OFR 151.pdf - CRC LEME

6.7 Time Slice K-6. Late Campanian-Maastrichtian [~70-65 Ma]
Zones: Tricolporites lilliei to Forcipites longus Zones
Isabelidinium korojonense to Manumiella druggii Zones
6.7.1 Palaeogeography
By the end of the Late Cretaceous, Australia had become the ‘island continent’, separated
from Antarctica by a shallow seaway across the South Tasman Rise, and possessing most of
the major topographic features found today (Veevers et al. 1991, Langford et al. 1995). For
example, fully oceanic conditions existed along the western and northwestern margins. The
Eastern Highlands, which extended from Tasmania to northeastern Queensland, had been
uplifted sufficiently to be a major source of sediment for the flanking basins. Fossil land
surfaces preserved beneath Paleocene basalts indicate the Southeastern Highlands of New
South Wales had reached an elevation of ca. 800 m during the Late Cretaceous. Precursors of
the modern large inland river systems were established on both sides of the continent by the
same time. Conversely, land-bridges connecting the mainland with Tasmania and New
Guinea were not yet submerged and continent margin basins such as the Gippsland Basin
continued to be foci for fluvio-lacustrine deposition, albeit subject to occasional marine
flooding.
6.7.2 Palaeobotany
In contrast to the Early Campanian, many Late Campanian and Maastrichtian angiosperm
pollen types are large and sometimes highly ornamented, with morphologically complex
apertures. The trend is most evident in the Proteaceae but is also seen in clades producing
tricolpate and tricolporate pollen. The phenomenon is presumed to represent adaptive
radiation associated with tectonic or volcanic activity and, on the broader geographic scale,
opening and enlargement of the southern oceans (Dettmann 1992, 1994, Wing et al. 1993).
Relatively few of the types first appearing during the Late Cenomanian and Maastrichtian
have been formally defined as fossil species; fewer still can be linked to extant plants in any
ecologically meaningful way since most became extinct at the end of the Maastrichtian. One
possible exception is Tricolporites lilliei, which may related to the tropical freshwater swamp
genus Neoscortechinia (Euphorbiaceae).
A number of immigrant taxa appear to have reached Australia by long distance dispersal from
landmasses to the north-west. The clearest example is the Lactoridaceae (Lactoripollis),
which is recorded in South-west Africa during the Turonian and in northern Australia (and
India) during the Campanian (Macphail et al. 1999, A.D. Partridge pers. comm.). Other
examples are possible members of the important Northern Hemisphere Normapolles
(Myrtaceoipollenites) and Triprojectites (Integricorpus) clades, which may have reached
northern Australia as early as the Late Campanian (cf. Jarzen & Dettmann 1992, A.D.
Partridge and M.K. Macphail, unpubl. results). More generally, the floras show strong
provincialism along north to south and east to west gradients. For example, Gambierina spp.,
which are common to abundant in Late Maastrichtian microfloras in the south-east, are rare to
absent in central and northern Australia. The same is true for Dacrycarpus and Dacrydium
(including the extinct Lygistepollenites balmei clade). Small (mostly undescribed) tricolpate
and tricolporate grains are more common in sites on the northern margin and these
microfloras also include taxa that are not recorded in southeastern Australia until the
Palaeogene, such as palms and Anacolosa.
6.7.3 Palaeoclimates
In global terms, the Late Campanian-Maastrichtian, like the Early Albian, is viewed as a
relatively cool stage within the Cretaceous (Jenkyns and Wilson 1999). Cooling may have
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