USGS

The Venus Geologic Mappers' Handbook


Appendix D: Format Instructions for Text and Explanations


Headings and Head Notes

Within the description of map units and text, headings are divided into orders--major headings (Introduction, Physiographic Setting, Stratigrphy, Structural History, References Cited, Description of Map Units, etc.) are first-order centered headings and further subdivisions are second order and third order.

Type, centered:

FIRST-ORDER HEADINGS ALL CAPS AND BOLD

SECOND-ORDER HEADINGS ALL CAPS BUT NOT BOLD

Third-order headings initial cap and lowercase and not bold

[Headnotes under centered headings are enclosed in square brackets, extend across entire column width (except centered if only one or two lines long), are not indented, and have no final period]

Map Units and Symbols in DOMU

Type all map unit names at first mention in lowercase and bold; follow by two hyphens. Begin the descriptive material with a capital letter. Do not put a period at the end of the last line of the description of each unit and do not divide the description into paragraphs. Start the name of each first-rank map unit about ten spaces to the right of the first letter of the map unit symbol.

First rank--"Left margin" 
  Second rank--Indent two spaces 
    Third rank--Indent four spaces 
        Fourth rank--Indent eight spaces 

All overruns of all ranks--Indent six spaces if more than two ranks are used, four spaces for two ranks, and two spaces for one rank.

Use the same format for symbols (such as contact, fault, etc.) as for map units. On a geologic map, such symbols are explained following the description of map units and a break of about four blank lines but no separate heading.

Example of map explanation. The sample explanation below demonstrates the application of the above rules (text modified from a Mars map being prepared by S.L. Rotto and K.L. Tanaka). It is made much narrower than an actual explanation to allow room for marginal notes. Note that it is followed by a corresponding correlation chart.


DESCRIPTION OF MAP UNITS

[Map units distinguished and interpreted on basis of morphology, texture, albedo, and stratigraphic position. Although most map units are rock materials, some channel floors are also considered units in order to highlight erosional events that formed them]

LOWLAND TERRAIN MATERIALS

Chryse assemblage

      Basin materials--Form lowland
            plains below mouths of 
            outflow channels; 
            interpreted to consist of 
            sediments derived from 
            outflow channels and 
            possibly volcanic and 
            eolian deposits. Contacts 
            between basin units 
            generally gradational
cr      Subdued ridged unit--Plains
            marked by subdued 
            wrinkle ridges and cut by 
            small outflow channels. 
            Interpretation: Ridged 
            plains material partly 
            resurfaced by outflow 
            erosion and deposition
cc      Complex unit--Characterized by 
            one or more of the 
            following: (1) hummocky 
            topography; (2) small knobs
            (some superposed on 
            mesas); (3) sinuous 
            depressions about 10 km 
            wide and tens of 
            kilometers long; (4) 
            sinuous ridges less than 
            1 km wide, some of which 
            are medial in sinuous 
            depressions or connect 
            knobs; (5) narrow, 
            curvilinear, northeast-
            trending grooves; and (6) 
            several mostly buried 
            crater rims. Unit 
            gradational with smooth 
            and grooved basin 
            materials. Interpretation:
            Relatively thick lacustrine 
            deposits from most recent 
            flooding. Various features 
            result of fluvial or glacial 
            processes (or both) and 
            compaction of sediments
cu      Undivided unit--Material of 
            Chryse assemblage 
            occurring where image 
            resolution does not permit 
            discrimination of 
            individual units
      Knobby materials--Interpreted as 
            basin sediments and 
            perhaps lava flows that 
            embay knobs of older 
            degraded plateau material 
ck      Younger knobby material--
            Forms knobby plains. Cut 
            by lowermost Ares Vallis; 
            gradational with older 
            knobby material; embays 
            mouth of Mawrth Vallis
cku     Upper unit--Found only in 
            upper reaches of Kasei 
            Valles in southwest 
            quadrant of map area

ckl     Lower unit--Locally underlies 
            upper unit but most 
            exposures found in lower 
            reaches of Kasei Valles in 
            north-central part of map 
            area

cko     Older knobby material--Closely 
            spaced groups of knobs on
            high, undulatory plains 
            along highland-lowland 
            boundary (fig. 1). Typical
            exposures at lat 14.4_N., 
            long 172_ (Viking frame 
            639A12)

HIGHLAND TERRAIN MATERIALS

Tharsis assemblage

[Lava flows originating in Tharsis region]
      Tharsis Montes Formation--
            Easternmost flows of large 
            shields of Tharsis Montes; 
            exposed in western part of 
            map area
t5      Member 5--Marked by elongate, 
            high-albedo flow lobes 
            with distinct margins; 
            craters rare. Correlative
            with member 3 of Tharsis 
            Montes Formation as 
            mapped by Doakes(1983)

Sample Correlation Chart

The following correlation chart corresponds to the above description of map units:




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