Kerguelen Plateau trawl sample (Pliocene of Indian Ocean)

Where: Indian Ocean (52.9° S, 75.6° E: paleocoordinates 52.8° S, 75.0° E)

• coordinate stated in text

• small collection-level geographic resolution

When: Piacenzian (3.6 - 2.6 Ma)

• Initially the bivalve suggested correlation with the Drygalski Formation of Late Miocene age, on Heard Island and the lithology is similar to that described for sedimentary facies within the Drygalski Formation. However, the age of the sample is constrained to < 3.2 Ma from the presence of one fragment of Fragilariopsis kerguelensis (O’Meara). The mean D/L ratio for aspartic acid (total acid hydrolysate) for the shell material is 0.352 ± 0.005 (n = 3). A numeric age for these shells was determined based on a model of apparent parabolic racemization kinetics (Mitterer & Kriausakul 1989). The age calculation was calibrated based on the degree of racemization in the fossil cockle Katelysia rhytiphora (D/LASP = 0.80: Murray-Wallace & Kimber 1989) from the Jandakot Beds of the Perth Basin, Western Australia, which based on micropalaeontological evidence straddles the Pliocene/Pleistocene transition (Mallett 1982). On the basis of the above, a minimum age for the shell is 2.20 ± 0.33 Ma. The uncertainty term accounts for a 1°C uncertainty in diagenetic temperature. In summary, the age appears to be Late Pliocene, 3.62–2 Ma. If the extinction of Austrochlamys from Antarctica at 2.5 Ma, referred to by Jonkers (2003) extended to the Heard Island region, the age may be restricted to 3.62–2.5 Ma.

• bed-level stratigraphic resolution

Environment/lithology: shoreface; lithified, coarse-grained, volcaniclastic, gray, conglomeratic sandstone

• All features of the sediment attest to a high energy, shallow water, fully marine environment of deposition close to a source of volcanic debris. Depth was near wave base, subject to considerable current activity which winnowed most fine debris, biogenic or detrital, and may be the cause of breakage of many of the valves.
• Well-sorted, very coarse, grey volcaniclastic sandstone of basaltic fragments but with sporadic large clasts to about 8 cm diameter; most is in the coarse sand fraction.

Size class: macrofossils

Collected by FV Austral Champion in 2000

Primary reference: P. G. Quilty, C. V. Murray-Wallace, and J. M. Whitehead. 2004. Austrochlamys heardensis (Fleming, 1957) (Bivalvia: Pectinidae) from Central Kerguelen Plateau, Indian Ocean: palaeontology and possible tectonic significance. Antarctic Science 16:329-338 [M. Clapham/M. Clapham]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 209138: authorized by Matthew Clapham, entered by Matthew Clapham on 25.04.2020

Creative Commons license: CC BY (attribution)

Taxonomic list

Show authors, comments, and common names
Bivalvia
 Pectinida - Pectinoidae
Austrochlamys heardensis
Austrochlamys heardensis Fleming 1957 scallop
Polychaeta
 Sabellida - Serpulidae
Spirorbis sp.
Spirorbis sp. Daudin 1800
Rhynchonellata
 Terebratulida -
Terebratulida indet.