Export 204 results:
Sort by: Author Title [ Type  (Asc)] Year
Tauxe, L.  2010.  Essentials of paleomagnetism. :xvi,489p.., Berkeley: University of California Press Abstract
Tauxe, L.  1998.  Paleomagnetic principles and practice. Modern approaches in geophysics. :xi,299p.., Dordrecht ; Boston: Kluwer Academic Publishers Abstract
Book Chapter
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  
Tauxe, L.  1989.  Magnetostratigraphy. The Encyclopedia of Solid Earth Geophysics. ( Jones DE, Ed.).:740-746. Abstract
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
Tauxe, L, Yamazaki T.  2007.  Paleointensities . Geomagnetism in the Treatise on geophysics. 5( Schubert G, Ed.).:509-564.: Oxford-Elsevier Ltd Abstract
Tauxe, L, Yamazaki T.  2015.  Paleointensities. Treatise on Geophysics. 5, Amsterdam: Elsevier   10.1016/B978-0-444-53802-4.00107-X  
Tauxe, L, Kent DV.  2004.  A simplified statistical model for the geomagnetic field and the detection of shallow bias in paleomagnetic inclinations: Was the ancient magnetic field dipolar? Timescales of the paleomagnetic field, Geophysical Monograph. 145( Channell J, Ed.).:101-116., Washington, DC: American Geophysical Union, Abstract
Journal Article
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  
Tauxe, L, Hartl P.  1997.  11 million years of Oligocene geomagnetic field behaviour. Geophysical Journal International. 128:217-229.   10.1111/j.1365-246X.1997.tb04082.x   AbstractWebsite

An II million year long record of the Oligocene geomagnetic field has been obtained from pelagic sediments of DSDP Hole 522. An average sample spacing of 4 cm yielded approximately one specimen per 4 to 8 kyr. The rock magnetics are remarkably consistent across the entire interval. Previous work demonstrated a magnetic mineralogy dominated by magnetically stable magnetite. The natural remanent magnetism (NRM) carries an Oligocene polarity timescale that is in excellent agreement with the Oligocene reversal record as determined from marine magnetic anomalies (MMAs), including many of the so-called 'crypto-chrons'. Normalized NRM intensities from the undisturbed portions of the record yield a time series of variations with features consistent with a number of other palaeointensity time series derived from both sedimentary and lava sequences. These features include consistent, major decreases in palaeointensity (DIPs) at reversal boundaries, and occasional DIPs between reversal boundaries that could correspond to lineated 'tiny wiggles' in the MMA records. The data set suggests that the overall field strength was 40 per cent higher in the first half of the Oligocene when the average reversal frequency was 1.6 Myr(-1) than in the second half when the reversal frequency was 4 Myr(-1). There is also a weak dependence of average field strength on length of polarity interval. Finally, in the three cores suited to spectral analysis (of coherent polarity and relative intensity independent of lithological contamination), there is a persistent ca. 30-50 ka periodicity in the variations of the relative intensity, suggesting that the geomagnetic held 'pulses' at about this frequency, not only during the Brunhes (as demonstrated by Tauxe & Shackleton 1994), but in the Oligocene as well.

Stokking, LB, Tauxe L.  1987.  Acquisition of Chemical Remanent Magnetization by Synthetic Iron-Oxide. Nature. 327:610-612.   10.1038/327610a0   AbstractWebsite

A fundamental assumption of palaeomagnetism is that rocks can provide a reliable record of the Earth's magnetic field. It is known that as magnetic minerals undergo chemical change they acquire a form of chemical remanent magnetization (CRM)1. Indeed, the magnetic phases formed at different times in the history of the rock may add several components of CRM to its net magnetization2, so that a valid application of palaeomagnetism to the interpretation of geological history requires a knowledge of the different components of CRM and the time of their acquisition. There are two mechanisms responsible for CRM3: mineral alteration and crystal growth. To understand the properties and acquisition mechanisms of CRM associated with the growth of mineral crystals, which is known as grain-growth CRM4, we have developed a technique for the synthesis of haematite crystals under controlled conditions. We find that the acquired magnetization is parallel to the applied magnetic field.

