Paleomagnetic record of Site 177-1089

We report geomagnetic directional paleosecular variation, relative paleointensity proxies and oxygen isotope data from the upper 88 m composite depth (mcd) at South Atlantic Ocean Drilling Program (ODP) Site 1089 (40°56.2?S, 9°53.64?E, 4620 m water depth). The age model is provided by high-resolution oxygen isotope stratigraphy, augmented by radiocarbon dates from the upper 8 mcd of nearby piston core RC11-83. Mean sedimentation rates at Site 1089 are in the range of 15 to 20 cm/kyr. Two intervals during the Brunhes Chron, at ?29.6 mcd (?190 ka) and at ?48 mcd (?335 ka), have component magnetization directions with positive (reverse polarity) inclination; however, the excursional directions are heavily overprinted by the postexcursional field. Magnetite is the dominant carrier of magnetic remanence, and occurs in the pseudosingle-domain (PSD) grain size. An additional higher-coercivity magnetic carrier, characterized by low unblocking temperatures (<350°C), is assumed to be authigenic pyrrhotite. A decrease in magnetization intensity down core is mirrored by a reduction in pore water sulfate, indicating diagenetic reduction of magnetite. Despite down-core changes in magnetic mineralogy, normalized intensity records from Site 1089 are comparable with high-resolution paleointensity records from the North Atlantic (e.g., ODP Sites 983 and 984). Sediment properties and sedimentation patterns within the Cape (Site 1089) and Iceland (Sites 983 and 984) Basins are distinctly different at both millennial and orbital timescales and therefore preclude lithologic variability from being the source of this correlation. Variations in normalized intensity from Site 1089 therefore appear to reflect changes in global-scale geomagnetic field intensity.

Construction of a precise early Eocene orbital cyclostratigraphy for DSDP Site 80-550 from the Goban Spur, North Atlantic

We constructed a precise early Eocene orbital cyclostratigraphy for DSDP Site 550 (Leg 80, Goban Spur, North Atlantic) utilizing precession related cycles as represented in a high resolution X-Ray Fluorescence based Barium core log. Based on counting of those cycles, we constrain the exact timing of two volcanic ash layers in Site 550 which correlate to ashes +19 and -17 of the Fur Formation in Denmark. The ashes, relative to the onset of the Paleocene/Eocene Thermal Maximum (PETM), are offset by 862 kyr and 672 kyr, respectively. When combined with published absolute ages for ash -17, the absolute age for the onset of the PETM is consistent with astronomically calibrated ages. Using the current absolute age of 28.02 Ma for the Fish Canyon Tuff (FCT) standard for calibrating the absolute age of ash -17 is consistent with tuning option 2 in the astronomically calibrated Paleocene time scale of Westerhold et al. (2008) [Westerhold, T., Röhl, U., Raffi, I., Fornaciari, E., Monechi, S., Reale, V., Bowles, J., and Evans, H.F., 2008, Astronomical calibration of the Paleocene time: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 257, p. 377-403]. Using the recently recalibrated absolute age of 28.201 Ma for the FCT standard is consistent with tuning option 3 in the astronomically calibrated Paleocene time scale. The new results do not support the existence of any additional 405-kyr cycle in the early Paleocene astronomically tuned time scale.

Middle to Late Quaternary sedimentation and rock-magnetic of ODP Site 105-646

We examine rock-magnetic, carbonate, and planktonic foraminiferal fluxes to identify climatically controlled changes of terrigenous and pelagic sedimentation at Ocean Drilling Program (ODP) Site 646 (the Labrador Sea). Terrigenous sediments are brought to the site principally by bottom currents. We use a rock-magnetic parameter sensitive to changes in magnetic mineral grain size, the ratio of anhysteretic susceptibility to low-field magnetic susceptibility (XARM/X), to monitor changes in bottom-current intensity over time, with large values of XARM/X (finer-grained magnetic minerals) indicating weaker bottom currents. A second rock-magnetic parameter, magnetic mineral accumulation rate (KaT) was used to indicate variations in terrigenous flux. Planktonic foraminiferal and carbonate accumulation rates (Pfar and CaC03ar) are used as indicators of pelagic flux. Absolute age assignments are based on correlation between the planktonic foraminiferal oxygen-isotope variations for Site 646 and the SPECMAP master oxygen-isotope curve. Cross-correlation analyses of the parameters that we studied with respect to the SPECMAP curve suggest that from oxygen-isotope stages 21 to 11, sedimentation rate, KaT, X, CaCO3ar, and Pfar were at their maximums, whereas XARM/X was at its minimum during peak interglacials (i.e., 0 k.y. lag time with respect to minimum ice volume). However, all parameters we examined lag behind minimum ice volume from stages 11 to 1, indicating a change in timing of both pelagic and terrigenous fluxes at approximately 400 k.y. BP. The negative correlation coefficient between XARM/X and the SPECMAP curve further suggest that finer-grained magnetic minerals are deposited during glacial periods, which probably reflects weaker bottom currents. The shift observed in the lag times of parameters examined with respect to the SPECMAP record is attributed to a change in significance of orbital parameters. Spectral results exhibit strong power in eccentricity (about 100 k.y.) throughout the record. Kap X, CaCO3flr, and Pfar show significant power in obliquity (about 41 k.y.), whereas XARM/X shows significant power at 73 k.y. from stages 21 to 11. The 73-k.y. period in XARM/X is near the difference tone of obliquity and eccentricity: 1/43-1/102 = 1/69. Kar and XARM/X show power only in eccentricity from stages 11 to 1. X and Pfar show significant power in precession (about 18 and 22 k.y.) whereas CaC03ar has power at 34 k.y, which could be a combination of precession and obliquity. The shift in power of orbital parameters may by attributed to the effect of the about 413-k.y. signal of eccentricity.

