Search

Ascending, descending, and horizontal (circular) methods of paper chromatography were explored and compared. Circular chromatography was found to be the most suitable; it requires shorter development time, has more definite Rf values, less tailing, higher sensitivity, and better precision than ascending or descending methods.A methyl ethyl ketone: hydrochloric acid solution (93:7 v/v) is used as a developing solvent for cobalt, copper, and nickel, and a 1-butanol: 1 N hydro–chloric acid solution (7:3 v/v) is used as a solvent for zinc. Good separations were obtained with these solvents and no critical interferences were noted. Benzidine – rubeanic acid is used as a color indicator for cobalt, copper, and nickel; and dithizone (0.01%) for zinc. This method has an absolute sensitivity of 0.005 μg for zinc, and 0.02 μg for cobalt, copper, and nickel. Precision is estimated at ± 10%.Methods have also been developed for determining bismuth, silver, and tin.The separation of elements from complex mixtures by paper chromatography and by quantitative determination of the amounts present by emission spectrography have been investigated. This rarely considered process offers promise, because the sensitivity of several elements is higher in emission spectrography than in colorimetry.

In recent years, the term "train' has become increasingly important in descriptive structural geology. Expressions like "train facies' or 'strain fabric' (formerly Veformation fabric') have been introduced (Halasen 197 1, Clifford 1972), which are exclusively related to tectonic flow, and these are used with increasing frequency, while use of the term strain is comparatively uncommon in papers on non-diastrophic deformation or flow of lava and magma. If this trend' continues 'geologic strain' will become synonymous with 'tectonic flow'. It need hardly be pointed out that strain is not a structural property but rather a general concept of theoretical mechanics, and that it is not the only method of specifying a coptinuous deforn~ation (minus translation) It has become clear, however, that the strain concept, rather than alternative methods, will be an important tool for the modcrn structural geologist (cf. Ramsay 1969). Clifford's ( 1972) study is essentially an application of the strain theory to the wall rock deformation of a granitic batholith. The paper employs such engineering terms as 'pure shear' and 'simple shear', as well as tectonic expressions related to strain. These technical terms have been unequivocally defined in standard books of theoretical mechanics, and/or in recent textbooks of structural geology (Table 1 ). Clifford ( 1972) does not use 'pure shear' and other expressions in their standard sense, neither does he re-define his technical vocabulary. The reader is forced to deduce from the general context which meaning is to be attached to the various terms (Table 1 ). Clifford ( 1972) prescnts convincing evidence that the triaxial strain of the wall rocks is markedly heterogeneous, i.e. that the magnitude of horizontal compressive strain increases toward the contact of the batholith. Me then claims that this inhomogcneous deformation corresponds closely to irrotational strain (labelled 'pure shear in three dimensions', see Table I ) , and attributes it largely to axially symmetric inflakion of thc uiaconsolidatcd batholith. Of gcomctric necessity, most heterogeneous strains involve large components of rigid rotation, i.e. the local strain is generally rotational (Ramsay 1969, p. 52) . Figure 1 illustrates schematically what heterogencous strains might be expected around uniformly expanding circular diapirs. The cross-sectional strain (normal to the axis of diapirs) must be irrotational (Fig. la ) , but large components of rigid rotation occur in other sections (Fig. l b ) . These components will tend to be greatest where geometry of the granite contact is approximately cylindrical. Inflation of noncircular diapirs will generally lead to rotational crosssectional strain in the sul-rounding rocks. Clifford ( B 972) considers two general models of radial horizontal compression of the supracrustal wall rocks, ( 1 ) by emplacement of a conical granitic mass, and (2) by late-stage horizontal "inflation' of a batholith. He asserts that the former model is characterized by biaxial strains (labelled 'constrictive', Table 1 ), and that the latter model involves an early phase of subvertical simple shear parallel to the contact. Figure 1 b illustrates that subverti

Stromatoporoids are abundant in parts of the Sayabec, St. Leon, and Mont Wisick formations of Wenlock and Ludlow age in eastern Quebec, Canada. The fauna is a mixture of species from \\:enlock strata of northern Europe, the Wenlock and L~~dlow beds of Baie des Chaleurs, Quebec, and Yiagaran rocks of the Great Lakes region. Clalhrodittyon cvicknroyi ancl Slromato ora prima show the affinity of t,he fauna to that described by Parks from Baic g es Chaleurs. Densasfroma nstroiles indicates a close connection of the fauna with the rocks of J1,'enlock age in England and the Baltic area. Sfromalopma antiqfca shours the affinity of the fauna to that of central North America. EGclimadictyonfastigiatum is a widespread species in all these regions. A new species of Actinodictyon (8. queberense) is described. Two unnamed species of Strmatopwa and Clalhrodictyon cf. pdolica make up the rest of the fauna. Silurian carbonates of the region between the Temiscouata and Matapedia Valleys in the Appalachian area of Quebec contain abundant stromatoporoids and corals. LittIe has been written about the paleontology of this area even though an extensive mapping program has been in progress by geologists of the Quebec Department of Natural Resources during the past 7 years. Stromatoporoids were collected by Hubert while he was employed as a geologist on field parties in this area during the seasons of 1959 and 1960. He visited most of the fossil localities between the Temiscouata and Matapedia Valleys found during reconnaissance and detailed mapping by Beland (1960), Lesperance (1960), and Lajoie (1963). The only systematic work on the stromatoporoids of eastern Canada was based on material collected by Schuchert and Dart (1926), Northrup (1939), Crickmay (1932), and Alcock (1935) around the shores of Baie des Chaleurs and published by Parks in 1933. The belt of Silurian sedimentary rocks on which this paper is based is separated from those of Baie des Chaleurs by a belt of schistose Devonian rocks but the similarity of the two stromatoporoid faunas permits a correlation to be drawn between these two areas. Although stromatoporoids are abundant in the limestone formations in this area, only a few of them are well enough preserved for identification. Many seem to have lost their structure through recrystallization. 'This paper is based on part of a thesis submitted by Hubert to the Faculty of Graduate Studies and Research, McGill University, in partial fulfilment of the requirements of the degree Master of Science (Hubert 1963).

Leaf compressions, spores, and pollen grains referrable to about 45 species were collected from a series of fine silts and coal stringers in the Parsnip River valley of the Rocky Mountain Trench. The leaf assemblage described in this paper indicates a late Maestrichtian to Danian age, somewhat younger than generally comparable assemblages previously reported from the lower part of the Edmonton Formation of Alberta, and from the Hell Creek, Lance, and Fox Hills Formations in the western interior of the United States. It also contains several species reported from the Nanaimo Group on eastern Vancouver Island. Plant microfossils (to be described in a later paper) include species of Glyptostrobus, Sciadopitys, Aquilapollenites, Pistillipollenites, Alnus, Myrica, Tilia, Pterocarya, and Carya, together with tricolpate pollen of uncertain affiliation. The combined leaf and microfossil assemblages indicate a warm mesothermal and humid paleoecological setting of low relief, suggesting absence of major mountain ranges westward to the Pacific Ocean.

