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Backman, J, Shackleton NJ, Tauxe L.  1983.  Quantitative Nannofossil Correlation to Open Ocean Deep-Sea Sections from Plio-Pleistocene Boundary at Vrica, Italy. Nature. 304:156-158.   10.1038/304156a0   AbstractWebsite

Although numerous studies have been performed on material from the Vrica section, southern Italy1–3 with a view to establishing its suitability as a type section for the Plio-Pleistocene boundary, these studies have failed either to establish the age of the boundary, or to achieve accurate correlation to other regions. We report here quantitative studies of selected nannofossil species in this section which unambiguously correlate it with open ocean piston cores in which an accurate chronology has been established. The age of the Plio-Pleistocene boundary as proposed by Colalongo et al. 4 is estimated to be ~1.6 Myr.

Badgley, C, Tauxe L, Bookstein FL.  1986.  Estimating the Error of Age Interpolation in Sedimentary-Rocks. Nature. 319:139-141.   10.1038/319139a0   AbstractWebsite

Magnetostratigraphic data can provide information on rates of sediment accumulation within a single sedimentation system over time spans from 10^4 to 10^6 yr. The short-term rate of sediment deposition varies with time; the apparent average rate over any longer interval also depends on the relative durations of periods of deposition, stasis (non-deposition), and erosion. While the average rate can be used to infer the time of occurrence of an event from its stratigraphical position, the inferred age has an uncertainty deriving from the variability in rate of sediment accumulation over all shorter timescales. We analyse here variability in sediment accumulation rates provided by the magnetostratigraphy of Miocene, Siwalik sediments from Pakistan. For long periods (>10^6 yr), sediment accumulation is approximately linear through time. Over short intervals (10^4–10^5yr), however, there is considerable variability. To provide an error term for an absolute age interpolated between boundaries of polarity units, we use a resampling technique similar to the statistician's ‘bootstrapping’. We illustrate this approach by estimating a standard error for the interpolated age of a biostratigraphical datum: the first appearance of hipparionine equids in the Siwalik sequence near the town of Khaur. The first appearance of “Hipparion” in the Khaur sequence is 9.22±0.09 Myr.

Badgley, C, Tauxe L, Bookstein FL.  1986.  Age Interpolation - Reply. Nature. 323:471-472.   10.1038/323471b0   AbstractWebsite
Barton, C, Kono M, Tauxe L, Wei QY.  1997.  Untitled - Preface. Journal of Geomagnetism and Geoelectricity. 49:471-471. AbstractWebsite
Behrensmeyer, AK, Potts R, Plummer T, Tauxe L, Opdyke N, Jorstad T.  1995.  The Pleistocene Locality of Kanjera, Western Kenya - Stratigraphy, Chronology and Paleoenvironments. Journal of Human Evolution. 29:247-274.   10.1006/jhev.1995.1059   AbstractWebsite

Kanjera is well known as the source of controversial hominid fossils collected by L. S. B. Leakey in the 1930s. Since 1935, the context of fossils and artifacts from the locality has been in doubt, due to a claim that sediment slumping had commingled materials from stratigraphic units of different ages. A careful re-examination of the geology demonstrates that the Kanjera deposits consist of approximately 37 m of volcaniclastic, fluvial, mudflat and lacustrine sediments that we assign to three major units: the Kanjera Formation, the Apoko Formation, and the Black Cotton Soil, Outcrops cover approximately 2 km(2) in two adjacent areas, the Northern and Southern Exposures. Fossils and artifacts are found in primary contexts through much of the stratigraphic column; and extensive trenching failed to reveal any sediment slumping that would have disturbed these contexts. Faulting, rapid lateral facies changes, and an erosional unconformity between the Kanjera and Apoko Formations result in complex geological relationships. Magnetostratigraphic and faunal determinations indicate that the Kanjera Formation is approximately 1.5-0.5 Ma, the Apoko Formation younger than 0.5 Ma, and the Black Cotton Soil latest Pleistocene to Holocene. The hominid sample is derived from the Black Cotton Soil except for Leakey's Hominid 3, which probably was an intrusive burial into Kanjera Formation Bed KN-2. The Theropithecus oswaldi type specimen originated from KN-2a and is dated between 1.1 and at most 1.76 Ma. The Kanjera Formation provides the youngest known records of Metridiochoerus andrewsi and Deinotherium bozasi at about 1.0 Ma. (C) 1995 Academic Press Limited

Behrensmeyer, AK, Tauxe L.  1982.  Isochronous Fluvial Systems in Miocene Deposits of Northern Pakistan. Sedimentology. 29:331-352.   10.1111/j.1365-3091.1982.tb01799.x   AbstractWebsite

A Paleomagnetic isochron dated at about 8.1 Myr BP and detailed lithostratigraphy of a 40 m interval exposed along strike for 40 km establish the depositional patterns of two contemporaneous, interfingering fluvial systems in the upper part of the Meddle Siwalik sequence.The two systems, referred to as the buff and blue-grey, differ in unit shape, lithofacies, bedding sequence, palaeocurrent direction and sand composition. Interfingering occurs along the south-west-north-east strike of the outcrops, with the palaeodrainage directions of the two systems generally perpendicular to this line. The axis of the blue-grey system, which deposited widespread sheet sands and silts, lay toward the south west end of the study area. The more complex axis of the buff system, which deposited shoe-string sand bodies and lage volumes of silt and clay, lay toward the north-east. The source area for both systems was the rising Himalyan belt to the north and noth-east of the study area. At maximum extent the blue-grey system occupied a channel belt at least 25 km wide. Channel belt widths and depths for the buff system are 1–3 km and 3–7 m, respectively. Current directions averge 94° for blue-grey sands and 136° for buff sands. Blur-grey sands contain 20% more rock fragments and are otherwise less mature than buff sands.The buff system shows a verticla pattern of avulsion, palaeosol formation and floodplain aggradation which we attribute to autocyclic processes of parallel rivers. The blue-grey system shows phases of erosion accompaniced laterally by plaeosol formation, folowed by valley fill and overfowing of interfluve surfaces. Theis pattern may be caused by allocyclic presses affecting the source area. We interpret the blue-grey system as a major drainage from the interior Himalayas (perhaps the ancestral Indus) and the buff system as a complex of smaller drinages along the mountain front which were probably ributaries to the bluegrey syste.Vertebrate fossils including hominoid primates from the area are almost exclusively associated with lithofacies of the buff system, and this probably refects both taphonomic and palaeoecological differences between the two systems.

