PHOTOGRAMMETRIC MEASUREMENTS OF GLACIAL LANDFORMS

Photogrammetric methods using sequential aerial photography can provide the geomorphologist with comparative measurements of rapidly changing glacial landforms. Examples are given of eskers, kame and kettle areas, an ice-dammed lake and coastal features in south-east Iceland.     

Redistriution of Major Elements in the Alteration of Some Basic Lavas during Burial Metamorphism

An Ordovician geanticlinal marine sequence is exposed in theCentral West of New South Wales, Australia. The sequence containingbasic lavas, labile sedimentary, and proclastic rocks, has undergoneextensive adjustment during regional burial metamorphism. Thebasic lavas have a patchy coloration due to the formation ofalternation minerals of the prehnite-pumpellyite facies whichapperar to have formed during the metamorphism. The hererogeneousappearance of the basic lavas reflects a pronouced chemicaland mineralogical departure from the original composition. Twodiverging trends result. One leads to the production of a Ca-enrichedlithology, the other, which by far dominates in area at eachouterop, leads to a ‘spilitic’ lithology. The alterationdomains in many cases cross–cut all primary textural featureand their chemical variation does not correspond to likely variationsin the original lava composition.     

Microstructures of High-grade Metamorpbic Rocks at Broken Hill, Australia

Frequency distributions of true interfacial angles in high-grade,regional metamorphic rocks from Broken Hill indicate that interfacialtension varies with relative crystallographic orientation incommon minerals. In some single-phase aggregates (e.g. quartz,feldspar, garnet, and calcite) the grains are equant and polygonal,anisotropy of interfacial tension having only a small effecton the appearance of such aggregates. This is also true of two-phaseaggregates of these phases, but their appearance is complicatedby the presence of inclusions, the relative proportions of ihephases, and the characteristic dihedral angle formed by a grainof one phase in contact with two grains of the other. In phases for which interfacial tension is more orientation-dependent,crystal forms exert some control on the appearance of the microstructure.For example, in hornblende and pyroxene aggregates, some interfacesare parallel to planes of the form {110}, although most areirrational. In still more anisotropic phases, low-energy forms(e.g. {001} of biotite and {110} of sillimanite) are very stable,giving rise to a predominance of planar, rational boundariesover curved, adjustment boundaries. Anisotropy of interfacial tension is expressed in the shapesof inclusions. However, even where strongly anisotropic mineralsare involved, inclusions with partly planar boundaries occuralongside inclusions with completely curved boundaries.     

On longitudinal vibration of an elastic bar in a magnetic field

Summary The equations of elasticity, electromagnetic equations of Maxwell have been applied to investigate the longitudinal vibration of a partly homogenous, partly inhomogeneous elastic bar permeated by a magnetic field.     

ANALYTICAL AERIAL TRIANGULATION BLOCK ADJUSTMENT; THE DIRECT HEIGHT SOLUTION INCORPORATING TIE-STRIPS

The historical development of analytical aerial triangulation block adjustment is mentioned by way of introduction. The advantages of separating the plan and height adjustments are given and the observation equations of a typical adjustment section are analysed to show that this convenient practice is justified in normal circumstances. The principles of a direct solution of the normal equations suitable for a moderate-sized computer, are explained and developed in detail for the height adjustment. The advantages of tie-strips in the height adjustment are demonstrated and the difficulties which then arise are discussed. An approximate method which overcomes these difficulties is developed. Details of the computer programmes used are given in Appendix B.     

Baryt und ankerit aus Ammoniten des Berner Juras (Schweiz)

Barite has been found for the first time in the Swiss Jura (Hirni, Passwang). Small, white crystals of barite with yellow ankerite grow on calcite in different chambers of a Bajocian ammonite. Chemical data (by microprobe analysis) and lattice parameters (refined by leastsquares from powder patterns) are given for the two minerals. There is a distinct correlation between the cell dimensions and the chemical composition for both of them. The genesis is discussed.