The 11th Plant Taphonomy Meeting

The 11th Plant Taphonomy Meeting was held in Barcelona (Carles Martín-Closas, Departament d'Estratigrafia i Paleontologia, Universitat de Barcelona), 11th of November 2000.

Table of contents

[*] EDWARDS, D.: Preserving plants in pyrite

[*] EKLUND, H.: Mesofossils from the Late Cretaceous of Antarctica

[*] FERGUSON, D.K.: Painting the broad picture: A plea for a multidisciplinary approach in community reconstruction

[*] FRANCIS, J.: Unusual preservation of silicified wood by quartzine from the Jurassic Purbeck Formation

[*] GOMEZ, B., MARTÍN-CLOSAS, C., BARALE, G., MÉON, H. & THÉVENARD, F.: Plant taphonomy in the fluvio-lacustrine basin of Uña-Las Hoyas (Upper Barremian, Southwestern Iberian Ranges, Spain)

[*] HOWE, J.: Mid Cretaceous fossil forests of Alexander Island, Antarctica

[*] MARTINETTO, E.: Terrestrial plant remains in late Cenozoic shallow marine deposits of the Po Plain (Italy)

[*] MARTÍNEZ-DELCLÒS, X: Taphonomy of amber and its inclusions

[*] Post-meeting field trip


Preserving plants in pyrite

Dianne Edwards
Department of Earth Sciences, Cardiff University, P.O. Box 914, Cardiff CF10 3YE

Pyrite permineralisations are an important source of information on plant anatomy including water-conducting cells in the earliest land plants and woody tissues in Eocene twigs and roots. Detailed analysis of the fabric of pyrite in relation to the quality of preservation in the Devonian and Eocene fossils has allowed elucidation of the processes involved and tentative explanations for the differences in amounts of organic material present in the fossils. A model system using Apium petioles (celery) and the FeS-H2S reaction to produce pyrite was designed to simulate pyritisation in the laboratory. The destruction of microcrystalline pyrite precipitated within cellulose cell walls, cements between cells, and on the inner walls of the cells is consistent with observations of Devonian plant fossils, but we have yet to produce a fully pyritised celery fossil to confound future palaeobotanists.

Mesofossils from the Late Cretaceous of Antarctica

Helena Eklund
School of Earth Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom

The Late Cretaceous (late Santonian) Table Nunatak Formation, Antarctica, has yielded the first Cretaceous mesofossil assemblage from the Southern Hemisphere. Preliminary studies by Jane Francis, and Dave Cantrill and co-workers, have shown that the mesofossils comprise small fragments of wood, fruits, seeds, and leaves. A recently started postdoc project with the aim of studying the fossils in more detail, particularly the angiosperm structures, will hopefully result in taxonomic placement of the fossils. The fossils are preserved as charcoal and many of them have their three-dimensional form retained. In the more well preserved specimens the cell shape is only slightly altered and can be studied in detail using the SEM. During this talk a brief presentation of the variety of fossils documented so far will be given.

Painting the broad picture: a plea for a multidisciplinary approach in community reconstruction

David K Ferguson
Institute of Palaeontology, Geocentre, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria

Just as guidebooks tend to concentrate on certain aspects of a country, and its centres of population, so do most accounts of fossil plant localities only deal with a fraction of the available information. Since the fossil record is by its very nature fragmentary, there is a real danger that by being selective a completely false picture of the former vegetation will emerge. The advantages of combining information from a variety of sources (leaves, sporomorphs, diaspores, wood etc.) are numerous, e.g.:

• a broader picture of the flora emerges (the extra plant parts yield supplementary information)

• the accuracy of the identifications can be corroborated/called into question and alternatives suggested

• differences in representation can be used in the spatial reconstruction of the flora

If possible, other data on the site of deposition and its environs (e.g. sedimentology, palynofacies, phytoliths, diatoms, insect- and vertebrate-remains) should be integrated into such multidisciplinary studies.

It is clear that no one individual can undertake all this work. So how can we accomplish this objective? The solution lies in multidisciplinary teams. However, this is easier said than done. The members of the team must be compatible and be willing to let the common goal take precedence over their individual careers.

