LEDA: A flexible codification system for computer-based files of geological field data

Computers & Geosctences. Vol. 1, pp 26~278. Pergamon Press, 1976. Printed in Great Britain

LEDA: A FLEXIBLE CODIFICATION SYSTEM FOR COMPUTER-BASED FILES OF GEOLOGICAL FIELD DATA 1 PETER P, DAXqD and JACQUES LEBUIS Department of Geology, University of Montreal, Montreal, Canada and Department of Natural Resources, Quebec City, Canada (Received 21 March 1975; revised 10 September 1975)

Abstract--The LEDA system, developed for the codification of field data and information, is user, machine, and geology oriented. It is used to codify stratigraphic and morphologic data required in mapping Quaternary deposits. Flexibility in the system is achieved by the selection of distinct types of data as units of data collection, which are reported on six type-cards extending the length of an 80-column punchcard. These type-cards are (1) Location, (2) Stratigraphic Unit, (3) Composition, (4) Orientation (5) Commentary, and (6) Stratigraphic Measurement. The type-cards are reproduced on pocket-size field data sheets in the following order: (1) one card for the location and one card for the description of a unit; (2) two cards for the description of units; (3) three cards for composition or orientation data; (4) four cards for commentary; and (5) two cards for stratigraphic measurements. There is an additional field sheet provided for diagrams and polaroid photos, the information of which is not codifiable. In the field, the sheets are placed in a loose-leaf binder with a flipout chart containing the code. The link between the type-cards making up a station file is provided by the field station code which occurs on each card in the data file but is reported only once on each field sheet. The filling out of the location card is obligatory for any particular station, whereas the other cards may be used in any order or number according to the type and length of information sought. Key Words: Coding, Geomorphology. Mapping, Stratigraphy.

INTRODUCTION

Recent developments in computer technology have made it possible to apply computer-based data-processing systems to geological mapping. The widespread use of this new tool in field work is witnessed by the number of field data codification systems which are currently in use all over the world (Hru~ka and Burk, 1971: Hubaux, 1972). The reasons for using the computer as an aid in mapping are (Haugh, Brisbin, and Turek. 1%7; WynneEdwards and others, 1970: Berner and others, 1971; David and Lebuis, 1973): (1) the large volume of field data collected in a mapping project which lasts for several years and involves a number of geologists; (2) the ease by which this volume of data can be handled rapidly and efficiently by the computer; (3) the systematization of field data neccessitated by the use of the computer; (4) the ease by which field notes of several geologists can be merged into a single data file created for a project; and (5) the elimination of the "virtual loss" of some information collected the "conventional way". In 1970, the Quebec Department of Natural Resources undertook a project of mapping Quaternary deposits in the Gasp6 Peninsula. The project was planned to last for a period of five years, each year employing a number of geologists. Foreseeing the large volume and the great variety of information that would be collected in the project, the authors developed a computer-based mapping system, called LEDA (from LEbuis-DAvid), to aid in the ~Published with permission of the Quebec Department of Natural Resources.

collection of field data and to make that data computer processable. In this paper, the authors describe the LEDA system, its philosophy and some of its practical applications. A more detailed description of the use of the system is contained in a field instruction manual (Lebuis and David, 1973) that is available from either one of the authors. CHARACTERISTICSOF THE LFJ)A SYSTEM

The most important qualities that characterize the LEDA system are as follows: (1) the LEDA system is geologist oriented as well as machine oriented; (2) it is equally geology oriented inasmuch as it is flexible and can be applied to any geological situation encountered in mapping; (3) the system does not restrict the type and the quantity of information that may be collected; and finally, (4) the systematization of field data, inherent in a computer-based codification system, does not adversely affect the quality of the data. The features that make the LEDA system geologist oriented are many and they are all related to specific aspects of the system. Some of these aspects, which are discussed in subsequent paragraphs, are the language and the physical layout of the code; the size and the color of printing of the field data sheets; the layout of the data cards and the size of the data squares on them; the small number of "uselessly" filled columns; the compactness of field notes with small quantities of unused space; and finally, the freedom given to the geologist in making his field notes best suitable to the local geology. This last feature also preserves the high quality of the data. The LEDA system also is machine oriented because the data 265

266

PETER P. DAVID and JACQUES LEBUIS

are machine processable. Flexibility of the LEDA system is due to the choice of data types as units of information collection, reported on a set of data cards used in any required order and number,

DEVELOPINGTHE LEDASYSTEM The diagram in Fig. 1 outlines, in a general manner, the steps that may be taken in developing field data codification systems. The LEDA system, in fact, was developed following these steps. The first item identified on the diagram is the specific field project which, in the situation of the LEDA system, is the Gas# Project of mapping Quaternary deposits. The next item is the question whether the project requires data only or both data and information. Geological mapping, in general, and mapping Quaternary deposits, in particular, require both data and information, implying that not only measurements and descriptions are made in the field but interpretations and commentaries also are recorded. Next on the diagram the question of data type is raised. In mapping Quaternary deposits both morphologic and stratigrapic data and information are required, that is, at any particular station data may be collected both "from the surface" and "from depth". In other words, besides station location, topography, and outcrop descriptions, data are required about stratigraphic units and about erosional and constructional features produced by a variety of morphologic processes. The next step, as noted on the diagram, is the selection of a suitable format for the input document which would

