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This study has developed paleomagnetic secular variation (PSV) records from Sites 1060, 1061, 1062, and 1063 (ODP Leg 172) from the western North Atlantic Ocean during MIS 11–12 (374–478 ka). We have identified 46 inclination features and 49 declination features that can be correlated among the records. We have also developed relative paleointensity records and identified 13 paleointensity features that can be correlated among them. These features can also be dated using the oxygen-isotope dated Global relative-paleointensity record PISO-1500 of Channell et al. (2009). There is one excursion located in these four records. We use the name Levantine/Bermuda Excursion developed elsewhere by Ryan (1972) and Channell et al. (2017). The Excursion occurred at 408 ± 4 ka. The excursion is recorded at Sites 1061, 1062, and 1063. The most detailed excursion records occur at Site 1062 where we have both shipboard PSV records and one u-channel PSV record of the excursion. The excursion has two intervals of excursional directions, one short interval (∼I ky) followed by a long interval (∼5 ky). Both intervals have counter-clockwise looping of the excursional directions and the excursion is considered to be a Class I Excursion (Lund et al., 2005). Statistical study of the PSV records after removal of the excursion directions has identified two characteristics of the 'normal' PSV. The first feature is a long-term (>104 yrs) deviation in inclination and declination averages from the overall site averages. These deviations suggest some type on long-term memory in the regional dynamo process. The second feature is the variation in PSV angular dispersion (a measure of directional variability). The angular dispersion is quite low (∼12°) for most of the 374–478 ka interval. But, there is a short (∼8 ky) interval with angular dispersion more than double the amplitude (∼25°-30°). This interval has a sharp (<3 ky) onset and termination, This interval contains the Levantine/Bermuda Excursion. Such high-angular dispersion intervals with associated excursions and low paleointensity appear to be regular distinctive features of the Brunhes Chron PSV. • Paleomagnetic secular variation for MIS 11/12. • Levantine/Bermuda Excursion. • Statistical study of PSV. [ABSTRACT FROM AUTHOR]

To create meaningful models of the geomagnetic field, high-quality directional and intensity input data are needed. However, while it is fairly straightforward to obtain directional data, intensity data are much scarcer, especially for periods before the Holocene. Here, we present data from twelve flows (age range ∼ 200 to ∼ 470 ka) in the East Eifel volcanic field (Germany). These sites had been previously studied and are resampled to further test the recently proposed multi-method palaeointensity approach. Samples are first subjected to classic palaeomagnetic and rock magnetic analyses to optimise the subsequent palaeointensity experiments. Four different palaeointensity methods – IZZI-Thellier, the multispecimen method, calibrated pseudo-Thellier, and microwave-Thellier – are being used in the present study. The latter should be considered as supportive because only one or two specimens per site could be processed. Palaeointensities obtained for ten sites pass our selection criteria: two sites are successful with a single approach, four sites with two approaches, three more sites work with three approaches, and one site with all four approaches. Site-averaged intensity values typically range between 30 and 35 μT. No typically low palaeointensity values are found, in line with paleodirectional results which are compatible with regular palaeosecular variation of the Earth’s magnetic field. Results from different methods are remarkably consistent and generally agree well with the values previously reported. They appear to be below the average for the Brunhes chron; there are no indications for relatively higher palaeointensities for units younger than 300 ka. However, our young sites could be close in age, and therefore may not represent the average intensity of the paleofield. Three of our sites are even considered coeval; encouragingly, these do yield the same palaeointensity within uncertainty bounds. [ABSTRACT FROM AUTHOR]

This study presents paleomagnetic results from Tancitaro volcanism in the Michoacan Guanajuato Volcanic Field, western Mexico, as a contribution to the time averaged field global database. Detailed paleomagnetic and rock-magnetic studies were carried out on eleven independent lava flows; 120 oriented, standard paleomagnetic cores were collected from Tancitaro volcano and surrounding areas. All sites were dated by means of 40Ar-39Ar (Ownby et al., 2007) as originating from 793 ka to present. Rock-magnetic experiments included continuous susceptibility and hysteresis measurements. Remanence is carried mostly by Ti-poor titanomagnetite of pseudosingle-domain magnetic structure. Eight out of eleven flows yield normal magnetic polarities while three sites yielded inconsistent paleodirections most probably due to lightning. Mean paleodirection from eight flows is Inc=39.5°, Dec=356.4°, k=29, α95=9.1° which corresponds to a pole position with Plat=84.4°, Plong=219.9°, K=33 and A95=8.5°, practically undistinguishable from expected Plio-Quaternary paleodirections, for the North American Craton. Paleosecular variation is compatible with other studies at the same latitude bands and with recent statistical models. The mean inclination falls within the uncertainties of the Geomagnetic Axial Dipole plus 5% quadrupolar contributions.

