Beyond techno-science: Transgenic maize in the fight over Mexico’s future     

Kathleen McAfee 《Geoforum》2008,39(1):148-160

Disputes about genetically engineered crops are linked to wider debates about the globalization of agro-food systems and its consequences for food security, social equity, and rural life. Biotechnology expert discourse rarely addresses these wider issues. An exception is the assessment of transgenic maize by the NAFTA Commission on Environmental Cooperation (CEC), which recommended a moratorium on Mexican imports of US-grown maize. Controversy about “contamination” of indigenous maize varieties by US-grown transgenic corn has been intensified by rising Mexican discontent with the terms of regional economic integration. In this context, scientists and officials were pressured to consider not only risks to maize biodiversity but also the ecological, and cultural characteristics of maize in its Mexican settings and the implications of asymmetric power in North American agricultural trade. In contrast to most narrowly-framed biotechnology risk assessments, the review took account of interventions by rural social movements. While the new moratorium was not adopted by the state, continuing conflicts over GMOs in Mexico have blocked introduction of transgenic maize and have enlarged the political space for debate over Mexico’s development direction. These conflicts reflect the differing interests of various state actors and economic sectors with regard to trade liberalization. They also reveal contrasting food-system paradigms: further agricultural modernization, export competition, and food-import dependence versus an alternative vision of revitalized rural life, farmers’ rights, and national food sovereignty.  相似文献   

Geochemical characteristics of gold-related granitoids in southwestern New Brunswick, Canada     

Xue-Ming Yang  David R. Lentz  Guoxiang Chi  Kathleen G. Thorne 《Lithos》2008,104(1-4):355-377

Two groups of granitoids associated with gold mineralization in the Appalachian orogen of southwestern New Brunswick are recognized: a Late Silurian to Early Devonian (423–396 Ma) granodioritic to monzogranitic series (GMS), and a Late Devonian (370–360 Ma) granitic series (GS). The GMS granitoids are relatively low in silica, calc-alkaline, metaluminous to weakly peraluminous, and show characteristics of normal (oxidized) to reduced I-type granites depending on the properties of country rocks. They may have been derived from partial melting of lower crustal rocks triggered by underplated basaltic magmas; and country rocks bearing reduced organic carbon and/or graphite may have played an important role in the reduction of normal I-type intrusions to reduced I-type, which is essential in the formation of intrusion-related gold systems. In contrast, the GS granites, although calc-alkaline and metaluminous to peraluminous, are relatively rich in silica, incompatible elements, and high field strength elements. They are fractionated I-type granites, and are probably related to the coeval Mount Douglas granite in the Saint George batholith through fractional crystallization. Their parental magmas may have been derived from partial melting of quartzofeldspathic sources at relatively low temperatures. Both GMS and GS intrusions are orogenic, although some of them display the affinity of those emplaced into a within-plate environment. The origin of intrusion-related gold systems in this region appears to be controlled by several factors, including magma sources, magmatic processes, redox conditions (country-rock nature), and local structural regimes.  相似文献   

Quechua II contraction in the Ayacucho intermontane basin: Evidence for rapid and episodic Neogene deformation in the Andes of central Perú     

James M. Wise  Donald C. Noble  Kathleen A. Zanetti  Terry L. Spell 《Journal of South American Earth Sciences》2008,26(4):383-396

In the Ayacucho basin of central Perú the regional Quechua II contractional deformation is bracketed by ⁴⁰Ar/³⁹Ar isotopic age determinations to a maximum duration of about 300,000 years, and probably less than 150,000 years, centered on 8.7 Ma. The strongly deformed Huanta Formation beneath the Quechua II angular unconformity was deposited during a period of extension that began before 9.05 ± 0.05 Ma. Deposition of a thick succession of alluvial fan deposits interbedded with flows of basaltic andesite in the Tingrayoc Member continued up to about 8.76 ± 0.05 Ma with the later part of the sedimentary record reflected by lacustrine deposits of the Mayocc Member. The upper limit on contractional deformation is constrained by an age of 8.64 ± 0.05 Ma on a unit of tuff near the base of the Puchcas volcanics, which in places was deposited upon near-vertical beds of the Huanta Formation. The Ayacucho Formation was deposited, locally unconformably, upon the Puchcas volcanics beginning slightly before 7.65 ± 0.10 Ma.Extended periods of neutral to tensional stress interrupted by rapid well-developed pulses of contractional deformation demonstrate the episodic behavior of Andean orogeny in Perú. The very short duration for the Quechua II event implies that driving forces for episodic deformation may be related to coupling along the orogen boundaries and strain accumulation and release mechanisms in the continental crust instead of much longer-term variations in the configuration of converging plates.  相似文献   

Response of closed basin lakes to interannual climate variability     

Kathleen Huybers  Summer Rupper  Gerard H. Roe 《Climate Dynamics》2016,46(11-12):3709-3723

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Using sedimentology to address the marine or continental origin of the Permian Hutchinson Salt Member of Kansas     