Jiang, Z, Qin H, Liu Q, Dekkers MJ, Tauxe L, Barron V, Torrent J.  2015.  Acquisition of chemical remanent magnetization during experimental ferrihydrite-hematite conversion - implications for paleomagnetic studies of red beds,. Earth Planet. Sci. Let. . 428:1-10.   10.1016/j.epsl.2015.07.024  
Yu, YJ, Tauxe L.  2006.  Acquisition of viscous remanent magnetization. Physics of the Earth and Planetary Interiors. 159:32-42.   10.1016/j.pepi.2006.05.002   AbstractWebsite

Viscous remanent magnetization (VRM) has been frequently suggested as a possible source of magnetic anomalies in ocean crust and as an important contributor of natural remanent magnetization in some volcanic and sedimentary rocks. Most references to VRM assume a linear dependence with log(t), yet long-term experimental data on VRM, while scarce often disagree with this simple notion. Here, we investigate the angular-dependence, grain-size dependence, initial-state dependence, and time (t) dependence of VRM acquisition. We observe a non-linear log(t) dependence of VRM acquisition over all time intervals (> 10(4) S) for all the samples regardless of various experimental conditions. Echoing earlier studies, we also find that VRM acquisition is strongly dependent on the initial magnetic state of the samples. Samples in a thermally demagnetized initial-state were most susceptible to VRM acquisition. When VRM is produced parallel to the initial thermal remanence, VRM acquisition is negligible. VRM acquisition is more prevalent for magnetites in single-domain and multidomain (MD) grains than in the pseudo-single-domain range. In MD magnetites, frequent removal and restoration of samples (for the purpose of zero-field remanence measurement) apparently increases the efficiency of VRM acquisition. (c) 2006 Elsevier B.V. All rights reserved.

Tauxe, L, Opdyke ND, Pasini G, Elmi C.  1983.  Age of the Plio-Pleistocene Boundary in the Vrica Section, Southern Italy. Nature. 304:125-129.   10.1038/304125a0   AbstractWebsite

New palaeomagnetic data from the proposed Plio-Pleistocene boundary stratotype section (Vrica section, southern Italy) are presented here in order to improve the correlation of these sediments to the magnetic polarity time scale. If the interpretation preferred here is correct, the boundary falls above the Olduvai normal subchron at approximately 1.6 Myr.

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.

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.

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.

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
Johnson, CL, Wijbrans JR, Constable CG, Gee J, Staudigel H, Tauxe L, Forjaz VH, Salgueiro M.  1998.  Ar-40/Ar-39 ages and paleomagnetism of Sao Miguel lavas, Azores. Earth and Planetary Science Letters. 160:637-649.   10.1016/s0012-821x(98)00117-4   AbstractWebsite

We present new Ar-40/Ar-39 ages and paleomagnetic data for Sao Miguel island, Azores. Paleomagnetic samples were obtained for 34 flows and one dike; successful mean paleomagnetic directions were obtained for 28 of these 35 sites. Ar-40/Ar-39 age determinations on 12 flows from the Nordeste complex were attempted successfully: ages obtained are between 0.78 Ma and 0.88 Ma, in contrast to published K-Ar ages of 1 Ma to 4 Ma. Our radiometric ages are consistent with the reverse polarity paleomagnetic field directions, and indicate that the entire exposed part of the Nordeste complex is of a late Matuyama age. The duration of volcanism across Sao Miguel is significantly less than previously believed, which has important implications for regional melt generation processes, and temporal sampling of the geomagnetic field. Observed stable isotope and trace element trends across the island can be explained, at least in part, by communication between different magma source regions at depth. The Ar-40/Ar-39 ages indicate that our normal polarity paleomagnetic data sample at least 0.1 Myr (0-0.1 Ma) and up to 0.78 Myr (0-0.78 Ma) of paleosecular variation and our reverse polarity data sample approximately 0.1 Myr (0.78-0.88 Ma) of paleosecular variation. Our results demonstrate that precise radiometric dating of numerous flows sampled is essential to accurate inferences of long-term geomagnetic field behavior. Negative inclination anomalies are observed for both the normal and reverse polarity time-averaged field. Within the data uncertainties, normal and reverse polarity field directions are antipodal, but the reverse polarity field shows a significant deviation from a geocentric axial dipole direction. (C) 1998 Elsevier Science B.V. All rights reserved.

Cai, S, Jin G, Tauxe L, Deng C, Qin H, Pan Y, Zhu R.  2017.  Archaeointensity results spanning the past 6 kiloyears from eastern China and implications for extreme behaviors of the geomagnetic field. Proceedings of the National Academy of Sciences. 114:39-44.   10.1073/pnas.1616976114   AbstractWebsite

Variations of the Earth’s geomagnetic field during the Holocene are important for understanding centennial to millennial-scale processes of the Earth’s deep interior and have enormous potential implications for chronological correlations (e.g., comparisons between different sedimentary recording sequences, archaeomagnetic dating). Here, we present 21 robust archaeointensity data points from eastern China spanning the past ∼6 kyr. These results add significantly to the published data both regionally and globally. Taking together, we establish an archaeointensity reference curve for Eastern Asia, which can be used for archaeomagnetic dating in this region. Virtual axial dipole moments (VADMs) of the data range from a Holocene-wide low of ∼27 to “spike” values of ∼166 ZAm2 (Z: 1021). The results, in conjunction with our recently published data, confirm the existence of a decrease in paleointensity (DIP) in China around ∼2200 BCE. These low intensities are the lowest ever found for the Holocene and have not been reported outside of China. We also report a spike intensity of 165.8 ± 6.0 ZAm2 at ∼1300 BCE (±300 y), which is either a prelude to or the same event (within age uncertainties) as spikes first reported in the Levant.