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serve as the unit of data collection. As suggested on the diagram, there are two possible choices for the selection of input document format: the first choice is the use of a single input data sheet with a sequential arrangement of all the data and, the second choice is the use of a number of independent data cards, each vith a distinct type of data. Whereas most codification systems have adopted the single data sheet for input document (Haugh, Brisbin and Turek, 1%7; Burns, Marshall, and Gee, 1%9; WynneEdwards and others, 1970; Berner and others, 1971), other systems divided their data into two or more groups, either because of space restriction (Turner, 1%7; and several other unpublished Canadian systems known to the senior author and reported in Hubaux, 1972), or to attain some degree of flexibility (Hutchison and Roddick, 1%8). The single data sheet with its rigorous order and fixed quantity of codified data restricts the amount and type of information that may be collected. If at a specific observation station field data is in excess of the space available on one field sheet, an additional data sheet may have to be used. This, however, increases the number of inefficiently used data sheets. Nevertheless, it should be noted that the choice of a single input document sheet employed by the described systems is a logical one, because most of these systems are used to codify routine mineralogical, petrological, structural and drillhole data, where the quantity and type of data range only slightly and within certain limits. It is in this respect that the requirements for the LEDA system differ inasmuch as the possible variations in the quantity and type of morphologic and stratigraphic data could not be foreseen, not even within a small region. For the development of the LEDA system, therefore, the second choice of input document format was selected. Instead of using the single data sheet as the unit of data collection, the authors selected a group of distinct types of data, recorded on individual punchcards, as units of data collection. It is evident that the field data required in mapping Quaternary deposits can be separated into distinct categories according to their definite frequency of occurrence at an observation station. These categories are as follows: (1) description of station location, outcrop and topography; (2) partial description of a stratigraphic unit; (3) composition of a stratigraphic unit; (4) orientation of structues or of morphological elements; (5) commentary; and (6) detailed stratigraphic measurements. These groups of data types provide the basis for the establishment of the six type-cards which are described in the following paragraphs. LEDATYPE.CARll~ The six groups of data described in the preceding paragraphs are recorded on six type-cards (Fig. 2), each the length of an 80-column computer punchcard. The detailed information recorded on each card is as follows: (1) The first type-card is used to record the date of observation and the location of a field station using UTM

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also is given. Furthermore, there is space provided for the identification of ground photographs taken at the station, using film-roll number, the order number of the first photograph on the roll taken at the station and the total

268

PETER P. DAVID and JACOUES LEBUIS

number of photographs taken. The number of field sheets used for sketches (see description of field sheets) also is recorded. On this same card, routine, repetitive stratigraphic observations involving not more than two stratigraphic units also may be made by identifying a former reference station where the same units have been described and by stating on the card the thickness of the units as measured at the new station. If there are more than two units at the new station, their detailed description is warranted by geological considerations. The first type-card is always the first card or may even be the only card at a particular station, because it is the single card required to create an observation station. (2) The second type-card is provided for the partial description of a stratigraphic unit and it contains the following information: order number, thickness, sediment type, bedform, and nature of lower contact of a unit; state of oxidation, chemical character, color, organic-matter content, and percent composition and particle shape of grain-size fractions of the sediment; a list of coded primary sedimentary and secondary deformation structures, interpretation of the sediment and identification of two samples. (3) The third type-card is provided for recording either quantitatively or qualitatively the lithologic, mineralogic, fossil, etc. content of a stratigraphic unit or of any other geological object, for example, the lithologic composition of glacial erratics lying on the land surface at or around the observation station. On one card there is space provided for recording eight compositional elements and one sample which may be a collection of rock chips or fossils. (4) The fourth type-card is used to record measurements of any type of orientational data, for example structural attributes of stratigraphic units, orientation of glacial striations or of the regional slope, or even the orientation of panoramic ground photos (!). Physically, this card has the same arrangement of "squares" as the preceding card with space provided for eight measurements, however, there is one column per measurement left unused on this card. (5) The fifth type-card provides space for codified commentary and it also may be used to record samples taken from a stratigraphic unit in excess of two. (6) The sixth type-card is used to record detailed measurements of the thickness of stratigraphic subunits that may occur within a composite unit. The unit of measurement for each subunit may change from millimeter to meter giving a greater flexibility to the measurements. Each type-card is identified by a code number preprinted in column 80. except on cards three and four which physically are the same. There, the geologist has to mark the code number according to the specific type of information recorded on the card. The code of the type-cards is for the identification of the recorded information types and is used in the punching of the computer cards and in the computer validation of the data file. The first two columns on each data card are reserved for the pagination of the cards to ensure their correct sequential order of entry in a station file. On type-card one

the figure ' T ' is preprinted in the second column. Columns three and four on each data cards are used for tile identification of the subject matter (see LEDA codet treated on a particular data card. In the situation of the first type-card, which is used for station location, the subject code "LO" that stands for "location" is preprinted. In the situation of the second type-card, which is used for the partial description of stratigraphic units. columns three and four are used for the numerical identification of stratigraphic units. The order of sequence of the use of the type-cards is shown in two different forms in Figs. 3 and 4. It is evident from the diagrams that type-card No. I has to be the first card at a particular station because it defines in space an observation station. Type-card No. 6 is used only in conjunction with type-card No. 2 if the latter has been used to describe composite stratigraphic units. The other type-cards can be used in any order. As far as the number of copies of any of the type-cards is concerned, the following rules apply: only one copy of type-card No. 1 can be used for a particular station; one copy of type-card No. 2 suffices for the partial description of a simple stratigraphic unit. However. a separate copy of this type-card is used for each stratigraphic unit in a particular exposure. Finally, as many copies of the other four type-cards may be used for each subject matter as is made necessary by the length of the data.

FIELD DATASHEErs

The six type-cards described in the preceding paragraphs are reproduced for field use on standard pocket-size field sheets of I 1.0 × 17.5 cm (Fig. 5) that can be placed in a "conventional" Iooseleaf binder (Fig. 6). With the exception of the first field sheet, each of them has two or more copies of the same type-card. The arrangement of the data cards on the field sheets, is as follows: The first field sheet contains one card for recording the location of a field station and one card for the description of a stratigraphic unit. The second sheet has two cards for the description of stratigraphic units. The third sheet contains three cards for recording either composition or orientation data. On the fourth sheet there are four cards for commentary. The fifth sheet has two cards for detailed stratigraphic measurements. There is an additional field sheet provided for diagrams, sketches, and polaroid photographs. The information on this last sheet is not codifiable. The number of cards reproduced on one field sheet is limited only by the size of the individual type-cards, leaving the data "squares" large enough for convenient use. Although the use of conveniently sized "squares" limits the number of cards that may be printed on one field sheet, the use of smaller squares would only decrease the clarity of writing and consequently would increase the frequency of error in the punching of the computer cards. Although the question of the size of squares seems trivial, it is an important point when field conditions under which note taking, demanding clearly printed symbols, are considered. The field data sheets are printed in green rather than black because experience indicates that green is more