Ben-Yosef, E, Ron H, Tauxe L, Agnon A, Genevey A, Levy TE, Avner U, Najjar M.  2008.  Application of copper slag in geomagnetic archaeointensity research. Journal of Geophysical Research-Solid Earth. 113   10.1029/2007jb005235   AbstractWebsite

Paleointensity and archaeointensity studies since the 1950s have produced numerous geomagnetic intensity data for the last seven millennia. As a consequence of different experiments and materials, there is a complex and internally inconsistent picture of the geomagnetic field behavior. In this study we present data using a recently developed experimental design on a heretofore unexploited recording medium: copper slag deposits. Our results, based on hundreds of specimens from various archaeometallurgical sites of the Southern Levant, demonstrate the applicability of copper slag material for archaeointensity studies. In addition to frequently exhibiting good experimental behavior, slag has further advantages such as dense multilayer deposits and in cases embedded charcoals, which open the door to data sets with excellent age control and resolution. The data presented here augment the high quality database from the Middle East and support previously observed periods of rapid change of the intensity of the geomagnetic field.

Ben-Yosef, E, Millman M, Shaar R, Tauxe L, Lipschits O.  2017.  Six centuries of geomagnetic intensity variations recorded by royal Judean stamped jar handles. Proceedings of the National Academy of Sciences.   10.1073/pnas.1615797114   Abstract

Earth’s magnetic field, one of the most enigmatic physical phenomena of the planet, is constantly changing on various time scales, from decades to millennia and longer. The reconstruction of geomagnetic field behavior in periods predating direct observations with modern instrumentation is based on geological and archaeological materials and has the twin challenges of (i) the accuracy of ancient paleomagnetic estimates and (ii) the dating of the archaeological material. Here we address the latter by using a set of storage jar handles (fired clay) stamped by royal seals as part of the ancient administrative system in Judah (Jerusalem and its vicinity). The typology of the stamp impressions, which corresponds to changes in the political entities ruling this area, provides excellent age constraints for the firing event of these artifacts. Together with rigorous paleomagnetic experimental procedures, this study yielded an unparalleled record of the geomagnetic field intensity during the eighth to second centuries BCE. The new record constitutes a substantial advance in our knowledge of past geomagnetic field variations in the southern Levant. Although it demonstrates a relatively stable and gradually declining field during the sixth to second centuries BCE, the new record provides further support for a short interval of extreme high values during the late eighth century BCE. The rate of change during this “geomagnetic spike” [defined as virtual axial dipole moment > 160 ZAm2 (1021 Am2)] is further constrained by the new data, which indicate an extremely rapid weakening of the field (losing ∼27% of its strength over ca. 30 y).

Ben-Yosef, E, Tauxe L, Levy TE, Shaar R, Ron H, Najjar M.  2009.  Geomagnetic intensity spike recorded in high resolution slag deposit in Southern Jordan. Earth and Planetary Science Letters. 287:529-539.   10.1016/j.epsl.2009.09.001   AbstractWebsite

In paleomagnetism, periods of high field intensity have been largely ignored in favor of the more spectacular directional changes associated with low field intensity periods of excursions and reversals. Hence, questions such as how strong the field can get and how fast changes occur are still open. In this paper we report on data obtained from an archaeometallurgical excavation in the Middle East, designed specifically for archaeomagnetic sampling. We measured 342 specimens from 72 samples collected from a 6.1 m mound of well stratified copper production debris at the early Iron Age (12th-9th centuries BCE) site of Khirbat en-Nahas in Southern Jordan. Seventeen samples spanning 200 yr yielded excellent archaeointensity results that demonstrate rapid changes in field intensity in a period of overall high field values. The results display a remarkable spike in field strength, with sample mean values of over 120 mu T (compared to the current field strength of 44 mu T). A suite of 13 radiocarbon dates intimately associated with our samples, tight control of sample location and relative stratigraphy provide tight constraints on the rate and magnitude of changes in archaeomagnetic field intensities. (C) 2009 Elsevier B.V. All rights reserved.

Ben-Yosef, E, Tauxe L, Levy TE.  2010.  Archaeomagnetic Dating of Copper Smelting Site F2 in the Timna Valley (Israel) and Its Implications for the Modelling of Ancient Technological Developments. Archaeometry. 52:1110-1121.   10.1111/j.1475-4754.2010.00528.x   AbstractWebsite

Site F2 in the Timna Valley, Israel, is a small copper smelting site of 'primitive' technology, dated by its excavator to the Pottery Neolithic (sixth to fifth millennium bce). This early date challenges the common view of the beginning of smelting technology in the Levant and has been contested by various scholars since its publication. In this study, we present results of archaeointensity experiments conducted on slag fragments from the site. The slag yielded an excellent ancient geomagnetic value (64.1 +/- 1.1 mu T) that, when compared to the Levantine master curve, suggests an age not older than the second millennium and most probably between the 13th and 11th centuries bce. In addition to demonstrating the applicability of geomagnetic archaeointensity experiments to independent dating of slag, we discuss the implications of the current results for the socio-historical picture of the Timna Valley, and in particular for the way in which technological developments were previously modelled in the archaeometallurgical research on the region.

Ben-Yosef, E, Shaar R, Tauxe L, Levy TE, Kassianidou V.  2011.  The Cyprus Archaeomagnetic Project (CAMP): targeting the slag deposits of Cyprus and the Eastern Mediterranean. Antiquity. 85 AbstractWebsite
Ben-Yosef, E, Tauxe L, Ron H, Agnon A, Avner U, Najjar M, Levy TE.  2008.  A new approach for geomagnetic archaeointensity research: insights on ancient metallurgy in the Southern Levant. Journal of Archaeological Science. 35:2863-2879.   10.1016/j.jas.2008.05.016   AbstractWebsite

We present results from an archaeointensity investigation based on a relatively unexploited recording medium, copper slag deposits. Together with a recently improved experimental design for the archaeointensity experiment, we demonstrate the applicability of this medium, as well as other archaeometallurgical artifacts, for the study of the ancient geomagnetic field intensity. In addition to archaeointensity data from well-dated archaeological contexts, we obtained reliable archaeointensity results from poorly dated or contentious archaeometallurgical sites in the Southern Levant. These results shed new light on the dating of these sites, among them the copper smelting installation of Timna 39b a site that has important implications for the beginning of metallurgy during the fifth millennium BCE. The paper also aims to introduce archaeointensity research to the archaeologist scholar, and to encourage further collaboration between the disciplines in future research. (C) 2008 Elsevier Ltd. All rights reserved.

Ben-Yosef, E, Levy TE, Higham T, Najjar M, Tauxe L.  2010.  The beginning of Iron Age copper production in the southern Levant: new evidence from Khirbat al-Jariya, Faynan, Jordan. Antiquity. 84:724-746. AbstractWebsite

The authors have explored the workplace and house of copper workers of the early Iron Age (twelfth to tenth century BC) in Jordan's Wadi Faynan copper ore district, showing that it belongs in time between the collapse of the great Bronze Age states and the arrival of Egyptians in the area under Sheshong I. They attribute this production to local - tribes perhaps those engaged in building the biblical kingdom of Edom.

