Silt Mixtures Research Articles

Chemical composition of cave sediment in Potočka zijalka, Mt. Olševa, North Slovenia

Potočka zijalka was a station of Aurignatien hunters and the site of rich fossil remains of Pleistocene large mammals. Clastic sediments were deposited in Würm and are an intimate mixture of gravel, sand, silt and clay occurring in various proportions. The fractions form distinct populations, which were transported by different agents, like rockfall, flowing water, ephemeral torrent flows and cryoturbation. The sediment constituents are petrologically rather diverse and indicate that they were derived from different parent rocks - Mesozoic limestone, Permian-Carboniferous shales, Tertiary fine-grained sediments and fluvial pebbly deposits. Bulk chemical composition is strongly influenced by the limestone component, but the majority of trace elements, like Ti, Li, V, Fe, Co, Zn, Ga, Y, REE, Zr, Nb, Cs, Hf and Th originates from clay and fine silt, and Mn, Pb, Ni, Cu and Sn mainly from the heavz minerals in the sand fraction. Ca, Mg, Br, Rb, Sr and U show strong correlation with the amount of carbonate component. Rare earth elements, normalised to PAAS are not appreciable fractionated and show light positive europium anomalies.

Liquefaction resistance of sand–silt mixtures: an experimental investigation of the effect of fines

The liquefaction resistance of a saturated fine to medium sand mixed with varying amounts of non-plastic fines was evaluated by laboratory cyclic triaxial tests. The test results were used to draw conclusions on the effect of fines content on the liquefaction potential of the mixtures in relation to the global void ratio as well as to the intergranular and the interfine void ratios. It was found that for fines content increasing from 0 to 44% the liquefaction resistance of mixtures with constant global void ratio decreases compared to that of the clean sand, whereas this trend is reversed for values of fines content greater than 44%. However, when intergranular or interfine void ratios were kept constant, the liquefaction resistance of the mixtures varied monotonically (i.e. continuously increased or decreased, respectively), for increasing values of fines content. The test results were also (a) examined in terms of the conceptual framework of Thevanayagam [20] whose predictive power was validated and (b) compared to seemingly contradictive results from the literature, which were reconciled when the variation of intergranular void ratio of the soil was taken into consideration.

Impact of fines content on a warm slurry extraction process using model oilsands ☆

Natural oilsands deposits are composed of a complex mixture of sand, silt, clay, water and bitumen. The bitumen content and silt fraction, or fines (<44 μm), have traditionally been used as primary measures of ore processability. However, it is now known that this rule of thumb is not always applicable. In fact, the variability of oilsands, in terms of both quality and composition, makes it difficult to determine the unbiased effect of any individual component on bitumen extraction from mined ore. To address this problem, a model oilsands (MOS) system has been devised to determine how the interactions of oilsands components affect bitumen recovery. In this preliminary work, the effects of bitumen and fines contents, connate water pH and sodium hydroxide (NaOH) dosages on primary bitumen recovery were determined under the conditions extant in the warm slurry extraction process (WSEP). A three-factor Box–Behnken experimental design was used to quantify the effects. Prior to incorporation into the model oilsands system, each component was characterized to ensure quality control between tests. For the simple model studied in this work, the fines content and sodium hydroxide addition were the most important parameters affecting primary bitumen recovery. Although a small amount of fines was required to recover bitumen in the absence of process aids, an excess of fines was always detrimental to bitumen recovery.

