Economic and climatic factors in ‘acreage abandonment’ over marginal cropland

Crop yield projections made at planting time or during the growing season often ignore the fact that an unknown percentage of planted acreage is not harvested. As a solution, we present a model for 'acreage abandonment, based upon both economic and weather variables. Weather is shown to be a much more important determinant of the decision not to harvest than is the expected price. The explained variance in abandonment of spring wheat acreage by future delivery price is approximately 16%, but rises to over 60% when weather variables are added. In a similarly designed model for winter wheat in the southern plains, the price contribution is less than 5%.The spring wheat model was tested on two extensive sets of withheld data: three-year successive deletions through the entire (1932–1975) data set, and a ten year block at the beginning of the modelling period that included substantial weather and price perturbations induced by the dust bowl, depression, and attendant market gyrations. Predictive capability was retained in both tests.Current weather appears to weigh more heavily in the abandonment decision than does future price.     

Comparison between natural and artificial maturation series of humic coals from the Mahakam delta,Indonesia

Type III (humic) organic matter from the Mahakam delta (Indonesia) was chosen to compare artificial and natural coal series. Powdered and concentrated immature organic matter was heated in sealed gold tubes for 24 hr at temperatures ranging from 250 to 550°C and under pressures ranging from 0.5 to 4 kb, with and without water. Both elemental and Rock-Eval analyses were used to characterize the products. A comparison between our results, published data and the natural model shows that, quantitatively, natural maturation is simulated better when pyrolysis is performed under confined conditions (no free volume, no diluting inert gas). Thus, pyrolysis in a medium swept by an inert gas, vacuum pyrolysis and some pyrolysis in sealed glass tubes must be considered to be poor simulation tools. The presence of water does not seem to have an essential effect. Allowing the hydrocarbons formed to reach a certain value of partial pressure seems to be important. Results are unchanged when external pressure varies from 0.5 to 4 kb.     

Importance of the oxidation/maturation pair in the evolution of humic coals

The natural thermal evolution of type III coals (Humic origin) is expressed during diagenesis by a loss of oxygen as CO₂ and H₂O. Other phenomena such as oxidation can cause extensive geochemical modifications and may complicate the effects of simple maturation.Humic coals from the Jurassic in southeastern Utah were studied by elemental analysis, Rock-Eval pyrolysis and infrared spectroscopy. In a van Krevelen diagram (atomic H/C vs atomic O/C), the samples fall within the envelope defined by 860 reference humic coals covering the entire range of diagenesis. Nevertheless, various criteria (geochemical, petrographic, geological and microscopic) cast doubt upon the interpretation that such a distribution of coal composition results from thermal maturation.The same criteria indicate the intervention of redox phenomena. Comparison of our results with those from artificial and natural oxidation shows that these coals were subjected to an oxidation process different from ordinary late alteration. This process was probably due to circulation of highly oxidizing saline water causing oxygen fixation and the transformation of carboxyls into carboxylate anions. The cations that were fixed are oxygenated and certainly contain calcium, but also uranium and perhaps several other cations (V, Mo, Fe...). Emphasis is placed on possible mechanisms that cause such phenomena.     

Policy and implementation in rural planning

Although often critical of the results achieved by rural planners, research by geographers and others has for some time been constrained by an inability to isolate the precise impacts of planning procedures on rural areas. The notions of a technically solvable ‘implementation problem’ and a politically complex ‘policy problem’ are confronted here, and acknowledgement of the latter directs research into the realms of decision-making and policy-implementation iteration in rural areas. Key themes in the understanding of these matters are those of central-local state relations, inter-agency relations and public-private sector relations, all of which should figure prominently in any conceptualisation of policymaking and implementation in rural areas. One final factor which invites conceptual clarification is that of the specificity of rurality as a policy-moulding phenomenon. The idea is introduced of a ‘rural dimension’ which presents a spatial facade to aspatial structures and processes.     

A modified parameterization of flux-profile relationships in the surface layer using different roughness length values for heat and momentum

The surface-layer flux-profile formulae of Louis (1979), used in many atmospheric models, are modified in a simple way to allow for different values of the roughness lengths for heat and momentum. The modified set of formulae simplifies the calculation of surface-layer fluxes over most natural land surfaces, where the roughness length for momentum can be almost an order of magnitude greater than that for heat.     

Some Biases in Sampling Multilevel Piezometers for Volatile Organics

Multilevel piezometers are cost-effective monitoring devices for determining the three-dimensional distribution of solutes in ground water. Construction includes flexible tubing (plastic or Teflon®). Their sampling is subject to a number of'potential biases, particularly: (1) losses of volatile organic solutes via volatilization, (2) sorption onto the flexible tubing of the piezometers, (3) leaching of organics from this tubing, and (4) collection of unrepresentative samples due to inadequate piezometer flushing. It is shown that these biases are minimal or are easily controlled in most situations.
Another source of bias has been recognized. Organic solutes present in ground water above the screened level can penetrate the flexible plastic or Teflon tubing and contaminate the sampled water being drawn through this tubing. Laboratory tests and field results indicate this transmission causes low organic contaminant concentrations to be erroneously attributed to ground water which is free of such contaminants. The transmitted organics apparently desorb from the plastic tubing during flushing of even 40 piezometer volumes.
Recognition of this transmission problem provides for a better interpretation of existing organic contaminant distribution data. Caution is advised when considering the use of these monitoring devices in organic solute contaminant studies.     

