ALBERT

Description: Magnetostratigraphy has been serving as a valuable tool for dating and confirming chronologies of lacustrine sediments in many parts of the world. Suitable paleomagnetic records on the Tibetan Plateau (TP) and adjacent areas are, however, extremely scarce. Here, we derive paleomagnetic records from independently radiocarbon-dated sediments from two lakes separated by 250 km on the southern central TP, Tangra Yumco and Taro Co. Studied through alternating field demagnetization of u-channel samples, characteristic remanent magnetization (ChRM) directions document similar inclination patterns in multiple sediment cores for the past 4000 years. Comparisons to an existing record from Nam Co, a lake 350 km east of Tangra Yumco, a varve-dated record from the Makran Accretionary Wedge, records from Lakes Issyk-Kul and Baikal, and a stack record from East Asia reveal many similarities in inclination. This regional similarity demonstrates the high potential of inclination to compare records over the Tibetan Plateau and eventually date other Tibetan records stratigraphically. PSV similarities over such a large area (〉3000 km) suggest a large-scale core dynamic origin rather than small scale processes like drift of the non-dipole field often associated with PSV records.

Description: A 30.5 m sediment core was recovered from the coastal lake Eilandvlei (EV13), which represents a unique high-resolution record of environmental change for southern Africa. For the establishment of a robust chronology, special emphasis was placed on the calibration of radiocarbon (14C) ages obtained from the dating of different material. However, the reliability of 14C ages can be problematic since coastal lakes interact with different source pools providing 14C-depleted ("old") carbon thus causing reservoir effects. The origin of old carbon affecting the EV13 samples was most likely sourced from the Indian Ocean. Two pre-bomb marine molluscan shells were therefore analysed to determine the regional marine reservoir offset (dR), with obtained dR values of 134 ± 38 and 161 ± 38 14C yrs providing the first available data for the south coast of South Africa. However, the application of the resulting average dRmean = 148 ± 27 14C yrs for the calibration of the entire EV13 record underestimates the variable reservoir effects throughout the Holocene. These were possibly caused by past changes in the connectivity between the present lake system and the ocean as well as a varying degree of upwelling in this area. To solve this problem, three sample pairs (each consisting of wood fragments and bulk organic sediment from the same core depth) were dated to calculate the variable past reservoir effects. This approach provided a median basal age of 8920 +200/-250 cal BP. Palaeomagnetic secular variation stratigraphy was used to corroborate the chronology for the topmost 1.5 m of the record (past millennium), thus providing the first Holocene sediment based inclination and declination data from South Africa.

Description: Location and water depth of the core tops used in this study alongside the percent sediment texture data. Magnetic hysteresis data are reported for the bulk sediment and the 5 fractions derived from the bulk sediment. Low temperature MS data are of the 10-32 Aµm fraction and have been interpolated to the nearest degree Celsius and cleaned of outliers.

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.