Influence of diet on dispersal of horse mussel Atrina zelandica biodeposits

Benthic suspension feeders repackage particulate matter into organic-rich biodeposits (feces and pseudofeces) that are released into near-bottom flows. Where suspension feeders are found in dense assemblages, they physically alter the near-bottom flow field and thus may affect the local pattern of particle deposition. This dispersal pattern will control the spatial flux of biodeposits, and potential effects on sediment properties and surrounding benthic fauna. We quantified the downstream dispersal of biodeposits produced by an array of horse mussels Atrina zelandica fed either cultured phytoplankton (P) or a mixture of phytoplankton and silt (PS), a diet range that mim- ics the natural variation in near-bed seston quality. Experiments were run in a laboratory flume at a free-stream velocity of 4.5 cm s -1 , a value typical of field conditions. Diet had a significant effect on A. zelandica feeding activity and the dispersal of biodeposits. Compared to the P biodeposits, a greater fraction of the PS biodeposits was ejected well above the horse mussel array into the acceler- ated overlying flow layer (62% compared with 35%). However, more of the PS biodeposits settled either within the A. zelandica array or in the 120 cm working section downstream of the array (43 vs 17% of P biodeposits). Despite overall similarity in size, PS biodeposits had a settling velocity twice that of the P biodeposits. Of biodeposits settling downstream of the array, more than 70% settled within 20 cm of the trailing edge, regardless of diet. The density of biodeposits decreased exponen- tially with distance from the array at a rate that was similar for both diets. Monte Carlo simulations with a simple boundary layer model generally reproduced this pattern, but also highlighted the importance of initial height above bottom as well as flow complexities in the downstream wake region. Thus, the quality and quantity of A. zelandica biodeposits reaching the bed depends on the interaction among behavioral responses to available diet, settling velocity and boundary layer flows. Such interactions should have strong but localized effects on the incorporation of pelagic productiv- ity into the sediments and their consequent impacts on benthic community structure.

Seedling emergence of Pinus sylvestris in characterized seedbed substrates under different moisture conditions

Establishment of Scots pine (Pinus sylvestris L.) stands from seed is often unsuccessful because of unsuitable environmental conditions, such as limited soil moisture or air humidity. Improved seedling emergence could be achieved by soil preparation if site-specific optimal seedbeds were specified. Therefore the effects of seedbed substrates (13 characterized mixtures of sand, silt, and organic matter) on seedling emergence were determined after 14-day emergence tests in small laboratory chambers with four moisture conditions (2 levels of relative air humidity (RH), 95 and 65%, in combination with 2 levels of substrate water tension, 3 and 10 kPa). Seeds were placed in (partially buried) and on noncompacted and compacted substrates. At 95% RH, seedling emergence was 80 to 95% (seed lot maximum 94%) regardless of the substrate, with the exception of seeds placed in silt substrates (30-70%). At 65% RH, seedling emergence was 90% on silt, but considerably lower on organic matter and sand substrates, where organic admixture improved emergence for sand, but had a neutral or negative effect for silt. At 65% RH, partial seed burial, i.e., with good seed-substrate contact, improved emergence for organic matter and sand substrates, but impaired emergence for pure silt in noncompacted substrates at 3 kPa soil water tension. The effect of compaction on emergence was small for most substrates and had an effect only at 65% RH and 10 kPa tension. Seedling emergence and soil hydraulic conductivity at 3 kPa water tension and 95% RH were negatively correlated for partially buried seeds, but regardless of seed position, they were positively correlated at 10 kPa tension and 65% RH. These results can be used as guiding principles for the creation of seedbed substrates and seeding techniques.

Postglacial history and paleoecology of Wampum, Manitoba, a former lagoon in the Lake Agassiz basin