Stable isotope compositions and water contents of boninite series volcanic rocks from Chichi-jima, Bonin Islands, Japan

Measurements of stable isotope compositions and water contents of boninite series volcanic rocks from the island of Chichi-jima, Bonin Islands, Japan, confirm that a large amount (1.6–2.4 wt.%) of primary water was present in these unusual magmas. An enrichment of 0.6‰ in¹⁸O during differentiation is explained by crystallization of¹⁸O-depleted mafic phases. Silicic glasses have elevated δ¹⁸O values and relatively low δD values indicating that they were modified by low-temperature alteration and hydration processes. Mafic glasses, on the other hand, have for the most part retained their primary isotopic signatures since Eocene time. Primary δD values of −53 for boninite glasses are higher than those of MORB and suggest that the water was derived from subducted oceanic lithosphere.     

Isotopic study of the Manaslu granite (Himalaya,Nepal): inferences on the age and source of Himalayan leucogranites

A detailed isotopic study of the Manaslu leucogranite was carried out. A U-Pb age of 25 Ma and a whole rock Rb-Sr age isochron of 18 Ma were obtained, suggesting that the magmatic activity lasted at least 7 Ma. Initial Sr isotopic ratios are very high (0.740 to 0.760) and initial Nd isotopic ratios are low ( _Nd ⁱⁿ : –13 to –16), and they show the existence of large isotopic variations even at the metre scale. These are not the result of perturbations by fluids but rather they reflect the initial isotopic heterogeneity of the source material which has not been obliterated by magmatic processes (e.g. fusion, mixing by convection). These results also support the crustal origin of this leucogranite. The Tibetan slab paragneisses, whose Sr and Nd isotopic ratios are very similar to those of the granite at an age of 20 Ma, are the most probable parental material. Nd model ages for both the leucogranite and the gneisses are in the range 1.5–2 Ga. A model of formation of the Manaslu granite by coalescence of different batches of magma is in agreement with the present data.     

Le massif granitique de Lesponne (Hautes Pyrénées): Un exemple de massif plutonique hercynien à mise en place diapirique syncinématique

Résumé Le massif plutonique de Lesponne est un petit complexe de granitoÏdes calco-alcalins affleurant au coeur d'un important dÔme structural, au sein d'un encaissant micaschisteux ordovicien surmonté par des formations calcaréo-pélitiques dévoniennes. A partir de l'étude structurale du massif et de son encaissant d'où ressortent le parallélisme entre la forme allongée du massif et les mégastructures plissées hercyniennes, la continuité entre la foliation des granitoÏdes et la schistosité hercynienne majeure de l'encaissant, la zonation de la déformation de part et d'autre du contact massif encaissant, la simultanéité entre le thermométamorphisme et la déformation développés autour du massif, le massif de Lesponne est interprété comme un corps intrusif dont la mise en place diapirique est synchrone de la déformation hercynienne majeure.

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The Lesponne plutonic massif is a small complex of calcalkaline granitoids cropping out in the core of an important structural dome, within Ordovician micaschists covered by Siluro-Devonian calc-pelitic formations. The structural study of the massif and its country rocks shows that: 1) the long axis of the massif tends to be parallel to the main Hercynian folds; 2) the foliation of the granitoids pass in continuity to the major Hercynian cleavage of the enclosing rocks; 3) the zonation of the strain in the massif and its enclosing rocks is parallel to the envelope of the pluton and 4) the contact metamorphism was synchronous with the main Hercynian deformation. This leads to interpret the Lesponne massif as an intrusive stock diapirically emplaced during the main Hercynian deformation.

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Zusammenfassung Der Pluton von Lesponne ist ein kleiner Komplex kalkalkalischer granitischer Gesteine im Zentrum einer bedeutenden Domstruktur. Er ist umgeben von ordovizischen Glimmerschiefern und wird überlagert von einer kalkigtonigen Devonabfolge. Strukturelle Untersuchungen im Granitmassiv und in den benachbarten Randbereichen erbrachten folgende Ergebnisse: Parallelität der Längsachse des Massivs und der varizischen Gro\faltenstruktur, Fortsetzung der varisszischen Hauptschieferung der Randgesteine ins Massiv in Form einer Schieferung zonare Anordnung der Deformation beiderseits des Kontaktes zwischen dem Massiv und den Randgesteinen, Gleichzeitigkeit von Thermometamorphose und Deformation der Randgesteine in der Umgebung des Massivs. Daraus lä\t sich ableiten, da\ das Massiv von Lesponne einen Intrusivkörper darstellt, dessen diapirische Platznahme synchron mit der variszischen Hauptdeformation erfolgte.

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