El Chacay Fm - El Bajo, Provincia de Santa Cruz (Miocene of Argentina)

Where: Argentina (48.8° S, 70.8° W: paleocoordinates 49.6° S, 65.0° W)

• coordinate estimated from map

• outcrop-level geographic resolution

When: El Chacay Formation, Burdigalian (20.4 - 16.0 Ma)

• STRATIGRAPHIC RELATIONS: From El Chacay Fm, which regionally overlies Basalto Posadas and is overlain by the Santa Cruz Fm (Eocene-Oligocene). THICKNESS: AGE: Eocene. No further detail provided. Justified on the basis of stratigraphic position and biostratigraphic correlation. This unit has more recently been dated as early Miocene (Burdigalian) by Sr isotopes (Cuitiño et al., 2015) and correlative units also as Burdigalian by U-Pb chronology (Cuitiño et al., 2012). STRATIGRAPHIC POSITION: Unknown stratigraphic position within section. Figure 3 (Chiesa et al. 1995) suggests that the collection is derived from multiple distinct beds within the formation at each section.

• group of beds-level stratigraphic resolution

Environment/lithology: marine; lithified sandstone and lithified, shelly/skeletal, sandy mixed carbonate-siliciclastic

• ENVIRONMENT: Shallow marine arenaceous platform, normal salinity, under a subtropical climate, with water temperatures between 19-22 degrees C.
• SPECIFIC LITHOLOGY: No specific lithology stated though Figure 3 (Chiesa et al. 1995) suggests that macrofauna are typically derived from sandstones and sandy coquinas at each section. LITHIFICATION: Lithified, based on figured specimens.

Size class: macrofossils

Collection methods: quarrying,

• COLLECTORS: Presumably collected by authors during broader lithostratigraphic study and geologic mapping (see Chiesa and Camacho, 1995). REPOSITORY: CIRGEO (Centro de Investigaciones en Recursos Geologicos), Argentina.

Primary reference: J.O. Chiesa, S.G. Parma, and H.H. Camacho. 1995. Observaciones estratigraficas en el Paleogeno del noroeste de la Provincia de Santa Cruz (Republica Argentina). Parte II: Invertebrados marinos de la Formacion El Chacy (Eoceno), Provincia de Santa Cruz, Argentina. Systematica y bioestratigrafia. Monografias de la Acadamia Nacional de Ciencias Exactas, Fisicas Y Naturales 11:17-68 [A. Hendy/A. Hendy]more details

Purpose of describing collection: biostratigraphic analysis

PaleoDB collection 65186: authorized by Austin Hendy, entered by Austin Hendy on 19.09.2006

Creative Commons license: CC BY (attribution)

Taxonomic list

• COVERAGE: Exhaustive for all macrofaunal groups (Brachiopoda, Bivalvia, Gastropoda). NOMENCLATURE: Authoritative paper using subgeneric and species-level designations.
 Terebratulida - Terebratellidae
Gmelinmagas plicata Marinelarena 1964
Terebratella "sp. A" d'Orbigny 1847
Terebratella "sp. B" d'Orbigny 1847
 Pectinida - Pectinoidae
Zygochlamys jorgensis Ihering 1907 scallop
 Ostreida - Ostreidae
Crassostrea hatcheri Ihering 1899 oyster
 Carditida - Carditidae
Venericardia sp. Lamarck 1801 clam
 Cardiida - Lahillidae
Lahillia patagonica Ihering 1907 clam
 Lucinida - Lucinidae
Lucina neglecta Ortmann 1902 clam
 Nuculida - Nuculidae
Nucula (Leionucula) patagonica Philippi 1887 nut clam
 Protobranchia - Nuculanidae
Nuculana sp. Link 1807 pointed nut clam
 Ptenoglossa - Fasciolariidae
Pseudofax solitaria Chiesa et al. 1995 true whelk
 Cerithiacea - Thiaridae
Turritella ambulacrum Sowerby 1846 turret shell
Subspecies: T. ambulacrum argentina
 Neogastropoda - Volutidae
Proscaphella cossmanni Ihering 1907 volute
 Neogastropoda - Muricidae
Purpura chicoana murex snail
 Mesogastropoda - Naticidae
"Polinices chiloensis" = Neverita chiloensis
"Polinices chiloensis" = Neverita chiloensis Philippi 1887 moon snail
 Stromboidea - Struthiolariidae
 Calyptraeoidea - Calyptraeidae
Crepidula sp. Lamarck 1799 slipper shell
 Heterostropha - Acteonidae
Acteon bajoensis Chiesa et al. 1995 snail
 Spatangoida - Schizasteridae
Brisaster sp. Gray 1855 heart urchin
 Astrophorida -
Ortmannia ortmanni Chiesa et al. 1995 demosponge