Ben-Yosef, E, Shaar R, Tauxe L, Ron H.  2012.  A chronological framework for Iron Age copper production at Timna (Israel). Bulletin of the American Schools of Oriental Research. 367:31-71.   10.5615/bullamerschoorie.367.0031  
Biggin, A, Piipsa E, Pesonen L, Holme R, Paterson G, Veikkolainen T, Tauxe L.  2015.  Palaeomagnetic field intensity variations suggest Mesoproterozoic inner-core nucleation. Nature. 526:245-248.   10.1038/nature15523  
Bijl, PK, Bendle JAP, Bohaty SM, Pross J, Schouten S, Tauxe L, Stickley CE, McKay RM, Rohl U, Olney M, Sluijs A, Escutia C, Brinkhuis H.  2013.  Eocene cooling linked to early flow across the Tasmanian Gateway. Proceedings of the National Academy of Sciences of the United States of America. 110:9645-9650.   10.1073/pnas.1220872110   AbstractWebsite

The warmest global temperatures of the past 85 million years occurred during a prolonged greenhouse episode known as the Early Eocene Climatic Optimum (52-50 Ma). The Early Eocene Climatic Optimum terminated with a long-term cooling trend that culminated in continental-scale glaciation of Antarctica from 34 Ma onward. Whereas early studies attributed the Eocene transition from greenhouse to icehouse climates to the tectonic opening of Southern Ocean gateways, more recent investigations invoked a dominant role of declining atmospheric greenhouse gas concentrations (e.g., CO2). However, the scarcity of field data has prevented empirical evaluation of these hypotheses. We present marine microfossil and organic geochemical records spanning the early-to-middle Eocene transition from the Wilkes Land Margin, East Antarctica. Dinoflagellate biogeography and sea surface temperature paleothermometry reveal that the earliest throughflow of a westbound Antarctic Counter Current began similar to 49-50 Ma through a southern opening of the Tasmanian Gateway. This early opening occurs in conjunction with the simultaneous onset of regional surface water and continental cooling (2-4 degrees C), evidenced by biomarker- and pollen-based paleothermometry. We interpret that the westbound flowing current flow across the Tasmanian Gateway resulted in cooling of Antarctic surface waters and coasts, which was conveyed to global intermediate waters through invigorated deep convection in southern high latitudes. Although atmospheric CO2 forcing alone would provide a more uniform middle Eocene cooling, the opening of the Tasmanian Gateway better explains Southern Ocean surface water and global deep ocean cooling in the apparent absence of (sub-) equatorial cooling.

Bloemendal, J, Tauxe L, Valet J-P.  1988.  High resolution, whole-core magnetic susceptibility logs from Leg 108. Proceedings of the Ocean Drilling Program, Pt. A. 108:1005-1013.   10.2973/  
Bloemendal, J, King JW, Tauxe L, Valet JP.  1989.  Rock-magnetic stratigraphy of Leg 108 Sites 658, 659, 661, and 665, Eastern Tropical Atlantic. Proceedings of the Ocean Drilling Program Scientific Results. 108:415-428.   10.2973/   Abstract

The results of detailed rock-magnetic measurements of selected stratigraphic intervals at Ocean Drilling Program Leg 108 Sites 658, 659, 661, and 665 are as follows: 1. At Site 658, it is likely that the entire interval was extensively affected by reductive diagenesis, resulting in the loss of fine-grained magnetite. At Sites 659 and 665, we suspect that a similar diagenetic alteration of fine-grained magnetite occurred, but that it was confined to discrete intervals. At Site 661, the uppermost 60-70 mbsf of the section appears to be relatively unaffected by reductive diagenesis; however, we suspect that the low carbonate content of sediments below were affected by oxidative diagenesis/authigenesis, resulting in the production of ultrafine-grained ferrimagnetic material. 2. Preliminary spectral analyses of the uppermost 70 mbsf (i.e., unaltered) rock-magnetic record at Site 661 suggest a decrease in the frequency of magnetite grain-size fluctuations after 2.9 Ma.

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.

Bowles, J, Gee J, Hildebrand J, Tauxe L.  2002.  Archaeomagnetic intensity results from California and Ecuador: evaluation of regional data. Earth and Planetary Science Letters. 203:967-981.   10.1016/s0012-821x(02)00927-5   AbstractWebsite

We present new archaeointensity data for southeastern California (similar to33degreesN, similar to115degreesW, 50-1500 yr BP) and northwestern South America (Ecuador, 2.4degreesS, 80.7degreesW, 4000-5000 yr BP). These results represent the only data from California, as well as the oldest archaeointensity data now available in northwestern South America. In comparing our results to previously published data for the southwestern United States and northwestern South America, we note that significant scatter in the existing data makes comparisons and interpretations difficult. We undertake an analysis of the sources of data scatter (including age uncertainty, experimental errors, cooling rate differences, magnetic anisotropy, and field distortion) and evaluate the effects of scatter and error on the smoothed archaeointensity record. By making corrections where possible and eliminating questionable data, scatter is significantly reduced, especially in South America, but is far from eliminated. However, we believe the long-period fluctuations in intensity can be resolved, and differences between the Southwestern and South American records can be identified. The Southwest data are distinguished from the South American data by much higher virtual axial dipole moment values from similar to 0-600 yr BP and by a broad low between similar to 1000-1500 yr BP. Comparisons to global paleofield models reveal disagreements between the models and the archaeointensity data in these two regions, underscoring the need for additional intensity data to constrain the models in much of the world. (C) 2002 Elsevier Science B.V. All rights reserved.

Cai, SH, Tauxe L, Deng CL, Qin HF, Pan YX, Jin GY, Chen XX, Chen W, Xie F, Zhu RX.  2016.  New archaeomagnetic direction results from China and their constraints on palaeosecular variation of the geomagnetic field in Eastern Asia. Geophysical Journal International. 207:1332-1342.   10.1093/gji/ggw351   AbstractWebsite

We carried out an archaeomagnetic directional study on 38 oriented samples (bricks and baked clays) collected from four archaeological locations at three provinces in China. The ages of our samples, spanning from similar to 3000 BCE to similar to 1300 CE, were constrained using a combination of archaeological context, radiocarbon dating and stratigraphic information. Rock magnetic results demonstrate that the main magnetic minerals of the studied samples are magnetite and/or hematite in single domain and superparamagnetic states. A total of 20 new reliable archaeodirectional data from 12 independent sites are obtained after thermal demagnetization experiments. These are the first set of archaeodirectional data in China produced since the 1990s. The published data are largely from the past 2 kyr and data from older time periods are rare. Our new data, especially those from period older than 3 ka, fill many gaps of the presently published dataset and will provide strong constraints on palaeosecular variation of the geomagnetic field in Eastern Asia and on the improvement of global models. Quite a few inflection points in the direction of the geomagnetic field are recorded in Eastern Asia over the past 10 kyr and some of them synchronize with the maximums or minimums of the palaeointensity. The palaeosecular variation rates are very low (based on present data distribution) before 2000 BCE and then start to increase and fluctuate afterward, which is generally consistent with the pattern of palaeointensity variations in this area.

