Organic biomarker compound concentrations in sediments from DSDP Hole 96-619

A study of organic biomarker compounds which could serve as tracers of terrigenous and marine sedimentary organic matter sources was performed on samples from a 208.7 m hydraulic piston core hole (DSDP Hole 619) from the hemipelagic Pigmy Basin in the northern Gulf of Mexico. Organic carbon-normalized concentrations of total long chain (C37-C39) alkenones and some individual C27-C29 desmethyl sterols were determined to be useful proportional indicators (tracers) of preserved marine and terrigenous organic carbon, respectively. The alkenones, whose only known source is marine phytoplankton of the class Prymnesiophyceae, generally occurred in higher concentrations in interglacial isotope stages 1 and 5a-b than in the intervening glacial stages. Sterols (C27-C29), apparently of a dominantly terrigenous origin, occurred in lower concentrations during interglacial stages than in glacial stages. Tracers of both terrigenous and marine organic matter appear to be affected by the differential diagenetic alteration of the biomarker/Corg ratios, as indicated by a simple, first-order kinetic model. The lack of any desmethylor 4a-methylsterol which is linearly related to the proportion of marine sedimentary organic matter (as scaled by d13Corg) indicates that either (1) sedimentary diagenesis has obscured the biomarker/Corg vs. d13Corg record, or (2) phytoplanktonic assemblage changes caused variations in the biomarker/Corg ratio of the primary input. Preferential preservation of terrigenous sterols may result in a biased sedimentary record of sterol input which could be misinterpreted as indicating solely terrigenous sterol sources. A simple model which characterizes the effects of sedimentary diagenesis on the relationship between Corg-normalized biomarker ratios and d13Corg demonstrates the potential problems of long-term, differential-diagenetic skewing on those tracer records

Alkenones and reconstructed sea surface temperature from sediment core 96-619 (Table 1)

The sedimentary record of a ratio (UK37) of long chain (C37) unsaturated alkenones is a useful indicator of glacial-interglacial climatic change in the Late Quaternary northern Gulf of Mexico where a planktonic foraminiferal delta18O-CaCO3 record is complicated by meltwater and/or fluvial events (Williams and Kohl, 1986, doi:10.2973/dsdp.proc.96.137.1986). Application of a laboratory temperature calibration of the UK37 ratio (Prahl and Wakeham, 1987, doi:10.1038/330367a0) to a Pigmy Basin hydraulic piston core record (Deep Sea Drilling Project core 619) suggested that the minimum glacial surface mixed layer (SML) temperature was 8°+/-1°C colder than the Holocene high SML temperature of 25.6°+/-0.5°C. This predicted glacial-interglacial temperature difference was significantly larger than the differences predicted by either the foraminiferal delta18O or foraminiferal assemblage temperature methods (0.8°-2.0°C). This large difference may be caused by local Prymnesiophyte assemblage changes in response to climatically induced hydrographic changes. Interglacial periods may be dominated by pelagic Prymnesiophyte assemblages, while glacial periods may be dominated by neritic assemblages. A combined mechanism of both climatically varying Prymnesiophyte species assemblage and depth of alkenone biosynthesis may account for the large difference between the temperature methods

Physical properties and bulk organic geochemical results for sediments from DSDP Hole 96-619

The concentration and carbon isotopic composition (d13C) of sedimentary organic carbon (C_org), N/C ratios, and terrigenous and marine d13C_org endmembers form a basis from which to address problems of Late Quaternary glacial-interglacial climatic variability in a 208.7 m hydraulic piston core (DSDP 619) from the Pigmy Basin in the northern Gulf of Mexico. While interpretations of sedimentary d13C_org time series records are often not unique, paired analyses of d13C_org and N/C are consistent with the hypothesis that the C_org in the Pigmy Basin is a climatically determined mixture of C3-photosynthetic terrigenous and marine organic matter, confirming the earlier d13C_org model of Sackett (1964). A high resolution (~1.4-2.9 Ka/sample) d13C_org record shows that sedimentary organic carbon in interglacial oxygen isotope (sub)stages 1 and 5a-b are enriched in 13C (average +/-1 sigma values are -24.2+/-1.2‰ and -22.9+/-0.7‰ relative to PDB, respectively) while glacial isotope stage values 2 are relatively depleted (-25.6+/-0.5‰). Concentrations of terrigenous and marine sedimentary organic carbon are calculated for the first time using d13C_org and C_org measurements, and empirically determined terrigenous and marine d13C_org endmembers. The net accumulation rate of terrigenous organic carbon is 4.3+/-2.6 times higher in isotope stages 2-4 than in (sub)stages 1 and 5a-b, recording higher erosion rates of terrigenous organic material in glacial times. The concentration and net accumulation rates of marine and terrigenous C_org suggest that the nutrient-bearing plume of the Mississippi River may have advanced and retreated across the Pigmy Basin as sea level fell and rose in response to glacial-interglacial sea level change

Long-range transport of terrestrially derived lipids in aerosols from the south Pacific

Terrestrially produced participate organic matter can be transported relatively fast in the atmosphere, long distances over the ocean. It has been hypothesized that this atmospheric transport may be an important way of quickly introducing continentally-derived organic material to the surface waters of the open ocean1-11. After rapid transport through the water column to the sediment surface12, these terrestrial organic substances could account for an important fraction of the organic carbon found in the sedimentary record13. The atmospheric fluxes of these organic substances are large enough to have a major potential impact on the inventory of terrestrially derived lipid material, originating from vascular plant waxes, found in deep-sea sediments13. We present here the first use of organic compound biological source marker information in conjunction with long-range meteorological trajectory analysis to elucidate specific terrestrial source regions and to determine the transport pathways of organic material through the atmosphere to remote marine locations. © 2002 Nature Publishing Group

NASA-GSFC Nano-Satellite Technology Development

The scientific understanding of key physical processes between the Sun and Earth require simultaneous measurements from many vantage points in space. Nano-satellite technologies will enable a class of constellation missions for the NASA Space Science Sun-Earth Connections theme. These technologies will also be of great benefit to other NASA science enterprises. Each nano-satellite will weigh a maximum of 10 kg including the propellant mass. Provisions for orbital maneuvers as well as attitude control, multiple sensors and instruments, and full autonomy will yield a highly capable miniaturized satellite. All onboard electronics will survive a total radiation dose rate of 100 krads over a two year mission lifetime. Nano-satellites developed for in-situ measurements will be spin-stabilized, and carry a complement of particles and fields instruments. Nano-satellites developed for remote measurements will be three-axis-stabilized, and carry a complement of imaging and radio wave instruments. Autonomy both onboard the nano-satellites and at the ground stations will minimize the mission operational costs for tracking and managing a constellation. Partnerships with private industry and academic institutions will be utilized for the development, manufacturing, and testing of the nano-satellites. Key technologies under development will be described, which include: advanced, miniaturized chemical propulsion; miniaturized sensors; highly integrated, compact electronics; autonomous onboard and ground operations; miniaturized onboard methods of orbit determination; onboard RF communications capable of transmitting data to the ground from far distances; lightweight, efficient solar array panels; lightweight, high output battery cells; a miniaturized heat transport system; lightweight yet strong composite materials for the nano-satellite and deployer-ship structures; and simple, reusable ground systems