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1 Figure 3. Flowchart showingpermissible order of type-cards used in mapping. pleasing to the eye and if part of a symbol is written on a line it remains legible. The edge of all the first field sheets are painted red with a marker to'facilitate the rapid manipulation of station files in the field office during preliminary validation of data. STATION FILE A h ~ DATA B,g~,K

The data file of each station consists of all the field sheets used for that location. The field sheets of a station file are arranged according to the order number of the sheets. Subsequent to the punching of the computer cards, each station file consists of a set of computer cards arranged according to the card order number. When field CAGEO Vol 1, No 4---D

data are registered on magnetic tapes forming the data bank of a project, each station file begins with a "map" showing the order in which the different type-cards occur within that file. The map is followed by the chain of data in the same order as they are on the punchcards. The link among the individual data cards of a station file is provided by the station code consisting of four parameters that occupy nine columns on the data cards from column five to column thirteen, inclusively. These parameters are. in order of occurrence, the code of the geologist, code of the region, station number and the last two numbers of the year of observation. The station code is marked only once, on the first card of each field sheet,

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Although the first type is limited in extent and is simpler in form. the second type is complete and, therefore, universal I I in character. The LEDA code described here is of the first Figure 4. LEDA octahedral. Diagrammatic presentation of entry type and is developed to serve Quaternary geologists in the order of type-cards in LEDA system. Province of Quebec. Although it may he applied to the study of Quaternary geology in other areas, it would certainly require modifications to meet local requirements. IL ' I COMPOSITION The requirements for the language and for the structure , :: OR of a well-organized local code which is to be both LOCATION Ii STRATIGRAPHIC ORIENTATION OUTCROP !I ; UNIT [ I . . . . . . . . . . . . . . . . . geologist and machine oriented may be summarized as TOPOGRAPHY I I COMPOSITION follows: I ;i . . . . . . . . . . . . . . . . . OR II) The coded expressions should have a unique . . . . . . . . . . . !i . . . . . . . . . . . . . . ORIENTATIIJN 'i . . . . meaning, should be short and easily understandable, and STIq ATIGRARHIC i STRATIGRAPHIC . . . . . . . . . . . . . . rSON4PO S I T I D N ~NIT !i UNIT should be adopted from a set of established abbreviations. (2) The code should not have such dubious and :i J QRIE ~'4TATIO N ! . . . . . . . . . . meaningless expressions as the term "other". . . . . . . . . (3) No geological subject should have more than one COMMeNtARY i . . . . l++~r+S CO_+D~a .~_ATE~ coded expression even if it occurs under more than one i ++ heading in the code. . . . . . . . . . ~ ] STRATIGRAPHIC ~-+(4) The list of codes should be expanded easily during COMMENTARY i MEASUREMENT ..... DIAGRAMS i the field season or whenever it becomes necessary. For i ~'ND this reason the categories in the code should be open COMMEN]ARY l: [-~-[T POLAROID ended. . . . . . STRATIGRAPHIC j pI4OTOS (5) The layout of the code should be simple, that is, the +-- - MEASUREMENT " ; COMMENTARY ~ I ~ --order of subsequent headings on the chart containing the JL ...... code should more or less follow the layout of the input Figure 5. LEDA fieldsheets sh°wing p°siti°n °f typecards" documents. (61 In order to comply with the requirements under 2, 4 however, it is automatically reproduced for all the other and 5, the coded expressions should be printed for field "used" cards of the same field sheet during punching of use on a chart separate from the field data sheets. The latest version of the LEDA code, a slightly the computer cards. modified English translation of which is given in Table 1, THE CODE complies with all the listed requirements. In view of the first requirement, the most important The code is the most important part of a computerbased codification system, because it is the vocabulary guideline in coining the coded expressions is to keep the with which lengthy information is transformed into a expressions as short as possible in order to have the least more efficient abbreviated form. From a practical point of amount of necessary writing in the field and to be able to view, the authors recognize two types of codes, a local record more information on less field sheets. The length of and a national code. The first type is developed for a a specific coded expression and the type of symbol used specific branch of geology and serves geologists working for the code are determined on the basis of the number of within an area limited by administrative boundaries. The items that are to be codified under a particular heading. If second type is developed for all the branches of geology this number is less than 25, a one-symbol code of either and serves geologists on a national or international level. numerical or alphabetical character is used. Furthermore, 7 Daagrams & Polaroid Photos

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LEDA: A flexibilecodificationsystemfor computer-basedfilesof geologicalfielddata if the number of items under a particular heading is less than ten the list of code starts with the numerical symbols and, if it is greater than ten the code starts with the alphabetical symbols. As new items are added to a heading during subsequent field seasons and the type of symbol used is exhausted, the code continues with the other symbol type (cf. "structures" and "location in unit" in Table I). If the number of items under a heading is in excess of 25, a two-symbol code is adopted. The two-symbol codes are generally alphabetical except when a subdivision of a coded item is required. For example, in the situation of rock names, if there are several distinct varieties of a rock type within a region, the code for the subtypes is made of a letter and a number symbols (cf. "varieties of granite" in Table 1). Although these subtypes may have identical name designations in the code, they are identified by type samples, small chips of which may be taken to the field for reference. The alphabetical coded expressions of rock, mineral, and sediment names are all adopted from abbreviations that are in use by a number of Quaternary geologists. These abbreviations do not follow the method of derivation of mnemonic names as suggested by Burk (1966) and by Brisbin and Ediger (1967), nor do they correspond to the four-letter coded expressions already in use in the Grenville Project of the Quebec Department of Natural Resources (Sharma, Laurin, and WynneEdwards. 1972). The authors felt that because the LEDA code was to be used locally, the implementation of a simple code seemed more conveninent. Nevertheless, the authors recognize the importance of the use of standardized mnemonic names in a universally accepted code for the exchange of geological information on a national or international level. Once such a code is accepted, data from a local project's data bank may be made available through the use of a vocabulary of the locally employed coded expressions. The second requirement of an effective code, regarding the use of the term "other", is an important one, because it concerns a number of codification systems in use. We feel that the use of "other" as a so-called "coded expression" is inexplicable, illogical, useless, and may be detrimental to the quality of field notes. The inclusion of this term in the recommendations for setting up codification systems made by Brisbin and Ediger (1967) is an error. In the opinion of the authors, this term is detrimental to the quality of field notes because it tends to dim the initiative of geologists and in fact, may "straitjacket" their ideas (cf. Wynne-Edwards and others, 1970, on the question of "strait-jacket"). The term is useless because it represents unacquired information or, rather, acquired but "unavailable" information but not in the sense of "unknown" or "unidentified". The introduction of this term in a code is illogical because geologists do not generally employ this term in their field notes made the "conventional way". The impact of the use of this term in the code of some of the codification systems is lessened by making allowance for the specification of the term "other", either in the section of uncodified but computer-processable descriptive notes (Haugh, Brisbin, and Turek, 1967) or by simply writing on the back of the field data sheet (Berner and others, 1971). Nevertheless.