Cai, S, Tauxe L, Deng C, Pan Y, Zheng J, Xie F, Qin H, Zhu R.  2014.  Geomagnetic intensity variations for the past 8 kyr: New archaeointensity results from Eastern China. Earth and Planetary Science Letters. 392:217-229.   10.1016/j.epsl.2014.02.030  
Constable, C, Tauxe L.  1990.  The Bootstrap for Magnetic Susceptibility Tensors. Journal of Geophysical Research-Solid Earth and Planets. 95:8383-8395.   10.1029/JB095iB06p08383   AbstractWebsite

In studies of the anisotropy of susceptibility or remanence of paleomagnetic samples it is conventional to specify the anisotropy in terms of the parameters of the anisotropy ellipsoids, namely the directions of the principal axes of the ellipsoid and their associated eigenvalues. Confidence intervals for these parameters have in the past often been estimated by using a linearization scheme to propagate the effect of small changes through the eigenvalue decomposition. The validity of these approximations is explored using a Monte-Carlo simulation from measurements that are presumed normally distributed, showing that there are circumstances in which the linearization scheme gives confidence intervals that are much too small. Q-Q plots indicate that the common assumption that the noise in the measurements is Gaussian does not always hold. Because of these shortcomings in the conventional technique we propose using a bootstrap resampling scheme to find empirically the distribution of uncertainties in the results. Confidence intervals for the eigenvalues are found directly from their empirical distributions. For the principal axes, approximate elliptical regions of confidence on the unit sphere are parameterized in terms of the Kent or FB5 distribution. The number of modes observed in the distribution of eigenvalues obtained by bootstrapping is used to classify the shape of the susceptibility ellipsoid as spherical, oblate, prolate or triaxial. The empirical nature of the bootstrap technique allows the extension of the analysis of uncertainties to parameters derived from the principal susceptibilities, such as percentage anisotropy or shape factor.

Constable, CG, Tauxe L.  1987.  Paleointensity In The Pelagic Realm - Marine Sediment Data Compared With Archaeomagnetic And Lake Sediment Records. Geophysical Journal of the Royal Astronomical Society. 90:43-59.   10.1111/j.1365-246X.1987.tb00674.x   AbstractWebsite

Four box cores collected from the Ontong—Java plateau during the Eurydice expedition have been used to make relative geomagnetic palaeo-intensity measurements. Rock magnetic measurements on the sediments show that they are characterized by a uniform magnetic mineralogy, and that they are suitable for relative intensity estimates. These are obtained by normalizing the NRM by an ARM imparted in a low DC bias field. the palaeoceanographic event known as the preservation spike is used to establish a crude time-scale for the record so that it may be compared with other data from the same region, and also with global palaeointensity estimates. the marine sediment data are quite similar to Australian intensity data from lake sediments and archaeomagnetic sources, but as might be expected exhibit some obvious differences from the global record.

Constable, CG, Tauxe L, Parker RL.  1998.  Analysis of 11 Myr of geomagnetic intensity variation. Journal of Geophysical Research-Solid Earth. 103:17735-17748.   10.1029/98jb01519   AbstractWebsite

We have conducted a detailed exploratory analysis of an II million year long almost continuous record of relative geomagnetic paleointensity from a sediment core acquired on Deep Sea Drilling Project Leg 73, at Site 522 in the South Atlantic. We assess the quality of the paleointensity record using spectral methods and conclude that the relative intensity record is minimally influenced by climate variations. Isothermal remanence is shown to be the most effective normalizer for these data, although both susceptibility and anhysteretic remanence are also adequate. Statistical analysis shows that the paleointensity variations follow a gamma distribution, and are compatible with predictions from modified paleosecular variation models and global absolute paleointensity data. When subdivided by polarity interval, the variability in paleointensity is proportional to the average, and further, the average is weakly correlated with interval length. Spectral estimates for times from 28.77 until 22.74 Ma, when the reversal rate is about 4 Myr(-1), are compatible with a Poisson model in which the spectrum of intensity variations is dominated by the reversal process in the frequency range 1-50 Mgr(-1) In contrast, between 34.7 and 29.4 Ma, when the reversal rate is about 1.6 Myr(-1), the spectra indicate a different secular variation regime. The magnetic field is stronger, and more variable, and a strong peak in the spectrum occurs at about 8 Myr(-1). This peak magi be a reflection of the same signal as recorded by the small variations known as tiny wiggles seen in marine magnetic anomaly profiles.

Constable, C, Tauxe L.  1996.  Towards absolute calibration of sedimentary paleointensity records. Earth and Planetary Science Letters. 143:269-274.   10.1016/0012-821x(96)00128-8   AbstractWebsite

Using relative paleointensity estimates derived from twelve globally distributed pelagic sediment cores, we assess whether they record a signal consistent with that expected from a dominant geocentric axial dipole, The cores span the Matuyama-Brunhes boundary and we normalize the observations by supposing that at the time the direction reverses the intensity low reflects only the non-axial-dipole contribution to the field. We further assume that this non-axial-dipole contribution to the field is invariant with geographic location. From absolute paleointensity compilations we estimate its size to be about 7.5 mu T; this supplies the calibration for the axial dipole signal away from the extreme low in intensity, The data predict the dipole field variation with latitude with similar accuracy to that observed in absolute paleointensity records, and show similar behavior when transformed to virtual axial dipole moments.

Cook, CP, van de Flierdt T, Williams T, Hemming SR, Iwai M, Kobayashi M, Jimenez-Espejo FJ, Escutia C, Gonzalez JJ, Khim BK, McKay RM, Passchier S, Bohaty SM, Riesselman CR, Tauxe L, Sugisaki S, Galindo AL, Patterson MO, Sangiorgi F, Pierce EL, Brinkhuis H, Scientists IE318.  2013.  Dynamic behaviour of the East Antarctic ice sheet during Pliocene warmth. Nature Geoscience. 6:765-769.   10.1038/ngeo1889   AbstractWebsite

Warm intervals within the Pliocene epoch (5.33-2.58 million years ago) were characterized by global temperatures comparable to those predicted for the end of this century(1) and atmospheric CO2 concentrations similar to today(2-4). Estimates for global sea level highstands during these times(5) imply possible retreat of the East Antarctic ice sheet, but ice-proximal evidence from the Antarctic margin is scarce. Here we present new data from Pliocene marine sediments recovered offshore of Adelie Land, East Antarctica, that reveal dynamic behaviour of the East Antarctic ice sheet in the vicinity of the low-lying Wilkes Subglacial Basin during times of past climatic warmth. Sedimentary sequences deposited between 5.3 and 3.3 million years ago indicate increases in Southern Ocean surface water productivity, associated with elevated circum-Antarctic temperatures. The geochemical provenance of detrital material deposited during these warm intervals suggests active erosion of continental bedrock from within the Wilkes Subglacial Basin, an area today buried beneath the East Antarctic ice sheet. We interpret this erosion to be associated with retreat of the ice sheet margin several hundreds of kilometres inland and conclude that the East Antarctic ice sheet was sensitive to climatic warmth during the Pliocene.

