Allstaedt, Frederik J., Appel, Erwin, Roesler, Wolfgang, Prokopenko, Alexander A., Neumann, Udo, Wenzel, Thomas and Pross, Joerg (2020). Downward remagnetization of a similar to 74-m-thick zone in lake sediments from palaeo-Lake Idaho (NW United States)-Locating the Gauss/Matuyama geomagnetic boundary within a dual-polarity zone. Geophys. J. Int., 222 (2). S. 754 - 769. OXFORD: OXFORD UNIV PRESS. ISSN 1365-246X

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Abstract

Remagnetization is an important issue in palaeomagnetism. Here, we discuss an extraordinarily thick (similar to 74 m) dual-polarity transition zone between the Gauss and Matuyama Chrons. The studied succession is from a drill core through lacustrine sediments of palaeo-Lake Idaho (Snake River Plain, NW United States of America) that are intercalated with basalt units. We identified detrital Ti-rich titanomagnetite and magnetite in lamellar exsolutions as the main carriers of a primary remanence, likely derived from the basalts that erupted in the Snake River Plain. Stepwise thermal demagnetization revealed a single-component remanent magnetization with reversed and normal polarities above and below the transition zone, respectively. Based on rock-magnetic results, microscopic observations, and previously known events in the evolution of palaeo-Lake Idaho, the reversed-polarity component in the transition zone represents a secondary chemical remanent magnetization caused by magnetic mineral alteration or partial neo-formation of magnetite, in association with strong depletion of the primary detrital magnetic minerals that affected a wide depth range below the level where the remagnetization event occurred. This remagnetization event was most likely related to lake-level lowering and partial desiccation of palaeo-Lake Idaho. Understanding the nature and origin of the remagnetization allows to identify the polarity boundary in the unusual case of a secondary magnetization with reversed polarity produced downward in a sequence to an extraordinary large depth. Based on available age information, the observed reversal represents the Gauss/Matuyama boundary, which provides an important age constraint for palaeoclimatic interpretation of the succession.

Item Type: Journal Article
Creators:
CreatorsEmailORCIDORCID Put Code
Allstaedt, Frederik J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Appel, ErwinUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Roesler, WolfgangUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Prokopenko, Alexander A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Neumann, UdoUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Wenzel, ThomasUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Pross, JoergUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
URN: urn:nbn:de:hbz:38-324485
DOI: 10.1093/gji/ggaa165
Journal or Publication Title: Geophys. J. Int.
Volume: 222
Number: 2
Page Range: S. 754 - 769
Date: 2020
Publisher: OXFORD UNIV PRESS
Place of Publication: OXFORD
ISSN: 1365-246X
Language: English
Faculty: Unspecified
Divisions: Unspecified
Subjects: no entry
Uncontrolled Keywords:
KeywordsLanguage
SNAKE RIVER PLAIN; SCIENTIFIC DRILLING PROJECT; MAGNETIC SELF-REVERSAL; YELLOWSTONE HOTSPOT; MARINE-SEDIMENTS; LOW-TEMPERATURE; ROCKS; BASIN; TITANOMAGNETITE; STRATIGRAPHYMultiple languages
Geochemistry & GeophysicsMultiple languages
URI: http://kups.ub.uni-koeln.de/id/eprint/32448

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