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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).

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

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.

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 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.

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.

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 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.

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 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 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 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.

With the advent of crystal settling in a solidifying igneous intrusion, the roof contact of the intrusion may be continuously subjected to temperatures approaching those of the magma itself. This causes steeper temperature gradients in the roof rocks and, consequently, more rapid heat loss and solidification than would occur if the crystals were frozen to the roof. By contrast, the accumulation of crystals in the lower parts of the intrusion acts to lower the floor contact temperature and so reduces temperature gradients in the floor rocks; but since the proportion of liquid near the floor is reduced, the overall effect also is to speed solidification, specifically in this case, from the floor upwards. The present paper reviews in a qualitative way the relation between crystallization mechanisms and temperature in a magma body when crystal fractionation is a major process. It then examines quantitatively, by means of one-dimensional solutions of the heat flow equation, the influence on crystal accumulation rates and roof rock temperatures of (a) variations in magma temperature, (b) pre-intrusion temperature gradients in the roof rocks, (c) shallow emplacement, (d) formation of an upper border zone or floating of crystals, and (e) latent heat effects associated with contact metamorphism. Finally, it considers the effects of heat loss to the floor rocks on (i) crystallization in the magma above the accumulating pile of crystals, (ii) solidification of trapped pore magma, and (iii) contact metamorphism of the floor rocks. Some of the more important equations presented also apply to sills, sheets, and dikes showing no crystal fractionation.

Nine glaciers in Glacier Bay, in southeastern Alaska, and three others within a radius of 60 km have been known to surge in the last 60 years. Of these, seven have surged during the 1960's. The surges of three of them, the Tyeen, Rendu, and Carroll, are discussed in this paper. Each glacier has surged one or more times previously. The course of each surge has been documented by photography but there has been no study of the regimes of these glaciers. The distribution in time and space of these and other surges in the Glacier Bay area are discussed and it is suggested that there may be external factors which cause more surges during some periods than others. These relationships need to be correlated and analyzed. A program of future observations is suggested.

About 5 000 ft of Carboniferous sedimentary strata occur in the Cape Rouge and Conche peninsulas, small projections on the east side of the Great Northern Peninsula of Newfoundland. The lower 900 ft of the section consists of coarse conglomerate and sandstone, the fragments in which were derived from nearby older rocks. These lower beds are overlain by about 4 000 ft of shale and sandstone, in places petroliferous and with bituminous residues, and bearing plants and spores identified as of upper Horton (late Tournaisian) age. The sedimentary rocks described in this paper are the northernmost known Carboniferous rocks of the Appalachian belt. They lie in a basin between Groais Island and the Great Northern Peninsula and may possibly be continuous under the sea with the Grand Lake–White Bay basin a 100 mi to the southwest. The boundary fault on the west side of this Carboniferous basin is a portion of a fault system which is known to extend some 300 mi from the northern tip of Newfoundland to its southwest corner and is a portion of the Cabot fault of Wilson. Movement on the fault system appears to have been of at least three ages, pre-Horton (pre-Tournaisian), post-Horton–pre-Windsor (post-Tournaisian–pre-Visean), and post-early Pennsylvanian (post-Westphalian "A").

This paper pursues the study of an apparent correlation between lead isotope abundance characteristics and features of the deposits in which the lead is discovered. New and precise analyses have been carried out on 55 galena samples, mostly From Australasian ore deposits classified as stratiform. To help clarify the interpretation, certain vein leads related to those which are stratiform have been included, as has one analysis of volcanic cotunnite.New evidence is offered that all leads began their isotopic evolution in a unique primary system which has very restricted spatial variation in the ratios U/Pb and Th/Pb. Leads from certain stratiform deposits approach more closely in isotopic composition the products of the primary system than do vein leads, many of which involve extensive crustal histories thai further modify the isotope ratios. The analyses presented here have sufficient precision to permit a close examination of the differences in isotope ratios between stratiform leads and the products of a simplified model for the primary system. The differences are significant and important.Novel aspects of the experimental technique are discussed.

ARMSTRONG, J. E. 1960. Surficial geology of the Sumas MATHEWS, W. H. 1967. Profiles of late Pleistocene Map-area British Columbia. Geol. Surv. Can. glaciers in New Zealand. New Zealand J. Geol. Paper 59-9. Geop. 10, pp. 146-163. FYLES, J. G. 1963. Surficial geology of Horne Lake ROBERTS, M. C. and MARK, D. M. 1970. The use of and Parksville Map-areas, Vancouver Island, trend surfaces in till fabric analyses. Can. J. Earth British Columbia. Geol. Sum. Can. Mem. 318. Sci. 7, pp. 1179-1 184.