| Saint-Chinian Formation | |
| Type: | Geologic formation |
| Period: | Tremadocian |
| Prilithology: | Shale |
| Otherlithology: | Sandstone |
| Namedfor: | Saint-Chinian |
| Country: |  France |
| Coordinates: | 43.4186°N 2.9454°W |
| Underlies: | La Maurerie Formation |
| Overlies: | La Dentelle Formation |
| Thickness: | around 500 m |
The Saint-Chinian Formation is a geological formation composed of shales with limestone inclusions, dating from the Lower Ordovician (Tremadocian).
It is one of the six geological formations from the Saint-Chinian Cambro-Ordovician basin, comprising, from the most ancient to the most recent : La Dentelle Formation, Saint-Chinian Formation, La Maurerie Formation, Cluse de l'Orb Formation and Setso member, Foulon Formation and Landeyran Formation. This formation outcrops on the southern flanks of the Montagne Noire in Southern France.[1]
The formation received its name from the small city of Saint-Chinian, a commune located in the Hérault department in Occitania.
It is dated from the biostratigraphic sub-zone characterized by Taihungshania miqueli and Asaphelina barroisi berardi.
The thin nature of the silico-clastics deposits, the presence of slump, combined with a trilobite fauna dominated by members of the Asaphidae family indicates a marine environment of external distal platform.[2]
Shales of the Saint-Chinian Formation bears in certain areas accumulations of phosphated nodules, each potentially bearing a trilobite. Those are the so-called "schistes à gateaux"[3] ..
| Genus | Species | Locality | Age | Notes | Images |
|---|---|---|---|---|---|
| Cyclostomiceras | C. thorali | Euloma filacovi Zone | A cyclostomiceratid ellesmerocerid[4] | ||
| Saloceras | S. chinianense | Euloma filacovi Zone | An eothinoceratid ellesmerocerid | ||
| S. murvielense | Euloma filacovi Zone | An eothinoceratid ellesmerocerid | |||
| S. pradense | Taihungshania miqueli acme Subzone | An eothinoceratid ellesmerocerid | |||
| Rioceras | R. escandei | Euloma filacovi Zone ; Asaphelina barroisi berardi and Taihungshania miqueli Subzone | A rioceratid ellesmerocerid | ||
| Felinoceras | F. constrictum | Euloma filacovi Zone | A rioceratid ellesmerocerid | ||
| Annbactroceras | A. martyi | Euloma filacovi Zone | A baltoceratid orthocerid | ||
| A. felinense | Euloma filacovi Zone | A baltoceratid orthocerid | |||
| Bactroceras | B. mourguesi | Euloma filacovi Zone | A baltoceratid orthocerid | ||
| Cochlioceras | C.? aff. roemeri | Euloma filacovi Zone ; Asaphelina barroisi berardi and Taihungshania miqueli Subzone | A baltoceratid orthocerid | ||
| Thoraloceras | T. bactroceroides | Euloma filacovi Zone ; Asaphelina barroisi berardi and Taihungshania miqueli Subzone | A troedsonellid dissidocerid | ||
| Lobendoceras | L. undulatum | Euloma filacovi Zone ; Asaphelina barroisi berardi and Taihungshania miqueli Subzone | A protocameroceratid endocerid | ||
| Genus | Species | Locality | Age | Notes | Images |
|---|---|---|---|---|---|
| Paramegalaspis | P. immarginata | An asaphid[5] | |||
| Asaphellus | A. frequens | An asaphid | |||
| A.? sp. | An asaphid | ||||
| Aocaspis | A. macrophtalma | An nileid[6] | |||
| Geragnostus | G. occitanus | A geragnostid[7] | |||
| G. callavei | A geragnostid | ||||
| G. pusio | A geragnostid | ||||
| Micragnostus | M. languedocensis | A micragnostid | |||
| Trinodus | T. chinianensis | A trinodid | |||
| T. corpulentus | A trinodid | ||||
| T. abruptus | A trinodid | ||||
| T. oviformis | A trinodid | ||||
Members from the Asaphida order and the Asaphidae family are commons :
The Agnostida order is present, with:
Ptychopariida order:
Phacopida order :
| Genus | Species | Locality | Age | Notes | Images |
|---|---|---|---|---|---|
| Arauricystis | A. primaeva | A cornute stylophoran | |||
| A. occitana | A cornute stylophoran | ||||
| Cothurnocystis | C. fellinensis | A cornute stylophoran | |||
| C. courtessolei | A cornute stylophoran | ||||
| Phyllocystis | P. blayaci | A cornute stylophoran | |||
| P. crassimarginata | A cornute stylophoran | ||||
| Thoralicystis | T. griffei | A cornute stylophoran | |||
| Trigonocarpus | T. singularis | A cornute stylophoran | |||
| Chauvelicystis | C. spinosa | A cornute stylophoran | |||
| C. vizcainoi | A cornute stylophoran | ||||
| Galliaecystis | G. lignieresi | A cornute stylophoran | |||
| G. ubaghsi | A cornute stylophoran | ||||
| Amygdalotheca | A. griffei | A cornute stylophoran | |||
| Anatifopsis | A. trapeziiformis | A mitrate stylophoran | |||
| Balanocystites | B. escandei | A mitrate stylophoran | |||
| Peltocystis | P. cornuta | A mitrate stylophoran | |||
| Vizcainocarpus | V. dentiger | A mitrate stylophoran | |||
| Chinianocarpos | C. thorali | A mitrate stylophoran | |||
| Minervaecystis | M. vidali | A solute homoistelean[12] | |||
| Balantiocystis | B. thorali | An eocrinoïd | |||
| Aethocrinus | A. moorei | A cladide crinoïd | |||
| Macrocystella | M. azaizi | A dichoporite rhombifere. Two subspecies are present : M. a. paucicristatus and M. a. multicristata | |||
| Hemicystites | H. boehmi | A edrioasteroïd | |||
| ?Pyrgocystis | ?P. sp. | A edrioasteroïd | |||
| Chinianaster | C. levyi | A goniactinid stelleroïd | |||
| Villebrunaster | V. thorali | A goniactinid stelleroïd | |||
| Ampullaster | A. ubaghsi | A goniactinid stelleroïd | |||
| Pradesura | P. jacobi | A stenurid stelleroïd | |||
Other fossil remains of marine animals are known from the formation:[13]