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By P. V. Amosov, V. A. Masloboev, D. V. Makarov, S. G. Seleznev, A. A. Baklanov

"The development of industry and intensive use of natural resources leads to a significant decrease in the share of reserves of rich ores, deposits of which have nearly all been exploited. Large amounts of displaced rock mass are accumulated, significant emissions of gas and dust from mining, dust from dumps and tailing pits, ingress of chemicals and toxic elements in surface and groundwater all can have negative effects on existing ecosystems and human health. Especially dangerous is the impact in Arctic regions with extreme climate conditions. The maintenance of overburden dumps and tailings dams requires significant capital and material costs. In this paper, some mining enterprises of the Murmansk region, in the Russian Federation, consider the environmental problems of the industry and propose some solutions.INTRODUCTIONThe safety of environment during the extraction and processing of minerals is a very acute problem throughout the whole world. The problem acquires a specific character in the Russian Federation. There, rather poor minerals, often existing in unconventional forms and including several mineral components are processed. The Russian mineral base has a specific geographical location; most of the deposits under operation are located in the Subarctic or Arctic regions, as well as in Siberia and in the Far East. Vast amounts of rock waste and tailings pose serious economic and ecological problems in mining regions. The operation of overburden heaps and tailings requires considerable capital and material costs. The dumps withdraw vast lands from potential commercial use. Large amounts of mined rock disturb the existing geological balance; emissions of gas and dust which accompany the mining operations, dusting of waste heaps and tailings, emissions of reagents and heavy metals into natural surface and ground waters all can produce negative effects on existing ecosystems and human health."

Jan 1, 2016

By Kris Inwood

"In 1879, when the Dominion government initiated its controversial program of industrial promotion, iron smelting in Canada was limited to one company producing coke iron on the mainland of Nova Scotia and three small charcoal blast furnaces in Quebec. There was no steel production. By the eve of the First World War, iron and steel were being produced in very large quantities, the companies active in 1879 had disappeared and new centres of integrated iron and rolled steel production at Hamilton, Sydney and Sault Ste. Marie had come to resemble the industry as we know it today. The most dramatic change was that at Sydney, Nova Scotia, where in the early 1900s, two steelmaking companies established works. The Sydney developments have been explained as the result of resource discovery and technical change. W.J. Donald, in his authoritative account of the Canadian iron and steel industry, observes:(1) ""The most rapid growth of the Canadian iron and steel industry has occurred since 1897 ... The remarkable growth has been caused largely by the new conditions of the industry. The discovery and use of Newfoundland ores, together with the availability of Cape Breton coal, has made the Nova Scotia industry not only possible but profitable .... It is a safe conclusion that the Canadian industry would not have been an important one, had it not been for the discovery of the Michipicoten and especially the Wabana (Newfoundland) ores:' Donald also argues that metallurgical progress had been necessary to render the ores valuable. ""Newfoundland ores ... contain a considerable amount of phosphorus, and were made available for steel-making by recent inventions:' The purpose of this paper is to re-examine Donald's story. It will be argued that the origin of steel-making at Sydney is somewhat more complicated than Donald has indicated. The difficulty with Newfoundland ore extended beyond its phosphorus content and a resolution required more than the basic open hearth furnace identified by Donald. Moreover metallurgical change was only one of several developments necessary to induce industrial investment at Sydney. Surprisingly, however, the discovery of iron ore in the late nineteenth century does not appear to be part of the explanation."

Jan 1, 1999

By T. Takayama Filho

Votorantim Metais Zinco is a smelting facility which produces SHG zinc, zinc alloys, sulfuric acid, liquid SO2, copper sulfate, cadmium metal and silver concentrate. It is located at Juiz de Fora, Minas Gerais State, Brazil. This facility has been operating since 1980 and its current capacity is 95,000 tonnes of zinc per year, using mostly imported sulfide concentrates.The plant uses the conventional roast-leach electrowinning (RLE) process, in which iron is removed from the circuit as jarosite. The residues generated by the RLE process, which amount to about 200 t/day (dry weight), were until 10 years ago, deposited in tailing ponds having no impervious lining. More recently, jarosite and other wastes have been deposited in a properly built reservoir, but this is reaching its maximum capacity. In order to decommission these disposal operations and to reclaim the sites in an environmentally acceptable manner, Votorantim Metais concluded in 2004 a rehabilitation project for the old tailings pond and prepared detailed plans for managing the current and future disposal of jarosite-bearing residues. This paper describes the procedure for removing iron from the hydrometallurgical circuit and discusses the past and current status of the residue disposal sites, as well as the future challenges related to the environmentally acceptable handling of iron residues.

