David R. Gaylord

Characterizing the heterogeneity and correlation of perchloroethene sorption and hydraulic conductivity using a facies-based approach

A facies-based approach was used to delineate both geochemical and physical aquifer property heterogeneity. Specifically, the parameters considered were the sorption coefficient (Kd) for a model organic contaminant and hydraulic conductivity (K) inferred from the particle size distribution. Subfacies-sized samples were analyzed for both tetrachloroethene Kd and K in a vertical core of the Borden aquifer. Both parameters were correlated with the six sedimentary facies identified within the vertical core. As a consequence of their relations to sedimentary facies, significant positive correlations between ln K and ln Kd which were different from the core-scale correlation and different from each other were identified for some facies. Fades-specific correlations generally resulted in improved statistics (i.e., higher correlation coefficients and reduced confidence intervals) compared to the core-scale correlation. The results suggest that a facies-based approach can be useful in characterizing the heterogeneity of the transport properties of sedimentary aquifers.

Aeolian-climatic thresholds and sand dunes at the Hanford site, south-central Washington, U.S.A.

Aeolian-climatic thresholds are quantified using time sequence analysis of 1948-87 aeolian and climatic data from the Hanford Site, south-central Washington. Calculations indicate that 30 unvegetated sand dunes will maintain their total 1987 volume if they are exposed to a climate having an average annual precipitation, wind speed, and temperature of approximately 15·5 cm, 3·5 ms −1 , and 11·8°C, respectively. Calculations also show that if average 1948-87 climate conditions continue for the next approximately 10–15 years, the volume of unvegetated dune sand in the dunes studied will decrease by approximately 18%. Aeolian-climatic projections are based on the assumptions that there will be no major changes in human, animal, or botanical impact on the surface and no major variations from historical seasonal climatic patterns.

Evaluating eolian-climatic interactions using a regional climate model from Hanford, Washington (USA)

Abstract A regional climate model (RCM) developed for the Hanford Site, Washington illustrates a potentially useful method for assessing eolian responses to regional climate change. The RCM is based on long-term relations between fundamental climatic variables of precipitation, temperature, and wind speed. Modelled data are integrated into eolian-climatic scenarios through maps of eolian susceptibility, plots of sand dune mobility, and calculated trends of unvegetated dune sand volumes. Results demonstrate the sensitivity of eolian-climatic interactions to small changes in precipitation. Analyses suggest that continuation of the 1977–1987 trend toward a cooler (−0.16°C) and wetter (+1.8 cm yr −1 ) climate over the next 10–15 years will result in a decrease of ∼18% in the volume of unvegetated dune sand. Further temperature reductions totaling 0.7°C would promote precipitation increases of 30% leading to an additional reduction of 98% in the volume of unvegetated dune sand. Modelling scenarios for a possible global warming of +4°C indicate that annual precipitation at Hanford would be negligible and vegetation would be eliminated from dune surfaces. Sand dune mobility would increase by over 400%.

Fluvial, coastal, nearshore, and shelf deposition in the Upper Proterozoic (?) to Lower Cambrian Addy Quartzite, northeastern Washington

Abstract Quartzose and lesser argillaceous strata of the approximately 1300 m thick Upper Proterozoic (?) to Lower Cambrian Addy Quartzite of northeastern Washington record shelf, coastal, and continental sedimentation on an actively subsiding, relatively young passive margin. The lower 400 to 500 m of the Addy Quartzite was deposited immediately following the initiation of subsidence in a wave-dominated coastal and eventually storm-dominated shelf environment. This sequence records relative sea level rise that culminated in high-stand conditions. These sediments grade upwards into approximately 150 m of fluvial strata that record progradation of terrestrial environments during a period of relative sea level fall and a regional low-stand. The upper 700 m of the Addy Quartzite fines upwards from nearshore- to shallow-marine-dominated sediments into shelf-dominated deposits. This sequence marks the reestablishment of net sea level rise. The overall fining-upwards trend displayed by the Addy Quartzite indicates that regional subsidence of the newly formed passive margin was one of the most important factors controlling Addy sedimentation. However, variation seen in this trend throughout the Addy Quartzite indicates that rates of sea level rise associated with subsidence fluctuated and occasionally even reversed. Causes for the variation are inferred to be related to variations in subsidence rates and sediment supply. Textural and compositional data suggest Addy detritus was derived from relatively proximal recycled sedimentary source terranes and more distal continental crystalline terranes.

