THE WORKING GROUP ON GONDWANAN BIOGENIC STRUCTURES

Newsletter Number. 1. (17/3/1999)

Editor . Dr Simon Braddy, Department of Earth Sciences, University of Bristol,

Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ, U.K.

Email. S.J.Braddy@bris.ac.uk

Dear Gondwanan ichnologist,

Welcome to the first newsletter of the Gondwanan biogenic structures working group. I would like to thank all of you for joining, especially those of you who have contributed something to this newsletter. Although many ichnologists expressed an interest in participating, I have received relatively few contributions, particularly statements of current research.

I have advertised this new working group in the Palaeontological Association Newsletter (1998, V. 39, p. 5) and the Ichnology Newsletter (1999, V. 21, p. 17). I also e.mailed circulars to various ichnologists, asking them to forward news of this new working group to others. I hope, by now, that most of the ichnological community is aware of our new group. Please 'spread the word' and lets try and make the next issue even bigger and better.

As many of you already know, this working group stems from the Gondwana-10 symposium in Cape Town (June 28th - July 5th, 1998). During this meeting it was proposed that a working group on "Gondwanan biogenic structures" should be formed to facilitate communication between ichnologists working on Gondwanan trace fossils. I was asked to act as the working group leader, and to set up and co-ordinate the activities of the working group.

As I have mentioned in the circulars, announcing this group, I see the main aims of our group to be: (i) To correlate the palaeoecological and stratigraphic distribution of ichnotaxa between the various Gondwanan continental fragments, and (ii) To attempt to recognise which ichnotaxa (if any) are endemic to Gondwana. Remember that this is your working group, so we should steer our agenda together. If anyone feels that additional aims or objectives should be addressed, please report them to me. Our deliberations will be reported to the Subcommission on Gondwana Stratigraphy (SGS), a division of the International Commission on Stratigraphy (ICS), which is sponsored by the International Union of Geological Sciences (IUGS). Therefore we all have an opportunity to 'raise the profile' of trace fossils, particularly in their (potential) stratigraphic value.

The SGS is devoted to the promotion and co-ordination of specialists in different fields of Geology involved in research related to the geological evolution of Gondwana. Its main objective, understanding the evolution and dispersal of Gondwana, has been largely fulfilled. However, the global correlation of late Paleozoic-Mesozoic Gondwanan sequences, remains to be resolved in detail. Therefore the SGS is focusing its attention, through its working groups, in this direction. There are several other working groups related to the SGS. The groups concerned with 'Gondwana Glacial Deposits' and 'Gondwana Sutures and Fold Belts' have achieved their objectives and published their results. I hope that our group can be as productive as these two.

A newsletter will act as the primary means of communication between the working group members. I have distributed this issue over the internet to all members and intend to do the same for later issues. This is because there is considerable expense in producing multiple copies of a newsletter in hard copy format (something that the editors of the newly revived "Ichnology Newsletter" will appreciate!), and I wanted to avoid charging a fee. Also, information in electronic format is much easier and quicker to distribute. I hope that you are all able to access the information and that the format is satisfactory. I have deliberately kept the format simple and have excluded figures (to limit the size of the file and avoid format problems). A few hard copies of this newsletter have been produced and sent to those of you who have expressed an interest in this format.

This newsletter contains contact information for members, (rather few) statements of each contributors research (and recent publications relating to Gondwanan ichnology), any articles which were submitted, announcements and a 'debate' section. I hope that these newsletters will also act as a forum for reporting, and discussing, the activities of the SGS. It is inevitable that there will be some overlap with the Ichnology Newsletter (Eds. A. Rindsberg and A. Uchman), although I hope that our efforts may be concentrated more towards the discussion of 'ichnostratigraphic' issues, particularly relating to Gondwana. I hope that members will continue to contribute articles and information to the newsletters, relating to their research on Gondwanan trace fossils.

So what does the future hold for this working group? This depends very much on the response I get from you, the academic community. I hope that this group will act as a focus to discuss issues relating to the value of trace fossils in Gondwanan stratigraphy, perhaps leading to various multi-authored papers on the subject in the future. I intend to produce a web-site, which will contain the newsletters, and (hopefully) a data-base on the stratigraphic distribution of Gondwanan trace fossils (from data supplied by contributors).

I would like to take this opportunity, therefore, to invite members (and others interested) to contribute to and/or receive the next newsletter. Please can you send your contributions to newsletter 2, as before, via e.mail if possible (to save retyping) and structure them as follows: Name, address, e.mail, phone, fax, outline of research relating to Gondwanan ichnology (c. 100 words), a list of recent (last few years), publications relating to Gondwanan ichnology, any articles which you care to submit (c. few hundred words) and any discussion relating to the debate (i.e. new suggestions for issues to debate, or points raised from this issue). Please contribute something to the next newsletter (even if just the contact and research interests sections). If this working group is to be an active one it will require input from you, the ichnological community. Please send contributions (in English preferably, but other languages will be acceptable) to Dr. Simon Braddy <S.J.Braddy@bris.ac.uk>. I will produce the next newsletter as soon as I receive a suitable number of contributions. Finally, please distribute this newsletter to anyone that you think might be interested in joining our working group.

c/o Council for Geoscience, PO Box 572, Bellville 5735, South Africa

(John has now left his position at the survey but mail should be forwarded to him from his old address)

Email: johnalmond@yahoo.com

Recent publications relating to Gondwanan ichnology:

Almond, J. 1998. Trace fossils from the Cape Supergroup (Early Ordovician-Early Carboniferous) of South Africa. Journal of African Earth Sciences, 27 (1A), 4-5.

Almond, J., Evans, F. and Cotter, E. 1998. Cape Supergroup Field Trip (Gondwana-10 excursion field guide). 64 pp. (This includes an excellent summary of the distribution of Early Palaeozoic traces from southern Africa, p. 63-64)

See also papers with Braddy, S. J. (see below)

Editor, Gondwanan Biogenic Structures Newsletter

Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ. UK.

Email: S.J.Braddy@bris.ac.uk

Phone: (0117) 928 7790

Fax: (0117) 925 3385

Research:

1. Eurypterid trackways from the Graafwater and Peninsula Formations, lower Table Mountain Group (Ordovician) of the Western Cape Province, South Africa (see Braddy 1998, Braddy and Almond 1998, in press). The ichnotaxonomy of trackways preserved on the "Brandenburg slab" from the Graafwater area is reassessed, with the recognition of two distinct forms: (i) Palmichnium capensis, consisting of series of four tracks, many accessory imprints and (usually) an intermittent bilobed medial impression, and (ii) Petalichnus brandenburgensis, a much narrower trackway with nine to ten tracks per series and no medial impression. Palmichnium capensis is interpreted as the locomotory trace of an onychopterellan eurypterid (Chelicerata:Eurypterida). Petalichnus brandenbergensis is provisionally ascribed to the Trilobita.

