OFR 151.pdf - CRC LEME

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Temperature Climates in palaeo-southern Australia appear to have cooled (lower mesotherm-microtherm). Warmer (upper mesotherm) conditions are recorded in palaeo-northern Australia (present-day northwestern Australia). Rainfall Precipitation may have decreased (humid range) or become more seasonal in southeastern Australia. Seasonality Seasonal contrasts in temperature are likely to have remained strong due to the location of the continent at high palaeolatitudes. iii. Tertiary Climates With few exceptions, only Late Neogene climates can be reconstructed in quantitative terms. Photoperiod Low light intensities ceased to be an important forcing factor during the Late Paleocene. Temperature Warming during the Paleocene culminated in maximum Tertiary warmth during the early Early Eocene when very warm to hot (upper mesotherm-megatherm) temperatures are recorded in northwestern, central, southwestern, central southern and southeastern mainland Australia and, locally, in western Tasmania. The clearest indication of the impact of abrupt warming during the PETM is the presence of a tropical mangrove palm (Nypa) at a palaeolatitude of 66 0 S in Macquarie Harbour on the West Coast of Tasmania. Locally warm (mesotherm range) climates persisted into late Early Eocene time in Macquarie Harbour and in the Gippsland Basin in southeastern Victoria, and into Middle-Late Eocene time in the Polda and St. Vincent Basins in southwestern South Australia. Temperatures in coastal northeastern Queensland were relatively cool (lower mesotherm) during the Early Eocene, possibly due to cool currents flowing northwards along the eastern margin. Very warm to hot (megatherm range) climates persisted in northwestern Australia throughout the Middle-Late Eocene and similar (upper mesotherm) conditions first developed in northeastern Australia during the Oligo-Miocene. Temperatures in northern Australia are likely to have remained very warm to hot throughout the Neogene due to rapid northward drift of the continent, despite the global cooling trend. Temperatures in central and southern Australia decreased (mesotherm range) during the Middle Eocene although there is weak evidence for temporary warming in southeastern Australia during the late Eocene Abrupt cooling associated with the development of the Circum-Antarctic Current is recorded in southeastern Australia during the Eocene-Oligocene transition. The effects were most severe in Tasmania where the event is associated with transient glaciation (Lemonthyme Glaciation) on the north-west Central Plateau. The same event is reflected in major impoverishment of the temperate rainforest flora in the Gippsland Basin. Temperatures in central southern and southwestern Australia remained relatively warm (lower mesotherm), probably due to warm water 'gyres' within the Bight. 23
Conditions in southern Australia appear to have been milder (mesotherm range) during the Early Miocene than during the Early to Late Oligocene or Middle to Late Miocene. Climates in coastal southwestern and central southern Australia were warmer (mesotherm range) during the Early Pliocene than during the Late Pliocene or Quaternary. The warm phase correlates with the mid Pliocene warm event recorded elsewhere at middle-high latitudes. Rainfall Precipitation appears to have increased during the Paleocene. The Early Eocene warm period is associated with wet to very wet (perhumid) conditions across the continent, including in central and northwestern Australia where rainfall may have become strongly seasonal (possibly monsoonal). Similar conditions persisted into Middle-Late Eocene time except that rainfall became more variable (possibly less reliable) in central and southwestern Australia and more uniformly distributed (or more reliable during summer months) in southeastern Australia. By Oligo-Middle Miocene time, subhumid conditions prevailed in north-west Australia and there is limited evidence for a decrease in rainfall (humid range) in central and southwestern Australia. Rainfall remained perhumid in the north-east, central south and south-east mainland Australia and in Tasmania. There is weak evidence for wetter conditions in central southern and southwestern Australia, and relatively strong evidence for wetter conditions on the Southeastern Highlands, during the Mid Pliocene warm phase. One site in south-west Western Australia (Yallalie) provides unequivocal evidence for three periods of aridification, at 2.9 Ma, 2.59 Ma and 2.56 Ma, during the same period. The vegetation response is broadly similar to that observed during Quaternary glacial-interglacial cycles, and parallels the development of continental ice sheets in the Northern Hemisphere. By Late Pliocene time, essentially modern bioclimatic regimes were in existence. Seasonality Seasonality, measured by the seasonal distribution and, in central and northwestern Australia, the reliability of rainfall, increased markedly during the Late Palaeogene and Neogene. The trend included a steep increase in the lapse rate (decrease in air temperature with increasing elevation), which may have been associated with decreasing CO2 levels. II. FUTURE DIRECTIONS For most