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Tauxe, L.  1979.  New Date for Ramapithecus. Nature. 282:399-401.   10.1038/282399a0   AbstractWebsite

Recent work in the Middle Siwalik rocks of the Potwar Plateau in northern Pakistan is doing much to further our understanding of Miocene mammalian evolution, in particular the evolution of Ramapithecus and Sivapithecus, hominoids considered important for human ancestry1. It is crucial to the understanding of hominoid evolution to place the fossils in as precise a chronologic framework as possible. As there is a lack of material suitable for radiometric dating, it is necessary to rely on the correlation of the magnetic stratigraphy associated with the Siwalik faunas to the calibrated magnetic polarity tune scale (MPTS). Initial age estimates by Barndt et al. 2 were based on reconnaissance level palaeomagnetic sampling. The more detailed sampling presented here suggests a revised correlation of the local magnetic stratigraphy to the time scale and hence a revised age estimate for Ramapithecus: 8 Myr now seems more likely than the previous estimate of 9 Myr.

Tauxe, L, Kent DV, Opdyke ND.  1980.  Magnetic Components Contributing to the NRM of Middle Siwalik Red Beds. Earth and Planetary Science Letters. 47:279-284.   10.1016/0012-821x(80)90044-8   AbstractWebsite

The components of the NRM in Middle Siwalik red beds are carried by two phases of hematite, a red pigment phase and a specular hematite phase. We present evidence in the form of a conglomerate test that the specularite phase carries a remanence acquired during or shortly after deposition. The red pigment, however, post-dates deposition, in many cases by at least one reversal boundary. This secondary component has a higher coercivity but a lower blocking temperature in these rocks and can therefore be selectively removed by thermal demagnetization to reveal a primary magnetization useful for magnetostratigraphic studies.

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.

Poore, RZ, Tauxe L, Percival SF, Labrecque JL.  1982.  Late Eocene-Oligocene Magnetostratigraphy and Biostratigraphy at South-Atlantic Dsdp Site 522. Geology. 10:508-511.   10.1130/0091-7613(1982)10<508:lemaba>;2   AbstractWebsite

Upper Eocene to lowest Miocene sediments recovered at Deep Sea Drilling Project (DSDP) Site 522 in the South Atlantic Ocean allow direct calibration of magnetostratigraphy and calcareous plankton biostratigraphy. The results from Site 522 show that the Eocene/Oligocene boundary occurs in the reversed interval of magnetic Chron C13 (= C13R) and that the Oligocene/IMiocene boundary probably occurs in the upper part of Chron C6C.

Hsu, KJ, He Q, McKenzie JA, Weissert H, Perchnielsen K, Oberhansli H, Kelts K, Labrecque J, Tauxe L, Krahenbuhl U, Percival SF, Wright R, Karpoff AM, Petersen N, Tucker P, Poore RZ, Gombos AM, Pisciotto K, Carman MF, Schreiber E.  1982.  Mass Mortality and Its Environmental and Evolutionary Consequences. Science. 216:249-256.   10.1126/science.216.4543.249   AbstractWebsite

The latest Mesozoic and earliest Tertiary sediments at Deep Sea Drilling Project site 524 provide an amplified record of environmental and biostratographic changes at the end of Cretaceous. Closely spaced samples, representing time intervals as short as 10^2 or 10^3 years, were analyzed for their bulk carbonate and trace-metal compositions, and for oxygen and carbon isotopic compositions. The data indicate that at the end of Cretaceous, when a high proportion of the ocean's planktic organisms were eliminated, an associated reduction in productivity led to a partial transfer of dissolved carbon dioxide from the oceans to the atmosphere. This resulted in a large increase of the atmospheric carbon dioxide during the next 50,000 years, which is believed to have caused a temperature rise revealed by the oxygen-isotope data. The lowermost Tertiary sediments at site 524 include fossils with Cretaceous affinities, which may include both reworked individuals and some forms that survived for a while after the catastrophe. Our data indicate that many of the Cretaceous pelagic organisms became extinct over a period of a few tens of thousands of years, and do not contradict the scenario of cometary impact as a cause of mass mortality in the oceans, as suggested by an iridium anomaly at the Cretaceous-Tertiary boundary.