Jan 1, 2006

By S. Ng, Peter Stapleton, Paul Mankowski, J. Spence, R. Siy

"Syncrude has developed a low energy extraction process for the recovery of bitumen from oil sand. This new process operates at a temperature of 25 °C, resulting in substantially lower energy costs and lower capital costs, especially for the thermal energy generation equipment. The process will be used in Syncrude’s Aurora Mine, which is scheduled for startup in mid 2000. The flowsheet for Low Energy Extraction includes hydraulic transport of oil sand slurry, and bitumen separation using collector and frother chemicals and air as process aids. A number of flow sheet innovations and optimizations have been included, resulting in the next generation of extraction technology. Experimental pilot plant results, engineering progress to date and areas of ongoing work will be discussed. SUMMARYThe Low Energy Extraction Process has been successfully developed for commercial implementation at Aurora. The 1996 100 tonne hour Field Pilot demonstrated that the bitumen recovery target could be met with an 11.1% grade oil sand. However, pilot plant bitumen recoveries for a lower grade oil sand were not acceptable. The subsequent flowsheet optimization study led to a new flowsheet for Low Energy Extraction, which includes a primary separation vessel, a flotation circuit for PSV middlings, and the use of middlings displacement in the PSV cone bottom with flotation underflow. A test program conducted in 1997 showed that the new flowsheet could significantly improve the bitumen recoveries for lower grade oil sands. Engineering work on process scale-up led to selection of a 30 meter diameter PSV, with a tangential feedwell. The successful development and commercialization of Low Energy Extraction for the Aurora Mine Project is a major enabling step in the Syncrude 21 program. The low energy requirements of this process allow Syncrude to develop the Aurora leases more cost effectively. The use of this process results in major capital cost savings, predominantly in the thermal energy infrastructure and also provides long term operating cost advantages for Syncrude."

Jan 1, 1999

By C. A. Hardie, G. F. Leichtle, J. A. Finch, J. A. Watson

"The recycling of wastepaper has become an important and common process worldwide. Techniques similar to those used in the mineral processing industry are used to produce high quality recycled fibres for use in newsprint. The mineral processing group at McGill University, in conjunction with the Pulp and Paper industry (Mechanical and Chemi-mechanical Wood Pulp Network), has adapted one of these techniques, column flotation, for the purpose of deinking wastepaper. This article describes the typical process of recycling wastepaper from a mineral processing point of view. It also presents results from McGill University’s flotation column test work at a Québec wastepaper recycling facility. IntroductionThe recycling of wastepaper has become an important and common process worldwide, including Canada which is now the world’s largest importer of wastepaper (CPPA, 1996). Much of the current drive to increase the utilization rate of recovered paper is a reaction to the solid-waste disposal problem that faces many Canadian and United States municipalities. The real problem in the disposal of solid waste is not the absolute amount of garbage that must be disposed of each year, but this amount in relation to available disposal capacity.Environmental restrictions on the creation of new landfill sites and incinerators (the two main options for disposal of municipal solid waste) have tightened the demand/supply balance in the solid waste disposal market. This shrinking availability of waste disposal sites in the face of increasing population with greater disposal requirements defines the Developed World’s solid waste crisis. Not only are there fewer disposal sites available, but the costs of using them is skyrocketing. These factors have increased government regulations mandating recycled paper content in newsprint. Conservation and environmental issues make the current drive for wastepaper recycling a real issue and business opportunity."