Cromwell, G, Constable CG, Staudigel H, Tauxe L, Gans P.  2013.  Revised and updated paleomagnetic results from Costa Rica. Geochemistry Geophysics Geosystems. 14:3379-3388.   10.1002/ggge.20199   AbstractWebsite

Paleomagnetic results from globally distributed lava flows have been collected and analyzed under the time-averaged field initiative (TAFI), a multi-institutional collaboration started in 1996 and designed to improve the geographic and temporal coverage of the 0-5 Ma paleomagnetic database for studying both the time-averaged field and its very long-term secular variations. Paleomagnetic samples were collected from 35 volcanic units, either lava flows or ignimbrites, in Costa Rica in December 1998 and February 2000 from the Cordilleras Central and Guanacaste, the underlying Canas, Liberia and Bagaces formations and from Volcano Arenal. Age estimates range from approximately 40 ka to slightly over 6 Ma. Although initial results from these sites were used in a global synthesis of TAFI data by Johnson et al. (2008), a full description of methodology was not presented. This paper documents the definitive collection of results comprising 28 paleomagnetic directions (24 normal, 4 reversed), with enhanced precision and new geological interpretations, adding two paleointensity estimates and 19 correlated Ar-40/Ar-39 radiometric ages. The average field direction is consistent with that of a geocentric axial dipole and dispersion of virtual geomagnetic poles (17.34.6 degrees) is in general agreement with predictions from several statistical paleosecular variation models. Paleointensity estimates from two sites give an average field strength of 26.3 T and a virtual axial dipole moment of 65 ZAm(2). The definitive results provide a useful augmentation of the global database for the longer term goal of developing new statistical descriptions of paleomagnetic field behavior.

Cromwell, G, Tauxe L, Halldorsson SA.  2015.  New paleointensity results from rapidly cooled Icelandic lavas: Implications for Arctic geomagnetic field strength. Journal of Geophysical Research-Solid Earth. 120:2913-2934.   10.1002/2014jb011828   AbstractWebsite

The Earth's magnetic field is assumed to be a geocentric axial dipole (GAD) when averaged over sufficient time (10(5)-10(6)years). Recent investigations of global paleosecular variation and time-averaged field behavior on million year timescales generally support a predominantly dipole field in the Northern Hemisphere, but unique field structures at high southern latitudes suggest the presence of a substantial (g) over bar (0)(2) quadrupolar component. Average paleointensity results from Antarctica are approximately half the value predicted by a GAD field; this behavior has not been sufficiently investigated because there is a paucity of absolute paleointensity data from the high latitudes of the Arctic and Antarctic, so no adequate comparisons have been made between the two regions. We collected glassy volcanic material from 129 subaerial and subglacial volcanic units in Iceland in order to provide a suitable intensity data set at high northern latitudes. Forty-four sites met our very strict specimen and site level selection criteria. Four Holocene sites have a median intensity value of 55.8 +/- 15.6 mu T (virtual axial dipole moment=78.1 +/- 22.0ZAm(2)), consistent with the present-day field. Thirty-seven sites are between 11ka and 3.35Ma with a median intensity of 33.1 +/- 8.3 mu T (47.0 +/- 11.6ZAm(2)). This median intensity is indistinguishable from some long-term global field strength estimates. Reevaluation of existing high-latitude data suggests a general agreement with our Iceland results, but there are still too few Antarctic sites to adequately compare Arctic and Antarctic field behaviors.

Cromwell, G, Tauxe L, Halldorsson SA.  2015.  New paleointensity results from rapidly cooled Icelandic lavas: Implications for Arctic geomagnetic field strength. J. Geophys. Res.. 120 :2913-2934.   10.1002/2014JB011828.  
Cromwell, G, Tauxe L, Staudigel H, Constable CG, Koppers AAP, Pedersen RB.  2013.  In search of long-term hemispheric asymmetry in the geomagnetic field : Results from high northern latitudes. Geochemistry Geophysics Geosystems. 14:3234-3249.   10.1002/ggge.20174   AbstractWebsite

Investigations of the behavior of the geomagnetic field on geological timescales rely on globally distributed data sets from dated lava flows. We present the first suitable data from the Arctic region, comprising 37 paleomagnetic directions from Jan Mayen (71 degrees N, 0.2-461 ka) and Spitsbergen (79 degrees N, 1-9.2 Ma) and five paleointensity results. Dispersion of the Arctic virtual geomagnetic poles over the last 2 Ma (27.34.0 degrees) is significantly lower than that from published Antarctic data sets (32.15.0 degrees). Arctic average virtual axial dipole moment (76.824.3 ZAm(2)) is high in comparison to Antarctica over the same time interval (34.88.2 ZAm(2)), although the data are still too sparse in the Arctic to be definitive. These data support a long-lived hemispheric asymmetry of the magnetic field, contrasting higher, more stable fields in the north with lower average strength and more variable field directions in the south. Such features require significant non-axial-dipole contributions over 10(5)-10(6) years.

Cromwell, G, Tauxe L, Staudigel H, Ron H.  2015.  Paleointensity estimates from historic and modern Hawaiian lava flows using volcanic glass as a primary source material. Phys. Earth Planet. Int.. 241:44-56.   10.1016/j.pepi.2014.12.007  
Cronin, M, Tauxe L, Constable C, Selkin P, Pick T.  2001.  Noise in the quiet zone. Earth and Planetary Science Letters. 190:13-30.   10.1016/s0012-821x(01)00354-5   AbstractWebsite

