C., M., J. & P. (2007).- Strud: old quarry, new discoveries. Preliminary report. In: P. & E. (eds.), Recent Advances in Palynology.- Carnets de Géologie / Notebooks on Geology, Brest, Memoir 2007/01, Abstract 07 (CG2007_M01/07)
Famennian; biostratigraphy;
fossil plants; Strud.
Famennien ;
biostratigraphie ; plantes fossiles ; Strud.
The Strud
quarry is located in the uppermost levels of the Dinant Synclinorium, Belgium.
It exposes a part of the Upper Famennian
(Upper Devonian) "Condroz sandstones", composed mainly of fine-grained,
more or less micaceous, arkosic sandstones interlayered with thin shale or
siltstone beds and, but rarely, with dolomite beds (these may occur either as
evaporites or as immature dolcrete) ( & ,
1986).
In Belgium, most of the
fossil-bearing beds in "Psammites du
Condroz" are found in the Evieux Formation (,
1996). The quarry was first investigated by
(1878). He mentioned only the presence of remarkably well-preserved specimens of Rhacophyton condrusorum , 1875. , in 1948, published a monograph on the Upper Devonian plants of Belgium. He described several localities, including
Strud. The aim of the present study is to update the data set concerning Strud and to date the
quarry correctly.
The Strud quarry has
been recently and densely sampled for miospores. Two samples have provided
a miospore association that preliminary study has indicated surprizingly to be the
Lower GF spore biozone characterized by Grandispora gracilis- Grandispora famenensis.
Commonly, this biozone dates the Monfort Formation which in other areas of the Dinant
Synclinorium lies below the Evieux Formation. Here, the Evieux Formation is
dated by the slightly younger VCo (versabilis cornuta) biozone and by the
lithology described above.
Taking into
account the actual Strud lithology and its miospore association, one may
conclude that the sequence exposed in the quarry is in reality facies of an Evieux
type and does correspond biostratigraphically to the Evieux Formation as was
thought previously: the data clearly demonstrate that the Evieux facies has a
diachronous character dependent on Upper Fammenian palaeogeography ( et alii, 2006).
The quarry has yielded various fossil remains. An important vertebrate assemblage including a mandible of the early tetrapod Ichtyostega (
et alii, 2004) has been found. The palaeozoological material found in the quarry is currently
under study by Gaël (Museum d'Histoire
Naturelle, Paris).
The outcrop has also yielded plant remains. The first collection
was made by F. before 1950 and is housed at the
Institut Royal des Sciences Naturelles de Belgique. The fossils are preserved as strongly oxidized,
red- to brown-coloured compressions. The state of preservation does not allow any anatomical study.
The second collection
(Pl. 1, figs. 1-7 
) is newly collected material and is housed in the collections of the University of Liège. The plants are
less well-preserved than the older specimens. This can be explained by the fact that the Strud quarry has not been exploited for more than 100 years. The outcrop has thus been exposed to weathering processes for a long time.
's floristic index
mentions 5 taxa for the quarry. All are classical members of the
"Evieux flora" (, 1948; ,
1996). This index is summarized in
Table 1 .
The new collection increases the floristic index of the locality to 9 taxa
(Table 2 ). It shows the presence of nearly all important upper Devonian plant groups:
Progymnosperms, Ferns, Gymnosperms and Barinophytes.
Archaeopteris remains are the only representatives of this group
(Pl. 1, fig. 1 ). In contrast with a
number of Belgian localities (,
1996), Archaeopteris remains are rare at
Strud. Only three fragments have been recovered. The organisation of their axis and the shape of their leaves are characteristic of the species Archaeopteris roemeriana () sensu ,
1948. This species should probably be synonymised with Archaeopteris halliana () ,
1871 (
et alii, 2001).
This group is represented by Rhacophyton condrusorum
(Pl. 1, fig. 4 ). It
was the first plant to have been described from the quarry (,
1878). The remains of this plant consist of large rachis without fertile parts or vegetative endings. In other beds from the same quarry,
(1878) described very fine and well preserved Rhacophyton fertile parts.
