THE USE OF THE GEOMAGNETIC POLARITY TIME SCALE IN ELUCIDATING PLEISTOCENE LANDSCAPE EVOLUTION: AN EXAMPLE FROM SOUTH AUSTRALIA

• Published in: South African geographical journal Vol. 79; no. 2; pp. 75 - 82
• Main Authors: BOURMAN, R. P., PILLANS, B.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis Group 01-09-1997; Routledge; South African geographical society
• Subjects: Australia; Bgi / Prodig; Climate; Evolution; Geography; Landscape; Oceania; Physical geography; Pleistocene; Australia; South Australia; Geochronology; Geomorphogenesis; Palaeogeography; Quaternary; Fault; Palaeomagnetism; Pleistocene
• ISSN: 0373-6245; 2151-2418
• DOI: 10.1080/03736245.1997.9713627

The application of the geomagnetic polarity time scale to terrestrial Pleistocene sediments in the Adelaide area of South Australia has elucidated landscape evolution. Identification of the Bruhnes/Matuyama polarity transition (0.78 Ma) and the Jaramillo Normal Subchron(0.99 Ma at its top) has allowed numerical ages to be assigned to previously undated weathering products. This study demonstrates that palaeomagnetism is a valuable tool both for correlating and for distinguishing superficially similar materials over distances exceeding 100 km. The palaeomagnetically determined ages reveal the need for reinterpretation of previously published marine-terrestrial relationships and provide data relevant to the time taken for development of a strongly mottled ferruginous zone and the mode of origin of the mottles: the mottles appear to have formed by the localised redistribution of iron minerals within the sediments. The view that weathering was ongoing throughout the Pleistocene is suggested by the occurrence of mottles and/or palaeosols in all of the Pleistocene terrestrial units as well as normal polarity weathering signatures overprinting reversed chemical remanent magnetism. The palaeomagnetic data has also more precisely fixed the timing of compressionally-induced reverse faulting.