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b. STOP n° 4 : on fossiliferous sandstones rills of the Salagou Formation (JG).

In the Lodève Basin, flora, invertebrate and vertebrate remains (fish, amphibians, reptiles) have been collected principally from the base of the series in the grey formations F1 – F2, L1, L2 (fig. 4 A). Higher up various traces of biological origin are found in the red facies which start at Formation F2. L3. Vertebrate tracks are common in the Autunian Group but become scarcer in the Saxonian where they are located mainly at the base (F13 of the Rabejac Formation) and at the top (F17 of the Salagou Formation, fig. 4A). Because several metres of deposit are devoid of fossils between the two Formations, it has been accepted that the Saxonian was virtually azoic due to the arid climate prevailing at the time of deposition.
In fact the examination of Dr LAPEYRIE’s collection painstakingly assembled over some twenty years, shows that this was not the case as so many fossils were collected throughout the Saxonian from formations F29 to F20 (fig. 4). These sites are small siltstone rills and lenses located in the argilite portion of the binary sequences that are terminated by volcanic carbonate siltstone horizons.

* The fossiliferous rills : structure and origin (JG ; fig. 13)

On the vertical section of a typical rill (figure 11), one distinguishes three parts. The upper part is widened in the form of a U or V-shaped and corresponds to the rill sensu stricto. The U-shaped is more resistant ; it is generally found intact while the V-shaped rill is dislocated into ‘plaquettes’. The lower part is more narrow and more or less rectilinear ; in some cases it resembles a plant root or an hydrothermal vein. The intermediate zone between the two parts is well marked by the collar. Often the rill is identifiable from some distance. It is of a clear green-grey color and contrasts clearly on the red brown argilite background.

Fig 13 –: fossiliferous siltstones rill type in mudstones seen near « le Saut des Vaches »

In transverse section, rills appear as sedimentary bodies of small dimensions. Most of the U-shaped rills are isodiametrical (10 cm or a little more) whilst the V-shaped rills are wider than high. Sometimes one rill can exceed one meter in overall directions. On the other hand, the lower part or ‘root’ is disproportionate, reaching 2 to 4 m in height for a width not exceeding 10 cm. In the lower parts in the form of ‘veins’ the difference is even greater ; on the site of Vignasses, veins are 2 to 4 cm wide and 2 m high. And once out two, the root or the vein does not exist.
In its horizontal plane, the rill is longer than broad and when observable, the visible length may reach ten meters. Exceptionally the main rill of the Vignasses site measures 86 m. The U- and the V-shaped rills correspond to clearly distinct deposits.
The U-shaped rill is constituted of siltites with a little or no graded bedding. It contains green clay chloritic pellets and various intraclasts. It is a microbreccia with rudimentary cross bedding and is often very resistant and shows no evidence of stratification ; it is rich in recrystallized carbonates .
The V-shaped rill is formed of finely graded siltites. When the sediment is grey green, there is a clear stratification with a ‘rubanement’ underlined by the darker kerabitume. When the sediment is reddish, the bedding is less visible but under the microscope mm-scale laminations are visible. The ‘rubanement’ results in a fragmentation into slices or ‘plaquettes’ recognizable by their curved form and their shiny surface.
Sediments of the root are identical to those of the upper part. Siltites can be homogeneous and well graded. However, in the deepest roots, the granularity can vary a lot. When granularity is coarse, the ‘rubanement’ disappears and then the clayish cement gives little consistency to this structure. Sometimes, red argilitic joints connect to the enclosing sediment.
In the veins, the siltites are red and more resistant. Bedding is clearly concave and connected to the enclosing sediment. By intervals, there are varnished joints corresponding to a deposit of whitish phyllitic (clays) or reddish (ferric oxides) minerals. Therefore there has been deposits of silts along the entire thickness of the vein.