geological epochs, the Australian palaeobotanic record is commensurate with records preserved on other landmasses in the Southern Hemisphere. Two Australian sequences however, preserve exceptionally detailed records for short periods of geological time. These are (1) the 34 m long Lemonthyme Creek sequence in north-west Tasmania, which is likely to correlate with the development of the Circumantarctic Current during the Eocene-Oligocene transition, and (2) the 110 m thick Yallalie sequence in south-west Western Australia, which correlates with the initiation of continental ice-sheet development in the Northern Hemisphere. Early Eocene sequences preserved at Regatta Point near Strahan in western Tasmania, may preserve a detailed record of the PETM as well as its continuing impact at this high palaeolatitudes site throughout the Early Eocene. Application of objective (statistical) techniques used to extract palaeoclimatic data from Late Quaternary palynosequences is likely to improve the reliability of Cretaceous and Tertiary climate reconstructions in Australia. These are Isopollen Mapping (Birks and Birks 1980), Biome Analysis (Prentice and Webb 1998) and Principal Components Analysis, respectively. 24
Page 1 and 2: CRCLEME Cooperative Research Centre
Page 3 and 4: Electronic copies of the publicatio
Page 5 and 6: and, for Tertiary continental seque
Page 7 and 8: 2. Analysis of a Plio-Pleistocene l
Page 9 and 10: Table A (cont.) Basin and related s
Page 11 and 12: Figure A: Generalised climatic curv
Page 13 and 14: Carpenter, R.J., Hill, R.S., Greenw
Page 15 and 16: Hill, S.M., Eggleton, R.A. and Tayl
Page 17 and 18: Macphail, M.K. and Stone, M.S., 200
Page 19 and 20: Swenson, U., Backlund, McLoughlin,
Page 22 and 23: EXECUTIVE SUMMARY This review prese
Page 26 and 27: SUMMARY OF INFERRED CRETACEOUS PALA
Page 28 and 29: INTRODUCTION Mineral resources, whe
Page 30 and 31: Professor B. Balme (Geology Departm
Page 32: Section 7 (Tertiary climates) This
Page 35 and 36: vegetation. Moreover, individual ta
Page 37 and 38: 1.3 Flora, vegetation and climate 1
Page 39 and 40: TABLE 2: Classification of vegetati
Page 41 and 42: Figure 2: Relationship of different
Page 43 and 44: Accordingly, only at sites with exc
Page 45 and 46: 2.1.3 Palaeoecology Palaeoecology i
Page 47 and 48: wind-pollinated trees and shrubs bu
Page 49 and 50: 1. The usual practice of equating t
Page 51 and 52: 1. Palaeontological evidence Like p
Page 53 and 54: 5. Facies architecture and lithostr
Page 55 and 56: Subsequent developments include mel
Page 58 and 59: SECTION 4 (GEOGRAPHIC BOUNDARIES AN
Page 60 and 61: SECTION 5 (EARLY CRETACEOUS CLIMATE
Page 62 and 63: events on other continents and sugg
Page 64 and 65: If these considerations apply to th
Page 66 and 67: surrounding basins. Thick sands ero
Page 68 and 69: Haig and Lynch 1993, Erbacher et al
Page 70 and 71: SECTION 6 (LATE CRETACEOUS CLIMATES
Page 72 and 73: has highlighted the roles played by
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6.4.2 Palaeobotany Cenomanian flora
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Palaeo-southern Australia Dryland c
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6.7 Time Slice K-6. Late Campanian-
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7.1. Global backdrop SECTION 7 (TER
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Explanations for the PETM are centr
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East Antarctica and strengthening o
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amplifying, pacing and potentially
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southeastern Australia than elsewhe
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7.4 Time Slice T-1. Paleocene [65-5
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Palaeo-southern Australia Unlike no
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Palaeo-central Australia As for the
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7.6.2 Palaeobotany The palaeobotani
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Zone microfloras imply temporary wa
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in the Bass Basin, the basal Seaspr
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Similarly it is difficult to summar
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However, the data are emphatic that
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margin of plateau were cooler (~7 0
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fossil taxa that are morphologicall
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during Late Pleistocene glacial max
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SECTION 8 (CONCLUSIONS) Climatic in
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• On present indications, Early C
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TABLE 8a: INFERRED CRETACEOUS PALAE
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8.2 Results in prospect (recommenda
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The 10 μm sieved, oxidised extract
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phenology. The method also provides
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SECTION 9 (REFERENCES) Acton, G.D.
