Saint-Chinian Formation

{{Infobox rockunit

| name = Saint-Chinian Formation

| image = Geragnostus mediterraneus CRF.jpg

| caption = Geragnostus mediterraneus

| type = Geologic formation

| age = {{fossilrange|Tremadocian}}

| period = Tremadocian

| prilithology = Shale

| otherlithology = Sandstone

| namedfor = Saint-Chinian

| namedby =

| region = {{Flag|Occitanie}}

| country = {{flag|France}}

| coordinates = {{coord|43.418624|N|2.945366|E|source:wikidata}}

| paleocoordinates =

| unitof =

| subunits =

| underlies = La Maurerie Formation

| overlies = La Dentelle Formation

| thickness = around 500 m

| extent =

| area =

| map = {{Location map+ | France

| relief = 1

| width = 250

| float = center

| places =

{{Location map~ | France

| lat_deg = 43.418624

| lon_deg = 2.945366

| mark = Cyan pog.svg

| marksize = 12

}}

| map_caption =

}}

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.{{cite web|title=L'Ordovicien du bassin de Saint-Chinian|website= Excursion ASNAT|date= 21 September 2019|url= https://asnat.fr/pdf/saint-chinian_ordovicien2019.pdf}}

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.

Paleoenvironment

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.{{cite journal|first1=Muriel|last1=Vidal|title= Some Asaphidae from the Saint-Chinian Formation, Lower Ordovician, Montagne Noire (France): Systematics and palaeoenvironments|journal=Geobios|volume =29| date= 1996|issue=6|pages= 725–744|doi=10.1016/S0016-6995(96)80018-0}}

Paleofauna

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"{{cite journal|first1=Marcel|last1=Thoral|date=1946|title=Cycles géologiques et formations nodulifères de la Montagne Noire|journal= Publications du musée des Confluences, Année 1946|volume=1| pages=1–63|url=https://www.persee.fr/doc/mhnly_0373-6636_1946_num_1_1_983}}..

=Nautiloids=

class="wikitable sortable" ! Genus !! Species !! Locality !! Age !! Notes !! Images
Cyclostomiceras	C. thorali	align="center" \|Euloma filacovi Zone	Late Tremadocian	A cyclostomiceratid ellesmerocerid{{Cite journal\|last1=Kröger\|first1=B.\|last2=Evans\|first2=D. H.\|date=2011\|title=Review and palaeoecological analysis of the late Tremadocian – early Floian (Early Ordovician) cephalopod fauna of the Montagne Noire, France\|journal=Museum für Naturkunde\|language=en\|volume=14\|issue=1 \|pages=5–34\|doi=10.1002/mmng.201000013\|doi-access=free\|url=https://repository.publisso.de/resource/frl:6406908/data}}
rowspan="3" \| Saloceras	S. chinianense	align="center" \|Euloma filacovi Zone	Late Tremadocian	An eothinoceratid ellesmerocerid
\| S. murvielense	align="center" \|Euloma filacovi Zone	Late Tremadocian	An eothinoceratid ellesmerocerid
\| S. pradense	align="center" \|Taihungshania miqueli acme Subzone	Late Tremadocian	An eothinoceratid ellesmerocerid
Rioceras	R. escandei	align="center" \|Euloma filacovi Zone ; Asaphelina barroisi berardi and Taihungshania miqueli Subzone	Late Tremadocian	A rioceratid ellesmerocerid
Felinoceras	F. constrictum	align="center" \|Euloma filacovi Zone	Late Tremadocian	A rioceratid ellesmerocerid
rowspan="2" \| Annbactroceras	A. martyi	align="center" \|Euloma filacovi Zone	Late Tremadocian	A baltoceratid orthocerid
A. felinense	align="center" \|Euloma filacovi Zone	Late Tremadocian	A baltoceratid orthocerid name="Kröger2011"/>
Bactroceras	B. mourguesi	align="center" \|Euloma filacovi Zone	Late Tremadocian	A baltoceratid orthocerid
Cochlioceras	C.? aff. roemeri	align="center" \|Euloma filacovi Zone ; Asaphelina barroisi berardi and Taihungshania miqueli Subzone	Late Tremadocian	A baltoceratid orthocerid
Thoraloceras	T. bactroceroides	align="center" \|Euloma filacovi Zone ; Asaphelina barroisi berardi and Taihungshania miqueli Subzone	Late Tremadocian	A troedsonellid dissidocerid
Lobendoceras	L. undulatum	align="center" \|Euloma filacovi Zone ; Asaphelina barroisi berardi and Taihungshania miqueli Subzone	Late Tremadocian	A protocameroceratid endocerid

