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• 1531. [Article] Stratigraphy and sedimentology of the Cretaceous Nanaimo group, Saltspring Island, British Columbia

  Clastic sedimentary rocks of the Nanaimo Group on Saltspring Island, British Columbia are Late Cretaceous in age, overlie a deformed and intruded Paleozoic basement complex, and consist of eight formations. ...

  Citation × Citation Citation Abstract Copy Title: Stratigraphy and sedimentology of the Cretaceous Nanaimo group, Saltspring Island, British Columbia Author: Hanson, William Bruce Clastic sedimentary rocks of the Nanaimo Group on Saltspring Island, British Columbia are Late Cretaceous in age, overlie a deformed and intruded Paleozoic basement complex, and consist of eight formations. These eight formations, from oldest to youngest, are the Comox, Haslam, Extension-Protection, Cedar District, De Courcy, Northumberland, Geoffrey, and Spray Formations. The Formations vary greatly in thickness, consist of multiple members, and show complex intertonguing relationships. A composite section of minimum thickness totals approximately 9,000 feet. In the study area, the Nanaimo Group is tentatively divided into two subgroups, the lower Nanaimo Group - Comox through Extension-Protection Formations - and upper Nanaimo Group - Cedar District through Spray Formations. The lower Nanaimo Group consists of a series of three transgressive sequences, each of which overlies an erosional surface and shows an upward-fining of grain size and progression from nonmarine or nearshore marine to offshore marine deposition. The upper Nanaimo Group can be divided into a total of five progradational cycles which show upward-coarsening from pro-delta mudstone to delta-front sandstone, and locally to fluvial-marine channel conglomerate. Prodelta muds were probably deposited at lower neritic to upper bathyal water depths. The Comox Formation was deposited as a delta or fan delta with a braided fluvial system and flanking littoral sandstones including beaches which contain heavy mineral placers and tidal creek channels. The Extension-Protection Formation was deposited along a piedmont plain with laterally contiguous marine turbidites. The Cedar District and De Courcy Formations intertongue through a stratigraphic interval of at least three thousand feet. Four Cedar District to De Courcy progradational cycles are characterized by an upward progression from offshore marine mudstone and distal turbidite to proximal turbidite or/and fluidized sediment flow and locally to a laminated and cross-bedded sandstone and channelized conglomerate lithofacies. The sequences are indicative of repeated superposition of prodelta, delta-front slope, and fluvial-marine environments of deposition. The Northumberland and overlying Geoffrey Formation comprise a very thick progradational sequence complete with a thick and extensive conglomeratic interval in the Geoffrey Formation. Mineralogy and Paleocurrent data of the Comox Formation suggest derivation from low to intermediate grade metamorphic and intermediate to basic igneous rocks located a short distance to the southwest. The overlying sandstone-conglomerate formations record a decreased contribution from metamorphic and basic igneous rocks and increased contribution from intermediate to silicic plutonics and volcanics. De Courcy paleocurrent data suggest derivation from the east: sandstone compositions indicate the major source was an uplifted region of intermediate plutonic rocks which was rapidly eroded and subject to mainly mechanical weathering. The Geoffrey Formation shows an abrupt increase in intermediate to silicic volcanic debris possibly derived from the Bonanza Volcanics located to the south and southwest on Vancouver Island. Post-depositional mineralogic changes include widespread cementation by calcite, laumontite, and quartz. The assemblage laumontite plus prehnite is locally developed in the Comox Formation. Laumontite occurs in all overlying sandstone formations. A green diagenetic matrix was derived from the in situ alteration of volcanic rock fragments and is particularly abundant in the Geoffrey Formation. Tertiary faulting and folding of the study area formed the Kulleet Syncline, Trincomali Anticline, a system of northwest-trending strike faults and a system of north-trending transverse faults. Title: Stratigraphy and sedimentology of the Cretaceous Nanaimo group, Saltspring Island, British Columbia Author: Hanson, William Bruce Clastic sedimentary rocks of the Nanaimo Group on Saltspring Island, British Columbia are Late Cretaceous in age, overlie a deformed and intruded Paleozoic basement complex, and consist of eight formations. These eight formations, from oldest to youngest, are the Comox, Haslam, Extension-Protection, Cedar District, De Courcy, Northumberland, Geoffrey, and Spray Formations. The Formations vary greatly in thickness, consist of multiple members, and show complex intertonguing relationships. A composite section of minimum thickness totals approximately 9,000 feet. In the study area, the Nanaimo Group is tentatively divided into two subgroups, the lower Nanaimo Group - Comox through Extension-Protection Formations - and upper Nanaimo Group - Cedar District through Spray Formations. The lower Nanaimo Group consists of a series of three transgressive sequences, each of which overlies an erosional surface and shows an upward-fining of grain size and progression from nonmarine or nearshore marine to offshore marine deposition. The upper Nanaimo Group can be divided into a total of five progradational cycles which show upward-coarsening from pro-delta mudstone to delta-front sandstone, and locally to fluvial-marine channel conglomerate. Prodelta muds were probably deposited at lower neritic to upper bathyal water depths. The Comox Formation was deposited as a delta or fan delta with a braided fluvial system and flanking littoral sandstones including beaches which contain heavy mineral placers and tidal creek channels. The Extension-Protection Formation was deposited along a piedmont plain with laterally contiguous marine turbidites. The Cedar District and De Courcy Formations intertongue through a stratigraphic interval of at least three thousand feet. Four Cedar District to De Courcy progradational cycles are characterized by an upward progression from offshore marine mudstone and distal turbidite to proximal turbidite or/and fluidized sediment flow and locally to a laminated and cross-bedded sandstone and channelized conglomerate lithofacies. The sequences are indicative of repeated superposition of prodelta, delta-front slope, and fluvial-marine environments of deposition. The Northumberland and overlying Geoffrey Formation comprise a very thick progradational sequence complete with a thick and extensive conglomeratic interval in the Geoffrey Formation. Mineralogy and Paleocurrent data of the Comox Formation suggest derivation from low to intermediate grade metamorphic and intermediate to basic igneous rocks located a short distance to the southwest. The overlying sandstone-conglomerate formations record a decreased contribution from metamorphic and basic igneous rocks and increased contribution from intermediate to silicic plutonics and volcanics. De Courcy paleocurrent data suggest derivation from the east: sandstone compositions indicate the major source was an uplifted region of intermediate plutonic rocks which was rapidly eroded and subject to mainly mechanical weathering. The Geoffrey Formation shows an abrupt increase in intermediate to silicic volcanic debris possibly derived from the Bonanza Volcanics located to the south and southwest on Vancouver Island. Post-depositional mineralogic changes include widespread cementation by calcite, laumontite, and quartz. The assemblage laumontite plus prehnite is locally developed in the Comox Formation. Laumontite occurs in all overlying sandstone formations. A green diagenetic matrix was derived from the in situ alteration of volcanic rock fragments and is particularly abundant in the Geoffrey Formation. Tertiary faulting and folding of the study area formed the Kulleet Syncline, Trincomali Anticline, a system of northwest-trending strike faults and a system of north-trending transverse faults. Close

• 1532. [Article] An assessment of plant community structure, herbivory, soils, and state-and-transition theory on a winterfat (Krascheninnikovia lanata [Pursh] A.D.J. Meeuse & Smit) ecological site

  State-and-transition models (STMs) have been successfully used to describe ecological dynamics in woodlands, shrublands, grasslands, and several other ecosystems. Changes in vegetation and soil are measured ...

