Browsing Geosciences Faculty Publications by Issue Date
Now showing items 1-20 of 28
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Behavior of oceanic crustal magnetization at high temperatures: Viscous magnetization and the marine magnetic anomaly source layer
(1999-08-01)Although the source layer for marine magnetic anomalies has been assumed to be the extrusive basalts of uppermost ocean crust, recent studies indicate that lower crustal rocks may also contribute. Because the temperature ... -
Source of tiny wiggles in Chron C5: A comparison of sedimentary relative intensity and marine magnetic anomalies
(2003-06-14)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 ... -
Cooling rate effects on paleointensity estimates in submarine basaltic glass and implications for dating young flows
(2005-07-12)Cooling rate effects on the intensity of thermoremanent magnetization (TRM) have been well documented in ceramics. In that case, laboratory cooling is generally more rapid than the initial cooling, leading to an overestimate ... -
Paleointensity applications to timing and extent of eruptive activity, 9°–10°N East Pacific Rise
(2006-06-08)Placing accurate age constraints on near-axis lava flows has become increasingly important given the structural and volcanic complexity of the neovolcanic zone at fast spreading ridges. Geomagnetic paleointensity of submarine ... -
On the duration of magnetochrons C24r and C25n and the timing of early Eocene global warming events: Implications from the Ocean Drilling Program Leg 208 Walvis Ridge depth transect
(2007-01-01)Five sections drilled in multiple holes over a depth transect of more than 2200 m at the Walvis Ridge (SE Atlantic) during Ocean Drilling Program (ODP) Leg 208 resulted in the first complete early Paleogene deep-sea record. ... -
Magnetic and petrologic characterization of synthetic Martian basalts and implications for the surface magnetization of Mars
(2009-01-01)A suite of synthetic Martian basalts is generated with the objective of providing fundamental material properties data for use in modeling and interpretation of mission data. We systematically evaluate the effects of major ... -
Paleointensity estimates from ignimbrites: An evaluation of the Bishop Tuff
(2010-03-16)Ash flow tuffs, or ignimbrites, typically contain fine-grained magnetite, spanning the superparamagnetic to single-domain size range that should be suitable for estimating geomagnetic field intensity. However, ignimbrites ... -
Deconvolution of u channel magnetometer data: Experimental study of accuracy, resolution, and stability of different inversion methods
(2010-07-14)We explore the effects of sampling density, signal/noise ratios, and position-dependent measurement errors on deconvolution calculations for u channel magnetometer data, using a combination of experimental and numerical ... -
Effects of open and closed system oxidation on texture and magnetic response of remelted basaltic glass
(2010-10-13)As part of an experimental and observational study of the magnetic response of submarine basaltic glass (SBG), we have examined, using ion backscattering spectrometry (RBS), transmission and scanning electron microscopy, ... -
Timing of magnetite formation in basaltic glass: Insights from synthetic analogs and relevance for geomagnetic paleointensity analyses
(2011-02-09)Absolute paleointensity estimates from submarine basaltic glass (SBG) typically are of high technical quality and accurately reflect the ambient field when known. SBG contains fine-grained, low-Ti magnetite, in contrast ... -
Multicomponent cubic oxide exsolution in synthetic basalts: Temperature dependence and implications for magnetic properties
(2012-01-01)Although the compositional unmixing of cubic-structured iron oxides has profound effects on the magnetic properties of rocks that contain them, a basic understanding of the kinetics and thermodynamics of this process has ... -
Eruptive timing and 200 year episodicity at 92°W on the hot spot-influenced Galapagos Spreading Center derived from geomagnetic paleointensity
(2014-01-01)Eruptive timing in mid-ocean ridge systems is relatively poorly constrained, despite being an important variable in our understanding of many mid-ocean ridge processes, including volcanic construction; magma recharge, flux, ... -
Curie temperatures of titanomagnetite in ignimbrites: Effects of emplacement temperatures, cooling rates, exsolution, and cation ordering
(2014-11-06)Pumices, ashes, and tuffs from Mt. St. Helens and from Novarupta contain two principal forms of titanomagnetite: homogeneous grains with Curie temperatures in the range 350–500°C and oxyexsolved grains with similar bulk ... -
Contribution of multidomain titanomagnetite to the intensity and stability of Mars crustal magnetic anomalies
(2014-11-26)Two basalts with compositions relevant to the crusts of Mars and Earth were synthesized at igneous temperatures and held at 650°C for 21 to 257 days under quartz-fayalite-magnetite ƒO2 buffer conditions. The run products ... -
Full vector low-temperature magnetic measurements of geologic materials
(2015-01-14)The magnetic properties of geologic materials offer insights into an enormous range of important geophysical phenomena ranging from inner core dynamics to paleoclimate. Often it is the low-temperature behavior ( -
Geomagnetic paleointensity in historical pyroclastic density currents: Testing the effects of emplacement temperature and postemplacement alteration
(2015-10-26)Thellier-type paleointensity experiments were conducted on welded ash matrix or pumice from the 1912 Novarupta (NV) and 1980 Mt. St. Helens (MSH) pyroclastic density currents (PDCs) with the intention of evaluating their ... -
Effects of titanomagnetite reordering processes on thermal demagnetization and paleointensity experiments
(2016-12-17)Titanomagnetite (Fe3-xTixO4, 0≤x≤1) is a common, naturally occurring magnetic mineral critical to many paleomagnetic studies. Underlying most interpretations is the assumption that, lacking chemical alteration, Curie ... -
Malleable Curie Temperatures of Natural Titanomagnetites: Occurrences, Modes, and Mechanisms
(2018-01-24)Abstract Intermediate-composition titanomagnetites have Curie temperatures (Tc) that depend not only on composition but also on thermal history, with increases of 100°C or more in Tc produced by moderate-temperature ... -
Geology of the Alarcon Rise, Southern Gulf of California
(2018-03-15)Abstract Meter-scale AUV bathymetric mapping and ROV sampling of the entire 47 km-long Alarcon Rise between the Pescadero and Tamayo transforms show that the shallowest inflated portion of the segment hosts all four active ... -
Assessing New and Old Methods in Paleomagnetic Paleothermometry: A Test Case at Mt. St. Helens, USA
(2018-06-07)Paleomagnetic data can be used to estimate deposit temperatures (Tdep) of pyroclastic density currents (PDCs) by finding the laboratory temperature at which a PDC-associated thermal remanence is removed. Paleomagnetic ...