Geology topics

J. R. Payne

Publications and source records attributed to J. R. Payne.

4 recordsLinked to original sources

USGS2007

Slightly weathered Exxon Valdez oil persists in Gulf of Alaska beach sediments after 16 years

Oil stranded by the 1989 Exxon Valdez spill has persisted in subsurface sediments of exposed shores for 16 years. With annualized loss rates declining from &sim;68% yr -1 prior to 1992 to &sim;4% yr -1 after 2001, weathering processes are retarded in both sediments and residual emulsified oil (“oil mousse”), and retention of toxic polycyclic aromatic hydrocarbons is prolonged. The n -alkanes, typically very readily oxidized by microbes, instead remain abundant in many stranded emulsified oil samples from the Gulf of Alaska. They are less abundant in Prince William Sound samples, where stranded oil was less viscous. Our results indicate that, at some locations, remaining subsurface oil may persist for decades with little change.

Environmental Science & Technology↗

USGS2007

An evaluation of petrogenic hydrocarbons in northern Gulf of Alaska continental shelf sediments - The role of coastal oil seep inputs

We compared hydrocarbons in water, suspended particulate matter (SPM), and riparian sediment collected from coastal watersheds along the Yakataga foreland with corresponding hydrocarbons in Gulf of Alaska benthic sediments. This comparison allows an evaluation of hydrocarbon contributions to marine sediments from natural oil seeps, coal and organic matter (e.g., kerogen) associated with eroding siliciclastic rocks. The samples from oil seeps show extensive loss of low-molecular weight n-alkanes (<n-C14) and the presence of large, bimodal unresolved complex mixtures (UCMs), in contrast to the hydrocarbon fingerprints on the SPM and riparian sediment samples collected upstream from the oil seeps. After entering the fluvial systems, hydrocarbons from seep oils are rapidly diluted, and associate with the SPM phase as oil-mineral-aggregates (OMA). Johnston Creek, the watershed containing the most prolific seep, conveys detectable seep-derived hydrocarbons to the Gulf of Alaska, but overall seep inputs are largely attenuated by the (non-seep) petrogenic hydrocarbon content of the high SPM loads. In contrast to the geochemical signature of seep oil, Gulf of Alaska benthic sediments are characterized by abundant alkylated naphthalene homologues, relatively smooth n-alkane envelopes (n-C9 through n-C34, but with elevated levels of n-C27, n-C29, and n-C31), and small UCMs. Further, hydrocarbons in benthic sediments are highly intercorrelated. Taken together, these characteristics indicate that seep oil is a negligible petrogenic hydrocarbon source to the Gulf of Alaska continental shelf. Coaly material separated from the benthic sediment samples using a dense liquid (???2.00 g cm-3) also accounted for a minor portion of the total PAH (1-6%) and total n-alkanes (0.4-2%) in the benthic samples. Most of the hydrocarbon burden in the sediments is found in the denser sediment fraction and likely derives from organic matter contributed by denudation of siliciclastic formations in the Yakutat terrane. We therefore conclude that previous investigations relying on source allocation models have considerably overestimated oil seeps as a hydrocarbon source to the Gulf of Alaska. ?? 2006 Elsevier Ltd. All rights reserved.

Organic Geochemistry↗

USGS1993

Interaction of rising frazil with suspended particles: Tank experiments with applications to nature

Widespread occurrence of sediment-laden (turbid) sea ice and high concentrations of diatoms and foraminifers in ice have recently been reported from both polar regions. Many possible mechanisms of particle entrainment into ice have been postulated, among which scavenging by rising frazil ice and nucleation or adhesion of ice onto suspended particles appear to be the most likely ones. No reliable experimental data on the mechanisms, however, are available. Because of the importance of turbid ice for sediment transport, tanks for laboratory-scale experiments were constructed, in which frazil crystals produced at the base were monitored rising through water column laden with various types of particulate matter, including plankton. Observations made in salt water are reported here. Over a distance of 1.5 m, frazil < 1 mm in diameter grew to crystals or flocs several cm in diameter, rising at average velocities of 2 to 3 cm/s. Rise velocities were a function of frazil size, but varied greatly due to interactions of ice particles of different size and velocity and the resulting turbulence. Sand-size particles could be either trapped permanently by rising frazil, or were temporarily supported and again released. With live plankton, a several-fold enrichment of ice occurred, suggesting that their irregular shapes or appendages were caught by ice flocs. Diatom- and foram tests were also relatively effectively trapped. The concentration of silt- and clay-size terrigenous detritus in frazil tended to increase relative to the water. We found no preferential sorting by ice in this size range. Various kinds of evidence showed that ice does not nucleate onto foreign particles, and has no adhesive properties. Foreign material resided in the interstices of crystal aggregates, and particles denser than water could be released by agitation, suggesting that scavenging is a mechanical process. With rising frazil, the settling of particulate matter therefore is either retarded or reversed, resulting in a net upward sediment flux and a sediment-laden ice cover from this process of suspension freezing.

Cold Regions Science and Technology↗

USGS1993

Interactions of frazil and anchor ice with sedimentary particles in a flume

Frazil and anchor ice forming in turbulent, supercooled water have been studied extensively because of problems posed to man-made hydraulic structures. In spite of many incidental observations of interactions of these ice forms with sediment, their geologic effects remain unknown. The present flume study was designed to learn about the effects of salinity, current speed, and sediment type on sediment dynamics in supercooled water. In fresh-water, frazil ice formed flocs as large as 8 cm in diameter that tended to roll along a sandy bottom and collect material from the bed. The heavy flocs often came to rest in the shelter of ripples, forming anchor ice that subsequently was buried by migrating ripples. Burial compressed porous anchor ice into ice-bonded, sediment-rich masses. This process disrupts normal ripple cross-bedding and may produce unique sedimentary structures. Salt-water flocs were smaller, incorporated less bed load, and formed less anchor ice than their fresh-water counterparts. In four experiments, frazil carried a high sediment load only for a short period in supercooled salt water, but released it with slight warming. This suggests that salt-water frazil is either sticky or traps particles only while surrounded by supercooled water (0.05 to 0.1 °C supercooling), a short-lived phase in simple, small tanks. Salt water anchor ice formed readily on blocks of ice-bonded sediment, which may be common in nature. The theoretical maximum sediment load in neutrally-buoyant ice/sediment mixture is 122 g/l, never reported in nature so far. The maximum sediment load measured in this laboratory study was 88 g/l. Such high theoretical and measured sediment concentrations suggest that frazil and anchor ice are important sediment transport agents in rivers and oceans.

Cold Regions Science and Technology↗