2. Abundant trace fossils in the ?Lower Devonian Muth Formation (Pin Valley, Spiti, northern India) (see Draganits et al. 1998). This ichnoassemblage consists of abundant Palmichnium antarcticum and Diplichnites gouldi with rarer Diplopodichnus biformis, Beaconites antarcticus, and other traces. The palaeoenvironment of the Muth Quartzite is interpreted as a marginal marine (foreshore/backshore) setting. The arthropod trackways occur predominantly in the upper part of the formation. The abundance and frequently sub-parallel orientation of the Palmichnium antarcticum trackways suggest that stylonurid eurypterids, which are interpreted as their producers, were migrating en-masse across the shoreline, perhaps en-route to quiet water pools. The similarity of this ichnofauna to other trace fossil assemblages in comparable depositional environments of similar age, in Antarctica and Australia, suggests that a recurrent Lower Devonian ichnocoenosis around the margins of eastern Gondwana may be recognised.

Recent publications relating to Gondwanan ichnology:

Braddy, S. J. 1998. Arthropod trackways from South Africa. Geoscientist, 8(7), 4-6.

Braddy, S. J. 1998. Permian Polaroids: snap-shots of ancient environments and animal activities. Palaeontological Association Newsletter, 39, 4 (meeting abstracts).

Braddy, S. J. and Almond, J. 1998. Eurypterid trackways from the Table Mountain Group (Lower Ordovician) of South Africa. Journal of African Earth Sciences, 27 (1A), 34-36.

Braddy, S. J. and Almond, J. In press. Eurypterid trackways from the Table Mountain Group (Lower Ordovician) of South Africa. Journal of African Earth Sciences.

Draganits, E., Grasemann, B. and Braddy, S. J. 1998. Discovery of giant arthropod trackways in the Devonian Muth Quartzite (Spiti, India): implications for the depositional environment. Journal of Asian Earth Sciences, 16 (2-3), 109-118.

Department of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.

Email: marga@Chch.plaNet.org.NZ

INSUGEO. Casilla de correo 1 (CC), 4000 San Miguel de Tucumán, Argentina

Email: insugeo@unt.edu.ar

Phone/Fax: (54) (81) 236395

Zoology Department, University of Stellenbosch, Private Bag X1, Matieland, 7602, South Africa.

Email: fevans@geobell.org.za

Research:

Currently, I am writing up a paper on vertebrate and invertebrate traces from the L. Triassic of South Africa in collaboration with J. MacEachern and G. Groenewald. I also have another paper with Welman, MacEachern and Groenewald on vertebrate traces from South Africa, which I mentioned in my talk at Gondwana-10 (this will include evidence for some of the earliest social behaviour of vertebrates by means of their traces). I am also planning a paper on little known invertebrate traces from the earliest Carboniferous of South Africa with J. MacEachern.

INSUGEO. Casilla de correo 1 (CC), 4000 San Miguel de Tucumán, Argentina

Email: insugeo@unt.edu.ar

Phone/Fax: (54) (81) 236395

Departamento de Cs. Geologicas, Universidad de Buenos Aires, Ciudad Universitaria Pab. II, 1428, Buenos Aires. Argentina.

Email. claumar@gl.fcen.uba.ar

Tel/Fax: 54-1- 576-3329

Ricardo Melchor

Universidad Nacional de La Pampa

Postal Address: Av. Uruguay 151, 6300 Santa Rosa,

La Pampa, Argentina

Department of Geology, Box 117 Station B Vanderbilt University Nashville, Tennessee 37235, USA

Email: MillerMF@ctrvax.Vanderbilt.edu

Recent publications relating to Gondwanan ichnology:

Miller, M. 1998. Effects of Permian extinction on freshwater bottom-swelling animals inferred from biogenic structures. Journal of African Earth Sciences, 27 (1A), 138.

Coeditor, Ichnology Newsletter

Geological Survey of Alabama, P.O. Box O, Tuscaloosa, AL 35486, USA

Email: arindsberg@ogb.gsa.tuscaloosa.al.us

Phone: (205) 349-2852

Fax: (205) 349-2861

Research:

In 1999, I will begin an ichnologic investigation of the Lower Cambrian Rome Formation of Alabama, USA. The Precordillera of Argentina broke away from Laurentia while this unit was deposited. Virtually identical rocks are exposed there, as shown by Bill Thomas (University of Kentucky) and by Argentine geologists including Ricardo Astini (Universidad Nacional de Cordoba). Talks with these geologists during their recent stay at the Geological Survey of Alabama inspire me to investigate the Alabama-Argentina connection, at least at this end.

Engelfriedshalde 25, D-72076, Tübingen, Germany

Department of Geology and Geophysics, PO BOX 208109, Yale University, New Haven, CT 06520-8109

Tel: (203) 432-3173

Department of Geology and Petroleum Geology, King's College, University of Aberdeen, AB9 2UE, Scotland.

Email: n.trewin@geol.abdn.ac.uk

Tel: (01224) 273448

Fax: (01224) 272785

Research:

1. Silurian-Devonian circum-Gondwana quartzites. Nigel Trewin and Ken McNamara are continuing work on arthropod traces from the Tumblagooda Sandstone of W. Australia, building on published work (Trewin & McNamara, 1994, Trans. R. Soc. Edinb. 85, 177-210). Work is in progress on subdivision of traces previously assigned to Diplichnites. The age of the Tumblagooda Sandstone continues to be controversial with the latest proposed age being Early Silurian (Well correlations by other workers), If this is the case, a lot of large arthropods were capable of walking on land at this early time! Comparisons with other circum-Gondwana Early Palaeozoic assemblages in sandstones are clearly a major priority for Gondwanan ichnologists.

2. Permian, Falkland Islands. Rich, diverse ichnofaunas of presumed non-marine turbidite to delta associations have been located and collected from the Falkland Islands. Superb Undichna/Umfolozia associations very closely comparable with South African ichnofaunas are being studied, and close comparisons can also be made with the late Palaeozoic non-marine associations in South America. Trace fossils assemblages will be described following a third visit to the Falklands by NHT in January 1999, and this work will be utilised and amplified in the PhD thesis of Chris Thomas on the Permian of the Falklands (Aberdeen-CASP, project started 1997).

Departamento de Paleontología, Facultad de Ciencias, Igua 4225, CP 11400, Montevideo, Uruguay.

Email: verde@fcien.edu.uy

Tel: (005982) 525 8618-23 int. 170.

Fax: (005982) 525 8617.

Research:

At present, my research with Gondwanan trace fossils from Uruguay is still somewhat incipient. I'm working with trace fossils from the San Gregorio Formation and Mangrullo Formation, both of Permian Age.

Department of Zoology, La Trobe University, Bundoora, Victoria, Australia 3083.