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.

Peters, I, Tauxe L, Ben-Yosef E.  2017.  Archaeomagnetic dating of pyrotechnological contexts: A case study for copper smelting sites in the Central Timna Valley, Israel. Archaeometery.   10.1111/arcm.12322   Abstract

This study is focused on establishing age constraints for several copper slag deposits at the centre of the Timna Valley (Israel) via reconstruction of their ancient geomagnetic intensities as recorded by the individual slag samples at the time of their formation. The results show a correlation between the location of the slag deposits (labelled as individual ‘mounds’ in our survey) and their inferred ages, reflecting varying socio-economic and political dynamics in the region. While the slag mounds found at the unprotected foothills represent a variety of dates (mostly Early Islamic), the slag mounds on the hilltops are chronologically constrained to the early Iron Age (late 11th to 10th centuries bce), supporting the idea for a need for protection during this period. Furthermore, in comparing the new data with previous archaeomagnetic studies from Timna, we can assert the existence of simultaneous copper production at the archaeological Sites 30, 30a and 34. This gives further support to the claim of intense smelting in the central Timna Valley during the early Iron Age. Finally, this project demonstrates the potential of archaeomagnetic experiments to provide chronological insights, and their particular advantage in addressing pyrotechnology-related cases.

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.

Shackleton, NJ, Hall MA, Raffi I, Tauxe L, Zachos J.  2000.  Astronomical calibration age for the Oligocene-Miocene boundary. Geology. 28:447-450.   10.1130/0091-7613(2000)28<447:acafto>;2   AbstractWebsite

The stratotype section for the base of the Miocene is at a reversed (below) to normal (above) magnetic transition that is claimed to represent magnetic chron C6Cn.2n (o). Deep Sea Drilling Project (DSDP) Site 522 is the only location we are aware of that unambiguously records the three normal events of C6Cn. We have quantitatively determined the range of the short-lived nannofossil Sphenolithus delphix and the tower limit of S. disbelemnos in DSDP Holes 522 and 522A in order to calibrate their precise relationship to the magnetostratigraphy and to confirm the completeness of the record at this site. Astronomical tuning of Ocean Drilling Program (ODP) Sites 926, 928, and 929 shows that S. disbelemnos appears at 22.67 Ma and that the entire range of S. delphix is from about 22.98 Ma to 23.24 Ma. Using these ages, linear interpolation in DSDP Site 522 suggests that the age of C6Cn.2n (o) and of the Oligocene-Miocene boundary is 22.92 +/- 0.04 Ma. Our value, conservatively expressed as 22.9 +/- 0.1 Ma, is 0.9 m.y. younger than the currently accepted age of the Oligocene-Miocene boundary and of C6Cn.2n (o), which was assigned an age of 23.8 Ma, based on an estimate of 23.8 +/- 1 Ma for the Oligocene-Miocene boundary. The bulk-sediment carbon isotope data from DSDP Site 522 is correlated to the record from benthic foraminifera at ODP Site 929 to refine the calibration of magnetic reversals from C6Cn.1n (o) to C7n.2n (o) at DSDP Site 522 on the astronomical time scale.

Tauxe, L, Herbert T, Shackleton NJ, Kok YS.  1996.  Astronomical calibration of the Matuyama-Brunhes boundary: Consequences for magnetic remanence acquisition in marine carbonates and the Asian loess sequences. Earth and Planetary Science Letters. 140:133-146.   10.1016/0012-821x(96)00030-1   AbstractWebsite

