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61.
Philipp R. Heck Christopher Herd Jeffrey N. Grossman Dmitry Badjukov Audrey Bouvier Emma Bullock Hasnaa Chennaoui‐Aoudjehane Vinciane Debaille Tasha L. Dunn Denton S. Ebel Ludovic Ferrire Laurence Garvie Jrme Gattacceca Matthieu Gounelle Richard Herd Trevor Ireland Emmanuel Jacquet Robert J. Macke Tim McCoy Francis M. McCubbin Takashi Mikouchi Knut Metzler Mathieu Roskosz Caroline Smith Meenakshi Wadhwa Linda Welzenbach‐Fries Toru Yada Akira Yamaguchi Ryan A. Zeigler Michael Zolensky 《Meteoritics & planetary science》2019,54(7):1397-1400
62.
Christopher Pierce 《Geoarchaeology》1992,7(3):185-208
The construction of burrows and movement of sediment by pocket gophers alter archaeological deposits by causing vertical size-sorting of artifacts, destruction of fragile artifacts, disruption of sedimentary structures, and organic enrichment of the subsurface. To evaluate the long-term effects of exposure to burrowing, a simulation was developed based on quantitative information on pocket gopher burrows and rates of sediment movement. Simulation results indicate the development of a distinct stone zone composed predominantly of particles greater than 6 cm after 4000–5000 years, and a logarithmic pattern to the rate of strata disruption. The patterns produced by the simulation compare well with patterns exhibited by actual archaeological deposits belonging to California's Milling Stone Horizon. These results suggest that current notions concerning the Milling Stone Horizon and other aspects of California prehistory may require revision, and that more emphasis must be placed on formation process research in such settings. 相似文献
63.
Christopher Lintz 《Geoarchaeology》1989,4(4):319-346
Thermal experiments under laboratory conditions examined caliche discoloration and thermal conductivity/shock. the results provide information about caliche behavior under thermal conditions, which in some environmental settings will assist archaeologists in identifying discolored caliche from cultural activities as opposed to that from natural range fires. Generally, temperature intensity affects discoloration more than heat exposure duration. Sample colors change markedly towards darker values with carbon reduction between 300° and 700° C caliche glows during heating as the carbon oxidizes; the samples tend towards paler colors, lighter weight, and increased fissures. the thermal conductivity experiment compared heat transference of caliche with other lithic resources of the Llano Estacado, while the thermal shock measured caliche resilience. Metaquartzites and cherts from the Llano Estacado are better heat conductors than caliche, but caliche is far more resilient to repeated thermal shock. 相似文献
64.
Christopher R. J. Charles Phil J. A. McCausland Donald W. Davis 《Meteoritics & planetary science》2020,55(5):1093-1102
Lovina, classified as an ungrouped ataxite, is controversial and its identity as a meteorite has been questioned. In this work, we use Pb isotopes on targeted troilite nodules in Lovina as a test of its antiquity and provenance. Although precise ages cannot be obtained, LA‐ICP‐MS offers a rapid, straightforward procedure to establish the source of lead, whether ancient (meteoritic) or modern (terrestrial). For nine pristine, unweathered nodules in Lovina, we find a lead isotopic composition of: 206Pb/208Pb = 0.492 ± 0.003 (2σ, MSWD 0.79; 95%) and 207Pb/206Pb = 0.852 ± 0.003 (2σ, MSWD 1.09; 95%) with no detectable uranium. All lead compositions of the troilite fall in the range expected for modern environmental and mantle lead and are distinctly different from the primordial Canyon Diablo Troilite (CDT) composition of ancient meteoritic troilite. Although the origin of Lovina remains unknown, we conclude that lead in the Lovina troilite is unsupported by U decay and originated from a terrestrial source. 相似文献
65.
Christopher Airriess 《Singapore journal of tropical geography》2020,41(1):6-22
The tropical fruit durian in Southeast and East Asia has witnessed a surge in popularity in the past two decades to assume the rank of a fetishized commodity. This research investigates the construction of the multidimensional concept of terroir as applied to the durian economy of Penang, Malaysia based on personal interviews with orchard owners and state government officials to strategically embed the local in the global through the promotion of agritourism. While environmental terroir is a contingent dimension, the construction of a place bound cultural terror is anchored in a strong cultivation tradition, cultivar diversity, and a historical sense of community. This research deepens the cultural terroir dimension in two ways. First, it injects the otherwise aspatial concept of refinement to the cultural terroir narratives of orchard owners allowing the on-farm tourist consumption experience to be more geographically rooted. Second, it conceptually links cultural terroir to the marketing terroir instrument of the Balik Pulau geographical indication; while functioning as a governance tool to prevent fraud and to construct a place bound product valorization and differentiation within an expanding and larger scale durian economy, it also indirectly assists in preserving agro-diversity and local identity. 相似文献
66.
