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A field appraisal of the role of plant opal in the Australian environment

posted on 2022-03-28, 10:24 authored by D. M. Hart
When plants die the plant opal they contain is subjected to processes both before and after it enters the soil. To date the use of plant opal has been largely confined to paleoenvironmental and archaeological research, where its relationship to the plant or plant community and its shape characteristics are of primary importance in the erection of assemblages of plant opal diagnostic of a particular environment. A comparison was made of the plant opal assemblages from the topsoil beneath several vegetation communities. Similar vegetation communities did not produce similar plant opal assemblages in the soil. Widely differing vegetation communities produced soil plant opal assemblages which differed very little. Once the plant opal has become separated from the host plant its botanical links become attenuated and its role as a mineral within the sediment assumes primacy. Periodic fire in the Australian environment exposes the plant opal to the effects of wind and running water which remove much of it while it is still in the litter layer. Large, platey sheets of plant opal are preferentially removed in this manner. In the litter layer, both the plant remains and the opal it contains are comminuted by the fauna. Soil fauna may selectively remove and store plant material containing a range of plant opal shapes which are then not found in representative amounts in the topsoil. The opal removed can vary from site to site and through time. These results suggest that plant opal could be used as a marker in pedological and geomorphic studies. This thesis presents a new view of plant opal as a constituent of sediments in its own right.


Table of Contents

Volume 1. Part 1. Introduction and field studies. Chapter 1. An overview of problems concerning plant opal -- Chapter 2. Initial field studies: Oxford Falls -- Chapter 3. Pilliga field studies I: Plant opal in litter -- Chapter 4. Pilliga field studies II: The distribution and mobility of plant opal in soils -- Chapter 5. Pilliga field studies III: Plant opal assemblages -- Chapter 6. Ecology reserve field study: fire and plant opal -- -- Part 2. Laboratory and field techniques. Chapter 7. Sample preparation and analysis -- Chapter 8. Litter study techniques -- Chapter 9. The morphology of plant opal - Part 1: Plant opal keys -- Chapter 10. The morphology of plant opal - Part 2: Plant opal assemblages -- -- Part 3. Implications. Chapter 11. Old problems -- Chapter 12. New problems -- -- Volume 2. Plates, Appendices.


"March 1992". Bibliography: p. 445-473 "Submitted for the degree of Doctor of Philosophy".

Awarding Institution

Macquarie University

Degree Type

Thesis PhD


Thesis (PhD) , Macquarie University, School of Earth Sciences

Department, Centre or School

School of Earth Sciences

Year of Award


Principal Supervisor

T. R. Paton


Copyright disclaimer: Copyright Diane Hart 1992 This thesis was digitised for the purposes of Document Delivery. Macquarie University ResearchOnline attempted to locate the author but where this has not been possible; we are making available, open access, selected parts of the thesis which may be used for the purposes of private research and study. If you have any enquiries or issues regarding this work being made available please contact Macquarie University ResearchOnline - If you wish to access the complete thesis, on receipt of a Document Supply Request, placed with Macquarie University Library by another library, we will consider supplying a copy of this thesis. For more information on Document Supply, please contact






1 online resource (2 v. (473 p.), 46 col. plates) ill

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mq:20656 1702699

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