A small paleolagoon along the margin of the glacial Lake Agassiz basin near Wampum, Manitoba, 130 km southeast of Winnipeg, contains an unusually thick and continuous sequence of late-glacial and Holocene organic sediment. Cores at 17 sites through this sequence provide insight into the fluctuations of the level of Lake Agassiz, the timing of the construction of the lake9s most extensive strandline (the Upper Campbell beach), and the paleoecology of this area during the past 10 000 14 C yr. The history of this area is established from 26 new AMS radiocarbon dates, siliceous microfossils, plant macrofossils, mineralogy, sediment characteristics, and stratigraphic relationships. Following deglaciation at Wampum about 11 14 C ka, deposition of largely unfossiliferous silty clay with occasional ice-rafted clasts represents relatively deep-water conditions in Lake Agassiz. Overlying this is a spatially and temporally variable mixture of silt, sand, peat, gyttja, and marl, containing an allochthonous assemblage of siliceous microfossils and plant macrofossils with a wide range of radiocarbon dates. These sediments were deposited in an embayment of Lake Agassiz, mainly in shallow, quiet waters, as the lake transgressed about 10 ka over the Moorhead low-water phase surface. Between about 9.7 and 9.3 ka, the Wampum embayment was progressively isolated from Lake Agassiz by growth of the Upper Campbell spit, resulting in the formation of a lagoon. Organic-rich deposits on the lakeward side of the lagoon were buried 9.3–9.4 ka by sand and gravel of the spit, and a thin overwash of sand marks this event throughout the lagoon. At about this time, Lake Agassiz fell below the Upper Campbell beach level. Subsequent accumulation at Wampum consists mainly of algal gyttja during the early Holocene and marl during the middle Holocene; only minor fluctuations in hydrological conditions occurred, except for slightly warmer and drier conditions between 6.2 and 4.0 14 C ka. These stable, shallow-water conditions may be due partly to persistent groundwater contributions to the site. Progressive encroachment of rooted aquatics led to present-day fen conditions; peat accumulation across the basin began by about 4.0 ka.

Postglacial history and paleoecology of Wampum, Manitoba, a former lagoon in the Lake Agassiz basin

Research Article| June 01, 2000 Postglacial history and paleoecology of Wampum, Manitoba, a former lagoon in the Lake Agassiz basin James T. Teller; James T. Teller 1Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada Search for other works by this author on: GSW Google Scholar Jan Risberg; Jan Risberg 2Department of Quaternary Research, Stockholm University, S-106 91, Stockholm, Sweden Search for other works by this author on: GSW Google Scholar Gaywood Matile; Gaywood Matile 3Manitoba Energy and Mines, Geological Services, 360–1395 Ellice Avenue, Winnipeg, Manitoba R3G 2N2, Canada Search for other works by this author on: GSW Google Scholar Stephen Zoltai Stephen Zoltai 4Canada Forest Service, Northern Forestry Centre, 5320–122 Street, Edmonton, Alberta T6H 3S5, Canada Search for other works by this author on: GSW Google Scholar GSA Bulletin (2000) 112 (6): 943–958. https://doi.org/10.1130/0016-7606(2000)112<943:PHAPOW>2.0.CO;2 Article history received: 06 Jul 1998 rev-recd: 01 Jul 1999 accepted: 15 Sep 1999 first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation James T. Teller, Jan Risberg, Gaywood Matile, Stephen Zoltai; Postglacial history and paleoecology of Wampum, Manitoba, a former lagoon in the Lake Agassiz basin. GSA Bulletin 2000;; 112 (6): 943–958. doi: https://doi.org/10.1130/0016-7606(2000)112<943:PHAPOW>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract A small paleolagoon along the margin of the glacial Lake Agassiz basin near Wampum, Manitoba, 130 km southeast of Winnipeg, contains an unusually thick and continuous sequence of late-glacial and Holocene organic sediment. Cores at 17 sites through this sequence provide insight into the fluctuations of the level of Lake Agassiz, the timing of the construction of the lake's most extensive strandline (the Upper Campbell beach), and the paleoecology of this area during the past 10 000 14C yr. The history of this area is established from 26 new AMS radiocarbon dates, siliceous microfossils, plant macrofossils, mineralogy, sediment characteristics, and stratigraphic relationships.Following deglaciation at Wampum about 11 14C ka, deposition of largely unfossiliferous silty clay with occasional ice-rafted clasts represents relatively deep-water conditions in Lake Agassiz. Overlying this is a spatially and temporally variable mixture of silt, sand, peat, gyttja, and marl, containing an allochthonous assemblage of siliceous microfossils and plant macrofossils with a wide range of radiocarbon dates. These sediments were deposited in an embayment of Lake Agassiz, mainly in shallow, quiet waters, as the lake transgressed about 10 ka over the Moorhead low-water phase surface. Between about 9.7 and 9.3 ka, the Wampum embayment was progressively isolated from Lake Agassiz by growth of the Upper Campbell spit, resulting in the formation of a lagoon. Organic-rich deposits on the lakeward side of the lagoon were buried 9.3–9.4 ka by sand and gravel of the spit, and a thin overwash of sand marks this event throughout the lagoon. At about this time, Lake Agassiz fell below the Upper Campbell beach level. Subsequent accumulation at Wampum consists mainly of algal gyttja during the early Holocene and marl during the middle Holocene; only minor fluctuations in hydrological conditions occurred, except for slightly warmer and drier conditions between 6.2 and 4.0 14C ka. These stable, shallow-water conditions may be due partly to persistent groundwater contributions to the site. Progressive encroachment of rooted aquatics led to present-day fen conditions; peat accumulation across the basin began by about 4.0 ka. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

