Haig & Mory: Siliceous, later Eocene from Kalbarri 
basins, but the foraminiferal assemblage recovered from 
Kalbarri does not allow a precise correlation with the 
southern Australian cooling events. The interregional 
correlations may only be confirmed by study of thicker, 
better preserved sections of the Eocene on the North 
West Shelf (see Apthorpe 1988), if continuously cored 
sections become available there. 
The new discovery adds to knowledge of the erosion 
history of the basin prior to 41.5 Ma. Erosion of between 
25 and 250 m of Cretaceous, and possibly also Paleocene 
and lower Eocene strata, is estimated to predate deposition 
of the shallow-water Eocene. The lower estimate is based 
on the thickness of the Cretaceous Alinga Siltstone and 
Toolonga Calcilutite preserved below calcrete on the 
Pillawarra Plateau 22 km north-west of the new location. 
The upper estimate is based on the maximum thickness of 
the Toolonga Calcilutite and overlying Cretaceous and 
Paleocene units further north in the basin. Below the type 
section of the Giralia Calcarenite, all units down to the 
Windalia Radiolarite were deposited in mid- to outer 
neritic settings on a broad, gently inclined continental 
shelf. The facies in these units are laterally uniform and, 
although there are hiatuses within the Cretaceous to 
Paleocene succession, they do not indicate major erosion 
even though the thicknesses of the units vary ( e.g . see 
Dixon et al 2003a, b). 
Zones P12-P16 (including outcrops of the Giralia 
Calcarenite, the new unit, and the Merlinleigh Sandstone) 
encompass a variety of depositional settings in the 
Southern Carnarvon Basin (Fig 1). Sediment deposited at 
that time overlies lowest Eocene at the type section of the 
Giralia Calcarenite (Haig et al 1997); Campanian (Upper 
Cretaceous) at Yaringa (Belford 1960); Lower Permian at 
the Merlinleigh Sandstone type section (Condon 1968); 
and Aptian (Lower Cretaceous) at the new locality. This 
implies a significant episode of erosion in the basin 
during the late part of the Early and early part of the 
Middle Eocene (about 53 Ma to 41.5 Ma BKSA95). The 
differences in present heights of the Eocene units in the 
Southern Carnarvon Basin (see Fig 1) are probably the 
result of late Neogene uplift, which also elevated 
underlying Cretaceous strata at the new site by about 60 
m relative to the position of equivalent units on 
Murchison House Station, 22 km to the northwest (Fig 2). 
Whatever caused the Early to Middle Eocene erosional 
event in the Southern Carnarvon Basin also affected the 
southern margin basins (as there is no record for most of 
this interval in southern or continental Australia, 
according to McGowran et al 2000). Coevally, along the 
northern margin in the Papuan Basin and on the 
southern Papuan Peninsula there was a change from 
Cretaceous-Paleocene generally deep-water uniform 
calcareous mudstone facies to diverse inner neritic 
Middle Eocene shallow-water limestones (Haig et al 
1993). 
The three main conclusions that arise from the new 
discovery are; 
1) the new unit, which was deposited in the shallow 
inner neritic zone, represents the youngest known 
Eocene in the Southern Carnarvon Basin, and 
appears to belong within planktonic foraminifera 
Zones P13 to P16 of Middle to Late Eocene age 
(40.5 - 34.0 Ma BKSA95); 
2) significant cooling within the basin apparently 
took place during the later Eocene after 40.5 Ma; 
and 
3) a major episode of erosion is inferred during the 
50 - 41.5 Ma interval (late Early to early Middle 
Eocene) preceding deposition of the Middle 
Eocene units. 
Acknowledgements: The Western Australian Department of Conservation 
and Land Management is thanked for granting us permission to collect 
material from the newly discovered unit. We thank David Barton of 
Kalbarri for sharing his knowledge of the area and guiding us to the site, 
Tony Cockbain for alerting us to the new unit, which was assumed to be 
part of the Windalia Radiolarite, and Brian McGowran and Ken 
McNamara for improving the manuscript. Logan Barber, Ben Hammond 
and Rowena Pallister are thanked for assistance with drafting and 
manuscript preparation. AJM publishes with the permission of the 
Director of the Geological Survey of Western Australia. 
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Ill 