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Ashley, P.M., Duncan, R.A. and Feeb
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Birks, H.J.B. and Gordon, A.D., 198
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Burnham, R.J., 1989. Relationships
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Clarke, J.D.A., 1994. Evolution of
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Dettmann, M.E. and Playford, G., 19
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Evans, P.R., 1970b. Palynology of H
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Godthelp, H., Archer, M., Cifelli,
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Harris, W.K., 1974. Biostratigraphy
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Hill, R.S., 1994b. Nothofagus smith
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Holland, S.M. and Patzkowsky, M.E.,
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Australia: paleoceanographic implic
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Lindsay, J.M. and Harris, W.K., 196
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Macphail, M.K., Colhoun, E.A. and F
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McGowran, B. and Beecroft, A., 1985
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Morgan, R., 1977. Palynology of Ter
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Abstracts of the Annual General Mee
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Raymo, M.E., Grant, B., Horowitz, M
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Sereno, P.C., 1999. The evolution o
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Taylor, G., 1998. Prediction of mod
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Webb, L.G., 1968. Environmental rel
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Zachos, J.C., Stott, L.D. and Lohma
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APPENDIX 1 CRETACEOUS DATA 167
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1. TIME SLICE K-1 Age Range: Berria
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Australian assemblages, located on
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2. Officer Basin Dinoflagellates in
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2. TIME SLICE K-2 Age Range: Aptian
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Inferred climate The combined data
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Dettmann et al. (1992) have argued
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3. TIME SLICE K-3 Age Range: Cenoma
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3.2.2 North-East Australia 1. Carpe
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4. TIME SLICE K-4 Age Range: Turoni
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1. Otway Basin Limited data (Macpha
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5. TIME SLICE K-5 Age Range: Early
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Inferred climate The data indicate
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6. TIME SLICE K-6 Age Range: Late C
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Contrary to global cooling trends d
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Inferred climate The relatively goo
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Inferred climate As for regions to
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APPENDIX 2 TERTIARY DATA 201
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1. TIME SLICE T-1 Age Range: Paleoc
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also include relatively frequent No
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Inferred climate Some differences b
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Microfloras preserved in the Lower
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subtropical affinities are rare, hi
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2. TIME SLICE T-2 Age Range: Early
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Inferred climate Climates appear to
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northern New South Wales. The assem
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2.2.5 Central southern Australia Ha
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a number of distinctive Proteaceae
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Inferred climate The Regatta Point
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3. TIME SLICE T-3 Age Range: Middle
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2. Lake Torrens Basin Abundant leaf
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Dominance is highly variable. For e
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types (M.K. Macphail unpubl. data).
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Dacrycarpus), Euphorbiaceae (Austro
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(possibly upper mesotherm) and drie
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Basin) on the Eyre Peninsula (Alley
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explanation is that a warm water gy
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several taxa, which first appear in
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4. TIME SLICE T-4 Age Range: Oligoc
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Inferred climate The southern limit
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The lowest and possibly the oldest
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Dominants include fresh to brackish
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Based on the relative abundance of
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(Morgan 1977, McMinn 1981a, Martin
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common (up to 5-6%) in the middle s
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Polypodiaceae, Palmae (Dicolpopolli
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Strasburgeriaceae. Proprietary info
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Rare taxa which first appear in the
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Correlative microfloras in the onsh
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impression of floristic impoverishm
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(Lophosoria) reached Tasmania befor
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2. Otway Basin Oxygen isotope strat
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5. TIME SLICE T-5 Age Range: Late M
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Casuarinaceae, Cunoniaceae, Elaeoca
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maximum temperature of the hottest
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Nothofagus-gymnosperm temperate rai
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5.2.7 Tasmania Late Neogene sedimen
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