We have carried out a detailed paleomagnetic investigation of two stratigraphically overlapping sections from the Scaglia Bianca Formation (similar to 85-89.5 Ma) in the Umbria-Marche area in central Italy. Sampling was conducted over 32 in and 7 in intervals at La Roccaccia and Furlo respectively. After AF cleaning the majority of specimens show the expected normal magnetic field orientation, however a number of specimens are directionally anomalous. Some of these deviant specimens are accompanied by apparent spikes or dips in normalized intensity. A detailed investigation of rock magnetics shows that most of these deviations are not a sign of excursionary geomagnetic field behavior, but rather correspond to specimens with distinct rock magnetic characteristics and are therefore rock magnetic 'noise'. Such specimens should not be interpreted as records of the geomagnetic field. Our experience suggests that detailed rock magnetic and magnetic fabric analysis should be done on all anomalous directions prior to interpreting them as geomagnetic field behavior. After elimination of rock magnetic noise in the Scaglia Bianca data sets, there is a high degree of agreement in direction and to a lesser extent relative intensity between correlative portions of the two sections. We therefore offer this data set as a robust record of geomagnetic field behavior during the 4.5 Myr interval represented by the La Roccaccia section. A statistical analysis of the relative intensity observations suggests that this period of the Cretaceous Normal Superchron is characterized by a normalized variability in paleointensity (standard deviation about 28% of the mean value) that is significantly lower than seen during the Oligocene over intervals in which reversals or tiny wiggles occur (typically about 50%). The directional stability results in virtual geomagnetic pole dispersion compatible with that found in volcanic rocks from around the same latitude and ranging in age from 80 to 110 Ma. (C) 2001 Elsevier Science B.V. All rights reserved.

Dallanave, E, Muttoni G, Agnini C, Tauxe L, Rio D.  2012.  Is there a normal magnetic-polarity event during the Palaeocene-Eocene thermal maximum (similar to 55 Ma)? Insights from the palaeomagnetic record of the Belluno Basin (Italy) Geophysical Journal International. 191:517-529.   10.1111/j.1365-246X.2012.05627.x   Abstract

In the lowermost Eocene sedimentary record of Ocean Drilling Program Site 1262 (Leg 208, Walvis Ridge, South Atlantic Ocean), the presence of a similar to 53-kyr-long normal polarity event has been recorded within the similar to 2.55-Myr-long reverse polarity Chron C24r (similar to 53.355.9 Ma) and termed PalaeoceneEocene magnetic reversal (PEMR). The origin of the PEMR has been speculatively related to a change in the Earth's rotation rate that was in turn influenced by an abrupt overturning of the ocean-atmosphere circulation that occurred during the PalaeoceneEocene thermal maximum (PETM) at similar to 55 Ma. Such provocative genesis for a magnetic-polarity reversal demands the PEMR to be confirmed (or refuted) in additional PETM sections. Here, we present detailed palaeomagnetic and rock-magnetic data from the Forada and Cicogna sections of the Belluno Basin in NE Italy, which contain an expanded and continuous record of the PETM termed clay marl unit (CMU). Our data indicate that these sediments were deposited during a continuous interval of reverse geomagnetic field polarity. We therefore conclude that no magnetic-polarity reversals occurred throughout the PETM. In addition, we studied the origin of the high degree of flattening affecting the characteristic magnetic component directions of the sediments, which we interpret as due to a combination of depositional inclination shallowing typical of detrital haematite, and post-depositional compaction of clays, particularly abundant in the carbonate-depleted CMU.

Dallanave, E, Tauxe L, Muttoni G, Rio D.  2010.  Silicate weathering machine at work: Rock magnetic data from the late Paleocene-early Eocene Cicogna section, Italy. Geochemistry Geophysics Geosystems. 11   10.1029/2010gc003142   AbstractWebsite

We describe a scenario of climate forcing on sedimentation recorded in the late Paleocene-early Eocene Cicogna marine section from the Belluno Basin ( NE Italy). Previously published magneto-biostratigraphic data revealed that the similar to 81 m Cicogna section extends from Chron C25r to Chron C23r spanning the NP7/NP8-NP12 nannofossil zones (similar to 52.2-56.6 Ma). Using previously published rock magnetic data, augmented by data from this study, we describe and thoroughly discuss a pronounced increase of hematite ( relative to maghemite or magnetite) between similar to 54.9 and 54.6 Ma immediately above the Paleocene-Eocene boundary, followed by a second, long-term increasing trend from similar to 54 Ma up to similar to 52.2 Ma in the early Eocene. This hematite is essentially of detrital origin, insofar as it is associated with a strong shallow bias of paleomagnetic inclinations, and is interpreted to have formed on land by the weathering of Fe-bearing silicates and other primary minerals. We speculate that the warm and humid climate typical of the Paleocene-Eocene thermal maximum (PETM, similar to 54.9 Ma) as well as of the warming trend leading to the early Eocene climatic optimum (EECO; similar to 52-50 Ma) enhanced continental weathering of silicate rocks with the consequent production, transport, and sedimentation of detrital hematite grains. This hypothesis is confirmed by a statistical correlation between the rock magnetic properties and global climate as revealed by a standard benthic oxygen isotope record from the literature. Our temporal coupling between oxidation state of sedimentary magnetic phases and global climate is therefore consistent with the existence in the Paleocene-Eocene of the silicate weathering negative feedback mechanism for the long-term stabilization of the Earth's surface temperature.

Dallanave, E, Bachtadse V, Crouch EM, Tauxe L, Shepherd CL, Morgans HEG, Hollis CJ, Hines BR, Sugisaki S.  2016.  Constraining early to middle Eocene climate evolution of the southwest Pacific and Southern Ocean. Earth and Planetary Science Letters. 433:380-392.   10.1016/j.epsl.2015.11.010   AbstractWebsite

Studies of early Paleogene climate suffer from the scarcity of well-dated sedimentary records from the southern Pacific Ocean, the largest ocean basin during this time. We present a new magnetostratigraphic record from marine sediments that outcrop along the mid-Waipara River, South Island, New Zealand. Fully oriented samples for paleomagnetic analyses were collected along 45 m of stratigraphic section, which encompasses magnetic polarity Chrons from C23n to C21n (similar to 51.5-47 Ma). These results are integrated with foraminiferal, calcareous nannofossil, and dinoflagellate cyst (dinocyst) biostratigraphy from samples collected in three different expeditions along a total of similar to 80 m of section. Biostratigraphic data indicates relatively continuous sedimentation from the lower Waipawan to the upper Heretaungan New Zealand stages (i.e., lower Ypresian to lower Lutetian, 55.5 to 46 Ma). We provide the first magnetostratigraphically-calibrated age of 48.88 Ma for the base of the Heretaungan New Zealand stage (latest early Eocene). To improve the correlation of the climate record in this section with other Southern Ocean records, we reviewed the magnetostratigraphy of Ocean Drilling Program (ODP) Site 1172 (East Tasman Plateau) and Integrated Ocean Drilling Program (IODP) Site 131356 (Wilkes Land Margin, Antarctica). A paleomagnetic study of discrete samples could not confirm any reliable magnetic polarity reversals in the early Eocene at Site 1172. We use the robust magneto-biochronology of a succession of dinocyst bioevents that are common to mid-Waipara, Site 1172, and Site U1356 to assist correlation between the three records. A new integrated chronology offers new insights into the nature and completeness of the southern high-latitude climate histories derived from these sites. (C) 2015 Elsevier B.V. All rights reserved.

