THE EIGHTIETH BIRTHDAY OF AN EMINENT WORLD CARTOGRAPHER

The multifaceted career and contributions of Professor Konstantin A. Salishchev, Chair of the Moscow University Department of Cartography and eminent world cartographer, are celebrated on the occasion of his eightieth birthday. These contributions include but are not restricted to: scholarly and administrative work in upgrading national atlas cartography worldwide, improvement of the quality of maps and cartographic instruction in higher education, publication of numerous excellent cartographic texts, formulation of the concept of the “cartographic method of research,” and promotion of international cooperation among cartographers and geographers through active participation and leadership in numerous world professional organizations. From the Russian original by I. D. Papanin, G. I. Rychagov, and A. F. Treshnikov.     

Are peatlands in different states with respect to their thermodynamic behaviour? A simple test of peatland energy and entropy budgets

Whilst all ecosystems must obey the second law of thermodynamics, these physical bounds and controls on ecosystem evolution and development are largely ignored across the ecohydrological literature. To unravel the importance of these underlying restraints on ecosystem form and function, and their power to inform our scientific understanding, we have calculated the entropy budget of a range of peat ecosystems. We hypothesize that less disturbed peatlands are ‘near equilibrium’ with respect to the second law of thermodynamics and thus respond to change by minimizing entropy production. This ‘near equilibrium’ state is best achieved by limiting evaporative losses. Alternatively, peatlands ‘far-from-equilibrium’ respond to a change in energy inputs by maximizing entropy production which is best achieved by increasing evapotranspiration. To test these alternatives this study examined the energy balance time series from seven peatlands across a disturbance gradient. We estimate the entropy budgets for each and determine how a change in net radiation (ΔR_n) was transferred to a change in latent heat flux (ΔλE). The study showed that: (i) The transfer of net radiation to latent heat differed significantly between peatlands. One group transferred up to 64% of the change in net radiation to a change in latent heat flux, while the second transferred as little as 27%. (ii) Sites that transferred the most energy to latent heat flux were those that produced the greatest entropy. The study shows that an ecosystem could be ‘near equilibrium’ rather than ‘far from equilibrium’.     

Non-tidal changes in the length of the day: 700 BC to AD 1982

Occultations and eclipses from ancient times down to the present are analysed to determine changes in the length of the day. By subtracting the expected tidal contribution from the observed changes, the non-tidal variations are obtained. The non-tidal varations are shown to occur on time-scales of decades and millennia.     

Contamination of the Marcy Anorthosite Massif,Adirondack Mountains,NY: petrologic and isotopic evidence

Oxygen isotope analyses of 101 samples from the Marcy Anorthosite Massif (61 from this study, 40 from Taylor 1969), indicate that two major and distinct processes of crustal contamination have affected the massif. Ninety percent of the 93 samples with over 65% plagioclase are enriched in ¹⁸O by 2.6 relative to normal anorthosites or gabbros: the average ¹⁸O for 83 enriched samples is 9.5 Depletions in ¹⁸O occur in 8% of the samples which have values ranging from 3.0 to 5.8 Only 2 of the samples fall within the normal magmatic range for anorthosites.Low ¹⁸O values of 3.0 to 5.8 in the anorthosite occur only near contacts, and a gradient in ¹⁸O occurs near the contact within the border zone of the massif. Low ¹⁸O values in both the anorthosite and adjacent wollastonite skarns (with ¹⁸O down to –1.3) were probably caused by isotopic exchange with heated meteoric water when the anorthosite intruded at shallow levels, prior to Grenvilleage ( 1.1 by) granulite facies metamorphism.The ¹⁸O-enrichment was ascribed to exchange between anorthosite and ¹⁸O-rich marble by means of a pervasive, H₂O-CO₂ fluid during the regional metamorphism by Taylor (1969). However, a number of lines of evidence argue against this hypothesis: 1) the preservation of premetamorphic low ¹⁸O values in anorthosite from the border zone as well as preserved gradients in ¹⁸O from a number of localities, 2) mass balance calculations of the amount of marble necessary to produce the ₁₈O enrichment 3) metamorphic phase equilibria which buffer and to low values, and, 4) recent oxygen isotope analyses show homogeneity which indicates that magmatic oxygen isotope compositions have been preserved. We evaluated the importance of magmatic assimilation of country rock at the present level of intrusion as an alternative cause of the ¹⁸Oenrichment. Samples from 2 distinct lobes of the massif were analyzed: the NE lobe where xenoliths of metasedimentary country rock are common, and the NW lobe, where xenoliths are scarce and the country rock is dominantly granitic. The mean values of ¹⁸O for these two lobes are 9.6 in the NE and 9.3 in the NW. Thus, magmatic assimilation at the present level of exposure probably had only localized and relatively minor effects on the oxygen isotope composition of the massif. This conclusion is supported by Rb/Sr data: variations in Rb content and (₈₇Sr/ ₈₆Sr)_i show that such crustal contamination is localized, generally occurring only in samples near the border zone. All of the available results suggest that the ¹⁸O-enrichment is a magmatic feature, acquired prior to intrusion at the present level of exposure.     

Oxygen isotope constraints on the petrogenesis of the Sybille intrusion of the Proterozoic Laramie Anorthosite Complex

The origin of monzonitic intrusions that are associated with Proterozoic massif-type anorthosite complexes is controversial. A detailed oxygen isotope study of the Sybille intrusion, a monzonitic intrusion of the Laramie Anorthosite Complex (Wyoming), indicates that either derivation from a basaltic magma of mantle origin with a metasedimentary component (∼20%) incorporated early in its magmatic history, or a partial melt of lower crustal rocks is consistent with the data. The oxygen isotope compositions of plagioclase, pyroxene and zircon from the Sybille monzosyenite, the dominant rock type in the Sybille intrusion, were analyzed in order to establish the isotopic composition of the source of the magma. Plagioclase δ¹⁸O values range from 6.77 to 9.17‰. We interpret the higher plagioclase δ¹⁸O values (average 8.69 ± 0.30‰, n = 19) to be magmatic in origin, lower plagioclase δ¹⁸O values (average 7.51 ± 0.44‰, n = 22) to be the result of variable subsolidus alteration, and pyroxene δ¹⁸O values (average 6.34 ± 0.38‰, n = 19) to be the result of closed-system diffusional exchange during cooling. Low magnetic zircons, which have been shown to retain magmatic oxygen isotope values despite high grade metamorphism and extensive subsolidus hydrothermal alteration, have δ¹⁸O values (7.40 ± 0.24‰, n = 11) which are consistent with our interpretation of the plagioclase and pyroxene results. Oxygen isotope data from all three minerals indicate that the magmatic oxygen isotope composition of the Sybille intrusion is enriched in ¹⁸O relative to the composition of average or “normal” mantle-derived magmas. This enrichment is approximately twice the oxygen isotope enrichment that could result from closed-system fractionation, rendering a closed-system, comag- matic petrogenetic model between the Sybille intrusion and the mantle-derived anorthositic lithologies of the Laramie Anorthosite Complex improbable. Received: 7 April 1998 / Accepted: 19 January 1999     

Alkaline hybrid mafic magmas of the Yampa area,NW Colorado,and their relationship to the Yellowstone mantle plume and lithospheric mantle domains

The Yampa volcanic field (late Miocene) consists of about 70 outcrops of monogenetic cinder cones, lavas, dykes, volcanic necks and hydrovolcanic pyroclastic deposits and is situated in the most northerly part of the Rio Grande rift. Contemporaneous extension in this part of the rift was small, but there is geological and geophysical evidence that, by the late Miocene, the area was underlain by hot asthenosphere convected by the Yellowstone mantle plume. The Yampa rocks are mafic and chemically diverse, including basanites, alkali basalts, potassic trachybasalts, hawaiites and shoshonites. About half the rocks bear the xenocryst suite feldspar, pyroxene, Fe–Ti oxide, amphibole, biotite. There is a tendency for xenocryst-free rocks to be the most mafic, interpreted to indicate that the xenocrysts are cognate, and represent cumulate material from fractional crystallization of the magmas in deep crustal magma chambers. The elemental and isotopic (Nd and Sr) variations can be modelled by mixing variable proportions of partial melts of local lithospheric mantle with an OIB end-member formed by partial melting of asthenosphere. The OIB end-member appears to have the elemental and isotopic composition of typical Northern Hemisphere OIB, in particular the plume-derived basanites of Loihi seamount, Hawaii. The OIB end-member at Yampa is interpreted to have been derived from mantle convected in the Yellowstone mantle plume.     

Geomorphic controls on mercury accumulation in soils from a historically mined watershed, Central California Coast Range, USA

Historic Hg mining in the Cache Creek watershed in the Central California Coast Range has contributed to the downstream transport of Hg to the San Francisco Bay-Delta. Different aspects of Hg mobilization in soils, including pedogenesis, fluvial redistribution of sediment, volatilization and eolian transport were considered. The greatest soil concentrations (>30 mg Hg kg⁻¹) in Cache Creek are associated with mineralized serpentinite, the host rock for Hg deposits. Upland soils with non-mineralized serpentine and sedimentary parent material also had elevated concentrations (0.9–3.7 mg Hg kg⁻¹) relative to the average concentration in the region and throughout the conterminous United States (0.06 mg kg⁻¹). Erosion of soil and destabilized rock and mobilization of tailings and calcines into surrounding streams have contributed to Hg-rich alluvial soil forming in wetlands and floodplains. The concentration of Hg in floodplain sediment shows sediment dispersion from low-order catchments (5.6–9.6 mg Hg kg⁻¹ in Sulphur Creek; 0.5–61 mg Hg kg⁻¹ in Davis Creek) to Cache Creek (0.1–0.4 mg Hg kg⁻¹). These sediments, deposited onto the floodplain during high-flow storm events, yield elevated Hg concentrations (0.2–55 mg Hg kg⁻¹) in alluvial soils in upland watersheds. Alluvial soils within the Cache Creek watershed accumulate Hg from upstream mining areas, with concentrations between 0.06 and 0.22 mg Hg kg⁻¹ measured in soils 90 km downstream from Hg mining areas. Alluvial soils have accumulated Hg released through historic mining activities, remobilizing this Hg to streams as the soils erode.     

DO WE NEED TO MODEL PLATES AT ALL?

The historical method of obtaining equatorial coordinates for stars observed via astronomical photography has been to convert the measured coordinates to equatorial coordinates with the aid of a plate model which corrects for a variety of effects. However, we now have at our disposal novel smoothing techniques, of considerable generality, which in conjunction with modern star catalogues can reproduce the essence of the plate model while dramatically minimizing both the fortuitous and systematic errors of observation. In this paper we demonstrate that, with this technique and extant catalogues, one can obtain, with at least the same precision and better accuracy, the information necessary to transform the measured coordinates successfully into standard coordinates by a process that involves no sophisticated model for the plate. Using external checks we estimate the increase in accuracy to be of the order of 25 per cent.     

Mid-level clouds over the Sahara in a convection-permitting regional model

Climate Dynamics - The simulation of Saharan mid tropospheric clouds is investigated with the weather research and forecasting (WRF) regional atmospheric model at convection permitting...