Wang, Daming et al. (2005): Why is the remanent magnetic intensity of Cretaceous MORB so much higher than that of mid to late Cenozoic MORB?

Leg/Site/Hole:
Identifier:
2006-011268
georefid

10.1130/GES00024.1
doi

Creator:
Wang, Daming
University of Michigan, Department of Geological Sciences, Ann Arbor, MI, United States
author

Van der Voo, Rob
author

Peacor, Donald R.
author

Identification:
Why is the remanent magnetic intensity of Cretaceous MORB so much higher than that of mid to late Cenozoic MORB?
2005
Geosphere
Geological Society of America, Boulder, CO, United States
1
3
138-146
The fact that the natural remanent magnetization (NRM) intensity of mid-oceanic-ridge basalt (MORB) samples shows systematic variations as a function of age has long been recognized: maximum as well as average intensities are generally high for very young samples, falling off rather rapidly to less than half the recent values in samples between 10 and 30 Ma, whereupon they slowly rise in the early Tertiary and Cretaceous to values that approach those of the very young samples. NRM intensities measured in this study follow the same trends as those observed in previous publications. In this study, we take a statistical approach and examine whether this pattern can be explained by variations in one or more of all previously proposed mechanisms: chemical composition of the magnetic minerals, abundance of these magnetization carriers, vectorial superposition of parallel or antiparallel components of magnetization, magnetic grain or domain size patterns, low-temperature oxidation to titanomaghemite, or geomagnetic field behavior. We find that the samples do not show any compositional, petrological, rock-magnetic, or paleomagnetic patterns that can explain the trends. Geomagnetic field intensity is the only effect that cannot be directly tested on the same samples, but it shows a similar pattern as our measured NRM intensities. We therefore conclude that the geomagnetic field strength was, on-average, significantly greater during the Cretaceous than during the Oligocene and Miocene.
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Solid-earth geophysics; basalts; Cenozoic; cores; Cretaceous; Curie point; Deep Sea Drilling Project; electron probe data; global; grain size; igneous rocks; magnetic field; magnetic intensity; magnetic properties; magnetization; Mesozoic; mid-ocean ridge basalts; middle Cenozoic; natural remanent magnetization; Ocean Drilling Program; oxidation; oxides; paleomagnetism; remanent magnetization; temporal distribution; titanomagnetite; upper Cenozoic; variations; volcanic rocks;

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