  Citation × Citation Citation Abstract Copy Title: An assessment of plant community structure, herbivory, soils, and state-and-transition theory on a winterfat (Krascheninnikovia lanata [Pursh] A.D.J. Meeuse & Smit) ecological site Author: Matney, Casey A. State-and-transition models (STMs) have been successfully used to describe ecological dynamics in woodlands, shrublands, grasslands, and several other ecosystems. Changes in vegetation and soil are measured to gauge and predict plant community dynamics within ecological states and transitions between alternative ecological states. Ecological states and their boundaries are defined by a range of variability in vegetation and soil parameters. The ecological site classification system used in the United States requires the development of a unique STM model for each defined ecological site. The foundation of the ecological site concept is the estimation and quantification of a historical reference plant community. Historical information, land manager experience, and scientific data are used to quantify the historical reference plant community and gauge changes towards alternative stable states. In regards to winterfat plant communities and the Silty 6-10 PZ ecological site, conceptual STMs have not been fully developed or tested. The objective of this study was to develop, test, and refine a process-based, data supported, STM for the Silty 6-10 PZ ecological site. The predominant factor of disturbance on this ecological site for the last 100 years has been grazing by livestock. To develop the process-based STM for the ecological site, we conducted a piosphere study centered on a livestock watering point and a five-year grazing exclosure study. With these two studies we were able to quantify the resilience of the ecological site when protected from disturbance (exclosure study) and also to quantify the trends of the ecological site when under a continued grazing disturbance (piosphere study). We used the information gathered from both of these studies to refine the STM. The four strongest factors that indicated differences between ecological states were amount of biological soil crust, soil surface aggregate stability, density of winterfat, and frequency of Indian ricegrass. Data from this study supported the initial proposed STM for the Silty 6-10 PZ ecological site. States defined were a Reference Winterfat State (State 1), Sickle Saltbush State (State 2), and a Creeping Wildrye State (State 3). Each ecological state corresponds to a site characterized by high, moderate, and low ecological functioning, respectively. Title: An assessment of plant community structure, herbivory, soils, and state-and-transition theory on a winterfat (Krascheninnikovia lanata [Pursh] A.D.J. Meeuse & Smit) ecological site Author: Matney, Casey A. State-and-transition models (STMs) have been successfully used to describe ecological dynamics in woodlands, shrublands, grasslands, and several other ecosystems. Changes in vegetation and soil are measured to gauge and predict plant community dynamics within ecological states and transitions between alternative ecological states. Ecological states and their boundaries are defined by a range of variability in vegetation and soil parameters. The ecological site classification system used in the United States requires the development of a unique STM model for each defined ecological site. The foundation of the ecological site concept is the estimation and quantification of a historical reference plant community. Historical information, land manager experience, and scientific data are used to quantify the historical reference plant community and gauge changes towards alternative stable states. In regards to winterfat plant communities and the Silty 6-10 PZ ecological site, conceptual STMs have not been fully developed or tested. The objective of this study was to develop, test, and refine a process-based, data supported, STM for the Silty 6-10 PZ ecological site. The predominant factor of disturbance on this ecological site for the last 100 years has been grazing by livestock. To develop the process-based STM for the ecological site, we conducted a piosphere study centered on a livestock watering point and a five-year grazing exclosure study. With these two studies we were able to quantify the resilience of the ecological site when protected from disturbance (exclosure study) and also to quantify the trends of the ecological site when under a continued grazing disturbance (piosphere study). We used the information gathered from both of these studies to refine the STM. The four strongest factors that indicated differences between ecological states were amount of biological soil crust, soil surface aggregate stability, density of winterfat, and frequency of Indian ricegrass. Data from this study supported the initial proposed STM for the Silty 6-10 PZ ecological site. States defined were a Reference Winterfat State (State 1), Sickle Saltbush State (State 2), and a Creeping Wildrye State (State 3). Each ecological state corresponds to a site characterized by high, moderate, and low ecological functioning, respectively. Close

• 1533. [Article] Stability of gravel at artificially created spawning beds in uncontrolled streams

  Twenty-five gabion-type structures across the main stem and tributaries of the Siuslaw River in the Oregon Coastal Range, installed to expand the available spawning area for fish, were investigated for their ...

