Uranium and thorium series isotopes as indicators of geochemical processes in recent Venezuela Basin sediments

Miscellaneous · Fri Jan 01 00:00:00 EST 1988

OSTI ID:6721056

Cole, K P.H.

Several uranium and thorium series isotopes are important indicators of abyssal geochemical and physical processes: sedimentation, bioturbation, compaction, dissolution and precipitation. This research was designed to investigate the relative importance of each of these on early sediment diagenesis in different abyssal environments. Sediment samples were collected from three different sedimentary environments from the Venezuela Basin. Samples were designated as pelagic carbonate, hemipelagic and turbidite-rich, based on bulk sediment characteristics. Selected members of the U and Th radioisotope series ({sup 238}U, {sup 234}U, {sup 230}Th, {sup 226}Ra, {sup 210}Pb, and {sup 232}Th), {sup 14}C, and anthropogenic {sup 239,240}Pu were determined on selected intervals. Other sedimentary parameters, including porosity, calcium carbonate content, stable isotopes, macrofaunal abundances, organic carbon and grain size, were measured or available from the literature. A model, based on the constancy of {sup 230}Th production in sea water, was developed to determine fine-scale sedimentation rates for the last 14 ky, 6 ky, and 2 ky for sediments from pelagic carbonate, hemipelagic and turbidite-rich environments, respectively. Nannofossil {delta}{sup 13}C values correlated well with carbonate accumulation rates. {sup 226}Ra fluxes across the sediment/sea water interface were estimated from losses in the expected {sup 226}Ra activities. {sup 226}Ra fluxes across the interface were low due to low {sup 230}Th activities. A multi-layer explicit finite difference model was developed to simulate the effects of diffusive and advective bioturbation on the distributions of {sup 210}Pb and {sup 239,240}Pu in abyssal sediments.

• Research Organization: Texas A and M Univ., College Station, TX (USA)
• OSTI ID: 6721056
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
SEDIMENTARY BASINS
GEOCHEMISTRY
VENEZUELA
BIODEGRADATION
CALCIUM CARBONATES
CARBON 13
CARBON 14
COMPACTING
DEPTH
DIAGENESIS
DISSOLUTION
FINITE DIFFERENCE METHOD
FOSSILS
GEOLOGIC HISTORY
GEOLOGIC MODELS
ISOTOPE RATIO
LEAD 210
ORGANIC MATTER
PARTICLE SIZE
PLUTONIUM 239
PLUTONIUM 240
POROSITY
PRECIPITATION
RADIUM 226
SEAWATER
SEDIMENTARY ROCKS
SEDIMENTATION
SEDIMENTS
THORIUM 230
THORIUM 232
URANIUM 234
URANIUM 238
VARIATIONS
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
ALPHA DECAY RADIOISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CALCIUM COMPOUNDS
CARBON 14 DECAY RADIOISOTOPES
CARBON COMPOUNDS
CARBON ISOTOPES
CARBONATES
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
DEVELOPING COUNTRIES
DIMENSIONS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GEOLOGIC STRUCTURES
HEAVY ION DECAY RADIOISOTOPES
HEAVY NUCLEI
HYDROGEN COMPOUNDS
ISOTOPES
ITERATIVE METHODS
LATIN AMERICA
LEAD ISOTOPES
LIGHT NUCLEI
MAGNESIUM 28 DECAY RADIOISOTOPES
NEON 24 DECAY RADIOISOTOPES
NUCLEI
NUMERICAL SOLUTION
OXYGEN COMPOUNDS
PLUTONIUM ISOTOPES
RADIOISOTOPES
RADIUM ISOTOPES
ROCKS
SEPARATION PROCESSES
SIZE
SOUTH AMERICA
STABLE ISOTOPES
THORIUM ISOTOPES
URANIUM ISOTOPES
WATER
YEARS LIVING RADIOISOTOPES
580000* - Geosciences