PLEISTOCENE DIATOMS FROM THE 602, 000 YR B.P. LAVA CREEK B ASH

A lacustrine deposit in central Texas contains the southernmost known locality of the 602,000 yr old Lava Creek B volcanic ash, which came from the most recent eruption of the Yellowstone Caldera in Wyoming. Diatoms were concentrated in the basal 10 cm of the ash, which represents the initial ashfall. Subsequent sediments, which are increasingly less diatomaceous, contain a mixture of ash, silt and sand that was gradually washed into the lake. The diatoms preserved in the initial ashfall include both planktonic and benthic species typical of a cool, alkaline, moderate to high conductivity, slow-flowing stream or lake. Cells of some of the filamentous species were still attached to each other in chains of 10–15 individuals, and long, slender frustules measuring 180 × 5 μm were preserved intact. Because the Lava Creek B ash was ejected from a caldera lake, transport of diatoms from the crater lake with the ash is possible; however, the large initial volume of hot ejecta, the localization and concentration of diatoms in the lower part of the ash, the occurrence of linked chains of diatom frustules, and the preservation of long, slender forms argue against transport of the diatoms within the Wyoming ash. The absence of diatoms in the lacustrine sediments below and above main ashfall suggests that the ash changed the nature of of the surrounding chemical microenvironment to either induce the growth of diatoms in an otherwise unfavorable habitat, or preclude diatom dissolution in what had been, prior to the ashfall, an environment in which diatoms were not preserved. The diatoms encapsulated in the ash provide a snapshot of the diatom population living in the lake at and immediately after the time of the eruption.

Seedling emergence of &lt;i&gt;Pinus sylvestris&lt;/i&gt; in characterized seedbed substrates under different moisture conditions

Establishment of Scots pine (Pinus sylvestris L.) stands from seed is often unsuccessful because of unsuitable environmental conditions, such as limited soil moisture or air humidity. Improved seedling emergence could be achieved by soil preparation if site-specific optimal seedbeds were specified. Therefore the effects of seedbed substrates (13 characterized mixtures of sand, silt, and organic matter) on seedling emergence were determined after 14-day emergence tests in small laboratory chambers with four moisture conditions (2 levels of relative air humidity (RH), 95 and 65%, in combination with 2 levels of substrate water tension, 3 and 10 kPa). Seeds were placed in (partially buried) and on noncompacted and compacted substrates. At 95% RH, seedling emergence was 80 to 95% (seed lot maximum 94%) regardless of the substrate, with the exception of seeds placed in silt substrates (30-70%). At 65% RH, seedling emergence was 90% on silt, but considerably lower on organic matter and sand substrates, where organic admixture improved emergence for sand, but had a neutral or negative effect for silt. At 65% RH, partial seed burial, i.e., with good seed-substrate contact, improved emergence for organic matter and sand substrates, but impaired emergence for pure silt in noncompacted substrates at 3 kPa soil water tension. The effect of compaction on emergence was small for most substrates and had an effect only at 65% RH and 10 kPa tension. Seedling emergence and soil hydraulic conductivity at 3 kPa water tension and 95% RH were negatively correlated for partially buried seeds, but regardless of seed position, they were positively correlated at 10 kPa tension and 65% RH. These results can be used as guiding principles for the creation of seedbed substrates and seeding techniques.