Deino, AL, Tauxe L, Monaghan M, Hill A.  2002.  Ar-40/Ar-30 geochronology and paleomagnetic stratigraphy of the Lukeino and lower Chemeron Formations at Tabarin and Kapcheberek, Tugen Hills, Kenya. Journal of Human Evolution. 42:117-140.   10.1006/jhev.2001.0521   AbstractWebsite

Ar-40/Ar-39 single-crystal laser-fusion dating, K-Ar dating, and paleo-magnetic reversal stratigraphy have been used to determine the chronostratigraphy of the Kabarnet Trachyte, Lukeino Formation, Kaparaina Basalt Formation, and Chemeron Formation at the sites of Kapcheberek (BPRP#77) and Tabarin (BPRP#77) in the Tugen Hills, Kenya. The succession ranges in age from 6(.)56-3(.)8 Ma. The upper Lukeino Formation at Kapcherberek, including the fauna from the site BPRP#76, was deposited during chron C3r and can be constrained to the interval 5(.)88-5(.)72 Ma. The Chemeron Formation at Tabarin includes at the base an ignimbrite and associated basal air-fall tuff with a combined age of 5(.)31 +/- 0(.)03 Ma. Sedimentary and volcaniclastic rocks of the Chemeron Formation which unconformably overlie the ignimbrite record chrons C3n.2n through C2Ar. The combined Ar-40/Ar-39 and paleomagnetic data constrain the age of this sequence to 4(.)63-3(.)837 Ma. The age of the Tabarin mandible fragment (KNM-TH 13150) and associated fauna at site BPRP#77 in the Chemeron Formation is 4(.)48-4(.)41 Ma, marginally older than similar early hominids from Aramis, Ethiopia. Basin subsidence appears to be defining an overall accumulation rate of about 17 cm/ka over the 2(.)7 Ma represented at Tabarin and Kapcheberek, despite episodes of rapid accumulation and hiatuses. (C) 2002 Academic Press.

Deino, A, Tauxe L, Monaghan M, Drake R.  1990.  Ar-40/Ar-39 Age Calibration of the Lithomagnetic and Paleomagnetic Stratigraphies of the Ngorora Formation, Kenya. Journal of Geology. 98:567-587. AbstractWebsite
Di Chiara, A, Tauxe L, Speranza F.  2014.  Paleointensity determination from Sao Miguel (Azores Archipelago) over the last 3 ka. Physics of the Earth and Planetary Interiors.   10.1016/j.pepi.2014.06.008   Abstract

Paleointensity data from the Atlantic Ocean are rare. We present new paleointensity data from Sao Miguel (Azores Islands, Portugal) based on 20 paleomagnetic sites from 13 lava flows emplaced over the last 3000 years. Ten lava flows are radiocarbon dated, whereas three flows were paleomagnetically dated and one site was dated using stratigraphic relations. All the samples, previously investigated to recover paleo-directions, were subjected to IZZI experiments. Importantly, the new data are internally consistent, agree with Moroccan and European datasets, and offer new constraints for global geomagnetic field models. Some of the ages of the paleomagnetically dated lava flows have been revised based on the intensity data presented here. The inferred Virtual Axial Dipole Moments (VADMs) range from 68.2 to 163.5 ZAm(2). A peak in field strength with an estimated age of around 600 BC is well supported by two sites from the same flow (Furna), and is comparable to the high intensity values found in Portugal for the same age and the earlier field peak at about 1000 BC in the Levant. A gradient in VADM values with latitude from northwestern Africa and across Europe between 100 and 1000 AD is confirmed as well as its absence from between 0 to 100 AD. (C) 2014 Elsevier B.V. All rights reserved.

Donadini, F, Elming SA, Tauxe L, Halenius U.  2011.  Paleointensity determination on a 1.786 Ga old gabbro from Hoting, Central Sweden. Earth and Planetary Science Letters. 309:234-248.   10.1016/j.epsl.2011.07.005   AbstractWebsite

Paleointensities from Precambrian rocks are rare and might be biased by remagnetization processes. Here we present new analyses of samples from a 1.786 Ga gabbro near Hoting, Central Sweden. Rock magnetic and mineralogical analyses indicate that one of the sites (site 5) may be pristine, whereas the others exhibit evidence of alteration. Characteristic remanent magnetization was determined using principal component analysis for each sample and was compared with results obtained in a previous study of Elming et al. (2009). Intensity measurements from site 5 show higher values compared to those of the other sites, suggesting that alteration processes may lead to underestimation of the field intensity. After cooling rate and anisotropy correction, the field moment at 1.786 Ga was estimated to be 25.6 +/- 33 ZAm(2) and 15.2 +/- 6.1 ZAm(2) from site 5 only and from all sites respectively. We consider the result from site 5 to be more accurate owing to the lack of evidence for alteration: our estimates agree well with the Proterozoic VDM values suggested by Biggin et al. (2009). (C) 2011 Elsevier B.V. All rights reserved.

Escutia, C, Brinkhuis H, Scientists E318.  2014.  From Greenhouse to Icehouse at the Wilkes Land Antarctic Margin: IODP Expedition 318 Synthesis of Results. Developments in Marine Geology. 7, Amsterdam: Elsevier   10.1016/B978-0-444-62617-2.00012-8  
Flynn, JJ, Tauxe L.  1998.  Magnetostratigraphy of the Upper Paleocene-Lower Eocene marine and terrestrial sequences . Late Paleocene-Early Eocene events. ( Aubry MP, S.G L, Berggren WA, Eds.).:67-90.: Columbia University Press Abstract
Friedman, R, Gee J, Tauxe L, Downing K, Lindsay E.  1992.  The Magnetostratigraphy of the Chitarwata and Lower Vihowa Formations of the Dera-Ghazi-Khan Area, Pakistan. Sedimentary Geology. 81:253-268.   10.1016/0037-0738(92)90074-2   AbstractWebsite