271

because in most systems the term cannot be retraced to its original, intended meaning, its use introduces ambiguity in a data file and it takes up invaluable space by increasing the volume of data without '"adding" information to it. Although, the third requirement sounds self evident, it is mentioned here because an earlier version of the LEDA code (Lebuis and David. 1973). already in circulation. deviates from this point. In that version of the code the term "roche de fond" ("bedrock") occurs under several headings but with different coded expression. The reason for this discrepancy is historical and is due to the manner by which the LEDA code developed throughout the years. The fourth requirement, that a code should be updatable, makes it necessary that each heading in the code should be open ended. It is in this respect that the use of the term "other" in a code is understandable when the coded expressions are printed on the input documents and the code cannot be readily updated. However. updating of a code is necessary and is logical. That is the only method to keep a code flexible the same manner as field notes taken the "conventional way" are flexible. If something "new" is found in the field, it should be codified and be temporarily introduced on the code chart of all the geologists working in the same field party. Permanent additions to the code can be made at the end of the field season without upsetting the code. During one summer there were 30 additions made to the LEDA code, a good part of which was due to changes in lithology of the bedrock as the field work extended into new areas. The argument that a code becomes a "monstrosity" by continuous additions is true only if one considers variety in geology "monstrous". In order to comply with the fifth requirement, the arrangement of the headings in the physical layout of the list of codes should follow, in a general manner, the order of the input documents without making any unnecessary repetitions in the list. The numbers in paranthesis under the headings on the chart showing the LEDA code (Table 1) refer to the column number on a specific type-card. The last requirement, that the coded expressions should he printed separately from the field data sheets, has been touched upon in the foregoing discussion. At any rate, this requirement is self evident if duplications on the chart containing the coded expressions are to be avoided, or, if additions to the code are permitted, and if the term "other" is banned from the code. In the LEDA system, the chart containing the code is placed in a flipout folder attached to the front cover of the looseleaf binder used as field notebook (Fig. 6). COD~CATIONOF SlXA~nGV,APmC DATA The greatest merit of the LEDA system lies in the ease by which either simple or complex stratigraphic data may be codified. The flexibility of the system makes it possible to describe stratigraphic sections or parts of them, either in a grosso modo manner, or in as much detail as required. Furthermore, description of stratigraphic data can be accomplished without having to use more than the Least number of necessary data cards or without having to collect a large number of partially used data sheets. From a practical point of view. the LEDA system recognizes two types of stratigraphic units, simple and

OUTCROP TYPE (48) I--Natural exposure 2--Artificial cut

ST--Structures SS--Sedimentary structures SF--Structures-folds SJ--Structures-joints SC--Schistosity FA--Fabric

UN--UniI US--Unit with sub-unit CT-~outact Ll--l,ithology Sl~-Sedimenls FO--Fossils SP--Samples GS--Geochemical samples SM--Straligraphic measur.

OX--Oxydation PD---Patterned ground MM--Mass movement AL--Alluvium ER--Glacial erratics RE--Ice-rafted erratics GD--Glacier flow direction SR--Strialions

sc---Soit

PA--Aerial photo PCv--Ground photo GG-4]eneral geology IN--Interpretation BR--Bedrock VG--Vegetation

SL--Slope

SUBJECT (3-4) L(~--Location 0C-4)utcrop Tl~---Tolx~taphy

LOCATION---OUTCROP

BI)--Beach Ridge TO--Tombolo SP--Split LA--Lagoou SA--Active scarp

Cl.~irque VG--Glacial valley MF--Frontal moraine ML--Lateral moraine MM--Median moraine MG--Ground moraine MH--Hummocky moraine KA--Kame KT--Kame terrace ES---Esker DR--Drumlin

INTERPRETATION (62-63) BR--Bedrock BH--Bedrock hill EC--Escarpment SL--Slope TA--Talus AT--Rock avalanche LS---Landslide AF--Alluvial fan/cone CH--Channel VF--Fluvial valley 'l'E--Terrace

CONTROL BY 159) B--Bedrock D--Drift

TOPOGRAPHY TYPE (55) l--Flat 2--Undulating 3--Rough 4--Ridges 5---Kno~s & depressions 6--Dissected 7--Inclined plain g--Stair-like

I.fX?ATION IN UNIT (35 & 39) I--Outcrop sudace 2--Parallel to land surf. 3--Parafiel to bedding 4--Along contacts 5--Along fractures b--Along roots 7--Fractures & rools 8--Random 9---Everywhere A ~ n pebbles

INTENSITY (34 & 40) 0--None l--Weak 2--Medium 3--Strong

132) C--Concordant D---Discordant F--Faulted N--Non-determinable (33) ('--Concave upward V--Convex upward H--Horizontal I--Inclined R--Irregular

LOWER CONTACT (31) C--Covered G~radual N--Net

BED-FORM (30l l--Blanket 2--Talmlar/rectangular 3--Wedge/prism 4--Lens :5--Cone 6--Delta 7--Dike 8--Equidimensioual

ORIENTATION

A--,~lluvial L--Lacustrine M--Marine I--Littoral G--Glacial N--Ice-contact P--Pro-glacial R--Periglacial T--Till E--Eolian O-4)rganic

