List of contributors 1. The Australian fossil plant record: an introduction R. S. Hill 2. Maps of late Mesozoic-Cenozoic Gondwana break-up: some palaeographical implications G. E. Wilford and P. J. Brown 3. The background: 144 million years of Australian palaeoclimate and palaeogeography P. G. Quilty 4. Palaeobotanical evidence for Tertiary climates D. R. Greenwood 5. Landscapes of Australia: their nature and evolution G. Taylor 6. Patterns in the history of Australia's mammals and inferences about palaeohabitats M. Archer, S. J. Hand and H. Godthelp 7. Australian Tertiary phytogeography: evidence from palynology H. A. Martin 8. Cretaceous vegetation: the microfossil record M. E. Dettmann 9. Cretaceous vegetation: the macrofossil record J. G. Douglas 10. Early Tertiary vegetation: evidence from spores and pollen M. K. Macphail, N. F. Alley, E. M. Truswell and I. R. K. Sluiter 11. The early Tertiary macrofloras of continental Australia D. C. Christophel 12. Cenozoic vegetation in Tasmania: macrofossil evidence R. J. Carpenter, R. S. Hill and G. J. Jordan 13. The Neogene: a period of transition A. P. Kershaw, H. A. Martin and J. R. C. McEwen Mason 14. The Oligo-Miocene coal floras of south-eastern Australia D. T. Blackburn and I. R. K. Sluiter 15. Quaternary vegetation G. S. Hope 16. The history of selected Australian taxa R. S. Hill Taxonomic index General index.

/pdf/history-of-the-australian-vegetation-cretaceous-to-recent-2k43t2lib3.pdf

History of the Australian vegetation : cretaceous to recent

Seismic reflection profiles across the Hikurangi Plateau Large Igneous Province and adjacent margins reveal the faulted volcanic basement and overlying Mesozoic-Cenozoic sedimentary units as well as the structure of the paleoconvergent Gondwana margin at the southern plateau limit. The Hikurangi Plateau crust can be traced 50–100 km southward beneath the Chatham Rise where subduction cessation timing and geometry are interpreted to be variable along the margin. A model fit of the Hikurangi Plateau back against the Manihiki Plateau aligns the Manihiki Scarp with the eastern margin of the Rekohu Embayment. Extensional and rotated block faults which formed during the breakup of the combined Manihiki-Hikurangi plateau are interpreted in seismic sections of the Hikurangi Plateau basement. Guyots and ridge-like seamounts which are widely scattered across the Hikurangi Plateau are interpreted to have formed at 99–89 Ma immediately following Hikurangi Plateau jamming of the Gondwana convergent margin at ∼100 Ma. Volcanism from this period cannot be separately resolved in the seismic reflection data from basement volcanism; hence seamount formation during Manihiki-Hikurangi Plateau emplacement and breakup (125–120 Ma) cannot be ruled out. Seismic reflection data and gravity modeling suggest the 20-Ma-old Hikurangi Plateau choked the Cretaceous Gondwana convergent margin within 5 Ma of entry. Subsequent uplift of the Chatham Rise and slab detachment has led to the deposition of a Mesozoic sedimentary unit that thins from ∼1 km thickness northward across the plateau. The contrast with the present Hikurangi Plateau subduction beneath North Island, New Zealand, suggests a possible buoyancy cutoff range for LIP subduction consistent with earlier modeling.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2007GC001855

Hikurangi Plateau: Crustal structure, rifted formation, and Gondwana subduction history

Numerical models for diagenesis and the Neogene Sr isotopic evolution of seawater from DSDP Site 590B

The transition from the Eocene to the Oligocene Epochs, from about 40 to 30 Ma (million years ago), was the most significant interval in Earth history since the dinosaurs died out 65 Ma. From the warm, equable "greenhouse" climate of the early Eocene (a relict of the age of dinosaurs), the Earth experienced major climatic changes. Global temperature plum­ meted, and the first Antarctic ice sheets appeared. These climatic stresses triggered extinctions in plants and animals, both on land and in the oceans. By the early Oligocene (33 Ma), the Earth had a much cooler, more temperate climate, with a much lower diversity of organisms. Indeed, the Eocene-Oligocene transition marked the change from the global "green­ house" world of the Cretaceous and early Cenozoic to the glaciated "ice house" world of today. Despite the intense research interest in mass extinctions over the past two decades, the Eocene-Oligocene extinctions have been relatively under­ studied and misunderstood. While hundreds of papers have been published on the terminal Cretaceous extinction of dinosaurs and ammonites since the discovery of the iridium anomaly in 1980, only a few dozen articles have been published on the Eocene-Oligocene extinctions. Much of this work has now been invalidated by new data. In the enthusiasm to force the Eocene-Oligocene extinctions into the mold of the Cretaceous-Tertiary impact hypothesis and the periodic extinc­ tion hypothesis (Raup & Sepko ski 1984), a lot of misinformation has appeared. Typically, impact proponents treat the Eocene-Oligocene tran-

The late eocene-oligocene extinctions

Tectonics and climate are both directly and indirectly related. The direct connection is between uplift, atmospheric circulation, and the hydrologic cycle. The indirect links are via subduction, volcanism, the introduction of gasses into the atmosphere, and through erosion and consumption of atmospheric gases by chemical weathering. Rifting of continental blocks involves broad upwarping followed by subsidence of a central valley and uplift of marginal shoulders. The result is an evolving regional climate which has been repeated many times in the Phanerozoic: first a vapor-trapping arch, followed by a rift valley with fresh-water lakes, culminating in an arid rift bordered by mountains intercepting incoming precipitation. Convergence tectonics affects climate on a larger scale. A mountain range is a barrier to atmospheric circulation, especially if perpendicular to the circulation. It also traps water vapor converting latent to sensible heat. Broad uplift results in a shorter path for both incoming and outgoing radiation resulting in seasonal climate extremes with reversals of atmospheric pressure and enhanced monsoonal circulation. Volcanism affects climate by introducing ash and aerosols into the atmosphere, but unless these are injected into the stratosphere, they have little effect. Stratospheric injection is most likely to occur at high latitudes, where the thickness of the troposphere is minimal. Volcanoes introduce CO2, a greenhouse gas, into the atmosphere. Geochemical effects of tectonic uplift and unroofing relate to the weathering of silicate rocks, the means by which CO2 is removed from the atmosphere-ocean system on long-term time scales.

Tectonics and climate

Late Eocene-early Oligocene (42–35 Myr) sediments cored at two DSDP sites in the south-west Pacific contain evidence of a pronounced increase in local volcanic activity, particularly in close association with the Eocene–Oligocene boundary. This pulse of volcanism is coeval with that in New Zealand and resulted from the development of an Indo- Australian / Pacific Plate boundary through the region during the late Eocene. The late Eocene / earliest Oligocene was marked by widespread volcanism and tectonism throughout the Pacific and elsewhere, and by one of the most important episodes of Cenozoic climatic cooling.

C.E. Barton

Papers

Palaeotectonic implications of increased late Eocene—early Oligocene volcanism from South Pacific DSDP sites

Deep-Sea Drilling Project Leg 90: The South Pacific Cenozoic