The Experts below are selected from a list of 90 Experts worldwide ranked by ideXlab platform
Ellery Frahm - One of the best experts on this subject based on the ideXlab platform.
-
lithic raw material units based on magnetic properties a blind test with armenian obsidian and application to the middle palaeolithic site of lusakert cave 1
Journal of Archaeological Science, 2016Co-Authors: Ellery Frahm, Joshua M Feinberg, Gilliane F Monnier, Gilbert B Tostevin, Boris Gasparyan, Daniel S AdlerAbstract:Classification of lithic artifacts’ raw materials based on macroscopic attributes (e.g., color, luster, texture) has been used to pull apart knapping episodes in palimpsest assemblages by attempting to identify artifacts produced through the reduction of an individual nodule. These classes are termed “raw material units” (RMUs) in the Old World and “minimum analytical nodules” in the New World. RMUs are most readily defined for lithic artifacts in areas with distinctive cherts and other siliceous raw materials, allowing pieces from different nodules to be recognized visually. Opportunities to apply RMUs, however, are strongly limited at sites where lithic material visual diversity is low. The magnetic properties of obsidian, which result from the presence of microscopic Iron Oxide Mineral grains, vary spatially throughout a flow. Consequently, obsidian from different portions of a source (i.e., different outcrops or quarries) can vary in magnetic properties. This raises the possibility that magnetic-based RMUs (mRMUs) for obsidian artifacts could be effective to distinguish individual scatters from multiple production episodes and offer insights into spatial patterning within a site or specific occupation periods. First, we assess the potential of mRMUs using obsidian pebbles from Gutansar volcano in Armenia. Second, we evaluate the validity of this approach based on a double-blind test involving an experimental assemblage of Gutansar obsidian flakes. Cluster analysis can successfully discern flakes from obsidian specimens containing high concentrations of Iron Oxides. Obsidian with more magnetic material has more opportunities for that material to vary in unique ways (e.g., grain size, morphology, physical arrangement). Finally, we apply the mRMU approach to obsidian artifacts from the Middle Palaeolithic site of Lusakert Cave 1 in Armenia and compare the results to traditional RMU studies at contemporaneous sites in Europe. In particular, we seek – but do not find – differences between retouch flakes (which reflect rejuvenation of tools) and the other small debris (which reflect other reduction activities). This result likely reflects the local landscape, specifically the abundance of obsidian and, thus, little pressure to curate and retouch tools. As this approach is applied to additional sites, such findings will play a central role in regional assessments about the nature and timing of the Middle to Upper Palaeolithic “transition” and the relationship, or lack thereof, between technological behaviors and presumed population dynamics.
Gary R Byerly - One of the best experts on this subject based on the ideXlab platform.
-
Ironstone pods in the archean barberton greenstone belt south africa earth s oldest seafloor hydrothermal vents reinterpreted as quaternary subaerial springs
Geology, 2003Co-Authors: Donald R Lowe, Gary R ByerlyAbstract:Bodies of Iron Oxide to 200 m across in the 3.5–3.2 Ga Barberton greenstone belt, South Africa, have been interpreted as deposits of Archean seafloor hydrothermal vents and have provided what are arguably key observations about surface envIronments on early Earth. These bodies, termed “Ironstone pods,” have yielded what are putatively the oldest-known complex organic compounds and have been used to estimate Archean surface temperature, ocean depth and volume, and seawater composition and to deduce relationships between hydrothermal activity and seafloor sedimentation. However, the pods are composed largely of goethite (a thermally unstable hydrated Iron Oxide Mineral), show abundant still-open primary porosity, are undeformed in a terrane of highly deformed rocks, and show bedding and cavity-filling dripstone indicating formation with their present orientation. They are here interpreted to have formed as spring and shallow subsurface deposits of young (Quaternary) groundwater and/or low-temperature hydrothermal systems. Iron was derived by the dissolution of siderite in surrounding Archean sedimentary rocks. Along pod margins, goethite locally replaces Archean chert and silicified ultramafic rock. However, coarse vein and cavity-fill quartz was less susceptible to replacement and remains as disrupted masses and rare remnant veins in the Ironstone. This quartz is of Archean age but contains no more information about the Archean surface envIronment than other late hydrothermal veins throughout the Barberton greenstone belt rocks. The presence of a well-preserved modern Iron Oxide spring terrace confirms that these are deposits of young subaerial springs and contain no record of Archean life or envIronments. They do, however, provide a unique view of a remarkable young Iron-depositing hydrologic system.
Daniel S Adler - One of the best experts on this subject based on the ideXlab platform.