We have compiled 19 records from marine carbonate cores in which the Matuyama-Brunhes boundary (MBB) has been reasonably well constrained within the astronomically forced stratigraphic framework using oxygen isotopes. By correlation of the delta(18)O data to a timescale based on astronomical forcing, we estimate astronomical ages for each of the MBB horizons. In all but one record the MBB occurs within Stage 19. Most magnetostratigraphic sections in Asian Loess place the MBB within a loess interval. Since loess deposition is presumed to be associated with glacial intervals, loess horizons should correspond to even-numbered oxygen isotope stages. A glacial age for the MBB is at odds with the results presented here, which firmly place the MBB within interglacial Stage 19. Inconsistency among the many loess sections and between the loess and the marine records suggests that the magnetic interpretation of loess sections may be more complicated than hitherto supposed. The mean of the Stage 19 age estimates for the MBB is 777.9 +/- 1.8 (N = 18). Inclusion of the single Stage 20 age results in a mean of 778.8 +/- 2.5 (N = 19). The astronomical age estimate of the MBB compares favorably with an (unweighted) mean of 778.2 +/- 3.5 (N = 10) from a compilation of Ar-40/Ar-39 results of transitional lava flows. Combining the two independent data sets yields a grand mean of 778.0 +/- 1.7 (N = 28). The new compilation shows virtually no trend in placement of the MBB within isotope Stage 19 as a function of sediment accumulation rate. We interpret this to mean that the average depth of remanence acquisition is within a few centimeters of the sediment-water interface. Separating the cores into two geographic regions (an Indo-Pacific-Caribbean [IPC] Group and an Atlantic Group) results in a significant difference in the position of the mid-point of the reversal with respect to the astronomical time scale. The data presented here suggest a difference of several thousand years between the two regions. This observation could be caused by systematic differences between the two regions in sedimentation rate within the interval of interest, systematic differences in remanence acquisition, or by genuine differences in the timing of the directional changes between the two regions.

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.

Weaver, PPE, Backman J, Baldauf J, Bloemendal J, Manivit H, Miller K, Pokras EM, Raymo ME, Tauxe L, Valet JP, Cheptow-Lusty A, Olafsson G.  1989.  Biostratigraphic synthesis: Leg 108, Eastern Equatorial Atlantic. Proceedings of the Ocean Drilling Program Scientific Results. 108:455-461.   10.2973/   Abstract

Leg 108 cored 12 sites in the eastern equatorial Atlantic and along the northwest African continental margin to investigate the late Neogene and Quaternary oceanographic and climatic history of these regions. Sediments recovered during Leg 108 provide in part a high-resolution stratigraphic record for the upper Pliocene through Holocene interval. The bio- and magnetostratigraphy are intercalibrated where possible and provide a useful chronostratigraphy for paleoceanographic studies.

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.

Tauxe, L, Kylstra N, Constable C.  1991.  Bootstrap Statistics for Paleomagnetic Data. Journal of Geophysical Research-Solid Earth and Planets. 96:11723-11740.   10.1029/91jb00572   AbstractWebsite

The power and utility of paleomagnetic analyses stem largely from the ability to quantify such parameters as the degree of rotation of a rock body, or the orientation of an anisotropy axis. Until recently, estimates for uncertainty in these paleomagnetically determined parameters derived from assumptions concerning the underlying parametric distribution functions of the data. In many geologically important situations, the commonly used parametric distribution functions fail to model the data adequately and the uncertainty estimates so obtained are unreliable. Such essentials as the test for common mean require data sets consistent with a spherically symmetric underlying distribution; their application in inappropriate circumstances can result in flawed interpretations. Moreover, the almost universally used approximation for a cone of 95% confidence for the mean of a sample drawn from a Fisher distribution is quite biased even for moderate dispersions (kappa = 25). The availability of inexpensive, powerful computers makes possible the empirical estimation of confidence regions by means of data resampling techniques such as the bootstrap. These resampling schemes replace analytical solutions with repeated simple calculations. We describe a bootstrap approach for the calculation of uncertainties for means or principal directions of paleomagnetic data. The method is tested on means of simulated Fisher distributions with known parameters and is found to be reliable for data sets with more than about 25 elements. Because a Fisher distribution is not assumed, the approach is applicable to a wide range of paleomagnetic data and can be used equally well on directions or associated virtual poles. We also illustrate bootstrap techniques for the discrimination of directions and for the fold test which enable the use of these powerful tests on the wider range of data sets commonly obtained in paleomagnetic investigations.

Pick, T, Tauxe L.  1994.  Characteristics of Magnetite in Submarine Basaltic Glass. Geophysical Journal International. 119:116-128.   10.1111/j.1365-246X.1994.tb00917.x   AbstractWebsite

We have compared the rock-magnetic characteristics of Cretaceous submarine basaltic glass (SBG) from DSDP/ODP Holes 417D, 418A, 807C and 543A to data from Holocene glasses from the East Pacific Rise. Both groups are very similar in that they contain single-domain, low-Ti magnetite as the carrier of a strong and stable remanent magnetization. The behaviour of magnetic hysteresis in SBG is, however, dominated by superparamagnetic grain-size populations. Transmission electron microscopy revealed spherically shaped grains of 10-20 nm diameter with crystal lattice properties consistent with magnetite. These grains could be responsible for the magnetic behaviour of SBG.