  Citation × Citation Citation Abstract Copy Title: Stability of gravel at artificially created spawning beds in uncontrolled streams Author: Helland-Hansen, Erik Andreas Twenty-five gabion-type structures across the main stem and tributaries of the Siuslaw River in the Oregon Coastal Range, installed to expand the available spawning area for fish, were investigated for their ability to perform gravel control functions such as trapping bedload carried by the stream or holding gravel placed behind the structures. The merits of gravel trapping structures in the main stem Siuslaw River were found to depend largely on channel features in the reach at and above the structures. Factors favoring successful developments were: ample gravel supply, high bed roughness, wide straight reaches, and lateral stream bed slopes deflecting flood water from the structure. Among limiting factors were: the existence of pools immediately upstream of structures, deficient gravel supply, curving stream alignment, and unfavorable lateral stream bed slopes. Main stem reaches with an instantaneous peak discharge exceeding 100 cfs per foot width were found questionable for development. The controlling factors in the tributary streams were found to be approach velocities and stream features such as bedrock smoothness, approach slope, channel alignment, constrictions, lateral bed slope, plunge pools, and lengths of gravel beds. Careful placing of gravel to predetermined slopes was found not to be warranted, as the stream would rework the gravel according to local influences. Reaches where the flow was retarded without widening and reaches where high velocities occurred were found especially unfavorable for gravel stability. Flume studies with simulated gabions and full-size gravel were carried out to study incipient motion and scour from a gravel bed behind a gabion. Scour was found to take place from the upstream portion of the gravel bed, resulting in an adversely sloping bed there. Bed forms of standing-wave type, with changing wave location, were encountered when the flow was in the critical region; subsequent scour would wash the bed waves out. Gravel transport from apparently stable beds subjected to very low flow strengths verified that gravel transport is a statistical phenomenon and that the threshold of motion should include time of observation as a variable. Disruption of the gravel imbrication at the bed surface was found to encourage particle movement. The effect of buried perforated pipes o.n reducing bed siltation was investigated at the time of the stability experiments. No beneficial effect on the siltation pattern could be found when well-graded fine material was added to the flume. Title: Stability of gravel at artificially created spawning beds in uncontrolled streams Author: Helland-Hansen, Erik Andreas Twenty-five gabion-type structures across the main stem and tributaries of the Siuslaw River in the Oregon Coastal Range, installed to expand the available spawning area for fish, were investigated for their ability to perform gravel control functions such as trapping bedload carried by the stream or holding gravel placed behind the structures. The merits of gravel trapping structures in the main stem Siuslaw River were found to depend largely on channel features in the reach at and above the structures. Factors favoring successful developments were: ample gravel supply, high bed roughness, wide straight reaches, and lateral stream bed slopes deflecting flood water from the structure. Among limiting factors were: the existence of pools immediately upstream of structures, deficient gravel supply, curving stream alignment, and unfavorable lateral stream bed slopes. Main stem reaches with an instantaneous peak discharge exceeding 100 cfs per foot width were found questionable for development. The controlling factors in the tributary streams were found to be approach velocities and stream features such as bedrock smoothness, approach slope, channel alignment, constrictions, lateral bed slope, plunge pools, and lengths of gravel beds. Careful placing of gravel to predetermined slopes was found not to be warranted, as the stream would rework the gravel according to local influences. Reaches where the flow was retarded without widening and reaches where high velocities occurred were found especially unfavorable for gravel stability. Flume studies with simulated gabions and full-size gravel were carried out to study incipient motion and scour from a gravel bed behind a gabion. Scour was found to take place from the upstream portion of the gravel bed, resulting in an adversely sloping bed there. Bed forms of standing-wave type, with changing wave location, were encountered when the flow was in the critical region; subsequent scour would wash the bed waves out. Gravel transport from apparently stable beds subjected to very low flow strengths verified that gravel transport is a statistical phenomenon and that the threshold of motion should include time of observation as a variable. Disruption of the gravel imbrication at the bed surface was found to encourage particle movement. The effect of buried perforated pipes o.n reducing bed siltation was investigated at the time of the stability experiments. No beneficial effect on the siltation pattern could be found when well-graded fine material was added to the flume. 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• 1534. [Article] Biostratigraphy, depositional environments, and paleogeography of Lower and Middle Devonian rocks, Death Valley area, California

  During Early and Middle Devonian time, the main part of the Death Valley area was characterized by shallow marine shelf position. In the extreme western part, deposition took place in carbonate slope environments. ...

  Citation × Citation Citation Abstract Copy Title: Biostratigraphy, depositional environments, and paleogeography of Lower and Middle Devonian rocks, Death Valley area, California Author: Heironimus, Thurman L. During Early and Middle Devonian time, the main part of the Death Valley area was characterized by shallow marine shelf position. In the extreme western part, deposition took place in carbonate slope environments. Early and Middle Devonian eastern platform dolomites, represented by uppermost Hidden Valley Dolomite and lower Lost Burro Formation, have been divided into six units in ascending order based on lithology, depositional environment, and age. The Lochkovian depositional setting was that of southeast to northwest transition from a broad inner platform to a narrow outer shelf basin. Unit 1 intertidal to very shallow subtidal sediments were deposited to the east, whereas a skeletal carbonate bank or reef complex fringing the platform edge supplied bioclastic material to extreme slope areas to the west. Late Lochkovian regression exposed extreme southeast thesis platform areas to erosion. A depositional hiatus marks the top of farther seaward Unit 1 platform areas in the northern Panamint Range. Unit 2 fossiliferous sediments were widely deposited throughout the thesis area during early Pragian transgression. Unit 2 correlative Sevy-like deposits in southeast areas at Bat Mountain and the Nopah Range mark the landward extent of initial marine onlap during this time. With increased input of clastic material into the normal marine environment, the Unit 2 lithotope was gradually replaced by Unit 3 silty and cherty argillaceous dolomites. The lower part of Unit 3 was deposited during continued marine transgression. The upper part reflects shallowing upward conditions and initiation of late Early Devonian regression. To the west, slope areas contain cherty argillaceous limestones correlative to Unit 3 and, similarly, indicate shallowing conditions. A beach-barrier bar complex, represented by sandy Unit 4 rocks, prograded seaward over nearshore Unit 3 sediments in response to marine offlap in late Early Devonian time. Unit 4 reflects an increased clastic sediment supply derived from erosion of cratonward strata, as well as marking regression. The seaward prograding sandy environment was followed and progressively overstepped by eastern intertidal-supratidal deposits, represented by Unit S coarse crystalline dolomite. Thinness and gradational lower contact of this lithology suggest that the transgressive part of coarse crystalline dolomite deposition seen in central Nevada may not be present in southeast California. Deposition of Unit 6 intertidal to shallow subtidal sediments during early Middle Devonian time records a gradual submergence of inner shelf regions by initial transgression. Rocks overlying Unit 6 in the thesis area reflect the larger transgressive pulse of the Taghanic onlap. Two distinct dolomite types are recognizable in the thesis area. Primary dolomite, represented by aphanitic, thinly laminated dolomite at the Nopah Range and Bat Mountain, was formed by penecontemporaneous replacement of calcareous sediment essentially at time of deposition. This dolomite type preserved microcrystalline textures, and fine sedimentary structures. The second dolomite type, eogenetic secondary dolomite, represents postdepositional near-surface replacement of limy sediments by slow growth and coalescence of dolomite crystals. This dolomite type characterizes the bulk of the carbonate interval studied. A favored mechanism for eogenetic secondary dolomite formation in the thesis area is that of mixing zone dolomitization, whereby meteoric freshwater mixes with intrastratal sea water in a seaward extending subsurface wedge. This dolomitizing zone moved seaward with marine regression and landward during transgression, leaving behind a blanket of dolomitized strata. Coarse crystalline dolomite in Unit 5 was extensively subjected to this paleogeographic-related dolomitizing environment. Title: Biostratigraphy, depositional environments, and paleogeography of Lower and Middle Devonian rocks, Death Valley area, California Author: Heironimus, Thurman L. During Early and Middle Devonian time, the main part of the Death Valley area was characterized by shallow marine shelf position. In the extreme western part, deposition took place in carbonate slope environments. Early and Middle Devonian eastern platform dolomites, represented by uppermost Hidden Valley Dolomite and lower Lost Burro Formation, have been divided into six units in ascending order based on lithology, depositional environment, and age. The Lochkovian depositional setting was that of southeast to northwest transition from a broad inner platform to a narrow outer shelf basin. Unit 1 intertidal to very shallow subtidal sediments were deposited to the east, whereas a skeletal carbonate bank or reef complex fringing the platform edge supplied bioclastic material to extreme slope areas to the west. Late Lochkovian regression exposed extreme southeast thesis platform areas to erosion. A depositional hiatus marks the top of farther seaward Unit 1 platform areas in the northern Panamint Range. Unit 2 fossiliferous sediments were widely deposited throughout the thesis area during early Pragian transgression. Unit 2 correlative Sevy-like deposits in southeast areas at Bat Mountain and the Nopah Range mark the landward extent of initial marine onlap during this time. With increased input of clastic material into the normal marine environment, the Unit 2 lithotope was gradually replaced by Unit 3 silty and cherty argillaceous dolomites. The lower part of Unit 3 was deposited during continued marine transgression. The upper part reflects shallowing upward conditions and initiation of late Early Devonian regression. To the west, slope areas contain cherty argillaceous limestones correlative to Unit 3 and, similarly, indicate shallowing conditions. A beach-barrier bar complex, represented by sandy Unit 4 rocks, prograded seaward over nearshore Unit 3 sediments in response to marine offlap in late Early Devonian time. Unit 4 reflects an increased clastic sediment supply derived from erosion of cratonward strata, as well as marking regression. The seaward prograding sandy environment was followed and progressively overstepped by eastern intertidal-supratidal deposits, represented by Unit S coarse crystalline dolomite. Thinness and gradational lower contact of this lithology suggest that the transgressive part of coarse crystalline dolomite deposition seen in central Nevada may not be present in southeast California. Deposition of Unit 6 intertidal to shallow subtidal sediments during early Middle Devonian time records a gradual submergence of inner shelf regions by initial transgression. Rocks overlying Unit 6 in the thesis area reflect the larger transgressive pulse of the Taghanic onlap. Two distinct dolomite types are recognizable in the thesis area. Primary dolomite, represented by aphanitic, thinly laminated dolomite at the Nopah Range and Bat Mountain, was formed by penecontemporaneous replacement of calcareous sediment essentially at time of deposition. This dolomite type preserved microcrystalline textures, and fine sedimentary structures. The second dolomite type, eogenetic secondary dolomite, represents postdepositional near-surface replacement of limy sediments by slow growth and coalescence of dolomite crystals. This dolomite type characterizes the bulk of the carbonate interval studied. A favored mechanism for eogenetic secondary dolomite formation in the thesis area is that of mixing zone dolomitization, whereby meteoric freshwater mixes with intrastratal sea water in a seaward extending subsurface wedge. This dolomitizing zone moved seaward with marine regression and landward during transgression, leaving behind a blanket of dolomitized strata. Coarse crystalline dolomite in Unit 5 was extensively subjected to this paleogeographic-related dolomitizing environment. Close

