Impacts of primary deforestation upon limestone slopes in northern Vancouver Island, British Columbia

Effects of deforestation upon slopes in limestones and in volcanic rocks in the Benson River valley, northern Vancouver Island, have been investigated quantitatively. Postlogging soil erosion and vegetal regeneration success were assessed by measuring soil depth, percent bare rock and moss cover, and the numbers and diversity of trees, shrubs, and plants on 25 sampling sites, each containing ten measuring quadrats selected at random. Sixteen sites were on the Quatsino Formation, a well-karstified limestone, and nine on the Karmutsen Formation of basaltic lavas. Eight sites were of virgin forest, 16 were logged between 1970 and 1983, and one (on limestone) was logged in 1911. Both bedrock types were significantly affected by the cutting. There was greater loss of soil and an increase in bare rock on the limestones. Erosion was increased significantly by burning on the limestones but not on the volcanics. Within-group comparisons on the limestones determined that steeper slopes and harder burned areas suffered the most and are slowest to regenerate. Volume of timber on the 1911 site was 19 percent of that in similar uncut forest sites. It appears that complete recovery on the barren limestone slopes will require at least some centuries.     

Tafoni on coastal slopes,South Devon,U.K.

Cavernous weathering (tafoni development) occurs on coastal slopes in greenschist bedrock at elevations up to 40 m above sea level. The freshly weathered surfaces of the cavern interiors are irregular in morphology, discordant to major rock structure, formed by substantially weakened rock and associated with granular weathering debris. The weathering debris contains soluble elements in proportions similar to those present in seawater, and the penetration of elements associated with sea salts into the weathering surface to estimated depths of at least 0·1–0·2 m is indicated by the presence of chlorine. Scanning electron microscopy and microprobe analyses suggest that rock breakdown occurs principally through limited chemical weathering at grain boundaries. The mechanism for the emplacement of marine salts within sheltered rock surfaces in the tafoni is postulated to be a combination of dry deposition under turbulent atmospheric conditions and wetting by coastal fog.     

Structural chemistry of synthetic cordierite: Evidence for solid solutions and disordered compositional domains in Bi-flux-grown Mg-cordierites

The structure, crystal chemistry, and microstructure of disordered and ordered Mg-cordierites synthesized in a bismuth oxide flux system have been studied by a combination of x-ray and neutron powder diffraction and quantitative x-ray microanalysis using analytical electron microscopy. Microchemical data obtained on Bi-flux cordierites using energy-dispersive x-ray analysis is interpreted through comparison with data collected on stoichiometric Mg₂Al₄Si₅O₁₈ glass and α- and β-cordierite samples synthesized by subsolidus crystallization of the glass. Bi-flux cordierites crystallize in both the hexagonal and orthorhombic polymorphs and contain 5 to 10 at% occupancy of bismuth on the C1 and C2 channel sites. The microstructure of Bi-flux α-cordierite is characterized by the existence of local domains of disordered cordierite solid solutions with variable composition and significant vacancy concentrations on the octahedral site. The β-cordierites have a more homogeneous microstructure but are still Al-deficient, Si-rich solid solutions.     

A comparison of the reactions to government taxation measures of twentieth century mining companies and nineteenth century pastoralists

This paper compares pastoralists in South Australia in the nineteenth century with Australian mining companies in the twentieth century as they resist the efforts of government to extract a greater proportion of the wealth created in the exploitation of natural resources. In effect, in both cases the struggle relates to the allocation of economic rent between private and corporate capital on the one hand, and the owners of the resources, the people of Australia, on the other. It is difficult not to be impressed by the similarities in the ideologies, objectives and strategies of these two groups of resource exploiters, separated though they are by over one hundred years.     

A comparison of two methods of estimating transpiration rates from a Sitka spruce plantation

Estimates of hourly transpiration from a 16–17 yr old Sitka spruce forest were calculated from the Penman-Monteith combination equation and compared with estimates from an eddy correlation/energy balance method.Canopy conductances were estimated from stomatal conductances measured using null balance diffusion porometers and took account of canopy variations of stomatal conductance and needle area index.Vertical heat fluxes were measured by the eddy correlation method; transpiration fluxes were then estimated from an energy balance of the forest.There was not a 1:1 relationship between the estimates of transpiration from the two methods. The major sources of error were concluded to be (i) difficulties of estimating the variation in stomatal conductance and leaf area through the canopy, (ii) errors in the value of total leaf area index, and (iii) errors in stomatal conductance measurements.The eddy correlation method was suggested as the more useful for future studies of the variation of forest transpiration in time or space, because the Penman-Monteith equation requires extensive biological measurements.     

Relationships between marginal thrusting and movement on major,internal shear zones in the Northern Highland Caledonides,Scotland

The development of the syn-metamorphic Sgurr Beag slide zone, a major ductile shear zone of initially low dip, caused at least 50 km north-western thrust displacement of part of the internal metamorphic complex of the Northern Highland Caledonides of Scotland. Initiation of the zone, and movements upon it, were earlier than formation of the marginal Moine Thrust zone. Movement on the zone followed but overlapped the peak Caledonian metamorphism and the mid to high amphibolite facies mineral assemblages, fabrics and structures produced during the development of the slide zone and those surviving from earlier events, were reworked under greenschist facies conditions during mylonitization associated with initiation of the Moine Thrust zone. Displacements on the slide zone and thrust movements were separated by emplacement of a regional suite of pegmatites and a considerable change of metamorphic grade. Thus, they may not constitute members of a progressive sequence of Caledonian thrusts formed over a short time interval. Rather, preliminary isotopic data may imply an interval of c. 25 Ma between movement on the slide zone and final, ductile translation along the Moine Thrust zone.