Publications

Export 4 results:
Sort by: Author Title Type [ Year  (Desc)]
2003
Bowles, J, Tauxe L, Gee J, McMillan D, Cande S.  2003.  Source of tiny wiggles in Chron C5: A comparison of sedimentary relative intensity and marine magnetic anomalies. Geochemistry Geophysics Geosystems. 4   10.1029/2002gc000489   AbstractWebsite

[1] In addition to the well-established pattern of polarity reversals, short-wavelength fluctuations are often present in both sea-surface data ("tiny wiggles'') and near-bottom anomaly data. While a high degree of correlation between different geographical regions suggests a geomagnetic origin for some of these wiggles, anomaly data alone cannot uniquely determine whether they represent short reversals or paleointensity variations. Independent evidence from another geomagnetic recording medium such as deep-sea sediments is required to determine the true nature of the tiny wiggles. We present such independent evidence in the form of sedimentary relative paleointensity from Chron C5. We make the first comparison between a sedimentary relative paleointensity record (ODP Site 887 at 54degreesN, 148degreesW) and deep-tow marine magnetic anomaly data (43degreesN, 131degreesW) [ Bowers et al., 2001] for Chron C5. The sediment cores are densely sampled at similar to2.5 kyr resolution. The inclination record shows no evidence for reverse intervals within the similar to1 myr-long normal Chron C5n.2n. Rock magnetic measurements suggest that the primary magnetic carrier is pseudo-single domain magnetite. We choose a partial anhysteretic magnetization (pARM) as our preferred normalizer, and the resulting relative paleointensity record is used as input to a forward model of crustal magnetization. We then compare the results of this model with the stacked deep-tow anomaly records. The two records show a significant degree of correlation, suggesting that the tiny wiggles in the marine magnetic anomalies are likely produced by paleointensity variations. An analysis of our sampling density suggests that if any reverse intervals exist at this site, they are likely to be <5 kyr in duration. Furthermore, we suggest that reverse intervals during Chron C5n.2n documented in other locations are unlikely to be global.

2001
Bowers, NE, Cande SC, Gee JS, Hildebrand JA, Parker RL.  2001.  Fluctuations of the paleomagnetic field during chron C5 as recorded in near-bottom marine magnetic anomaly data. Journal of Geophysical Research-Solid Earth. 106:26379-26396.   10.1029/2001jb000278   AbstractWebsite

Near-bottom magnetic data contain information on paleomagnetic field fluctuations during chron C5 as observed in both the North and South Pacific. The North Pacific data include 12 survey lines collected with a spatial separation of up to 120 kin, and the South Pacific data consist of a single long line collected on the west flank of the East Pacific Rise (EPR) at 19 degreesS. The North Pacific magnetic profiles reveal a pattern of linear, short-wavelength (2 to 5 km) anomalies (tiny wiggles) that are highly correlated over the shortest (3.8 km) to longest (120 km) separations in the survey. Magnetic inversions incorporating basement topography show that these anomalies are not caused by the small topographic relief. The character of the near-bottom magnetic profile from anomaly 5 on the west flank of the EPR, formed at a spreading rate more than twice that of the North Pacific, displays a remark-able similarity to the individual and stacked lines from the North Pacific survey area, Over distances corresponding to 1 m.y., 19 lows in the magnetic anomaly profile can be correlated between the North and South Pacific lines. Modeling the lows as due to short polarity events suggests that they may be caused by rapid swings of the magnetic field between normal and reversed polarities with little or no time in the reversed state. Owing to the implausibly high number of reversals required to account for these anomalies and the lack of any time in the reversed state, we conclude that the near-bottom signal is primarily a record of pateointensity fluctuations during chron C5. Spectral analysis of the North Pacific near bottom lines shows that the signal is equivalent to a paleointensity curve with a temporal resolution of 40 to 60 kyr, while measurements of the smallest separations of correlatable dips in the field suggest a temporal resolution of 36 kyr.

1999
Herbert, TD, Gee J, DiDonna S.  1999.  Precessional cycles in Upper Cretaceous pelagic sediments of the South Atlantic; long-term patterns from high-frequency climate variations. Special Paper Geological Society of America. 332:105-120. Abstract
n/a
1991
Pospichal, JJ, Dehn J, Driscoll N, van Eijden AJM, Farrell J, Fourtanier E, Gamson PD, Gee J, Janecek T, Jenkins GD, Klootwijk CT, Nomura R, Owen RM, Rea DK, Resiwati P, Smit J, Smith GM.  1991.  Cretaceous-Paleogene biomagnetostratigraphy of sites 752-755, Broken Ridge; a synthesis. Proceedings of the Ocean Drilling Program, Scientific Results. 121:721-742.   10.2973/odp.proc.sr.121.181.1991   Abstract

Broken Ridge, in the eastern Indian Ocean, is a shallow-water volcanic platform which formed during the Early to middle Cretaceous at which time it comprised the northern portion of the Kerguelen-Heard Plateau. Rifting during the middle Eocene and subsequent seafloor spreading has moved Broken Ridge about 20°N to its present location. The sedimentary section of Broken Ridge includes Turonian-lower Eocene limestone and chalk with volcanic ash, an interval of detrital sands and gravels associated with middle Eocene rifting and uplift, and a middle-late Oligocene unconformity overlain by a thin section of Neogene-Holocene pelagic calcareous ooze. This paper summarizes the available post-cruise biostratigraphic and magnetostratigraphic data for the Cretaceous- Paleogene section on Broken Ridge. The synthesis of this information permits a more precise interpretation of the timing of events in the history of Broken Ridge, in particular the timing and duration of the middle Eocene rifting event. Paleontologic data support rapid flexural uplift of Broken Ridge in response to mechanical rather than thermal forces. Other highlights of the section include a complete Cretaceous/Tertiary boundary and an opportunity for first-order correlation of Paleogene diatom stratigraphy with that of the calcareous groups.