Tauxe, L, Opdyke ND.  1982.  A Time Framework Based on Magnetostratigraphy for the Siwalik Sediments of the Khaur Area, Northern Pakistan. Palaeogeography Palaeoclimatology Palaeoecology. 37:43-61.   10.1016/0031-0182(82)90057-8   AbstractWebsite

The magnetostratigraphy of eleven new sections in the Khaur area of northern Pakistan is presented. All specimens have been subjected to thermal demagnetization. The sections, taken in adjacent ravines incising the Siwalik formations nearly penpendicular to strike, form a temporal framework in which to interpret the biological and lithological information. A composite section is constructed from several long sections and is correlated to the magnetic polarity time scale (Chron 6 to Chron 15), providing absolute age information for the biostratigraphic zonations of Barry et al. (1982). Detailed sections along the strike of major stratigraphic marker beds document an isochronous horizon and form the basis for paleoenvironmental reconstructions. The preservation of a polarity transition in fluvial sediments suggests continuity of sedimentation on a time scale of 103–104 years.

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.

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.

Poore, RZ, Tauxe L, Percival SF, Labrecque JL, Wright R, Petersen NP, Smith CC, Tucker P, Hsu KJ.  1983.  Late Cretaceous Cenozoic Magnetostratigraphic and Biostratigraphic Correlations of the South-Atlantic Ocean - DSDP Leg-73. Palaeogeography Palaeoclimatology Palaeoecology. 42:127-&.   10.1016/0031-0182(83)90041-x   AbstractWebsite

DSDP Leg 73 sediment cores allow direct calibrations of magnetostratigraphy and biostratigraphy for much of the latest Cretaceous to Cenozoic in the mid-latitude South Atlantic Ocean. A complete record of the Cenozoic was not obtained, however, because strong dissolution, poor core recovery and intense core disturbance have masked the biostratigraphy or magnetostratigraphy over some intervals of all recovered sections. DSDP Leg 73 results are given.

Tauxe, L, Tucker P, Petersen NP, Labrecque JL.  1983.  The Magnetostratigraphy of Leg-73 Sediments. Palaeogeography Palaeoclimatology Palaeoecology. 42:65-90.   10.1016/0031-0182(83)90039-1   AbstractWebsite

The main objectiveof DSDP Leg 73 was to obtain high-quality records of major paleooceanographic events in the South Atlantic. This was achieved by coringsix sites on the African plate. The sediments thus recovered span the Cenozoic and five of the six sites proved ideally suited for magnetostratigraphic analysis. The results presented in this paper and elsewhere in this volume constitute the first opportunity to extend the direct correlation of the magnetostratigraphic and biostratigraphic time-scales into the Paleogene in deep-sea cores.The magnetostratigraphic analyses from DSDP Leg 73 sediments are presented in this paper. The correlation of the magnetostratigraphy to the magnetic polarity time-scale provides tight age—depth control for the five sites analyzed, allowing the accurate calculation of sediment accumulation rates.The data presented here represent a remarkable record of the fine-scale polarity history of the Earth's magnetic field. These data place constraints on the interpretation of small-scale marine magnetic anomalies which are modelled equally effectively by field intensity fluctuations as polarity reversals. At least some of the “tiny wiggles” correspond to very short polarity units in the magnetostratigraphic record.By assuming an axial geocentric dipole, the inclination of the time-averaged magnetic field recorded in the sediments can be used to calculate the paleolatitude at which the sediments were deposited. Combining the age and average inclination information available from the magnetostratigraphy, we present paleolatitudes versus time for the Leg 73 drill sites.