GLACIAL EROSION MARKS (24) GRAIN-SIZE CLASSES S--Striations Block >256 mm T--Striation with sense Cobble 64-256 nma N--Nail-headed striation Pebble ~64 mm G~3rooves Sand 0-05-4.0 mm M--Chattermarks Silt & Clay <0.05 mm N~Chattermarks w. sense F--Flutings GRAIN FORM (48, 5 I. 54, 57) R--Rock boss I--Spherical ] C--Crag & tail 2--Platy ~ rounded D--Drumlin/drumlinoid 3--Ehmgatc I 4--Spherical j PEBBLE ORIENTATION (24) 5--Platy ~ Sob-angular with subject"FA" 6--Elongate I A--Elongate 7--Spherical [ B--Flat & elongate g--Platy ] angular C--Flat 9--Elongate } COMPOSITION STRUCTURES (67--701 A--Massive ROCKS (18-19, etc.) B--Bedded GR~ranile C~ross-bedded G I-- Varieties D-Graded-bedded G2-E--Rhythmites etc. of granite F--Ripples--symelrical GP--Porphyry granite G--Ripples--assymetrical MG--Microgranite It--Dunes SY--Syenite I--Imbrication DR--Diorite J--4)riented pebbles GA~abbro K ~ I l l & fill DI--Diabase

145) B--In beds I~-Disseminated

ORGANIC MA'ITER CONTENT (44) F--Fossils (articulate) G--Fossil fragments H--Whole fossils L--Fossils & marl M--Marl P--Plant fragments T--Peat moss W--Wood

Table I. LEDA code. Slightly modified English translation of original French-language code. Layout of code is shown as used in field

Rl.--Rutile

MINERAI.S AND ROCK MODIFIERS (20-21, etc.) QZ--Quartz PG--Plagioclase PF--Potash feldspar BO--Biotite AB--Amphibole HN--Hornblende P×--Pyroxene HY--Hyperstbene OV--Olivine

UN--U nidentified

SM--l,aminated slate SA~?alcar. slate SX--l.amin. calcar, sla SW--Wealhered slate itF--Hornfels SK--Skarn SC--Schist GN-43neiss SO--Shickshock rocks ME--Melasedim.SO SI-- Varieties $2-- of SO etc.

AR--Argllite SL--Slate SB--Black slate SN--Green slate SR--Red slate

CA--Carbonate CL--Calcilutite CR--Calcarenite DO--Dolomite CH--Chert

Ml~Laminated mudstone MM--Indurated mudstoue SH--Shale

¢tl

e~

<

"m

t,o

AI,TITUDE MEASUREMENT (54) A--Altimeter from sealevel B--Altimeter from a BM F--Altimeter with second altimeter at base camp C--TOPo. map: 25' contours O--Topo. map: >t 50' contours E--Estimated H--Handlevel from fix. point R--Measure. tape/fixed point 'I--Transit from fixed point

POSITION (49) I--Valley ~)ttom 2--Vafiey side slope 3--1nlerfluve

3--Horizontal surface 4--Inclined surface 5--Hand auger 6--Mecbanical drill

B--At base of unit C--At top of unit

L~-Load cast M--Flute cast N~onvolution UNIT I)ESCRIPTION CHEMICAl. DEPOSITS (38) q)--Folds I--Mineralization P--Planar structures SEDIMENTS (20-2 I) 2--Cementation R--Joints B--Blocs _L.-Iron concretions S--Normal faults G~ravel 4-.4)rtstein T--Reverse faults S~Sand ~ a l c a r e o u s concr. O--Diapir I--Silt 6--Cafiche V--Ice-wedge C~'lay 7~xydes W--Fissile D--Diamicton 8--Clay film X--Partings O--Organic matter 9--H ydrothroilite Y--Blocky Z--Loose SUB-UNfr ARRANGEMENT COLOR (41-42) I~ompact (22) V--Variegated 2--Striated pebbles I--Inter-bedded B--Brown ~-Fractured pebbles 2--Inter-fingered G--Grey INTENSITY 4--Open-box structure 3--1nter-laminaled L--Black (43) 4--Thin bed N-if;teen I--Pale INTERPRETATION (71-7:t) ~--Inclusion O--Olive 2--Medium B--Bedrock g-Dyke P--Pink 3--1Yark S--Saprolite 7--Wedge R--Red C--Colluvial g--At top of unit U--Blue V--Mass movement 9--At base of unit W--White Y--Yellow F--Fluvial

Sl--lnactive scarp DU--Dunes

BR--Breccia CG-~.-'onglomerat e CC--Calcar. conglom. CF--Fossifif. conglom. AK--Arkose SS--Sandstone SF--Sandst. fine-grained SY--York River sandst. QZ--Ouartzite GW~reywackee SI--Siltstone ST--Calcar. siltstone MD--Mtuistone M C ~ a l c a r . mudstone

RH--Rhyolite FE--Felsite AD--Andesite BA--Basalt BP--Porphyry basalt

AN--Anorthosite PE--Peridotite AM--Amphibofite PY--Pyroxenite

FO--Fossiliferous GA~Granitic LA--l~aminated MT--Metamorphosed SR--Speckled red GP--Of Gasp6

P'l'--Pyrite CP--Chalcopyrite AT--Arsenopyrite PY--Pyrrhotipe HM--Hematite MG--Magnetite IM--Ilmenite Ml,--Malachite

SN--Sphere SP--Serpentine ZC--Zircon EP--Epidote GR~Garnet KN--Kyanite SE--Sericite CC--Calcite AG--Agate

o~

o

g

> >

r-

274

PETERP. DAVIDand JACQUESLEBUIS

composite. Whereas, simple units are those which are formed by homogenous lithologies (Fig. 7, units 01 and 04), composite units are associations of several lithologies (Fig. 7, units 02 and 03). Furthermore, the LEDA system uses a trilevel hierarchy of stratigraphic units according to the subdivision of composite units into subunits. Accordingly, there are first-order units that may be either simple or composite. The latter are formed by second-order units, also referred to as subunits, which in turn may be

either simple or composite. Finally, composite secondorder units are formed by third-order units, also called sub-subunits, which are all of the simple type. The lithologic associations in a composite unit may take the form of a series of alternating beds of two or more lithologies (Fig. 7, unit 02) where each lithology represents a second-order unit, either simple or composite in type. In a more complex association, alternating beds of a composite unit may be cut by a dike which in itself may be

i-Dl~ IG~ I-119121i7~

STATION

CARDS FOR DESCRIPTION ,'~FUNI T

CARDScOP ORIENTATION

CARDS ~OR COMPOSITION

CARDSFOR STRAT!GRAPNIC UEASUqEMENT

UNITS [

01

y

/

y

l--.