Jan 1, 1999

By V. Thangadurai

The critical problems in commercialization of the present solid oxide fuel cells (SOFCs) and useful electrical and physical properties of IT-SOFCs electrolytes are discussed briefly. The conductivity behavior of the perovskite-type and perovskite-related structure metal oxides are summarized. Perovskite-type La0.9Sr0.10ao.8Mgo.203_8 (LSGM) exhibits high ionic conductivity of 0.1 S/cm at 800 °C. In order to improve the electrical conductivity of LSGM and the In analogue of LSGM, substitutions have been made at the A-and B-sites. Substitution of trivalent La3+ by isovalent Pr3+ in LSGM and La09Sro ilno.sMgo.202.85 (LSIM), yield new mixed conductors. Among the investigated compounds in the present study, La0APro.4Sro.21no sMgo.2028 exhibits the highest total electrical conductivity of 3.2 x 10-5 S/cm at 200 °C in air with the lowest activation energy of 0.44 eV (200-700 °C). LSIM and Pr-substituted LSGM and LSIM perovskites show p-type electronic conductivity in the oxygen partial pressure range 10-5 ? 0.21 atm at 750 °C. The perovskite-type solid solution SrSn1-xFex03 exhibits compositionally driven phase transitions. For example, compound of the composition x = 0 to 0.3 crystallizes in an orthorhombic GdFeO3-like perovskite structure, where as that of x = 0.4-0.9 crystallizes in simple cubic SrTiO3-like, and that of x = 1 in orthorhombic structure. The electrical conductivity of SrSn1_xFex03 increases with the increasing Fe content and reaches a value of about 10-1 S/cm at 25 °C in air for x = 1. Compounds with low Fe content exhibit both ionic and electronic conductivity, while the higher Fe content 0.5) perovskites are electronic conductors over a wide range of oxygen partial pressure of 10-22? 0.21 atm at 750 °C.

Jan 1, 2005

By J. E. Dutrizac, Alba Sunyer

The factors affecting the precipitation of arsenic-free alunite (KAl3(SO4)2(OH)6) were investigated in a series of laboratory experiments. Although the amount of alunite precipitated increased with increasing retention time, temperature, solution pH and the concentrations of Al(SO4)1.5 or K2SO4, the composition of the products remained nearly constant. The preferred conditions identified for the precipitation of arsenic-free alunite were then used to assess the behaviour As(III) and As(V) during alunite precipitation at 98°C. Increasing additions of As(III), as NaAsO2 or As2O3, resulted in a slight increase in the amount of precipitate formed at pH 2.80. However, X-ray diffraction analysis showed all the precipitates to be alunite, and <0.2% As(III) was detected in the products. In contrast, increasing additions of As(V), as KH2AsO4 or As2O5, resulted in significant increases in the amount of precipitate formed at pH 2.80 or 3.00. Furthermore, the arsenate (AsO43-) contents of the precipitates increased up to 15%, and the sulphate contents decreased, as the As(V) concentration of the synthesis solution increased from 0 to 9 g/L. X-ray diffraction analysis of the products detected only alunite, but there was a progressive expansion of the alunite cell with increasing arsenate content. The implication is that arsenate substitutes for sulphate in the alunite structure. Preliminary observations on the environmental stability of the arsenate-bearing alunite using the TCLP protocol gave solubilities <0.4 mg/L from a precipitate containing 8.5% AsO4 and 7.8 mg/L from a product containing 19.5% AsO4. Thus, it appears that alunites containing less than -10% AsO4 would be an acceptable vehicle for the disposal of arsenic from hydrometallurgical processing solutions.

Jan 1, 2011

By L. Bryson, J. H. W. M. Brits, K. Voogt

"The Anglo American Platinum’s Rustenburg Base Metals Refinery (RBMR) has the world’s first full deposit nickel plating tankhouse. Impurities in the nickel electrolyte can induce stresses in the electrowon nickel deposits that could lead to delamination of the deposit. Identifying the impurities that contribute to increasing internal stresses in the nickel deposit is key to successful operation and automation of the tankhouse. Impurities were introduced in the plant electrolyte and the effects on the full-scale nickel deposits evaluated. The impurity-adjusted electrolyte solutions were also analyzed using commercially available bench-scale methods to determine the induced stress. A correlation between impurity-induced deposit stress and full-scale delamination was developed. A direct correlation can now be made between feed quality, i.e. impurity concentrations, and degree of delamination in the plant. This methodology has the potential to rapidly predict the effect of new reagents, upstream process upset conditions and synergistic interactions between impurities on deposit stress and delamination of nickel deposits.INTRODUCTION Nickel electrowinning in sulphate media was first pioneered by Outokumpu in its Harjavalta refinery in 1960 (Saarinen and Seilo, 1985). The original process was very manual with starter sheets plated onto “acid resistant” steel for 36 hours and then manually stripped and cut into sheets which could be inserted into the main production cells for a further 4–5 days. The starter sheet stripping and manufacture process was later automated. The same technology was subsequently implemented on a number of plants around the world. Anglo American Platinum’s Base Metal Refinery (BMR) began nickel electrowinning in the early 1980’s. The recent expansion of Anglo American Platinum’s Base Metals Refinery necessitated the construction of a new nickel tankhouse to achieve two primary objectives. The first to increase the capacity to 32 400 tpa nickel and the second to reduce employee occupational exposure to nickel aerosols. The new tankhouse has been commissioned and is in the process of ramp-up; more details are given by Hagemann et al. (2016). Fundamental to lowering employee exposure to aerosols was automating both harvesting and final handling of cathode. In order to accomplish this a bold move was taken to plate up to 10 days on permanent titanium blanks which are harvested by automatic crane and automatically stripped. The original development work for the plating nickel on titanium blanks over a ten day cycle is given by Bryson et al. (2006)."