Three sections of the Chitarwata and lower Vihowa formations were sampled along the Dalana River on the southeastern flank of the Zinda Pir Dome in the southern Sulaiman Range near Dera Ghazi Khan, Pakistan. Together they provide nearly 800 m of a continuous sedimentary record of the Miocene derived from the uplifted Himalayan highlands. Previous studies have examined the Middle and Upper Miocene sediments, the Siwalik Group, of the Potwar Plateau to the north. However, detailed investigations of earlier periods are impossible in that area due to the absence of Oligocene and Lower Miocene sediments caused by continued overthrusting associated with the Himalayan orogeny. Fortunately, the Sulaiman basin to the south, which was further removed from the tectonic activity, provides a record of the Early Miocene in the form of the Chitarwata Formation. The Dalana A, B, and C sections (DGA, DGB, and DGC) were examined and sampled for this study. A magnetostratigraphic analysis was carried out to correlate and date the Chitarwata and Vihowa formations exposed in this area. The samples were subjected to step-wise demagnetization to resolve the primary and secondary remanent magnetization components. Thermal demagnetization trajectories indicate that the majority of samples have sufficient internal consistency that their calculated polarities are reliable. Likewise, the majority of the 126 measured sites showed statistically significant agreement between the three measured samples per site. However, the bimodal data set does not pass the reversal test and so is deemed unsuitable for tectonic interpretations. The individual sections were initially correlated using lithologic and stratigraphic methods, and the relationship was reinforced by the magnetostratigraphy. The composite DG section was tentatively correlated with the standard magnetic polarity time scale placing the disconformable base of the Chitarwata in the DGA section at just older than 22 Ma, the Chitarwata/Vihowa contact at 18.6 Ma, and the top of the Vihowa in the DGC section at about 16 Ma. The assignment of these dates to the Chitarwata will aid in future biostratigraphic and lithostratigraphic correlation of Early Miocene sediments, effectively extending the well-established Siwalik faunal sequence back by four million years.

Gallet, Y, Gee J, Tauxe L, Tarduno JA.  1993.  Paleomagnetic analyses of short normal polarity magnetic anomalies in the Matuyama Chron. Proceedings of the Ocean Drilling Program, Scientific Results. 130:547-559.   10.2973/   Abstract

We document three short normal intervals in the natural remanent magnetization of sediments within the Matuyama Chron. These three anomalous zones of magnetization between the Jaramillo and Olduvai subchrons were identified from continuous measurements of archive halves from Hole 803 A using the pass-through 2G cryogenic magnetometer at Scripps. The U-channel samples were taken from the three intervals, analyzed using the pass-through system, and then cut into discrete 1 -cm-thick samples. Measurements on discrete samples confirmed the presence of the upper normal polarity zone. Based on sedimentation rate calculations, this zone is confidently correlated with the Cobb Mountain Subchron. For the two other anomalous zones, complete thermal demagnetization revealed a high-stability component (250°-575°C) of reversed polarity. The intensity of the low-stability normal polarity component, normalized by susceptibility, remains roughly constant throughout the entire interval sampled, whereas the intensity of the high-stability reversed component is much lower within the normal zone than outside. We interpret these two normal zones, then, as periods of low (reversed polarity) geomagnetic field intensity resulting in low magnetization of the sediments; the periods of these low magnetization reversed polarity zones are completely masked by the component acquired viscously in a normal polarity field.

Gee, JS, Tauxe L, Constable C.  2008.  AMSSpin: A LabVIEW program for measuring the anisotropy of magnetic susceptibility with the Kappabridge KLY-4S. Geochemistry Geophysics Geosystems. 9   10.1029/2008gc001976   AbstractWebsite

Anisotropy of magnetic susceptibility (AMS) data are widely used as a petrofabric tool because the technique is rapid and nondestructive and because static measurement systems are capable of determining small degrees of anisotropy. The Kappabridge KLY-4S provides high resolution as a result of the large number of measurements acquired while rotating the sample about three orthogonal axes. Here we describe a graphical-based program called AMSSpin for acquiring AMS data with this instrument as well as a modified specimen holder that should further enhance the utility of this instrument. We also outline a method for analysis of the data (that differs in several ways from that of the software supplied with the instrument) and demonstrate that the measurement errors are suitable for using linear perturbation analysis to statistically characterize the results. Differences in the susceptibility tensors determined by our new program and the SUFAR program supplied with the instrument are small, typically less than or comparable to deviations between multiple measurements of the same specimen.

Gee, J, Tauxe L, Hildebrand JA, Staudigel H, Lonsdale P.  1988.  Nonuniform Magnetization of Jasper Seamount. Journal of Geophysical Research-Solid Earth and Planets. 93:12159-12175.   10.1029/JB093iB10p12159   AbstractWebsite

Paleopoles derived from seamounts have been used to reconstruct the tectonic history of ocean basins; however, the interpretation of seamount magnetization models and the validity of seamount paleopoles may be affected by inhomogeneous magnetization. Multibeam bathymetric data, sea surface and deep-tow magnetic field data, and paleomagnetic analyses of dredged samples were used to examine the origin of nonuniform magnetization within Jasper Seamount (30°27′N, 122°44′W). Models indicate that the seamount is predominantly reversely magnetized with local zones of normal polarity as corroborated by deep-tow measurements. Lithologies likely to be volumetrically important in a seamount edifice show highly variable magnetic properties. Basalts have high intensities (0.5–27.0 A/m), high Koenigsberger ratios (Q) and low viscous remanence (VRM) acquisition. Low Q ratios and high VRM acquisition coefficients of coarse-grained material and volcaniclastics suggest that they may have substantial viscous and induced components. Models for Jasper are characterized by low uniform intensities and far-sided paleopoles. The shallow model inclinations may be attributed to nondipolar components in the time-averaged geomagnetic field. The low intensities of the uniform models and the large nonuniform component in the seminorm solutions imply a complex distribution of magnetization sources within Jasper. This nonuniformity may result from either lithological variability or construction of the seamount spanning two or more polarity intervals.

Gee, JS, Tauxe L, Barge E.  1991.  Lower Jaramillo polarity transition records from the equatorial Atlantic and Indian oceans. Proceedings of the Ocean Drilling Program Scientific Results. 121:377-394.   10.2973/   Abstract

Two records of the geomagnetic polarity transition at the beginning of the Jaramillo Subchron (0.97 Ma) have been obtainedfrom sediments in the equatorial Atlantic (Leg 108, Site 665; 2.95°N, 340.33°E) and Indian (Leg 121, Site 758; 5.38°N, 90.35°E)oceans. Both cores yielded high-quality magnetostratigraphic results; however, the relatively low sedimentation rates, the weakmagnetizations, and complex demagnetization behavior of some transitional samples suggest that the record of the transitional fieldbehavior may be less reliable. In addition, variations in grain size preclude reliable paleointensity determinations although theremanence in both cores is apparently dominated by magnetite. Despite these possible complications, the two cores yield transitionalpaths that are neither far-sided nor near-sided. Together with published records that meet minimum reliability standards, the twoequatorial records presented here suggest that the lower Jaramillo transitional field morphology was significantly nonaxisymmetric.The mean normal and reversed inclinations from both cores deviate from the inclination expected from a geocentric axial dipole, asnoted in virtually all marine sediment cores. The observed inclinations provide further support for a polarity-dependent nondipolecontribution to the time-averaged field.