They consist of three different
taxa: Moresnetia zalesskyi , 1948, emend. et ,
1987 (Pl. 1, figs. 6-7 ), Condrusia rumex ,
1948 (Pl. 1, fig. 3 ) and Pseudosporogonites hallei ,
1948 (see , 1948, Pl. XI, fig. 18). Moresnetia and Pseudosporogonites dominate this assemblage.
Based on megafossils only, the locality is attributed to Famennian biozone number 7 of et alii
(2000). If a palynological age of mid GF is confirmed, the locality would represent the earliest occurrence of cupulate early seed plants, if we
exclude the poorly understood Russian Moresnetia mentioned by
(1988) in the OG Russian Frasnian miospore zone.
The greatest diversity
among the plants observed in the quarry is found in the spermatophytes, represented by 3 very different genera: the classical Moresnetia zalesskyi, and the less well-known Condrusia rumex and Pseudosporogonites hallei.
These three seed-plant genera illustrate a wide range of morphological variation both
in the cupule and in the integument ( & ,
1987; ,
2005; et alii,
2006a), representing three distinct architectural schemes (,
1999; ,
2005).
Such diversity in a group suggests a long evolutionary story. The origin of seed plants is thus presumably to be found earlier in the geological record. The description of the proto-seed Runcaria heinzellinii (
et alii, 2004), the discovery of a highly diversified Givetian megaspore assemblage ( et alii,
2006b; de
et alii, 2007) and the two seed megaspores Spermasporites allenii et ,
2003 and Granditetrasporites zharkovae et ,
2003 are all supplementary indications of the probable Middle Devonian origin of the seed plant lineage.
We wish to express our gratitude to Gaël and his team for
their help when we collected the plant fossil material. We are indebted also to the IRSNB in the person of F. . We warmly thank M.
(Liège) for the preparation of palynological slides.
A.D. & E. (2003).- New dispersed seed-megaspores from the mid-Givetian of European Russia.- Review of Paleobotany and Palynology, Amsterdam, vol. 127, n° 1, p. 45-58.
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J.W. (1871).- The fossil plants of the Devonian and Upper Silurian formations of Canada.- Geological Survey of Canada, Montréal, 923 p.
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| Zosterophyllopside | Gymnospermes | ||||
| Barinophyton citrulliforme | Moresnetia zalesskyi | ||||
| Filicopside | Pseudosporogonites hallei | ||||
| Zygopteridale | Incertae sedis | ||||
| Rhacophyton condrusorum | Cf. Calathiops sp. | ||||
Click on the table to open a new window.
Table 1: Paleofloristic assemblage of Strud as described by (1948).
| Progymnospermes | Gymnospermes | ||||
| Archaeopteris roemeriana | Moresnetia zalesskyi | ||||
| Zosterophyllopside | Pseudosporogonites hallei | ||||
| Barinophyton citrulliforme | Condrusia rumex | ||||
| Filicopside | Incertae sedis | ||||
| Zygopteridale | Cf. Calathiops sp. | ||||
| Rhacophyton condrusorum | Sphenopteris flaccida | ||||
| Sphenopteris modavensis | |||||
Click on the table to open a new window.
Table 2: Paleofloristic assemblage of Strud as determined in this work.
Click on thumbnail to enlarge the image.
Plate 1:
figure 1. Archaeopteris roemeriana () , ULg n° 15201, scale: 0.5 cm.
figure 2. Sphenopteris modavensis 1948, ULg n° 15221, scale: 1 mm.
figure 3. Condrusia rumex , ULg n° 15222, scale 1 mm.
figure 4. Rhacophyton sp. , ULg n° 15203, scale 1 cm.
figure 5. Sphenopteris flaccida 1948, ULg n° 15215, scale 5 mm.
figures 6-7. Moresnetia zalesskyi , ULg n° 15216 and 15217, scales 0.5 mm.
