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James P Mccalpin - One of the best experts on this subject based on the ideXlab platform.

  • sedimentology of fault scarp derived Colluvium from the 1983 borah peak rupture central idaho
    Journal of Sedimentary Research, 1993
    Co-Authors: James P Mccalpin, Witold Zuchiewicz, L Allen C Jones
    Abstract:

    ABSTRACT Ten undisturbed samples of scarp-derived Colluvium from the 1983 Borah Peak, Idaho, fault scarp were subjected to laboratory grain-size and fabric measurements to characterize typical Colluvium from a Basin and Range fault scarp. Colluvial deposits consisted of poorly-sorted pebble gravels (mean diameter -0.3 to -3.75 ; 1.2 to 13.5 mm) with 25-79% matrix (< 4 mm). Stereograms of long-axis orientations of 115 clasts from each colluvial wedge yielded girdle-type distributions, with typical eigenvalue ratios of In S1/S2 = 0.05-0.50 and In S2/S3 = 0.3-1.0 These girdle distributions indicate preferred orientation in angle-of-repose planes coincident with colluvial wedge depositional planes. Short-axis stereograms display single or du l maxima with mean bearing parallel to transport direction and plunge perpendicular to the colluvial wedge surface. Clast fabric strength is not strongly correlated with scarp aspect (corr. coeff. = 0.03 to 0.68) or with the slope of the faulted geomorphic surface (corr. coeff. = -0.16 to +0.57), but it improves with increasing matrix content (corr. coeff. = -0.04 to -0.42). Fabrics in measured wedges are weaker than those reported for other Colluviums and talus and resemble fabrics in debris flows. However, the stronger girdle tendencies and distinct orientation subgroups in scarp-derived Colluvium should distinguish it from suspected debris flow deposits in fault-zone exposures.

  • thermoluminescence dating of fault scarp derived Colluvium deciphering the timing of paleoearthquakes on the weber segment of the wasatch fault zone north central utah
    Journal of Geophysical Research, 1991
    Co-Authors: Steven L Forman, Alan R Nelson, James P Mccalpin
    Abstract:

    The timing of middle to late Holocene faulting on the Weber segment of the Wasatch fault zone, Utah, is constrained by thermoluminescence (TL) and radiocarbon age estimates on fine-grained, fault-related colluvial sediments. The stratigraphy in two trenches excavated across fault scarps is characterized by a stack of three colluvial wedges, deposited in response to three separate faulting events, the oldest of which buried a soil developed on a middle Holocene debris flow. Thermoluminescence age estimates by the partial and total bleach methods and the regeneration method on fine-grained Colluvium from the trenches agree within 1 sigma and are concordant with the radiocarbon chronology. A synthesis of the TL and 14C age estimates indicate that these three faulting events occurred sometime between 4500 and 3500, between 3200 and 2500, and between 1400 and 1000 years ago. Detailed investigation of a sequence of fine-grained, scarp-derived distal Colluvium shows that much of the sediment was deposited during <600-year intervals immediately after faulting. The sedimentation rate of Colluvium is inferred to increase shortly after faulting, and TL dating of these sediments provides additional information to constrain the timing of faulting events.

  • Thermoluminescence dating of fault-scarp-derived Colluvium: Deciphering the timing of paleoearthquakes on the Weber Segment of the Wasatch Fault Zone, north central Utah
    Journal of Geophysical Research, 1991
    Co-Authors: Steven L Forman, Alan R Nelson, James P Mccalpin
    Abstract:

    The timing of middle to late Holocene faulting on the Weber segment of the Wasatch fault zone, Utah, is constrained by thermoluminescence (TL) and radiocarbon age estimates on fine-grained, fault-related colluvial sediments. The stratigraphy in two trenches excavated across fault scarps is characterized by a stack of three colluvial wedges, deposited in response to three separate faulting events, the oldest of which buried a soil developed on a middle Holocene debris flow. Thermoluminescence age estimates by the partial and total bleach methods and the regeneration method on fine-grained Colluvium from the trenches agree within 1 sigma and are concordant with the radiocarbon chronology. A synthesis of the TL and 14C age estimates indicate that these three faulting events occurred sometime between 4500 and 3500, between 3200 and 2500, and between 1400 and 1000 years ago. Detailed investigation of a sequence of fine-grained, scarp-derived distal Colluvium shows that much of the sediment was deposited during

Steven L Forman - One of the best experts on this subject based on the ideXlab platform.