Tauxe, L, Besse J, Labrecque JL.  1983.  Paleolatitudes from DSDP Leg-73 Sediment Cores - Implications for the Apparent Polar Wander Path for Africa During the Late Mesozoic and Cenozoic. Geophysical Journal of the Royal Astronomical Society. 73:315-324.   10.1111/j.1365-246X.1983.tb03318.x   AbstractWebsite

Palaeolatitudes estimated from DSDP sediments provide important constraints on the apparent polar wander path (APWP) of Africa during the Cenozoic. A revised APWP is suggested based on new information about palaeomagnetic poles from the African continent and predicted palaeolatitudes are compared with those determined from Leg 73 sediments. Other published paths are discussed.

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.

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
Poore, RZ, Tauxe L, Percival SF, Labrecque JL, Wright R, Petersen NP, Smith CC, Tucker P, Hsu KJ.  1984.  Late Cretaceous Cenozoic Magnetostratigraphic and Biostratigraphic Correlations for the South-Atlantic Ocean, Deep-Sea Drilling Project Leg-73. Initial Reports of the Deep Sea Drilling Project. 73:645-655. AbstractWebsite
Tauxe, L, Tucker P, Petersen NP, Labrecque JL.  1984.  Magnetostratigraphy of Leg-73 Sediments. Initial Reports of the Deep Sea Drilling Project. 73:609-621. AbstractWebsite
Tauxe, L, Kent DV.  1984.  Properties of a Detrital Remanence Carried by Hematite from Study of Modern River Deposits and Laboratory Redeposition Experiments. Geophysical Journal of the Royal Astronomical Society. 76:543-561.   10.1111/j.1365-246X.1984.tb01909.x   AbstractWebsite

Although detrital haematite is often observed in red sedimentary rocks, its contribution to the magnetization is usually a matter of debate. Part of the problem is that the properties of magnetic remanence carried by detrital haematite are not well known. Studies on both naturally and experimentally deposited modern river sediments whose remanence is carried by detrital haematite lead to the following observations:(1) The declinations of river-laid sediments deposited under known field conditions average to that of the Earth's field.(2) A substantial inclination error is observed in both river-laid and experimentally deposited sediments which varies as: tan (Io) =f. tan (If) where Io and If are the remanent and applied inclinations respectively and f is about 0.55 in these experiments.(3) The intensity of remanence is a function of both the magnitude and the orientation of the applied magnetic field, increasing with field strength and decreasing with field inclination. This observation is consistent with models involving contributions to the remanence by plates (constrained to lie nearly horizontally) and spheres (aligned with the applied field).(4) Sediments deposited in zero field and then subjected to an applied field acquired a p-DRM by grain rotation. The intensity of p-DRM increased with time according to a power law, P-DRM is acquired parallel to the applied field but, unless the sediment is disturbed, has an intensity an order of magnitude lower than the DRM acquired in the same field.(5) If generally valid, the inclination error for a haematite DRM presents the paradox that while both the age and the polarity of the DRM may be determined, the direction of the DRM magnetization will tend to underestimate palaeolatitude and give palaeopole positions that are far-sided.

Tauxe, L, Badgley C.  1984.  Transition Stratigraphy and the Problem of Remanence Lock-in Times in the Siwalik Red Beds. Geophysical Research Letters. 11:611-613.   10.1029/GL011i006p00611   AbstractWebsite

The record of paleomagnetic polarity transitions can provide relative time information in the stratigraphic record on scales of hundreds to thousands of years. Transition stratigraphy is here used to determine the relative lock-in times of several components of magnetization in the Siwalik red beds.

Johnson, NM, Stix J, Tauxe L, Cerveny PF, Tahirkheli RAK.  1985.  Paleomagnetic Chronology, Fluvial Processes, and Tectonic Implications of the Siwalik Deposits near Chinji Village, Pakistan. Journal of Geology. 93:27-40. AbstractWebsite
Tauxe, L, Monaghan M, Drake R, Curtis G, Staudigel H.  1985.  Paleomagnetism of Miocene East African Rift sediments and the calibration of the geomagnetic reversal time scale. Journal of Geophysical Research. 90:4639-4646., Washington, DC, United States (USA): American Geophysical Union, Washington, DC   10.1029/JB090iB06p04639   AbstractWebsite