This study develops composite high-resolution, full-vector PSV records for the last 380 ka from three regions associated with ODP Leg 172 in the western North Atlantic Ocean. These records identify 207 inclination features and 196 declination features that are common to all three regions. The average sediment accumulation rates are ~25 cm/ky, which produce sampling intervals of ~100–200 years. Each region has been dated by a combination of oxygen isotope stratigraphy and carbonate stratigraphy. We also have developed relative paleointensity records from all three regions that have 34 features in common. The paleointensity features can also be correlated to the PISO-1500 global paleointensity record of Channell et al. (2009) and provide an independent chronostratigraphy. The directions have near Gaussian distributions with inclinations averaging about 6° lower than axial dipole expectation due to the ΔI anomaly. The intensities also have a near Gaussian distribution, but have some more low intensities than expected. There is reproducible evidence for 7 excursions in these records with good waveform information. The excursions last from ~900 to ~8400 years. Five of the excursions are Class I excursions with out-of-phase inclination and declination variability that produces clockwise or counter-clockwise circularity. Two of the excursions (Blake Event, 8α Excursion) are Class II excursions with in-phase inclination and declination variability. Both of these excursions should be considered local reversals due to their very fast (<200 year) in-phase directional movement to reversed polarity directions that hover there before returning quickly to normal polarity directions. We have complete full-vector PSV records that surround each of these excursions. Some excursions occur quickly with no distinctive pre- or post-excursion anomalous directional variability. Other excursions are preceded by 10–20 ky of anomalous directional variability (high angular dispersion). Some also show continuing anomalous directions for 10–20 ky after the excursions. All of these features suggest a close relationship between excursions themselves and the surrounding PSV. Statistical studies of the PSV also show distinctive patterns to the PSV variability. The angular dispersion in 3-ky intervals shows a distinctive bimodal distribution with high (low) values associated with low (high) intensities. The high angular dispersion (and low intensity) are associated with the seven recorded excursions in these regions. There is reproducible evidence for another 5 excursions elsewhere in the world, but not in our records, that are also associated with high angular dispersion intervals. We think this is corroborative evidence for the reality of these excursions. That means that 12 excursions have occurred in the last 380 ka. Overall assessment of the PSV records suggests that important non-linear behavior occurs in the geodynamo as a function of intensity. This behavior is noted in the sharp changes between low/high angular dispersion intervals. It suggests that the 9-ky averaged field is more multipolar and far from axial dipole expectation during low paleointensity. Non-linearity is also seen in the fast polarity flips associated with the two Class II excursions. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Under suitable conditions, magnetofossils (the inorganic remains of magnetotactic bacteria) can contribute to the natural remanent magnetization (NRM) of sediments. In recent years, magnetofossils have been shown to be preserved commonly in marine sediments, which makes it essential to quantify their importance in palaeomagnetic recording. In this study, we examine a deep-sea sediment core from offshore of northwestern Western Australia. The magnetic mineral assemblage is dominated by continental detritus and magnetite magnetofossils. By separating magnetofossil and detrital components based on their different demagnetization characteristics, it is possible to quantify their respective contributions to the sedimentary NRM throughout the Brunhes chron. In the studied core, the contribution of magnetofossils to the NRM is controlled by large-scale climate changes, with their relative importance increasing during glacial periods when detrital inputs were low. Our results demonstrate that magnetite magnetofossils can dominate sedimentary NRMs in settings where they are preserved in significant abundances. [Copyright &y& Elsevier]

