Fault identification using multidisciplinary techniques at the Mars/Uranus Station antenna sites

A fault investigation was performed at the Mars and Uranus antenna sites at the Goldstone Deep Space Communications Complex in the Mojave desert. The Mars/Uranus Station consists of two large-diameter reflector antennas used for communication and control of deep-space probes and other missions. The investigation included interpretation of Landsat thematic mapper scenes, side-looking airborne radar transparencies, and both color-infrared and black-and-white aerial photography. Four photolineaments suggestive of previously undocumented faults were identified. Three generally discrete morphostratigraphic alluvial-fan deposits were also recognized and dated using geomorphic and soil stratigraphic techniques. Fourteen trenches were excavated across the four lineaments; the trenches show that three of the photolineaments coincide with faults. The last displacement of two of the faults occurred between about 12,000 and 35,000 years ago. The third fault was judged to be older than 12,000 years before present (ybp), although uncertainty remains. None of the surface traces of the three faults crosses under existing antennas or structures; however, their potential activity necessitates appropriate seismic retrofit designs and loss-prevention measures to mitigate potential earthquake damage to facilities and structures

Recent soil-geomorphic methods for delimiting archaeological sites

Traditionally archaeological sites have been recognized and delimited by reconnaissance of the surface distribution of artifacts. Often, however, this approach underestimates the true horizontal and vertical extent of a site. More complete data can be obtained by an on-going systematic sampling program combined with soil-geomorphic analyses. After discovery, a major prehistoric site near San Francisco, California was delimited both by traditional and by soil-geomorphic methods. The site generally conforms to a superimposed alluvial fan deposit (with mudflows and debris flows) internally separated by several buried soils (organic horizons). Detailed soil descriptions (pedogenic profiles) and laboratory analyses of P, Na, K, cation exchange, and organic matter content all reveal that the site is deeper and extends far beyond that originally delimited by traditional methods. Soil-geomorphic analyses are best employed prior to completion of a sampling design and excavation of a site.Selon la méthode traditionnelle, des sites archéologiques ont été découverts et délimités par reconnaissance des objets archéologiques trouvés à la surface du site. Cependant, fréquemment cette méthode a sous-estimé l'étendue horizontale et verticale du site. Il est possible d'obtenir des dates plus complètes au moyen d'un programme systématique de sondages, combiné avec des analyses pédologiques. Après la découverte d'un des plus importants sites archéologiques dans les environs de San Francisco, en Californie, le site a été délimité au moyen de deux méthodes, par la méthode traditionnelle, aussi bien que par la méthode pédologique. En général, le site est couvert de couches alluviales de sable (avec des apports de boue et des débris), séparées entre elles par plusieurs sols d'occupation (avec horizons organiques). Les descriptions détaillées des sols (profils pédogéniques) , les analyses de laboratoire pour P, Na, K, le potentiel d'échange de cation et la teneur en matière organique ont révélé que le site est bien plus profond et a une étendue considérablement plus grande qu'il n'avait été estimé, antérieurement par la méthode traditionnelle. Pour la meilleur utilisation des analyses pédologiques, il est souhaitable de les faire avant la fin des sondages et des fouilles d'un site.Gary-Stickel E., Shlemon R. J. Recent soil-geomorphic methods for delimiting archaeological sites. In: Revue d'Archéométrie, n°5, 1981. pp. 29-39

Deep soil inventories reveal that impacts of cover crops and compost on soil carbon sequestration differ in surface and subsurface soils

Increasing soil organic carbon (SOC) via organic inputs is a key strategy for increasing long-term soil C storage and improving the climate change mitigation and adaptation potential of agricultural systems. A long-term trial in California's Mediterranean climate revealed impacts of management on SOC in maize-tomato and wheat-fallow cropping systems. SOC was measured at the initiation of the experiment and at year 19, at five depth increments down to 2 m, taking into account changes in bulk density. Across the entire 2 m profile, SOC in the wheat-fallow systems did not change with the addition of N fertilizer, winter cover crops (WCC), or irrigation alone and decreased by 5.6% with no inputs. There was some evidence of soil C gains at depth with both N fertilizer and irrigation, though high variation precluded detection of significant changes. In maize-tomato rotations, SOC increased by 12.6% (21.8 Mg C/ha) with both WCC and composted poultry manure inputs, across the 2 m profile. The addition of WCC to a conventionally managed system increased SOC stocks by 3.5% (1.44 Mg C/ha) in the 0-30 cm layer, but decreased by 10.8% (14.86 Mg C/ha) in the 30-200 cm layer, resulting in overall losses of 13.4 Mg C/ha. If we only measured soil C in the top 30 cm, we would have assumed an increase in total soil C increased with WCC alone, whereas in reality significant losses in SOC occurred when considering the 2 m soil profile. Ignoring the subsoil carbon dynamics in deeper layers of soil fails to recognize potential opportunities for soil C sequestration, and may lead to false conclusions about the impact of management practices on C sequestration