• 1535. [Article] Silicic acid and oxidizable carbon movement in a Walla Walla silt loam as related to long-term residue and nitrogen applications

  Intensive cultivation of Walla Walla silt loams (coarse silty, mixed, mesic, typic Haploxeroll) in eastern Oregon and Washington during the past 50 years, has decreased internal soil drainage in the 15 ...

  Citation × Citation Citation Abstract Copy Title: Silicic acid and oxidizable carbon movement in a Walla Walla silt loam as related to long-term residue and nitrogen applications Author: Douglas, Clyde Lee Intensive cultivation of Walla Walla silt loams (coarse silty, mixed, mesic, typic Haploxeroll) in eastern Oregon and Washington during the past 50 years, has decreased internal soil drainage in the 15 to 40 cm layer. However, no measurements have been made to determine the causes and corrective management for this internal drainage problem. Gradual acidification of the plow layer, partially as a result of long-term use of nitrogen fertilizers in a summer-fallow management system may possibly have contributed to release of soil constituents that contribute to cementation of a high strength soil layer of variable thickness found at depths from 15 to 40 cm. Therefore, the potential for release, and possible interactions, of silicic acid, organic carbon, and major cations from the plow layer and subsequent movement through or desposition in layers below were evaluated. The test soils came from selected plots subjected to residue and nitrogen addition treatments for a period of 50 years. Samples were taken from the four upper 15-cm layers of a Walla Walla silt loam, placed in a system of laboratory columns, and leached with distilled water. The columns were designed to simulate a leaching soil profile and to facilitate continuous collection of leachate for analysis. Results indicate that soluble silica concentrations in Walla Walla soils are high in comparison to soils of the United States found outside of the Pacific Northwest. When no silica enters a layer (the 0 to 15-cm layer) silicic acid concentration in the leachate increases as original soil pH decreases. When the input fluid contained silicic acid, as in all layers below 15 cm, there was a smaller trend for increasing silicic acid concentration with decreasing soil pH. Silicic acid release from the 0 to 15-cm layer was decreased 24% by addition of large amounts of organic material, and 32% by the addition of lime compared to other treatments with lower soil pH values. All management systems showed a net release of silicic acid from the 0 to 15-cm layer and a net gain in each 15 cm layer below to a depth of 60 cm. Maximum release was 4.3 x 10⁻² mol H₄S10₄/m of liquid depth and maximum gain was 2.7 x 10⁻² mol H₄SiO₄/m of liquid depth, both in the plot treated with 45 kg N/hayr. Silicic acid concentration and transfer were each correlated (R² = 0.99 and 0.87, respectively) with both soil pH and long-term carbon additions to the soil surface. Soluble carbon also gave a release and movement response with a maximum net release of 1.3 x 10 ⁻¹ mo1 C/m of liquid depth and a maximum gain of 7.2 x 10 ⁻² mol C/m of liquid depth. However, there were no significant correlations of either soluble organic carbon or major cations with silicic acid release or retention. Silicic acid solubility increases with increasing soil acidity. More silicic acid leaves the plow layer thereby increasing the potential for adsorption or deposition in lower layers. Desorption, movement and sorption of silicic acid may affect such soil physical and chemical properties as hydraulic conductivity and cementation. Because silicic acid in soil solutions, and associated movement, is susceptible to changes in soil management, silica solubility effects on soil physical properties deserves more attention. Title: Silicic acid and oxidizable carbon movement in a Walla Walla silt loam as related to long-term residue and nitrogen applications Author: Douglas, Clyde Lee Intensive cultivation of Walla Walla silt loams (coarse silty, mixed, mesic, typic Haploxeroll) in eastern Oregon and Washington during the past 50 years, has decreased internal soil drainage in the 15 to 40 cm layer. However, no measurements have been made to determine the causes and corrective management for this internal drainage problem. Gradual acidification of the plow layer, partially as a result of long-term use of nitrogen fertilizers in a summer-fallow management system may possibly have contributed to release of soil constituents that contribute to cementation of a high strength soil layer of variable thickness found at depths from 15 to 40 cm. Therefore, the potential for release, and possible interactions, of silicic acid, organic carbon, and major cations from the plow layer and subsequent movement through or desposition in layers below were evaluated. The test soils came from selected plots subjected to residue and nitrogen addition treatments for a period of 50 years. Samples were taken from the four upper 15-cm layers of a Walla Walla silt loam, placed in a system of laboratory columns, and leached with distilled water. The columns were designed to simulate a leaching soil profile and to facilitate continuous collection of leachate for analysis. Results indicate that soluble silica concentrations in Walla Walla soils are high in comparison to soils of the United States found outside of the Pacific Northwest. When no silica enters a layer (the 0 to 15-cm layer) silicic acid concentration in the leachate increases as original soil pH decreases. When the input fluid contained silicic acid, as in all layers below 15 cm, there was a smaller trend for increasing silicic acid concentration with decreasing soil pH. Silicic acid release from the 0 to 15-cm layer was decreased 24% by addition of large amounts of organic material, and 32% by the addition of lime compared to other treatments with lower soil pH values. All management systems showed a net release of silicic acid from the 0 to 15-cm layer and a net gain in each 15 cm layer below to a depth of 60 cm. Maximum release was 4.3 x 10⁻² mol H₄S10₄/m of liquid depth and maximum gain was 2.7 x 10⁻² mol H₄SiO₄/m of liquid depth, both in the plot treated with 45 kg N/hayr. Silicic acid concentration and transfer were each correlated (R² = 0.99 and 0.87, respectively) with both soil pH and long-term carbon additions to the soil surface. Soluble carbon also gave a release and movement response with a maximum net release of 1.3 x 10 ⁻¹ mo1 C/m of liquid depth and a maximum gain of 7.2 x 10 ⁻² mol C/m of liquid depth. However, there were no significant correlations of either soluble organic carbon or major cations with silicic acid release or retention. Silicic acid solubility increases with increasing soil acidity. More silicic acid leaves the plow layer thereby increasing the potential for adsorption or deposition in lower layers. Desorption, movement and sorption of silicic acid may affect such soil physical and chemical properties as hydraulic conductivity and cementation. Because silicic acid in soil solutions, and associated movement, is susceptible to changes in soil management, silica solubility effects on soil physical properties deserves more attention. Close