Toroda Creek half graben, northeast Washington: Late-stage sedimentary infilling of a synextensional basin

The Toroda Creek half graben is one of several north-northeast–trending Eocene extensional basins associated in time and space with the Okanogan and Kettle metamorphic core complexes in the southern Omineca crystalline belt of Washington and British Columbia. Sedimentary rocks of the middle Eocene Klondike Mountain Formation are the youngest stratified, nonvolcanic rocks in the Toroda Creek half graben. These sedimentary rocks preserve details of the character of Toroda Creek half-graben basin development in a humid temperate setting, help constrain the timing of brittle faulting in the basin, and provide insight into approximate rates of Okanogan core-complex uplift. Facies distributions and provenance determinations indicate that the Klondike Mountain Formation accumulated in a localized basin. There is no evidence that the Klondike Mountain Formation strata in the Toroda Creek half graben were once part of a more widespread deposit that later was segmented by faulting into its present configuration. Klondike Mountain sedimentary strata consist of sedimentary, gravity-dominated rock-avalanche, slide, and debris-flow deposits that accumulated on alluvial fans that delivered their sediments into either a single elongate lake or a series of possibly interconnected lakes. Provenance determinations and facies distribution patterns suggest that Klondike Mountain detritus primarily was derived from steep, unstable highlands exposed in the footwall of the Bodie Mountain fault on the east side of the basin. Sediments at the southern end of the basin were shed from an upland created by a west-northwest–trending transfer fault (Granite Creek fault). Rates of footwall uplift (and/or basin subsidence) estimated from unroofing of plutonic and presumed mylonitic rocks suggest rapid and significant basin margin uplift.

Subedifice collapse of an andesitic stratovolcano: The Maitahi Formation, Taranaki Peninsula, New Zealand

The Maitahi Formation is a large-volume (>7.5 km 3 ) debris-avalanche deposit that resulted from a mid-Pleistocene (ca. 0.24–0.21 Ma) collapse of Pouakai Volcano, Taranaki Peninsula, New Zealand. It is best exposed at intermediate distances (12–14 km) from its source and consists of heterolithologic megaclast-rich and megaclast-poor facies. There are four megaclast and clast types: (1) volcanogenic sedimentary deposits derived from the cone and ring plain; (2) extrusive and intrusive igneous rocks derived primarily from the cone; (3) Pliocene mudstone-rich, subedifice bedrock; and (4) pyroclastic deposits derived from the cone and ring plain. Transport of intact, weakly to moderately lithified, volcanogenic sedimentary and bedrock megaclasts and megaclast domains, tens of meters in diameter, indicates that the W-NW–directed Maitahi debris avalanche was dominantly viscous and nonturbulent. Normally faulted, stratified megaclasts reflect flow dilation, whereas jigsaw-puzzle fractured megaclasts and clasts are evidence for early-stage compression and limited particle-particle and particle-substrate collisions. Folded and elongated megaclasts and clasts and injected interclast matrix reflect the influences of syn- and postavalanche compression, loading, penetrative shear, and pore-fluid overpressures. A significant subedifice bedrock and ring-plain megaclast and clast content distinguishes the Maitahi Formation from all other Taranaki Peninsula debris-avalanche deposits. Coupled with its large volume, the subedifice bedrock content also suggests that the Maitahi Formation originated from a deep-seated edifice collapse, unlike subsequent, and apparently shallower, edifice collapses at the nearby and genetically similar Egmont Volcano.

Latest Proterozoic to Early Cambrian Sedimentary-Tectonic Evolution of a Passive Margin Sequence, Northeastern Washington: ABSTRACT

The late Proterozoic to Early Cambrian Three Sisters formation, Addy Quartzite, and Gypsy Quartzite lie near the base of the Cordilleran miogeocline in northeastern Washington. Detailed stratigraphic and sedimentary examination of these units extends understanding of the evolution of western North America. These units were deposited on a newly rifted passive margin and record the final stages of late Proterozoic rifting and the early stages of subsequent early Paleozoic subsidence and transgression. The three Sisters formation, Addy Quartzite, and Gypsy Quartzite are correlative with the Brigham Group in southeastern Idaho and Utah, the Gold Creek Quartzite in northern Idaho, and the Flathead Quartzite in Montana and Wyoming.