Paleomagnetic stratigraphy and K-Ar age determinations are reported for the type section of the middle Miocene Ngorora Formation, found in the Kenya rift valley. The magnetostratigraphy is well correlated to the geomagnetic reversal time scale (GRTS) and spans from the lower part of Chron C5 (9) to Chron C5AB-r (14). K-Ar dates were determined for euhedral sanidines, handpicked from seven tuff horizons within the Ngorora Formation and the underlying Turn phonolite flow. These dates can therefore be tied directly to the GRTS. The eight dates fall into three discrete groups averaging 12.5 + or - 0.22 Ma (mean and standard deviation of results from four tuffs), 11.6 + or - 0.06 Ma (mean and standard deviation from three tuffs), and 10.16 + or - 0.38 (average of three analyses from one tuff). We interpret the age groups as resulting from three successive eruptive episodes, the stratigraphic positions of which are well constrained. In spite of episodic supply at the eruptive source, sediment accumulation is continuous at the resolution of the GRTS. This suggests that accumulation is controlled by basin subsidence rather than sediment supply. Sanidine dates support an age for the older boundary of marine magnetic anomaly 5 of about 10 Ma, as opposed to 11.12 Ma, suggested by the most recent results from Icelandic basaltic lava flows.

Hill, A, Drake R, Tauxe L, Monaghan M, Barry JC, Behrensmeyer AK, Curtis G, Jacobs BF, Jacobs L, Johnson N, Pilbeam D.  1985.  Neogene Paleontology and Geochronology of the Baringo Basin, Kenya. Journal of Human Evolution. 14:759-773.   10.1016/s0047-2484(85)80058-0   AbstractWebsite

The period from 14 to four million years is poorly known in Africa, but during this time the Ethiopian fauna became established and hominids originated. The sedimentary sequence of the Tugen Hills in the Baringo area of Kenya provides important geological, environmental and plaeontological data concerning this interval. Concordant radiometric and palaeomagnetic determinations within the type section of the Ngorora Formation show that it spans more than 2 m.y., from 13 m.y.a. to less than 10 m.y.a., and from chrons 14 to 9. Other dates refine the calibration of the Younger Mpcsida, Lukeino and Chemeron units. Palaeontological results include the collection from the Ngorora Formation of one of the best Neogene macrofloras in Africa, and more fauna, including hominoids. No equids have been recorded older than 10 m.y.a. We also report new fauna from the more recent units.

Ruddiman, W, Sarnthein M, Baldauf J, Backman J, Bloemendal J, Curry W, Farrimond P, Faugeres J C, Janecek T, Katsura Y, Manivit H, Mazzullo J, Mienert J, Pokras EM, Raymo M, Schultheiss P, Stein R, Tauxe L, Valet JP, Weaver PP, Yasuda H.  1986.  Ocean Drilling Program; palaeoclimatic linkage between high and low latitudes. Nature (London). 322:211-212., London, United Kingdom (GBR): Macmillan Journals, London AbstractWebsite
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.

Ruddiman, W, Sarnthein M, Backman J, Baldauf J, Bloemendal J, Curry W, Farrimond P, Faugeres JC, Janecek T, Katsura Y, Manivit H, Mazzulo J, Mienert J, Pokras E, Raymo M, Schultheiss P, Stein R, Tauxe L, Valet JP, Weaver P, Yasuda H.  1986.  Neogene Paleocirculation and Paleoclimate Record of ODP Leg 108 (Tropical and Subtropical East Atlantic). Comptes Rendus De L Academie Des Sciences Serie Ii. 303:1581-&. AbstractWebsite
Mead, GA, Tauxe L, Labrecque JL.  1986.  Oligocene Paleoceanography of the South Atlantic: Paleoclimatic Implications of Sediment Accumulation Rates and Magnetic Susceptibility Measurements. Paleoceanography. 1:273-284.   10.1029/PA001i003p00273   AbstractWebsite