Natural remanent magnetization of IODP Expedition 308, Holes U1319A, U1320A, U1322B, and U1324B from the northern Gulf of Mexico

Paleomagnetic analyses of the natural remanent magnetization of >1700 vertically oriented sediment samples from Integrated Ocean Drilling Program (IODP) Holes U1319A, U1320A, U1322B, and U1324B in the northern Gulf of Mexico reveal complex magnetostratographic signals for the Brazos-Trinity and Ursa region carried by detrital iron oxide minerals. Additionally, gyroremanent magnetization was observed to form during alternating-field demagnetization of samples containing an enhanced amount of magnetic iron sulfide minerals. Most characteristic remanent magnetization inclinations are reasonable for the site latitudes. Stable declinations allow for azimuth correction of the formerly unoriented drill cores.

Calcareous plankton response to orbital and millennial-scale climate changes from ODP Leg 161-975

The paleoenvironmental conditions through MIS 15-9 at the Mediterranean Ocean Drilling Program (ODP) Site 975 were interpreted by high resolution study of calcareous plankton assemblages compared with available d18O and d13C records and high resolution paleoclimate proxies from the Atlantic Ocean. Sea Surface Temperatures (SSTs) have been estimated from planktonic foraminiferal assemblages using the artificial neural networks method. Calcareous plankton varied dominantly on a glacial-interglacial scale as testified by the SST record, foraminiferal diversity, total coccolith abundance and changes in warm-water calcareous nannofossil taxa. A general increase in foraminiferal diversity and of total coccolith abundance is observed during interglacials. Warmest SSTs are reached during MIS 11, while MIS 12 and MIS 10 represent the coldest intervals of the studied record. During MIS 12, one of the most extreme glacials of the last million years, occurrence of Globorotalia inflata and of neogloboquadrinids indicates a shoaling of the interface between Atlantic inflowing and Mediterranean outflowing waters. Among calcareous nannofossils the distribution of Gephyrocapsa margereli-G. muellerae > 4 µm also supports a reduced Atlantic-Mediterranean exchange during MIS 12. Superimposed on glacial-interglacial variability, six short-terms coolings are recognized during MIS 12 and 10, which appear comparable in their distribution and amplitude to the Heinrich - type events documented in the Atlantic Ocean in the same interval. During these H-type events, N. pachyderma (s) and G. margereli-G. muellerae > 4 µm increase as a response to the enhanced inflow of cold Atlantic water into the Mediterranean via the Strait of Gibraltar. Mediterranean surface water hydrography appears to have been most severely affected at Termination V during the H-type event Ht4, possibly as a response to a large volume of Atlantic meltwater inflow via the Strait of Gibraltar and/or to freshwater/terrigenous input deriving from local mountain glaciers. Three additional SST coolings are recorded through MIS 14-16, but these are not well correlated with Heinrich - type events documented in the Atlantic Ocean in the same interval; during these cooling episodes only the subpolar Turborotalita quinqueloba increases. These results highlight the sensitive response of the Mediterranean basin to millennial-scale climate variations related to Northern Hemisphere ice-sheet instability and support the hypothesis that the tight connection between high latitude climate dynamics and Mediterranean sea surface water features can be traced through the Middle Pleistocene.

Orbital space debris [microform] : hearing before the Subcommittee on Space Science and Applications of the Committee on Science, Space, and Technology, House of Representatives, One Hundredth Congress, second session, July 13, 1988.

"No. 112."

Orbital refueling system (ORS) /

Cover title.

A thermistor probe for measuring particle orbital speed in water waves /

"March 1964."

A study of the accurate re-entry and precision landing of an orbital earth satellite.

Mode of access: Internet.

Mercury Project summary including results of the fourth manned orbital flight, May 15 and 16, 1963.

Mode of access: Internet.

The role of prediction in training with a simulated orbital docking task

Cover title.

A study of the effect of man's motion on the attitude and orbital motion of a satellite.

Technical report SEG-TR-65-41

Orbital dynamics of space vehicles.

Bibliography: p. 392-401.