John C Sheppard

• A Reevaluation of the Marmes Rockshelter Radiocarbon Chronology

  John C Sheppard, Peter E Wigand et al.•ARTICLE•American Antiquity•1987•Citada por: 11•Referências: 1

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  Twenty years ago excavation began on Marmes Rockshelter at the mouth of the Palouse River in southeastern Washington. Radiocarbon determinations from cave and adjacent floodplain sediments indicated an established pattern of human use by 10,800 B.P. However, a scarcity of dates between 6000 and 1300 B.P. suggested that either these strata were undated or the cave was unused. Examination of all Marmes radiocarbon ages showed agreement between shel…

• Contrasting Climatic Histories for the Snake River Plain, Idaho, Resulting from Multiple Thermal Maxima

  Open Access•Owen Davis, Owen K Davis et al.•ARTICLE•Quaternary Research•1986

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  Ten sites near the Snake River Plain have consistent differences in their climatic histories. Sites at low elevation reflect the “early Holocene xerothermic” of the Pacific Northwest, whereas most climatic chronologies at high elevation indicate maximum warmth or aridity somewhat later, ca. 6000 yr ago. This elevational contrast in climatic histories is duplicated at three sites from the central Snake River Plain. For sites in such close proximit…

• The Age of Glacier Peak Tephra in West-Central Montana

  Open Access•Peter J Mehringer, John C Sheppard et al.•ARTICLE•Quaternary Research•1984

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  At Sheep Mountain Bog, near Missoula, Montana, a late-glacial tephra, that probably fell in late summer, is preserved as an 8-mm-thick graded bed overlain by another 8 mm of redeposited ash mixed with lake deposits. Sediment surrounding the ash was 14 C dated to about 11,200 yr B.P. Electron-microprobe analyses of the volcanic glass and hornblende phenocrysts from this ash layer indicate that they are similar in major-element chemistry to those o…

• Radiocarbon Dating Archaeologic and Environmental Samples Containing 10 to 120 Milligrams of Carbon

  Open Access•John C Sheppard, J Fred Hopper et al.•ARTICLE•Radiocarbon•1983•Referências: 9

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  A conventional 14 C system with either a 15cm 3 or a 100cm 3 methane gas proportional counting tube, each constructed from high purity copper, has been used at the Washington State University 14 C laboratory for three years (Sheppard, Hopper, Westberg, 1981). The electronic components of this system included highly stable (John Fluke) power supplies, modified pre-amplifiers (Canberra), and NIM amplifiers, single channel analyzers, scalers, timers…

• A Reevaluation of the Marmes Rockshelter Radiocarbon Chronology

  John C Sheppard, Peter E Wigand et al.•ARTICLE•American Antiquity•1987•Citada por: 11•Referências: 1

  Incluir item

  Twenty years ago excavation began on Marmes Rockshelter at the mouth of the Palouse River in southeastern Washington. Radiocarbon determinations from cave and adjacent floodplain sediments indicated an established pattern of human use by 10,800 B.P. However, a scarcity of dates between 6000 and 1300 B.P. suggested that either these strata were undated or the cave was unused. Examination of all Marmes radiocarbon ages showed agreement between shel…

• Radiocarbon Dating Archaeologic and Environmental Samples Containing 10 to 120 Milligrams of Carbon

  Open Access•John C Sheppard, J Fred Hopper et al.•ARTICLE•Radiocarbon•1983•Referências: 9

  Incluir item

  A conventional 14 C system with either a 15cm 3 or a 100cm 3 methane gas proportional counting tube, each constructed from high purity copper, has been used at the Washington State University 14 C laboratory for three years (Sheppard, Hopper, Westberg, 1981). The electronic components of this system included highly stable (John Fluke) power supplies, modified pre-amplifiers (Canberra), and NIM amplifiers, single channel analyzers, scalers, timers…

• The Age of Glacier Peak Tephra in West-Central Montana

  Open Access•Peter J Mehringer, John C Sheppard et al.•ARTICLE•Quaternary Research•1984

  Incluir item

  At Sheep Mountain Bog, near Missoula, Montana, a late-glacial tephra, that probably fell in late summer, is preserved as an 8-mm-thick graded bed overlain by another 8 mm of redeposited ash mixed with lake deposits. Sediment surrounding the ash was 14 C dated to about 11,200 yr B.P. Electron-microprobe analyses of the volcanic glass and hornblende phenocrysts from this ash layer indicate that they are similar in major-element chemistry to those o…

• Contrasting Climatic Histories for the Snake River Plain, Idaho, Resulting from Multiple Thermal Maxima

  Open Access•Owen Davis, Owen K Davis et al.•ARTICLE•Quaternary Research•1986

  Incluir item

  Ten sites near the Snake River Plain have consistent differences in their climatic histories. Sites at low elevation reflect the “early Holocene xerothermic” of the Pacific Northwest, whereas most climatic chronologies at high elevation indicate maximum warmth or aridity somewhat later, ca. 6000 yr ago. This elevational contrast in climatic histories is duplicated at three sites from the central Snake River Plain. For sites in such close proximit…

• A Reevaluation of the Marmes Rockshelter Radiocarbon Chronology

  John C Sheppard, Peter E Wigand et al.•ARTICLE•American Antiquity•1987•Citada por: 11•Referências: 1

  Incluir item

  Twenty years ago excavation began on Marmes Rockshelter at the mouth of the Palouse River in southeastern Washington. Radiocarbon determinations from cave and adjacent floodplain sediments indicated an established pattern of human use by 10,800 B.P. However, a scarcity of dates between 6000 and 1300 B.P. suggested that either these strata were undated or the cave was unused. Examination of all Marmes radiocarbon ages showed agreement between shel…

Geology (3 obras) · Paleontology (3 obras) · Archaeology and ancient environmental studies (2 obras) · Geography (2 obras) · Geology (2 obras) · Geology and Paleoclimatology Research (2 obras) · Radiocarbon dating (2 obras) · Amplifier (1 obras) · Archaeology (1 obras) · Archaeology and Natural History (1 obras)