Showing papers in "Geoscience Canada in 1976"

Facies Models 2. Turbidites and Associated Coarse Clastic Deposits

Abstract: lntroduetlon To the sedimentologist. Me turbidity current concept is both simple and elegant. Each turb~dite (defined as the deposit of aturbidity current) is the result of a single, short lived event, and once deposited, it is extremely unlikely to be rewciked by other currents. The concept is elegant because it allows the interpretation of thousands of graded sandstone beds, alternating with shales. as the result of a series of similar events. and it can safely be stated that nosimilar volume of clastic rock can be interpreted so simply. In this review. I will begin by studying the "classical" turbidite, and will then gradually broaden the scale to encompass turbidites and related coarse clastic rocks in their typical depositional environments deep sea fans and abyssal plains. The concept of turbidites was introduced to the geological profession in 1950. At that time, nobody had observed a modern turbidity current in the ocean, yet the evidence for density currents had become overwhelming. The concept accounted for graded sandstone beds that lacked evidence of shallow water reworking, and it accounted for transported shallow water forams in the sandstones, yet bathyal or abyssal benthonic forams in interbedded shales. Low density currents were known in lakes and reservoirs, and they appeared to be competent to transport sediment for fairly long distances. Many of these different lines of evidence were pulled together by Kuenen and Migliorini in 1950 when they publishedtheir experimental results in a now classic paper on "Turbidity currents as a cause of graded bedding". A full review of why and how the concept was established in geology has recently been published (Walker. 1973). After its introduction in 1950, the turbidity current interpretation was applied to rocks of many different ages. in many different places. Emphasis was laid upon describing a vast and new assemblage of sedimentary structures. and using those structures to interpret paleocurrent directions. In the absence of a turbidite lacies model (see pevious article in this issue of Geoscience Canada), there was no norm with which lo compare individual examples, no framework for organizing observations. no logical basis for prediction in new situations, and no basis for a consistent hydrodynamic interpretation. Yet gradually duringthe years 1950-1 960, a relatively small but consistent set of sedimentary features began to be associated with turbidites. These are considered in the following list, and can now be taken as a set of descriptors for classical turbidites: 1 ) Sandstone beds had abrupt, sharp bases, and tended to grade upward into finer sand. silt and mud. Some of the mud was introduced into the basin by the turbidity current (it conta~ned shallow benthonic forams), but the uppermost very fine mud contained bathyal or abyssal benthonic forams and represented the constant slow rain of mud onto the ocean floor. 2) On the undersurface (sole) of the sandstones there were abundant markings, now classified into three types: tool marks, carved into the underlying mud by rigid tools (sticks. stones) in the turbidity current; scour marks, cut into the underlying mud by fluid scour: and organic markings trails and burrows filled in by the turbidity current and thus peserved on the sole. The tool and scour markings give an accurate indication of local flow directions of theturbidity currents, and by now, many thousands have been measured and used to reconstruct paleoflow patterns in hundreds of turbidiie basins. 3) Within the graded sandstone beds. many different sedimentary structures were recorded. By thelate 1950s, some authors were proposing turbidite models, or ideal turbidiies. based upon a generalization of these sedimentary structures and the sequence in which they occurred. This generalization is akin tothe distillation process discussed in the previous paper, and the final distillation and publication of the presently accepted model was done by Arnold Bouma in 1962. A version of the Bouma model is shown in Figure 1