The results of two previous papers by Chinnery published in 1963 and 1964 are used to calculate the distribution of stress that is present after the formation of a strike-slip fault. The pattern obtained shows that although the initial stress is reduced over most of the length of the fault, there are strong concentrations of shear stress near the ends. It is therefore suggested that secondary faulting is due to these end effects, and patterns of likely modes of secondary faulting are shown. The geological implications of these results are discussed in another paper, on the geological aspects of Secondary faulting.

This summary of papers and discussion makes no real attempt to be comprehensive or complete, instead I have tried to select those contributions which seem to me to be most interesting, new, and significant. This summary is a personal view, and thus it suffers from personal bias and errors of omission and commission. I hope, however, that the more important highlights of this stimulating symposium will at least be identified. The papers clearly are of three main types, depending on whether the emphasis was on observational data, theory, or speculation on the large-scale effects of surges; I have grouped and discussed them accordingly.

Although Symons' (1973) study of the Topley Intrusions is an important contribution to unraveling the Jurassic polar wander path for North America, several difficulties become apparent on reading his paper. He states that a major object of his study was to add data to help clarify the Jurassic portion of the polar wandcr curve. However, he is apparently unaware of our contribution in that area, which was published last year (Steiner and Helsley 1972). Quite to the contrary of his assertion that no confidence limits are given for the Kayenta and Sumrnerville poles, in that paper all relevant statistical information is given for the data of our earlier abstract (Steiner and Helsley 197 1 ) . In comparing his results to other published Jurassic data, Symons makes several inaccurate statements regarding the White Mountain Magma Series data (Opdyke and Wensink 1966), referring to it as reliable and saying that it predates the Topley pole by 40 m y . Since many workers, in comparing their data to published data, consider the White Mountain result reliable, issue is taken here with that concept. As was discussed in our paper, the White Mountain Series pole: ( I ) is not 180 m.y. old, ( 2 ) spans a time period of up to 100 may., from 199 to 96 m.y. (Foland 1969; Foland et al. 1971; Armstrong and Stump 1971 1, and (3) is derived from widely scattered site mean poles, indicative of either secondary component remaining or individual plutons having been magnetized at different times during the long time between Triassic and Cretaceous spanned by the intrusions. The White Mountain data are suspect in that the normal results in the mixed polarity study are associated mainly with monzonites and all give a present pole position while the reversed results are all from gabbroic compositions and give a streak of poles away from the Cretaceous pole. Therefore, the White Mountain pole cannot be taken to represent a reliable Jurassic pole to which other data from North America can be compared. Furthermore, the White Mountain pole does not predate the Topley Intrusions but includes them within its age span. Since the currently accepted age for the boundary of the Jurassic and Cretaceous Periods is 136 m.y. (Geol. Soc. Phanerozoic time-scale 1964), the Topley Intrusions, within their error limits (139 * 4 m.y.), fall on the Jurassic-Cretaceous boundary. Therefore, Symons' statement that his pole position, intermediate between those of the Jurassic and Cretaceous, is "contrary to the static TriassicJurassic pole position interpretation of Steiner and Helsey (1971 ) " makes no sense. The age of his pole position is at the end of the period to which we referred. Moreover, we would likc to reiterate our findings (Steiner and Helsley 1971; 1972) that the pole relative to North America apparently remained in its Triassic position until post 150 m.y. (Summerville time) and then moved very rapidly to its Cretaceous position. New data of ours to be published from uppermost Jurassic sedimentary rocks of the Colorado Plateau support that conclusion. Although the Topley Intrusions pole has a rather large confidence ovd, the position of the pole is in agreement with the concept of rapid movement in the time post 150 m.y. (His pole, at about 139 m.y., is almost half way between Triassic and Cre

Mothersill and Fung (1972) declare in the introduction of their paper that one of the aims "of this investigation was to determine the Quaternary stratigraphy . . . of the northern part of the Lake Superior basin". Therefore, a reader expects not only new original data, but also consideration of generally accepted stratigraphic criteria including the code of the American Commission on Stratigraphic Nomenclature ( 1961 ), and correlation with up-todate stratigraphic schemes of other authors. Unfortunately, the authors are confusing rock stratigraphic with time stratigraphic terms, are defining a time transgressive contact as the boundary between two established time stratigraphic units, and are not using the latest references for correlations. To some extent, this has been done already before by the senior author (Mothersill 197 1 ) , and the present paper of Mothersill and Fung (1972) repeatedly refers to his equally disputable stratigraphic statements. In their Table 1, Mothersill and Fung (1972) call Farrand's (1969) names of sediments encountered in cores of Lake Superior as "Time Stratigraphic Units". They could be considered informal rock stratigraphic units, but never time stratigraphic. No reasons are given why, in the same table, the authors (and also Mothersill 1971) have chosen Hough's (1958) very seldom used classification of the Wisconsin Stage, when they already indicate in the table, that most of Hough's substages (five out of six) are missing in the area; the only one listed as present (Valders) is not a term introduced by J. L. Hough. Why not refer to any other more recently published and widely used classifications of the last glacial stage in the Great Lakes Region? No explanation is given by Mothersill and Fung ( 1972) and Mothersill (1971 ), why they prefer 11 000 yr B.P., based upon a few black carbon dates (Flint and Deevey 1951) for dating the Valders advance, rather than using, or at least mentioning the 18850 + 100 yr B.P. average date (Broecker and Farrand 1963) of the Two Creeks forest bed, which was flooded and the trees killed, during the Valders advance. The latter date is based upon a special investigation of new material and comparison with more than twenty other radiocarbon dates. One of the most confused concepts in Mothersill and Fung (1972) is the HolocenePleistocene boundary. They say that Mothersill ( 1971 ) , "defined the basal contact of the claysilt sequence with the underlying gray varves as the Holocene-Pleistocene boundary". They also state that this contact represents an unconformity. Comparison of their Tables 1 and 3 shows that chronologically this unconformity is partly in the Pleistocene, partly in the Holocene: in Table 3 the extrapolated dates of basal Holocene range from 5400 + to 13 000 2, while in the 'Time Scale' of Table 1 the date of 11 000 yr B.P. is included in Pleistocene. The Holocene-Pleistocene boundary is a timestratigraphic term and therefore it can not fluctuate over a wide span of time. It may be noted that the INQUA Commission on the Holocene announced at the VIII INQUA (International Union for Quaternary Research) Congress in Paris, 1969, that "For the reference boundary between the Pleistocene and Holocene with world-wide validity, the Commission proposes a date at about 10,000 B.P. measured in radiocarbon years" (Hageman 197 1 ) . Neither Mothersill ( 1971 ) nor Mothersill and Fung (1972) have proven that the contact between the clay-silt and underlying varves in