• 1536. [Article] Stability of rainbow trout (Salmo gairdneri) muscle lysosomes

  Studies were conducted to determine the post-mortem stability of lysosomes in the white muscle of rainbow trout (Salmo gairdneri) and to determine whether lysosomal stability was related to rigor mortis ...

  Citation × Citation Citation Abstract Copy Title: Stability of rainbow trout (Salmo gairdneri) muscle lysosomes Author: Whiting, Richard Charles Studies were conducted to determine the post-mortem stability of lysosomes in the white muscle of rainbow trout (Salmo gairdneri) and to determine whether lysosomal stability was related to rigor mortis and its subsequent dissolution. In addition, isolated lysosomes were subjected to different environments in an attempt to detect some of the factors that might influence their stability. After slaughter, fish were aged at either 4 or 15. Muscle samples were excised from each fish 1 hr post-mortem, during rigor mortis, soon after the dissolution of rigor mortis, and after a period of aging. Lysosonnes were extracted by blending the muscle in 0. 25 M sucrose-0.175 M KC1-1 mM EDTA in a solution:muscle ratio of 4:1. After blending, the mixture was centrifuged at 1000 x G to sediment the nuclear-debris pellet, followed by centrifugation of the supernatant at 27,000 x G to obtain a lysosomal pellet and a supernatant containing the soluble enzymes. The distribution of the lysosomal enzymes, cathepsin and α-glucosidase, was measured in each of the above fractions at each sampling interval. The stability of lysosomes was thus followed by monitoring the release of these lysosomal enzymes with time. The lysosomal pellet extracted at 1 hr post-naortem contained 23% of the catheptic activity of the muscle. This percentage decreased to approximately 15% by the end of rigor mortis with small changes noted thereafter. The nuclear-debris pellet contained a relatively constant amount of catheptic activity, generally 55-65%, while the soluble activity increased with decreasing lysosomal activity. Approximately one-third of the extractable lysosomes appeared to rupture and release catheptic enzymes before or during rigor mortis. Freezing and thawing the muscle four times reduced the catheptic activity in the lysosomal pellet to 8% of the total activity and increased the soluble activity to 51%. Isolated lysosomes rapidly released their enzymes in response to environmental conditions, but once adjusted they were relatively stable. Seventy-five percent of the cathepsins from lysosomes suspended in 0.25 M sucrose-0.005 M phosphate buffer (pH 6.5) at 4° remained sedimentable for 105 hr. Increasing the sucrose concentration toward 0.5 M and decreasing the incubation temperature increased the stability. The minimum release of the enzymes occurred between pH 6 and 7. Addition of salts (NaCl, KCl, CaCl₂) decreased the initial solubilization of the enzymes, but appeared to increase solubilization over a 70 hr incubation. Ca⁺² was more effective in producing this pattern than Na⁺. Fish saline had little protective effect relative to distilled water. The detergent Triton X-100 caused nearly complete solubilization of the enzyme. The solubilization of α-glucosidase in response to incubation conditions paralleled that of cathepsin but was invariably greater. This suggested that the enzymes have different binding affinities with the membrane surface. However, when the changing distribution of the two enzynnes was determined in aging muscle, an identical pattern resulted. Title: Stability of rainbow trout (Salmo gairdneri) muscle lysosomes Author: Whiting, Richard Charles Studies were conducted to determine the post-mortem stability of lysosomes in the white muscle of rainbow trout (Salmo gairdneri) and to determine whether lysosomal stability was related to rigor mortis and its subsequent dissolution. In addition, isolated lysosomes were subjected to different environments in an attempt to detect some of the factors that might influence their stability. After slaughter, fish were aged at either 4 or 15. Muscle samples were excised from each fish 1 hr post-mortem, during rigor mortis, soon after the dissolution of rigor mortis, and after a period of aging. Lysosonnes were extracted by blending the muscle in 0. 25 M sucrose-0.175 M KC1-1 mM EDTA in a solution:muscle ratio of 4:1. After blending, the mixture was centrifuged at 1000 x G to sediment the nuclear-debris pellet, followed by centrifugation of the supernatant at 27,000 x G to obtain a lysosomal pellet and a supernatant containing the soluble enzymes. The distribution of the lysosomal enzymes, cathepsin and α-glucosidase, was measured in each of the above fractions at each sampling interval. The stability of lysosomes was thus followed by monitoring the release of these lysosomal enzymes with time. The lysosomal pellet extracted at 1 hr post-naortem contained 23% of the catheptic activity of the muscle. This percentage decreased to approximately 15% by the end of rigor mortis with small changes noted thereafter. The nuclear-debris pellet contained a relatively constant amount of catheptic activity, generally 55-65%, while the soluble activity increased with decreasing lysosomal activity. Approximately one-third of the extractable lysosomes appeared to rupture and release catheptic enzymes before or during rigor mortis. Freezing and thawing the muscle four times reduced the catheptic activity in the lysosomal pellet to 8% of the total activity and increased the soluble activity to 51%. Isolated lysosomes rapidly released their enzymes in response to environmental conditions, but once adjusted they were relatively stable. Seventy-five percent of the cathepsins from lysosomes suspended in 0.25 M sucrose-0.005 M phosphate buffer (pH 6.5) at 4° remained sedimentable for 105 hr. Increasing the sucrose concentration toward 0.5 M and decreasing the incubation temperature increased the stability. The minimum release of the enzymes occurred between pH 6 and 7. Addition of salts (NaCl, KCl, CaCl₂) decreased the initial solubilization of the enzymes, but appeared to increase solubilization over a 70 hr incubation. Ca⁺² was more effective in producing this pattern than Na⁺. Fish saline had little protective effect relative to distilled water. The detergent Triton X-100 caused nearly complete solubilization of the enzyme. The solubilization of α-glucosidase in response to incubation conditions paralleled that of cathepsin but was invariably greater. This suggested that the enzymes have different binding affinities with the membrane surface. However, when the changing distribution of the two enzynnes was determined in aging muscle, an identical pattern resulted. Close

