Grossplots are compilations of globally distributed palaeotemperature data
onto latitude versus age plots, which are then contoured. The results
specifically show the distribution of temperature over the globe and its
variations over the Cretaceous to Middle Miocene interval. Data for continents
and oceans are plotted separately in this investigation, and each such
grossplot is in accord with the known climate changes of this time. The
general scarcity of quantitative palaeotemperature information for Australia
can be rectified by deriving, from the global continental grossplot, the
relationship between mean annual temperature and latitude. When these are
applied to the latitude band progressively occupied by Australia, the
following observations can be made: (1) during the Early Cretaceous, the
south-east of the continent was subjected to freezing wintertime temperatures;
(2) peak warming of northern Australia was attained in the
Turonian–Santonian, but this was followed by cooling later in the
Cretaceous; (3) Early Tertiary warming until the Late Eocene particularly
affected the northern half of the continent, but this region then underwent
the most severe cooling in the Early Oligocene; (4) subsequently, the whole of
the continent cooled uniformly from conditions only slightly warmer than at
present. Despite Australia’s equatorward march, the Late Cretaceous to
Palaeocene climates of the continent have been influenced more effectively by
changes in the global climate state. However, global cooling since the Eocene
has been less effective than drift in controlling the warming climate of
Australia. The time–space distribution of precipitation over Australia
is estimated from the global relationship between terrestrial temperature and
rainfall. The Eocene experienced the heaviest rainfall (> 1560 mm
year-1, in the north only), and the Eocene to Middle
Miocene experienced moderately high rates (> 500 mm
year-1 in the northern three-quarters of the continent).
Tertiary brown coals in southern regions were formed in proximity to areas of
high rainfall. Continentwide low rates (< 500 mm
year-1; semi-arid) are suggested for the Cretaceous,
except for wet conditions in the north during the Albian–Santonian and
the Late Maastrichtian. Estimates of precipitation are subject to factors such
as continentality and location of moisture sources, which cannot be evaluated
at present.
Middle-late Eocene dinoflagellate cysts from NE Ukraine (Borehole No. 230, Dnepr-Donets Depression): stratigraphic and palaeoenvironmental approach