Jan 1, 2017

By A. S. Dawson

Introduction The purpose of this paper is to discuss, in a general way, the application of geological principles in the exploration for, and development of, deposits of industrial minerals. Mention of geological factors pertaining co specific minerals will be by way of illustration only. Since many prospectors are little acquainted with the geological setting and mode of occurrence of deposits of these minerals, some prospecting possibilities in the field will be pointed out. Geology is a tried and proven tool in the search for and exploitation of metalliferous deposits and of oil and gas fields, but, so far at least as Canada is concerned, only very rarely has a directed, intensive search been made for deposits of industrial minerals. Examples might be cited, however, where, in other countries, such investigations have yielded rich rewards. Thus, development of the vitally important potash deposits of New Mexico was the result of a deliberately planned programme of geological investigation, first by United States Government agencies, and later by private interests. War or the threat of war, or peace-time industrial expansion, can render concentrated exploration for specific minerals desirable or even essential. Such exploration is, primarily, a geological problem. Admittedly, there is in general less scope for the application of geology in the search for, and development of, deposits of industrial minerals than of metalliferous minerals, oil, etc. Where the latter are concerned; the objective of exploration is to find a material that is valuable, within broad limits, no matter where it is located or how it occurs. The unit value of the material is limited only by the amount of the valuable constituent in the formation- its possible upper limit is tremendously high. On the other hand, many industrial minerals constitute in themselves 90 per cent or more of the formation- their amount cannot increase and their unit value is commonly low. Moreover, for commercial exploitation, the deposit must, in general, be reasonably close to markets or to plant or other facilities for processing the raw material, since, owing to its low value, this cannot be transported any great distance. As a consequence, intensive geological search for and investigation of such deposits has been restricted to industrialized areas. Obviously, however, it is good insurance for any operator to understand the geological background of his deposit, particularly in the case of new developments.

Jan 1, 1949

By J. W. Hohn

The precipitation of Fe(III) to form ferrihydrite in the presence of arsenic is the United States EPA&apos;s Best Demonstrated Available Technology for treating arsenic-containing hydrometallurgical solutions and waste streams. This technology has been widely adopted throughout the world and developments have been well reviewed. The adsorption and long-term stability of ferrihydrite can be improved by co-precipitating Fe(III) and Al(III) together to form an aluminum-modified ferrihydrite. Arsenate adsorption into ferrihydrite and modified ferrihydrite as a function of pH, Fe/As or (Al+Fe)/As mole ratio, and the initial As(V) concentration is presented and compared. The results of long-term aging of both adsorbents at 70°C for over a year are also summarized.

Jan 1, 2006

By N. Musee, N. Kornelius

This study presents a neural network approach to modelling the liberation of gold bearing ores. A complete mineralogical analysis of unmilled and milled ores, including gold deportment and gangue content are used as inputs to a self-organising neural net which generates order preserving topological maps. The arrangement and shapes of these clusters are coupled to unmilled free gold data to predict gold liberation in milled ores (absolute error: 4.2%). Moreover, the self-organising maps were diagnostic of the quality of data used, indicating that the relationship between particle size and gangue material content requires further investigation.

Jan 1, 2005

By E. B. Wilson

"Although the Operations Research technique of Reliability Theory has been applied with marked success in many fields, including the Apollo spaceship programs, the concept of reliability has not been generally adopted in mining and other heavy industries. Of course, reliability, or the probability that a system will be able to operate without a failure for a given interval of time, does not require the same emphasis in mining as in the aerospace industries. Nevertheless, certain aspects of Reliability Theory can be followed advantageously. For example, reliability calculations can determine the best time to overhaul and whether to retain stand-by units.The usefulness of the pseudo-operations research technique known as Replacement Theory is more readily re-cognized by the maintenance engineers in mining and other heavy industries. One of the least complex models enables the optimum Lifetime of an asset to be determined."