Unusual preservation of silicified wood by quartzine from the Jurassic Purbeck Formation

Jane E. Francis
School of Earth Sciences, University of Leeds, Leeds, LS2 9JT, UK

Fossil trees are preserved within Upper Jurassic Purbeck Formation sediments on the south coast of England. Large petrified tree stumps and branches are encased within algal stromatolitic limestones and roots are preserved within calcareous palaeosol horizons. The wood represents the remains of conifer trees that once grew on the shores of hypersaline lagoons, on the borders of the Tethys sea. The wood is generally well preserved and anatomical details are present, suggesting that silicification occurred soon after the death of the trees. Cell walls are preserved by microcrystalline quartz and lumen filled with single quartz crystals. However, secondary recrystallisation has resulted in the formation of large radial fibrous crystals that have displaced organic matter and pushed apart the cell walls. This process has progressed until large rosettes of megaquartz have destroyed all cellular detail in some trees. The unusual feature is that most of the quartz in the wood is a variety of chalcedony called quartzine, which is optically length-slow and has the c-axis of the crystals parallel to the axis of the fibres. Length-slow chalcedony is rare but recently reported from evaporitic sediments. Under conditions of high pH, as would have been present in the Purbeck hypersaline lagoons, the silica solution can precipitate more easily with the c-axis of the crystals parallel to the fibres. In addition, lutecite, another rare form of length-slow chalcedony, is also present within the Purbeck beds as pseudomorphs of gypsum and anhydrite. This unusual mineral can be used as an indicator of semi-arid environments.

Plant taphonomy in the fluvio-lacustrine basin of Uña-Las Hoyas (Upper Barremian, Southwestern Iberian Ranges, Spain)

Bernard Gomez (1), Carles Martín-Closas (2), Georges Barale (1), Henriette Méon (3) and Frédéric Thévenard (1)
(1) Laboratoire de Biodiversité et Évolution des Végétaux Actuels et Fossiles, and FRE CNRS 2042, Université Claude-Bernard Lyon 1, bâtiment 401A, 43, Boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex, France. (2) Departament d'Estratigrafia i Paleontologia, Universitat de Barcelona, 08028 Barcelona, Catalonia, Spain. (3) Centre de Paléontologie, Stratigraphie et Paléoécologie, FRE CNRS 2042 CNRS, Université Claude-Bernard Lyon 1, 27, Boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex, France

Plant cuticle compressions were found in deltaic coaly clays from Uña and in lithographic lacustrine limestones from Las Hoyas (Upper Barremian South-western Iberian Ranges, Cuenca, Spain). The assemblages from Uña were extremely monotonous and formed by the genera Frenelopsis Schenk emend. Watson, Classostrobus Alvin et al. and Glenrosa Watson and Fisher. According to sedimentological and taphonomic analyses, these assemblages originated by fragmentation and size-selection during fluvial transport, and final deposition in crevasse-splay and delta front facies. Our results indicate that the delta of Uña was almost only fed by remains of cheirolepidiaceous conifers living in the upper delta plain of a lacustrine delta. A comparison with the flora found in the open lacustrine facies of Las Hoyas, which are laterally equivalent of the deltaic beds of Uña, shows that land-plant assemblages of Las Hoyas are largely more diverse. The matoniaceous tree-fern Weichselia reticulata constitutes the most abundant land-plant remain and is preserved either as large fronds with articulated pinnae or as small charred pinnules and pinnae. These remains appear to be parautochthonous and indicate that Weichselia reticulata dominated the lakeshore vegetation of Las Hoyas in contrast to the vegetation of the upper delta plain of Uña which was dominated by Frenelopsis. The habitats of Frenelopsis and Glenrosa from the Upper Barremian oligohaline basin of Uña - Las Hoyas are in contrast with the habitats commonly hypothesised for both taxa in coastal marine environments or on saline edaphic profiles.

