Little Rapid River 2 (Oligocene of Australia)

Where: Tasmania, Australia (41.2° S, 145.2° E: paleocoordinates 55.6° S, 144.0° E)

• coordinate stated in text

When: Proteacidites tuberculatus pollen zone, Late/Upper Oligocene (28.4 - 23.0 Ma)

• The fossil-bearing mudstone has been dated by palynological correlation by M. K. Macphail. He considers that the mudstone belongs to the lower Proteacidites tuberculatus Zone of Stover & Partridge, 1973 (hill & Bigwood, 1987). Macphail (in Hill 1987) suggested a Late Oligocene age for the flora.

•The sediments are dated palynologically as Early Oligocene (Macphail et al. 1994) in Guerin & Hill, 2003.

Environment/lithology: lacustrine; poorly lithified, gray mudstone and coarse-grained, gray sandstone

• It is likely that the Little Rapid River deposit represents a Tertiary lake which has undergone a dramatic change in depositional regimes. The lower unit is characteristic of a low energy environment such as the centre of a lake with low stream input. Organic laminations would be the result of fluctuating stream flow (possibly seasonal), the plant matter most probably being derived from vegetation lining inflowing creeks and streams or from the lake edge itself.
• The deposit is composed of two different lithological units, each corresponding with a separate environment of deposition. The lower unit is at least 2 m in depth and is composed of a very fine-grained dark grey mudstone characterised by many layers of black organic material containing macrofossils. mudstone characterised by many layers of black organic material containing macrofossils.

•Above the organic layer which separates the two units the sediment changes suddenly to a coarser grained material composed of dark grey sands, once again rich in black organic material. Both upper and lower units are consolidated when dry but become plastic when wet. Fossils from Hill, 1989 & Hill and Carpenter, 1989 were recovered from the fluviatile sands of this place.

Size class: macrofossils

• Several vegetative fragments and one ovulate cone were retrieved.

Preservation: adpression

Collection methods: chemical, peroxide, sieve

• Fossils collected by R. S. Hill from 1992 to 1998 (Guerin & Hill, 2003).

Primary reference: P. M. Wells and R. S. Hill. 1989. Fossil Imbricate-leaved Podocarpaceae from Tertiary Sediments in Tasmania. Australian Systematic Botany 2(4):387-423 [C. Jaramillo/C. Jaramillo]more details

Purpose of describing collection: paleoecologic analysis

PaleoDB collection 167317: authorized by Carlos Jaramillo, entered by Carlos Jaramillo on 11.03.2015

Creative Commons license: CC BY (attribution)

Taxonomic list

 Pinales - Podocarpaceae
Willungia oppositifolia n. sp.5 Hill and Pole 1992
Dacrycarpus mucronatus n. sp. Wells and Hill 1989
Dacrycarpus linearis n. sp. Wells and Hill 1989
Dacrycarpus cupressiformis n. sp. Wells and Hill 1989
Phyllocladus aberensis n. sp.2 Hill 1989
Phyllocladus lobatus n. sp.2 Hill 1989
Sigmaphyllum tasmanensis n. sp.6 Hill and Scriven 1999
Microstrobos microfolius Wells and Hill 1989
Smithtonia jonesii n. sp.5 Hill and Pole 1992
 Pinales - Cupressaceae
Libocedrus mesibovii n. sp.4 Hill and Carpenter 1989
Ovulate cone
Libocedrus jacksonii n. sp.4 Hill and Carpenter 1989
 Pinales - Araucariaceae
 Fagales - Casuarinaceae
Gymnostoma tasmanianum n. sp.1 Guerin and Hill 2003