-
lithic raw material units based on magnetic properties a blind test with armenian obsidian and application to the middle palaeolithic site of lusakert cave 1
Journal of Archaeological Science, 2016Co-Authors: Ellery Frahm, Joshua M Feinberg, Gilliane F Monnier, Gilbert B Tostevin, Boris Gasparyan, Daniel S AdlerAbstract:Classification of lithic artifacts’ raw materials based on macroscopic attributes (e.g., color, luster, texture) has been used to pull apart knapping episodes in palimpsest assemblages by attempting to identify artifacts produced through the reduction of an individual nodule. These classes are termed “raw material units” (RMUs) in the Old World and “minimum analytical nodules” in the New World. RMUs are most readily defined for lithic artifacts in areas with distinctive cherts and other siliceous raw materials, allowing pieces from different nodules to be recognized visually. Opportunities to apply RMUs, however, are strongly limited at sites where lithic material visual diversity is low. The magnetic properties of obsidian, which result from the presence of microscopic Iron Oxide Mineral grains, vary spatially throughout a flow. Consequently, obsidian from different portions of a source (i.e., different outcrops or quarries) can vary in magnetic properties. This raises the possibility that magnetic-based RMUs (mRMUs) for obsidian artifacts could be effective to distinguish individual scatters from multiple production episodes and offer insights into spatial patterning within a site or specific occupation periods. First, we assess the potential of mRMUs using obsidian pebbles from Gutansar volcano in Armenia. Second, we evaluate the validity of this approach based on a double-blind test involving an experimental assemblage of Gutansar obsidian flakes. Cluster analysis can successfully discern flakes from obsidian specimens containing high concentrations of Iron Oxides. Obsidian with more magnetic material has more opportunities for that material to vary in unique ways (e.g., grain size, morphology, physical arrangement). Finally, we apply the mRMU approach to obsidian artifacts from the Middle Palaeolithic site of Lusakert Cave 1 in Armenia and compare the results to traditional RMU studies at contemporaneous sites in Europe. In particular, we seek – but do not find – differences between retouch flakes (which reflect rejuvenation of tools) and the other small debris (which reflect other reduction activities). This result likely reflects the local landscape, specifically the abundance of obsidian and, thus, little pressure to curate and retouch tools. As this approach is applied to additional sites, such findings will play a central role in regional assessments about the nature and timing of the Middle to Upper Palaeolithic “transition” and the relationship, or lack thereof, between technological behaviors and presumed population dynamics.
Donald E Canfield - One of the best experts on this subject based on the ideXlab platform.
-
spatial variability in oceanic redox structure 1 8 billion years ago
Nature Geoscience, 2010Co-Authors: Simon W Poulton, Philip Fralick, Donald E CanfieldAbstract:The deposition of Iron formations ceased about 1.84 billion years ago. Reconstructions of ocean chemistry suggest that the advent of euxinic conditions along ocean margins preferentially removed dissolved Iron from the water column in the form of the Mineral pyrite, inhibiting widespread Iron-Oxide Mineral deposition.
Donald R Lowe - One of the best experts on this subject based on the ideXlab platform.
-
Ironstone pods in the archean barberton greenstone belt south africa earth s oldest seafloor hydrothermal vents reinterpreted as quaternary subaerial springs
Geology, 2003Co-Authors: Donald R Lowe, Gary R ByerlyAbstract:Bodies of Iron Oxide to 200 m across in the 3.5–3.2 Ga Barberton greenstone belt, South Africa, have been interpreted as deposits of Archean seafloor hydrothermal vents and have provided what are arguably key observations about surface envIronments on early Earth. These bodies, termed “Ironstone pods,” have yielded what are putatively the oldest-known complex organic compounds and have been used to estimate Archean surface temperature, ocean depth and volume, and seawater composition and to deduce relationships between hydrothermal activity and seafloor sedimentation. However, the pods are composed largely of goethite (a thermally unstable hydrated Iron Oxide Mineral), show abundant still-open primary porosity, are undeformed in a terrane of highly deformed rocks, and show bedding and cavity-filling dripstone indicating formation with their present orientation. They are here interpreted to have formed as spring and shallow subsurface deposits of young (Quaternary) groundwater and/or low-temperature hydrothermal systems. Iron was derived by the dissolution of siderite in surrounding Archean sedimentary rocks. Along pod margins, goethite locally replaces Archean chert and silicified ultramafic rock. However, coarse vein and cavity-fill quartz was less susceptible to replacement and remains as disrupted masses and rare remnant veins in the Ironstone. This quartz is of Archean age but contains no more information about the Archean surface envIronment than other late hydrothermal veins throughout the Barberton greenstone belt rocks. The presence of a well-preserved modern Iron Oxide spring terrace confirms that these are deposits of young subaerial springs and contain no record of Archean life or envIronments. They do, however, provide a unique view of a remarkable young Iron-depositing hydrologic system.