Email. a.warren@zoo.latrobe.edu.au

Tel. 61(03)94792241

Fax. 61(03)94791551

Research:

I am an early tetrapod worker concerned at present with the Early Carboniferous Ducabrook Formation of Queensland (Sue Turner is the ichnologist for this project ).

Technische Universität Berlin, Inst. für Angewandte Geowissenschaften II, FG. Historische Geologie und Paläontologie. ACK 14, Ackerstrasse 71-76, D-13355 Berlin, Germany.

Email: webb0933@mailszrz.zrz.tu-berlin.de

Tel: +493031 / 472905

Fax: +493031 / 479471

Research:

1. Palaeoichnological investigations on a Lower Ordovician trace fossil assemblage associated with an unusual polypreserved crustacean fauna from the Blaiklock Glacier Group, north-western Shackleton Range (W-Antarctica). A trace- and body fossil assemblage occurs in the Lower Ordovician Blaiklock Glacier Group (BGG) in the north-western Shackleton Range (Antarctica). Sedimentological data and palaeontological characteristics of the Blaiklock fauna point to an extremely shallow marine sedimentary environment. Large bivalved crustaceans have been reported for the first time from a Palaeozoic sequence in Antarctica (for a brief description see: Thomson & Weber, 1995, 1999, in press; Weber & Thomson, 1998; Weber et al., 1998). A complete and detailed description of the ichnofauna and the polypreserved crustacean fauna of the BGG is in preparation (in collaboration with M.R.A. Thomson (BAS) and S.J. Braddy). See the article by B Weber for more details.

2. Upper Cambrian and Lower Ordovician ichnofaunas from several siliciclastic sedimentary successions of the Eastern Cordillera in southern Bolivia (in collaboration with S. Egenhoff). This field work has been sponsored by the German National Science Foundation (DFG), Special Research Project: SFB-267). See the article by B Weber and S. Egenhoff for more details.

Recent publications relating to Gondwanan ichnology:

Weber, B. (1995): Fossilfunde in der Shackleton Range. In: Deutsche Gesellschaft für Polar-forschung (Arbeitstreffen, Aachen, 1995). Kurzfassung der Beiträge: 12-17.

Thomson, M.R.A. & Weber, B.(1995): A New and Unusual Fauna from the Blaiklock Glacier Group, Shackleton Range. (Initial Report). Contrib. Abstract Vol.: VII. International Symposium on Antarctic Earth Sciences (ISAE) , Siena (Italy), Sept. 1995: 375.

Thomson, M.R.A. & Weber, B.(1999, in press): Discovery of an Invertebrate Fauna in the Blaiklock Glacier Group, Shackleton Range, Antarctica and its Regional Implications. In: EUROSHACK Expedition Report. Terra Antartica (Special Issue), Siena, Italy (1999, in press)

Egenhoff, S.O. & Weber, B. (1998): Ichnofauna trends in a shallowing- and coarsening-upward succession: an example from the Arenigian of southern Bolivia. In: Abstracts of the 15th International Sedimentological Congress. Alicante (Spain), April 1998: 311-312.

Weber, B. & Thomson, M.R.A. (1998): Fazies und Ichnofauna der Mount Provender Formation (untere Blaiklock Glacier Group), Shackleton Range, Antarctica. Berichte zur Polarforschung. Bremerhaven. 277 (1998): 117-119.

Weber, B.; Thomson, M.R.A. & Buggisch, W. (1998): An Ordovician invertebrate fauna from the Blaiklock Glacier Group, Shackleton Range, Antarctica. In: Gondwana 10: Event Stratigraphy of Gondwana. Cape Town, South Africa. Journal of African Earth Sciences. Vol. 27 (1998) No.1A: .207.

Egenhoff, S.O., Weber, B. & Erdtmann, B.-D. (1998): Ichnofaunen-Trends in einer Flachwasser- abfolge, Mittleres Arenig, Südbolivien. GEO-Berlin '98, Berlin, 6.-9. Sept. 1998. In: Terra Nostra (Schriften der Alfred Wegener-Stiftung) 98/3: 34-35.

by G. Simpson (Univ. Bristol., Email <gs8826@bristol.ac.uk>)

Introduction

Trace fossils are generally regarded as poor biostratigraphic indicators as they are produced by facies restricted benthic marine organisms (Magwood and Pemberton 1990). Facies dictate behaviour thus the traces produced are influenced by environmental conditions. Traces can also show convergent evolution as they are a functional response to the environment. This is because there are a limited number of solutions for a given physiological problem, different animals can perform the same function and so ichnofossils represent a small amount of producer morphology (Fortey and Seilacher 1997). This means that most trace fossils are not distinctive enough to be used as zone fossils, often the body fossil record is good enough for correlation, but in some environments body fossils are absent. Cruziana occurs in such areas in which facies preserve trace fossils well, but not body fossils. Since Cruziana are abundant over the Precambrian-Cambrian and Cambrian-Ordovician boundaries they have been used to correlate stratigraphy world-wide, but this use of trace fossils is rare and highlights the need for the producer to be well known and understood.

Trace fossil problems

Specific behaviours can evolve repeatedly in the same species, or alternatively they can be produced by an entirely different organism that has developed a similar physical adaptation to an environment. This means that traces, however distinctive can be distributed widely throughout the fossil record (Magwood and Pemberton 1990). Generally the evolution of behaviour is not well enough understood to be of use in biostratigraphy (Magwood and Pemberton 1990), as it is environmentally

controlled, and changes in conditions usually result in ichnofaunal changes (Crimes 1987). This means that at specific intervals when there are only one or two possible producers of the trace certain facies represent distinctive trace fossil assemblages, e.g. the Cruziana facies described by Seilacher (1970). However, it does not mean they are restricted to this facies, only indicative of it.

To be a useful zone fossil, and to be used in stratigraphy a fossil should meet the following criteria; (i) The fossil should have a short time range, (ii) It should be morphologically distinctive, (iii) It should be independent of facies control, (iv) It should have world-wide distribution, and (v) Have a high preservation potential.

Few trace fossils are applicable to all of these as most have long time ranges, either due to the producer having a long time range, or through convergent evolution in behaviour producing similar traces. The producer of a trace could be a useful body fossil as the morphology will show changes, but morphological differences may not be reflected in the trace fossil record. Few are facies independent and wide distribution does occur, but again this is dependant on environmental and energy conditions. The preservation potential is high in infaunal burrows like Cruziana, as the facies inhabited were low energy and favour preservation. Trace fossils over-represent the benthic feeders, smaller organisms produce less traces and substrate type will record traces with differing success, the best being interbedded sands, silts and clays (Seilacher 1977).