We report on the results of an experimental study based on the petrology of the Tissint meteorite, an olivine-phyric shergottite that preserves evidence of an oxidation event during its petrogenesis. We find that oxidation occurring after olivine saturation modifies the Cr zoning profiles in experimental run products, and note that similar Cr-depleted olivine profiles occur in the natural sample. We consider processes that could operate to modify Cr zoning profiles in experimentally produced olivine, and find that diffusion operates too slowly; furthermore, peritectic resorption of olivine, which occurs during oxidation, does not adequately shorten the diffusion length to account for the depletion. Fine-grained (<10 μm) spinel grains are observed within olivine crystals exclusively in cooling rate experiments involving an oxidation step, suggesting that the mechanism causing modification of Cr zoning profiles in olivine is the oxidation-induced exsolution of Cr-spinel, consistent with observations of natural samples. A replicate experiment with V included in the composition shows that V is similarly affected. Known partitioning behavior suggests that Ni and Co should be similarly affected due to preferential partitioning into spinel. We consider implications of our observations for the interpretation of the petrogenetic histories of other olivine-phyric shergottites, and provide a new petrographic tool for recognizing oxidation events in olivine-phyric shergottites. 相似文献
67.
Christopher R. J. Charles Pierre-Yves F. Robin Donald W. Davis Phil J. A. McCausland 《Meteoritics & planetary science》2018,53(5):935-951
The approximately spherical shapes of chondrules has long been attributed to surface tension acting on ~1 mm melt droplets that formed and cooled in the microgravity field of the solar nebula. However, chondrule shapes commonly depart significantly from spherical. In this study, 109 chondrules in a sample of CR2 chondrite NWA 801 were imaged by X-ray computed tomography and best-fitted to ellipsoids. The analysis confirms that many chondrules are indeed not spherical, and also that the chondrules’ collective shape fabric records a definite 13% compaction in the host meteorite. Dehydration of phyllosilicates within chondrules may account for that strain. However, retro-deforming all chondrules shows that a large majority were already far from spherical prior to accretion. Possible models for these initial shapes include prior deformation of individual chondrules in earlier hosts, and, as suggested by previous authors, rotation of chondrules as they were solidifying, and/or “streaming” of molten chondrules by their differential velocities with their gaseous hosts after melting. More in situ 3-D work such as this study on a variety of unequilibrated chondrites, combined with detailed structural petrography, should help further constrain these models and refine our understanding of chondrite formation. 相似文献
68.
Rosalind C. King Guillaume Backé Christopher K. Morley Richard R. Hillis Mark R.P. Tingay 《Marine and Petroleum Geology》2010
Recent GPS measurements demonstrate that NW Borneo undergoes 4–6 mm of plate-scale shortening a year, which is not accommodated by plate-scale structures. The only geological structure in NW Borneo described to accommodate on-going shortening is the Baram Delta System located on the outer shelf to basin floor. Delta toe fold-thrust belts are commonly thought to be caused by margin-normal compressional stresses generated by margin-parallel upslope gravitational extension. 相似文献
69.
Sabine K.J. Cochrane Stanislav G. Denisenko Paul E. Renaud Christopher S. Emblow William G. Ambrose Jr. Ingrid H. Ellingsen Jofrid Skarhamar 《Journal of Sea Research》2009,61(4):222-233
Benthic faunal assemblages were analysed from 47 stations in the central and southern parts of the Barents Sea, together with sedimentary and water column parameters, daily ice records and modelled integrated primary productivity. Sampling spanned areas influenced by Atlantic Water (AW) to those lying under Arctic Water (ArW), and included stations with mixed water masses. Ice cover suppressed water column productivity in the northern areas. Three main faunal groups were identified, based on similarity of numerical faunal composition. The northern and southern faunal groups were separated by the northernmost penetration of AW in the bottom water and the third group, the Hopen group, was influenced by modified bank water. Faunal abundances were significantly higher within the southern faunal group relative to the northern group, but the numbers of taxa present were similar. The particularly rich fauna of the Hopen group reflected sediment heterogeneity and tight pelagic–benthic coupling. These results suggest that a retreat and thinning of the ice cover in the Barents Sea likely will result in the northern parts of the Barents Sea becoming more Atlantic in character, with a higher productivity at the sea floor. 相似文献
70.