=Trilobites=

class="wikitable sortable" ! Genus !! Species !! Locality !! Age !! Notes !! Images
Paramegalaspis	P. immarginata	align="center" \| Prades-sur-Vernazobre	Late Tremadocian-Early Arenig	An asaphid{{Cite journal\|last1=Vidal\|first1=M.\|date=1996\|title=Quelques Asaphidae (Trilobita) de la Formation de Saint-Chinian, Ordovicien inférieur, Montagne Noire (France): Systématique et paléoenvironnements\|journal=Geobios\|language=en\|volume=29\|issue=6 \|pages=725–744\|doi=10.1016/S0016-6995(96)80018-0\|bibcode=1996Geobi..29..725V }}
rowspan="2" \| Asaphellus	A. frequens	align="center" \| Prades-sur-Vernazobre	Late Tremadocian-Early Arenig	An asaphid
\| A.? sp.	align="center" \| Félines-Minervois	Late Tremadocian-Early Arenig	An asaphid
Aocaspis	A. macrophtalma	align="center" \| La Rouvelane, près de Prades-sur-Vernazobre	Late Tremadocian-Early Arenig	An nileid{{Cite journal\|last1=Dolambi\|first1=T.\|last2=Gond\|first2=P.\|date=1992\|title=Aocaspis nov. gen., nouveau Trilobite Nileidae de l'Ordovicien inférieur de Montagne Noire (France)\|journal=Geobios\|language=en\|volume=25\|issue=2 \|pages=213–224\|doi=10.1016/S0016-6995(06)80400-6\|bibcode=1992Geobi..25..213D }}
rowspan="3" \| Geragnostus	G. occitanus	align="center" \| Saint-Chinian	Early Arenig	A geragnostid{{cite journal\|first1=B. F. \|last1=Howell\|date=1935\|title= Cambrian and Ordovician trilobites from Herault, southern France\|journal=Journal of Paleontology\|volume=9\|issue=3\|pages=222–238}}
G. callavei	align="center" \| Saint-Chinian	Early Arenig	A geragnostid
G. pusio	align="center" \| Saint-Chinian	Early Arenig	A geragnostid
Micragnostus	M. languedocensis	align="center" \| Saint-Chinian	Early Arenig	A micragnostid
rowspan="4" \| Trinodus	T. chinianensis	align="center" \| Saint-Chinian	Early Arenig	A trinodid
\| T. corpulentus	align="center" \| Saint-Chinian	Early Arenig	A trinodid
\| T. abruptus	align="center" \| Saint-Chinian	Early Arenig	A trinodid
\| T. oviformis	align="center" \| Saint-Chinian	Early Arenig	A trinodid

Trilobites:{{cite journal|first1=J. C.|last1= Capera|first2= R. |last2=Courtessole |first3=J.|last3= Pillet|date=1978|title= Contribution à l'étude de l'Ordovicien inférieur de la Montagne Noire : biostratigraphie et révision des Agnostida|journal=Annales de la Société Géologique du Nord |volume=98|issue= 1|pages=67–87}}
:Members from the Asaphida order and the Asaphidae family are commons :
Asaphelina barroisi barroisi,
Asaphelina barroisi berardi,
Niobella ligneresi,
Taihungshania miqueli,
Ampyx priscus,{{cite book|last1=Thoral|first1=M.|title=Contribution à l'étude paléontologique de l'Ordovicien inférieur de la Montagne Noire et révision sommaire de la faune cambrienne de la Montagne Noire|editor=Imprimerie de la Charité|place=Montpellier|pages= 362 pp|date=1935}}
Ampyxinella ;
:The Agnostida order is present, with:
Arthrorhachis;{{cite journal|last1=Vizcaino|first1=D.|last2=Alvaro|first2=J.|last3=Lefebvre|first3=B.|date=2001|title=The lower Ordovician of the southern Montagne Noire|journal=Annales de la Société Géologique du Nord |volume=8|issue=2|pages=213–220}}
:Ptychopariida order:
Euloma filacovi,
Solenopleuropsis ribeiro;{{cite journal|last1=Alvaro|first1=J.|last2=Lefebvre |first2=B.|last3=Vizcaino|first3=D.|date= 2001|title=Catalogue of the fossil species defined in the Lower Paleozoic of the southern Montagne Noire|journal=Annales de la Société Géologique du Nord|volume=8|issue=2|pages= 227–232}}
: Phacopida order :
Platycalymene.