However, the body fossil record is also imperfect. Fossil assemblages may have had post-mortem transport and mixing of remains. Diagenetic solution may remove fossils from certain sequences producing areas where a zone fossil is absent, but trace fossils are improved during diagenesis (Seilacher 1977). Trace fossils generally occur in situ and are rarely derived. As noted the disadvantage of using these is the facies restriction, but in North America, South America, Europe,

Southern Africa and Australia the Precambrian-Cambrian boundary is dominated by siliciclastic facies in which Cruziana is abundant (Narbonne et al. 1987).

Cruziana and Stratigraphy

There are various ways in which trace fossils are useful in stratigraphy; tracing the evolution of behaviour, as morphologic entities (without determining the producer) and as a substitute for the producer of the trace (Magwood and Pemberton 1990). It is the latter of these that mainly concerns Cruziana, although changes in behaviour are used to correlate sequences. Cruziana and other trilobite traces pre-date the appearance of trilobite body fossils (Crimes 1989). The appearance of Cruziana is useful in identifying and correlating the Precambrian-Cambrian boundary and the Cambrian-Ordovician boundary. Cruziana are undoubtedly attributable to trilobite burrowing activities in the upper sediment in search of food, and for protection from predators. Trilobites used their legs to dig down into the sediment, and then channel this along the midline of the animal towards its mouth, producing the characteristic 'V' scratch marks. A wide variety of burrowing behaviours developed, most prevalent was a dorsally bent attitude in the sediment, pulling the sediment underneath it and depositing it behind thus producing the trail (Seilacher 1994).

The stratigraphic ranges of these traces corresponds to trilobite body fossils, and changes in the size of the trace relate to changes in the trilobite morphology. The traces do not fit any other arthropod group of comparable size that occur through this time range (Seilacher 1970). The producer and producing mechanism of Cruziana is well understood, so a high degree of distinction between ichnogenera is possible, allowing finer levels of correlation between different areas. It is most abundant in a siliciclastic facies, and it occurs in this so often that Seilacher (1970) assigned it to this facies type. This facies restriction of Cruziana is a contradiction to the criteria for a good zone fossil, but comparative fossils such as early Cambrian shelly fauna are very provincial in distribution, whilst trace fossils have good distribution (Narbonne et al. 1987).

Traces and body fossils rarely occur together, as trace fossils are best preserved in sandstones which do not favour the preservation of body fossils, as they are permeable and body fossils can be easily dissolved during diagenesis (Seilacher 1970). This means that traces are important in stratigraphy in this kind of facies (Crimes 1970). It is possible that every Cruziana could represent only one species of trilobite varying its behaviour in response to environmental conditions, however the choice of burrowing technique appears to be specific to certain species of trilobite (Seilacher 1970).

Precambrian-Cambrian Boundary

The Precambrian-Cambrian boundary contains few body fossils as the dominant facies across the boundary is a shallow water clastic environment, but trace fossils are abundant (Crimes et al. 1977). Correlation is based on the first occurrences of the trace as many of the fossils range from the Cambrian through the Phanerozoic. The fossils are vertically zoned into three stages of incoming ichnofauna that indicate a particular time zone. Zone 1 represents the Upper Vendian and includes Skolithos, Neonerites and Bilinichnus. Zone 2 represents the Lower Tommotian, and includes Phycodes and Bergaureia. Zone 3 is the Upper Tommotian and has the first appearance of Cruziana, "Diplichnites", Rusophycus, Astropolichnus and Diplocraterion (Crimes 1987).

As silciclastic facies are widespread across the boundary, correlation is easier as Cruziana occurs frequently in this facies type. Facies control on the producers may have been less important than it is in contemporary environments, as shallow water sequences show typically 'shallow' and 'deep' water ichnofaunal assemblages (Crimes 1987). To demonstrate the use of trace fossils as tools for correlation Crimes (1987) analysed 15 localities world-wide and identified ichnogenera occurrence in order of appearance. Of the 50 ichnogenera used only 18 occurred 5 or more times in each locality. Cruziana has now been used in Canada, USA, Argentina, Greenland, Scandinavia, Spain, Russia, India and China as a zone fossil (Crimes 1989). Correlation based on these zone fossils, using Planolites and

Cruziana as end members can define the boundary of the Tommotian-Atdabanian, and indicates the start of the Cambrian.

Cambrian-Ordovician boundary

The use of Cruziana to identify and correlate the Cambrian-Ordovician boundary has been called the 'ichnostratigraphic paradigm' by Magwood and Pemberton (1990). This refers to the changes in Cruziana throughout this interval. C. semiplacta occurs in the Upper Cambrian and Tremadoc, but not in the Arenig, whilst C. furcifera occurs in the Arenig, and the Tremadoc, but not in the Upper Cambrian (Crimes 1970). This has been used in the British Isles, Europe and Newfoundland to correlate the boundary. Another feature is first appearance of an intermediate type, C. rugosa, marking the base of the Arenig. The overlap of C. semiplacata and C. furcifera give the range of the Tremadoc allowing the boundary of the non-fossiliferous Cambrian-Ordovician boundary to be found (Magwood and Pemberton 1990). However, Magwood and Pemberton (1990) show that the Lower Cambrian Gog Group in Alberta, contains all four Cruziana that are used to identify the Cambrian-Ordovician boundary. This would mean that these ichnogenera cannot be used as global index fossils, as C. rugosa occurs in the Gog Group it indicates that the Baltica and Armorica provinces had different ichnogenera to the North American provinces in the Cambrian. The producer of C. rugosa may have evolved in North America and then migrated. This difference in dates can be explained. Trilobites are restricted to

benthic shallow marine habitats, and are subject to provinciality (Seilacher 1994). The ichnostratigraphic framework used only applies to Gondwana as little is known from the other palaeocontinents. The distribution and succession for other palaeocontinents has yet to be found (Seilacher 1994). Seilacher (1994) shows that the Canadian C. rugosa is a different ichnospecies and is morphologically different to other C. rugosa. The Canadian species has coarser scratching along the midline with a

wider angle than the other scratch sets. C. rugosa has multiple scratch sets that intersect on the mid-line.

Conclusions

Using trace fossils as biostratigraphic indicators is difficult. Knowledge of the producer is preferable to understand the mechanisms of production, especially in arthropods. However, identifying the trace producer is difficult as it requires morphological knowledge of the producer. Appendages that produce a structure could evolve several times throughout the fossil record as they are a functional attribute and therefore show a high degree of evolutionary convergence. This could be due to the organisms inhabiting environmentally similar habitats, so the solution to a morphologic solution will be very similar. This will be exhibited in the benthic marine arthropods to a greater amount as they have existed for a longer period of time. The few post-Palaeozoic examples are well out of the time range of Cruziana and therefore should not be confused with them. A useful zone trace fossil should be

correlated with its producer to be certain that it is a comparable structure to the other traces in a succession. The palaeogeographic distribution of the trace should match the producer to be certain that is a contemporary to other similar traces in the area.

