Collecting Field Data for Collecting Field Data for aa

Bedrock Geologic MapBedrock Geologic Map

GEOL GEOL 30003000

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Research Previous Mapping and Useful DataReview published and unpublished maps (e.g. thesis maps, exploration company maps) and related reports or scientific articlesSeek out original field maps and notes if available Investigate any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 WorkWork

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 packGeologic 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)- field lunch (gorp, fruit, jerky)

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

North Country ExposuresNorth Country Exposures

The Field MapThe Field MapTopographic 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

BE ACCURATEBE ACCURATEBE NEAT!BE NEAT!

Finding OutcropFinding Outcrop

Start here Start here

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

M486

massive gabbro

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; 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 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

massive gabbro

layered gabbro20o

Compiling Field Data In Compiling Field Data In GIS GIS