  • thermoluminescence dating of fault scarp derived Colluvium deciphering the timing of paleoearthquakes on the weber segment of the wasatch fault zone north central utah
    Journal of Geophysical Research, 1991
    Co-Authors: Steven L Forman, Alan R Nelson, James P Mccalpin
    Abstract:

    The timing of middle to late Holocene faulting on the Weber segment of the Wasatch fault zone, Utah, is constrained by thermoluminescence (TL) and radiocarbon age estimates on fine-grained, fault-related colluvial sediments. The stratigraphy in two trenches excavated across fault scarps is characterized by a stack of three colluvial wedges, deposited in response to three separate faulting events, the oldest of which buried a soil developed on a middle Holocene debris flow. Thermoluminescence age estimates by the partial and total bleach methods and the regeneration method on fine-grained Colluvium from the trenches agree within 1 sigma and are concordant with the radiocarbon chronology. A synthesis of the TL and 14C age estimates indicate that these three faulting events occurred sometime between 4500 and 3500, between 3200 and 2500, and between 1400 and 1000 years ago. Detailed investigation of a sequence of fine-grained, scarp-derived distal Colluvium shows that much of the sediment was deposited during <600-year intervals immediately after faulting. The sedimentation rate of Colluvium is inferred to increase shortly after faulting, and TL dating of these sediments provides additional information to constrain the timing of faulting events.

  • Thermoluminescence dating of fault-scarp-derived Colluvium: Deciphering the timing of paleoearthquakes on the Weber Segment of the Wasatch Fault Zone, north central Utah
    Journal of Geophysical Research, 1991
    Co-Authors: Steven L Forman, Alan R Nelson, James P Mccalpin
    Abstract:

    The timing of middle to late Holocene faulting on the Weber segment of the Wasatch fault zone, Utah, is constrained by thermoluminescence (TL) and radiocarbon age estimates on fine-grained, fault-related colluvial sediments. The stratigraphy in two trenches excavated across fault scarps is characterized by a stack of three colluvial wedges, deposited in response to three separate faulting events, the oldest of which buried a soil developed on a middle Holocene debris flow. Thermoluminescence age estimates by the partial and total bleach methods and the regeneration method on fine-grained Colluvium from the trenches agree within 1 sigma and are concordant with the radiocarbon chronology. A synthesis of the TL and 14C age estimates indicate that these three faulting events occurred sometime between 4500 and 3500, between 3200 and 2500, and between 1400 and 1000 years ago. Detailed investigation of a sequence of fine-grained, scarp-derived distal Colluvium shows that much of the sediment was deposited during

Willy A Lacerda - One of the best experts on this subject based on the ideXlab platform.

  • subsurface hydrology of layered Colluvium mantles in unchannelled valleys south eastern brazil
    Earth Surface Processes and Landforms, 1994
    Co-Authors: Nelson Ferreira Fernandes, Ana Luiza Coelho Netto, Willy A Lacerda
    Abstract:

    The effects of subsurface hydrology on the evolution of erosive processes inside layered Colluvium mantles in unchannelled valleys are investigated. Tensiometer nests are installed in different morphological conditions with their specific depths controlled by the subsurface structure of the Colluvium mantle. Daily readings (during one year) and physical and mechanical analyses of the different Colluvium layers are carried out. In spite of a highly discontinuous subsurface structure, present topography is the major factor controlling subsurface flow in this landscape. Paleotopographic features, usually resulting from the lateral mobilization of the previous topographic hollow axis, can locally control the preferential expansion of the saturated zone towards areas other than the present hollow axis. During rainy periods, pressure head at the base of the hollow axis increases towards a maximum value which is not increased by subsequent precipitation inputs. New water input is dissipated by direct precipitation onto the saturated zone and exfiltration by seepage at the gully head walls, precluding the development of the excess pore pressures required to trigger failure by landsliding.

Nelson Ferreira Fernandes - One of the best experts on this subject based on the ideXlab platform.