Canada's Active Western Margin: The Case for Subduction

Abstract: lntmduetlon Some of the questions that most commonly arise in studies of the recent tectonics of south-western British Columbia are 'when and where has subduction taken place along the continental margin?' and 'is subduction still going on today?'. Being actively involved in both onshore and onshore studies of this region, we felt that it would be useful to review all the important data which bear on these questions. While admitting that our special interests have led us to emphasize particular aspects of the many fields of geology and geophysics relevant tothe problem, the exercise has nevertheless considerably clarified our own ideas. It will, we hope, be similarly useful to others whether or not they agree with our conclusions that subduction has occurred and is still occurring. established the presence and basic bathymetric trench at the foot of the configuration of an active spreading continental slope, the absence of a ocean ridge system ofl the west coast of clearly defined eastward dipping Beniofl Vancwver Island. The theory of the earthquake zone and the apparently geometrical mwement of rigid quiescent state of present volcanism lithospheric plates on a spherical earth have all contributed toward a (introduced as the 'paving stone' theory) widespreaa uncertalnfy as to whether was tirst ~ r o ~ o s e d and tasted bv subddctlon 1s cbrrently taking place ~ c ~ e n z i i and Parker (1 967) using data (e.8.. Crosson. 1972: ~rivast&a, 1973; from the N. Pacific and in the global Stacey. 1973). Past subduction, fran extension of the theory by Morgan several tens of m.y. ago until at leastone (1 968) this reglon again played a major or two m y. ago. IS more generally role Morgan alsoconcluded that a small accepted ana it seems to us that the block e i t of theJuandeFuca ridge (the Juan de Fuca plate. Fig. 2) was moving independently of the main Pacific plate. The possibility that theJuan de Fuca plate is now underthrusting North America was first suggested by McKenzie and Parker (1967). They noted that consumptionof oceanic crust case for contemporary subduction, in a large part, must beargued upona continuation into the present of the processes shown to be active in the recent geological past. In this article we anempt to treat systematically each of themainsources of information on whether or not

A Deep Tow High Resolution Seismic System for Continental Shelf Mapping

Abstract: Trials of a deep tow high resolution seismic system (DTS) intended lor marine surficial geological mapping are described. The development ol this equipment is the consequence ol an engineering and scientific partnership between industry and government through implementation of various government policies intended to encourage Canadlan Industry. The system is capable of penetrating acoustically \"hard\" bottoms to depths in excess of33 m and ''son'' bottoms to at least 100 m. Its hlgh resolution (less than 0.3 m) and repeatable pulse shape make it an ideal source lor identifying and mapping sea floor sediments. Sample records, accompanied by geological interpretations from areas of widely differing geology are included.

Facies Models 1. General Introduction

Abstract: Purpole of Serler This article is a general introduction to a proposed series of articles on sedimentary lacies models. They will appear roughly one per issue in Geoscience Canada, and are intended to review specific sedimentary environments. Thearticles will be written lor the non-specialist who wishes or needs to be aware of current ideas in environmental interpretation and prediction. There will be a minimum of text, a maximum of illustrations, and a bibliography so short that there is a reasonable chance for the nonspecial~st-sedimentologist to read a l~ttle farther and painlessly find his way into a maze of literature. Obviously, we will stress review papers and classic examples, using Canadian examples wherever possible.

Methods for Recording Great Lakes Shoreline Change

Abstract: Presently available methods and techniques for monitoring changes of certain geophysical aspects of theGreat Lakes shoreline can be classified in two groups: I ) Historical recordsdating backto early exploration days exist in the form of navigational charts, old survey records and photographs. However they were not intended for the purpose of monaoring changes in the coastal zone processes. Hence the value is limited in recording these phenomena. 2) Scientific observations ranging from synoptic overview (satellite) to ground measurement (erosion proR~e) are examined and discussed in general with a closer look at the nature and ~ concentration of suspended loads, bathymetry and currents, wave cltmate. erosion and accretion rates. Site specific studies of the coastal processes are also discussed.

