Revised Pacific M-anomaly geomagnetic polarity timescale
Sager, William W.
MetadataShow full item record
KeywordMagnetic anomalies: modelling and interpretation; Reversals: process, time scale, magnetostratigraphy; Marine magnetics and palaeomagnetics
The current M-anomaly geomagnetic polarity timescale (GPTS) is mainly based on the Hawaiian magnetic lineations in the Pacific Ocean. M-anomaly GPTS studies to date have relied on a small number of magnetic profiles, a situation that is not ideal because any one profile contains an uncertain amount of geologic 'noise' that perturbs the magnetic field signal. Compiling a polarity sequence from a larger array of magnetic profiles is desirable to provide greater consistency and repeatability. We present a new compilation of the M-anomaly GPTS constructed from polarity models derived from magnetic profiles crossing the three lineation sets (Hawaiian, Japanese and Phoenix) in the western Pacific. Polarity reversal boundary locations were estimated with a combination of inverse and forward modelling of the magnetic profiles. Separate GPTS were established for each of the three Pacific lineation sets, to allow examination of variability among the different lineation sets, and these were also combined to give a composite timescale. Owing to a paucity of reliable direct dates of the M-anomalies on ocean crust, the composite model was time calibrated with only two ages; one at each end of the sequence. These two dates are 125.0 Ma for the base of M0r and 155.7 Ma for the base of M26r. Relative polarity block widths from the three lineation sets are similar, indicating a consistent Pacific-wide spreading regime. The new GPTS model shows slightly different spacings of polarity blocks, as compared with previous GPTS, with less variation in block width. It appears that the greater polarity chron irregularity in older models is mostly an artifact of modelling a small number of magnetic profiles. The greater averaging of polarity chron boundaries in our model gives a GPTS that is statistically more robust than prior GPTS models and a superior foundation for Late Jurassic–Early Cretaceous geomagnetic and chronologic studies.
Author Posting. © The Authors, 2010. This article is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 182 (2010): 203-232, doi:10.1111/j.1365-246X.2010.04619.x.
Showing items related by title, author, creator and subject.
Central Anomaly Magnetization High documentation of crustal accretion along the East Pacific Rise (9°55′–9°25′N) Williams, Clare M.; Tivey, Maurice A.; Schouten, Hans A.; Fornari, Daniel J. (American Geophysical Union, 2008-04-09)Near-bottom magnetic data collected along the crest of the East Pacific Rise between 9°55′ and 9°25′N identify the Central Anomaly Magnetization High (CAMH), a geomagnetic anomaly modulated by crustal accretionary processes ...
Deep-tow magnetic anomaly study of the Pacific Jurassic Quiet Zone and implications for the geomagnetic polarity reversal timescale and geomagnetic field behavior Tominaga, Masako; Sager, William W.; Tivey, Maurice A.; Lee, Sang-Mook (American Geophysical Union, 2008-07-26)The Jurassic Quiet Zone (JQZ) is a region of low-amplitude magnetic anomalies whose distinctive character may be related to geomagnetic field behavior. We collected deep-tow magnetic profiles in Pigafetta Basin (western ...
Tominaga, Masako; Sager, William W. (American Geophysical Union, 2010-01-06)Late Jurassic-Early Cretaceous marine magnetic anomalies observed in the North Atlantic exhibit an abrupt change in character in M5-M15 crust. The anomalies are smoother with low amplitudes, and are difficult to correlate ...