The analytical portions of a recent paper by Kretz (1970) leave certain questions unanswered, and raise some others. (1) In Table 11, what is the signiiicance of the 10-ml aliquot? If the solution is not diluted, why list an aliquot? It is hard to see how sodium and lithium can be determined at the same dilution level for the concentrations involved, unless an unusual sodium line was used. Wavelengths are not listed in the paper. The lithium concentrations for samples 1 and 8, Table V, are so close to the detection limit that use of two significant figures is questionable. (2) Kretz used Angino and Billings' (1967, p. 96) hydrofluoric-sulfuric decomposition although even those authors state that ". . . It is probably simpler, however, to use an acid other than sulfuric. . .". Kretz did change "subsequently" to perchloric acid, but no indication is given of which results were obtained with which acid. The 0.64% lanthanum in the solutions for calcium and magnesium determination may not be sufficient to overcome the chemical interference of so much sulfate ion, and may account for the small but persistent negative bias in the results for those metals (Table 111). Solutions from hydrofluoric-sulfuric and similar decompositions are not generally considered suitable for aluminum determination (Abbey 1 9 7 0 ~ ) . The only example in the literature is that of Galle (1968), and he followed up his decomposition with a pyrosulfate fusion. (3) Is it really necessary to show calibration curves? Would not a simple statement be sufficient to indicate that all were linear? If curves must be shown, why is there none for lithium? More significantly, why is there no indication of the composition and manner of preparation of the standard solutions used for calibration? (4) In Table 111, Flanagan ( 1967) is quoted for the "given" values for G2, GSP 1, and AGV 1. A more comprehensive compilation is available (Flanagan 1969), and also a critical study of the data (Abbey 1970b). Admittedly, the assigned values in the latter study do not differ greatly from those in Flanagan (1967), but it must be remembered that one set of analyses by one laboratory does not make a standard sample. (5) Is it really necessary to d e h e "mean" and "standard deviation"? I

In this paper, Lines and Jones (1973) attempt to apply the finite difference method of numerical analysis to a Zdimensional model. The only real problem is due to the impossibility of separating the component equations for any direction of polarization. The details of the method appear in Lines (1972). Unfortunately, these methods are in serious error and the problem mentioned above has nor been solved. Tt i s therefore certain that the results described in this paper are incorrect, especially near and at structural discontinuities. These are, however, the only regions in which there is any interest. On page 40 of Line's thesis, equations 3.2, 3.3, and 3.4 give the non-homogenous equations that are to be solved for the components of the electric field. It can be seen that each equation contains derivatives of all three field components. For convenience we will write equation 3.2

Except for one point we do not wish to argue the details of our paper. The data are on record and the curious reader is in a position to decide for himself. However, we feel we must point out that the magnetization of site BH2 cannot be "envisaged as made up of one main component which is the lone survivor after cleaning at 600 "C, and of several other components oriented at random", as Pearce and Freda suggest, since the removal of random components could not cause the observed mean direction change of more than 30" (see our Table 11, (Robertson et al. 1968, p. 1179)). Oddly enough Pearce and Freda do agree with the main point of our paper when they state "Robertson et al. have indeed clearlv demonstrated that Black's data cannot be conkdered as conclusive ..." The magnetism of the Perry Formation is so complex that the results are inconclusive and cannot be used as a basis for arguing that Newfoundland has rotated.

Four erosional unconformities have been recognized within the Mesozoic-Cenozoic succession on the Scotian Shelf, on the basis of data from high resolution seismic reflection profiles. Older unconformities are known from well data and others may be revealed by detailed biostratigraphic studies.The oldest of the four unconformities discussed in this paper is of Early Cretaceous age and appears to mark, with discordance, the boundary between Jurassic and Cretaceous strata on the western part of the shelf. A second angular unconformity, of Late Cretaceous age, has been recognized on the central part of the shelf where the basal part of the Banquereau Formation (Tertiary and uppermost Cretaceous) oversteps the zero-edge of the Wyandot Formation (Upper Cretaceous) and lies upon truncated beds of the Dawson Canyon Formation (Upper Cretaceous). Cut-and-fill relationships characterize a third unconformity developed during Early Tertiary time. A fourth unconformity was developed in Late Tertiary – Pleistocene time by fluvial processes and later by glacial processes. Although in many areas the latest unconformity appears to be the most conspicuous one on the shelf, its configuration closely follows the geomorphic expression developed during the previous period of erosion. The regional extent of the Cretaceous unconformities is not known, and they might only occur near basin margins and on structural and basement highs.

David et al. (1974a, b) present a different approach to factor analysis and are to be commended for bringing to the attention of the geological community the existence of a method of data analysis called Correspondence Analysis. However, before the utility of the technique can be properly evaluated on the basis of the set of data used in the paper, a number of points should be clarified. Principal Components Analysis (PCA) is not synonymous with Ror Q-mode factor analysis (Mulaik 1972; Davis 1973). The usual procedure (Klovan 1968 ; Rummel 1970; Davis 1973) is to begin with a PCA and then rotate a subset of the principal component axes according to some substantive criterion (for example, simple structure: Harmon 1967; Rummel 1970). The most common method of orthogonal rotation is the varimax procedure (Kaiser 1958). Oblique rotational methods (Hakstian 1969; Rummel 1970; Mulaik 1972) where the orthogonality constraints of the varimax scheme are relaxed are also utilized (Hitchon et al. 1971). The authors state (p. 13 1) that the 'technique' (correspondence analysis) is designed to extract the maximum of information from an array of positive numbers. They also emphasize the saving of computer time and storage (and by inference money). The latter aspect may be the most redeeming quality of their Correspondence Analysis. The transformation which they employ (p. 134) is a bounding type of data matrix transformation (Rummel 1970) and not standardization. Standardization in the strict sense involves subtracting the mean of a variable from each original observation and dividing the resultant

The existing techniques for the quantitative evaluation of vertical crustal movements from geodetic spirit levelling have one common feature. They can deal only with a complete network of systematically relevelled connected lines. This paper presents a method, based on the least-squares fitting of a velocity surface, capable of using scattered as well as connected relevelled segments. A facility to choose a specific level of statistical significance of the results is built in. The performance of the method is tested on data for the vicinity of Chesapeake Bay. The results compare well with those of the U.S. National Geodetic Survey.

This paper brings together the paleomagnetic results from miscellaneous unmetamorphosed diabases and their remagnetized adjacent country rocks collected from widely separated locations within the Canadian Shield. Most of these diabases are tentatively assigned to the Franklin and Mackenzie Igneous Episodes on the basis of their paleomagnetic poles and their geological relationships with previously assigned diabases. The tentative Mackenzie pole from the present work is 02.S0N, 169.8"W (N = 12, K = 35, As5 = 7.4). Cet article rCuni les rksultats palComagnktiques de divers diabases non-rnCtamorphisCs et de roches contigues remagnCtizCs receuillis de lieux espacCs dans le bouclier canadien. Le plupart de ces diabases sont attribuks tentativement B base de leur p8les palkomagnktiques et leur relations gCologiques avec des diabases dtji attribuCs aux Cpisodes ignks de Franklin et Mackenzie. Le p81e d'essai de Mackenzie du travail prksent est de 02.5"N, 169.8"W (N = 12, K = 35, A, = 7.4). [Traduit par le journal]