Debris-flow deposits in an alluvial-plain succession; the Upper Triassic Callide Coal Measures of Queensland, Australia

The Carnian-Rhaetian Callide Coal Measures are preserved in a small (22.5 km by 8 km), partially fault-bounded basin remnant in east-central Queensland, Australia. The <150 m thick coal-measure succession is interpreted to have accumulated during a phase of mild crustal extension that formed a series of discrete, intermontane basins in eastern Australia. The succession fines upward from a conglomerate-rich lower part into a finer-grained and coal-bearing upper section (including coal seams <34 m thick), and is interpreted as the deposits of an alluvial-plain environment. Anomalous, matrix-rich diamictites, breccias, and conglomerates have been recognized within the succession at several localities, in many cases interbedded with coals. These are interpreted as the product of debris flows. Two debris-flow lithofacies are recognized: (1) mixtures of fine carbonaceous material, clay, silt, sand, gravel, and volcaniclastic debris, and (2) breccias consisting principally of coal clasts in a coaly matrix with minor clastic and volcaniclastic debris. Facies 1 is found in sharp-based, simple or composite bodies (<15 m thick) that are elongate to lobate in plan (with some multi-lobate), and as much as at least 1500 m long and 600 m wide. Facies 2 is less common and occurs in sharp-based units as much as 1.5 m thick, at least 200 m in length, and 60 m in width. Both facies are characterized by abundant fine matrix and a very poorly sorted clast population, and show little internal organization or sedimentary structure other than variably developed imbrication of coarse clasts. Parts of some bodies show an erosional base (with up to several meters of coal removed), although a flat, apparently non-erosional contact is more common. The distribution of debris flows in the Callide Coal Measures shows a coincidence with mapped faults and interpreted structural lineaments. The debris flows may have been triggered by fault movements, which formed rupture topography on the flat alluvial plain, and caused destabilization of water-saturated clastic and organic sediments. Some debris-flow bodies may have been mounded, such that subsequent peat formation was restricted until those bodies were buried. The preservation of debris-flow units at different stratigraphic levels along mapped structures suggests multiple paleoseismic events or multiple debris-flow events along those structures. The mixing of volcaniclastic debris into debris-flow facies suggests that seismic events were coincident with (or perhaps caused by) nearby, explosive volcanic activity. The close relationship between debris-flow deposits and thick coal bodies on the inferred downthrown sides of faults at Callide further suggests that periodic, tectonic subsidence may have facilitated thick coal accumulation.

The nutritional status and digestibility of Oreochromis niloticus L. diet in Lake Langeno, Ethiopia

The composition, nutrient content and digestibility of the diet of Oreochromis niloticus were studied based on stomach and rectal samples collected monthly between December, 1995, and December, 1996, from Lake Langeno. The diet of O. niloticus was composed of a mixture of algal-based detritus, macrophyte scraps, phytoplankton and silt. Inorganic silt, macrophytes and detritus were more dominant in the diet during the wet than in the dry season. Total organic matter (TOM) in the diet was generally low (413 mg g-1 d.w.) reflecting the high proportion of inorganic silt in all seasons. Carbohydrates, proteins and lipids were important nutrients and constituted on average about 139, 185 and 57 mg g-1 d.w., respectively. The levels of all these nutrients varied significantly (ANOVA, P<0.0001) between months and declined during the wet season. Variation was observed in the ability of the fish to digest and absorb the different components of the food. Protein (41%) was better assimilated than total organic matter (32.7%), carbohydrate (31.7) or lipids (29.8%). The quality of the food expressed as P:E ratio (18.6-28.8 mg KJ-1) ranged from inadequate to adequate. The condition factor (CF) of the fish varied significantly between months in males (ANOVA, F=12.99, p<0.0001) and females (ANOVA, F=14.46, p<0.0001). It is concluded that the relatively poor condition factor (CF= 1.67) of O. niloticus in Lake Langeno, compared with other Rift Valley Lakes, follows from the low organic matter content and high proportion of inorganic silt in the diet.