Abstract: Paleomagnetic and rock magnetic investigation was performed on the 35-m long MD03-2595 CADO (Coring Adélie Diatom Oozes) piston core recovered on the continental rise of the Wilkes Land Basin (East Antarctica). Analysis of the characteristic remanent magnetization (ChRM) inclination record indicates a normal magnetic polarity for the uppermost 34m of the sequence and a distinctive abrupt polarity change at the bottom of the core. This polarity change, which spans a 27cm thick stratigraphic interval, represents a detailed record of the Matuyama–Brunhes (M–B) transition and it is preceded by a sharp oscillation in paleomagnetic directions that may correlate to the M–B precursor event. Paleomagnetic measurements enable reconstruction of geomagnetic relative paleointensity (RPI) variations, and a high-resolution age model was established by correlating the CADO RPI curve to the available global reference RPI stack, indicating that the studied sequence reaches back to ca. 800ka with an average sedimentation rate of 4.4cm/ka. Orbital periodicities (100ka and 41ka) were found in the ChRM inclination record, and a significant coherence of ChRM inclination and RPI record around 100ka suggests that long-term geomagnetic secular variation in inclination is controlled by changes in the relative strength of the geocentric axial dipole and persistent non-dipole components. Moreover, even if the relatively homogeneous rock magnetic parameters and lithofacies throughout the recovered sequence indicates a substantial stability of the East Antarctic Ice Sheet during the middle and late Pleistocene, influence of the 100ka and 41ka orbital periodicities has been detected in some rock magnetic parameters, indicating subtle variations in the concentration and grain-size of the magnetic minerals linked to orbital forcing of the global climate. [Copyright &y& Elsevier]

Abstract: We reconstruct the earth magnetic field in the Brunhes epoch at the Banda Sea by studying the paleomagnetic data from core MD012380, collected during the International Marine Global Change Study (IMAGES) VII Cruise in 2001. Magnetic analysis is carried out for whole core with a sampling spacing of 1cm by using u-channel. Magnetic susceptibility (χ), nature remanent magnetization (NRM), anhysteretic remanent magnetization (ARM), and isothermal remanent magnetization (IRM) are measured in our paleomagnetic experiment. Results show the low latitude geomagnetic field variation at the Banda Sea during the last ∼820kyr. Except for the Brunhes/Matuyama boundary (BMB), there is no clear signal of reverse events in paleo- inclination and paleo-declination patterns. However, the synthetic paleointensity curve displays the asymmetrical saw-tooth pattern that can be used for determining reverse events, and shows a maximum intensity drop at the BMB. The characteristics of paleointensity provide a useful tool to identify reverse signals and improve the difficulties from only using inclination and declination patterns, especially at low latitude. With the help of paleointensity, inclination and declination, we have identified five reverse events. Furthermore if we consider the secular variation effect, we think that the strong negative inclination observed in our study may be the zonal time-averaged field with paleo secular variation, rather than non-dipole effect within the Brunhes epoch. [Copyright &y& Elsevier]

Detailed palaeomagnetic integrated with rock magnetic studies have been carried out on a loess-palaeosol sequence in Baoji, Shaanxi province, southern Chinese Loess Plateau. For most samples stepwise thermal demagnetization revealed two well-defined magnetization components. A low-temperature component (LTC), which was isolated between 100 and 200 °C, is consistent with the present geomagnetic field direction. A high-temperature component (HTC), which was isolated between 250 and 620–680 °C, shows normal, reversed or transitional polarities. Our new magnetostatigraphy revealed two distinct geomagnetic excursions recorded in loess unit of L5 and palaeosol unit of S7, respectively, and the Matuyama-Brunhes (M-B) polarity boundary in loess unit of L8. Rock magnetic experiments demonstrated that the specimens from the excursion zones have the same magnetic properties as those from the Brunhes normal or Matuyama reversed polarity zones. Measurements of anisotropy of magnetic susceptibility (AMS) showed that the sediments have primary sedimentary fabrics. Based on the palaeoclimatological and magnetostratigraphic age models, the middle Brunhes excursion in loess L5 is dated at 413–433 ka, and the early Brunhes excursion is estimated to occur 23–33 ka after the M-B reversal. Comparing with previously reported geomagnetic excursions in the Brunhes chron, the middle Brunhes excursion (L5) is likely global. For the early Brunhes excursion (S7), we need further studies to examine its global occurrence. [ABSTRACT FROM AUTHOR]