=Echinoderms=

class="wikitable sortable" ! Genus !! Species !! Locality !! Age !! Notes !! Images
rowspan="2" \| Arauricystis	A. primaeva	align="center" \|		A cornute stylophoran
\| A. occitana	align="center" \|		A cornute stylophoran
rowspan="2" \| Cothurnocystis	C. fellinensis	align="center" \|		A cornute stylophoran
\| C. courtessolei	align="center" \|		A cornute stylophoran
rowspan="2" \| Phyllocystis	P. blayaci	align="center" \|		A cornute stylophoran
\| P. crassimarginata	align="center" \|		A cornute stylophoran
Thoralicystis	T. griffei	align="center" \|		A cornute stylophoran
Trigonocarpus	T. singularis	align="center" \|		A cornute stylophoran
rowspan="2" \| Chauvelicystis	C. spinosa	align="center" \|		A cornute stylophoran
\| C. vizcainoi	align="center" \|		A cornute stylophoran
rowspan="2" \| Galliaecystis	G. lignieresi	align="center" \|		A cornute stylophoran
\| G. ubaghsi	align="center" \|		A cornute stylophoran
Amygdalotheca	A. griffei	align="center" \|		A cornute stylophoran
Anatifopsis	A. trapeziiformis	align="center" \|		A mitrate stylophoran
Balanocystites	B. escandei	align="center" \|		A mitrate stylophoran
Peltocystis	P. cornuta	align="center" \|		A mitrate stylophoran
Vizcainocarpus	V. dentiger	align="center" \|		A mitrate stylophoran
Chinianocarpos	C. thorali	align="center" \|		A mitrate stylophoran
Minervaecystis	M. vidali	align="center" \|		A solute homoistelean{{Cite journal\|last1=Vizcaïno\|first1=D.\|last2=Lefebvre\|first2=B.\|date=1999\|title=Les échinodermes du Paléozoïqueinférieur de Montagne Noire: Biostratigraphie et paléodiversité\|journal=Geobios\|language=en\|volume=32\|issue=2 \|pages=353–356\|doi=10.1016/S0016-6995(99)80049-7\|bibcode=1999Geobi..32..353V }}
Balantiocystis	B. thorali	align="center" \|		An eocrinoïd
Aethocrinus	A. moorei	align="center" \|		A cladide crinoïd
Macrocystella	M. azaizi	align="center" \|		A dichoporite rhombifere. Two subspecies are present : M. a. paucicristatus and M. a. multicristata
Hemicystites	H. boehmi	align="center" \|		A edrioasteroïd
?Pyrgocystis	?P. sp.	align="center" \|		A edrioasteroïd
Chinianaster	C. levyi	align="center" \|		A goniactinid stelleroïd
Villebrunaster	V. thorali	align="center" \|		A goniactinid stelleroïd
Ampullaster	A. ubaghsi	align="center" \|		A goniactinid stelleroïd
Pradesura	P. jacobi	align="center" \|		A stenurid stelleroïd

Other fossil remains of marine animals are known from the formation:{{cite book|first1=C. |last1=Babin|first2= R.|last2= Courtessole| first3=M. |last3=Melou| first4=J. |last4=Pillet| first5=D. |last5=Vizcaino |first6=E. L. |last6=Yochelson|date= 1982|title=Brachiopodes (Articulés) et mollusques (bivalves, rostroconches, monoplacophores, gastéropodes) de l'Ordovicien inférieur (Trémadocien-Arenigien) de la Montagne Noire (France méridionale) |pages=1–63}}

References

Category:Geologic formations of France

Category:Ordovician System of Europe

Category:Ordovician France

Category:Ordovician south paleopolar deposits