Journal of the Royal Society of Western Australia, 86:107-113, 2003 
New record of siliceous, marine, later Eocene 
from Kalbarri, Western Australia 
D W Haig 1 & A J Mory 2 
'School of Earth arid Geographical Sciences, The University of Western Australia, 
35 Stirling Highway, Crawley WA 6009 0 dhaig@geol.uwa.edu.au 
Geological Survey of Western Australia, 100 Plain Street, East Perth WA 6004 
0 arthur.mory@doir.wa.gov.au 
(Manuscript received May 2003; accepted September 2003) 
Abstract 
Weathered residue of a previously undetected thin Eocene unit at elevation of 220 m AHD east 
of Kalbarri includes silicified sponge-rich calcarenite and argillite. Sponges (intact forms and 
spicules) dominate the silicified fauna but common smaller benthic and planktonic foraminifers, 
molluscs (gastropods, bivalves, scaphopods, and nautiloids), bryozoans, solitary corals, and 
serpulid worms are also present. The planktonic foraminifers indicate that the unit lies within the 
Zone P13 to P16 interval of the Middle to Late Eocene (40.5 - 34.0 Ma BKSA95). In comparison to 
the Giralia Calcarenite of upper Zone P12, the fossil assemblage indicates that significant cooling in 
the shallow inner neritic zone apparently took place within the basin during the later Eocene. The 
ages of known marine Eocene occurrences in the basin, and the contrast between these and 
underlying formations, indicate major erosion during the interval 53 - 41.5 Ma (late Early to early 
Middle Eocene) preceding deposition of Zone P12-16 units. 
Key words: siliceous. Eocene, Kalbarri, sponges, foraminifers, molluscs. South Carnarvon Basin 
Introduction 
The marine Eocene in mainland Australia is best 
known from the southern margin of the continent 
(McGowran et al. 2000; Li et al. 2003). Outcrops of such 
strata in the Southern Carnarvon Basin have been 
recorded only north of about 26 °S (Fig 1; Haig et al. 
1997), and have been placed in two formations, the 
Giralia Calcarenite and the Merlinleigh Sandstone 
(Condon 1968; Hocking et al. 1987). Based on planktonic 
foraminifers, Haig et al. (1997) correlated the lower part 
of the type section of the Giralia Calcarenite to the upper 
part of Zone PI2 of Berggren Miller (1988), of Middle 
Eocene age (about 41.5 - 40.5 Ma according to the 
BKSA95 time-scale of Berggren et al. 1995). Haig et al. 
(1997) interpreted the entire formation at the type locality 
as the upper transgressive and lower highstand systems 
tract of one sequence, and suggested that this section 
represents a limited time interval. Outcrops of the 
formation at Red Bluff (north of Carnarvon) and Yaringa 
were correlated with the type section, as was the 
Merlinleigh Sandstone, although on much more tenuous 
evidence. Brunnschweiler (1962) had attributed the 
Merlinleigh Sandstone to the Middle Eocene (upper 
Cuisian or Lutetian) based on echinoids. 
This paper records a new discovery of an Eocene 
location near the southern margin of the Southern 
Carnarvon Basin (Fig 1) that is younger than other 
Eocene localities in the basin, and contains a cooler water 
fauna. The locality also allows a more precise age to be 
placed on a major interval of erosion that affected the 
entire post-breakup basin. Locality details are lodged in 
© Royal Society of Western Australia 2003 
the collection register of the E de C Clarke Geology 
Museum, The University of Western Australia. 
Description of site and stratigraphic relationships 
The locality lies 27 km east of Kalbarri at about 220 m 
AHD (Fig 2), and consists of scree dominated by iron- 
stained siliceous argillites with scattered large fragments 
of silicified bryozoans as well as large (up to about 30 
cm) intact siliceous sponges. A relatively clean sponge- 
spicule dominated arenite that includes silicified 
calcareous skeletal grains (including abundant 
foraminifers, and common gastropods and bryozoan 
fragments) is also present. The locality extends about 2 
km along a low breakaway capped by coarse-grained 
unfossiliferous silicified and ferrugenised pebbly 
sandstone probably less than 1 m thick. To the west and 
south, low exposures of Windalia Radiolarite are present 
no more than 5 m below the ferrugenised sandstone, 
thereby setting an upper limit for the thickness of the 
Eocene at this locality. 
Within the scattered rubble of Eocene argillite and 
silicified calcarenite are pebbles of siliceous porcellinite 
and silicified belemnite guards (Peratobelus) derived from 
the Late Aptian Windalia Radiolarite (Clarke & Teichert 
1948; Hocking et al 1987; Ellis 1993; Haig et al. 1996), 
implying that the Eocene lies unconformably on this 
Cretaceous unit. The Eocene unit is not formally named 
because no in situ outcrop is present; only the weathered 
residue of the unit remains at the studied locality. 
Eocene fossil assemblage and correlation 
All fossils recovered from the site are silicified or were 
originally siliceous ( e.g . sponges). Some of the original 
calcareous skeletons are chalcedonic internal moulds (e.g. 
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