Studies of palaeodirections and palaeointensities were carried out on andesite lavas from the older part of the late Quaternary Ontake Volcano, Japan. Recently published K-Ar ages of the Older Ontake lavas range from 740 to 393 Ka. Palaeomagnetic samples were collected at 24 sites which are either of the same locality or nearby the dating site. Determination of palaeodirections was straightforward at most of the sites. Exceptions are a few sites in which the site mean palaeodirections were obtained only by the great circle method due to large secondary components, possibly lightning strikes in origin. The obtained VGP angular dispersion of 14.3° around the mean is smaller than the representative value for the site latitude of 36°N, which could be attributed to an insufficient number of sampling sites. Thellier's experiments were successful in 25 specimens from three lavas out of 54 specimens from nine lavas, giving a moderate success rate of 46 per cent. The obtained flow mean palaeointensities of 21, 40 and 53 μT conform well with the worldwide trend of the global palaeointensity during the Brunhes Chron, which indicates possible maxima of the global palaeointensity around 0.7 and 0.35 Ma with following gradual decrease. [ABSTRACT FROM AUTHOR]

Abstract: Component natural remanent magnetizations derived from u-channel and 1-cm3 discrete samples from ODP Site 919 (Irminger Basin) indicate the existence of four intervals of negative inclinations in the upper Brunhes Chronozone. According to the age model based on planktic oxygen isotope data, these “excursional” intervals occur in sediments deposited during the following time intervals: 32–34 ka, 39–41 ka, 180–188 ka and 205–225 ka. These time intervals correspond to polarity excursions detected elsewhere, known as Mono Lake, Laschamp, Iceland Basin and Pringle Falls. The isotope-based age model is supported by the normalized remanence (paleointensity) record that can be correlated to other calibrated paleointensity records for the 0–500 ka interval, such as that from ODP Site 983. For the intervals associated with the Mono Lake and Laschamp excursions, virtual geomagnetic poles (VGPs) reach equatorial latitudes and mid-southerly latitudes, respectively. For intervals associated with the Iceland Basin and Pringle Falls excursions, repeated excursions of VGPs to high southerly latitudes indicate rapid directional swings rather than a single short-lived polarity reversal. The directional instability associated with polarity excursions is not often recorded, probably due to smoothing of the sedimentary record by the process of detrital remanence (DRM) acquisition. [Copyright &y& Elsevier]

Abstract: We report high-resolution paleomagnetic records obtained from six piston cores recovered on the continental rise of the Wilkes Land Basin (WLB), East Antarctica, in the frame of the Italian/Australian Wilkes Land Glacial History (WEGA) project. The studied cores, with a length of ca. 4m each, were collected from the gentle and steep sides of sedimentary ridges present in the lower part of the continental rise, and consist of very fine-grained sediments. Paleomagnetic measurements were carried out on u-channel samples. Apart from a low-coercivity magnetic overprint, removed after the first steps of alternating field demagnetization, each core is characterized by a well defined characteristic remanent magnetization. Paleomagnetic inclinations fluctuate around the expected value (of ca. −77°) for such high latitude sites and always indicate normal magnetic polarity. Short period oscillations to anomalously shallow paleomagnetic inclinations (up to −20°) were identified at different levels of the sampled sequences; positive (reverse) inclination values were however not observed. Specific rock magnetic measurements indicate a substantial homogeneity of the magnetic mineralogy in the sampled sequences. For each core we reconstructed curves of relative paleointensity (RPI, as computed by NRM20mT/κ and NRM20mT/ARM20mT) variation of the geomagnetic field. An original age model was established by tuning the individual RPI curves with the available global and regional reference RPI stacks. Paleomagnetic results, supported by other limited bio- and chronostratigraphic constraints, establish that all the cores are Late Pleistocene in age: two provide an expanded record of the last ca. 30ka (PC18 and PC19), three span the last ca. 100, 200 and 300ka (respectively, PC25, PC27 and PC26), and one reaches back to ca. 780ka (PC20), approaching the Brunhes–Matuyama transition. Thus, the WEGA paleomagnetic record provides the first experimental data documenting the dynamics and amplitude of the geomagnetic field variations at high southern latitudes during the Brunhes Chron. The individual normalized RPI records were merged in a WEGA RPI stacking curve spanning the last 300kyr. The comparison of the WEGA RPI individual and stacked curves with the global references RPI stacks shows that geomagnetic paleointensity variations, with periods longer than a few to tens kyr depending on the sedimentation rate, can be safely recognized in this sector of the peri-Antarctic margins. Furthermore, the stacking of the individual ChRM inclination records indicates that the recurrent swings to shallow paleomagnetic inclinations may be correlated to the main known geomagnetic excursions of the Brunhes Chron, supporting the validity of the age models. The reconstructed average sediment accumulation rates for the individual cores range from 0.6 to 19cm/ka and are compatible with their position within the WLB, with the lowest rates found close to the ridge of the sedimentary drifts. Moreover, the high-resolution age models obtained in this study provide original constraints to assess chronology, rates and amplitudes of the climatic and environmental processes affecting this key area of the peri-Antarctic margins during the Late Pleistocene. [Copyright &y& Elsevier]