Use of Dredged Material Substrates by Nesting Terns and Black Skimmers

While islands formed as the result of dredging operations are becoming increasingly important as nesting habitat for colonial seabirds, the effect of the composition of these islands on their usefulness as colony sites is not adequately understood. Because some seabirds apparently prefer to nest on shell rather than on fine-textured dredged material (a mixture of sand, silt, and clay), we studied black skimmers (Rhyncops niger), least terns (Sterna antillarum), and gull-billed terns (S. nilotica) to determine if their reproductive success differed between the 2 substrates We also tested the hypotheses that the substrate composition might affect vegetation growth, substrate surface temperatures, and nest visibility. The average proportion of eggs that hatched was higher for nests on shell than for nests on fine-textured dredged materials (P = 0.025); however, the proportion of nests in which at least 1 egg hatched was not different between substrates (P = 0.214). Vegetation densities and cover were higher on fine-textured dredged materials than on shell after 2 growing seasons (P ≤ 0.010), but not after only 1 season (P ≥ 0.112). The amount of time substrate temperatures were potentially stressful (≥42°C did not differ between substrates (P = 0.987). Human observers took longer to locate black skimmer and gull-billed tern nests on shell than on fine-textured dredged materials (P ≤ 0.008). Gull-billed terns (P ≤ 0.001), but not black skimmers (P = 0.343), nested on supplemental deposits of shell in larger numbers than on nearby areas of fine-textured dredged material. Our results suggest shell substrates are important for vegetation control, egg camouflage, and reproductive success. Where possible substrate composition should be manipulated for increased levels of shell when managing dredged material islands for nesting terns and black skimmers.

Impact into unconsolidated, water‐rich sediments at the Marquez Dome, Texas

Abstract— The Marquez Dome, Leon County, Texas represents a 13 km diameter Paleocene/Eocene impact structure formed in largely unconsolidated sediments in a near‐shore environment. The present study is an analysis of samples from cores taken from boreholes drilled separately on the edge of the central uplift and in the surrounding annular basin. The borehole drilled in the annular basin of the structure penetrated a sequence of interbedded sands, silts, and shales that is typical of the stratigraphy of the surrounding area. In contrast, the borehole drilled on the edge of the central uplift penetrated material that is relatively homogeneous in chemical composition and texture and may represent a mixture of sand, silt, clay, and minor carbonate derived from deeper levels in the preimpact stratigraphy. Veins containing pseudotachylitic breccias are not found and are not expected in this environment because low‐strength target materials are not conducive to frictional melting. Similarly, the low strength and unconsolidated nature of these target materials are not conducive to the formation of other types of typical impact breccias (e.g., melt rocks or suevites). The absence of such lithologies results either from explosive ejection of these materials caused by the water‐rich character of the target sediments or, more probably, from removal of these materials by deeper postimpact erosion than has been suggested previously. Planar deformation features (PDFs) were not found in quartz grains from any of these samples. The scarcity of quartz grains with PDFs, which have only been reported in rare impact breccias from the central uplift, and the large amount of vertical displacement indicated for the central uplift of this structure may also be a consequence of the low strength of target materials.

Steam Stripping Organics from “Fluidized” Soils (versus Confined Soils)

A laboratory comparison is made between the ability to steam strip organic contaminants from soil in the confined state and the ability to do so in the “fluidized” state. The soil used was a 50/50 mixture of beach sand and river silt. It was found that the removal of benzene, toluene, and xylene and dodecane occurred much faster and to a much greater extent in the “fluidized” soil than in the confined soil.