Few trace fossils are facies independent which can be problematical in correlation. Restriction to a facies means that sequences of the same age but different settings can have a completely different range of fossils in them. This is often not a problem when body fossils are used, as commonly they may be planktonic or pelagic, and are therefore present in a range of facies. However, trace fossils such as Cruziana are applicable for use as zone fossils. The formation of them by trilobites is well understood, and the morphological variations have been well documented. The succession of Cruziana can therefore be used in correlation, and can be used to identify boundaries. Facies restriction does not apply across the Precambrian-Cambrian and Cambrian-Ordovician, as siliciclastic facies are predominant over these boundaries. It is in areas such as these, using well documented trace fossils that they can be used as tools for correlation. However, there is still a palaeobiogeographic bias as little is known about Cruziana from north America and Russia / northern Asia. These are the contemporary palaeocontinental realms to Gondwana (Seilacher 1994). Without knowing the full extent of Cruziana range and succession, questions will persist on the use of it as a zone fossil.

References

Baldwin, C.T. 1975. The stratigraphy and facies association of trace fossils in some Cambrian and Precambrian rocks from north-western Spain. p 9-40 . In: Crimes, T.P and Harper, J.D. Trace fossils 2. Special issue of the geological Journal 9.

Crimes, T.P. 1975. The stratigraphic influence of trace fossils. p 109-130. In Frey, R.W. Ed. The study of trace fossils. New Yrok. Springer-Verlag.

Crimes, T.P. and Anderson, M.M. 1985. Trace fossils from the late Precambrian and early Cambrian strata of south-east Newfoundland (Canada): Temporal and environmental implications. Journal of Paleontology. v 59. p 310-343.

Crimes, T.P. 1987. Trace fossils and the correlation of the late Precambrian and early Cambrian strata. Geological Magazine. v 124. p 47-119.

Fortey, R.A. and Seilacher, A. 1997. The trace fossil Cruziana and the trilobite that made it. Lethaia. v 30. p 105-112.

Narbonne, G.M., Myrow, P.M., Landing, E. and Anderson, M.M. 1987. A candidate stratotype for the Precambrian-Cambrian boundary, Fortune head, Burin Peninsula, south-east Newfoundland. Canadian Journal of Earth Sciences. v 24. p 277-1293.

Pickerill, R.K., Romano, M. and Melendez, B. 1984. Arenig trace fossils from the Salamanca area, western Spain. Geological Journal. v 9. p 249-269.

Romano, M. 1982. The Ordovician biostratigraphy of Portugal. A review with new data and re-appraisal. Geological Journal. v 17. p 89-110.

Seilacher, A. 1970. Cruziana stratigraphy of "non-fossiliferous" Palaeozoic sandstones. In Crimes, T.P. and Harper, J.C. eds. Trace Fossils. Geological Journal special issue 3. p 447-476.

Seilacher, A. 1977. Evolution of trace fossil communities. In Hallam, A. Ed. Patterns of evolution. Elesvier. p 359-376.

Seilacher, A. 1994. How valid is Cruzizna stratigraphy? Geologishe Rundshau. v 83. no 4. p 752-758.

by B. Weber

Trace fossils, natural casts of problematic soft-bodied organisms, and the impressions of phyllocarid-like crustaceans have been reported from the Blaiklock Glacier Group of the north-western Shackleton Range, Antarctica. The fossils occur in a succession of red beds containing mainly shallow-water sandstones and conglomerates with minor silty interbeds that was subject to periods of strong current activity. The trace fossil assemblage as well as the sedimentological characteristics (Buggisch et al., 1994a,b) of the sequence point to an extreme shallow marine, oxidising and high energy environment during the Blaiklock sedimentation. A lower to (at the most) middle Ordovician age of the rocks is indicated by radiometric and palaeomagnetic data as well. The Blaiklock Glacier Group sediments represent the first true autochthonous fossiliferous sequence of Ordovician age proved in Antarctica.

The Blaiklock fauna itself are unusual in that trace fossil-rich sequences contain natural casts of problematic soft-bodied organisms of unknown taxonomic position together with moulds of some and impressions of some of the probable track makers and large phyllocarid crustaceans. The BGG fossil assemblage contains the following listed groups of fossils:

(1) Planolites-type bioturbation layers; horizontal and partly meandering trails and trackways of non-arthropod trace originators (e.g. Gordia, Taphrhelminthopsis, Didymaulichnus).

(2) Trackways and moulds of true arthropod trace makers (e.g. Monomorphichnus, Merostomichnites, Cruziana, Rusophycus).

(3) Horseshoe-shaped casts or impressions on bedding surfaces of sandstones with well-developed parting lineation; probably casts of empty carapace valves belonging to bivalved arthropods (=Selenichnites).

(4) Circular to subcircular resting traces or impressions of unknown and problematic soft-bodied (medusoid?) organisms (some are probably pseudofossils).

(5) Casts and convex hyporeliefs of bilobate "coffee bean" shaped carapaces of bivalved arthropods, partly with vein shaped impressions of vesicles on the internal carapace surface.

(6) Impressions and casts of complete crustaceans showing two carapace valves being separated, by a dorsal hinge line with partly preserved impressions of thoracic segments, legs and a segmented abdomen. These large body fossils (ca. 5-12 cm in total size) are here provisionally considered to belong to the representatives of Palaeozoic phyllocarids (Malacostraca: Phyllocarida incertae sedis).

The BGG ichnofauna contains palaeobathymetrically significant taxa and points in accordance with the sedimentological data to a well-ventilated shallow marine shelf or coastal sedimentary environment. Trace fossils are generally unsuitable for biostratigraphic purposes but with respect to their composition, the BGG biota altogether show strong affinities of typical Lower Palaeozoic (Cambro-Ordovician) shallow marine trace fossil assemblages. The occurrence of large phyllocarid crustaceans in the BGG means the first evidence of this taxonomic group on the Antarctic continent. The predominant occurrence of the arthropod ichnotaxa Merostomichnites and Selenichnites is assumed by the author to be related to the activity of the bivalved BGG-crustaceans.

The Blaiklock sequence and their fauna show several sedimentological and palaeontological similarities with the basal units of the Ordovician Table Mountain Group (esp. the Graafwater Formation) of South Africa. The findings therefore support palaeogeographic models which suggest a Palaeozoic position of the Blaiklock sedimentary basin close to the Table Mountain basin. A research project will be focused especially on these SW-Gondwanan basin development and related sedimentological and palaeoichnological problems.

References:

Buggisch,W.; Kleinschmidt,G.; Höhndorf,A. & Pohl,J. (1994a): Stratigraphy and Facies of Sediments and Low-Grade Metasediments in the Shackleton Range. Polarforschung 63 (1): 9-32.