Paleoceanographic changes during the Oligocene in the South Atlantic have been examined using paleomagnetic, rock magnetic, carbonate content, and sediment accumulation rate (SAR) data. We show that magnetic susceptibility(M S) is largely controlled by carbonate content at Deep-Sea Drilling Project site 522, which in turn is the primary control on SAR at the site. Over 5000 MS measurements were averaged over magnetostratigraphic polarity intervals for use as indicators of carbonate content and SAR proxies. The study produced three primary results:(1) a spectral analysis of the MS data from one upper Oligocene core reveals two dominant periodicities (44.7 +/- 10.4 kyr and 26.4 +/- 3.6 kyr) which approximate Milankovitch obliquity(41 kyr) and precession(2 3 kyr) periods;(2) four pulses of increased SAR lasting 1 to 2 m.y. punctuate the section, implying longer-term climatic changes (these events are also seen in the Contessa quarry section of the Italian (Tethyan) Oligocene); and (3) two of the SAR maxima correspond to times of global cooling and possible ice volume increases, at 31 and 36 Ma.

Tauxe, L, Clark DR.  1987.  New Paleomagnetic Results from the Eureka Sound Group - Implications for the Age of Early Tertiary Arctic Biota. Geological Society of America Bulletin. 99:739-747.   10.1130/0016-7606(1987)99<739:nprfte>;2   AbstractWebsite

Some 300 specimens from 101 sites were analyzed from sections spanning more than 2,000 m of lignitic carbonate and clastic rocks. The sediments belong to the lower Tertiary Eureka Sound Group and are exposed near Bay and Strathcona Fiords on Ellesmere Island. Paleomagnetic analysis suggests that remanence is carried by magnetite, and positive fold and reversals tests support an early (detrital or early post-depositional) acquisition of the characteristic magnetization. We correlate the local magnetostratigraphy to Chrons C25 and C26 of the time scale. Comparison of the magnetostratigraphic results obtained here with results from Paleocene/Eocene sections from Wyoming and Texas do not support a significant temporal discrepancy of faunal and floral assemblages between the Arctic and the southwestern United States.

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.

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.

Tauxe, L, Butler R, Herguera JC.  1987.  Magnetostratigraphy - in Pursuit of Missing Links. Reviews of Geophysics. 25:939-950.   10.1029/RG025i005p00939   AbstractWebsite

Since the last quadrennial report, magneto-stratigraphy has continued to flourish. The primary issues have been (1) refinements to the geomagnetic reversal time scale (GRTS) including recalibrations, correlation of biostratigraphic data to the CRTS and revision of the terminology, (2) use of magnetostratigraphic data for estimating rates of such processes as sediment accumulation, evolution and faunal migration, and (3) magnetic mineralogy and the origin of remanence. For convenience, we have divided the publications into studies of continental and marine sediments and highlight the most exciting issues within each of these sub-headings. In the first section of this review, we will concentrate on the development of the geomagnetic reversal time scale (GRTS), with particular emphasis on refinements from the last few years. We then turn our attention to applications of magnetostratigraphy in marine and continental sequences.

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/  
Tauxe, L, Badgley C.  1988.  Stratigraphy and Remanence Acquisition of a Paleomagnetic Reversal in Alluvial Siwalik Rocks of Pakistan. Sedimentology. 35:697-715.   10.1111/j.1365-3091.1988.tb01245.x   AbstractWebsite

A high-resolution record of a palaeomagnetic reversal is documented in Miocene alluvial rocks of Pakistan. We examined lateral variability of lithostratigraphy and palaeomagnetic stratigraphy through the same palaeomagnetic reversal in six correlated sections. Each section contains one or more palaeomagnetic sites with directions between fully reversed and fully normal. The position of the reversal illustrates local relief in the study area and the time-transgressive nature of certain stratigraphic units. Variability in the thickness of the transitional interval indicates contemporaneous variability in sediment accumulation rates.Different characteristics of palaeomagnetic remanence are associated with the depositional and post-depositional history of these sediments. Variability in patterns of remanence behaviour is the basis for inferences about post-depositional processes. We discuss two magnetic parameters that express coherency of palaeomagnetic samples—the maximum angle of deviation and the circular standard deviation. Of particular interest are samples with incoherent palaeomagnetic signals. The incoherency of samples is inversely correlated with the thickness of the transitional interval. A low rate of sediment accumulation, suggested by a thin transitional interval, may facilitate a prolonged period of remagnetization through pedogenic or hydrological processes. Alternatively, transition intervals, denned by coherent magnetization, may be thin as a result of pedogenically induced incoherency.