* Paleontological contents

• Conchostracans (after JS in GAND et al 1998 and new data).
Conchostraca have been found in many levels starting at the base of the section in the Usclas et St. Privat Formation up to the lower part of the La Lieude Member. The conchostracans of the northern Pangea are still in revision (Goretzki, TU Freiberg, Germany). For the moment, some first conclusions are suggested. The up to now distinguishable species from Salelles and Arieges seem to be somewhat higher developed compared with the conchostracans from the Upper Rotliegend I Tambach fm. and (see MARTENS 1983) Müritz fm. (Sakmarian/Artinskian ; see SCHNEIDER in HOFFMANN et al. 1989, SCHNEIDER et al. 1995a) in Germany. One form from Arieges is possibly derived from Lioestheria andreevi, known e.g. from the Tambach fm. The amphibian Seymouria sanjuanensis in the Tambach fm. is typical for the Wolfcampian of North America (SUMIDA et al. 1996). Specimens from Sallèles could be compared with Isaura harveyi Tasch, 1958 and Palaeolimnadiopsis brevis Raymond, 1946 of the Wellington fm., Leonardian of Kansas. Most interestingly, conchostracans are found immediately below and above the basal fanglomerates of the La Lieude fm. The 3 mm to 5,5 mm large forms show a delicate meshwork between the growing lines – a feature typical for mesozoic conchostracans. This points eventually to a latest Permian age – Lopingian. Resulting from this, the profile from the base of the Rabejac fm. up to La Lieude fm. could cover the time span from the higher Lower Permian Artinskian up to the Upper Permian Changxingian.

• Triopsids (GAND et al. 1997 ; fig. 14 ; GG)
After observation of thousands of carapace and thoraco-abdominal fragments and more rarely from intact specimens, we have identified and described two species : Triops cancriformis permiensis and Lepidurus occitaniacus which are morphologically similar to modern species.
On the basis of the ecological preferences of modern Triopsids and the sedimentological characteristics of their environment in Permian times, we have confirmed the occurrence of shallow, temporary expanses of water during the deposition of the Salagou Formation. These pools were either neutral or slightly alkaline and were scattered across a playa type environment and endured with the same characteristics during deposition of the formation which is 2000 m thick in the south of the basin.
Aridity that prevailed during this long period of sedimentation had been suggested earlier from the study of sedimentological data (desiccation cracks, rubefaction)

Fig 14 AI : Triopsidés, A-D: carapaces avec A, C, D = vue interne, B = vue externe; E-H : telson et cercopodes de Triops cancriformis permiensis; F-G: plaque supra anale de Lepidurus occitaniacus; I: Triopsidé carapace + abdomen; mire = 1 mm; Légende des sigles: a. a = anneaux abdominaux, a. c = attache corporelle, ar. = membrane articulaire, a.t = anneaux thoraciques, ap.a = appendices abdominaux ou pléopodes, ap.t = appendices thoraciques ou péréiopodes, ap.t.e = appendices thoraciques endites, ar.= membrane articulaire, b.c = bord de la carapace, c. = carapace, c.a ou b.a.c = bord antérieur de la carapace, ca. = carène, ce. = cercopode, f = furca, f.a.t = flagelle ou épipodite d’un appendice thoracique, f.t = froissement du tégument, g.b = gnathobase, g.c= glande cémentaire, l. = labre, Md = empreinte basale de la mandibule, m.e = moulage externe, m.i = moulage interne, Mx = empreinte basale des mâchoires, o = ornementation, o.o.n = organe nuccal, p.c = pliure de la carapace, p.s.a = plaque supra-anale, p.s.f = plaque subfrontale, r = sens du recouvrement des anneaux, s.t = sillon transversal, t = telson, y.c = yeux composés; different parts of Triopsids body, A-D = carapace, E-F= telson and cercopods of Triops cancriformis permiensis, G-H = supra-anal plate of Lepidurus occitaniacus, I = carapace + abdomen of Triopsid.

Fig 14 JL= moulages de différentes parties corporelles de Triopsidés ; J = vue ventrale de la carapace et de l’abdomen ; K = vue dorsale de Triops cancriformis permiensis ; L = essai de reconstitution de Lepidurus occitaniacus.. J-L. Triopsids : different casts ; J = ventral view of carapax and abdomen ; K = dorsal view of Triops cancriformis permiensis ; L = attempted partial reconstruction of Lepidurus occitaniacus (after Gand et al. 1997) ; Main acronyms : a.a = abdominal metamere, a.t = thoracic metamere, ap.a = abdominal appendages or pléopods, ap.t = thoracic appendages or pereiopods, ap.t.e = endites, ar. = articular membrane, b.c = carapace edge, c. = carapace, c.a ou b.a.c = subfrontal plate, ca. = median keel, ce. = cercopod, f = furca, f.a.t = thoracic appendage flagellum or epipodite, g.b = gnathobase, g.c= maxillary gland, l. = labrum, Md = mandible, m.e = external cast, m.i = internal cast, Mx = maxilla, o = ornementation, o.o.n = dorsal organ, p.c = folding carapace, p.s.a = supra-anal plate, p.s.f = subfrontal plate, s.t = transversal furow, t = telson, y.c = compound eyes

• Insects. (AN, JS, OB, JL).