Sediment and Nutrient Yield from Great Lakes Tributary Drainage, Canada

Abstract: The role of tributary drainage, as one primary source of sediment and nutrient loads to the Great Lakes, is outlined within the context both of historic cultural impact on land drainage and of relative importance of contemporary point and diffuse sources. Regional trends and panernsof sediment, nutrient and chloride yields to the four Canadian Great Lakes are created from Ontario Ministry ofthe Environment period-ofrecord water quality surveillance data files collected at or near the mouths of 102 rivers and creeks. Limitations both of raw data and analyses employed herein are briefly explored. Denudational equivalents should be used with caution. The understanding of water quality of the Great Lakes must take into account a variety of inputs: -tributary drainage. flow from connecting waterways, industrial and municipal effluent discharged directly into the lacustrine environment, and biochemicalcycling in the water column and lake sediments. This paper deals with the role of tributary drainage as one primary source of sediment and nutrient loads to the Great Lakes. Since colonial deforestation, loadings of sediment and nutrient have increased many fold an observation which is well documented in the Great Lakes literature (Lewis and McNeely. 1957: Basset and Terasmae. 1962; Upchurch. 1972; Kemp eta/.. 1974.1976).Although Southern Ontario may be regarded as a low energy environment relative to other geomorphic environments. deforestation is accompanied by significant changes in runoff regimes wherein storm and melt runoff produce shorter runoff events with greater discharge peaks than under forested conditions. Hence, in agricultural southern Ontario where deforestation is virtually complete, significantly greater energy is available during runoff events than in precolonial times. This increased energy is parlicularly important in mobilizing clastic sediments. Ailhough agricultural disturbance of land surfaces is Lakes are dominated by shore bluff erosion (Kemp et a/. 1976). fluvially transported particulates are of interest in studies of water qualay because of the capacity of the finer fraction to transport significant quantities of adsorbed phosphorus and nitrogen. Because suspended sediment is dischargedependent the systematic monitoring of sediment loads presents large sampiing problems. As will be noted below, our understanding of total suspended sediment loads into the Great Lakes is far from adequate. The temporal change in solute loadings has received extensive study, particularly in a comprehensive report to the International Joint Commission (1969). In addition to discharge from connecting waterways, solute loadings of point or diffuse source origin are routed into the Great Lakes both by tributary riversanddirect dischargefrom municipaland industrial sources located on Great Lakes shores. The relative importance of these two routes is difficult to assess. The International Joint Commission (1 969) calculated that nine per cent of total phosphorus and five per cent of total nitrogen loadings to Lake Erie were attributable to direct discharge -most of which originated on the U.S. side. Comparable values have not been calculated for Lake Ontario. where the densely populated Canadian side is serviced primarily by municipal sewerage systems discharging directly into the Lake. The relative importance of land drainage vis-a-vis direct flow to lake may, therefore, be less for Lake Ontario than for the rest of the Canadian Great Lakes. As can be seen from the above comments, the study of land drainage to the Great Lakes is not intended to convey a holistic picture of land-based n~.,~ml undoubtedly the primary provenance of activity. It representsonly those land use . .-\"...Le rBle des affluents en tant que source principale d'apport aux Grands Lacs en sediments et substances nutritives est discutb dans le double contexte de I'impact culture1 historique sur le bassin versant et de I'importance relative des sources contemporaines ponctuelles et diffuses. Les changementset la distribution par region des charges en sediments, substances nutritives et chlorures aux quatre Grands Lacs Canadiens sont Btablis B partir de donnees recueillies A proximite de I'embouchilre de 102 rivibres et most clastic load, an unanswered research question is the degree to which bank failure and floodplain modification act as sediment sources following channel geometry changes in response to deforested hydrologic regimes. In terms of sedimentation into Lakes basins, post-settlement increases by factors of three and four were found by Kemp et a/. (1 974). Nevertheless. such estimates must err on the low side as the coarse fraction of the fluvial load remains in the littoral zone. While total particulate loads supplied to the Great activities which contribute to fluvial water quality. River mouth data. therefore, reflect diffuse sources which may be both natural and anthropogenic. and such direct sources which are input directly into fluvial systems. In general. therefore agricultural impact, such as is. is documented by river data. In large watersheds with significant urban and/or industrial concentrations, river water qualify may be signilicantly affected and therefore monitorable some distance downstream. Geoscience Canada. Volurne3. Number 3. August. 1976 Recognizing the necessity of Tab* l understandim the relationshi~s Number of msms' (lo 1972) between tribuiarv drainage and Great ~ ~ Lakes' waterquility, the'~ollution From Hvon Humn Land Use Activities Reference Group' Ontrrlo E r k @oU(h) ( M h ) sup.rloT (PLUARG) was established by the Water Ouatly 50 19 17 83 8 International Joint Commission in 1973. 26 13 11 9 18 As part of the PLUARG activities, an assessment was to be made of all available water quality and discharge records for Great Lakes' tributary drainage. The first phase of this assessment has been completed for Canadian data and is the subject ofthis report. It must be emphashed at the outset that the data presented represent a 'first look' at regional trends. As will be noted below, the currently available data files are subject to a number of systematic biases which are under examination through ongoing PLUARG studies. Data B m The data base consists of two data files. The first includes all (reasonably) continuously monitored discharge records collected across the Province of Ontario by the Water Survey of Canada. These data are in the form of daily mean and monthly mean discharge in cubic feet per second (cis). The records used here are generally near but not at the mouth of larger tributary rivers and creeks. The second data file contains routinely monitored concentrations for the following water quality parameters: total solids suspended solids total phosphorus as P (TP) soluble reactive phosphorus as P (SRP) ammonia as nitrogen (NH3-N) total kjeldahl (TK) nitrate as nitrogen (NO3-N) nitrke as nitrogen (NO,-N) chloride Dissolved solids may be obtained by subtracting suspended from total solids. Occasionally available are: hardness as CaCO, total iron alkalinity as CaCO, These data, collected and made available by the Ontario Ministry of the Foolnotes lexcludes basins tributary toconnecting waterways 2reasonably complete records sincludes both the Mwn and Muskoka River outlets of the Muskoka watershed monitoring was begun in 1964 in most of the Lower Lakes'and Southern Huron tributary watersheds. The Upper Lakes are generally represented by only a few sample years. Lake Superior was not fully monitored until 1973. In a report to the International Joint Commission (Ongley, 1974) the data are processed by individual watershed for period of record to 1972. Using the same period the data are now aggregated by Great Lake for the purpose of inter-lake comparison. It should be noted that inputs via connecting waterways are excluded from this study. Although it is not possible to make a unique distinction between watersheds draining agricultural Southern Ontario and forested Precambrian Northern Ontario, the Trent-Severn system provides a convenient separation (Fig. 1). Lake Huron data have been divided into Southern Huron (agricultural) and Northern Huron (forested). It should be noted that most of the tributary systems to Lake Ontario, from the Trent eastwards, cover a proportion of Shield terrain. Llmltatlon and Melhodn ot Data -.I* The limitations of the data set and consequent methods of analysis have been reported previously (Ongley. 1974; 1976) and it was noted that data limitations imposecertain restrictionson analysis which may well prove to be substantially in error. NORTHERN e m R Y OF T R E N T SEVERN WUTERSmOS AGRICULTURAL SOUTHERN M i T A R l O Environment for the entire (Canadian) Great Lakes, average one to two samples per month taken at or very near the mouth of most tributary Flour* 1 watercourses. The numbers of n rial lakes Watershed illuslraling division oi watersheds for which data are available Canadian Tribularv Drainage inlo ~ . . ~~ are enumerated in Table I. Routine agricullural, carbonale ~oufhern Onlario and Precambrian Northern Onlario. 1 )Water quality data are generally available for only one or two days per month. Moreover, collection of samples has been predicted by sampling convenience rather than an attempt to sample over ranges of stage or range of antecedent conditions. Inevitably then. sampling is biased towards low flow. In view of the limited sample size and bias towards low flow it has not been possible to compute the mathematical relationships between parameter concentration and discharge. Hence. monthly mean values of concentraion and flow wereemployed to yieldmonthly loadings in the full knowledge that products of means will not provide the accuracy of more complete experimental data sets. An assessment of this procedure is currently underway through ongoing PLUARG studies. monthly mean values of concentration and flow wereemployedto yieldmonthly mean annual loadings. This p