Upper Paleozoic strata of the Chaco-Paranábasin, Argentina, and the great Gondwana glaciation

Late Paleozoic glaciation in the southern Chaco-Paranábasin, Argentina, is recorded in cores from the Ordoñez Formation. The upper Ordoñez Formation consists of diamictite with lesser amounts of sandstone and shale, and is up to 1600 m thick. The diamictite-bearing interval was deposited during the Potonieisporites- Lundbladispora to Cristatisporites palynozones, probably in the latest Carboniferous-Early Permian. Diamictites are red to gray, thickly bedded, very poorly sorted mixtures of clay, silt, and sand with floating pebbles up to 5 cm long. These beds are structureless or show soft-sediment shear banding. An origin of diamictites related to glaciation is interpreted because of the following: the presence of dropstone pebbly mudshale; the angularity of sand grains and pebbles; the mixture of clast types in diamictite; and the freshness of most sand grains and pebbles. Subaqueous mudflow deposition is suggested for some diamictites because of interbedding with dropstone-bearing strata. Medium-scale, moderate to high-angle cross bedding is interbedded with other diamictite. That diamictite is interpreted as having been deposited as subglacial till or from subaerial ice-related mudflows. Pebble and sandstone composition in the Ordoñez Formation indicate a provenance terrane consisting of limestone, granite, gneiss, shale, sandstone, and volcanic units that existed to the west. Ordoñez Formation diamictite also becomes redder in wells in the Chaco-Paranábasin toward the western provenance area. The upper Ordoñez Formation is inferred to be partly contemporaneous with Paleozoic glacial deposits of the Paranábasin of Brazil, but was associated with a different ice lobe. Overlying the Ordoñez Formation is the Permian Victoriano Rodrı́guez Formation, which consists of shale and sandstone that was deposited in fluvial, floodbasin, and shallow to possibly deep-aqueous environments when the basin apparently was free of ice.

Pile capacity by direct CPT and CPTu methods applied to 102 case histories

Six methods to determine axial pile capacity directly from cone penetration test (CPT) data are presented, discussed, and compared. Five of the methods are CPT methods that apply total stress and a filtered arithmetic average of cone resistance. One is a recently developed method, CPTu, that considers pore-water pressure and applies an unfiltered geometric average of cone resistance. To determine unit shaft resistance, the new method uses a new soil profiling chart based on CPTu data. The six methods are applied to 102 case histories combining CPTu data and capacities obtained in static loading tests in compression and tension. The pile capacities range from 80 to 8000 kN. The soil profiles range from soft to stiff clay, medium to dense sand, and mixtures of clay, silt, and sand. The pile embedment lengths range from 5 to 67 m and the pile diameters range from 200 to 900 mm. The new CPTu method for determining pile capacity demonstrates better agreement with the capacity determined in a static loading test and less scatter than by CPT methods.

An investigation of seabed acoustic penetration and scattering via broadband echo soundings

Recent experiments were conducted in the Mediterranean Sea with the intention of developing a better understanding of the physics of acoustic penetration into and scattering from the seabed. Two shallow water sites were studied, one near Viareggio, Italy and the other off the coast of Sardinia. One site consisted of a fine mixture of silt and sand, with a large amount of trapped gas, while the other included a layer of marine vegetation that produced a bright acoustic return ahead of the bottom echo. Echo soundings were collected with a broad beam impulsive sound source operating over a band between 1 and 15 kHz. The data acquisition system was configured to record the acoustic pulse before and after encountering the seabed, from which a calibrated measure of the seabed’s reflective character was obtained. The measured reflection coefficient was compared with model predictions, based on a poroelastic theory for the seabed. In general the measured reflection coefficients exceeded the predictions significantly. A likely hypothesis is that trapped gas bubbles act to enhance the reflection. A description of various signal processing techniques that were employed will be included, along with a discussion of relationships between the processed acoustic data and known structural features. [Work supported by ONR.]

