Collecting Field Data for a Collecting Field Data for a

Bedrock Geologic MapBedrock Geologic Map

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 potentialWhat 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 acquireWho will be mapping and where?- balance expertise, safety, coverage of field parties

Research Previous Mapping and Useful DataReview published and unpublished maps (e.g. thesis maps, exploration company maps) and related reports or scientific articlesSeek out original field maps and notes if available Investigate any handsamples and thin sections from previous studiesInvestigate any drill core or core logs in your field area

PreparationPreparation

Gear for Northwoods Field Gear for Northwoods Field WorkWorkClothing

- long sleeve collared shirt - loose-fitting, light but rugged long pants- inexpensive rain pants and jacket- field hat- watch- rugged water-proof boots- field vest &/or backpackGeologic 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 markersOther - insect repellent and more insect repellent-water (2 liters)- first aid kit, matches, emergency blanket-field lunch (gorp, fruit, jerky)- cell phone, 2-way radio

I’m gonna find I’m gonna find me some me some outcrop today!outcrop today!

The Field MapThe Field MapTopographic/LiDARBase

-~ 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

BE ACCURATEBE ACCURATEBE NEAT!BE NEAT!

Finding Outcrop Finding Outcrop

Start here Start here

S80ºW or 260ºS80ºW or 260º~700’ or 1120m~700’ or 1120m~140 paces~140 paces

Recording Recording Outcrop Outcrop

InformationInformation• 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; 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 OutcropFinding More Outcrop

Start here Start here

S60ºW or 250ºS60ºW or 250º~1100’ or1750m~1100’ or1750m~220 paces~220 paces

M486

S75ºW or 255ºS75ºW or 255º~750’ or1200m~750’ or1200m~150 paces~150 paces

M48725o

S5ºW or 185ºS5ºW or 185º~950’ or1520m~950’ or1520m~190 paces~190 paces

M488S--S--

No OC

Using Your Orienteering Using Your Orienteering CompassCompass

Line up edge of compass with route to be taken

North

Using Your Orienteering Using Your Orienteering CompassCompass

Rotate dial to align interior lines N-S

Using Your Orienteering Using Your Orienteering CompassCompass

Your bearing will be indicated by the azimuth at the white tick mark

Using Your Orienteering Using Your Orienteering CompassCompass

Measure the distance and determine the number of paces you will need to walk

Using Your Orienteering Using Your Orienteering CompassCompass

Point compass away from your body

Turn your body until the red needle lines up with the “red in the shed”

Head in the direction of the long axis of the compass