Publication Name: Second South-Eastern Australia Oil Exploration Symposium - Technical Papers
Authors: H.A. Martin
Date Published: December 1986
Number of Pages: 23
Reference Type: Book Section
Abstract:
The palynology of the Upper Eocene to Middle Miocene sediments of the Murray Basin fits the accepted scheme of zonation but the scheme does not give sufficient stratigraphic control, especially in thick sections which fall within the one zone. A method using the abundance of certain taxa, or 'quantitative events', has been devised and is shown to be stratigraphically reliable, at least for local correlation.Attempts to extrapolate from one region to another may not be successful for, although the same quantitative
event may be present, its stratigraphic expression in another region may be different. The quantitative events are controlled by ecologic factors and an explanation of variation from one region to another is found in the palaeoecology.
Abundant Myrtaceae (Late Oligocene to earliest Miocene) are the most widespread quantitative event in the basin. There is evidence that abundant Myrtaceae may start earlier in the west than in the east, although the eastern, non-marine section is poorly dated. This change from abundant Nothofagidites to abundant Myrtaceae was climatically controlled and probably marks the first step of a drier climate, leading eventually to the present aridity.
The Middle Tertiary hiatus cannot be detected lithologically in the non-marine sediments. It is thought that a good cover of vegetation would minimise erosion at a time of low sea level. At times of high sea level, with poor drainage and a swampy terrain, taxa requiring a wetter habitat become abundant. With low sea levels, improved drainage and a lowered water table, taxa requiring a drier habitat may become abundant. Consequently, the palynology may be sensitive to eustasy.