Mid Cretaceous fossil forests of Alexander Island, Antarctica

Jodie Howe
The School of Earth Sciences, The University of Leeds, Leeds LS2 9JT (British Antarctic Survey CASE Student)

Fossil plants and trees preserved in the Cretaceous rocks of Alexander Island, Antarctica are a crucial source of information on the palaeoenvironment, climate and palaeoecology of these mid Cretaceous fossil forests. They are evidence for warm equable conditions that supported temperate climate vegetation in the polar regions.

The fossil plants and trees are found preserved in sequences of fluvial sandstones, siltstones and palaeosols. Sandstones show features such as in situ fossil tree trunks and leaves, some current bedding and rip-up clasts of the palaeosol below. Thick siltstone units are horizontally laminated and contain an abundance of well preserved plant fossils. This sedimentary sequence represents flood plain and channel bar deposits of a braided river which evolved into a meandering river system. The sandstones were formed during flood events which deposited vast amounts of sand over the riverbanks, covering the soils and vegetation. Signs of deformation in underlying sediments suggest that deposition of the sands was rapid and therefore flood events were catastrophic. The siltstones were formed from suspension fallout in standing water pools. The palaeosols are immature but have an abundance of rootlets and plant material within them indicating that they supported vegetation. The palaeosols represent a period of emergence along a riverbank with enough time for colonisation of plants and trees. Sequences of palaeosols, sandstones and siltstones suggest that when water subsided, new soils formed and plant colonisation began again.

The fossil plant assemblages suggest that a thick canopy of araucarian and Elatocladus conifers with an understorey of ferns and the small shrub Taeniopteris, dominated the vegetation within these Cretaceous fossil forests. Other minor components of the vegetation included liverworts, angiosperms and Ginkgo.

Terrestrial plant remains in late Cenozoic shallow marine deposits of the Po Plain (Italy)

Martinetto, E.
Dipartimento di Scienze della Terra, Via Accademia Scienze 5, 10123 Torino, Italy

Late Cenozoic very shallow marine sediments crop out in the western and southern part of the Po Plain. They sometimes contain beds rich in terrestrial plants, either well-preserved leaf impressions or weakly coalified mega/mesofossils, including fruits and seeds which can be readily identified. A dozen of sites have been examined from the palaeobotanical point of view during the last decade, and two case studies will be presented here. The first one is the nearly 300 m thick Cervo River section in the NW Po Plain, which, on the ground of floristic composition of plant assemblages, seems to cover with many gaps a time interval between Early Pliocene and Late Pliocene (possibly also Early Pleistocene). The sediments are mostly shallow marine sands, part of which show sedimentary structures of tidal origin. Several layers with fruits and seeds («carpoids») of terrestrial plants and one yielding a diverse assemblage (ab. 50 taxa) of leaf impressions have been studied. The «carpoids» always show different size classes, from a few millimetres to several centimetres (Pinus cones), the smallest ones being usually remarkably well preserved, while the degree of abrasion of the biggest ones is variable even in the same species; interestingly, a few cones are bored by Teredo. The leaves are mostly reduced to small fragments, however a few irregular surfaces, for not more than 5 metres of lateral extension, are covered by almost complete leaf sheets, which are often folded and chaotically disposed within the sediment. The usually large-leafed taxa are only represented by small-sized specimens or fragments of big ones. Fragmentation and imperfect state of preservation of leaves (cuticles are absent) often hamper their systematic determination.

The second case study is represented by the succession of Oriolo (nearly 20 m thick) in the SE Po plain, near Faenza, which should be chronostratigraphically located at the Matuyama/Brunhes boundary. Here a rich collection of reddish leaf impressions (and a few fruits and seeds) was gathered by Dr. M. Sami. The leaf assemblages originate from a few silty layers with chaotically disposed leaf sheets. Several samples contain mainly whole leaf specimens, suggesting that fragmentation during transport has not been dramatic. Most specimens show distinctive leaf architectural features, which permit to assign them to about three dozens of taxonomic groups, most of them still living in Italy.