Analysts of texture, mineralogy, and chemistry of bottom sediments in Conception Bay, southeastern Newfoundland has shown: (1) Sediment texture is related to water depth, (2) water depth, CaCO3 content, organic-C content, and feldspar/quartz peak area ratios are all related to sediment mean grain size, (3) concentrations of major elements are related to clay, organic-C, and CaCO3 contents and feldspar/quartz peak area ratios of sediments, (4) concentrations of trace elements are related to clay and organic-C contents, (5) sediment pH is related to Organic-C and CaCO3 contents, and (6) sediment temperature is related to water depth. These relationships indicate that four interrelated factors regulate sedimentary geochemical variables: Source and depositional environment are primary factors that regulate the type of solid components comprising sediments and sediment grain size, respectively; grain size is a secondary factor that regulates mineral and organic matter content of sediments; solids composition (quartz, feldspar, clay minerals, CaCO3, and organic matter) is a tertiary factor that regulates sediment chemistry. Sediment pH is regulated mainly by CaCO3 content and temperature is regulated by depositional environment. Particular attention should be paid to these factors when conducting sedimentary geochemical investigations.A surface layer of brick-red, iron-enriched sediment around Bell Island, which is the waste product of former mining activities, provides the only evidence of man's alteration of the Conception Bay bottom environment. Therefore, trace and major element concentrations in bottom sediments described in this paper are natural background levels which can be utilized for a future comparative study in the event of increased urbanization and/or industrialization of the Conception Bay area.Results of echosounder profiling have shown that the physiography of Conception Bay has been glacially modified. Four sets of marine terraces have been identified at water depths of 110–120, 90, 70–75, and 20 m. These terraces are correlative with others found elsewhere in Atlantic Canada.

In the continuum approach to problems of geologic mechanics, the ground surrounding a deformation zone is replaced mathematically by an idealized material that deforms in accordance with principles of continuum mechanics. Studies published to date have been rather few in number and have often followed a methodology characterized by restrictive material property and boundary condition assumptions. In order to avoid these difficulties, emphasis in this paper is given to modern numerical methods. Discrete-element formulations of matrix structural analysis are shown to be particularly useful, inasmuch as they are adaptable to solutions of systems characterized by nonlinear anisotropic materials, heterogeneously distributed, containing internal discontinuities, and of arbitrary topographic or internal boundary configuration.

A secondary fault is defined as a fracture which arises as a direct result of movement on a master transcurrent fault. Some previous approaches to the study of secondary faulting are discussed, and fallacies in the arguments of McKinstry (1953) and Moody and Hill (1956) are pointed out. The effect of movement on a fault is to reduce the initial shear stress everywhere except in the vicinity of the ends of the fault, where it causes complex additional stresses (see first paper in this series on the theoretical aspects of secondary faulting). Thus it is proposed that secondary faulting is an end effect of a master shear movement, and on this basis six major modes of secondary faulting, labelled types A to F, are described. The usefulness of these results in the analysis of fault systems is illustrated by applying them to the Alpine, San Andreas, and Mac Donald faults. In each case it is possible to predict or explain the curvature, location, and sense of the secondary faults in the area. In addition, the development of the master fault may be traced by locating the ends of the shear zone at various times in the past.

The paper investigates the relationships that exist between the airform pattern, hydrology, and ontogeny of the muskegs of Canada. A new interpretive classification based on the concept of hydroform is proposed and some practical examples of its application are given. Cet article etudie les relations existant entre 1' "airform pattern", I'hydrologie, et I'ontogenese des fondrieres de mousse du Canada. Une nouvelle classification d'interpretation basee sur le concept d' "hydroform" est proposee. Quelques exemples pratiques de son application sont donnks. [Traduit par le journal]

Previous investigators have shown that natural chromium-bearing spinel solid solutions adhere closely to the general formula (Mg, Fe++) (Cr, Al, Fe+++)2O4 and may therefore be graphically portrayed in a triangular prism, the length of which represents the ratios MgO/FeO, and the cross section the relative proportions of Cr2O3, Al2O3, and Fe2O3. In this paper, theoretical expressions are derived whereby the prism may be "contoured" for conditions of isothermal–isobaric equilibrium according to (a) the spinel compositions that may coexist with olivine or pyroxene having specific MgO/FeO ratios; (b) the activity ratios of Cr/Al, Cr/Fe+++, or Al/Fe+++ that obtain in the environments in which the spinel solid solutions form, and (c) the oxygen fugacities that accompany formation of spinel in systems containing olivine (forsterite–fayalite) and orthopyroxene (enstatite–ferrosilite). Rough "working" values for the thermochemical coefficients involved are estimated from limited calorimetric data and chemical analyses of spinel–olivine and spinel–orthopyroxene pairs.

The principle of constituent analysis is introduced. Assuming that a component (end member) consists of n variables in percentage form and that m different components (m ≤ n) constitute each of N samples, the samples can be treated as N points in m-dimensional space. Points represented by m end members are characterized by being non-coplanar and non-collinear in m-dimensional space. The amount of the mth end member contained in a sample is calculated as Xm−1i/Xm−1 m, where Xm−1 is the length of (m−1)th orthogonal axis; i and m in subscript Xm−1 are for the sample and mth end member, respectively; and the end members are successively put on the origin of the coordinate, X1, X1−X2, X1−X2−X3,…, and X1−X2 …−Xm−1 axes.In a metamorphic rock, m points are equivalent to constituent minerals. If the chemical compositions of constituent minerals and the bulk chemical composition of the rock are known, the method outlined in this paper provides information on equilibrium assemblages and allows computation of the amounts of constituent minerals.

During June and July of 1968 the Geological Survey of Canada participated in the llominion Observatories crustal seismic experiment centered on the (3renvllle front in north central Quebec. Participation was to the extent of recording the shots of the experiment at locations subadjacent to the Appalachian front from Kimouski and IiiviPre Du I,oup, Quebec to Edmundston, New Brunswick. Recordings from a three component station were taken on photographic paper, and also on frequency modulated magnetic tape. A preliminary study of 19 Pn first arrivals results in velocities for the upper mantle ranging from 8.08 km/s to 8.23 km/s with a mean of 8.15 km/s under the shots. Under the stations Pn events show velocities for the upper mantle ranging from 7.81 kn~/s to 8.65 km/s with a mean of 8.15 km/s. A least-squares time-term analysis for Pn events results in a velocity oi 7.94 -t 0.42 km/s at the 90% confidence level. This solution shows large residual times ranging between -+0.7 s which probably imply complex geological structures near the shots and the recording stations. Time and distance data are summarized as well as details of computations. Pendant les mois de juin et juillet 1968, la Commission Gtologique du Canada a pris part aux expiriences sismiques efiectuecs sur la crofite terrestre par lcs Observatoires du Dominion et centrCes sur le front Grenville du nord du QuCbec central. Sa participation s'est limitCe h I'enregistrement des tirs de llexpCrience h des localites adjacentes au front Appalachian et sises de Rimouski et Riviere-du-Loup, P.Q. B Kdmundston N.B. L'enregistrement sur papier photographique et aussi sur bande magnCtique 2 frkquence modulde, fut rCalisC h l'aide d'une station B trois parties composantes. Une Ctude priliminaire des temps de premikre arr~vie de 19 ondes Pn a donnC des vitesses de propagation allant de 8.08 km/s B 8.23 km/s (la moyenne ktant de 8.15 km/s) dans le manteau supC.rieur, lors des Cbranlements. Sous les stations, on obtient pour le manteau qupdrieur, des vitesses de propagation de ces ondcs Pn allant de 7.81 kmis h 8.65 km/s avec une moyenne de 8.15 km/s. l,'analysc, par la mtthode des moindres carrCs, du terme temps pour les ondes Pn a produit une vitesse de 7.94 2- 0.42 km/s B un niveau de confiance de 90%. Cette solution fait boir des temps rbiduels considtrables variant entre -i- 0.7 s, ce qui indiquerait sans doute des str~ictures gCologiqucs complexes pr2s des points de tir et des stations d'observation. On rksume les donnces sur le temps et les distances ainsi que les artifices de calcul. [Traduit par le journal]