  • subsurface hydrology of layered Colluvium mantles in unchannelled valleys south eastern brazil
    Earth Surface Processes and Landforms, 1994
    Co-Authors: Nelson Ferreira Fernandes, Ana Luiza Coelho Netto, Willy A Lacerda
    Abstract:

    The effects of subsurface hydrology on the evolution of erosive processes inside layered Colluvium mantles in unchannelled valleys are investigated. Tensiometer nests are installed in different morphological conditions with their specific depths controlled by the subsurface structure of the Colluvium mantle. Daily readings (during one year) and physical and mechanical analyses of the different Colluvium layers are carried out. In spite of a highly discontinuous subsurface structure, present topography is the major factor controlling subsurface flow in this landscape. Paleotopographic features, usually resulting from the lateral mobilization of the previous topographic hollow axis, can locally control the preferential expansion of the saturated zone towards areas other than the present hollow axis. During rainy periods, pressure head at the base of the hollow axis increases towards a maximum value which is not increased by subsequent precipitation inputs. New water input is dissipated by direct precipitation onto the saturated zone and exfiltration by seepage at the gully head walls, precluding the development of the excess pore pressures required to trigger failure by landsliding.

  • Subsurface hydrology of layered Colluvium mantles in unchannelled valleys—south-Eastern Brazil
    Earth Surface Processes and Landforms, 1994
    Co-Authors: Nelson Ferreira Fernandes, Ana Luiza Coelho Netto, Willy Alvarenga Lacerda
    Abstract:

    The effects of subsurface hydrology on the evolution of erosive processes inside layered Colluvium mantles in unchannelled valleys are investigated. Tensiometer nests are installed in different morphological conditions with their specific depths controlled by the subsurface structure of the Colluvium mantle. Daily readings (during one year) and physical and mechanical analyses of the different Colluvium layers are carried out. In spite of a highly discontinuous subsurface structure, present topography is the major factor controlling subsurface flow in this landscape. Paleotopographic features, usually resulting from the lateral mobilization of the previous topographic hollow axis, can locally control the preferential expansion of the saturated zone towards areas other than the present hollow axis. During rainy periods, pressure head at the base of the hollow axis increases towards a maximum value which is not increased by subsequent precipitation inputs. New water input is dissipated by direct precipitation onto the saturated zone and exfiltration by seepage at the gully head walls, precluding the development of the excess pore pressures required to trigger failure by landsliding.

Alan R Nelson - One of the best experts on this subject based on the ideXlab platform.

  • thermoluminescence dating of fault scarp derived Colluvium deciphering the timing of paleoearthquakes on the weber segment of the wasatch fault zone north central utah
    Journal of Geophysical Research, 1991
    Co-Authors: Steven L Forman, Alan R Nelson, James P Mccalpin
    Abstract:

    The timing of middle to late Holocene faulting on the Weber segment of the Wasatch fault zone, Utah, is constrained by thermoluminescence (TL) and radiocarbon age estimates on fine-grained, fault-related colluvial sediments. The stratigraphy in two trenches excavated across fault scarps is characterized by a stack of three colluvial wedges, deposited in response to three separate faulting events, the oldest of which buried a soil developed on a middle Holocene debris flow. Thermoluminescence age estimates by the partial and total bleach methods and the regeneration method on fine-grained Colluvium from the trenches agree within 1 sigma and are concordant with the radiocarbon chronology. A synthesis of the TL and 14C age estimates indicate that these three faulting events occurred sometime between 4500 and 3500, between 3200 and 2500, and between 1400 and 1000 years ago. Detailed investigation of a sequence of fine-grained, scarp-derived distal Colluvium shows that much of the sediment was deposited during <600-year intervals immediately after faulting. The sedimentation rate of Colluvium is inferred to increase shortly after faulting, and TL dating of these sediments provides additional information to constrain the timing of faulting events.

  • Thermoluminescence dating of fault-scarp-derived Colluvium: Deciphering the timing of paleoearthquakes on the Weber Segment of the Wasatch Fault Zone, north central Utah
    Journal of Geophysical Research, 1991
    Co-Authors: Steven L Forman, Alan R Nelson, James P Mccalpin
    Abstract:

    The timing of middle to late Holocene faulting on the Weber segment of the Wasatch fault zone, Utah, is constrained by thermoluminescence (TL) and radiocarbon age estimates on fine-grained, fault-related colluvial sediments. The stratigraphy in two trenches excavated across fault scarps is characterized by a stack of three colluvial wedges, deposited in response to three separate faulting events, the oldest of which buried a soil developed on a middle Holocene debris flow. Thermoluminescence age estimates by the partial and total bleach methods and the regeneration method on fine-grained Colluvium from the trenches agree within 1 sigma and are concordant with the radiocarbon chronology. A synthesis of the TL and 14C age estimates indicate that these three faulting events occurred sometime between 4500 and 3500, between 3200 and 2500, and between 1400 and 1000 years ago. Detailed investigation of a sequence of fine-grained, scarp-derived distal Colluvium shows that much of the sediment was deposited during