Journal of the Royal Society of Western Australia, 86(3), September 2003 
dominated by benthic types of the Orders Rotaliida 
(including Cibicidoides, Gyroidinoides, Planogypsina ) and 
Miliolida (including Quinqueloculina, Triloculina, Pyrgo). 
Less common agglutinated foraminifers (including 
Textularia) and species of the Order Buliminida are also 
present. Planktonic foraminifers form about 10% of the 
foraminiferal assemblage. Ostracods make up a small 
percentage of the microfossil assemblage. 
Of the fossil groups present, the planktonic 
foraminifers provide the best indication of age, and key 
species are illustrated in Fig 3. The recovered 
assemblage includes none of the species that define 
Berggren & Miller's (1988) zonation for the tropical and 
subtropical Eocene. However, the range charts provided 
by Toumarkine & Luterbacher (1985) linked to the P- 
zonation of Berggren & Miller (1988; rather than to the 
P-zones listed by Toumarkine & Luterbacher) are useful 
in broadly defining an age for the present material 
based on international criteria. Globigerinatheka index 
index is recognized by its distinctive coiling, high- 
arched apertures and incised sutures (Fig 3A,B). 
According to the compilation of Toumarkine & 
Luterbacher (1985), this subspecies ranges from Zone 
Pll to the lower part of Zone P16 (Upper Eocene) and 
sporadically higher to the top of Zone P17 (the Eocene- 
Oligocene boundary according to Berggren & Miller 
1988). The presence of common G. index index therefore 
indicates that the new unit lies no higher than Zone 
P16. Subbotina inaequispira (Fig 3E-G) ranges from 
within Zone P7 to uppermost Zone P12. According to 
Berggren & Miller (1988, p 373) it may range into Zone 
P13. Subbotina eocaena ranges consistently from within 
P10 to the Oligocene, with descendant S. corpulenta 
ranging from the base of PI 3 into the Oligocene. The 
recovered specimens (Fig 3H-J) seem transitional 
between S. eocaena and more high-spired S. corpulenta, 
and imply that the new unit lies within or above Zone 
P13. The specimen illustrated in Fig 3K-M is a robust 
low trochospiral form with 3.5 chambers in the final 
whorl and with chambers elongated in the direction of 
coiling. The aperture seems to be a relatively high arch 
from the umbilicus toward the periphery. The wall is 
deeply corroded, but was probably coarsely perforate. It 
some aspects, it resembles Acarinina primitiva (Finlay) 
which ranges from the Paleocene to the top of P13 
(according to Toumarkine & Luterbacher 1985) and to 
the 39.0 Ma BKSA95 datum level. More probably, 
because of its looser coiling and higher arched aperture 
directed more to the periphery, it belongs to the 
Turborotalia cerroazulensis lineage as outlined by 
Toumarkine & Luterbacher (1985). The broad peripheral 
margin shows that the specimen is closer to T. 
cerroazulensis potneroli than to the more advanced T. 
cerroazulensis cerroazulensis, which has an angled 
periphery. According to Tourmarkine & Luterbacher 
(1985), Turborotalia cerroazulensis potneroli is the most 
abundant and widespread of the subspecies of the T. 
cerroazulensis lineage and ranges through Zones P12 to 
P17 (Middle to Upper Eocene). Among the other 
planktonic foraminifers, the specimen tentatively 
referred to Catapsydrax (Fig 3C) has a distinct bulla 
across the umbilicus and possibly a spinose surface, and 
may be related to Catapsydrax echinatus Bolli of the 
Middle Eocene (following Stainforth et al. 1975). 
Subbotina linaperta (Fig 3D) is a long-ranging species, 
and the species designation of Acarinina? sp (Fig 3N-P) 
is uncertain and its generic attribution tentative. 
Collectively, the planktonic foraminifers indicate that 
the newly discovered site belongs within the PI3 to PI6 
zonal range (40.5 - 34.0 Ma BKSA95). The absence of 
zonal index species that would narrow the stratigraphic 
range may indicate environmental constraints. 
Distinctive species of Truncorotaloides, that are abundant 
in the upper Zone P12 assemblage from the type Giralia 
Calcarenite (Haig et al. 1997) and range elsewhere to the 
top of Zone P14, are absent from the new assemblage. 
Morozovella, which also ranges upward to the top of Zone 
PI4, is absent from the new assemblage and from the 
Giralia Calcarenite P12 assemblage. Two explanations 
may account for the absence of these genera in the new 
assemblage: (1) the environment was too cool or too 
shallow for these genera (see discussion below on 
independent evidence for a cool shallow-water 
environment); (2) the new assemblage may belong to a 
level higher in the Upper Eocene than Zone PI 4. 
Comparison with known Eocene in Southern 
Carnarvon Basin 
The fossil assemblage from the new locality differs 
substantially from other Eocene assemblages in the 
Southern Carnarvon Basin (Appendix 1), especially as 
photozoan benthic faunal elements that characterize 
warm waters (using the definition of James 1997) are 
absent. These include "larger" (complex) benthic 
foraminifers that are abundant in the Giralia Calcarenite 
type section, at Red Bluff (north of Carnarvon) and 
Yaringa, and hermatypic colonial corals that are common 
in the Merlinleigh Sandstone. In contrast, sponges have 
not been recorded previously from Eocene localities in 
the basin, but are dominant at the newly discovered site. 
In this respect, the new unit resembles the Plantagenet 
Group of the Bremer and Eucla Basins on the southern 
margin of Western Australia (Gammon et al. 2000). 
Because of the abundance of robust diverse miliolid 
foraminifers and the low planktonic percentage (about 
10%), the new unit probably accumulated in inner neritic 
conditions (following Murray 1991), at water depths 
between about 10 and 30 m (based on unpublished 
observations of DW Haig for present-day assemblages 
along the Western Australian coast). This appears to be 
shallower than for the lower part of the Giralia 
Calcarenite type section (about 50 m water depth 
according to Haig et al. 1997), but deeper than for the 
Giralia Calcarenite at Yaringa and for the Merlinleigh 
Sandstone (see Fig 1). Based on the deduced water depth, 
the new unit should contain skeletal material belonging 
to groups such as larger benthic foraminifers, colonial 
corals, or coralline algae, if it is coeval with the Giralia 
Calcarenite and Merlinleigh Sandstone. Their apparent 
absence, however, implies that it is somewhat different 
in age to these units. 
Discussion 
The faunal composition of the new unit implies that 
climatic cooling in the Southern Carnarvon Basin took 
place during the later Eocene after about 40.5 Ma 
(BKSA95). McGowran et al (2000) recorded a similar 
cooling for the later Eocene in southern Australian 
110 