° Blattodea (JS).
Abundant Blattodea, among them five species of Phyloblatta and one Opsimylacris species are recognized, similar to those observed at the Obora locality in the Boskovice Furrow (Czech) and the Wellington fm. of Kansas (SCHNEIDER, 1980, 1984a,b). Fragments of about 2 cm long fore-wings from Arieges show first indications of a v-shaped cross-venation pattern, which is typical for the genus Aisoblatta, which appears possibly first in the uppermost Kungurian and is typical for the German Zechstein and the Upper Permian of China (see SCHNEIDER, 1983, 1996). Blattoid insects of the Salagou fm. indicate a Kungurian to lower Lopingian age. The La Lieude fm. could therefore be of higher Lopingian age.

° Others insects (OB, JL, fig. 15).
The fossil-bearing strata are distributed between F30 and F20 (fig. 4). The entomofauna is known from 350 specimens, and appears very diverse, although not very abundant. Around twelve orders are represented, 3 for Palaeoptera (Palaeodictyoptera, Odonatoptera, Diaphanopterodea), 9 for Neoptera (Blattaria, Orthoptera, Glosselytrodea, Neuroptera, ‘Protorthoptera’, Caloneurodea, Miomoptera, Protelytroptera, Hemiptera). Four other Insects of uncertain affinities represent unknown families or orders.
The following insects were described from the Salagou Formation ; Lapeyria magnifica NEL et al. 1999 (Odonatoptera : Panodialata : Lapeyriidae) ; Epilestes gallica NEL et al. 1999 (Protozygoptera : Permolestidae) ; Lodevia longialata NEL et al. 1999 (Protozygoptera : Permepallagidae), Saxonagrion minutus NEL et al. 2000 (Odonatoptera : Panodonata : Zygoptera : Saxonagrionidae) ; Orthoptera : Tettigoniidea ; Glosselytrodea (BETHOUX et al., under press).

Fig 15–; Insects wings from the Salagou Formation ; A and B = Lapeyria magnifica, Odonatoptera, Panodialata, Lapeyriidae ; C = Epilestes gallica, Protozygoptera Permolestidae ; D = Lodevia longialata, Protozygoptera Permepallagidae ; E = Saxonagrion minutus, Odonatoptera, Panodonata, Zygoptera, Saxonagrionidae.

The Odonatoptera are mainly ‘Meganisoptera’ with several new species of Meganeuridae : Typinae. The Protozygoptera are represented, though less abundant than the Typinae, the Permian suborder Protanisoptera is still unknown in these outcrops.
The Blattodea : Phyloblattidae are abundant. At least, five species of Phyloblatta could be recognized, similar to those observed in the Boskovice Trough (Czech) and in Kansas (SCHNEIDER, 1983). The same strata also contain a representative of a yet unknown order which seems to be the sister group of Isoptera. This could be the earliest representative of the isopteran lineage which was recorded by HASIOTIS and DUBIEL (1995) after a nest from the Triassic deposits of Arizona.
Orthoptera are represented by several undescribed families and species. Hemiptera occur in the shape of a ‘cercopoid-like’ wing and a Cicadomorpha : Prosbolidae, the latter being already known from the Late Permian of Russia and Siberia. The same is true for Protelytroptera which are reported for the first time in France.
The Endopterygota include several species of Mecopterida and Neuroptera. Oddly enough, the Coleoptera, Raphidioptera, Megaloptera have still not been found in Lodève basin sites whereas they exist in the Early and Middle Permian of Siberia and the USA. It remains to be proved whether their absence is real, and if so whether this is related to an unfavorable paleoenvironment or to conditions of fossilization.
Taphonomy
At present, the entomofaunal material is almost entirely limited to wings, which are frequently fragmented. The body remains found in rills/channels are those of adult specimens.
Generally, after the dislocation of an insect, wings are the best recognisable and collectable remains, because of spreader failure plan. Current taphonomic hypothesis concerning the Salagou formation predicts that animals were dislocated before fossilisation and exposed for variable time, in areas close to sites of fossilization. After that, sedimentological events concentrated insects in rills/channels. Possibly they were concentrated by rain and wind or running water accumulating organic remains in small depressions during drying periods.
The absence of larvae, in spite of numerous remains of Odonatoptera, could have several possible reasons. First, they may have grown in different areas. Second, fossiliferous events may have been seasonal when larvae were absent, but this seems unlikely because different insect larvae are developing during all year among extant forms. Third, the delicate bodies of insect larvae may have been more easily destroyed by necrophagous organisms than adults