Jan 1, 1970

By Fr. -W. Bach

In the past years the enormous weight saving potential of magnesium sheet has been demonstrated by various research projects all over the world. It has been shown magnesium flat products can benefit automotive, aviation, machine tool and consumer electronics industries. Major material problems such as poor formability, corrosion resistance and high production cost still inhibit the application of magnesium sheets in large scale production. The present contribution outlines achievements in casting and rolling technology. The authors developed an adapted strip casting process in which near-net-shape rolling feedstock of several wrought alloys has been produced. During the rolling process, various parameters were varied in order to modify the microstructure and surface quality of sheet. Several temperature cycles, strains, lubricants, roll surface structures and roll coatings have been analyzed. The sheets were examined and tested in deep-drawing experiments. Suitable rolling schedules have been developed for standard and modified wrought alloys. The study concludes with an overview of current industrial solutions and an estimation of the potential cost savings that might result from the adaptation of the process that has been developed.

Jan 1, 2006

By Michael Zurowski

This paper traces the history of International Mogul's assessment program on the Lake Ainslie barite-fluorite deposits of Cape Breton Island. The geology of the area is outlined, and the main vein systems described. The geophysical and geochemical exploration techniques employed are explained, the metallurgy of the ore is covered, and the market prices and economics of operation are described.

Jan 1, 1972

By R. L. Dunsmore

Introduction If one had been called upon to describe petroleum oil refining seventy-five years ago, he could have acceded to the request quite satisfactorily in about fifteen minutes. Fifteen years ago, an hour and a half would have been sufficient to give a general idea of oil refining, and of the equipment used for this purpose. Today, so extensive has been the research into all phases of the refining and manufacturing of petroleum products, and so rapid the strides in improvement in technique and equipment, that I doubt if a week would suffice to give an adequate outline of ail the ramifications of present-day oil refining. I propose to only &apos;hit the high spots&apos;, dealing particularly with the equipment and methods employed at the Imperoyal refinery, which you are to visit. Crude oil, the refiner&apos;s raw material, contains essentially only two elements, hydrogen and carbon. These are not present in the free state but are combined in various proportions as &apos;hydrocarbons&apos;. A given crude oil is not made up of just one hydrocarbon, but of myriads; some solid, others liquid, and still others gaseous at atmospheric temperature and pressure, ail dissolved one in the other. Moreover, the nature and the relative amounts of the several hydrocarbons vary very considerably in crude oils from different sources. That is, a &apos;crude&apos; from Oklahoma will contain hydrocarbons not present in crude from Mexico, and is different again from the Venezuela crude. Not only this but oil in a certain well in, say, Peru may be differently constituted from that in a well half a mile distant from it.

Jan 1, 1931

"Mining with blast holes drilled upwards may be done to recover sill pillars, or for economic reasons when the distance between the levels is relatively large. If the rock is sufficiently competent to accommodate large stope size, the distance between sublevels could be increased to as much as drilling accuracy allows. The same drill drift can be used for the drilling of both down holes and up holes. In the case of down holes, the initial opening of the stope (drop raise) is not as much a problem as for the inverse drop raise for mining with up holes. This is because, with a drop raise, a lot of space is available at the toe for the blasted rock to expand. In addition, the raise can be blasted in many shots, thus allowing smaller blasts each time. Inverse drop raises are generally much more difficult to blast because of the limited space for muck flow, and must, therefore, be taken down in a single blast, requiring special considerations in order to ensure a success. A case study of a 29 m (95 ft) inverse drop raise successfully blasted in a single shot at Heath Steele Mines is described. The paper covers technical considerations such as drilling accuracy, hole deviation survey, delay extension and protection, initiation methods and initiation sequence. Finally, a novel method for creating the initial opening called ’slot drilling’ is presented. This method, inspired from LKAB in Sweden, consists of drilling a row of interconnected holes using a special guide mounted on a regular production drill hammer.With a case study of blasting an inverse drop raise of 29 m (95 ft) in one blast, this paper further discusses some technical issues that are critical for the development of inverse drop raises. A novel method for creating the initial opening with a slot of interconnected holes is also presented with the experience acquired at different mine sites across the Noranda group."

