154 
Records of the Australian Museum (2017) Vol. 69 
Age 
m.yr. 
Epoch 
Internat. 
Stages 
Australian 
Stages 
Perth 
Basin 
Eucla 
Basin 
Kangaroo 
Island 
St Vincent 
Basin 
Otway 
Basin 
Gippsland 
Basin 
TARANTIAN 
0.77- 
1 - 
LLl 
~Z. 
IONIAN 
? 
Haunted 
LU 
O 
O 
wwwx 
X Hill Gravel 
1- 
co 
LU 
CALABRIAN 
- -?--% - 
WERRI- 
KOOIAN 
Bassendean Sd. 
Whalers Bluff 
1.81- 
2 
Up. Ascot Fm. 
/ Bridgewater 
/Bridgewater^ 
—J 
CL 
GELASIAN 
/ Fm. 
9 R 
Z.O 
3- 
LU 
PIACENZIAN 
? 
Lr. Ascot Fm. ^ 
y^Roe Calc. ^ 
/^PtEllenFm. ▲ 
Hallett Cove 
▲ 
Hallett 
Cove Sdst. ^ 
Q O 
"7 
o.v 
4 - 
LU 
O 
o 
Moitun Ck.._-— S ^ 
“ 
ZANCLEAN 
4.35- 
- 5 Nyerimalang 
5- 
c V* 
CL 
KALIMNAN 
unnamed 1st. • 
Table Rock 
Grange * 
Bum Fm. 
• 
O.oO 
6- 
LU 
:z: 
LU 
o 
o 
MESSINIAN 
CHELTEN¬ 
HAM IAN 
Jemmys Point 
Formation 
s 
Dry Ck. Sand 
/ Goodwood 
7- 
MITCHELLIAN 
/ Fm. 
Tambo R. Fm. 
Figure 19. Stratigraphical position of Janthina fossil localities in southern Australia, modified from Beu and Darragh (2001: fig. 6). 
Bridgewater Limestone Fm shown diagrammatically; on mainland southern Australia it probably represents every interglacial high-stand 
from at least 2 Ma to MIS 3. Symbols: ▲ Janthina chavani:, • Janthina typica. Grey tone = stratigraphical hiatus. 
limestone layers in overburden above the quarried Gambier 
Limestone (Longfordian, Aquitanian, early Miocene). A 
thin block of limestone c. 1 m 2 containing abundant J. 
chavani was also observed at the quarry office. Bridgewater 
Limestone usually has been mapped as Pleistocene in 
age. The Dismal dune ridge, the oldest dune ridge east of 
Mount Gambier in south-easternmost South Australia, was 
deposited during MIS 23 (middle Pleistocene; Blakemore et 
al., 2015, and references therein) and the ridges extend up to 
MIS 3 (latest Pleistocene) at the present coast (Blakemore 
et al. , 2015). The oldest ridge west of the Kanawinka Fault 
scarp further north at Naracoorte, the Naracoorte dune ridge 
(Sprigg, 1952: fig. 17a, and geological map) has been dated 
by amino stratigraphy and thermoluminescence dating at 
c. 800 ka (late Calabrian, Pleistocene) (Murray-Wallace et 
ah, 2001), although it would have been judged to be late 
Piacenzian-Gelasian from its content of J. chavani. Possibly 
the date has been affected by diagenesis. If not, this date 
indicates that J. chavani has a fossil record in southeastern 
South Australia that is very much younger than anywhere 
else. Other excavations into dune ridges likely would reveal 
further Janthina fossils. Parallel older dune ridges extend 
further north-eastwards into south-western Victoria and 
further inland in South Australia, and it is conceivable that 
they will reveal a detailed evolutionary history of Janthina 
species. However, water temperature would be significant 
again here; the Naracoorte ridge of Bridgewater Limestone 
evidently was influenced by the warm Leeuwin Current, 
which transported Janthina specimens from Western 
Australia eastwards into South Australia. Similarly warm 
temperatures would have to have affected South Australia 
during other interglacial periods for Janthina fossils to occur 
in other dune ridges. 
Roe Calcarenite (type formation of Janthina chavani ; 
Ludbrook, 1978) in southeastern Western Australia contains 
abundant, beautifully preserved specimens of J. chavani 
in weakly consolidated sand. Large collections from Roe 
Calcarenite are present in several Australian museums. 
Correlations by Beu & Darragh (2001: fig. 6) suggested an 
early Piacenzian age for Roe Calcarenite, but in view of 
current knowledge of Janthina time ranges in New Zealand, 
the age is now known to be late Piacenzian (3.0-2.59 Ma). 
James et ah (2006) and James & Bone (2007) described 
the outcrop, stratigraphy, lithology, and environment of 
deposition of Roe Calcarenite. James et ah (2006: table 1, 
fig. 6) also reported strontium isotope ratios indicating a 
Pliocene-early Pleistocene age. However, the surprisingly 
large age range of 4.45-1.17 Ma indicates diagenetic 
alteration of aragonite in many shells, as the real age range 
is now known to be 3.0-2.59 Ma. James & Bone (2007) 
recognized two members. The lower member, consistently 
1 m thick, comprises uniform, mostly structureless, 
unconsolidated, bivalve-gastropod-Margr'wopora rudstone or 
floatstone, with a biofragmental grainstone matrix containing 
some quartz grains. The large warm-water foraminifer 
Marginopora is abundant throughout. The upper member 
is more variable in thickness, distribution and lithology 
than the lower member, and in many exposures is severely 
cemented by soil carbonates. The fine-grained biofragmental 
grainstone contains few identifiable molluscs. The contact 
between the members is gradational in a few places, but a 
burrowed unconformity separates them in most places, and 
a thin bed of finely laminated grainstone separates them in a 
few places. The total observed thickness of the formation is 
3 m (James & Bone, 2007: fig. 6). Deposition took place on 
a very shallow carbonate platform at the head of the Great 
