Description: Integrated Ocean Drilling Program (IODP) Site 303-U1308 (49° 53'N, 24° 14'W; water depth 3871 m) provides a record of magnetization directions, relative paleointensity (RPI), susceptibility and benthic stable isotope stratigraphy back to 3.2 Ma. The record since 1.5 Ma has been published (Channell et al., Earth and Planetary Science Letters, 274, 59-71, 2008). This paper deals with the interval from 1.3 Ma to 3.2 Ma (Early Pleistocene-Late Pliocene). The benthic oxygen isotope record in this interval can be correlated to marine isotope stages (MIS) 51 to KM2, with an apparent hiatus that removed MIS G1-G2, immediately below the Gauss-Matuyama boundary. The mean sedimentation rate for the 1.5-3.2 Ma period is 8.5 cm/kyr. The age model was built by correlation of the oxygen isotope record to the LR04 stack. Carbon isotope data imply the influence of North Atlantic Deep Water (NADW) during interglacials with influence of southern source waters during glacials throughout the period, but with more muted δ¹³C variations in the Gauss Chron. Apart from the expected polarity reversals, three magnetic excursions are recorded: Punaruu in MIS 31/32 at 1092 ka, Gilsa in MIS 54 at 1584 ka, and a newly recognized excursion labeled Porcupine (after the nearby Porcupine abyssal plane) in MIS G7 at 2737 ka. The ages of reversals at Site 303-U1308, on the LR04 time scale, are consistent with the current geomagnetic polarity timescale (GPTS) with the exception of the base of the Olduvai Subchron in MIS 73 at 1925 ka, 26 kyr younger than in the current GPTS. The RPI record at Site 303-U1308 is calibrated using the oxygen isotope age model, and combined with four other North Atlantic records to obtain a North Atlantic RPI stack for 1.2-2.2 Ma (NARPI-2200). For 2.2-3.2 Ma, no Atlantic RPI records other than Site 303-U1308 exist. The NARPI-2200 stack is compared with published RPI stacks: Epapis, Sint-2000 and PADM2M. The mean sedimentation rates of the North Atlantic sites in NARPI-2200 are greater (by about an order of magnitude) than most of the records incorporated in other stacks. The comparison of Pacific Epapis and NARPI-2200 yields an apparent lag for NARPI-2200 relative to Epapis, attributed the Epapis age model constructed by correlation of magnetic concentration parameters (a proxy for carbonate percentage) to a calibrated oxygen isotope record. The long RPI record from Site 303-U1308 yields a very similar mean value for the Brunhes and Matuyama virtual axial dipole moments (7.5 x 1022 A m²), implying no polarity bias for RPI as in Sint-2000 and PADM2M. The results strengthen the case that RPI can be used to improve global stratigraphic correlation, especially for sites with mean sedimentation rates up to several decimeters/kyr.

Description: Arctic deep-sea sediments often record intervals of negative inclination of natural remanence that are tens of centimeters thick, implying magnetic excursions with durations of tens of thousand years that far exceed excursion durations estimated elsewhere, and the lack of tight age control usually provides excessive freedom in the labeling of Arctic excursions. Fortuitous variations in sedimentation rate have been invoked to explain the “amplified” excursions. Alternating field demagnetization of natural remanent magnetization (NRM) of sediment cores 08JPC, 10JPC, 11JPC, and 13JPC recovered by the Healy Oden Trans-Arctic Expedition in August 2005 (HOTRAX05) to the Mendeleev-Alpha Ridge yields apparent magnetic “excursions” in sediments deposited in the Brunhes Chron. Thermal demagnetization of the NRM, however, implies multiple magnetization components with negative inclination components usually “unblocked” below ?350°C. Analysis of isothermal remanent magnetization acquisition curves from magnetic extracts indicates two magnetic coercivity components superimposed on one another. Magnetic experiments conducted under high and low temperatures show features that are characteristic for (titano)magnetite and titanomaghemite. Presence of the two magnetic phases is further confirmed by elemental mapping on a scanning electron microscope equipped for X-ray energy dispersive spectroscopy (EDS) and by high-resolution X-ray diffraction (XRD). It is unlikely that anomalously thick intervals of negative inclination in these Brunhes-aged sediments are caused by unusual behavior of the magnetic field in the Arctic area. We therefore attribute low and negative NRM inclinations in these cores to partially self-reversed chemical remanent magnetizations, apparently carried by titanomaghemite and acquired during the oxidation of detrital (titano)magnetite grains. The high Ti contents and high oxidation states indicated by EDS and XRD data provide the conditions required for partial self-reversal by ionic reordering during diagenetic maghemitization, and this process appears to have affected all HOTRAX05 cores collected from the Mendeleev-Alpha Ridge.

