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dated at 153 m.y. (Fig. 16-8), slightly post-dating the Callovian unconformity*.
As in the North Sea, abnormal pressures are encountered in the north-west
shelf of Australia in thick mudstones of Jurassic and Cretaceous age (Kyaw
Nyein et al., 1977). Some of the large accumulations of gas and condensate
are at normal hydrostatic pressures beneath the abnormally pressured mud-
stones.
Some of the record is on land. The Perth basin is half on land, half under
the sea, dominating the south-west coast of Australia. It is a north-south trend-
ing graben and half-graben, 800 km long, bounded by the Darling fault on
the east. Movement on the Darling fault since the early Permian has controlled
the accumulation of at least 6 km of sedimentary rocks on its downthrown
side, against the Precambrian shield to the east (Jones and Pearson, 1972;
Jones, 1976). Marine and non-marine sediments accumulated from the early
Permian. The rate of accumulation, controlled largely by movement on the
Darling fault, peaked during the late Jurassic (4 km) and early Cretaceous (6
km) with intense fault activity. This ceased during the Neocomian, and tilted
fault blocks were eroded. A marine transgression followed in late Cretaceous
times, with only minor fault movement. Carbonates accumulated during the
Tertiary. Thus the Perth basin acquired similar characteristics to the north-
west shelf.
The southern Perth basin (Cope, 1972) is a graben in Precambrian base-
ment, bounded to the east by the Darling fault, and to the west by the Duns-
borough fault. In this graben accumulated about 6 km of Permian to lower
Cretaceous sediments, and this is the throw on both bounding faults**.
The south coast of Australia, along the Great Australian Bight, has similar
character to the northern Perth basin and north-west shelf, but rocks older
than Cretaceous are not known (Pattinson et al., 1976). The Mesozoic is fault-
ed by normal faults, but these barely affect the Tertiary sequence. Movements
on faults from late Jurassic to late Cretaceous is inferred, with some moving
later. In parts of the Bight, sediment accumulation was erratic from late Cam-
panian to the Paleocene. This was followed by a middle Miocene transgres-
sion, then a prograding carbonate shelf.
Around the south-east corner of mainland Australia are three basins - the
Otway, Bass and Gippsland - of which the easternmost is the main petro-
leum province of Australia (Ellenor, 1976; Brown, 1976; Threlfall et al., 1976)

* Another point of interest in Barber’s paper is the report of geothermal gradients in a sedi-
mentary column in deep water. In Jupiter 1 and Mercury 1, this was found to be 25.3OC/
km from a surface temperature of 15.6OC; and in Saturn 1, it was 34OC/km.
** There is absolutely no evidence of a Mesozoic sequence of any thickness having accu-
mulated on Precambrian rocks outside the graben - to the contrary. Such a sequence, if
it had existed, would give the faults throws of more than 10 km and imply considerable
depths of burial of the graben sequence. The lack of metamorphism and the space problem
are evidence against this.