotion (see fig. 2) and second, the portion of crinoids suggested to apply this kind of locomotion is highest in the Triassic (fig. 3).

Fig. 2: Traces of Davidaster rubiginosa in a fishtank experiment, scale bar: 20 mm (Baumiller and Messing, 2007).

Fig. 3: Generic diversity of crinoids from Ordovician to modern times. Red bars represent the portion of crinoidtaxa that might have been able to perform the observed mode of locomotion (Baumiller and Messing, 2007).

Working in the lower Triassic with a keen interest in ichnology, I will keep this work in my head when returning to the field. Does anybody knows about crinoid trace fossils?

Reference

Baumiller, T.K., and Messing, C.G., 2007: Stalked Crinoid locomotion, and its ecological and evolutionary implications. Palaeontologia Electronica, v. 10/1. http://palaeo-electronica.org/paleo/2007_1/crinoid/index.html

New old Blog

It is online for quite a while so it is not really new: A blog by Kevin Bylund called Ammonoida which is focused on Cephalopds from the U.S. Kevin joined the recent field trip. He is an Ammonite-specialist and there is probaly no one who knows better about the Geology of Utah and adjoining areas.

From the east coast to the west coast...

Recently, I returned from a field trip with American (Jim Jenks and Kevin Bylund) and French (Dr. Arnaud Brayard) Cephalopod researchers. I have been in the south-western U.S. for almost 4 weeks to see the Panthalassian faunas mainly of the Smithian and Spathian (Upper Early Triassic, Olenekian if you want). I've got a lot of things to do right now so I just will post some pictures from the field trip and some ichnologic goodies. Almost everything that is suggested for publication will emerge here (if any) after definite publication. It is not that I am conceited or afraid that someone snitches my ideas but most journals require that the submitted material is not published elsewhere in any form (hence, including blog-posts). In fact, currently I am working on a manuscript on some trace fossils from the Dolomites that I'd love to show you. Anyway back to the U.S. (as always: click to enlarge!):

The ?Thaynes Formation at the Dog Valley locality (Pahvant Range, central Utah).

Our camp with the Thule Valley in the background seen from the Disappointment Hills (Confusion Range, Utah) . The backmost mountains belong to the House Range and are mainly composed of Cambrian sediments.

One of the sections at the Disappointment Hills locality. The succession of interest starts at the right with a calcarenitic bed (the bright bedding plane) blanketing a ?permian paleo-relief. The Triassic here is represented by the Thaynes Formation (Smithian and Spathian) .


Well, the desert can be a lonely place...


...but furry guests show up from time to time.

Thats a locality called Smiths Phalen Ranch near Currie (Nevada). See the post on Ammonoidea.


"Superb" outrcop conditions in NE-Nevada (Winecup Ranch, or something). We weren't even sure if its Lower Triassic at all.


The morning after a 25°C drop in temperature.


The Spathian Virgin Member (stratigraphic nomenclature is debated, some researcher refer to the Vrgin Limestone Formation) near Hurricane. Basically, a shale interbedded with a series of prominent limestone ledges.


The lowermost of such "ledges", here very variable in thickness. It pinches out towards the left. I think it represents an estaury filling incisions in the underlying terrestrial red beds. The base of the Virgin member is highly variable in facies. It must have been a very dissected coastline with shoals, tidal flats, lagoons and estuaries. Honey Moon Trail east of the Hurricane cliffs.


The same little mesa showing the prominent pinch-out towards the left.


The Hurricane Cliffs east of Hurricane (Utah).


So called "wrinkle structures". Little pseudo ripples which are formed by microbial mats. It is considered as an "anachronistic" facies showing up in areas or times when grazing and bioturbation in general is dramatically reduced due to nonexistence of grazers and burrowers (Lower Cambrian) or as a result of a previous massive extinction (Lower Triassic). If you are interested read Pruss et al. 2004 for instance.