The difficulties of the aerial survey of the Aletsch Glacier lay in establishing ground control in the high mountains and locally on the moving glacier surface, and in plotting featureless névés on the autograph. The major problem in plotting proved to be the delineation of the margins of active glaciers where marginal zones were thickly covered with debris or fresh snow, or where it was necessary to define the boundary between the active glacier and stagnant ice. The distinction between active and stagnant ice is based on movement and nourishment, that is, on characteristics not directly visible in the air photographs, and the boundary is too often a matter of personal judgment. The authors hold that this boundary would be better omitted on an accurate map of the type discussed, while the glacierized area should be represented only in so far as ice is clearly indicated by surface features. A further provisional boundary might be given to indicate suspected buried ice. The paper emphasizes the importance of favorable glacier conditions when the control photographs are taken, to facilitate the mapping and interpretation of glaciological features.

The Pharusian belt of west-central Ahaggar belongs to the 'basement complex' underlying the Paleozoic and later sediments of the Sahara. This paper reports and discusses the Rb–Sr ages obtained on total rocks and minerals from two granitic stocks of the belt: the Tioueiine and Iskel intrusions.Both plutons gave good whole-rock isochrons, which show that the systems were closed 560 ± 40 m.y. ago with respect to Rb and Sr. This is, most probably, the age of crystallization. Three of the four values obtained on biotites are somewhat lower and scattered in the range 502–526 m.y. The discrepancies are probably due to deuteric reactions or incipient weathering. They can be ascribed neither to the loss of 87Sr during the cooling down of the granites, nor to rejuvenation by some later thermal or tectonic event.These studies confirm previous results of random sampling in Ahaggar and prove that large-scale igneous activity took place during the Early Cambrian Epoch. Knowing from field data that the Tioueiine and Iskel are late orogenic granites, it must be concluded that the Pharusian orogeny came to an end at that time.Such a result contradicts early assumptions, made in the field, of a middle Precambrian age for the Pharusian orogeny. It gives further weight to modern ideas concerning the 700–500 m.y. events in Africa, and it leaves time for erosion to create the Saharian platform before the deposition of the first Paleozoic sandstones.

Five glacier maps at scales of 1:5 000 and 1:10 000 were produced by the Photogrammetric Research Section of the National Research Council and the Axel Heiberg Island Expedition of McGill University for use in glaciological research in the Canadian Arctic. After general comments on the need for and scope of glacier mapping, the authors discuss in some detail the main problems encountered. It is maintained that glacier maps belong to the class of 'special maps' and that the specifications for them should be set by the glaciologists.Accuracy requirements, choice of mapping scale and contour interval, delineation of various glacier units, extent of detail plotting, etc. are critically reviewed, The 1:10 000 map of the entire White Glacier catchment area, accompanying this paper, is an example of a map which serves various glaciological purposes, primarily calculations of mass change. To facilitate future glacier mapping, the authors suggest that clear definitions of glaciological terms such as 'active glacier' or 'glacierized area' should be established and that their cartographical presentation should he further standardized.

In this paper evidence is presented in support of the hypothesis that the upper 2-3 km of oceanic layer II is a zone of chemical reaction between seawater and the oceanic crust as it moves away from the mid-ocean ridges.A model is constructed assuming that the principal alteration products resulting from the action of sea-water on primary basalts are:1. K-rich smectite formed during weathering of basalt,2. chlorite formed during retrograde metamorphism, and3. albite–actinolite formed during primary greenschist metamorphisms at the ridge crest.These three processes in combination could extract most of the stream input of K+, Mg2+, and Na+ and add SiO2, Ca2+, Fe2+, and Mn2+ to the ocean systems in amounts comparable to stream input.The steady state reaction of basalt with interstitial seawater to produce alteration minerals could exercise a strong influence in the chemistry of seawater and release energy in amounts sufficient to form a portion of normal heat flow measured on the ocean floor.

To make glacier mapping possible in white firn areas where stereo-effect is difficult to obtain, a large number of surface markers were placed on the glacier before air photographs were taken. Experiments proved that 3- to 5-kg powdered dye (yellow or brown ochre, or lamp black), packed in paper bags, made excellent surface markers when thrown from between 50- and 100-m elevation above the glacier surface. Color circles, applied by hand, also proved to be a good means for identifying ablation stakes, etc., in the firn area. An example of a map is given where the construction of contour lines was based upon the easily determinable dye markers that were clearly visible on vertical photographs taken from 7 300-m altitude.

The petrology of four plugs of fresh, coarse-grained olivine dolerite, of Pliocene age, is described in this paper. Two plugs, which exhibit textural and mineralogical variations, are described in detail. Major element analyses and selected trace element analyses for fifteen samples illustrate the chemical nature of the dolerite as well as fractionation in small marginal portions of the plugs. Strontium isotope values indicate that the plugs represent basaltic magma that was not contaminated by crastal matter. Both the mineralogy and the chemistry of the plugs indicate that the magma was mildly alkaline, and suggest that it was a differentiate of a primary olivine basalt magma, perhaps derived through crystal fractionation in a high-level magma chamber.

A paper-tape digital recording system is described which has been used to determine the isotopic abundance ratios of strontium from geologic samples. The system costs less than $10 000 and has proved to be highly reliable during its three years of operation. More than 600 analyses have been recorded and the results processed by an IBM-360 computer. This procedure has improved the precision of analyses from this laboratory by a factor of two. Over a period of 11 months, 16 measurements on the M.I.T. strontium carbonate standard gave a mean value for (87Sr/86Sr)n = 0.70797 ± 0.017%. The uncertainty En the results is the standard deviation of the analyses with the 86Sr/88Sr value normalized to 0.1194. Over shorter periods of time considerably better precision is indicated.

The Karakoram and Alaska–Yukon region between them account for perhaps 90% of the known surging glacier events. While modern research and information is available for the latter region, the Karakoram, though often referred to, remains virtually unknown except in a very general sense. The prime aim of this paper is to collate all the information that is available for the Karakoram from the usually old and inaccessible documents where it is found. It establishes eleven instances of surges with reasonable certainty and the probability of many more. The (rare) instances of detailed descriptions of the phenomena are quoted. A short discussion is given of the degree to which the information, and knowledge of the Karakoram environment, equate with various mechanisms put forward to explain surging glacier events.