Anna Sofia Andeskie  Kathleen C. Benison 《Sedimentology》2020,67(2):882-896

The Permian Hutchinson Salt Member of the Wellington Formation of the Sumner Group of Kansas (USA) has multiple scientific and industrial uses. Although this member is highly utilized, there has not been a sedimentological study on these rocks in over 50 years, and no study has investigated the full thickness of this member. Past publications have inferred a marine origin as the depositional environment. Here, this marine interpretation is challenged. The goals of this study are to fully document sedimentological and stratigraphic characteristics of the Permian Hutchinson Salt Member in the Atomic Energy Commission Test Hole 2 core from Rice County, Kansas. This study documents colour, mineralogy, sedimentary textures, sedimentary structures, diagenetic features and stratigraphic contacts in core slab and thin sections. The Hutchinson Salt Member is composed of five lithologies: bedded halite, siliciclastic mudstone, displacive halite, bedded gypsum/anhydrite and displacive gypsum/anhydrite. These lithologies formed in shallow surface brines and mudflats that underwent periods of flooding, evapoconcentration and desiccation. Of note are the paucity of carbonates, lack of marine-diagnostic fossils, absence of characteristic marine minerals and lithofacies, and the stratigraphic context of the Hutchinson with associated continental deposits. The Hutchinson Salt Member was most likely deposited in an arid continental setting. This new interpretation offers a refined view of Pangaea during the middle Permian time.  相似文献   

Evolution and stratigraphic architecture of marine slope gully complexes: Monterey Formation (Miocene), Gaviota Beach,California     

Kathleen D. Surpless  Richard B. Ward  Stephan A. Graham 《Marine and Petroleum Geology》2009

Three small headlands in the sea cliffs west of Gaviota Beach, California, are the remnant fill of three discrete submarine gullies incised into the late Miocene submarine slope environment. These promontories provide excellent, three-dimensional exposure of the gully fill in outcrop, permitting documentation of their complex internal stratigraphic architecture. Detailed study of these exposures elucidates the sedimentologic processes that occur in the filling of slope gullies, guides interpretation of the acoustic records of otherwise unsampled modern gully systems on continental slopes, and provides insight into the heterogeneity that may characterize slope gully petroleum reservoirs.  相似文献   

The changing Patagonian landscape: Erosion and westward sediment transfer paths in northern Patagonia during the Middle and Late Pleistocene     

Tania Villaseñor  Daniel Tentori  Kathleen M. Marsaglia  Luisa Pinto 《Basin Research》2020,32(5):1035-1053

Pleistocene glaciations have promoted important landscape transformations as a result of high rates of erosion and rapid sediment evacuation to adjacent marine basins. In the Patagonian Andes the role of the Patagonian Ice Sheet on landscape evolution, in particular the spatial patterns of glacial erosion and its influence on sediment fluxes, is poorly documented. Here, we investigate the Middle and Late Pleistocene sedimentary record of the continental slope from Ocean Drilling Program (ODP) Site 861, offshore Patagonia (46°S), to evaluate the link between glaciations, mountain range erosion and continental margin strata formation. Petrographic analysis of the sand-size fraction (0.063–2 mm) and ɛNd and ⁸⁷Sr/⁸⁶Sr measurements in the silt-size fraction (10–63 µm) indicate that glacial erosion over the last 350,000 years has focused within the Patagonian Batholith, with a minor influence of a proximal source to the drilling site, the Chonos Metamorphic Complex. This shows that erosion has focused in the core of the northern Patagonian Andes, coinciding roughly with the location of the Liquiñe-Ofqui Fault Zone and the zone of concentrated precipitation during glaciations, suggesting a combined climatic and structural control on glacial erosion. Temporal variation in the provenance signal is contemporaneous with a marked change in the stratigraphy of ODP Site 861 that occurred after the glaciation of MIS 8 (~240 kyr ago). Before MIS 8, a restricted provenance signal and coarse lithofacies accumulated on the continental slope indicates spatially restricted erosion and efficient transfer of sediment towards the ocean. In contrast, very high provenance variability and finer continental slope lithofacies accumulation after MIS 8 suggest a disorganized expansion of the areas under erosion and a more distal influence of ice sediment discharge to this site. We argue that this change may have been related to a re-organization of the drainage patterns of the Patagonian Ice Sheet and flow of outlet glaciers to the continental margin during the last two glaciations.  相似文献   

Sea-level history of the past two interglacial periods: new evidence from U-series dating of reef corals from south Florida     

Daniel R. Muhs  Kathleen R. Simmons  R. Randall Schumann  Robert B. Halley 《Quaternary Science Reviews》2011,30(5-6):570-590