Description: Inclination patterns of natural remanent magnetization (NRM) in Quaternary sediment cores from the Arctic Ocean have been widely used for stratigraphic correlation and the construction of age models, however, shallow and negative NRM inclinations in sediments deposited during the Brunhes Chron in the Arctic Ocean appear to have a partly diagenetic origin. Rock magnetic and mineralogical studies demonstrate the presence of titanomagnetite and titanomaghemite. Thermal demagnetization of the NRM indicates that shallow and negative inclination components are largely "unblocked" below ~300 °C, consistent with a titanomaghemite remanence carrier. Following earlier studies on the Mendeleev-Alpha Ridge, shallow and negative NRM inclination intervals in cores from the Lomonosov Ridge and Yermak Plateau are attributed to partial self-reversed chemical remanent magnetization (CRM) carried by titanomaghemite formed during seafloor oxidation of host (detrital) titanomagnetite grains. Distortion of paleomagnetic records due to seafloor maghemitization appears to be especially important in the perennially ice covered western (Mendeleev-Alpha Ridge) and central Arctic Ocean (Lomonosov Ridge) and, to a lesser extent, near the ice edge (Yermak Plateau). On the Yermak Plateau, magnetic grain size parameters mimic the global benthic oxygen isotope record back to at least marine isotope stage 6, implying that magnetic grain size is sensitive to glacial-interglacial changes in bottom-current velocity and/or detrital provenance.

Description: Lack of foraminiferal carbonate in marine sediments deposited at high latitudes results in traditional oxygen isotope stratigraphy not playing a central role in Quaternary age control for a large portion of the globe. This limitation has affected the interpretation of Quaternary sediment drifts off the Antarctic Peninsula in a region critical for documenting past instability of the West Antarctic Ice Sheet (WAIS) and Antarctic Peninsula Ice Sheet (APIS). Here we use piston cores recovered from these sediment drifts in 2015 during cruise JR298 of the RRS James Clark Ross to test the usefulness for age control of relative paleointensity (RPI) data augmented by scant d18O data. Thermomagnetic and magnetic hysteresis data, as well as isothermal remanent magnetization (IRM) acquisition curves, indicate the presence of prevalent magnetite and subordinate oxidized magnetite ("maghemite") in the cored sediments. The magnetite is likely detrital. Maghemite is an authigenic mineral, associated with surface oxidation of magnetite grains, which occurs preferentially in the oxic zone of the uppermost sediments, and buried oxic zones deposited during prior interglacial climate stages. Low concentrations of labile organic matter apparently led to arrested pore-water sulfate reduction explaining oxic zone burial and downcore survival of the reactive maghemite coatings. At some sites, maghemitization has a debilitating effect on RPI proxies whereas at other sites maghemite is less evident and RPI proxies can be adequately matched to the RPI reference template. Published RPI data at ODP Site 1101, located on Drift 4, can be adequately correlated to contemporary RPI templates, probably as a result of disappearance (dissolution) of maghemite at sediment depths 〉~10m.

Description: The data comprise meters composite depth (mcd) versus volume susceptibility (x10-3 SI) and anhysteretic susceptibility from Integrated Ocean Drilling Program (IODP) Site U1306 drilled on the crest of the Eirik Drift (SW Greenland) in 2272 m water depth. The anhysteretic magnetization (ARM) was measured on a pass-through u-channel magnetometer and the volume susceptibilities were measured on a pass-through (u-channel) susceptibility bridge (see Channell et al., 2014). Planktic oxygen isotope (δ18O) and relative paleointensity (RPI) data are used in tandem to generate an age model for the last 1 Myr from Integrated Ocean Drilling Program (IODP) Site U1306 drilled on the crest of the Eirik Drift (SW Greenland) in 2272 m water depth. For the 1-1.5 Ma interval, the age model is based on RPI alone due to insufficient foraminifera for isotope analyses. Utilizing RPI and δ18O in tandem allows recognition of low-δ18O "events" prior to glacial Terminations I, III, IV, V, VII, VIII, IX and X, that are independently supported by radiocarbon dates through the last deglaciation, and are attributed to local or regional surface-water effects. At Site U1306, Quaternary sedimentation rates (mean ~15 cm/kyr) are elevated during peak glacials and glacial onsets, and are reduced during interglacials, in contrast to the pattern at Site U1305 in 3460 m water depth at the distal toe of the drift, 191 km SW of Site U1306. The contrasting sedimentation-rate pattern appears to hold for the entire ~1.5 Myr record. The slackening and/or shoaling (due to lowered salinity) of the Deep Western Boundary Current (DWBC) during glacial intervals coincided with greater sediment supply to Site U1306 whereas the deepening, and possibly increased vigor, of the DWBC during interglacial intervals boosted sediment supply to Site U1305.