Movements of the earth's crust causing progressive changes in the levels of large bodies of water relative to their shorelines may influence the formulation of water resource projects and/or their continuing effectiveness with time. In the Great Lakes basin there is evidence of an uplift of the earth's crust, of about 1 ft per 100 y, in the northeasterly part of the basin relative to that in the southwest. This results in a corresponding lowering of water levels along the northeasterly shorelines and a rise in water levels along the southwest shores. In at least two of the lakes, Lake Huron and Lake Ontario, the average depth of water will change with time. In Lake Huron, it will gradually decrease because the bed underlying the lake is rising with respect to the lake outlet. In Lake Ontario, the depth of water will increase since the lake outlet is rising with respect to the remainder of the lake. This paper reviews some of the engineering implications of the relative rates of crustal movement in the Great Lakes region on long-term management of the water levels of the Great Lakes.

In the Archean greenstone belt at Sioux Lookout, N.W. Ontario, a lowermost belt of volcanic rocks is unconformably overlain by sediments of the Abram Group. Our mapping has subdivided the Abram Group into three formations. The lowest (Ament Bay Formation) consists of interbedded conglomerates and sandstones. The sandstones contain large-scale cross-stratification, and the conglomerates and sandstones both lack graded bedding. The depositional environment was a subaerial alluvial fan—this is the first description of such a feature based upon modern sedimentological work in Archean rocks. The Daredevil Formation conformably overlies the Ament Bay Formation, and is composed of felsic and basic tuffs, and some interbedded turbidites. The uppermost (Little Vermilion) Formation is composed entirely of turbidites.The petrography of the sand, and large clasts, in the Ament Bay Formation indicates derivation from a dominantly granodioritic terrain. Some granodiorite boulders contain greenstone xenoliths, implying intrusion of the granodiorite after formation of the lowermost belt of volcanic rocks.In a final section of the paper, we define two Archean facies associations—a Resedimented association containing turbidites, pebbly mudstones, resedimented conglomerates, and basinal black argillites; and a Continental association, containing alluvial fan deposits, and possible coastal deposits from South Africa and Australia. The facies sequence in the Sioux Lookout belt is Continental followed by Resedimented facies, the reverse of the normal geosynclinal flysch (resedimented) → molasse (continental) sequence.

Seismic activity has been induced by loading and possibly lubrication of faults in rocks underlying several artificial lakes. Such evidence of failure justifies study of incremental stress distributions produced by the filling of artificial lakes. In this paper two-dimensional lakes are considered. Equations are derived giving the incremental stress components due to a side of a water-filled trough of polygonal section in the surface of art elastic half-space. A computer program based on these equations is described. Distributions of stress parameters are shown for lakes of rectangular and isosceles triangular sections, and for a two-dimensional approximation of a section of the lake forming behind the Bennett Dam on the Peace River, British Columbia.

This paper reports a parametric study of rainfall–runoff relations for 38 storms in the Eaton basin, southeastern Quebec, between 1950 and 1966. In addition to storm rainfall amounts, water table levels in the vicinity of the channel network, as indicated by baseflow prior to storms, appear to be very important in controlling the amount of response of the basin in different storms. Storm runoff is viewed as the product of direct interception by, and subsurface seepage into, expanded surface water systems in the valley floor areas of the basin. This is in agreement with the variable (partial) source area model developed over the last ten years by a number of hydrologists as an alternative to the Horton theory of runoff production.

Within the last few years studies of relationships among faulting, fault creep, and seismicity in active areas such as California and Nevada have progressed rapidly, and have contributed greatly to our understanding of tectonics and the earthquake mechanism. This success prompted a field and literature search for similar phenomena in New York State and adjoining areas, a region of only moderate seismicity but of sufficient population density so that the seismic hazard should be thoroughly studied using all relevant information.Evidence for postglacial bedrock faulting, dated by offset striations, is common on outcrops of a belt of Paleozoic shales and slates that extends from near Hyde Park, New York, northerly along the east side of the Hudson and Champlain valleys, and continues northeasterly into Quebec at least as far as St. Georges. Faults tend to be in the plane of slaty cleavage with the south or east side upthrown in postglacial time. The observed faults are thus high-angle reverse faults with little or no postglacial strike–slip component. Displacement along a single fault is usually of the order of an inch or less, but commonly several such faults are seen in an outcrop only a few feet across. Thus, the faults seem very numerous, and cumulative displacement across a belt tens of miles in width could be quite substantial.An important question is whether this faulting is associated with glacial loading or unloading, with tectonic stresses, or with some other effect such as thermal changes, hydration, or a chemical process in the shales. Present data do not seem adequate to resolve this point, and a major purpose of this paper is to request similar information on other areas, particularly those adjoining the region of interest here. Casual observation of such faults would probably be dismissed by a geologist as slumping, frost heaving, or some other local disturbance in most cases if he were unaware of the regional pattern.Correlation between the pattern of observed faults and that of recent seismic activity is not highly convincing, but this could be because of inadequacies in either or both sets of data, so this question also remains open.

The St. Lawrence valley system (including the St. Lawrence, Ottawa, and Champlain valleys, and the St. Lawrence or Cabot trough) is coextensive with a well-defined pattern of seismic activity. The valley system is in a region of general updoming, normal faulting, and alkaline igneous activity of a distinctive type. The main phase of tectonic activity probably dates back to Mesozoic time. The above and other evidence presented in this paper indicate the existence of a major rift valley system that may be called the St. Lawrence rift system.The Rough Creek – Kentucky River fault zone, and the normal fault zones in Texas and Oklahoma, and the Lake Superior fault zone probably represent extensions of the St. Lawrence rift system. However, current seismicity indicates that the present tectonic activity is along a straight zone running through lakes Ontario and Erie into the Mississippi embayment. The St. Lawrence rift system may also be connected with the mid-Atlantic rift, in the region of the Azores plateau.The rift hypothesis presented may be useful as a regional guide in the search for niobium-bearing alkaline complexes and diamond-bearing kimberlites.Crustal tension in the St. Lawrence region may be genetically related to the opening of the Atlantic basin as postulated in the hypothesis of continental drift.

The paper emphasizes that the choice of a proper procedure is essential for efficient glacier surveying. Terrestrial versus aerial photogrammetry and the use of electronic surveying procedures versus triangulation have been tested in surveys on the Athabasca and Saskatchewan glaciers, and on glaciers in northern Ellesmere Island, southeastern Alaska, and the Yukon Territory. The Otto Fiord glacier survey in northern Ellesmere Island demonstrates that no ground control is needed for volumetric glacier studies. Accurate maps needed for other studies depend on the establishment of control. Control can most efficiently be determined by tellurometer and phototheodolite with helicopter support, as shown in Alaskan glacier surveys. For large glaciers phototopography provides a good means of extending control from tellurometer traverse stations, as demonstrated in the Mount Kennedy survey. Simple one-color maps are an economical means of preserving survey results for future glaciological evaluation.

This paper describes the field relations of Tertiary basalts which are preserved as small patches intermittently along the coast for 90 km northwest from Cape Dyer, Baffin Island. The flat-lying, subaerial lavas generally rest directly on the Precambrian basement but in some localities a thin sequence of terrestrial sediments intervenes between the basement and the volcanics. Where the sediments occur, the overlying volcanics tend to be divisible into a lower unit of subaqueous volcanic breccia and an upper sequence of subaerial flows. In age, stratigraphic position and magma-type, these volcanics strongly resemble those of the basalt province of west Greenland. A model is presented for the generation of both provinces in a single volcanic episode, related to the opening of Labrador Sea – Baffin Bay by continental drift.

