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Tectonic and geochronological implications of variably timed magnetizations carried by authigenic greigite in marine sediments from New Zealand

Tectonic and geochronological implications of variably timed magnetizations carried by authigenic greigite in marine sediments from New Zealand
Tectonic and geochronological implications of variably timed magnetizations carried by authigenic greigite in marine sediments from New Zealand
Detailed scanning electron microscope observations, coupled with elemental microanalysis, confirm the presence of a chemical remanent magnetization carried by authigenic greigite (Fe3S4) in uplifted Neogene marine sediments from the Hikurangi Margin of New Zealand. Normal polarity samples from the studied section have declinations that are deflected 60° clockwise of reversed polarity samples, indicating the presence of two distinct magnetizations separated by several million years of tectonic rotation about a vertical axis. However, although multiple generations of iron sulfide growth are observed petrographically, we see no clear differences in the relative timing of greigite formation between samples carrying these two magnetizations. Not only can the diagenetic growth of greigite in fine-grained marine sediments occur long after deposition, obscuring tectonic and magnetostratigraphic information, but such remagnetizations are also difficult to distinguish from a more primary signal in the absence of constraints from field tests. Our observations emphasize that considerable care is necessary when interpreting paleomagnetic data from greigite-bearing sediments.
greigite, remagnetization, new zealand, tectonics, magnetostratigraphy
0091-7613
553-556
Rowan, C.J.
5d88ac64-c1d9-47c5-ba0a-ccf43eccc673
Roberts, A.P.
4497b436-ef02-428d-a46e-65a22094ba52
Rowan, C.J.
5d88ac64-c1d9-47c5-ba0a-ccf43eccc673
Roberts, A.P.
4497b436-ef02-428d-a46e-65a22094ba52

Rowan, C.J. and Roberts, A.P. (2005) Tectonic and geochronological implications of variably timed magnetizations carried by authigenic greigite in marine sediments from New Zealand. Geology, 33 (7), 553-556. (doi:10.1130/G21382.1).

Record type: Article

Abstract

Detailed scanning electron microscope observations, coupled with elemental microanalysis, confirm the presence of a chemical remanent magnetization carried by authigenic greigite (Fe3S4) in uplifted Neogene marine sediments from the Hikurangi Margin of New Zealand. Normal polarity samples from the studied section have declinations that are deflected 60° clockwise of reversed polarity samples, indicating the presence of two distinct magnetizations separated by several million years of tectonic rotation about a vertical axis. However, although multiple generations of iron sulfide growth are observed petrographically, we see no clear differences in the relative timing of greigite formation between samples carrying these two magnetizations. Not only can the diagenetic growth of greigite in fine-grained marine sediments occur long after deposition, obscuring tectonic and magnetostratigraphic information, but such remagnetizations are also difficult to distinguish from a more primary signal in the absence of constraints from field tests. Our observations emphasize that considerable care is necessary when interpreting paleomagnetic data from greigite-bearing sediments.

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Published date: 2005
Keywords: greigite, remagnetization, new zealand, tectonics, magnetostratigraphy

Identifiers

Local EPrints ID: 20422
URI: http://eprints.soton.ac.uk/id/eprint/20422
ISSN: 0091-7613
PURE UUID: bd5879fa-9321-4edc-9a9e-ed980fdf719a

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Date deposited: 24 Feb 2006
Last modified: 15 Mar 2024 06:24

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Contributors

Author: C.J. Rowan
Author: A.P. Roberts

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