Changing Cenozoic Barriers and the Australian Paleobotanical Record

The first part of this study reconstructs the changing Cenozoic environment of continental drift, о, and climate.The northward movement of Australia brought it into collision with Southeast Asia in Miocene time.Throughout the Cenozoic, New Zealand has remained in approximately the same relative position and the same distance from Australia.Tectonics within Australia have been minor, gentle, and the main topographic features have probably existed in much the same form all well as the Quaternary.Today, the arid center of the continent is the major feature of the climate.Soils are generally low in fertility, and have been low all through the Cenozoic, when some soils may have been even less fertile than those of toda e vegetation today, there are small and disjunct areas of closed forest (-rainforest) in the better watered northern and eastern coastal regions.Eucalyp tus do ipsae forests and scrublands cover the major area.Grasslands and shrublands are found in cThe second half presents the paleobotanical record of all reliable бепййсачопв of тасго-and micro-fossils, first appearances and the quantitative relationships of the abundant pollen groups.The found in the Miocene en Australia, and open savannah and/or he arm e domin in southeastern Australia in the Pleistocene.The vegetation was not necessarily more uniform than that seen my for there is considerable evidence of geographic uM ime lated, аай in the ми һе po shows cyclic changes of a more open and drier kind of vegetation in glacial M. pu a more forested, wetter vegetation in the interglacials.A comparison of the Australian and New Ze aland paleobotanical records shows a general similarit a of both has been similar, and distance has not been an insurmountable barrier.The paleobotanical record of Southeast Asia is different, and limited Sepe.after the Miocene are probably associated with uplift.During the Miocene, there is an increase in Myrtaceae in both Australia and Southeast in Australia.Climate is the most important environmental factor, for the paleobotanical and paleoclimatic records usually go together.Climate has probably not been a barrier within Aust ralia for most of the spread.Within Australia, tectonics and topography have not been barriers, although they have been important in maintaining habitat diversity.These factors may have been more important as barriers between PM and Southeast Asia.This study shows a complex, continuously changing, interwoven environment and flora, rather than migrations stopped or брутна ЯЕ by changing barriers.The concepts of barriers and migrations 1 This paper was presented at the symposium ''Plant Geographical Results of Changing Cenozoic Barriers" at the XIII International ya br AE Sydney, Australia, 1981.