Schwehr, K, Tauxe L.  2003.  Characterization of soft-sediment deformation: Detection of cryptoslumps using magnetic methods. Geology. 31:203-206.   10.1130/0091-7613(2003)031<0203:cossdd>;2   AbstractWebsite

Many workers have explored anisotropy of magnetic susceptibility (AMS) of sediments as an indicator of deformation. Several studies have used deflection of the eigen-vector associated with the minimum in susceptibility, V-3, as a criterion for deformation. We examine the AMS record of a well-exposed slump and find that although demonstrable deformation can occur without deflecting the V-3 directions, an oblate AMS fabric is transformed into a triaxial fabric during initial deformation. Transformation of the fabric from oblate to triaxial appears to be highly correlated with an increase in natural remanent magnetization scatter, whereas deflection of the V-3 axes is not. We suggest that subtle soft-sediment deformation can be detected by using AMS fabric.

Tauxe, L.  1992.  Chemical Remanent Magnetization. Encyclopedia of the Earth System Science. 1:447-453. Abstract
Pick, T, Tauxe L.  1991.  Chemical Remanent Magnetization in Synthetic Magnetite. Journal of Geophysical Research-Solid Earth and Planets. 96:9925-9936.   10.1029/91jb00706   AbstractWebsite

As a magnetic grain produced by a chemical process below its blocking temperature grows through a critical volume in the presence of a magnetic field, its moment becomes blocked and it acquires a chemical remanent magnetization, CRM. Despite its importance to paleomagnetism, the properties of CRM and the controls on its behavior are still poorly understood. We have modified techniques developed by Taylor et al. [1987] to synthesize magnetite at room temperature and atmospheric pressure, whereby magnetite is produced by alteration of "green rust" under reducing conditions. The period of synthesis is twenty-four hours and a viscous component acquired over this amount of time can be demagnetized with alternating fields of 10 mT. The average direction of the CRM parallels the direction of the applied field and the intensity increases with increasing intensity of the applied field. The intensity is linearly related to the applied field up to approximately 1 mT, consistent with existing CRM theory developed by analogy to the acquisition of thermal remanent magnetization (TRM). Above about 1 mT, however, the CRM intensity approaches saturation at a rate substantially lower than that predicted by the TRM analog theory. Furthermore, the ratio of the CRM to an anhysteretic remanence acquired in the same field strongly depends on the intensity of the growth field. Analogy to TRM predicts this ratio to be independent of growth field. Both, the principal eigenvector of the anisotropy of isothermal remanence (AIR) matrix becomes more aligned with growth field and the percent anisotropy increases as the intensity of the growth field increases. The above observations suggest that the model of CRM acquisition based on analogy to TRM acquisition is incomplete. We therefore propose a revised model which incorporates the increased alignment of easy axes with growth field. Finally, the alignment of magnetic anisotropy ellipsoids of our synthetic samples with the growth field suggests a means to distinguish CRM from TRM in natural remanence.

Tauxe, L, Stickley CE, Sugisaki S, Bijl PK, Bohaty SM, Brinkhuis H, Escutia C, Flores JA, Houben AJP, Iwai M, Jimenez-Espejo F, McKay R, Passchier S, Pross J, Riesselman CR, Rohl U, Sangiorgi F, Welsh K, Klaus A, Fehr A, Bendle JAP, Dunbar R, Gonzalez J, Hayden T, Katsuki K, Olney MP, Pekar SF, Shrivastava PK, van de Flierdt T, Williams T, Yamane M.  2012.  Chronostratigraphic framework for the IODP Expedition 318 cores from the Wilkes Land Margin: Constraints for paleoceanographic reconstruction. Paleoceanography. 27   10.1029/2012pa002308   AbstractWebsite

The Integrated Ocean Drilling Program Expedition 318 to the Wilkes Land margin of Antarctica recovered a sedimentary succession ranging in age from lower Eocene to the Holocene. Excellent stratigraphic control is key to understanding the timing of paleoceanographic events through critical climate intervals. Drill sites recovered the lower and middle Eocene, nearly the entire Oligocene, the Miocene from about 17 Ma, the entire Pliocene and much of the Pleistocene. The paleomagnetic properties are generally suitable for magnetostratigraphic interpretation, with well-behaved demagnetization diagrams, uniform distribution of declinations, and a clear separation into two inclination modes. Although the sequences were discontinuously recovered with many gaps due to coring, and there are hiatuses from sedimentary and tectonic processes, the magnetostratigraphic patterns are in general readily interpretable. Our interpretations are integrated with the diatom, radiolarian, calcareous nannofossils and dinoflagellate cyst (dinocyst) biostratigraphy. The magnetostratigraphy significantly improves the resolution of the chronostratigraphy, particularly in intervals with poor biostratigraphic control. However, Southern Ocean records with reliable magnetostratigraphies are notably scarce, and the data reported here provide an opportunity for improved calibration of the biostratigraphic records. In particular, we provide a rare magnetostratigraphic calibration for dinocyst biostratigraphy in the Paleogene and a substantially improved diatom calibration for the Pliocene. This paper presents the stratigraphic framework for future paleoceanographic proxy records which are being developed for the Wilkes Land margin cores. It further provides tight constraints on the duration of regional hiatuses inferred from seismic surveys of the region.