Valet, JP, Tauxe L, Clark DR.  1988.  The Matuyama-Brunhes Transition Recorded from Lake Tecopa Sediments (California). Earth and Planetary Science Letters. 87:463-472.   10.1016/0012-821x(88)90009-x   AbstractWebsite

The paleomagnetic record of the Matuyama-Brunhes reversal in the sediment of ancient lake Tecopa provided the first evidence that the geomagnetic field during transition is not dipolar.We resampled the section to increase the time resolution of the record. Our new data show that the characteristic direction could not be completely isolated by AF demagnetization. The transitional directions obtained from thermal demagnetization are thus quite different from those of the previous study but the primary conclusion that the field was non-dipolar remains. The VGP paths lying close to the site longitude is consistent with an axisymmetric transition field.

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.

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.

Tauxe, L.  1989.  Magnetostratigraphy. The Encyclopedia of Solid Earth Geophysics. ( Jones DE, Ed.).:740-746. Abstract
Tauxe, L, Valet JP, Bloemendal J.  1989.  The magnetostratigraphy of Leg 108 APC cores. Proceedings of the Ocean Drilling Program Scientific Results. 108:429-439.   10.2973/   Abstract

This paper presents the magnetostratigraphic results from Leg 108 of the Ocean Drilling Program. Measurements made with the shipboard "pass-through" cryogenic magnetometer on whole cores and archive halves are combined with those made on discrete samples; these measurements constitute the paleomagnetic data base for the Leg 108 cores. Polarity determination on unoriented, low-latitude cores is somewhat subjective; we rely heavily on the available biostratigraphic data and document our line of reasoning where appropriate. The interpretations presented here, therefore, are compatible with the available biostratigraphic information; they are also in substantial agreement with orientation information where available.

Valet, JP, Tauxe L, Bloemendal J.  1989.  The Matuyama-Brunhes geomagnetic reversal from two deep-sea cores of the Eastern Equatorial Atlantic . Proceedings of the Ocean Drilling Program Scientific Results. 108:441-452.   10.2973/   Abstract

Matuyama-Brunhes geomagnetic polarity transitions recorded in Holes 659C and 664D, cored with the hydraulic piston corer during Ocean Drilling Program Leg 108, were selected for detailed study. The sections containing the reversals, as identified by shipboard results, were sampled using "U" channels. Few intermediate polarity directions were obtained from Hole 659C; consequently, no interpretation of this record in terms of transitional field behavior was attempted. However, the record from Hole 664D, located at the equator, is characterized by a gradual easterly progression of the declination from reverse to normal polarity and no deviation of the inclination from a mean value of 0°. The field intensity was reduced to about 20% of its pretransitional value. The absence of inclination changes combined with easterly declinations constrains the Virtual Geomagnetic Pole path to lie along the meridian 90° to the east. Such behavior does not resemble transitional field models, which neglect nonzonal terms. A comparison of this record with other reliable records shows that the behavior of the geomagnetic field during this reversal cannot be explained by a model involving a simple field geometry.

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.

Tauxe, L, Valet JP.  1989.  Relative Paleointensity of the Earths Magnetic-Field from Marine Sedimentary Records - a Global Perspective. Physics of the Earth and Planetary Interiors. 56:59-68.   10.1016/0031-9201(89)90036-8   AbstractWebsite

To assess the potential of marine sediments as a source of relative paleointensity information, we have undertaken an investigation of selected box cores stored in the Scripps core repository. We present here new results from two North Atlantic box cores. Magnetic remanence in the sediments is carried by magnetite and is univectorial during alternating field and thermal demagnetization. The median destructive field is 25–30 mT. Normalization by anhysteretic remanent magnetization yields relative paleointensity data that are highly concordant within and between cores. Age control provided by oxygen isotope data from both cores allows comparison of these relative paleointensity data with contemporaneous archeomagnetic data from Czechoslavakia. Both data sets indicate a peak in paleofield intensity at around 8–10 ka. This peak is less prominent in box core data from the western Pacific and global averages of archeomagnetic and lava flow data. However, the peak is evident in data estimating changes in production of radiocarbon, which is controlled in part by changes in the dipole moment of the geomagnetic field. The excellent agreement between production variations predicted by the changes in dipole moment and those observed suggests that long-term variations in atmospheric radiocarbon are dominated by geomagnetic field variations.