Buggisch,W.; Kleinschmidt,G.; Kreuzer,H. & Krumm,S. (1994b): Metamorphic and Structural Evolution of the Southern Shackleton Range during the Ross Orogeny Polarforschung. 63(1) 133-56.

Thomson,M.R.A. & Weber,B.(1995): A New and Unusual Fauna from the Blaiklock Glacier Group, Shackleton Range. Abstract Vol. VII. Internatl. Symp. Antarctic Earth Sciences (ISAE), Siena (Italy): 375.

Thomson,M.R.A. & Weber,B. (in press): Discovery of an Ordovician invertebrate fauna in the Blaiklock Glacier Group. In: EUROSHACK Expedition Rep.. Terra Antartica, Siena (Italy): (1999, in press).

Weber, B. & Thomson, M.R.A. (1998): Fazies und Ichnofauna der Mount Provender Formation (untere Blaiklock Glacier Group), Shackleton Range, Antarctica. Berichte zur Polarforschung. Bremerhaven. 277 (1998): 117-119.

Weber, B.; Thomson, M.R.A. & Buggisch, W. (1998): An Ordovician invertebrate fauna from the Blaiklock Glacier Group, Shackleton Range, Antarctica. In: Gondwana 10: Event Stratigraphy of Gondwana. Cape Town, South Africa. Journal of African Earth Sciences. Vol. 27 (1998) No.1A: .207.

*(Results of the European Shackleton Range Expedition (EUROSHACK) 1994/95. The project has been sponsored by the German National Science Foundation (DFG): WE 1640/ 2-1; ER 96/ 21-1)

by B. Weber and S. Egenhoff

General Aspects of Geological Setting and Stratigraphy (Egenhoff et al., 1998b):

The Cambro-Ordovician succession in southern Bolivia consists of more than 12 km siliciclastic sediments. The topographic distribution of the Upper Cambrian, Lower, Middle and Upper Ordovician strata is shown in the sketch map (Fig. 1). The development of the basin started in late Cambrian time with the sedimentation of more than 2 km of fluvial to marginal marine clastics, showing a general transgressive trend. During the Tremadocian, the deepening continued, leading to a shift of the coastline at least 20 km landward to the east. Large parts of the shelf fell below storm wave base, resulting in the sedimentation of black, laminated shales with intercalated low relief sandy channels and lobes. The Arenigian strata record an overall shallowing trend which is interpreted to result in the emergence of the shelf in late Arenigian to Middle Ordovician times. A coastline shift of about 50 km towards the west is assumed for that time-interval, leading to the deposition of coast-near storm deposits in the centre of the study area during the Middle Ordovician. In the Upper Ordovician, sedimentation is probably restricted to a narrow, north-south running deep marine basin in the western part of the study area.

Early Palaeozoic Ichnofaunas in Southern Bolivia:

Cambro-Ordovician ichnofossils from southern Bolivia and the adjacent areas in northern Argentina are known since the 19th century. Alcide d'Orbigny described the ichnogenus Cruziana for the first time from this region. Further hints to the occurrence of Ordovician traces in southern Bolivia have been published by Steinmann & Hoek (1912) and later by Branisa (1965). On the other hand, the details on the stratigraphic position, distribution and composition as well as the palaeoecological meaning of these ichnofaunas are general little known, and more recent palaeoichnological approaches to this material are hitherto missing.

During extensive sedimentological and tectonic studies concerning the below mentioned German research project (SFB-267), more detailed palaeoichnological field work has been carried out in several outcrops of the study area (Fig.1) in 1997 and 1998. Only parts of the results have been already published as short communication (Egenhoff et al.,1998a, Egenhoff & Weber, 1998). Other data are hitherto completely unpublished. More detailed publications are still in preparation. The following text only provides a general overview about the research aims in respect to the already recognisable results:

(a) The Torohuayco Formation:

A detailed investigation of a profile through a larger sequence of the Torohuayco Formation has been carried out at the southern margin of the Cerro Patillas, southwest of the Laguna Grande (following the road cut from Icscayachi to Villazon) in 1998. The mainly grey to brownish-grey (partly also reddish or greenish-grey) coloured and coarse to medium grained quartzitic sandstones belong to the Upper Cambrian Torohuayco Formation (Rivas et al., 1969) which is overlaying concordantly the more conglomeratic developed Camacho Formation (Suarez-Soruco, 1992). The Torohuayco Formation has been assumed to be not fossiliferous. Only Suarez-Soruco (1992) published a first hint to the occurrence of horizons of non-specific worm-like traces ("galerias de vermes") in the Torohuayco Formation. The field study of the mentioned outcrop in 1998 showed that actually the non-fossiliferous sediments alternate with 1-2 m thick intercalations of quartzitic sandstones containing well-preserved traces of Skolithos- and Diplocraterion-type domichnia. In addition, a (hitherto undetermined) specimen of an arthropod resting trace obviously belonging to the ichnogenus Rusophycus Hall, 1852 has been found in the erratic rock material occurring downslope the southern edge of Cerro Patillas.

(b) Ichnofauna trends in the Chaupi Uno profile:

A well-accessible outcrop near the village Chaupi Uno (Fig.1) provided the opportunity to study trends in the ichnofaunal composition and distribution in their relation to the sedimentological record. A section of about 400m of Middle Ordovician (middle to upper Arenigian) sediments has been recorded for sedimentological and palaeoichnological data. The occurrence of flat erosional terraces within the relatively steep slope of the outcrop enabled a (semi-quantitative) estimation of the composition of the ichnofauna and their distribution within the profile by counting of characteristic trace types of the assemblage using a simple method of counting of the traces in about 10m-(vertical) distances on standardised counting areas (ca.20x20 m) throughout the whole profile.

The succession consists of a lower part of about 300m thick pelitic rocks with abundant invertebrate shelly fossils (mainly trilobites and cephalopods) preserved in carbonate concretions followed by about 160m thick ichnofossil bearing strata. These successions shows a coarsening-upward pattern and is capped by regional unconformity with overlying Cretaceous rocks. The uppermost 160m of sediments show bioturbation features with a vertical zonation being obviously related to bathymetry and grain size changes respectively.

The trace fossil assemblage is predominated by simple unbranched and unornamented, sand- or silt-infilled, partly crossing horizontal burrows. In contrast to the previous statement of the authors published in the initial reports (Egenhoff & Weber, 1998, Egenhoff et al., 1998), all these burrows have to be attributed to the ichnogenus Palaeophycus Hall, 1847 (sensu Pemberton & Frey, 1982) as thin sections of the traces showed later that the infilling sediment of the burrows is the same like that of the surrounding sedimentary matrix.

This main assemblage is only locally and more rarely accompanied by several arthropod resting, furrowing, and walking traces (Rusophycus isp., Monomorphichnus Crimes, 1970) as well as by thin meandering traces belonging to the ichnogenus Gordia. These trace types are distributed in silty layers of nearby the whole succession, and are absent only in the uppermost and throughout coarse-grained sandstone beds.