The Soil Column: Geology, Land-Use, and Conservation of the Quaternary Barrier System of Wasaga Beach, Ontario

Abstract: Man is finally becoming aware of the limitations of his habitat on Earth. He is now striving to use natural resources without unduly disturbing or pollutingthe natural environment. However. increasing population requires increased development of lands for habitation and recreation. In densely populated areas, modifications of natural landscapes occur rapidly; in these areas there is an obvious need to maintain a variable and pleasant environment in which to live. Remote. inaccessible wilderness regions preserve examples of natural phenomena and act as reservoirs for living things. However, examples of natural landscapes should also be maintained in densely populated regions SO that many individuals may visit them for recreation and educational purposes. In land use planning, values that are seldom considered relate to the geological and geomorphological history ofthe landscape. The primary objectiveof this article is to contribute some information concerning the geology and geomorphology of Wasaga Beach. Ontario(Eig. I ) , by stressing its unique character. the slow processes that formed it, and the necessity for careful land-use planning and conservation. The geological system of Wasaga Beach comprises Pleistocene (Wisconsin) till sheets overlain by glacio-fluvial and lacustrine sands and gravels. A-barrier complex\" was formed in the last 6800 years through accretion of spits, beaches and sub-aerial sand dunes (Martini. 1975). Similar complexes exist along the coasts of the Great Lakes, and contain much information for decipheringthe history of