Bulk stable carbon and oxygen isotopes from ODP Site 1258, and Fe intensities from ODP Site 1262, and minimal tuning age model options for ODP Site 1258 and 1262

Timing is crucial to understanding the causes and consequences of events in Earth history. The calibration of geological time relies heavily on the accuracy of radioisotopic and astronomical dating. Uncertainties in the computations of Earth's orbital parameters and in radioisotopic dating have hampered the construction of a reliable astronomically calibrated time scale beyond 40 Ma. Attempts to construct a robust astronomically tuned time scale for the early Paleogene by integrating radioisotopic and astronomical dating are only partially consistent. Here, using the new La2010 and La2011 orbital solutions, we present the first accurate astronomically calibrated time scale for the early Paleogene (47-65 Ma) uniquely based on astronomical tuning and thus independent of the radioisotopic determination of the Fish Canyon standard. Comparison with geological data confirms the stability of the new La2011 solution back to ~54 Ma. Subsequent anchoring of floating chronologies to the La2011 solution using the very long eccentricity nodes provides an absolute age of 55.530 {plus minus} 0.05 Ma for the onset of the Paleocene/Eocene Thermal Maximum (PETM), 54.850 {plus minus} 0.05 Ma for the early Eocene ash -17, and 65.250 {plus minus} 0.06 Ma for the K/Pg boundary. The new astrochronology presented here indicates that the intercalibration and synchronization of U/Pb and 40Ar/39Ar radiometric geochronology is much more challenging than previously thought.

Lucky Strike records of hydrothermal outflow temperatures

We deployed autonomous temperature sensors at black smoker chimneys, cracks, and diffuse flow areas at the Lucky Strike hydrothermal field (Mid-Atlantic Ridge, ~37°17'N) between summer 2009 and summer 2012 and contemporaneously measured tidal pressures and currents as part of the long-term MoMAR experiment to monitor hydrothermal activity. We classify the temperature data according to the hydrogeologic setting of the measurement sites: a high-temperature regime (>190°C) representing discharge of essentially unmixed, primary hydrothermal fluids through chimneys, an intermediate-temperature regime (10-100°C) associated with mixing of primary fluids with cold pore fluids discharging through cracks, and a low-temperature regime (<10°C) associated with a thermal boundary layer forming over bacterial mats associated with diffuse outflow of warm fluids. Temperature records from all the regimes exhibit variations at semi-diurnal tidal periods, and cross-spectral analyses reveal that high-temperature discharge correlates to tidal pressure while low-temperature discharge correlates to tidal currents. Intermediate-temperature discharge exhibits a transitional behavior correlating to both tidal pressure and currents. Episodic perturbations, with transient temperature drops of up to ~150°C, which occur in the high-temperature and intermediate-temperature records, are not observed on multiple probes (including nearby probes at the same site), and they are not correlated with microearthquake activity, indicating that the perturbation mechanism is highly localized at the measurement sites within the hydrothermal structures. The average temperature at a given site may increase or decrease at annual time scales, but the average temperature of the hydrothermal field, as a whole, appears to be stable over our 3 year observation period.

Paleomagnetic of ODP Hole 197-1203A

On the basis of studies of Holocene samples,submarine basaltic glass (SBG) is thought to be an ideal paleointensity recorder because it contains unaltered single domain magnetic inclusions that yield Thellier paleointensity data of exceptional quality. To be useful as a recorder of the long-term geomagnetic field, older SBG must retain these optimal properties. Here, we examine this issue through rock magnetic and transmission electron microscope (TEM) analyses of Cretaceous SBG recovered at Ocean Drilling Program Site 1203 (northwestern Pacific Ocean). These SBG samples have very low natural remanent magnetization intensities (NRM <50 nAm**2/g) and TEM analyses indicate a correspondingly low concentration of crystalline inclusions. Thellier experiments on samples with the strongest NRM intensity (>5*10**-11 Am**2) show a rapid acquisition of thermoremanent magnetization (TRM) with respect to NRM demagnetization. Taken at face value,this behavior implies magnetization in a very weak (617 WT) ambient field. But monitoring of magnetic hysteresis properties during the Thellier experiments (on subsamples of the SBG samples used for paleointensity determinations) indicates systematic variations in values over the same temperature range where the rapid TRM acquisition is observed. A similar change in properties during heating is observed on monitor SBG specimens using low-temperature data: with progressive heatings the Verwey transition becomes more distinct. We suggest that these experimental data record the partial melting and neocrystallization of magnetic grains in SBG during the thermal treatments required by the Thellier method,resulting in paleointensity values biased to low values. We further propose that this process is pronounced in Cretaceous and Jurassic SBG (relative to Holocene SBG) because devitrification on geologic time scales (i.e., tens of millions of years) lowers the transition temperature at which the neocrystallization can commence. Magnetic hysteresis monitoring may provide a straightforward means of detecting the formation of new magnetic inclusions in SBG during Thellier experiments.