Description: The data comprise meters composite depth (mcd) versus a relative paleointensity (RPI) proxy from Integrated Ocean Drilling Program (IODP) Site U1306 drilled on the crest of the Eirik Drift (SW Greenland) in 2272 m water depth. The RPI proxy is natural remanent magnetization (NRM) normalized by anhysteretic remanent magnetization (ARM). The NRM/ARM paleointensity proxy was calculated as a slope over the 20-60 mT peak field demagnetization range. Also listed are the correlation coefficients (r) representing the definition of the slopes. NRM and ARM were measured on a pass-through u-channel magnetometer (see Channell et al., 2014). Planktic oxygen isotope (δ18O) and RPI data are used in tandem to generate an age model for the last 1 Myr from Integrated Ocean Drilling Program (IODP) Site U1306 drilled on the crest of the Eirik Drift (SW Greenland) in 2272 m water depth. For the 1-1.5 Ma interval, the age model is based on RPI alone due to insufficient foraminifera for isotope analyses. Utilizing RPI and δ18O in tandem allows recognition of low-δ18O "events" prior to glacial Terminations I, III, IV, V, VII, VIII, IX and X, that are independently supported by radiocarbon dates through the last deglaciation, and are attributed to local or regional surface-water effects. At Site U1306, Quaternary sedimentation rates (mean ~15 cm/kyr) are elevated during peak glacials and glacial onsets, and are reduced during interglacials, in contrast to the pattern at Site U1305 in 3460 m water depth at the distal toe of the drift, 191 km SW of Site U1306. The contrasting sedimentation-rate pattern appears to hold for the entire ~1.5 Myr record. The slackening and/or shoaling (due to lowered salinity) of the Deep Western Boundary Current (DWBC) during glacial intervals coincided with greater sediment supply to Site U1306 whereas the deepening, and possibly increased vigor, of the DWBC during interglacial intervals boosted sediment supply to Site U1305.

Description: The data comprise meters composite depth (mcd) versus component declination, inclination and maximum angular deviation (MAD) values for natural remanent magnetization (NRM) from Integrated Ocean Drilling Program (IODP) Site U1306 drilled on the crest of the Eirik Drift (SW Greenland) in 2272 m water depth. The component magnetizations were determined from stepwise alternating field demagnetization of NRM and measured on a pass-through u-channel magnetometer (see Channell et al., 2014). Planktic oxygen isotope (δ18O) and relative paleointensity (RPI) data are used in tandem to generate an age model for the last 1 Myr. For the 1-1.5 Ma interval, the age model is based on RPI alone due to insufficient foraminifera for isotope analyses. Utilizing RPI and δ18O in tandem allows recognition of low-δ18O "events" prior to glacial Terminations I, III, IV, V, VII, VIII, IX and X, that are independently supported by radiocarbon dates through the last deglaciation, and are attributed to local or regional surface-water effects. At Site U1306, Quaternary sedimentation rates (mean ~15 cm/kyr) are elevated during peak glacials and glacial onsets, and are reduced during interglacials, in contrast to the pattern at Site U1305 in 3460 m water depth at the distal toe of the drift, 191 km SW of Site U1306. The contrasting sedimentation-rate pattern appears to hold for the entire ~1.5 Myr record. The slackening and/or shoaling (due to lowered salinity) of the Deep Western Boundary Current (DWBC) during glacial intervals coincided with greater sediment supply to Site U1306 whereas the deepening, and possibly increased vigor, of the DWBC during interglacial intervals boosted sediment supply to Site U1305.

Description: The Miocene Climatic Optimum (MCO; ~16.9 to 14.7 Ma) provides an outstanding opportunity to investigate climate-carbon cycle dynamics during a geologically recent interval of global warmth. We present benthic stable oxygen (d18O) and carbon (d13C) isotope records (5-12 kyr time resolution) spanning the late early to middle Miocene interval (18 to 13 Ma) at Integrated Ocean Drilling Program (IODP) Site U1335 (eastern equatorial Pacific Ocean). The U1335 stable isotope series track the onset and development of the MCO as well as the transitional climatic phase culminating with global cooling and expansion of the East Antarctic ice-sheet at ~13.8 Ma. We integrate these new data with published stable isotope, geomagnetic polarity and X-ray fluorescence (XRF) scanner-derived carbonate records from IODP Sites U1335, U1336, U1337 and U1338 on a consistent, astronomically-tuned timescale. Benthic isotope and XRF scanner-derived CaCO3 records depict prominent 100 kyr variability with 400 kyr cyclicity additionally imprinted on d13C and CaCO3 records, pointing to a tight coupling between the marine carbon cycle and climate variations. Our inter-site comparison further indicates that the lysocline behaved in highly dynamic manner throughout the MCO, with 〉75% carbonate loss occurring at paleo-depths ranging from ~3.4 to ~4 km in the eastern equatorial Pacific Ocean. Carbonate dissolution maxima coincide with warm phases (d18O minima) and d13C decreases, implying that climate-carbon cycle feedbacks fundamentally differed from the late Pleistocene glacial-interglacial pattern, where dissolution maxima correspond to d13C maxima and d18O minima. Carbonate dissolution cycles during the MCO were, thus, more similar to Paleogene hyperthermal patterns.