/

0 . . . . 201

~

M3UNIT Ol MENTARYt

F

~ -

I#N~T 02 O0

4

~

I

-,~1

lo; t , - 20[

C•O

[

~ g

. . . . . . . .

t

02

/ 20

//

./

-

STRATIGRAPNICI IMEASUREMENTI

UNIT 02 20

iCOMMENTARYI

. . . . .

~o[-:~

~NIT 02 10

P_7~EXPOSED t

{-

20

NIT ?3 O0

/,

COVERED

COMMENTARYI

E~Q@ NTACT [ BESCING [ I i

,o[_: I

L

03

: :/://- -I

,: O';TAC"

Lq:r 03 i'

i _NiT 03 2r)[ J

2~5--!

....3

o

~ %

04

~ -

J

-L

STRATIGRAPNIC MEASUREMENT

i UNIT 0 3 31 I

---2;-DIAGRAMS 1 POLAROID

PHOTOS

Figure7. Examplefor codificationof hypotheticalgeologicalsection.

LEDA:.# flexiblecodificationsystem for computer-based filesof geologicalfielddata

a composite second-order unit (Fig. 7, unit 03) containing simple third-order units. The LEDA system employs the second type-card as the core for the description of stratigraphic units (Fig. 2). This card contains all those parameters that describe the singly occurring properties of a specific stratigraphic unit, for example thickness, bedform, etc. On this type-card, the number identifying a unit is placed in columns 3--4. If the unit which is being described is a simple first-order unit. columns 14-15 are left blank. These latter columns are used in the identification of subunits. In the situation of a composite first-order unit, it may be necessary to describe the unit as a whole in order to give its total thickness or to indicate the nature of its lower contact, or of some other parameters. For this purpose, however, only those descriptive parameters are needed for which the base of the squares are marked by a heavy line on the type-card. If a composite unit is described as a whole, columns 14-15 have zeros marked in them and if detailed stratigraphic measurements follow using typecard No. 6, column 61 carries the symbol "S". In the situation of a composite unit involving a simple relationship between two subunits, such as. a bed containing a single inclusion or is cut by a dike. it may not be always necessary to describe the composite unit as a whole. In this situation, the major component of the unit is described first as a first-order unit followed by the description of the inclusion or dike as a second-order unit. In the situation of composite second-order units, it is sufficient to describe first the major component of the subunit as a second-order unit .and then the minor component as a third-order unit. Column 22 on the second type-card is used to describe the relationship of a second- or third-order unit to the enclosing unit or to the other subunit of the same composite unit. In columns 16-17 the percent distribution of the subunit is given in relation to the composite unit as a whole. Columns 18--19 contain the number of beds forming the subunit in question. Second-order units are numbered from 1 to 9 in column 14 and third-order units are numbered the same manner in column 15. Therefore, each composite first-order unit may have a maximum of nine second-order units, each of which may have a maximum of nine third-order units. Considering that at a particular station as many as 99 first-order units may be described, if in a hypothetical geological section there were 99 composite first-order units, each with nine composite second-order units, each of which in turn contained nine third-order units, a total of 8019 simple third-order units could be described. Furthermore, if it became necessary to increase this number, it could be accomplished by simply increasing the station number by one and establishing a double station for the same location. However, experience indicates that there are rarely more than 10-15 first-order units at a station and the number of second- or third-order units within the same composite unit never exceeds three or four. In the example shown in Fig. 7 and Table 2. a hypothetical geological section comprising four first-order units is described. In that example the selection of first-order units is obvious except perhaps for unit 04

275

which is lithologically identical to subunit 0320. However, unit 04 is different from subunit 0320 in that it is not cut by the dike contained in unit 03. If the dike were to extend into unit 04, the latter would simply be another subunit 0320. FIELD PROCEDURES

Field procedures connected to the use of the LEDA codification system are divided into the following categories: (1) Training of geologists who are unfamiliar with the LEDA system; (2) Verification of station files at the end of each week during the entire field season; (3) Discussions which are held once a week during the field season on problems arising from the application of the LEDA system. The introduction of the LEDA codification system to field mapping brings about a change in the preparation of geological field notes. To facilitate this change, and to ensure rapid acquisition of this new method of note taking, geologists who are unfamiliar with the LEDA system undergo a three- to four-day training at the beginning of each field season while the "field camp" is being set up. The first day of this training is spent in the field office familiarizing with the philosophy and the structure of the system and with the code and the data cards. Following that a few days are spent in the field to acquire the basic procedures in the practical application of the system. Several locations which provide a variety in local geology are visited. At each station the geologists describe their observations using the data cards. After the completion of one station, the data cards of the individual geologists are compared and any error that may occur in the application of the type-cards is corrected on the site. During two days of field training most aspects of the local geology are examined and the geologists are ready to proceed with their individual field work. During the entire season each geologist daily completes the data file of all the stations visited during that day and places his notes in a document file designated for him. Because field notes are in single copy they may never be taken back to the field. At the end of each week a preliminary validation of the week's station files is made by the geologists. This validation is made in two steps as follows: A--Firstly, the data file of each station is verified to see (I)----that all data sheets of the same station have identical station code; (2)--that there are no doubly used station numbers and stations are numbered consecutively; and (3)--that the cards of one station are numbered consecutively in the correct order. B--Secondly, the field sheets of all the station files of that week are grouped acccording to type and the individual type-cards are verified to see (4)--that only "legal" codes are used; and (5)--that all the columns required for a specific problem are correctly filled in. At the end of each week, or whenever necessay, all the

PETER P. DAVID and JACQUES LEBCIS

276

Table 2. Description of data cards used in codification of hyl~thetical geological section shown in Fig. 7 2ard order

3a:'i z}-~e

nu-nber

n~zoer

1

l

[lentlfica~ion zf 20/ifie~ inforr,xti:n

D~lcrip
2

3escri~zion of unit ,71

3

2

L

5

3or~en~aryon the sediment~ of unit O!