• 1537. [Article] Permeability properties of an edible methylcellulose-palmitic acid film

  The use of edible coatings in combination with antimicrobial agents enhances the microbial stability of foods. In this study we evaluated the potassium sorbate and sorbic acid permeability of an edible ...

  Citation × Citation Citation Abstract Copy Title: Permeability properties of an edible methylcellulose-palmitic acid film Author: Rico-Pena, Delmy del Carmen The use of edible coatings in combination with antimicrobial agents enhances the microbial stability of foods. In this study we evaluated the potassium sorbate and sorbic acid permeability of an edible methylcellulose (MC) - palmitic acid (PA) film with a MC:PA ratio of 3:1. Permeability cell measurements were used to evaluate the effect of pH and water activity (a [subscript w]) on the film permeation rate by sorbic acid and potassium sorbate. For films with a thickness of 55-66 pm, potassium sorbate permeability increased from 2.3x10⁻¹⁰ to 2.0x10⁻⁸ (mg/sec cm²)/(cm)/(mg/mL) as a [subscript w] increased from 0.65 to 0.80. Films were not stable at a [subscript w] levels above 0.80. The permeability of the film to sorbic acid decreased from 3.3x10⁻⁸ to 9.1x10⁻¹⁰ (mg/sec cm²) (cm)/(mg/mL) when pH in the permeability cell was increased from 3 to 7. This permeability decrease with pH could balance the loss of effectiveness of sorbates due to the lowering of the percentage of undissociated molecules at high pH. Another characterization of the MC-PA film was the evaluation of the effect of relative humidity (RH) on its oxygen transmission rate (OTR). In general, the film was highly permeable to oxygen (OTR values at 24°C, 660 to 1400 mL O₂ (STP)/m² 24h atm, average film thickness of 55 μm). Therefore, there is no risk to develop anaerobic conditions on food surfaces coated with the MC-PA film. There was no relative humidity effect on OTR in the 0-60% RH range; whereas, the OTR doubled when the RH was increased from 60 to 80%. These results agree well with the moisture uptake of the MC-PA film. Its moisture sorption isotherm shows a large moisture content increase at RH levels larger than 60%. The application of methylcellulose-based films as moisture permeability barriers in simulated sundae ice cream cones showed that a MC-PA film practically stopped moisture transfer from the ice cream to the sugar cone. Sugar cone crispness was retained for a period longer than three months when stored coated at -10°F and +10°F. The crispness of commercial sundae ice cream cones is retained for periods much less than three months. Title: Permeability properties of an edible methylcellulose-palmitic acid film Author: Rico-Pena, Delmy del Carmen The use of edible coatings in combination with antimicrobial agents enhances the microbial stability of foods. In this study we evaluated the potassium sorbate and sorbic acid permeability of an edible methylcellulose (MC) - palmitic acid (PA) film with a MC:PA ratio of 3:1. Permeability cell measurements were used to evaluate the effect of pH and water activity (a [subscript w]) on the film permeation rate by sorbic acid and potassium sorbate. For films with a thickness of 55-66 pm, potassium sorbate permeability increased from 2.3x10⁻¹⁰ to 2.0x10⁻⁸ (mg/sec cm²)/(cm)/(mg/mL) as a [subscript w] increased from 0.65 to 0.80. Films were not stable at a [subscript w] levels above 0.80. The permeability of the film to sorbic acid decreased from 3.3x10⁻⁸ to 9.1x10⁻¹⁰ (mg/sec cm²) (cm)/(mg/mL) when pH in the permeability cell was increased from 3 to 7. This permeability decrease with pH could balance the loss of effectiveness of sorbates due to the lowering of the percentage of undissociated molecules at high pH. Another characterization of the MC-PA film was the evaluation of the effect of relative humidity (RH) on its oxygen transmission rate (OTR). In general, the film was highly permeable to oxygen (OTR values at 24°C, 660 to 1400 mL O₂ (STP)/m² 24h atm, average film thickness of 55 μm). Therefore, there is no risk to develop anaerobic conditions on food surfaces coated with the MC-PA film. There was no relative humidity effect on OTR in the 0-60% RH range; whereas, the OTR doubled when the RH was increased from 60 to 80%. These results agree well with the moisture uptake of the MC-PA film. Its moisture sorption isotherm shows a large moisture content increase at RH levels larger than 60%. The application of methylcellulose-based films as moisture permeability barriers in simulated sundae ice cream cones showed that a MC-PA film practically stopped moisture transfer from the ice cream to the sugar cone. Sugar cone crispness was retained for a period longer than three months when stored coated at -10°F and +10°F. The crispness of commercial sundae ice cream cones is retained for periods much less than three months. Close

• 1538. [Article] Factors affecting germination of endomycorrhizal spores

  Four isolates of Glomus mosseae, collected from diverse geographic locations, were pot cultured on varied host plants or stored in the same soil as collected. Spores of three isolates failed to germinate ...

