Universität zu Köln

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:	Creators Email ORCID ORCID Put Code Allstaedt, Frederik J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Appel, Erwin UNSPECIFIED UNSPECIFIED UNSPECIFIED Roesler, Wolfgang UNSPECIFIED UNSPECIFIED UNSPECIFIED Prokopenko, Alexander A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Neumann, Udo UNSPECIFIED UNSPECIFIED UNSPECIFIED Wenzel, Thomas UNSPECIFIED UNSPECIFIED UNSPECIFIED Pross, Joerg UNSPECIFIED UNSPECIFIED UNSPECIFIED
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:	Keywords Language SNAKE RIVER PLAIN; SCIENTIFIC DRILLING PROJECT; MAGNETIC SELF-REVERSAL; YELLOWSTONE HOTSPOT; MARINE-SEDIMENTS; LOW-TEMPERATURE; ROCKS; BASIN; TITANOMAGNETITE; STRATIGRAPHY Multiple languages Geochemistry & Geophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/32448