The previously mentioned Palaeophycus-like burrows occur in two different types of traces predominating in bathymetrically different parts of the succession: Whereas the lower (mainly fine-grained) part of the sequence is characterised by very frequently occurring bioturbation horizons consisting mainly of a smaller form of burrows (type A: 2 - 5 mm in diameter), are the uppermost beds characterised by a trace fauna consisting almost entirely of a much larger form (type B: 6 - 10 mm in diameter). This infaunal trend obviously correlates with the shallowing and coarsening upward trend of the sedimentary environment. In this context, the smaller type A is restricted to the lower, fine-grained silty mudstone horizons of a low energy environment, whereas the larger type B seems to be distributed in both, the silty mudstones as well as in the coarser sandstone beds, and prevails in the latter. This distribution could be related to different demands of the unknown trace originators on their palaeoenvironment. The both trace types presumably represent the behaviour and life style of two taxonomically different originators probably preferring a different trophic and physical quality of their host sediment.

(c) Arthropod traces in the Sella profile - a further example of Gondwana-type ichno-assemblages?:

Sediments of Lower Arenigian age are outcropped in the uppermost part of a sedimentary succession in the surrounding of the village Sella, about 20 km north of Tarija. The brownish-grey mudstone, silt and sandstone beds locally contain fossil-rich layers of storm deposits with mainly fragmentary preserved trilobites and brachiopods. The soles of the massive sandstone beds show frequently well preserved ichnofossils, especially arthropod traces. The ichnofauna is predominated by partly excellent preserved specimens of the ichnogenus Cruziana d'Orbigny, 1842, especially occurring in the surrounding of Chaupi Cancha near Sella. The arthropod ichnofauna altogether shows strong affinities to the "Cruziana rugosa group" (sensu Seilacher, 1970; 1991) as Cruziana rugosa d'Orbigny, 1842 is the obviously predominating ichnospecies in the Sella assemblage. In the Sella beds, this ichnotaxon is rarely accompanied by Cruziana goldfussi Rouault, 1850 and by the much smaller Cruziana rouaulti Lebesconte 1883, both members of Seilachers "C. rugosa group". Further ichnotaxa are the frequently occurring resting traces of the ichnogenus Rusophycus Hall, 1852, and arthropod grazing traces of the ichnogenus Monomorphichnus Crimes, 1970. Interestingly, shape and average size of the Cruziana- (resp. Rusophycus-) type ichnofossils of the Sella beds correlate with those of some of the trilobite taxa (esp. with some representatives of the Ptychopariida: Asaphina; see Harrinton & Leanza, 1957) occurring in the storm layers and shales of the same succession.

The "Cruziana rugosa"-group has been first described by Seilacher (1991) as a typical, mainly (circum-) Gondwanan distributed ichno-assemblage of Lower Ordovician (Arenigian) age being obviously related to the more massive quartzites of the "Gres Armoricain" facies (Peneau, 1946; Seilacher, 1991). The sedimentary environment, the composition and stratigraphic position of the ichnofauna of the Sella beds in southern Bolivia support again Seilachers model of an existence of biostratigraphic relevant ichno-assemblages of Palaeozoic age as time-equivalent ichnofaunas of the same composition are reported from several other peri-Gondwanan deposits in Europe, N. Africa, Asia, S. America and Australia.

References:

Branisa,L.(1965): Los Fosiles Guias de Bolivia (I. Paleozoico). Serv. Geol. de Bol., Boletin No. 6 (1965), La Paz (Bolivia). pp.1-282.

Crimes,T.P. (1968): Cruziana: A stratigraphically useful trace fossil. Geol. Mag. 105 (4): 360-364.

Egenhoff, S.O. & Weber, B. (1998): Ichnofauna trends in a shallowing- and coarsening-upward succession: an example from the Arenigian of southern Bolivia. In: Abstracts of the 15th International Sedimentological Congress. Alicante (Spain), April 1998: 311-312.

Egenhoff, S.O., Weber, B. & Erdtmann, B.-D. (1998a): Ichnofaunen-Trends in einer Flachwasser- abfolge, Mittleres Arenig, Südbolivien. GEO-Berlin '98, Berlin, 6.-9. Sept. 1998. In: Terra Nostra (Schriften der Alfred Wegener-Stiftung) 98/3: 34-35.

Egenhoff,S.O.; Maletz,J. & Erdtmann,B.-D. (1998b): Geometric Changes during the Development of an Intracratonic Basin in Southern Bolivia. In. Abstracts of the 15th International Sedimentological Congress. Alicante (Spain), April 1998: 310-311.

Harrington,H.J. & Leanza,F.A.(1957):Ordovician Trilobites of Argentina. Dep. of Geology , Univ. of Kansas Spec. Publ.1 (1957): pp. 1-276.

Müller,J.; Maletz,J.; Egenhoff,S. & Erdtmann,B.-D. (1996): Turbiditas Caradocianas-?Ashgillianas en la Cordillera Oriental al sur de Bolivia: implicaciones cinematicas. Memorias del XII Congreso Geologico de Bolivia, Tarija (1996): 747-753.

d'Orbigny,A. (1842): Voyage dans l'Amerique meridionale (le Bresil, la Republique oriental del'Uruguay, la Republique Argentine, la Patagonie, la Republique de Chili, la Republique de Bolivia, la Republique du Peron) execute pendant les annees 1826, 1827, 1829, 1830, 1831, 1832, et 1833: v.3, pt.4 (Paleontologie), 188 p., 22pl. (1842); atlas for part 8 (1847), Pitois-Levrault (Paris), Levrault (Strasbourg).

Pemberton, S. G. and Frey, R. W. 1982. Trace Fossil Nomenclature and the Planolites- Palaeophycus Dilemma. Journal of Paleontology, v.56 (no.4): 843-881.

Peneau,J. (1946): Etude sur l'Ordovicien Inferieur (Arenigien = Gres Armoricain) et su faune (specialement en Anjou). Bull. Soc. Etude scient. Angers. n.s. 37: 74-76.

Rivas,S., Fernandez,A. & Alvarez,R. (1969): Estratigrafia de los sistemas Ordovicico, Cambrico y Precambrico en Tarija, Sud de Bolivia. Bol. Soc. Geol. Boliviana, 9(1969): 27-44.

Seilacher,A. (1970): Cruziana stratigraphy of "non-fossiliferous" Palaeozoic sandstones. In: Trace Fossils (T.P.Crimes & J.C.Harper, eds.). Geol. J. Spec. Issue, 3: 447-476.