5-7

3

Li~nological composition of pebble-sized roc&-gar:icles

L

:<~asuremcnts of a~ti~ude of lon~ axi~ of pebbled in unit CI

in unit 3i

5 c & c r i ~ i o n ~f composite unl~ 02, a~ a whole

16 il

2

~escrip~i~n of Dub-unit 0210

12

3

/ounz, by ty~es, ~f fossils in sub-unit O~!O

15

5

3or~entary on the fossils in sub-unit 0216

2

Description of sub-unit ~223

5

Commentary on sub-uni~ 5220, ~s such ~etaiiei zea~uremen:s of thickness of each consecutive hea

16

of Dub-units 32!0 ana 3220, from top to bottcm

17

2

Recording of thickness of unexposed portion of the zec~ion ~.is card contains Cols.


!-2

3a~'d arder n ~ b e r

3-4

Code for outcrop (OC)

16-19 T1

Vertical extent of covered Fortion ~f ~ ' = ~ ST~bol "Y" indic&zing that the ouezrop iz covered.

18

2

~escription of composite unit 63, as a whole

19

5

Com~en:a~/ on unit S3, ~

such

5:eas/remen~ of gttlrude Df lower 2on~ac~ of ~ni~ 63

2O 2!

4

Me~surementsof atzizuae of stratification in ~.it 03

22

2

Description of suo-,~nit ~310

k

:
2

Description of sub-suh-~ni~ O311 Description of sub-unit ;3320

25

26

Measarements of ant=tude of stratification in sub-uniz 032]

27

2

~eseription of sus-unit 0330

28

5

$ o ~ e n ~ a r y on %he sediments of sub-unit 0330

29

2

Description of sub-sub-unit 0331

i

Measurements of attitude of sub-~ub-uniz 0331

5

$oz~enta~/ on ~he ~ttltude of sub-sub-unit 6~31 ~etaiied measure=en~ of thickness of each consecutive be!

32

of ~ub-uniz 032C ~na ~uo-unit 3330, from top ~O bottom

33

2

2e~crip~ion of unit O~ Preparation of diagy~m and posting of polaroi~ photos on three field shee~s

geologists meet to discuss and resolve any problems that may have risen during the week in the application of the codification system. At the same time the code is updated by introducing the new coded expressions that may have been established during the preceding week. During these meetings periodic verifications of the data files of the geologists also are made by the party chief to ensure an errorless data file by the end of the summer.

OFFICE PROCEDU~-~

At the end of the field season the field data files are taken back to the head office where the computer cards are punched. The data. then, are transferred to a magnetic tape and every item on every type-card is verified against a master code which also is updated at the end of each field season. Experience suggests that most errors in the punching of the computer cards occur due to misreading

LEDA:A flexiblecodificationsystemfor computer-basedfilesof geologicalfielddata of symbols. However, this error occurs generally on less than 5 percent of the data cards and it can be readily corrected. Other errors in the data file are due to the use of "illegal" code names, inspite of the rigorous validation during the field season. Although this error may not be readily corrected, fortunately, it occurs on less than 1 percent of the data cards. OUTPUTOOCUMENTS At the present time, only a limited number of output documents are produced by the computer and only limited exploitation of the data is carried out with the aid of the computer. There is, however, an unpublished document not yet available for circulation, which contains instructions addressed to the users of the LEDA data bank outlining the procedures to follow in obtaining specific output documents. These documents which have already been used in the preparation of geological reports are as follows: (1) Location map used in the verification of UTM coordinates assigned to the stations: (2) Sample location map listing all the samples collected at the various field stations; (3) Surficial deposit map showing the uppermost unit observed at each station; (4) Drift thickness map giving definite or minimum thickness values of the surficial deposits at all locations; (5) Glacier flow direction map showing the location, the orientation, and the sense, if available, of movement of glaciers according to all the available glacier flow indicators; (6) Map showing the stratigraphic diagram of selected geological sections; (7) Map showing the percent distribution of erratic boulder types. The computer production of a number of other maps and diagrams is presently in the preparatory stage. These and other output documents proposed in the statistical evaluation of field data, however, awaits the collection of more data from a larger area. Further developments toward a more efficient exploitation of the data await the installation of instruments for a geologist-computer interactive manipulation of the data. GEOLOGISTS'APPRECIATIONOF TIlELEDASYSTEM This paper would not be complete without reporting the commentaries made by geologists on the LEDA system. The LEDA system was introduced in actual mapping during the summer of 1971 when three geologists, including the authors, employed it for the first time. The following summers fifteen other geologists were introduced to the system as the system was adopted in other Quaternary maphing projects of the Quebec Department of Natural Resources. The reaction of these geologists to the use of the system was always favorable and their suggestions led to considerable improvements in the system. The LEDA system was equally well received by the members of the Working Committee on Geological Field Data of the Canadian NACRGS Subcommittee on Computer Application, who considered the system to be a