In southern Turkey ongoing differential impingement of Arabia into the weak Anatolian collisional collage resulting from subduction of the Neotethyan Ocean has produced one of the most complex crustal interactions along the Alpine–Himalayan Orogen. Several major transforms with disputed motions, including the northward extension of the Dead Sea Fault Zone (DSFZ), meet in this region. To evaluate neotectonic motion on the Amanos and East Hatay fault zones considered to be northward extensions of the DSFZ, the palaeomagnetism of volcanic fields in the Karasu Rift between these faults has been studied. Remanence carriers are low-Ti magnetites and all except 5 of 51 basalt lavas have normal polarity. Morphological, polarity and K–Ar evidence show that rift formation occurred largely during the Brunhes chron with volcanism concentrated at 0.66–0.35 Ma and a subsidiary episode at ∼0.25–0.05. Forty-four units of normal polarity yield a mean of D/I=8.8°/54.7° with inclination identical to the present-day field and declination rotated clockwise by 8.8±4.0°. Within the ∼15-km-wide Hassa sector of the Karasu Rift, the volcanic activity is concentrated between the Amanos and East Hatay faults, both with left lateral motions, which have rotated blocks bounded by NW–SE cross faults in a clockwise sense as the Arabian Block has moved northwestwards. An average lava age of ∼0.5 Ma yields a minimum cumulative slip rate on the system bounding faults of 0.46 cm/year according with the rate deduced from the Africa–Arabia Euler vector and reduced rates of slip on the southern extension of the DSFZ during Plio-Quaternary times. Estimates deduced from offsets of dated lavas flows and morphological features on the Amanos Fault Zone [Tectonophysics 344 (2002) 207] are lower (0.09–0.18 cm/year) probably because they are limited to surface fault breaks and do not embrace the seismogenic crust.Results of this study suggest that most strike slip on the DSFZ is taken up by the Amanos–East Hatay–Afrin fault array in southern Turkey. Comparable estimates of Quaternary slip rate are identified on other faults meeting at an unstable FFF junction (DSFZ, East Anatolian Fault Zone, Karatas Fault Zone). A deceleration in slip rate across the DSFZ and its northward continuation during Plio-Quaternary times correlates with reorganization of the tectonic regime during the last 1–3 Ma including tectonic escape within Anatolia, establishment of the North and East Anatolian Fault Zones bounding the Anatolian collage in mid–late Pliocene times, a contemporaneous transition from transpression to transtension and concentration of all basaltic magmatism in this region within the last 1 Ma. [Copyright &y& Elsevier]