Seilacher,A. (1991): An Updated Cruziana Stratigraphy of Gondwanan Palaeozoic Sandstones. In: "The Geology of Libya" Vol. IV.(Salem, Hammuda et Eiyouti, Eds.). 1991: 1565-81.

Seilacher,A. (1994): How valid is Cruziana Stratigraphy? Geol. Rundschau (1994) 83: 752-58.

Steinmann,G. & Hoek,H. (1912): Das Silur und Cambrium des Hochlandes von Bolivia und ihre Fauna. Beiträge. zur Geol. und Paläontol. von Südamerika. In: Neues Jahrb. Min. - Beilageband XXXIV (1912): 176-252.

Suarez Soruco,R. (1992): El Paleozoico Inferior de Bolivia y Peru. In: J.G.Gutierrez Marco et al. (Eds.): Paleozoico Inferior de Ibero-America. Univ. de Extremadura. (1992): 225-239.

*(This field work has been sponsored by the German National Science Foundation (DFG), Special Research Project: SFB-267)

See also Ichnology Newsletter, 21, p. 34-35.

MARCH 14-17, 2000

Special session: Applications of ichnology to sedimentary facies and basin analysis.

CONVENORS: Luis A. Buatois (CONICET-Universidad Nacional de Tucuman-Argentina) & Renata G. Netto (UNISINOS-Brazil)

This session focuses on the potential of ichnofossils to solve problems in sedimentary geology and genetic stratigraphy, with special emphasis in their use in the petroleum industry. Talks and posters integrating ichnologic data with other lines of evidence (e.g. sedimentary facies, sequence stratigraphy, petrophysics) are particularly welcomed. Although fossil examples are emphasized, there is plenty of room for studies of recent environments and their associated biogenic structures that may serve as modern analogues for the analysis of the stratigraphic record.

Possible topics include: sequence-stratigraphic importance of substrate-controlled ichnofacies, ichnofabric mapping of reservoir zones, paleoclimatic significance of paleosol ichnofaunas, trace fossils and event stratigraphy, bioturbation and reservoir quality, hardgrounds and bioerosion, and trace fossil zonation of lacustrine systems.

Participants should be registered in the congress. For further information on registration, abstract submission, short courses, and field trips, please contact: Sergio Matheos, Centro de Investigaciones Geologicas, Calle 1 nro 644, 1900 La Plata, Argentina, TE (54) (21) 25-8696 ext 39, FAX (54) (21) 25-8696, e-mail: smatheos@cig.museo.unlp.edu.ar

For further information on the Ichnology session, please contact: Luis Buatois, Casilla de Correo 1 (CC), 4000 San Miguel de Tucuman, Argentina, TE/FAX (54)(81) 23-6395 or Renata Netto, Programa de Pos-Graduacao em Geologia, Universidade do Vale do Rio dos Sinos - UNISINO, Av. Unisinos 950, 93022-000 Sao Leopoldo RS, Brazil, TEL (55)(51) 590-8174, FAX (55)(51) 590-8177, e-mail: nettorg@dgeo.unisinos.tche.br

by S. Braddy

Towards the end of the Gondwana-10 meeting, in Cape Town, there was a proposal that the next meeting (c. early 2000) should be held in Antarctica. It was suggested that a Russian research vessel will act as the venue, and the presentations (on board) will be integrated with fieldwork on Antarctica, South Georgia and the Falkland Islands/Malvinas.

Many delegates at the Cape Town meeting expressed various concerns to me on this proposal, particularly: (1) The number of delegates able to attend would be have to be limited (c. 100-120), (2) The cost would have to be quite high, and this would probably exclude many post graduates, (3) Would the ship be able to offer all the facilities necessary for a meeting of this nature?, (4) The weather is likely to be unsuitable (even in the Antarctic summer, the weather can be very changeable, which might delay or prevent the planned field excursions).

On the other hand, those delegates able to attend, would have the opportunity to visit parts of the world that would normally be very inaccessible, and costly, to get to. It was also suggested that this excursion would highlight the importance of Antarctica in Gondwanan studies, and possibly involve the media.

So far, most members of our working group, who have expressed an opinion, suggest that this excursion is a bad idea for the reasons mentioned above. I would like to hear from any members who would like to attend the next Gondwana meeting (wherever it is held), and get your comments on the proposed venue, before I cast my vote (the 20 voting SGS members will vote on the next venue).

by B. Weber

Some words relating to the term "endemic" in the context with the Gondwanan ichnology: In the original biological sense, the word "endemic" means the occurrence of a certain (isolated) biological taxon being clearly restricted to a certain region or territory (esp. islands, lakes or valleys surrounded by high mountains or by any other natural reproduction boundaries), and by that way being isolated from the surrounding neighbourhood of originally genetic equal populations for a long time. The final genetic and evolutionary result could be an "endemic taxon" being incapable to interbreed further on with the individuals of the other related populations.

On the other hand, Gondwana (from the geographical point of view) has been a unique giant super-continent, incomparable with any geographic units which ever existed since the Mesozoic era up to today, - a "poly-cratonic complex" and an evolutionary crucible of enormous dimension! - The question is, whether biological taxa which were living on such a huge geographical unit as Gondwanas coastlines and shelf areas, in relation to their neighbours on the surrounding continental plates, really "endemics" in the original sense of this biological (evolutionary) term.?!

In other words, we have for example many typical and distinct zoological and botanical taxa today in North America, Europe, Africa etc. (and each of these continents today are even much smaller than Gondwana was), but we cannot call for that reason all these thousands of (African, European and North American) taxa "endemic organisms" - Rather, it is more usual to distinguish between different recent (African, North American, European etc.) "faunal or floral provinces" (biogeographic zones etc.). For example, also in the palaeobotanical literature, for the Permo-Carboniferous time, a "Gondwanan Glossopteris-floral province" has been distinguished from another (northern) "Euroamerican-Cathaisian and Angaran" floral province. Considering all these points, I therefore would suggest to be careful with the use of the term "endemic" in the context mentioned.

It is obviously proved by the fossil record that during the Palaeozoic time the shelf environments of Gondwana have been populated by a characteristic Gondwanan (benthic) faunal complex being clearly different from the Laurentian, Baltic or Siberian palaeo-faunal provinces, and therefore (in my opinion) it seems very likely that we have also a typical related "Gondwanan ichnofaunal province".

Seilacher (1970, 1991, 1994) and also Crimes (1968), (references see above), showed that for instance, Cruziana ispp. are very suitable as biostratigraphic markers in "non-fossiliferous" siliclastic sediments. Moreover, Seilacher, (1991) suggested that probably several Cruziana ispp. actually seem to be restricted to peri-Gondwanan occurrences, e.g. several representatives of his Ordovician "Cruziana rugosa-Group" as C. rouaulti and C. goldfussi. So it seems to be very likely that several Cruziana ispp. represent typical ichnotaxa of this Gondwanan ichnofaunal province.