Jan 1, 2000

By G. T. Lapidus, R. Zárate-Gutiérrez

Selective leaching of lead from a Pb-Ag-Zn concentrate with hydrogen peroxide in citrate solutions was studied at room temperature. Leaching tests were performed, varying the H2O2 concentration and the solid-liquid ratio, holding the solution pH constant at 7, and the citrate concentration at 1 M. Lead extractions of 100 % were achieved with 4 and 5 times the stoichiometric quantity needed to form elemental sulfur, with only a small amount of metal impurities dissolved (Ag, Zn and Fe). The lead solubility limit at those conditions was found to be ~21 g L-1. X-ray diffraction analyses of the leach residues were free of galena (PbS), while other metal sulfides, such as sphalerite (ZnS), chalcopyrite (CuFeS2) and pyrite (FeS2), were basically unaffected.

Jan 1, 2014

By R. J. T. Charles

Introduction An apparatus that will measure the surface area of a few of the simple minerals with a high degree of accuracy has been described by J. W. Bell (1). His apparatus consisted essentially of a photometric device that would measure the turbidity of fine particle suspensions. Turbidity, in this case, was considered as a function of surface area. Bell&apos;s method of surface area determination seemed to offer possibilities of extension and improvement to the point where it might approach a general method of particle size measurement. Theoretical and Practical Considerations of the Photometric Method In order to illustrate how turbidity may be considered as a function of average particle size, and to indicate the type of results expected from a photometric method of particle size measurement involving turbidity, the following theory may be hypothecated. If a number of particles, considered as spheres of uniform diameter, are placed at random in the path of a beam of light, the following expression, which will give the change in light intensity as a function of the diameter of the particles, the specific gravity of the material, and the weight involved, can be formulated from the Beer-Lambert Law:

Jan 1, 1951

By Y. N. Zhang

Friction Stir Welding (F SW) is a novel "green" manufacturing technique due to its energy efficiency and environmental friendliness. This solid-state joining process involves a rotating tool consisting of a shoulder and/or a probe. The shoulder applies a downward pressure to the work-piece surface, constrains the plasticized material around the probe, generates heat through the friction and causes plastic deformation in a relatively thin layer under the bottom surface of the shoulder. The rotating probe mainly drags along, plasticizes, and mixes the adjacent material in the stir zone, creating a joint without fusion. Friction Stir Processing (FSP), a variant of FSW, has been developed to manufacture composites, locally eliminate casting defects, refine microstructure and/or improve the associated mechanical and physical properties including strength, ductility, fatigue, creep, formability and corrosion resistance. However, major challenges such as tool design and wear currently limit the use of F SW/P for manufacturing applications, particularly for high melting temperature or high strength alloys. In this review, the FSW/P tools are briefly summarized in terms of the tool types, shapes, dimensions, materials and wear behaviors.

Jan 1, 2011

By A. W. Jolliffe

AEROPROSPECTING may be defined as the application of the air view to the search for mineral deposits. The term is suggested as a preferable alternative to either aerial prospecting (which may be confused with areal prospecting) or air prospecting. The air view may be obtained by visual observation from an aircraft or by examination of air photographs; each has its particular advantages and disadvantages. Aeroprospecting should be regarded only as an aid to, and not as a substitute for, accepted prospecting methods ( l ). The Precambrian region north of Great Slave lake consists of two well defined physiographic units, a feature first noted by J. T. Wilson (2). The boundary between these lies close to the north shore of the east arm of the lake and extends northwesterly near Spencer, Beniah, Carp, and Ghost lakes (Figure 1). South and west of this line, exposed bed-rock makes up the greater part of the land area; eskers are very rare, and overburden is largely limited to rock-walled valleys and depressions. North and east of the line, outcrops are rare or absent, eskers are abundant, and most of the surface consists of drumlin-like drift hills, elongated parallel to the direction of ice movement (Figure 2). Where this boundary passes through the area shown in Figure 1, it lies near the 1,200-foot contour and may mark the maximum extent of the lake or sea arm present in this vicinity toward the end of the Pleistocene period. For convenience, the first area may be called the &apos;bed-rock belt&apos; and the other the &apos;drift belt&apos;.

Jan 1, 1945