277

great step forward in the codification of stratigraphic and morphologic field data. It was this backing that led to the writing of this paper. SUMMARYANDCONCLUSIONS The use of the computer as an aid in field mapping is a necessity in a project that lasts for several years and involves a number of geologists. The LEDA system which was developed for the Gasp8 Project of the Quebec Department of Natural Resources, to map Quaternary deposits, is user oriented as well as machine and geology oriented. Using the LEDA codification system, both morphologic and stratigraphic data may be collected with ease and without accumulating large quantities of partially used data sheets or without having to, uselessly, fill in too many data squares. The described qualities of the LEDA system are achieved through the selection of distinct types of data as units of data collection, which are reported on six type-cards extending the length of an 80-column punchcard. The type-cards are (1) Location, (2) Stratigraphic Unit, (3) Composition, (4) Orientation, (5) Commentary, and (6) Stratigraphic Measurement. The type-cards are reproduced on pocket-size field data sheets in the following order: (l) one card for location and one card for the description of a stratigraphic unit; (2) two cards for the description of stratigraphic units; (3) three cards for composition or orientation data; (4) four cards for commentary; and (5) two cards for stratigraphic measurements. There is an additional field sheet provided for diagrams and polaroid photographs, the information on which is not codifiable. The field sheets are printed in green and the number of copies of a type-card on a particular field sheet depends entirely on the size of the type-card with the data squares left large enough for convenient use. In the field office, the used field sheets are arranged according to station number in a standard, office-type looseleaf binder. The data file of an observation station consists of all the cards used at that station. The individual cards of a station are linked to one another by the station code consisting of four parameters which are the codes of the geologist and of the region followed by the station number and the year of observation, in that order. The cards of a station file are numbered consecutively from one. The data from the station files of all the geologists working in the Gasp6 Project are transferred to magnetic tape that forms the data bank of the project. For the description of an observation station, only one copy of the location card is used but the other type-cards are used in such order and quantities as required by the type and length of the information sought. The LEDA code used in the Gaspd Project is simple inasmuch as it contains coded expressions that are modified abbreviations of "common" usage. The coded expressions are printed on a chart separately from the input documents for flexibility and to make updating of the code feasible. The chart containing the code is placed in a flipout folder that is attached to the front cover of the looseleaf binder used in the field. Although several types of output documents have been produced by the computer from the data collected since the beginning of the project, a deeper and more extensive

278

PETER P. DAVIDand JACQUESLEBUIS

exploitation of the data bank awaits the accumulation of more data and the development of new, project-oriented computer programs. The greatest contribution of the LEDA system made to the problem of geological field data codification is its basic philosophy of using data types as units of data collection. This philosophy may be employed in developing equally flexibile codification systems for other projects in any branch of geology. Unlike the LEDA system, the length of each data unit in a new system may be different from one another and need not necessarily be equal to the length of an 80-column computer card. The LEDA system of codification of field data is not considered to have reached its final form. Further developments are expected to occur as more sophisticated computer hardware becomes available. There will be less and less emphasis on the length of data units giving a greater flexibility to the system. In the authors' opinion, however, the LEDA system in its present form has proved itself to be worthy of publicity as it has improved the methods of codification of complex stratigraphic and morphologic data.

Acknowledgments--The Quebec Department of Natural Resources supported most of the expenses occurred in developing the LEDA system including those that arose from the use of the Quebec Government's Centre de Traitement Electronique des Donn~es. Part of the expenses, which occurred to the senior author, was defrayed from National Research Council of Canada Grant No. A-2610. The senior author, as member of the Working Committee on Geological Field Data Codificationof the NACRGS Subcommittee on Computer Applications, acquired practical information, advice, and suggestion in system development from all members of the Working Committee, during the evaluation and discussion of other field data systems presented at the annual meetings of the Committee. The suggestions made by those geologists who actually employed the LEDA system in field mapping have helped improve the system. To all these persons and organizations both authors express their deep gratitude. The diagrams, except Fig. 2. were prepared by Michel Demidoff. Universit} of Montreal; Fig. 2 was drafted at the QDNR in Quebec City.

REFERENCES

Berner. H., Ekstrrm, T., Lilljequist, R., Staphansson, O., and Wikstrrm, A., 197l, Data storage and processing in geological mapping. I Field data sheet: Geol. Fbren. Stockholm Fbrh.. v, 93, pt. 1, no. 544. p. 85-101. Brisbin, W. C.. and Ediger, N. M., eds., 1%7, A national system for storage and retrieval of geological data in Canada: Natl. Advisory Comm. Research Geol. Sciences, Geol. Survey Canada Publ., 175 p. Burk, C. F., Jr., 1966, Coding of geological names and terms, in Interim report of the committee on storage and retrieval of geologicaldata in Canada: Geol. Survey Canada Paper 66-43, p. 29-34 and 95. Burns, K. L., Marshall, B., and Gee. R. D., 1969, Computerassisted geological mapping: Austr. Inst, Mining Metallurgy Proc., no. 232, p. 41-47. David, P. P., and Lebius, J., 1973, A flexible computer-based system for the storage of geological field data (abst.): Geol. Soc. America, Abst. with Programs, v. 5, no. 2, p. 154-155. and no. 7, p. 875. Haugh, I, Brisbin, W. C., and Turek, A. A., 1%7, A computeroriented field sheet for structural data: Can. Jour. Earth Sci., v. 4, no. 4. p. 657-662. Hru~ka. J., and Burk. C. F. Jr.. 1971, Computer-based storage and retrieval of geosciences information: Geol. Survey Canada Paper 71--40, 52 p. Hubaux, A., ed., 1972, Geological data files: a survey of international activity: COGEODATA Rept., CODATA Bull., no. 8, 30 p. Hutchison, W. W., and Roddick, J. A., 1968, Recording geologic field data for machine retrieval and processing: Western Miner (February 1968), v. 41, p. 39-43. Lebuis, J., and David, P. P.. 1973, Syst~me LEDA: Utilisation des fiches standardis~es pour enregistrer les donnges g~ologiques des d~pbts quaternalres: Quebec Dept. Natural Resources Open File Rept. GM-27623, 31 p. Sharma, K. N. M., Laurin. A. F.. and Wynne-Edwards, H. R., 1972, Computer-based field-data system for the Grenville Project, Quebec: Quebec Dept. Natural Resources Publ.. no. S-141. 146 p. Turner, W. R., 1%7, A computer-oriented groundwater information storage and retrieval system: Ground Water, v. 5. no. 4. p. 30-37. Wynne-Edwards, H. R., Laurin, A. F., Sharma. K. N. M., Nandi, A., Kehlenbeck, M, M,, and Franconi, A., 1971, Computerized geological mapping in the Grenville Province. Quebec: Can. Jour. Earth Sci., v. 7, no. 6, p. 1357-1373.