Physical and chemical characteristics of sediments from prawn farms and mangrove habitats on the Clarence River, Australia

The culture of Penaeus monodon in earthen ponds produces a black, glutinous sediment which has caused degradation of waterways in some countries and is suspected of reducing farm productivity. Superficially, the sediment is similar to that found in mangrove habitats, however, there have been few studies which compare these materials. This study describes the physical and chemical characteristics of sediment from four Australian prawn farms and compares results with those from nearby sites in intertidal mangrove habitats of the Clarence River, Australia. At the farms, sediment accumulated in the centre of ponds and around drains at variable rates (20 × 10 3–180 × 10 3 kg ha −1 per crop), depending on the stability of pond walls, prevailing winds, type of soil and aeration rates. The main source of the sediment was soil eroded from the pond walls and from the periphery of pond bottoms. The accumulating sediment was a mixture of silt and clay size particles, with a median particle size of 13 μm. Chemical analysis showed it consisted of (by weight): quartz, feldspar and clay minerals (70–80%); amorphous oxides of silicon, iron and aluminium (5–10%); organic matter and volatile compounds (5–10%); elevated levels of trace metals and nutrients. Inputs of food, faeces and decaying plankton enriched the sediment, increasing the organic carbon content from 13.9 mg g −1 at the periphery of ponds to 22.8 mg g −1 in the centre. Fresh and dried sediment had neutral pH, although soil in the pond walls was often acidic. In the centre of ponds, total nitrogen (2.25 mg g −1) and total phosphorus (690 μg g −1) were significantly higher than at the periphery. There were abundant microalgal fragments and high levels of amorphous silica (10–15% by volume) on the bottom of ponds, and calculations suggest that weathering of clay provided 87% of the silicon used by diatoms. The sediment in intertidal mangrove habitats was physically and chemically similar to sediment from the periphery of prawn ponds, while sediment from inland forest mangrove habitats was similar to sediment which accumulated in the centre of prawn ponds.

Home Range and Seasonal Movements of the Turtle Graptemys flavimaculata

Home Range and Seasonal Movements of the Turtle Graptemys flavimaculata

Use of Combined Air Sparging and Soil Vacuum Extraction (AS/SVE) and Groundwater Recovery and Treatment as Remedial Alternatives for Dissolved DNAPL Recovery: ABSTRACT

Corrective action has been implemented to address a dissolved dense non-aqueous phase liquid (DNAPL) plume in the vicinity of a former waste impoundment at the Paxon Polymer Company facility, located north of Baton Rouge, Louisiana. Assessment activities focused on the characterization of the geologic and hydrologic properties of the sediments underlying the area of investigation and the impact of the dissolved DNAPL plume to the soils and groundwater. Geologic characterization revealed that the facility is underlain by Quaternary age sediments consisting of mixtures of fine-grained sands, silt, and clay. Two hydrologic units were identified within the shallow sediments which are referred to as the Upper Permeable Zone and Second Permeable Zone. The investigation focused on the impacted soils and groundwater of the Upper and Second Permeable Zones. The Upper and Second Permeable Zones were characterized hydrologically to determine the most applicable remedial alternative for addressing the dissolved DNAPL plume. Pilot tests consisting of soil vacuum extraction (SVE), combined air sparging with SVE (AS/SVE), and groundwater recovery were performed. Evaluation of these remedial technology alternatives resulted in the selection of the combined AS/SVE system alternative for the Upper Permeable Zone and the groundwater recovery alternative for the Second Permeable Zone. Recoveredmore » off-gas from the combined AS/SVE treatment system from the Upper Permeable Zone is treated through use of a granular activated carbon unit, while recovered groundwater form the Second Permeable Zone is treated by use of a low-profile air stripper.« less