North-northwesterly striking Mackenzie diabase dikes of middle-Proterozoic (Helikian) age are profuse in the western part of the Canadian Shield. Published paleomagnetic data on dikes of this trend in Mackenzie District, on the Muskox Intrusion, the Coppermine River volcanic rocks, and the Sudbury dikes suggest that they are all products of closely related igneous events. This paper presents paleomagnetic data that suggest that the intrusion of extensive diabase sheets in the East Arm of Great Slave Lake, and of dikes as far to the northeast as Melville Peninsula and as far to the southeast as Manitoba, were also parts of these events. The mean paleomagnetic pole position for the Mackenzie dikes and for related intrusive and extrusive rocks is [Formula: see text], 171 °W with [Formula: see text]. Radioactive age determinations, some of which are unpublished, indicate an age of about 1200 m.y. for the formation of these rocks. It is suggested that for convenience all of these apparently related intrusive and extrusive igneous episodes be referred to as Mackenzie igneous events.

The sequence of the Labrador geosyncline is subdivided in three cycles, each beginning with deposition of shallow-water quartzites and precipitates and culminating with the deposition of thick shale–graywacke–basalt suites. This paper describes the stratigraphy and sedimentology of the formations deposited during the gradual re-stabilization of the basin at the end of cycle I.At the end of cycle I, red, green, and gray pro-deltaic shales and sandstones prograded into the basin from the west. They interfinger eastwards and upwards with the Dertaull Dolomite. In the west laminated dolomite was deposited on a deltaic platform; brecciated and conglomeratic dolomites developed at the slope margin, and grade into alternating laminated dolomite, conglomeratic dolomite, and pelite in the basin. Slumping and turbidity currents were important transport mechanisms. Lenses of massive dolomite deposited in relatively deep water occur in the center of the trough and a platform extended in the eastern, eugeosyclinal zone. Upper horizons of the Denault Dolomite grade into the Attikamagen IV basinwards. The basal member of the Attikamagen IV consists of relatively deep-water shales; these grade upwards into red silstone and fine-grained sandstones of deltaic or pro-deltaic origin. The Fleming Breccia overlies the Denault Dolomite at the western margin of the trough. This unit is probably derived from a bedded sequence of siltstone, sandstone, and dolomite, that has been profoundly altered by complete replacement of dolomite by chert, followed by pene-contemporaneous brecciation and slumping. The Wishart Formation overlaps all older units with a marginal unconformity, but has gradational contacts with the latest deposits of Cycle I (uppermost Attikamagen IV and perhaps Fleming) closer to the basin center.

The recent paper by Roberts and Mark (1970) illustrates most effectively the hazard of depending on a computer and a single field criterion to solve problems in glacial geology. The problem lies not in the computer technique for generalizing trends, but rather in the assumption that fabric analysis of till at a limited number of sites necessarily portrays faithfully a single, simple, and contemporaneous pattern of ice movement; this assumption is risky indeed in mountainous terrain. The hazard is, moreover, accentuated when field data provide only the local trend of ice movement, as the sense of the movement is also necessary to the trend surface analysis. The hazard is clearly illustrated in the example cited by Roberts and Mark (1970) from the eastern Fraser Valley of British Columbia (their Fig. 4 reproduced here as our Fig. 1). In this example till fabric studies have been restricted to deposits mapped by Armstrong (1960) as of Sumas age, a product of a short lived (perhaps 1000 years) glacial stade. Their outermost sites (e.g. Nos 9 and 14) may differ slightly in time of deposition from those nearer the source (e.g. Nos. 8 and 12) and some changes in the ice flow pattern during the period of deposition seem called for (Figs. 4 and 5). Even more important to the analysis is the basis for assuming sense of motion at their sites of fabric studies. Roberts and Mark evidently assumed (p. 1183) that the record was one left by "a valley glacier which flowed (southwards) from the side valley occupied by Stave Lake (the Hatzic-Stave Valley of Fig. 1) into the Fraser lowlands." The present authors, on the contrary, have evidence (see below) that the movement of the Sumas ice was northerly, rather than southerly, in the north

This paper presents theoretical and experimental studies of the propagation of Rayleigh waves along perturbed boundaries. In the theoretical treatment, the boundary conditions necessary for the propagation of Rayleigh waves are expressed in terms of the shape of the perturbed boundary. Then by applying a perturbation theory, and the Fourier Integral theorem, the perturbed parts of the solutions to the wave equation are obtained in the integral form. The perturbed contributions to the components of strain are obtained by the use of a numerical integration technique. The experiments are conducted on two dimensional ultrasonic models using plexiglass and plaster of paris as the modeling materials. The theoretical and experimental results for the perturbed half-space model and the model of a layer over a perturbed half-space, are in good agreement. In general, the results show an amplification of the strain amplitudes of Rayleigh waves along the Gaussian perturbation in the first model and along the free surface in the second model, in the direction of propagation.

This paper presents new radiometric data that permit some qualified statements to be made on the depositional history of the Belt sedimentary rocks. The period of deposition of sedimentary rocks of the Precambrian Belt Series has been placed within a broad time interval, for they rest on metamorphosed basement rock dated at ~ 1800 m.y. and are overlain by the Middle Cambrian Flathead Quartzite (circa 530 m.y.). Prior geochronometric data gathered during the last decade indicate most of the Belt Series to be older than ~ 1100 m.y.K–Ar and Rb–Sr techniques have been applied recently to a variety of samples selected from the whole gamut of the Belt Series. Glauconite from various formations in the sequence McNamara Formation down to the uppermost beds of the Empire Formation in the Sun River area has been dated at 1080 ± 27 m.y. by the K–Ar method and at 1095 ± 22 m.y. by the Rb–Sr mineral isochron method. A Rb–Sr whole-rock isochron based on argillaceous sedimentary rocks from this 5000-ft section gives an age of 1100 ± 53 m.y. The concordance of the preceding results and the K–Ar ages (1075 to 1110 m.y.) on Purcell sills and lava imply that this age represents the time of sedimentation of these units.A Rb–Sr isochron based on whole-rock samples stratigraphically far below the Umpire Formation— the Greyson Shale, Newland Limestone, Chamberlain Shale, and Neihart Quartzite in the Big Belt and Little Beit Mountains—yields an age of 1325 ± 15 m.y. This result is interpreted as indicating a substantial unconformity beneath the Belt Series, at least in central Montana; it also suggests a major hiatus, unsuspected from field evidence, between the uppermost part of the Empire Formation and the Greyson Shale.The results for the youngest of Belt rocks—the Pilcher Quartzite and the Garnet Range Formation, which are exposed in the Alberton region—are equivocal in that there is widespread dispersion. A large component of detrital muscovite in some of the samples could readily account for the magnitude and sense of this dispersion. A maximum age of ~930 m.y. based on an isochron of minimum slope through the various points may be inferred for this sequence. A K–Ar age of 760 m.y. obtained on biotite from a sill in the Garnet Range Formation provides a minimum age for these younger Belt rocks.Three distinct periods of sedimentation for Belt rocks sampled are suggested at ≥ 1300, 1100, and ≤ 900 m.y., with two substantial hiatuses of 200 m.y. or more. In addition the data for the sequence in the Big and Little Belt Mountains suggest that sedimentation may not have commenced for a period of possibly 400 m.y. after the metamorphism that affected basement rocks, while the data for the Garnet Range and Pilcher sequence suggest that sedimentation ceased some 200 to 400 m.y. prior to the deposition of the Middle Cambrian Flathead Quartzite.To suggest that the Belt sediments were deposited continuously over a period of 400 m.y. or more would imply an unusually low average rate of deposition of ≤ 0.1 ft/1000 yr, and this for the thickest part of the Belt Series. As a realistic expression of the depositional history of the Belt Series, both viewpoints are open to question, but the viewpoint that the Belt basin has been characterized by discontinuous sedimentation would be more in keeping with the principle of uniformity.