Triennial skeletal stable oxygen isotope ratios of Diploria labyrinthiformis

The reconstruction of the climatic history during the past several hundred years requires a sufficient geographical coverage of combined climate proxy series. Especially in order to identify causal connections between the atmosphere and the ocean, inclusion of marine records into composite climate time series is of fundamental importance. We present two skeletal delta18O chronologies of coral skeletons of Diploria labyrinthiformis from Bermuda fore-reef sites covering periods in the nineteenth and twentieth centuries and compare them with instrumental temperature data. Both time series are demonstrated to display sea-surface temperature (SST) variability on inter-annual to decadal time scales. On the basis of a specific modern delta18O vs instrumental SST calibration we reconstruct a time series of SST anomalies between AD 1350 and 1630 covering periods during the Little Ice Age. The application of the coral delta18O vs temperature relationship leads to estimates of past SST variability which are comparable to the magnitude of modern variations. Parallel to delta18O chronologies we present time series of skeletal bulk density. Coral delta18O and skeletal density reveal a strong similarity during Little Ice Age, confirming the reliability of both proxy climate indicators. The past coral records, presented in this study, share features with a previously published climate proxy record from Bermuda and a composite time series of reconstructed Northern Hemisphere summer temperatures. The coral proxy data presented here represent a valuable contribution to elucidate northern Atlantic subtropical climate variation during the past several centuries.

Paleoclimate record combinatio of speleothems and of sediment core GeoB3910-2

A substantial strengthening of the South American monsoon system (SAMS) during Heinrich Stadials (HS) points toward decreased cross-equatorial heat transport as the main driver of monsoonal hydroclimate variability at millennial time-scales. In order to better constrain the exact timing and internal structure of HS1 over tropical South America we assessed two precisely dated speleothem records from central-eastern and northeastern Brazil in combination with two marine records of terrestrial organic and inorganic matter input into the western equatorial Atlantic. During HS1 we recognize at least two events of widespread intensification of the SAMS across the entire region influenced by the South Atlantic Convergence Zone (SACZ) at 16.11-14.69 kyr BP and 18.1-16.66 kyr BP (labeled as HS1a and HS1c, respectively), separated by a dry excursion from 16.66-16.11 kyr BP (HS1b). In view of the spatial structure of precipitation anomalies, the widespread increase of monsoon precipitation over the SACZ domain was termed 'Mega-SACZ'.

Development of bacterial and archaeal communities in erupted subsurface muds at the Håkon Mosby mud volcano

The microbial oxidation of methane controls the emission of the greenhouse gas methane from the ocean floor. However, some seabed structures such as mud volcanoes have leaky microbial methane filters and can be important sources of methane. We investigated the disturbance and recovery of a methanotrophic mud volcano microbiome (Håkon Mosby mud volcano, 1250 m water depth), to assess time scales of community succession and function in the natural deep-sea environment. We analyzed 10 surface and 5 subsurface sediment samples across HMMV mud flows from most recently discharged subsurface muds towards old consolidated muds as well as one reference site (REF) located approximately 0.5 km outside of the HMMV. Surface samples were obtained in 2003, 2009 and 2010. The surface of the new mud flows at the geographical center was sampled in 2009 and 2010. Around 100 m south of the center, we sampled more consolidated aged muds in 2003 and 2010. Old mud flows were sampled around 300 m southeast and 100 m north of the geographical center in 2003, 2009 and 2010. Surface sediment samples (0-20 cm) were recovered either by TV-guided Multicorer or by push cores using the remotely operated vehicle Quest (Marum, University Bremen). Subsurface sediments of all zones (>2 m below sea floor) were obtained in 2003 by gravity corer. After recovery, sediments were immediately subsampled in a refrigerated container (0°C) and further processed for biogeochemical analyses or preserved at -20°C for later DNA analyses. Our study show that freshly erupted muds hosted heterotrophic deep subsurface communities, which were replaced by surface communities within a few years of exposure. Aerobic methanotrophy was established at the top surface layer within less than a year, followed by anaerobic methanotrophy, sulfate reduction and finally thiotrophy. Our data indicate that it takes decades in cold environments before efficient methanotrophic communities establish to control methane emission. The observed succession provides insights to the response time of complex deep-sea communities to seafloor disturbances.