A palaeomagnetic study has been conducted from Indonesian lava flows and dykes. Sampling was concentrated to the Merapi and Merbabu volcanoes (central Java), the Bromo–Tengger volcanic complex, the Lurus volcano (both east of Java), and the Bawean Island. Numerical dating indicates that the rock units sampled have ages that are well distributed within the Brunhes chron. Only a few reverse polarity flows were probably emplaced during the late Matuyama chron. Alternating field (AF) and thermal demagnetization treatments were routinely used for all sites. Results from both methods were generally in good agreement, demonstrating the reliability and the reproducibility of the palaeomagnetic determinations obtained from 36 independent sites. The large dispersion of the directions and the age distribution indicate that a large spectrum of the secular variation has been sampled. Our best estimate of the mean Brunhes field direction in Java is characterized by a zero declination and an inclination anomaly of −4.7° (with a 95 per cent confidence angle of 5.3°). This value agrees with an axial dipolar field model, or a model to which a persisting zonal quadrupolar term of a few per cent of the geocentric axial dipole is added. This study adds new constraints to recent results which suggested that a large zone of negative inclination anomalies may have persisted in the southwestern Pacific ocean over the past 500 Kyr, and possibly extended toward the eastern Indian ocean. The present results do not support such an extension. They also suggest that the inclination anomaly may have varied over 100 Kyr, and that it was more pronounced in recent times. [ABSTRACT FROM AUTHOR]

Loess–palaeosol sequences from the western part of the East European loess province were palaeomagnetically studied. The position of the Matuyama–Brunhes boundary was found in the sequence at Zahvizdja (East Carpathian Foreland) overlying the surface that corresponds to the VI Dniestre terrace. This boundary is located within the accumulation horizon of an interglacial soil developed during the time equivalent of oxygen isotope stage 19. The lowermost palaeosol of this sequence, located just below the soil containing the Matuyama–Brunhes boundary record, can thus be correlated with oxygen isotope stage 21 and the VI Dniestre terrace was developed during oxygen isotope stage 22. Samples from the palaeosols (especially from their accumulation horizons) revealed the presence of secondary (postdepositional) components of magnetisation, some resistant to alternating field demagnetisation even as high as 100 mT. Fine-grained maghaemite is most probably the carrier of these components. Subsequent thermal demagnetisation can remove them, to establish the primary palaeodirections. Haematite and magnetite are the main carriers of remanent magnetisation of the loess layers. The degree of possible delay of remanence acquisition in loess sequences was assessed on sediments from three sections sampled in the Volhynia and Lublin uplands. Good correlation of directional changes recorded in coeval segments of loess sections shows that the characteristic magnetisation of aeolian deposits from the western part of the East European loess province is approximately syndepositional. [Copyright &y& Elsevier]

A paleomagnetic study has been conducted on three gravity cores obtained from the Ontong-Java Plateau (OJP) in the western equatorial Pacific in order to investigate long-term secular variations during the Brunhes Chron. The cores consist of nanofossil foraminiferal ooze, and covers the last 500,000–800,000 years with average sedimentation rates of 6–9 m/m.y. Downcore changes of magnetic concentration represented by magnetic susceptibility are a factor of six or less, and variations in magnetic grain size and mineralogy are estimated to be small from the hysteresis parameters, ratio of anhysteretic remanent magnetization (ARM) to saturation isothermal remanent magnetization (SIRM), and S ratio. These results indicate that the sediments are rock-magnetically homogeneous in general, and are hence suitable for relative paleointensity estimation. I chose SIRM as a normalizer for relative paleointensity. The three cores could be precisely correlated with each other using relative paleointensity variations. Depth-to-age conversion was carried out by tying to the Sint-800 paleointensity stack (). The ages are consistent with the oxygen-isotope stratigraphy available for one of the three cores. Inclination variations were obtained after alternating-field demagnetization. Large inclination anomaly, about −7° in average, was observed as has been suggested to occur in the western equatorial Pacific by some studies. The inclination records of the three cores were integrated into a single record based on the correlation by the relative paleointensity. Long-term inclination variations of the order of 10,000–100,000 years were recognized. The inclinations tend to deflect toward negative when relative paleointensity is low. The variations are similar in general to the record from the West Caroline Basin (), which supports their model that long-term inclination variation is controlled by relative strength of the geocentric axial dipole (GAD) and persistent non-dipole components. [Copyright &y& Elsevier]

