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Origin of the Pacific Jurassic quiet zone

Maurice A. Tivey, William W. Sager, Sang-Mook Lee and Masako Tominaga
Origin of the Pacific Jurassic quiet zone
Geology (Boulder) (September 2006) 34 (9): 789-792


Understanding the marine magnetic anomaly record is critical for constructing realistic geodynamo models of global geomagnetic field, polarity reversal mechanisms, and long-term geomagnetic field behavior. One of the least understood portions of the marine magnetic anomaly record is also the oldest part of the record, the Jurassic quiet zone (JQZ), where anomalies become weak and difficult to correlate. The reason for the existence of the JQZ is unclear. It has been suggested that the JQZ is a true polarity superchron, similar to the Cretaceous normal superchron. Continental magnetostratigraphic studies have suggested that the JQZ is a period of rapid polarity reversal, of low field intensity, or both. We show results of a deep-tow survey of Pacific Jurassic crust that confirms the existence of magnetic anomalies within the JQZ. We tie Ocean Drilling Program Hole 801C (167.4 Ma) into the record and show that seafloor-spreading magnetic anomalies are present around the hole and extend to 170 Ma crust. We find a rise in reversal rate with increasing age with reversal rates over 10 rev/m.y. at 160 Ma and at 167 Ma. Anomaly amplitudes decrease in the record from 155 Ma until 162 Ma, where low-amplitude anomalies are difficult to correlate. Prior to 167 Ma, anomalies regain amplitude and remain strong until the end of our record at 170 Ma. The JQZ thus appears to be a combination of low-amplitude magnetic anomalies combined with rapid field fluctuations, which could be due to either intensity or polarity changes.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 34
Serial Issue: 9
Title: Origin of the Pacific Jurassic quiet zone
Affiliation: Woods Hole Oceanographic Institution, Department of Geology and Geophysics, Woods Hole, MA, United States
Pages: 789-792
Published: 200609
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 24
Accession Number: 2006-071533
Categories: Applied geophysicsSolid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2006163
Illustration Description: illus. incl. sketch map
N17°00'00" - N24°00'00", E150°00'00" - E158°00'00"
N18°38'31" - N18°38'35", E156°21'34" - E156°21'36"
Secondary Affiliation: Texas A&M University, USA, United StatesSeoul National University, KOR, South Korea
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200641
Program Name: ODPOcean Drilling Program
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