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.

Gee, J, Staudigel H, Tauxe L.  1989.  Contribution of Induced Magnetization to Magnetization of Seamounts. Nature. 342:170-173.   10.1038/342170a0   AbstractWebsite

A fundamental assumption in modelling seamount magnetic anomalies is that the contribution of induced magnetization is negligible. The general consistency of seamount and non-seamount palaeopoles, scarcity of poles skewed toward the present field direction and the high ratio of remanent to induced magnetization (Koenigsberger ratio) of many oceanic basalts have been cited as evidence supporting this assumption1,2. Recent discussions concerning the dominance of normally magnetized seamounts have focused attention on the possible role of viscous and induced magnetization in seamount anomalies3–6. Here we determine natural remanent magnetization, initial volume susceptibility and the Koenigsberger ratio for more than 2,000 samples from a subaerially exposed seamount section on La Palma, Canary Islands (Table 1). By contrast to results from the oceanic crust and ophiolites, these data indicate that a variety of rock types are potential magnetic sources. The significant induced component of intrusives underscores the importance of the lithological distribution in determining the character of seamount magnetic anomalies. The La Palma data, together with a plausible lithological distribution, indicate that induced magnetization may account for one-sixth of seamount magnetization.

Kent, DV, Tauxe L.  2005.  Corrected Late Triassic latitudes for continents adjacent to the North Atlantic. Science. 307:240-244.   10.1126/science.1105826   AbstractWebsite

We use a method based on a statistical geomagnetic field model to recognize and correct for inclination error in sedimentary rocks from early Mesozoic rift basins in North America, Greenland, and Europe. The congruence of the corrected sedimentary results and independent data from igneous rocks on a regional scale indicates that a geocentric axial dipole field operated in the Late Triassic. The corrected paleolatitudes indicate a faster poleward drift of similar to0.6 degrees per million years for this part of Pangea and suggest that the equatorial humid belt in the Late Triassic was about as wide as it is today.

Roberts, AP, Tauxe L, Heslop D, Zhao X, Jiang ZX.  2018.  A critical appraisal of the "Day" diagram. Journal of Geophysical Research-Solid Earth. 123:2618-2644.   10.1002/2017jb015247   AbstractWebsite

The Day diagram (Day et al., 1977, ) is used widely to make inferences about the domain state of magnetic mineral assemblages. Based on theoretical and empirical arguments, the Day diagram is demarcated into stable single domain (SD), pseudo single domain (PSD), and multidomain (MD) zones. It is straightforward to make the necessary measurements for a sample and to plot results within the domain state framework based on the boundaries defined by Day et al. (1977, ). We discuss 10 issues that limit Day diagram interpretation, including (1) magnetic mineralogy, (2) the associated magnetocrystalline anisotropy type, (3) mineral stoichiometry, (4) stress state, (5) surface oxidation, (6) magnetostatic interactions, (7) particle shape, (8) thermal relaxation, (9) magnetic particle mixtures, and (10) definitional/measurement issues. In most studies, these variables are unknowns and cannot be controlled for, so that hysteresis parameters for single bulk samples are nonunique and any data point in a Day diagram could result from infinite combinations of relevant variables. From this critical appraisal, we argue that the Day diagram is fundamentally ambiguous for domain state diagnosis. Widespread use of the Day diagram has also contributed significantly to prevalent but questionable views, including underrecognition of the importance of stable SD particles in the geological record and reinforcement of the unhelpful PSD concept and of its geological importance. Adoption of approaches that enable correct domain state diagnosis should be an urgent priority for component-specific understanding of magnetic mineral assemblages and for quantitative rock magnetic interpretation.

