摘要:

AbstractAnasazi farmers in northern New Mexico occasionally applied a pebble mulch to their gardens during the 14th and 15th centuries A. D. to increase crop yield and to buffer against drought. Regional variations in surface geology and soils are compared to the distribution of pebble‐mulch gardens near Pueblo San Marcos in the Galisteo Basin, south of Santa Fe. The slope angle and aspect of 96 individual garden plots are also examined to determine the role of microenvironment as a siting consideration within the broader geological‐pedological context. It is found that Anasazi pebble‐mulch gardens were consistently sited on south‐facing, relatively flat slopes of erosional benches, within naturally occurring surface/near surface deposits of gravel. This suggests that the Anasazi intentionally exploited regionally scaled variations in geology and soils in their pursuit of agricultural diversification. © 1993 John Wiley&S

ISSN:0883-6353    

DOI:10.1002/gea.3340080502

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractUsers of the obsidian hydration dating method have routinely assumed that artifacts which originate from the same geological flow will be of the same chemical composition and thus hydrate at the same rate under equivalent conditions of temperature and relative humidity. Recent laboratory experimentation into the hydration process has shown that the intrinsic water content of the glass is the dominant factor in establishing the rate of hydration. Water content determinations on a large suite of samples from numerous prehistoric quarries within the Coso volcanic field, California, indicated that water content values, and thus hydration rate, varied significantly on a within flow basis. It is recommended that water determinations be made on individual artifacts prior to obsidian hydration dating. © 1993 John Wiley&Sons, Inc

ISSN:0883-6353    

DOI:10.1002/gea.3340080503

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractIn many instances, geologically distinct obsidian flows located within even a relatively small geographic area can be uniquely identified by their chemical composition. This happens to be true for several obsidian sources from central Oregon. Internally each obsidian locality is chemically homogeneous, but the obsidian rocks from different collection sites exhibit chemical differences. Based on the geochemical variations and on K/ Ar dating of the end members of the chemical differentiation trend, these differences are related to the fractionation of a single Late Miocene magma chamber, dated at 6.5 Ma. By understanding the underlying causes of the chemical differences, constraints are disclosed that will govern the possible chemical variations of other, as yet unidentified but related obsidian flows. These can be useful for identifying the possible natural sources of obsidian artifacts which do not match known obsidian sources, and for suggesting possible geographic areas where these as yet undiscovered obsidian flows may be found. © 1993 John Wiley&Sons, Inc

ISSN:0883-6353    

DOI:10.1002/gea.3340080504

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractSamples of slag from three sites of a traditional lead industry located between Khuzdar and Nal were studied to determine their petrology, chemical composition, smelting conditions, source material, and age. Polished thin sections viewed in reflected light revealed a white glassy matrix with occasional rare mineral grains. Using an automated microprobe, typical glass composition was found to be 40% SiO2, 17% FeO, 11% CaO, 12% PbO, and 10% BaO. Repeated applications of Principal Component Analysis to the data revealed that the compositions of our slags fell within a tetrahedron. The ratios of most components to other components were found to be nearly constant, suggesting that the same indigenous source materials were mixed in almost the same proportion at all the sites. A comparative study of the composition of our slag in relation with various binary and ternary phase diagrams after necessary normalization of the data showed that addition of CaO and BaO by the traditional smelters and the formation of PbO during the process of smelting helped to lower the temperature required for smelting below 1200°C. Lead isotopic compositions suggested that our lead is isotopically distinct from sites in Greece. © 1993 John Wiley&Sons, In

ISSN:0883-6353    

DOI:10.1002/gea.3340080505

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractResearch on comestible earths utilized in the Andes indicates that they have a history of use of at least 2500 years. A hypothesis proposed for the origin of geophagy suggests a considerably greater time depth. Comestible earths discussed involve those with physiological, cultural, or medicinal components. This analysis includes 27 indigenously recognized earths. © 1993 John Wiley&Sons, Inc

ISSN:0883-6353    

DOI:10.1002/gea.3340080506

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

ISSN:0883-6353    

DOI:10.1002/gea.3340080507

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

ISSN:0883-6353    

DOI:10.1002/gea.3340080508

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

ISSN:0883-6353    

DOI:10.1002/gea.3340080509

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

ISSN:0883-6353    

DOI:10.1002/gea.3340080510

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

ISSN:0883-6353    

DOI:10.1002/gea.3340080511

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY