From Greenhouse to Icehouse – The Eocene/Oligocene - UMass ...

afting. Late Oligocene time saw repeated ice expansions recorded in the
CIROS-1 core by a succession of basal tills, and probably by the major
unconformity in Prydz Bay. Subsequently, frequent expansions took place to
the shelf edges in both areas, resulting in a fragmented stratigraphic record.
8.3. Climate Signals from the Terrestrial Realm – Fossil Plants
and Palynomorphs
8.3.1. Plant Macrofossils
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From Greenhouse to Icehouse – The Eocene/Oligocene in Antarctica 325
An important source of palaeoclimate information on land comes from fossil
plants (both macro- and microfossils) (Fig. 8.7). The fossil plant record
suggests that during the Late Palaeocene to Early Eocene moist, cool
temperate rainforests were present, similar to modern low to mid-altitude
Valdivian rainforests in southern Chile. These forests were dominated by
Nothofagus and conifer trees, with ferns, horsetails and some less-prominent
angiosperm groups. Assemblages of Eocene fossil plants and palynomorphs
signal a generally warm climate during the Early Eocene but conditions
deteriorated throughout the Antarctic Peninsula through the latter part of
the Eocene when cold, seasonal climates developed (Francis, 1991; Francis
and Poole, 2002; Francis et al., 2004, 2008; Poole et al., 2005).
Fossil plant assemblages of younger age have been found in glacial
sediments in the Transantarctic Mountains, representing vegetation that
grew on Antarctica under icehouse conditions. These include the Sirius
Group flora from the Transantarctic Mountains (the age of which is
problematic, Francis and Hill, 1996; Wilson et al., 1998a,b; Askin et al.,
1999), and a new flora of Miocene age discovered in the Dry Valleys
(Ashworth et al., 2008). Surprisingly, leaf fossils, although single leaves, have
also been discovered in drill cores within Oligocene and Miocene glacial
sequences. The early glacial world of Antarctica was clearly not totally
barren of vegetation.
Palaeogene fossil plants have been discovered from around the Antarctic
margin in outcrop, in sea-floor cores and in glacial erratic boulders from the
Antarctic Peninsula (King George Island and Seymour Island) and Ross Sea
(McMurdo Sound and Minna Bluff) regions. The collections consist of
compressions, impressions and petrifactions of leaves, seeds, flowers and
wood indicating a high southern latitude flora of variable diversity but
dominated by fossils comparable to modern Nothofagus (the southern beech)
and conifer trees. Ferns, horsetails and additional significant Southern