The assumptions on which the so-called magneto-telluric method to determine the subsurface conductivity of the earth is based are examined and it is shown how the method can be revised to get rid of those assumptions which are not necessarily legitimate. The principle of this revised or generalized magnetotelluric method is that the magnetic and telluric field components which observation can provide over the entire surface of the earth are more than sufficient viewed as boundary conditions to determine the electromagnetic field inside the earth with a prescribed conductivity distibution and, therefore, the extra boundary condlt~ons can be consistent with each other only by the correcrly prescribed (or chosen) distribution of electrical conductivity. The purcly magnetic method to determine the conductivity, which relies on the assumption that the magnetic field in space above the surface of the earth, is a potential held, is also revised to free it of the assumption which does not hold true unconditionally. Up to now, two methods have been proposed which make use of natural geomagnetic and telluric variations to determine the electrical conductivity of the earth. One is the method developed by Chapman and Price (1930), Lahiri and Price (1939), and Rikitake (1950, 1951). It may be called the "potential theory" method, since it is based on the assumption that the magnetic field in the space above the earth's surface and below the ionosphere can be derived from a potential function. The other method is the so-called "magneto-telluric" method, the basic ideas of which were given by Kato and Kikuchi (1950) and Kato and Yokoto (1953) and which was embodied mathematically by Cagniard (1953). The natural geomagnetic and telluric variations used by both methods as inducing electromagnetic fields are geomagnetic storms (ssc, Dst, and SD), solar and lunar daily variations (Sq and Sl), bays, solar flare effects (sfe), and geomagnetic pulsations. The "potential theory" method, which is a purely magnetic method in contrast to the magneto-telluric method, has a sound mathematical foundation, insofar as the assumption holds true that the magnetic field above the earth's surface has a potential. The mathematical procedure for determining the electrical conductivity of the earth is reasonably concise, though it is more complicated than that given by the "magneto-telluric" method. However, the method is not unconditionally applicable to every case, since the basic assumption of the "potential theory" method does not always hold true as has been discussed by Nishida (1962,1964) and also implied in a paper by Dungey (1962). On the other hand, the "magneto-telluric" method involves an even stronger assumption about inducing fields in the space above the surface of the earth, viz. that it is uniform in space. This assumption with two other subsidiary assumptions that the earth's surface is an infinitely wide plane and that the

Seismic experiments have been undertaken along the Atlantic coast of Nova Scotia, and an attempt has been made to determine by what mechanism the compressional wave which is recorded as the first event in the range of distance 10 km to 180 km propagates, and to describe its attenuation. In this part of the paper the change in amplitude of the first half-cycle of the first event is investigated, and compared with the change in amplitude which might be expected if propagation occurred as a "head wave", and if propagation occurred because of the presence of a velocity gradient in the upper few kilometers of the earth's crust. We find that we cannot distinguish between the two mechanisms of propagation with any certainty, and although the suggestion is made that the value of Q is in the range 90 to 300, depending upon the propagation mechanism, the assumptions which underlie the approach are criticized, and a more reasonable one put forward.

In a previous paper (Hermance and Peltier 1970), integral expressions for the magnetotelluric fields of a line source over a stratified conductor were obtained and numerically evaluated for a sequence of simple conductivity structures. This calculation was intended to simulate the magnetotelluric 'source effect' which is anticipated at auroral and equatorial latitudes. The most serious flaw in this line source model of an electrojet is that it does not take into account the laterally diffuse nature of the real current distribution. By assuming that the current density in the electrojet has a Gaussian dependence upon the horizontal coordinate a more realistic source model can be constructed. Representative solutions to the induction problem employing this source are analyzed in an effort to obtain a more accurate measure of the effect of finite source geometry on magnetotelluric interpretations in auroral and equatorial regions where strong electrojets exist at E-layer altitudes. In tectonically active areas such as Iceland (which is under the auroral electrojet), it appears that Cagniard's assumption of a "plane-wave" source leads to a correct interpretation of the subsurface conductivity structure in the commonly employed U.L.F. frequency band (10−4 Hz–1 Hz). A relationship, Tozer (1969), is here assumed to exist between tectonism, anomalously high near surface temperatures, and corresponding increases in electrical conductivity. In tectonically stable shield areas, however, the effect of finite source geometry is more pronounced and could lead to significant errors in interpretation.

The electrically heated cylindrical probe has often been used to measure the thermal conductivity of materials which allow the contact layer to be small enough to have negligible thermal resistance and negligible thermal mass. The probe method is not widely used in boreholes, mainly because the increased complexity of the theory required by the boundary conditions encountered in typical field situations makes it difficult to design appropriate probes and to interpret the data.This paper deals with the results of a comprehensive series of laboratory and field experiments, using cased and uncased boreholes, to investigate the importance of various design parameters and to compare the relative merits of the many proposed methods of reducing the data.It has been found that there is a surprising degree of latitude in probe design provided an uncertainty of 10% in conductivity values can be tolerated.

Diagnoses and illustrations of the holotypes and paratypes are given for two new genera and seven new species of the mammalian orders Rodentia and Lagomorpha from the Upper Miocene Wood Mountain Formation of southern Saskatchewan. Taxa named include the eomyid Adjidaumo russelli, sp. nov.; the heteromyids Perognathus saskatchewanensis, perognathoides kleinfelderi, and Peridiomys borealis, spp. nov.; the entoptychine geomyid Lignimus montis, gen. et sp. nov.; and the ochotonids Hesperolagomys fluviatilis, sp. nov., and Russellagus vonhofi, gen. et sp. nov. All taxa treated in this paper are from the Kleinfelder Farm locality, near Rockglen, Saskatchewan. More detailed descriptions and comparisons will be given in a subsequent publication.

This paper describes an aeromagnetic profile from Prince Edward Island, through the Cabot Strait to the Tail of the Grand Banks of Newfoundland, and subsequently over the Flemish Cap. It is inferred that Burgeo Bank off the southwest coast of Newfoundland is possibly a granite intrusion of Devonian age. A distinct magnetic anomaly, approximately 400 gammas in amplitude, appears to be associated with the edge of the continental shelf at the Tail of the Bank. A series of sharp shallow-source magnetic anomalies was recorded over the Flemish Cap, and this feature appears to have a negatively polarized core whose long dimension is oriented in a NNW.-SSE. direction.