Obviously, the leaf and «carpoid» assemblages of both study sites experienced a consistent transport that could have biased the composition. However the palaeoenvironmental setting of both sites was characterised by inclined slopes very close to the coastline, with a rather narrow coastal plain in between, so that plant remains did not need to be transported more than a few thousend metres. Such assemblages may be interpreted as masses of continental plant brought by rivers into the shallow-sea during distinct flood events. Individual «carpoids» obviously floated in the sea for several weeks (months?) before burial, because they were colonised by Teredo. On the other hand, due to the presence of delicate leaves, it seems improbable that their floating time in the sea would be as long; yet very rare specimens encrusted by balanids and bryozoans were found in other Pliocene sites of the western Po Plain. In order to reconstruct the area and the vegetation types which were sampled by the transport agents, the best tool seems to be an ecological analysis based on nearest living relatives, especially for the Pleistocene of Oriolo. In this site several living taxa distinctly indicate a riparian forest; other forms indicate a floodplain forest and a slope forest, likely associated with clearings yielding shrubby vegetation. Even for the Cervo River leaf flora there are some indications of such a broad vegetation sampling. The carpological assemblages invariably indicate a main provenance from well-drained terrestrial environments, but is difficult to say from how many vegetation types because most species are extinct. Less common taxa prove that also freshwater wetlands (Proserpinaca) and marine seagrass communities (Cymodocea) had been sampled. Of course, a sound actuopalaeontological analysis of analogous taphocoenoses will be the key to get more information from this rich and diverse kinds of fossil assemblages.

Taphonomy of amber and its inclusions

Martínez-Delclòs, X.
Departament d'Estratigrafia i Paleontologia, Facultat de Geologia, Universitat de Barcelona, 08028 Barcelona (Catalonia, Spain)

Insects embedded in amber constitute the main subject of study of amber specialists. As a matter of fact, only a few palaeobotanical studies have been devoted to the taphonomy of amber and palaeoenthomologists must confront the taphonomy of plants alone, even if they are unfamiliar with the subject at the beginning. One example may illustrate the interaction between plant and insect taphonomy in amber: insect taphonomy begins when the insects are trapped by the resin, but the resin itself already has entered its taphonomical history before.

Amber is a natural fossilized resin exuded by a large diversity of trees, especially some groups of conifers and angiosperms. Today these large resin producers are mainly distributed in the tropical and temperate forests and savannah, and they are largely used by the wood industry, chemistry and pharmacy. Resins are a complex mixture of terpenoid compounds, the more common ones are oxygenated terpenes, such as acids, alcohols, and esters, secreted from plant parenchyma cells. Terpenes may be volatiles at normal environmental temperatures but in particular cases they are not. The latter are the most significant for us since they transform into amber after milions of years of diagenesis, while volatiles are gradually lost in that time.

After resin secretion a number of processes including oxidation and polymerization occur; resin becomes harder in a short time to form a product known as copal, which may reach ages of up to a few thousand years. Copal has different physical and chemical features than amber, which needs some millions of years to be formed.

When does amber taphonomy begin? It is obvious that in the case of arthropod or other animal inclusions, the taphonomic processes begin when they are trapped by the sticky resin, but this is more difficult to decide in the case of their "matrix" (the amber). The boundary between biostratinomy and diagenesis is also different for insects and the amber itself. Whereas foramber inclusions, diagenesis begins when they are totally embedded in resin, this boundary is not as straightforward for the amber. Does it begin with the polymerization of terpenes or rather when the resin is buried in sediments ?, what about the resin secreted by roots ?

These questions may be answered after reviewing the formation of resins in trees. Resins may form in internal crack fillings, under the bark, in resin pockets in the wood, in pockets between the bark, as fillings from tree wounds, as external stalactite shapes, as stalactites, as external drops and swellings. Not only resins are usually related with the bark or wood but also with roots, leaves, etc. It is necessary to say that one species of tree may produce diverse types of resins, with different chemical compositions and obviously different rates of decomposition. For example Agathis australis (Araucariaceae) produces at least 5 different types of resin. All these features determine the future amber formation, and the preservation of inclusions.