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.

Valet, JP, Tauxe L, Clement B.  1989.  Equatorial and Mid-Latitude Records of the Last Geomagnetic Reversal from the Atlantic-Ocean. Earth and Planetary Science Letters. 94:371-384.   10.1016/0012-821x(89)90154-4   AbstractWebsite

Three records of the Matuyama-Brunhes reversal have been obtained from ODP deep-sea cores distributed along the West African margin in the Atlantic Ocean. These studies in addition to the record from DSDP Site 609B provide a latitudinal transect extending from the equator to 50°N. Simulations of natural smoothing by post-depositional processes show that characteristic features of a transitional field geometry dominated by axisymmetry should be preserved in the records, especially at the equator. The results do not seem to favour the hypothesis that axisymmetrical terms would dominate during this transition.

Tauxe, L, Constable C, Stokking L, Badgley C.  1990.  Use of Anisotropy to Determine the Origin of Characteristic Remanence in the Siwalik Red Beds of Northern Pakistan. Journal of Geophysical Research-Solid Earth and Planets. 95:4391-4404.   10.1029/JB095iB04p04391   AbstractWebsite

It is often difficult or impossible to determine the origin of the characteristic remanent magnetization of red beds from the bulk remanence alone. However, anisotropy of remanence or susceptibility is strongly controlled by the statistical alignment of hematite grains; this in turn may reflect the development of the magnetic fabric of the sediment over time, so the shape of the anisotropy ellipsoid may provide clues to the origin of remanence. In this work, we make a study of the anisotropy of magnetic susceptibility (AMS) in Siwalik red beds of Miocene age from northern Pakistan. Comparison of the results with detailed petrographic studies and other information suggests that advanced soil development leads to the destruction of primary fabrics and often with it, a coherent magnetization. Furthermore, it should be possible to use AMS fabric information to quantify the degree of pedogenesis in these Miocene soils. We attempted to determine the anisotropy of isothermal remanence (AIR) but found AMS to be the technique of choice because of apparent changes in coercivity during AIR experiments. We interpret the AIR data as resulting from metastable domains in hematite grains which change domain state during the AIR experiment.

Tauxe, L, Wu GP.  1990.  Normalized Remanence in Sediments of the Western Equatorial Pacific - Relative Paleointensity of the Geomagnetic-Field. Journal of Geophysical Research-Solid Earth and Planets. 95:12337-12350.   10.1029/JB095iB08p12337   AbstractWebsite

Piston cores from the Ontong-Java Plateau collected during the Eurydice expedition have been used to estimate regional geomagnetic paleointensity. Rock magnetic measurements of the sediments show that (1) the remanence is carried by stable pseudo-single domain magnetite, (2) the grain sizes and concentrations are relatively uniform with respect to the normalization technique and (3) susceptibility is an adequate parameter for normalizing remanent intensity in order to determine relative variations in the intensity of the paleomagnetic field. We therefore have measured the rémanent intensity (both natural and demagnetized to 15 mT) and susceptibility of archive quarters of three cores at centimeter intervals using an automated through-bore magnetometer. A further test of the normalized intensity records is provided by the coherence function between the normalized remanence and the susceptibility of the cores. One of our cores displays high coherence over a broad range of frequencies, while for two others, coherence is insignificantly different from zero at the 95% level of confidence. Oxygen isotopic records, paleontological datum levels and the Brunhes-Matuyama boundary provide an independent temporal framework for inter-core comparison. When the two cores which pass our acceptance criteria are placed on a common time scale, the coherence between the normalized intensity records is significantly different from zero at well above the 95% level of confidence, suggesting some common input signal over the same band of frequencies. Furthermore, there is a great deal of similarity between the records from the Ontong-Java Plateau and a record from core RC10-167 taken some 3000 km to the north. The distribution of intensities obtained from these sedimentary records has the same shape as the absolute virtual dipole moment data obtained from lava flows (0–5 Ma), with a slightly smaller standard deviation. The inter-core agreement within a single region, the similarity of records from 3000 km apart and the general correspondence of statistical character of these sediments with lava flow data all argue that the normalized intensity records presented here reflect variations in the intensity of the ancient geomagnetic field. Spectral analysis of the paleointensity time series shows that there a is significant enhancement of variance concentrated in frequencies around 33 thousand years, over the period 0–350 ka; this feature is however lacking for the period 350–700 ka.

