collecting field data for a bedrock geologic map
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Collecting Field Data for a Bedrock Geologic Map. GEOL 3000. Preparation. Establish Objectives Why are you mapping?

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Presentation Transcript
  • Establish Objectives
  • Why are you mapping?
  • - previously unmapped or inadequately mapped area, adding additional level of detail to previously mapped area, trying to solve a specific geologic problem, evaluating economic potential of an area, ...
  • What are you mapping?
  • - quadrangle, county, geological unit of interest, area of mineralization potential
  • What scale will your final map be?
  • determines the scale of your field map (always map at more detail than the final map) and the coverage of outcrop you acquire
  • Who will be mapping and where?
  • - balance expertise, safety, coverage of field parties
  • Research Previous Mapping and Useful Data
  • Review published and unpublished maps (e.g. thesis maps, exploration company maps) and related reports or scientific articles
  • Seek out original field maps and notes if available
  • Investigate any handsamples and thin sections from previous studies
  • Investigate any drill core or core logs in your field area
gear for northwoods field work
Gear for Northwoods Field Work

I’m gonna find me some outcrop today!

  • Clothing
  • long sleeve collared shirt
  • loose-fitting, light but rugged long pants
  • inexpensive rain pants and jacket
  • field hat
  • rugged water-proof boots
  • field vest &/or back pack
  • Geologic Equipment
  • field map and map board
  • notebook (water-resistant)
  • Brunton AND orienteering compasses
  • hand lens, magnet, acid bottle
  • hammer (and chisel)
  • pencils (reg. & colored)
  • sample bags and permanent markers
  • Other
  • - insect repellent and more insect repellent
  • - water (2 liters)
  • - field lunch (gorp, fruit, jerky)
the field map
The Field Map
  • Topographic Base
    • ~ page size
    • scale greater than final map scale (e.g. for 1:24,000 map, field map at 1:12,000 or 1:10,000)
    • add UTM grid for ease of locating
    • use waterproof paper or laminate
    • overlay with sheet of mylar
  • Outcrops
    • label station ID that matches notebook and sample ID
    • discriminate rock type with colored pencil
    • note sample locations
    • draw strike and dip of measured structures
  • Other Features
    • route taken
    • new roads or trails
    • possible geologic contacts or faults
    • other things of note



Field Map of part of Tofte 7.5’ quadrangle

finding outcrop
Finding Outcrop

Start here


S80ºW or 260º

~700’ or 1120m

~140 paces

massive gabbro

recording outcrop information
Recording Outcrop Information
  • Scout around the outcrop:
  • Make careful observations of rock type(s),
  • textures, structures; peel moss if necessary
  • Measure orientation of structures/contacts
  • Hammer off a piece of rock for a closer look
  • Take a sample if necessary or important
  • Take a picture if photogenic exposure
  • Find a comfortable spot on the outcrop; Apply bugspray if necessary; pull out notebook and map; check GPS location
  • On the field map, mark:
  • Route to outcrop location
  • Area of outcrop - ACCURATELY (in color?)
  • Station ID# label
  • Strike and dip symbols of structures
  • Locations of samples taken
  • In the notebook, record:
  • Station ID#, UTM coordinates
  • Extent, visibility, & type of outcrop
  • Rock description- mineralogy, texture, structure
  • Structure measurements
  • Photographs taken
  • Samples descriptions
finding more outcrop
Finding More Outcrop

Start here




S60ºW or 250º

~1100’ or1750m

~220 paces


S75ºW or 255º

~750’ or1200m

~150 paces

S5ºW or 185º

~950’ or1520m

~190 paces

massive gabbro



layered gabbro