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
Shaar, R, Tauxe L, Ben-Yosef E, Kassianidou V, B. L, Feinberg J, Levy T.  2015.  Decadal-scale variations in geomagnetic field intensity from ancient Cypriot slag mounds. Geochemistry, Geophysics, Geosystems. 16   10.1002/2014GC005455  
Tauxe, L, Steindorf JL, Harris A.  2006.  Depositional remanent magnetization: Toward an improved theoretical and experimental foundation. Earth and Planetary Science Letters. 244:515-529.   10.1016/j.cpsl.2006.02.003   AbstractWebsite

The first theoretical predictions for the behavior of magnetic particles in water were that sedimentary magnetizations would be fully aligned with the ambient field, yet redeposition experiments showed a strong (and quasi-linear) dependence on the external field. This empirically observed linearity has served as the fundamental assumption of sedimentary paleointensity studies for decades. We present redeposition experiments which suggest instead that the relationship between depositional remanence (DRM) and applied field may frequently be curved for magnetic fields in the range of the Earth's. Numerical simulations using a flocculation model can explain the redeposition data and suggest that DRM will be significantly non-linear when the floes are small (several microns). There is a strong dependence of floe size on salinity particularly in low salinity environments. Floe size has a profound influence on the efficiency of DRM, hence low salinity environment may give results with poor reproducibility. The size of the floe in which magnetic particles are embedded is not accounted for in current methods of normalization, yet is the most important parameter. On the bright side, however, it now seems possible to quantitatively explain paleointensity in sedimentary systems opening the door to absolute paleointensity estimates from sediments whose key parameters of floe size distribution and settling times can be constrained. (c) 2006 Elsevier B.V All fights reserved.

Schwehr, K, Tauxe L, Driscoll N, Lee H.  2006.  Detecting compaction disequilibrium with anisotropy of magnetic susceptibility. Geochemistry Geophysics Geosystems. 7   10.1029/2006gc001378   AbstractWebsite

In clay-rich sediment, microstructures and macrostructures influence how sediments deform when under stress. When lithology is fairly constant, anisotropy of magnetic susceptibility (AMS) can be a simple technique for measuring the relative consolidation state of sediment, which reflects the sediment burial history. AMS can reveal areas of high water content and apparent overconsolidation associated with unconformities where sediment overburden has been removed. Many other methods for testing consolidation and water content are destructive and invasive, whereas AMS provides a nondestructive means to focus on areas for additional geotechnical study. In zones where the magnetic minerals are undergoing diagenesis, AMS should not be used for detecting compaction state. By utilizing AMS in the Santa Barbara Basin, we were able to identify one clear unconformity and eight zones of high water content in three cores. With the addition of susceptibility, anhysteretic remanent magnetization, and isothermal remanent magnetization rock magnetic techniques, we excluded 3 out of 11 zones from being compaction disequilibria. The AMS signals for these three zones are the result of diagenesis, coring deformation, and burrows. In addition, using AMS eigenvectors, we are able to accurately show the direction of maximum compression for the accumulation zone of the Gaviota Slide.

Mitra, R, Tauxe L, Gee JS.  2011.  Detecting uniaxial single domain grains with a modified IRM technique. Geophysical Journal International. 187:1250-1258.   10.1111/j.1365-246X.2011.05224.x   AbstractWebsite

Mid-ocean ridge basalt (MORB) specimens have often been found to have high ratios of saturation remanence to saturation magnetization (M(rs)/M(s)). This has been attributed either to dominant cubic anisotropy or to insufficient saturating field leading to overestimation of M(rs)/M(s) of a dominantly uniaxial single domain (USD) assemblage. To resolve this debate, we develop an independent technique to detect USD assemblages. The experimental protocol involves subjecting the specimen to bidirectional impulse fields at each step. The experiment is similar to the conventional isothermal remanent magnetization (IRM) acquisition experiment but the field is applied twice, in antiparallel directions. We define a new parameter, IRAT, as the ratio of the remanences at each field step and show it to have characteristic behaviour for the two assemblages; IRAT similar to 1 at all field steps for USD and <1 with a strong field dependence for multi-axial single domain (MSD) grains. We verified the theoretical predictions experimentally with representative USD and MSD specimens. Experiments with MORBs gave low IRATs for specimens having high M(rs)/M(s). This argues for a dominant MSD assemblage in the MORBs, possibly cubic in nature. Although undersaturation of the samples can indeed be a contributing factor to the exceptionally high M(rs)/M(s), this study shows that the nature of the assemblage cannot be dominantly USD.

