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

Where: Argentina (47.3° S, 71.3° W: paleocoordinates 48.1° S, 65.6° 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 65178: 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.
Gastropoda
 Epitonioidea - Epitoniidae
 Neotaenioglossa - Calyptraeidae
Calyptraea juliana slipper shell
 Sorbeoconcha - Struthiolariidae
 Neogastropoda - Muricidae
Trophon sp. Montfort 1810 murex snail
 Heterostropha - Acteonidae
Acteon bajoensis Chiesa et al. 1995 snail
Bivalvia
 Arcida - Limopsidae
"Pectunculina patagoniensis" = Limopsis
"Pectunculina patagoniensis" = Limopsis clam
 Pectinida - Pectinoidae
Zygochlamys jorgensis Ihering 1907 scallop
 Ostreida - Ostreidae
Crassostrea hatcheri Ihering 1899 oyster
 Cardiida - Veneridae
Eurhomalea difficilis Ortmann 1899 venus clam
Rhynchonellata
 Rhynchonellida - Notosariidae
 Terebratulida - Terebratellidae