As a future warm-climate analog, much attention has been directed to studies of the Last Interglacial period or marine isotope substage (MIS) 5.5, which occurred ～120,000 years ago. Nevertheless, there are still uncertainties with respect to its duration, warmth and magnitude of sea-level rise. Here we present new data from tectonically stable peninsular Florida and the Florida Keys that provide estimates of the timing and magnitude of sea-level rise during the Last Interglacial period. The Last Interglacial high sea stand in south Florida is recorded by the Key Largo Limestone, a fossil reef complex, and the Miami Limestone, an oolitic marine sediment. Thirty-five new, high-precision, uranium-series ages of fossil corals from the Key Largo Limestone indicate that sea level was significantly above present for at least 9000 years during the Last Interglacial period, and possibly longer. Ooids from the Miami Limestone show open-system histories with respect to U-series dating, but show a clear linear trend toward an age of ～120 ka, correlating this unit with the Last Interglacial corals of the Key Largo Limestone. Older fossil reefs at three localities in the Florida Keys have ages of ～200 ka and probably correlate to MIS 7. These reefs imply sea level near or slightly above present during the penultimate interglacial period. Elevation measurements of both the Key Largo Limestone and the Miami Limestone indicate that local (relative) sea level was at least 6.6 m, and possibly as much as 8.3 m higher than present during the Last Interglacial period.  相似文献   

Influence of groundwater and topography on stream drying in semi-arid headwater streams     

Sara R. Warix  Sarah E. Godsey  Kathleen A. Lohse  Rebecca L. Hale 《水文研究》2021,35(5):e14185

Non-perennial streams comprise over half of the global stream network and impact downstream water quality. Although aridity is a primary driver of stream drying globally, surface flow permanence varies spatially and temporally within many headwater streams, suggesting that these complex drying patterns may be driven by topographic and subsurface factors. Indeed, these factors affect shallow groundwater flows in perennial systems, but there has been only limited characterisation of shallow groundwater residence times and groundwater contributions to intermittent streams. Here, we asked how groundwater residence times, shallow groundwater contributions to streamflow, and topography interact to control stream drying in headwater streams. We evaluated this overarching question in eight semi-arid headwater catchments based on surface flow observations during the low-flow period, coupled with tracer-based groundwater residence times. For one headwater catchment, we analysed stream drying during the seasonal flow recession and rewetting period using a sensor network that was interspersed between groundwater monitoring locations, and linked drying patterns to groundwater inputs and topography. We found a poor relationship between groundwater residence times and flowing network extent (R² < 0.24). Although groundwater residence times indicated that old groundwater was present in all headwater streams, surface drying also occurred in each of them, suggesting old, deep flowpaths are insufficient to sustain surface flows. Indeed, the timing of stream drying at any given point typically coincided with a decrease in the contribution from near-surface sources and an increased relative contribution of groundwater to streamflow at that location, whereas the spatial pattern of drying within the stream network typically correlated with locations where groundwater inputs were most seasonally variable. Topographic metrics only explained ~30% of the variability in seasonal flow permanence, and surprisingly, we found no correlation with seasonal drying and down-valley subsurface storage area. Because we found complex spatial patterns, future studies should pair dense spatial observations of subsurface properties, such as hydraulic conductivity and transmissivity, to observations of seasonal flow permanence.  相似文献   

YREE sorption on hydrous ferric oxide in 0.5 M NaCl solutions: A model extension     

Johan Schijf  Kathleen S. Marshall 《Marine Chemistry》2011,123(1-4):32-43

Distribution coefficients, _iK_Fe, were measured for sorption of yttrium and the rare earth elements (YREEs) on hydrous ferric oxide (HFO) in 0.5 M NaCl solutions over the pH range 3.9–8.4 (T = 25 °C). An existing, non-electrostatic model [Quinn, K.A., Byrne, R.H., Schijf, J., 2006. Sorption of yttrium and rare earth elements by amorphous ferric hydroxide: influence of pH and ionic strength. Mar. Chem. 99, 128–150] was modified to account for sorption of YREE–chloride complexes, as well as YREE–hydroxide complexes at elevated pH. The extended model, which allows calculation of _iK_Fe as a function of [H⁺], contains two parameters, _SK₁ and _SK₂, to describe the equilibrium between positive, neutral, and negative forms of the hydroxyl functional groups on the HFO surface. In addition, it contains several composite, conditional stability constants, A_n, that represent YREE bonding to the neutral groups with release of n protons and/or to the negatively charged groups with release of n ? 1 protons.In 0.5 M NaCl solutions, YREE sorption on HFO is weaker and less pH dependent, yielding only 0.7–0.9 protons per YREE cation on average, vs. about 1.5 at low ionic strength. This is due to enhanced deprotonation of the HFO surface (_SK₁ ~ 0, p_SK₂ = 6.16), leading to an increase in the proportion of negatively charged groups, which release fewer protons per YREE cation sorbed. On a logarithmic scale, _iK_Fe is a nearly linear function of pH, except at pH > 8 where cumulative sorption of YREE–hydroxide complexes causes it to rise more rapidly, especially for the heavy REEs. Both our own data and prior results from the literature are well described by the extended model, using only three adjustable parameters, A₁–A₃. The constant A₃, representing YREE bonding to the negatively charged groups with release of two protons, shows an excellent linear free-energy relation when plotted against the first YREE hydrolysis constant, β₁*. There is no evidence for YREE bonding to the positively charged groups (i.e., A₀ = 0).  相似文献