Stokking, LB, Tauxe L.  1990.  Properties of Chemical Remanence in Synthetic Hematite - Testing Theoretical Predictions. Journal of Geophysical Research-Solid Earth and Planets. 95:12639-12652.   10.1029/JB095iB08p12639   AbstractWebsite

We synthesized hematite under controlled conditions of the applied magnetic field in order to test the behavior of chemical remanent magnetization (CRM) predicted on the basis of theories developed to explain thermoremanent magnetization (TRM). We restrict this investigation to the remanence; acquired during mineral crystallization (grain-growth CRM) and do not consider chemical remanence acquired during mineral alteration. The material produced by our technique is hematite, up to 10 μm in diameter. Thermal demagnetization to 200°C removes the viscous component acquired under identical field/temperature conditions to those prevalent during synthesis. As predicted by analogy to TRM, the CRM acquired parallels the orientation of the magnetic field applied during growth. The intensity of chemical remanence is a linear function of the field in which it grew, BCRM up to 7.5 mT, the maximum growth field investigated. Furthermore, the ratio of intensities of CRM to TRM acquired in the same field is independent of the strength of that field. The intensity of BCRM controls the growth and orientation of hematite crystals, a result not predicted from theory derived by analogy to TRM. The control on crystal growth by the field is reflected in the dependence on BCRM of the orientation of ellipsoids of anisotropy of isothermal remanence and the acquisition of isothermal and anhysteretic remanence.

Stokking, LB, Tauxe L.  1990.  Multicomponent Magnetization in Synthetic Hematite. Physics of the Earth and Planetary Interiors. 65:109-124.   10.1016/0031-9201(90)90080-h   AbstractWebsite

We have investigated the directional properties of chemical remanent magnetization (CRM) carried by hematite synthesized in two successive generations in two distinct magnetic fields. Previously, we showed that the magnetization of hematite synthesized in a single generation under constant magnetic field conditions parallels the field in which it grew; we now demonstrate that hematite precipitated in two magnetic fields carries a remanence that is far more complex. In the simplest of these two-field experiments, we precipitated hematite in one generation in the presence of a magnetic field (B1) and in a second generation in zero field. The synthetic material acquired a single component of remanence approximately parallel to B1. We then precipitated hematite in two generations, but under constant magnetic field conditions. The resulting remanence was also uni-vectorial and paralleled the applied field. Finally, we synthesized hematite in two generations using perpendicular orientations of the applied field for the two generations. The resulting behavior of magnetic remanence was complex and samples recorded a variety of directions: both parallel and antiparallel to B1 and B2, as well as intermediate between the two fields. Four categories of behavior describe all observations. We suggest that the various types of behavior reflect the complexity inherent in the process of remanence acquisition by crystals precipitating from solution. The behavior of remanence can be explained in terms of a competition between the effect of the ambient magnetic field, the demagnetizing fields generated by pre-existing particles and possibly also exchange effects between the second-generation particles and first-generation particles used as seed crystals. A model that accurately predicts the behavior of remanence in a particular multigenerational experiment is difficult to conceive at present because of the complexity of the interplay of competing factors on the magnetization of the second-generation particles.

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
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.

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.

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.