1002 Subsurface Geologic Methods 



North-South Sectional Grid — North-South sectional unit-areas are 

 oriented so that the short or 20" dimension of the area is in a north-south 

 direction, and the north and south borders of the sectional rectangles co- 

 incide with the north and south borders of the plan rectangles. The eleva- 

 tions of the top and bottom of the rectangle are divisible by 2,000 (fig. 

 532) . 



Diagonal Sectional Grid — These are laid out in a manner similar to 

 the note-sheet diagonal grid. The short or 20" dimension of the office-map 

 rectangle is vertical and the elevations of the top and bottom are evenly 

 divisible by 1,000. 



Specifications of Data and Map Sheets 



All essential field and office data and map sheets used may be printed 

 from four plates. Survey sheets, field and underground note sheets, and 

 ore-reserve listing and classification sheets are printed on ledger paper. 

 Assay-record sheets are the same as the field-note sheets, but the printing 

 is on tracing paper instead of ledger paper. Office geological map sheets 

 are printed on cloth. Sheets for the representation of metallization, ore- 

 reserve blocks, geochemical or biochemical data, vegetation, or geophysi- 

 cal data are printed from the same plate as that used for the office geo- 

 logical maps and are prepared on clear plastic material. 



Survey Sheets — The survey sheet is dual purpose in that it is used 

 both as a field recording sheet and office survey ledger sheet. The printing 

 is on 32-pound ledger paper twice the size of a letter sheet, so that, when 

 folded at the center, it may be placed in either a letter-size, spring-back 

 field book (of identical type to that used for geology field-note sheets), 

 or in an office post binder. When thus folded each sheet makes two op- 

 positely facing pages. Data collected in the field and all preliminary 

 calculations are entered on the left-hand page. Latitude, departure, and 

 elevation data are entered on the right-hand page. To insure permanency, 

 it is desirable to retrace all field data in India ink. The horizontal lines 

 on the sheet are of such spacing that all the calculations may be type- 

 written for clarity in reading. A key-hole punching along the folded edge 

 permits removal of any sheet without taking the binder apart or removing 

 the top sheets. In the upper right-hand corner is an entry space for co- 

 ordinate indexing; this indexing indicates survey data source by 400'x500' 

 unit areas (fig. 528). 



Field- and Underground-Map Sheets — A letter-size field-note sheet 

 with a 1" grid covering an 8" x 10" map area has been found to promote 

 the maximum efficiency in mapping and filing. The coordinate grid is 

 printed in black on 28-pound ledger paper. On the north 8" border of 

 the map grid is a 1" margin, which fits into the binder of a spring-back 

 field book; on the east border is a |" margin in which location, elevation, 

 and filing data are'entered in appropriate places provided for such infor- 

 mation. The south and west margins of the sheet are kept to a minimum 



