Award Abstract # 1014506
Quaternary magnetic records from North Atlantic sediments: geomagnetism, environmental magnetism, and stratigraphy

NSF Org: EAR
Division Of Earth Sciences
Recipient: UNIVERSITY OF FLORIDA
Initial Amendment Date: July 26, 2010
Latest Amendment Date: June 5, 2014
Award Number: 1014506
Award Instrument: Standard Grant
Program Manager: Stephen Harlan
EAR
 Division Of Earth Sciences
GEO
 Directorate for Geosciences
Start Date: August 1, 2010
End Date: July 31, 2015 (Estimated)
Total Intended Award Amount: $196,219.00
Total Awarded Amount to Date: $196,219.00
Funds Obligated to Date: FY 2010 = $196,219.00
History of Investigator:
  • James Channell (Principal Investigator)
    jetc@ufl.edu
Recipient Sponsored Research Office: University of Florida
1523 UNION RD RM 207
GAINESVILLE
FL  US  32611-1941
(352)392-3516
Sponsor Congressional District: 03
Primary Place of Performance: University of Florida
1523 UNION RD RM 207
GAINESVILLE
FL  US  32611-1941
Primary Place of Performance
Congressional District:
03
Unique Entity Identifier (UEI): NNFQH1JAPEP3
Parent UEI:
NSF Program(s): Geophysics
Primary Program Source: 01001011DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s):
Program Element Code(s): 157400
Award Agency Code: 4900
Fund Agency Code: 4900
Assistance Listing Number(s): 47.050

ABSTRACT

Sediment "drifts" from the deep ocean (where sediments accumulated at elevated rates) are important archives of climate change and of geomagnetic field behavior on centennial and millennial time scales. Secular variation, magnetic excursions, polarity transitions and relative paleointensity (RPI) have been recorded with high-fidelity in North Atlantic sediments drifts, and sediment drift sequences recovered during Integrated Ocean Drilling Program (IODP) Expedition 303/306 offer new opportunities. Magnetic excursions have duration too brief to be recorded by deep-sea sediments with typical (lower) sedimentation rates. The better quality records that are time-calibrated indicate that magnetic excursions are paired polarity reversals in which the reversed polarity state is maintained for only about 1-3 kyr, or less. Similarly, the structure of long-lived polarity transitions can only be resolved at elevated sedimentation rates. We are investigating the combined use of oxygen isotopes (ostensibly a signature for global ice volume) and RPI (ostensibly a global signal of Earth's magnetic field strength) as means of improving global correlations. This exercise will test the usefulness of RPI for global correlation, and will provide estimates of excursion duration, rates of change at polarity transitions, and provide a time-calibrated template of RPI.

Orbital periods (at ~100 and ~41 kyr) are embedded in many RPI records and there is continuing debate regarding the origin of this orbital power; it may represent lithologic contamination of the RPI records or an inherent characteristic of the geomagnetic field. We plan to build on our understanding of the origin of the orbital power by development of "depth-derived" age models for isotope and RPI events (e.g. Terminations, RPI minima etc.) by using compaction-compensated sedimentation models between geomagnetic reversals, and also between reversals and excursions.

This work has implications for both stratigraphy and geophysics. Magnetic stratigraphy within polarity chrons, using RPI and magnetic excursions, appears to provide a much-needed means of global correlation for paleoclimate and other studies that involve synchronizing sedimentary records. The resolved time frames can be applied to records of field behavior to infer rates of change and field geometries that constrain numerical simulations of the geodynamo, and hence constrain mechanisms that govern the generation of the Earth's magnetic field. In addition to the scientific goals of the project, the research is supporting the training of a postdoctoral researcher and graduate and undergraduate students, and is contributing to support of research infrastructure at the University of Florida.

PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH

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(Showing: 1 - 10 of 29)
A. Mazaud, J.E.T. Channell and J.S. Stoner "Relative paleointensity and environmental magnetism since 1.2 Ma at IODP Site U1305 (Eirik Drift, NW Atlantic)" Earth and Planetary Science Letters , v.357-358 , 2012 , p.137
A. Mazaud, J.E.T. Channell and J.S. Stoner "Relative paleointensity and environmental magnetism since 1.2 Ma at IODP Site U1305 (Eirik Drift, NW Atlantic)" Earth and Planetary Science Letters , v.357-358 , 2012 , p.137-144
A. Mazaud, J.E.T. Channell and J.S. Stoner "The paleomagnetic record at IODP Site U1307 back to 2.2 Ma (Eirik Drift, off South Greenland)" Earth Planetary Science Letters , v.429 , 2015 , p.82
A. Mazaud, J.E.T. Channell and J.S. Stoner. "Relative paleointensity and environmental magnetism since 1.2 Ma at IODP Site U1305 (Eirik Drift, NW Atlantic)." Earth and Planetary Science Letters , v.357-358 , 2012 , p.137
D.A. Hodell, S. Crowhurst, L. Skinner, P. C. Tzedakis, V. Margari, J.ET. Channell, G. Kamenov, S. Maclachlan and G. Rothwell "Response of Iberian Margin sediments to orbital and suborbital forcing for the past 420 ka" Paleoceanography , v.28 , 2013 , p.185 10.1002/paleo.20017
D.A. Hodell, S. Crowhurst, L. Skinner, P. C. Tzedakis, V. Margari, J.ET. Channell, G. Kamenov, S. Maclachlan and G. Rothwell "Response of Iberian Margin sediments to orbital and suborbital forcing for the past 420 ka" Paleoceanography , v.28 , 2013 , p.185-199 doi:10.1002/paleo.20017
J.A.L. Nicholl, D. A. Hodell, B. D. A. Naafs, C. Hillaire-Marcel, J.E.T. Channell and O. E. Romero "A Laurentide outburst flooding event during the last interglacial Period" Nature Geoscience , v.10 , 2012 , p.1-4 doi:10.1038/NGEO1622
J.A.L. Nicholl, D. A. Hodell, B. D. A. Naafs, C. Hillaire-Marcel, J.E.T. Channell and O. E. Romero "A Laurentide outburst flooding event during the last interglacial Period" Nature Geoscience , 2012 10.1038/NGEO1622
J.A.L. Nicholl, D. A. Hodell, B. D. A. Naafs, C. Hillaire-Marcel, J.E.T. Channell and O. E. Romero. "A Laurentide outburst flooding event during the last interglacial Period" Nature Geoscience , 2012 , p.10.1038/N
J.E.T. Channell "The Iceland Basin excursion: Age, duration, and excursion field geometry" Geochem. Geophys. Geosyst , v.15 , 2014 10.1002/2014GC005564
J.E.T. Channell and D.A. Hodell "Magnetic signatures of Heinrich-like detrital layers in the Quaternary of the North Atlantic" Earth Planetary Science Letters , v.369-370 , 2013 , p.260
(Showing: 1 - 10 of 29)

PROJECT OUTCOMES REPORT

Disclaimer

This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

Deep-sea sediments constitute the principal archive of information on past climate, and interpretation of the archive requires that we have the means to correlate records from one location to another across the world’s oceans. For the last few million years, the traditional method of stratigraphic (geological) correlation in marine sediments involves the oxygen isotopic composition of foraminiferal (microscopic sea-shell) carbonate. This isotopic signal in the oceans varies in response to the amount of ice stored as glaciers on continents, because evaporation of seawater and storage of snow/ice modifies the isotopic composition of seawater and of foraminiferal carbonate at the time of shell growth. The oxygen isotope signal is/was thought to be a global signal and therefore useful for global correlation of climate records. However, in recent years, it has become increasingly clear that the oxygen isotope signal is perturbed by water chemistry and temperature and varies over long distances (e.g. from the Atlantic to the Pacific). This research project has focused on the use of records of the Earth’s magnetic field in geological (stratigraphic) correlation of marine sediments. Can magnetic field records that are acquired at the time of sediment deposition be used to improve the resolution of global correlation, to augment, or eventually replace oxygen isotope data?  The elements of the Earth’s magnetic field that can be used in global correlation are: (1) polarity reversal of the Earth’s magnetic field. These have been used in stratigraphic correlation for decades but are only useful for precise correlation in the immediate vicinity of polarity reversals that may be separated by tens or hundreds of thousands of years. (2) Magnetic excursions are brief (less than a few kyrs) directional aberrations of the Earth’s magnetic field that are believed to be manifest globally and occur irregularly during times of uniform polarity. (3) The intensity of the Earth’s magnetic field that represents a global signal when recorded in sediments with sedimentation rates less than ~50 cm/kyr. This research project has focused on these three elements of the Earth’s magnetic field and their integration with oxygen isotope records.  We have developed relative paleointensity (RPI) proxies that monitor past changes in the strength of the magnetic field. We have studied oxygen isotope records and RPI records (together with polarity reversals and magnetic excursions) from North Atlantic deep-sea drilling sites in order to test and improve the resolution of stratigraphic correlation over the last few million years.  We have shown that magnetic field records can augment oxygen isotope data and improve the resolution of stratigraphic correlation. This effort will aid the correlation of environmental and climate records across the globe, and help to interpret these environmental records in terms of climate change during the past few million years.  In addition, refined knowledge of the behavior of the Earth’s magnetic field, over the last few million years, constrain numerical simulations of the geodynamo and hence constrain mechanisms responsible for the behavior of the Earth’s magnetic field.

 


Last Modified: 09/01/2015
Modified by: James E Channell

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