In this workshop a number of crucial topics for the taphonomic history of amber may be discussed:

a) Resin production and their producers. What kind of trees produce today large quantities of resins ? Differences between their recent distribution and their distribution in the fossil record should be taken into account.

b) The drying of resin. During this event a large quantity of animal and plant remains may stick in resin. Are the organism remains found embedded in amber selected in a certain extent? This may condition the palaeoenvironmental and palaeoecological reconstructions made from amber remains.

c) The transport of resin until its final depository. Are the amber deposits mainly autochthonous or allochthonous ? Which sedimentary environments are more favourable for the preservation of resin?.

d) Diagenetic processes that affect resin and their biological content. Is the original composition of inclusions preserved in ambers? Why do we study the palaeobiological content by transmitted light microscopy (through the amber)? and why do we not extract it?

We may try to answer these questions during my talk, but there are other questions I would like to discuss together with all participants, as for example: why does a large quantity of amber localities occur around the world but only a few of them have palaeobiological content?

Post-meeting field trip: Plant Taphonomy in La Cerdanya Basin (Upper Miocene, Pyrenees)

Geological Setting

The semi-graben of La Cerdanya is located in the Axial Zone of the Eastern Pyrenees at an altitude of about 1100 m. The origin of this graben can be traced to the Late Miocene strike-slip movement of La Tet Fault, which cut the Eastern Pyrenees from ENE to WSW. As a result, a small (35 km long and up to 7 km at its widest point), clearly asymmetric basin was formed (Pous et al., 1986; Cabrera et al. 1988).

During Vallesian (Late Miocene) La Cerdanya recorded up to 800 m of fluvio-lacustrine sediments. Conglomerates, sands, and silts were deposited in alluvial fans; sands, silts, and lignite seams were deposited in fluvial plains and deltaic swamps, and lutites and diatomites accumulated in a lacustrine setting. Limnological studies showed that the lake was deep and meromictic. Sedimentological and geochemical data demonstrated that water stratification resulted in low-oxygenation conditions, preservation of lacustrine varves and high organic content at the lake bottom (Anadón et al. 1989; de las Heras et al. 1989).

Paleobotanical setting

Since the late nineteenth century, when Rérolle (1884-1885) first studied the fossil plant remains of La Cerdanya, the basin has been the subject of many paleobotanical and palynological studies (e.g. Baltuille et al. 1992; Barrón 1995, 1997; Haworth and Sabaté, 1993). About 100-150 species of plants have been recognized from their macroremains, pollen and spores.

During the Miocene, a vegetation zonation was apparent due to altitude change in La Cerdanya. Álvarez-Ramis & Golpe-Posse (1981) defined plant assemblages related to this zonation. The vegetation around the lake was a mixed, polydominant, montane forest composed of oaks, beeches, and fir with other elements, such as maples, elms, birch, chestnut and lime. Some relict thermophilous elements such as laurels, the bald cypress, and even palms, are occasionally found but these were probably never abundant in La Cerdanya. This vegetation is consistent with the higher altitude of the Pyrenean lake and contrasts with the Miocene vegetation of the Catalan coastal basins, which included a larger number of thermophilous and xerophytic elements, mainly legume trees. The lake itself was bounded by a helophytic belt formed by Poaceae, Cyperaceae and Typha, and a hydrophytic vegetation dominated by Trapa, pond-weeds and Ceratophyllum. Diatoms and planctonic chlorophytes dominated the open lake.

Plant taphonomy

Plant taphonomy has attracted the interest of authors in recent years (Barrón, 1995; Martín-Closas, 1995) The latter author recognized four plant macroremain taphofacies and discussed their distribution in the basin. Recent, still unpublished results, add new information about the palynofacies of the basin.

Deltaic-palustrine lutites include assemblages of autochthonous aquatic plant megaremains such as reed stems (Poaceae, Cyperaceae) and water-chestnut fructifications (Trapa). Layers with this taphofacies may present rootlet marks. Another taphofacies, found in lignites interbedded with previous lutites, is an assemblage of allochthonous remains. They include floated stems of helophytic plants, which are sometimes recognizable in roof shales of lignite seams. Palynofacies of the palustrine belt are highly diverse in composition. Characteristic components include brown wood, structured organic matter (cuticles), zygospores and dense palynomorphs such as spores of Osmundaceae.