Varga, RJ, Gee JS, Staudigel H, Tauxe L.  1998.  Dike surface lineations as magma flow indicators within the sheeted dike complex of the Troodos Ophiolite, Cyprus. Journal of Geophysical Research-Solid Earth. 103:5241-5256.   10.1029/97jb02717   AbstractWebsite

Mesoscopic flow lineations and anisotropy of magnetic susceptibility (AMS) have been measured for dikes within the Cretaceous-age Troodos ophiolite with the goal of comparing the direction of initial magma now through dike conduits immediately following crack propagation with that of flow of subsequent magma emplaced during later stages of dike growth. Dike margin indicators of flow include cusp axes and elongate vesicles found high in the ophiolite peudostratigraphy and ridge-and-groove structures termed hot slickenlines found throughout the complex. A unique now direction is determined where elongate vesicles near dike margins display imbrication with respect to the margin. Significant changes in vesicle elongation directions across dikes likely indicate either changes in magma flow direction after dike propagation or backflow of magma during the waning stages of intrusion. Surface lineations generally lie subparallel to the direction of flow inferred from AMS determinations on cores within 5 cm of dike margins. Surface lineations also lie subparallel to the long axis (epsilon(1)) of the orientation ellipsoid defined by long axes of groundmass plagioclase phenocrysts measured in sections from AMS cores. Correlation of surface lineations with interior indicators of flow (AMS, plagioclase trachytic texture) indicate that the surface features are good proxies for grain-scale magma flow directions during dike propagation in Troodos dikes. Orientations of surface flow features in the dikes of the Troodos ophiolite indicate an approximately equal mix of subhorizontal to near-vertical magma flow, contradicting the paradigm of primarily vertical flow of magma beneath continuous axial magma chambers at oceanic spreading centers. Our data are consistent with a model of magma emplacement both vertically and horizontally away from isolated magma chambers beneath axial volcanoes spaced along a ridge crest.

Tucker, P, Tauxe L.  1984.  The Downhole Variation of the Rock-Magnetic Properties of Leg-73 Sediments. Initial Reports of the Deep Sea Drilling Project. 73:673-685. AbstractWebsite
Labrecque, JL, Hsu KJ, Carman MF, Karpoff AM, McKenzie JA, Percival SF, Petersen NP, Pisciotto KA, Schreiber E, Tauxe L, Tucker P, Weissert HJ, Wright R.  1983.  DSDP Leg-73: Contributions to Paleogene Stratigraphy in Nomenclature, Chronology and Sedimentation-Rates. Palaeogeography Palaeoclimatology Palaeoecology. 42:91-&.   10.1016/0031-0182(83)90040-8   AbstractWebsite

DSDP Leg 73 was successful in determining magnetostratigraphic—biostratigraphic correlations throughout much of the Paleogene. This paper treats three aspects of the data analysis.The first section treats the development of a chron nomenclature which facilitates the precise correlation of arbitrary events with respect to the geomagnetic polarity history.The second section analyzes the accuracy of radiometric dates for the Paleogene. The conclusion is that despite the recent advances in radiochronology ‘South Atlantic Standard’ remains the most convenient and probably the most reliable chronological standard.The final section studies the correlation in sedimentation rates between the Umbrian and South Atlantic sites. The conclusion is that sedimentation rate changes determined from magnetostratigraphy provide a high-resolution source of paleoenvironmental information. Strong correlations are noted between sites and with respect to other paleo-environmental studies involving oxygen isotope ratios, biogeography and CCD fluctuations within the Paleogene marine sediments.

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.

Krijgsman, W, Tauxe L.  2006.  E/I corrected paleolatitudes for the sedimentary rocks of the Baja British Columbia hypothesis. Earth and Planetary Science Letters. 242:205-216.   10.1016/j.epsl.2005.11.052   AbstractWebsite

Paleomagnetic inclinations from sediments of the western terranes of Canada are consistently too shallow for their reconstructed paleogeographic positions. Two contradicting explanations for these discrepancies are: (1) terranes have been displaced northward with respect to the stable American craton by several thousands of kilometres between the Late Cretaceous (similar to 75 Ma) and the Eocene (similar to 50 Ma) and (2) sedimentary inclination error has caused a shallow bias in the paleomagnetic directions. Here, we apply the elongation/inclination (E/I) method to paleomagnetie data sets from sedimentary rocks of supposedly allochtonous terranes of Nvestem North America to correct for inclination flattening. Our results indicate that the paleomagnetic directions from the continental Silverquick sediments (95-92 Ma) of southern British Colombia are not seriously affected by inclination error, because the magnetic signal most likely concerns a chemical remanent magnetisation (CRM). In contrast, the marine sediments of the Nanaimo Group (84-72 Ma) of Vancouver Island region appear seriously affected by inclination flattening (f=0.7) and the EA corrected mean inclinations are about 9 degrees steeper than the original data. We arrive at corrected inclinations/paleolatitudes of I** = 57 degrees/lambda = 38 degrees N for the Silverquick and I** = 55 degrees/lambda = 36 degrees N for the Nanaimo sediments. Our corrected paleolatitudes indicate that the Canadian terranes were indeed located adjacent to the Baja Californian margin during the Late Cretaceous, thus supporting the Baja BC hypothesis. (c) 2005 Elsevier B.V. All rights reserved.