  Citation × Citation Citation Abstract Copy Title: Factors affecting germination of endomycorrhizal spores Author: Daniels, Barbara Ann Four isolates of Glomus mosseae, collected from diverse geographic locations, were pot cultured on varied host plants or stored in the same soil as collected. Spores of three isolates failed to germinate on any of five agar media while the fourth germinated well on all media. Lack of germination on agar media was not attributable to lack of viability as spores of all four isolates germinated when enclosed in nylon screen bags and buried in pasteurized soil mix containing a coleus plant. Scanning electron micrographs determined that morphological characteristics of the four isolates differed as well. A new endomycorrhizal species, Glomus epigaeus, produces abundant chlamydospores in sporocarps on the soil surface. This species has been maintained for more than 1 year in pot culture on various hosts and produces 8-15 sporocarps monthly from each pot. A simple technique of shaking sporocarps in water with broken glass chips is described for the separation of spores from sporocarps. The epigeous habit, narrow, thin-walled, inserted hyphal attachment and bright yellow to yellow brown wall color in transmitted light separate G. epigaeus from Glomus macrocarpus, which is not known to fruit epigeously and has a much broader, thick-walled, noninserted hyphal attachment and brown wall color in transmitted light. The influence of physical and chemical factors on germination of Glomus epigaeus spores was tested in nonsterile soil. Soil moisture, temperature, and to a lesser degree, pH, appear to influence germination, while the levels of soil fertility and spore density tested had little or no effect. Maximum spore germination occurred in soil at or above field capacity, between 18-25° C and between 6-8 pH. These conditions seem closely related to the conditions optimal for growth of many host plants, and this relationship is discussed. Spore germination of Glomus epigaeus was completely inhibited in forest, dune and agricultural soils which were autoclaved, and in Chehalis silt loam which was gamma-irradiated or pasteurized as well as autoclaved. However, 65-80% germination occurred in most nonsterile soils, autoclaved or nonsterile kaolin and activated charcoal. Similar levels of germination occurred on nonsterile Chehalis silt loam containing nonmycorrhizal, ectomycorrhizal and VA mycorrhizal seedlings, although penetration and infection was evident only in VA mycorrhizal host seedlings. Title: Factors affecting germination of endomycorrhizal spores Author: Daniels, Barbara Ann Four isolates of Glomus mosseae, collected from diverse geographic locations, were pot cultured on varied host plants or stored in the same soil as collected. Spores of three isolates failed to germinate on any of five agar media while the fourth germinated well on all media. Lack of germination on agar media was not attributable to lack of viability as spores of all four isolates germinated when enclosed in nylon screen bags and buried in pasteurized soil mix containing a coleus plant. Scanning electron micrographs determined that morphological characteristics of the four isolates differed as well. A new endomycorrhizal species, Glomus epigaeus, produces abundant chlamydospores in sporocarps on the soil surface. This species has been maintained for more than 1 year in pot culture on various hosts and produces 8-15 sporocarps monthly from each pot. A simple technique of shaking sporocarps in water with broken glass chips is described for the separation of spores from sporocarps. The epigeous habit, narrow, thin-walled, inserted hyphal attachment and bright yellow to yellow brown wall color in transmitted light separate G. epigaeus from Glomus macrocarpus, which is not known to fruit epigeously and has a much broader, thick-walled, noninserted hyphal attachment and brown wall color in transmitted light. The influence of physical and chemical factors on germination of Glomus epigaeus spores was tested in nonsterile soil. Soil moisture, temperature, and to a lesser degree, pH, appear to influence germination, while the levels of soil fertility and spore density tested had little or no effect. Maximum spore germination occurred in soil at or above field capacity, between 18-25° C and between 6-8 pH. These conditions seem closely related to the conditions optimal for growth of many host plants, and this relationship is discussed. Spore germination of Glomus epigaeus was completely inhibited in forest, dune and agricultural soils which were autoclaved, and in Chehalis silt loam which was gamma-irradiated or pasteurized as well as autoclaved. However, 65-80% germination occurred in most nonsterile soils, autoclaved or nonsterile kaolin and activated charcoal. Similar levels of germination occurred on nonsterile Chehalis silt loam containing nonmycorrhizal, ectomycorrhizal and VA mycorrhizal seedlings, although penetration and infection was evident only in VA mycorrhizal host seedlings. Close

• 1539. [Article] Spatial distribution and the probability of occurrence of beluga whales (Delphinapterus leucas) in Alaskan Arctic

  The known distribution of beluga whales ranges from sub-Arctic to Arctic waters where they migrate in pods in response to environmental factors such as the presence of sea ice and prey. This study uses ...