Two mega-remain taphofacies were recognized in the lacustrine area. Highly diverse assemblages of leaves, stems, and fructifications with evidence of tearing and fragmentation during stream transport coexist with well-preserved remains, which were transported by the wind. Hydrophytes and helophytes also may be present. This was the dominant plant taphofacies along the northern, western, and eastern lakeshores, which were shallower, gently sloping, and received a number of inlets. Another taphofacies includes land plant remains mainly blown by the wind. This taphofacies is characterized by well-preserved leaf- and winged-seed assemblages without evidence of mechanical breakage. It has a more distal character in comparison to the former plant taphofacies and is located along the deeper, southern margin of the paleolake.

Palynofacies found in lacustrine diatomites are also dual and correlate well with geochemical results (especially Hidrogen Index) but do not show a good correlation with mega-remain plant taphofacies. A palynofacies with dominance of anemophyllous pollen taxa (especially well preserved Alnus and torn bisaccates) and the chlorophyte Botryococcus is largely distribuited in the whole lake. Only in the central lake, sediments another palynofacies occurs, which shows abundant amorphous organic matter and is sapropelic in origin, as indicated by high hydrogen indexes (HI).


Álvarez-Ramis, C. & Golpe-Posse, J.M. 1981: Sobre la paleobiología de la cuenca de La Cerdanya (Depresiones Pirenaicas). Boletín de la Real Sociedad Española de Historia Natural. Sección Geológica 79, 31-44.

Anadón, P., Cabrera, L., Julià, R., Roca, E. & Rosell, L. 1989: Lacustrine oil-shale basins in Tertiary grabens from NE Spain (Western European Rift System). Palaeogeography, Palaeoclimatology, Palaeoecology 70, 7-28.

Baltuille, J.M., Becker-Platen, J.D., Benda, L. & Ivanovic-Calzaga, Y. 1992: A contribution to the subdivision of the Neogene in Spain using palynology. Newsletter Stratigraphy 27, 41-57.

Barrón, E. 1995: Estudio tafonómico y análisis paleoecológico de la macro y microflora miocena de la cuenca de La Cerdaña. Unpublished Ph.D.Thesis, Universidad Complutense de Madrid, 773 pp.

Barrón, E. 1997: Estudio palinológico de la mina de lignito Vallesiense de Sanavastre (La Cerdanya, Gerona, España). Revista Española de Micropaleontología 29, 139-157.

Cabrera, L., Roca, E., & Santanach, P. 1988: Basin formation at the end of a strike-slip fault: the Cerdanya Basin (Eastern Pyrenees). Journal of the Geological Society, London 145, 261-268.

De las Heras, X., Grimalt, J.O., Albaigés, J., Julià, R. & Anadón, P. 1989: Origin and diagenesis of the organic matter in Miocene freshwater lacustrine phosphates (Cerdanya Basin, Eastern Pyrenees). Organic Geochemistry 14, 667-677.

Haworth, E. Y. & Sabaté, S. 1993: A new Miocene Aulacoseira species in diatomite from the ancient lake in La Cerdanya (NE Spain). Nova Hedwigia, Beiheft 106, 227-242.

Martín-Closas, C. 1995: Plant Taphonomy of La Cerdanya Basin (Vallesian, Eastern Pyrenees): Geobios, M. S. 18, 287-298.

Pous, J., Julià, R. & Solé-Sugranyes, L. 1986: Cerdanya Basin: Geometry and its implications on the Neogene evolution of the Eastern Pyrenees. Tectonophysics 129, 355-365.

Rérolle, L. 1884-1885: Études sur les végétaux fossiles de La Cerdagne. Revue de Sciences Naturelles de Montpellier 3ème Série 4, 167-191, 252-298, 368-386.

Riba , O., de Bolós, O., Panareda, J.M., Nuet, J. & Gosalbez J. (1976): Geografia física dels Països Catalans, Ketres Editora226 p., Barcelona.

Solé Sabarís. Ll. (1958-1971): Geografía de Catalunya, Editorial Aedos, Barcelona.

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