PBDB Collection

Sierra Baguales (Miocene of Chile)

Where: Magallanes, Chile (50.6° S, 72.5° W: paleocoordinates 51.4° S, 66.5° W)

• coordinate estimated from map

• outcrop-level geographic resolution

When: Santa Cruz Formation, Burdigalian (20.4 - 16.0 Ma)

• The lithological correlation is also confirmed by detrital zircon ages (maximum age of 18.23±0.26 Ma) and a rich assemblage of terrestrial vertebrate fossils, biostratigraphically equivalent to a post- Colhuehuapian, pre-Santacrucian South American Land Mammal Age (SALMA) fauna, suggesting a range of 19 to 17.8 Ma

•

•Santa Cruz Formation (first refered by Ameghino (1889) as the ‘Piso Santacruceño’ (Marshall, 1976; Vizcaíno et al., 2012a) and later formalized by Zambrano and Urien (1970)), but Keidel and Hemmer in 1931 refered to this formation in Chile as Palomares.

•The Santa Cruz Formation is exposed along the southern flank of Cerro Cono (Fig. 2), where it overlies the Estancia 25 de Mayo Formation with a conformable, gradational contact

• group of beds-level stratigraphic resolution

Environment/lithology: fluvial; mudstone and sandstone

• Santa Cruz Formation in this area was deposited in a continental, fluvial environment, as indicated by the abundance of terrestrial vertebrate fragments, Scoyenia including probable hymenopterid traces, multi-coloured (often reddish), blocky-weathering mudstones (Fig. 4) with occasional mud-cracks, and sandstones showing sedimentary structures such as trough, epsilon and high-angle planar cross-lamination (Fig. 5), with a more or less consistent paleocurrent direction towards the east-northeast

• The descriptions are very long, this is a sum up:

•Unit 1 has a total thickness of 32.7 m. Overlying an erosional contact at the base is a 0.7 m thick, reddish brown, trough cross-laminated, medium- to coarse-grained sandstone, in which the troughs are up to about 1 m wide.

•Unit 2 has an erosional basal contact overlain by a 0.5 m thick, dark brown, medium-grained sandstone showing high-angle planar cross-lamination and mi- nor trough cross-lamination indicating northwest- to east-flowing currents.

•Unit 3, with a total thickness of 13.3 m, has a 1.0 m thick conglomerate at the base with small (up to 1 cm), multi-coloured chert and quartz clasts, grading towards the east into sandy conglomerate.

•Unit 4 starts with a 1.9 m thick, whitish, medium- grained sandstone at the base, which is low-angle planar cross-laminated.

•Unit 5 is 8.6 m thick and commences with a 4.6 m thick, yellowish, clay-rich, fine- to medium-grained sandstone with upper flow regime horizontal lami- nation, rare trough cross-lamination and high-angle cross-lamination

•Unit 6 has an erosional basal contact and a total thickness of 4.6 m, which can be subdivided into 5 fining-upward sub-units (6a-e) separated by sharp to erosional contacts.

•Fossils come from units 1-7

Size classes: macrofossils, mesofossils

Preservation: trace

Primary reference: J. E. Bostelmann, J. P. Le Roux, A. Vásquez, N. M. Gutiérrez, J. L. Oyarzún, C. Carreño, T. Torres, R. Otero, A. Llanos, C. M. Fanning, and F. Hervé. 2013. Burdigalian deposits of the Santa Cruz Formation in the Sierra Baguales, Austral (Magallanes) Basin: Age, depositional environment and vertebrate fossils. Andean Geology 40(3):458-489 [P. Mannion/M. Kouvari]more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 204203: authorized by Philip Mannion, entered by Miranta Kouvari on 03.09.2019, edited by Mark Uhen

Creative Commons license: CC BY (attribution)

Taxonomic list

Show authors, comments, and common names

Mammalia
Panameriungulata - Proterotheriidae	Proterotheriinae indet., Paramacrauchenia scamnata Proterotheriinae indet. Ameghino 1885 placental Paramacrauchenia scamnata Ameghino 1902 placental
Rodentia -	Adelphomys candidus Adelphomys candidus Ameghino 1887 caviomorph
Rodentia - Neoepiblemidae	Perimys incavatus Perimys incavatus Ameghino 1902 caviomorph
Rodentia -	Cavioidea indet. Cavioidea indet. Fischer de Waldheim 1817 caviomorph
Megatherioidea - Megalonychidae	Megalonychidae indet. Megalonychidae indet. Gervais 1855 edentate
Tardigrada -	"Tardigrada indet." = Folivora "Tardigrada indet." = Folivora Delsuc et al. 2001 edentate
Cingulata - Chlamyphoridae	Proeutatus "sp. nov.", Proeutatus sp. Proeutatus "sp. nov." Ameghino 1891 edentate Proeutatus sp. Ameghino 1891 edentate
Cingulata - Propalaehoplophoridae	"Propalaehoplophorinae indet." = Propalaehoplophoridae "Propalaehoplophorinae indet." = Propalaehoplophoridae Ameghino 1891 edentate
Astrapotheria - Astrapotheriidae	Astrapothericulus iheringi, Astrapotheriinae indet. Astrapothericulus iheringi Ameghino 1899 placental Astrapotheriinae indet. Soria and Alvarenga 1989 placental
Notoungulata -	Notohippinae (aff. Notohippus) toxodontoides Notohippinae (aff. Notohippus) toxodontoides Ameghino 1890 notoungulate
Notoungulata - Toxodontidae	Adinotherium sp., Nesodon sp. Adinotherium sp. Ameghino 1887 notoungulate Nesodon sp. Owen 1846 notoungulate
Aves
Cariamiformes - Cariamidae	Cariamidae indet. Cariamidae indet. Bonaparte 1853 seriema

Coniferales - Podocarpaceae	Podocarpaceae indet. Podocarpaceae indet. Endlicher 1847 podocarp
Dicotyledoneae
Myrtales - Myrtaceae	Myrtaceae indet. Myrtaceae indet. de Jussieu 1789 myrtle
Myrtales - Onagraceae	Onagraceae indet. Onagraceae indet. de Jussieu 1789 willowherb
Angiospermae
Fagales - Nothofagaceae	Nothofagaceae indet. Nothofagaceae indet. Kuprianova 1962
Asterales - Asteraceae	Asteraceae indet. Asteraceae indet. Berchtold and Presl 1820 daisy
Caryophyllales - Chenopodiaceae	Chenopodiaceae indet. Chenopodiaceae indet. Ventenant 1799
Proteales - Proteaceae	Proteaceae indet. Proteaceae indet. de Jussieu 1789
Poales - Poaceae	Poaceae indet. Poaceae indet. Barnhart 1895 grass
Polypodiopsida
Cyatheales - Polypodiidae	Cyatheaceae indet. Cyatheaceae indet. Kaulfuss 1827 scaly tree fern

Ichnofossils -	Skolithos sp. Skolithos sp. Haldemann 1840