  Citation × Citation Citation Abstract Copy Title: Spatial distribution and the probability of occurrence of beluga whales (Delphinapterus leucas) in Alaskan Arctic Author: Romeo, Lucy F. The known distribution of beluga whales ranges from sub-Arctic to Arctic waters where they migrate in pods in response to environmental factors such as the presence of sea ice and prey. This study uses bivariate and multivariate analysis techniques to measure how environmental covariates are associated with the spatial-temporal distribution of beluga whales. Exploratory data analysis was used to determine the relationship among environmental covariates: bathymetry, slope, sea surface temperature, and distance to sea ice. Spatial analyses were used to determine the probability of occurrence of beluga whales in the northeastern Chukchi and southwestern Beaufort seas, based on each environmental covariate for the autumn months of the two study periods, from 2000 to 2006 and from 2008 to 2012. Findings from this study suggest that correlations exist between SST and distance to sea ice, and depth and distance to sea ice, and that beluga whales may prefer areas of relatively steep slope and associated increasing depth along the continental slope. Probability of occurrence maps were created for September and October for each year, based on beluga whale preference and avoidance for each environmental covariate. Areas of preference, or high probability of occurrence, had more beluga whale sightings than expected. And areas of avoidance, or low probability of occurrence, had less beluga whale sightings than expected. Model validation included randomly dividing observational data from September of 2011 into a training (70%) and testing (30%) dataset, then creating a probability of occurrence model based on the training dataset and comparing the results to the locations of the testing dataset. Outputs from the analyses can help guide studies of beluga environmental covariate preferences and the possible influences on their occurrence. Better understanding of the spatial distribution of beluga whales can provide a tool for better management practices. Improved practices in management and conservation of habitat for beluga whales will impact indigenous communities who rely on marine mammals as cultural and consumable resources. Title: Spatial distribution and the probability of occurrence of beluga whales (Delphinapterus leucas) in Alaskan Arctic Author: Romeo, Lucy F. The known distribution of beluga whales ranges from sub-Arctic to Arctic waters where they migrate in pods in response to environmental factors such as the presence of sea ice and prey. This study uses bivariate and multivariate analysis techniques to measure how environmental covariates are associated with the spatial-temporal distribution of beluga whales. Exploratory data analysis was used to determine the relationship among environmental covariates: bathymetry, slope, sea surface temperature, and distance to sea ice. Spatial analyses were used to determine the probability of occurrence of beluga whales in the northeastern Chukchi and southwestern Beaufort seas, based on each environmental covariate for the autumn months of the two study periods, from 2000 to 2006 and from 2008 to 2012. Findings from this study suggest that correlations exist between SST and distance to sea ice, and depth and distance to sea ice, and that beluga whales may prefer areas of relatively steep slope and associated increasing depth along the continental slope. Probability of occurrence maps were created for September and October for each year, based on beluga whale preference and avoidance for each environmental covariate. Areas of preference, or high probability of occurrence, had more beluga whale sightings than expected. And areas of avoidance, or low probability of occurrence, had less beluga whale sightings than expected. Model validation included randomly dividing observational data from September of 2011 into a training (70%) and testing (30%) dataset, then creating a probability of occurrence model based on the training dataset and comparing the results to the locations of the testing dataset. Outputs from the analyses can help guide studies of beluga environmental covariate preferences and the possible influences on their occurrence. Better understanding of the spatial distribution of beluga whales can provide a tool for better management practices. Improved practices in management and conservation of habitat for beluga whales will impact indigenous communities who rely on marine mammals as cultural and consumable resources. Close

• 1540. [Article] Groundwater flow and radionuclide transport in fault zones in granitic rock

  Fault zones are potential paths for release of radioactive nuclides from radioactive-waste repositories in granitic rock. This research considers detailed maps of en echelon fault zones at two sites in ...

  Citation × Citation Citation Abstract Copy Title: Groundwater flow and radionuclide transport in fault zones in granitic rock Author: Geier, Joel E. Fault zones are potential paths for release of radioactive nuclides from radioactive-waste repositories in granitic rock. This research considers detailed maps of en echelon fault zones at two sites in southern Sweden, as a basis for analyses of how their internal geometry can influence groundwater flow and transport of radioactive nuclides. Fracture intensity within these zones is anisotropic and correlated over scales of several meters along strike, corresponding to the length and spacing of the en echelon steps. Flow modeling indicates these properties lead to correlation of zone transmissivity over similar scales. Intensity of fractures in the damage zone adjoining en echelon segments decreases exponentially with distance. These fractures are linked to en echelon segments as a hierarchical pattern of branches. Echelon steps also show a hierarchical internal structure. These traits suggest a fractal increase in the amount of pore volume that solute can access by diffusive mass transfer, with increasing distance from en echelon segments. Consequences may include tailing of solute breakthrough curves, similar to that observed in underground tracer experiments at one of the mapping sites. The implications of echelon-zone architecture are evaluated by numerical simulation of flow and solute transport in 2-D network models, including deterministic models based directly on mapping data, and a statistical model. The simulations account for advection, diffusion-controlled mixing across streamlines within fractures and at intersections, and diffusion into both stagnant branch fractures and macroscopically unfractured matrix. The simulations show that secondary fractures contribute to retardation of solute, although their net effect is sensitive to assumptions regarding heterogeneity of transmissivity and transport aperture. Detailed results provide insight into the function of secondary fractures as an immobile domain affecting mass transfer on time scales relevant to field characterization and repository safety assessment. In practical terms, secondary fractures in these en echelon zones are not indicated to limit release of radiation to the surface environment, to a degree that is significant for improving repository safety. Thus en echelon zones are to be regarded as detrimental geologic features, with potentially complex transport behavior which should be considered in the interpretation of in-situ experiments. Title: Groundwater flow and radionuclide transport in fault zones in granitic rock Author: Geier, Joel E. Fault zones are potential paths for release of radioactive nuclides from radioactive-waste repositories in granitic rock. This research considers detailed maps of en echelon fault zones at two sites in southern Sweden, as a basis for analyses of how their internal geometry can influence groundwater flow and transport of radioactive nuclides. Fracture intensity within these zones is anisotropic and correlated over scales of several meters along strike, corresponding to the length and spacing of the en echelon steps. Flow modeling indicates these properties lead to correlation of zone transmissivity over similar scales. Intensity of fractures in the damage zone adjoining en echelon segments decreases exponentially with distance. These fractures are linked to en echelon segments as a hierarchical pattern of branches. Echelon steps also show a hierarchical internal structure. These traits suggest a fractal increase in the amount of pore volume that solute can access by diffusive mass transfer, with increasing distance from en echelon segments. Consequences may include tailing of solute breakthrough curves, similar to that observed in underground tracer experiments at one of the mapping sites. The implications of echelon-zone architecture are evaluated by numerical simulation of flow and solute transport in 2-D network models, including deterministic models based directly on mapping data, and a statistical model. The simulations account for advection, diffusion-controlled mixing across streamlines within fractures and at intersections, and diffusion into both stagnant branch fractures and macroscopically unfractured matrix. The simulations show that secondary fractures contribute to retardation of solute, although their net effect is sensitive to assumptions regarding heterogeneity of transmissivity and transport aperture. Detailed results provide insight into the function of secondary fractures as an immobile domain affecting mass transfer on time scales relevant to field characterization and repository safety assessment. In practical terms, secondary fractures in these en echelon zones are not indicated to limit release of radiation to the surface environment, to a degree that is significant for improving repository safety. Thus en echelon zones are to be regarded as detrimental geologic features, with potentially complex transport behavior which should be considered in the interpretation of in-situ experiments. Close