Paleomagnetic and rock-magnetic studies on a hydraulic piston core (Ver98-1, St.6) from Academician Ridge, Lake Baikal showed the occurrence of a reversal excursion at 670–696 cm depth, which is at the base of marine oxygen isotope stage 6. A correlation of X-ray CT values, as a proxy of relative density, to the marine oxygen isotope record provides an age of 177–183 ka for this reversal excursion. It can be correlated with other excursion records from Lake Baikal, found in Core 287-K2 from Academician Ridge [King et al., Russ. Geol. Geophys. 34 (1993) 148–162] and in core BDP93-1 drilled on the Buguldeika saddle [BDP-93, Quat. Int. 37 (1997) 3–17]. We correlate the Lake Baikal reversal excursion with a well documented excursion in the Brunhes Chron, the Iceland Basin event (186–189 ka) from ODP Sites 983 and 984 in the North Atlantic [Channell, J. Geophys. Res. 104 (1999) 22937–22951]. Also the relative paleointensity record agrees well with that from ODP Site 983 [Channell, J. Geophys. Res. 104 (1999) 22937–22951]. The Lake Baikal excursion and the Iceland Basin event correspond to the minimum of relative intensity at 188 ka in Sint-800 [Guyodo and Valet, Nature 399 (1999) 249–252]. We argue that it is distinct from the Jamaica/Pringle Falls excursion, estimated at 205–215 ka [Langereis et al., Geophys. J. Int. 129 (1997) 75–94]. This is supported by the recalibration of the age of another excursion found in Core St.16 in Lake Baikal [Sakai et al., Bull. Nagoya Univ. Furukawa Mus. 13 (1997) 11–22] with an age of ∼223 ka, which is close to the age of the Jamaica/Pringle Falls excursion, as suggested earlier [King et al., Russ. Geol. Geophys. 34 (1993) 148–162]. The VGP path of the reversal excursion (177–183 ka) consists of a southward swing through the North Atlantic, followed by a loop through Africa and the Indian Ocean. The path morphology is similar to that of the Iceland Basin event from the North Atlantic [Channell, J. Geophys. Res. 104 (1999) 22937–22951]. [Copyright &y& Elsevier]

Piston core LC07, located west of the Sicily Strait in the Mediterranean Sea, unambiguously records the Matuyama/Brunhes (M/B) and the upper Jaramillo polarity reversals, with similar average sediment accumulation rates (SARs) for the Brunhes Chron (2.29 cm/kyr) and late Matuyama Chron C1r.1r (2.19 cm/kyr). We report a relative paleointensity record for the interval spanning the M/B boundary down into the Jaramillo Subchron, which is unique in the Mediterranean because existing records from this basin cover only the last 80 kyr. The average SAR in core LC07 is used to translate the depth-related paleointensity record to the time domain; the ratio of anhysteretic remanent magnetization to low-field magnetic susceptibility is climatically sensitive and is used to tune the age model. This correlation produces a good fit to the global ice volume model derived for summer insolation at 65°N. With this age model, a paleointensity minimum in association with the M/B boundary has a duration of about 4–5 kyr, while the directional change has a duration of <3 kyr. A second paleointensity minimum of similar duration is found about 16 kyr below the M/B boundary. This feature (precursor or ‘dip’ in the literature) has previously been recognized at the same time interval in many marine records, which reinforces the validity of our age model. Other relative paleointensity minima are found within chron C1r.1r, and, within the uncertainties of the respective age models, these minima coincide with those observed from the few published coeval paleointensity records. In particular, there is good correspondence between the ages of minima at about 0.92 and 0.89 Ma, which probably correlate with two geomagnetic excursions (Santa Rosa and Kamikatsura, respectively) that have been recorded in lava flows and dated using the 40Ar/39Ar technique. In contrast, a recently dated excursion at 0.83 Ma from La Palma seems to correspond to a paleointensity maximum. This observation is opposite to that expected and this excursion needs to be confirmed. In contrast to some recently published paleointensity records, spectral analysis of the LC07 record does not reveal identification of significant power at the orbital obliquity frequency. [Copyright &y& Elsevier]

Palynological data of the marine core M 16415-2 show latitudinal shifts of the northern fringe of the tropical rain forest in north-west Africa during the last 700 ka. Savanna and dry open forest expanded southwards and tropical rain forest expanded northwards during dry and humid periods, respectively. Until 220 ka B.P., the tropical rain forest probably kept its zonal character in West Africa during glacials and interglacials. It is only during the last two glacial periods that the rain forest possibly fragmented into refugia. Throughout the Brunhes chron, pollen and spore transport was mainly by trade winds. [ABSTRACT FROM AUTHOR]