Environmental control of magnetic properties of upper-slope sediments near the Great Barrier Reef

results from Leg 133, Site 820

C. E. Barton, M. Lackie, F. M. Peerdeman

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contribution

5 Citations (Scopus)

Abstract

Paleomagnetic analysis of sediment samples from Ocean Drilling Program (ODP) Leg 133, Site 820, 10 km from the outer edge of the Great Barrier Reef, is undertaken to investigate the mineral magnetic response to environmental (sea level) changes. The magnetic susceptibility (K) record is central for describing and understanding the magnetic properties of the sediments, and their relationship to glacio-eustatic fluctuations in sea level. Three prominent magnetic susceptibility peaks, at about 7, 32 and 64 mbsf, are superimposed on a background of smaller susceptibility oscillations. Fluctuations in susceptibility and remanence in the "background' zone are controlled predominantly by variations in the concentration, rather than the composition of ferrimagnetics, with carbonate dilution playing an important role (type-A properties). The sharp susceptibility maxima occur at the start of the marine transgressions following low stands in sea level (high δ18O, glacial maxima); and are characterized by a stable single-domain remanence, with a significant contribution from ulta-fine, superparamagnetic grains (type-C properties). During the later marine transgression, the susceptibility gradually returns to low values and the remanence is carried by stable single-domain magnetite (type-B properties). The A, B, and C types of sediment have distinctive ARM/K ratios. Throughout most of the sequence a strong inverse correlation exists between magnetic susceptibility and both CaCO3 and δ18O variations. The main magnetic characteristics of the sediments are thought to reflect sea-level-controlled variations in the sediment source regions and related run-off conditions. Some preliminary evidence is seen that biogenic magnetite may play a significant role in the magnetization of these sediments. -from Authors

Original languageEnglish
Title of host publicationProceedings of the Ocean Drilling Program, Scientific Results
EditorsJ.A. McKenzie, PJ. Davies, A. Palmer-Julson
PublisherODP, Texas A&M University, College Station
Pages543-562
Number of pages20
Volume133
Publication statusPublished - 1993

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    Barton, C. E., Lackie, M., & Peerdeman, F. M. (1993). Environmental control of magnetic properties of upper-slope sediments near the Great Barrier Reef: results from Leg 133, Site 820. In J. A. McKenzie, PJ. Davies, & A. Palmer-Julson (Eds.), Proceedings of the Ocean Drilling Program, Scientific Results (Vol. 133, pp. 543-562). ODP, Texas A&M University, College Station.