An ichnologic goodie: Cruziana in the lower Triassic. Usually, Cruziana is suggested to have been produced by Trilobites. As they went extinct in the course of the end-Permian mass extinction, similar structures can be obviously produced by someone else. A paper dealing with this topic is Zonneveld et al. 2002. The occurence reported in that reference is dated to the Middle Triassic. So my specimen (Spathian Virgin Member) should be the earliest large Cruziana after the end-Permian Mass extinction found so far. Well, the photographed specimen is not the whole story and I hope I can come back to this one when we have better data and a publication.


Me and my little clam truck.

References

Pruss S. B., Fraiser M. L., Bottjer D. J. 2004: The proliferation of Early Triassic wrinkle structures: implications for environmental stress following the end-Permian mass extinction. Geology, 32, 461–464.

Zonneveld J. P., Pemberton S. G., Saunders T. D. A., Pickerill R. K., 2002: Large, Robust Cruziana from the Middle Triassic of Northeastern British Columbia: Ethologic, Biostratigraphic, and Paleobiologic Significance. Palaios, 17, 435-448.

South Tyrol/ Italy II (July/ August, 2009)

I am just back from a short 9 day field session again in the Dolomites. We completed the documentation of the Werfen Formation at the San Pellegrino and started to log and sample an additional section at the Rosengarten/ Catinaccio with some surprising results. I will get back to it later when I have a sound database. Just for the record: trace fossils are awesome. Haha.

The Rosengarten/Catinaccio section exposing the lower Werfen Formation (click to enlarge). Not to scale due to perspective distortion in the upper part. Whole outcrop represents approximately 90 metres of exposed strata. Oh, I forgot to indicate that the extinction level roughly represents the Permian-Triassic boundary.

South Tyrol/ Italy I (May, 2009)

Here are some rather touristic impressions from the field campaign (click on the pcitures to enlarge). The task of the first session was to find appropriate sections...

The Peitlerkofel (Sas de Pütia) as seen from "Würzjoch". As you see there is still plenty of snow in May. We were'nt able to document a section here. The reddish/grey slope in the foreground is Grödner Sandstein Formation (Permian). Terrestrial plain and river sediments. The Permian Bellerophon Formation and the Permotriassic Werfen Formation is well-covered with snow.

The Permian Grödner Sandstein of the Bletterbachschlucht. Supervisor for scale in the lower left. This is a spectacular gorge. Unfortunately the upper part of the canyon was not accessible due to floods earlier this year. So we did'nt see the P/T boundary below the Weisshorn.

The Werfen Formation below Cimon della Pala at Passo di Rolle. In fact a nice outcrop but very risky when it comes to sampling and documenting the section.

Me on the way to Cima dell Uomo above Passo San Pellegrino. Snow everywere.

The Bellerophon Formation at the slopes of the Aferer Geisler seen from the Günther Messner Steig.

Me for scale at the Val Badia Member (Werfen Fm.), Val a Averta

Packing samples after 5 days of work at the Aferer Geisler section.

The upper 30 metres or so of the Aferer Geisler section (Seis Member). Supervisor (black something) for scale somewhere in the lower left.

The lower Werfen (from lower right to upper left): Mazzin Member, Andraz Horizon Member, Seis Member, ?Gastropod Oolith Member and Campil Member (red). The photo is taken from the slopes between Cima dell Oumo and Costabella (Passo San Pellegrino).

The upper Werfen below Costabella. It does'nt look spectacular but it is the best outcrop seen so far to see the complete upper Werfen Formation without breaking my neck. It is just too far to identify the members from this perspective.

These dudes saved my life several times i guess.

There it is: The End-Permian Extinction level at Rosengarten/Catinaccio. The lower bed is full of shelly fossils whilst the upper bed is devoid of life. Certainly, you can see such contrasts in other settings as well merely due to facies change or something but the following beds yield almost no fossils. Some authors refer to the "End Permian Death Zone".

Trees.

Cimon della Pala seen from Val Venegia.

I won't take this way.

San Pellegrino seen from Costabella.


A similar view 13 days earlier.

A typical Dolomite landscape in Val Badia near Misci and Seres. The mountain in the background should be Kreuzkofel (Sasso Croce).

Latemar seen from Rosengarten/Catinaccio.

A Bob Ross painting: Karer See with Latemar.


Cimon della Pala from Val Venegia