Gran Bajo de San Julian - San Julian Fm (Oligocene of Argentina)

Where: Argentina (49.3° S, 67.7° W: paleocoordinates 51.0° S, 58.6° W)

• local area-level geographic resolution

When: San Julián Formation, Early/Lower Oligocene (33.9 - 28.4 Ma)

• STRATIGRAPHIC RELATIONS: From beds of the San Julián Fm, which unconformably overlies the Bahia Laura Group and is overlain by the Early Miocene Monte Leon Fm. THICKNESS: From multiple beds within formation that reaches a thickness of 100 m. AGE: Early Oligocene to Late Oligocene according to molluscan biostratigraphy. Assigned to the Early Oligocene based on the presence of Zygochlamys geminatus. STRATIGRAPHIC POSITION: From upper parts of the formation.

• group of beds-level stratigraphic resolution

Environment/lithology: coastal; unlithified, bioturbated sandstone and poorly lithified, sandy limestone

• ENVIRONMENT: Environmental data not reported in text. Siliciclastic shallow marine assemblage.
• SPECIFIC LITHOLOGY: Bioturbated sandstone, cross-bedded sandstone and sandy limestone. LITHIFICATION: Unlithified on the basis of figured specimes.

Size class: macrofossils

Collection methods: COLLECTOR: List includes both new collections by the author, and examination of museum and previously reported taxa. REPOSITORY: Museo Argentino de Ciencias Naturales Bernadino Rivadavia, Buenos Aires, Argentina.

Primary reference: C. J. del Rio. 2004. Tertiary Marine Molluscan Assemblages of Eastern Patagonia (Argentina): A Biostratigraphic Analysis. Journal of Paleontology 78(6):1097-1122 [L. Ivany/P. Wall/P. Wall]more details

Purpose of describing collection: biostratigraphic analysis

PaleoDB collection 71402: authorized by Austin Hendy, entered by Austin Hendy on 24.04.2007

Creative Commons license: CC BY (attribution)

Taxonomic list

• COVERAGE: Exhaustive for bivalvia and gastropoda. NOMENCLATURE: Not an authoritaive publication, but providing revised generic placement for many previously reported antiquated names.
unclassified
  -
Gastropoda
 Trochoidea - Solariellidae
 Epitonioidea - Epitoniidae
 Neotaenioglossa - Calyptraeidae
"Calyptraea" juliana slipper shell
"Calyptraea" pileus Lamarck 1822 slipper shell
 Cerithioidea - Turritellidae
 Sorbeoconcha - Struthiolariidae
 Neogastropoda - Muricidae
Trophon santacrucensis Ihering 1897 murex snail
 Neogastropoda - Volutidae
""Proscaphella" gracilior" = Miomelon gracilis
""Proscaphella" gracilior" = Miomelon gracilis Philippi 1887 volute
 Sorbeoconcha - Naticidae
""Polynices" secunda" = Polinices, ""Polynices" subtenuis" = Polinices subtenuis
""Polynices" secunda" = Polinices moon snail
""Polynices" subtenuis" = Polinices subtenuis Ihering 1907 moon snail
 Sorbeoconcha - Hipponicidae
Hipponix costata hoof shell
Bivalvia
 Arcida - Parallelodontidae
"Cucullaea darwini" = Cucullaria darwini
"Cucullaea darwini" = Cucullaria darwini Philippi 1887 clam
 Arcida - Arcidae
"Arca (Barbatia) juliana" = Barbatia, Arca puntaensis
"Arca (Barbatia) juliana" = Barbatia clam
 Arcida - Cucullaeidae
Cucullaea (Monteleonia) marshalli Zinsmeister 1981 clam
 Arcida - Glycymerididae
 Arcida - Limopsidae
Limopsis insolita Sowerby 1846 clam
 Pectinida - Anomiidae
 Pectinida - Pectinoidae
"Zygochlamys geminatus" = Zygochlamys geminata
"Zygochlamys geminatus" = Zygochlamys geminata Sowerby 1846 scallop
 Ostreida - Ostreidae
Crassostrea hatcheri Ihering 1899 oyster
 Mytilida - Mytilidae
"Aulacomya cf. ater" = Aulacomya atra, Modiolus ameghinoi
"Aulacomya cf. ater" = Aulacomya atra Molina 1782 mussel
Modiolus ameghinoi Ihering 1907 mussel
 Lucinida - Lucinidae
 Pholadida - Pholadidae
Pholadidea patagonica Philippi 1887 clam
 Pholadida - Corbulidae
 Cardiida - Veneridae
Austrocallista iheringi Cossmann 1898 venus clam
Pitar julianum venus clam
Dosinia meridonalis Ihering 1897 venus clam
"Chione" patagonica Philippi 1887 venus clam
 Cardiida - Cardiidae
"Cardium" pisum Philippi 1887 cockle
 Hiatellida - Hiatellidae
 Carditida - Carditidae
 Carditida - Crassatellidae
 Nuculanida - Malletiidae