Transcript Generalized Geologic History of the North American

Use us – we are here to help!
Find us in the field. Ask us to traverse with you.
Come to office hours
• Alison Duvall
• Camille Collett
• John Fullmer
• Shane Schoepfer
Mechanics
• Unless otherwise announced, office hours
~7:30-9:00 pm, Either in the classroom (Main
hall 209 or in the grass outside of the dorms).
• Short lectures some evenings
• Most assignments due 9 pm. Don’t be late!
• Washer and dryer in Centennial 200
• Refrigerators (still working on individual minis
– using communal for now)
Rules
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Be respectful of others
Don’t drink and drive
Be ready to go at 8 am
Rendezvous on time at the end of the day
• Be nice / attitude goes a long way in the
field!
• Work together. Do your own work
• Vehicles
• Gear
• Schedule
Be nice
• 10 pm quiet time
– If you need to be loud late, go downtown
• Avoid friction with other groups
• Keep halls and sinks clean
– No breaking rocks in the rooms
– Take trash out
• We are guests here. You are conspicuous
ambassadors of UW. Think about the image
you project!
Work together. Do your own work
• In the field, parties of 2 or 3
– Do not work in groups of 4 or more!
– This is for safety and for learning better
– Argue with your colleagues!
– Mark your own map. Take your own notes.
• In the office, work alone. Only discuss in
general terms
• Questions? Ask us!
Vehicles
• You can still get driver-certified:
– uw.edu/facilities/transportation/fleetservices/
resources/training.php
• Keep vehicles clean
– Empty trash daily
– Windows, headlights, and tail lights clean at all times
• Keys
– In the field: put behind gas-cap lid
– At the dorms: with one of the TAs unless you are using a vehicle.
• Keep fuel tank > ¼ full. Fill/refresh water jug as needed
• After-hours use
– Try to take others with you (don’t shop alone; DON’T Don’t park
in front of bar or liquor store)
– On days off, may go as far as Butte or Pioneer Mtns.
– Leave plan (driver, passenger names, destination, return time)
with me or Tas for trips of more than ~10 miles
Gear
• Bruntons / Silvas
• Radios
– For safety, to ask for staff help
– No chit-chat on main frequency: go to another
channel
– Don’t talk geology on the air
• Field maps/map board
• Sand paper (for pencil sharpening if not
mechanical)
• Rock Hammer
• Pencils/pens/eraser
Daily routine
• Assemble ready to go by 8 am
• Back here by 5:30 pm
• Make arrangements for pickup time and place
before you leave the vehicle in the morning
– Generally we will do this outside the dorm before
we go
• Office hours 7:30p – 9:00p unless otherwise
noted – we often meet in the evening for a
lecture or map check
• My room is Davis 111 – please don’t hesitate
to come talk to me if you need something.
Pacific Plate
motion
Generalized
Geologic History of
the North American
Cordillera
Belt Supergroup (~1.6 – 1.2 Ga)
• Mesoproterozoic
basin
• ~ 1/3 of Montana
• ~ 18 km thick!!
• Beautifully
preserved sed
structures
Belt Supergroup Rocks
~240 Ma
Permian
Late Paleozoic
and early
Mesozoic:
region of eastern
Cordillera was
stable and lowrelief: shallow
sea and coastal
plain. Possible
island arcs and
orogeny off to
west.
images by
Ron Blakey,
Northern Arizona University
~160 Ma
LateJurassic
Beginning of
Nevadan
orogeny
(collision of
microplates?).
Growing westCordilleran
mountain belt
weights edge of
craton; craton
subsides to
create fore-deep
images by
Ron Blakey,
Northern Arizona University
85 Ma
mid Late
Cretaceous
Zenith of
Cordilleran
(Sevier)
orogeny.
Collision/subduc
tion has built an
extensive
mountain belt,
bordered to east
by Interior
Seaway
images by
Ron Blakey,
Northern Arizona University
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The Sevier orogeny defines a more western
event that took advantage of weak bedding
planes in thick Paleozoic and Mesozoic
sedimentary rock. Shortening in basement
metamorphic and igneous rocks was
transferred tens of miles eastward along the
weak shale and evaporite layers, producing
“thin-skinned” thrust faulting that, in its
eastern part, only involved sedimentary strata.
In contrast, the Laramide orogeny produced
“basement- cored” uplifts because thin
sedimentary rock in those areas did not easily
“decouple” from the basement rock.
Interacting Sevier and Laramide
“Montana Overlap”
animation by Rick Allmendinger
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Basin
and
Range
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Colorado
Plateau
Big Horn
Range
Wind River
Range
High
Plains
Challis volcanic episode
(~50 Ma)
Challis volcanic episode
(~50 Ma)
Basin and
Range
Extension
(~15 Ma –
present)
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Approx limit of
Cordilleran ice
sheet
Columbia
River
Basalt
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But how do we know this stuff?
Mostly, by making geologic
maps!
What is a geologic map?
• A spatially-indexed collection of observations
• An expression of an hypothesis about earth
history and the resulting distribution of earth
materials (geologic map units)
• A tool for creating and testing such
hypotheses … map is a verb
Schedule for this week
6/30 Monday getting settled/Intro lectures/practice
7/1 Tuesday
Frying Pan Gulch to measure section
7/2 Wednesday Frying Pan Gulch mapping
*evening lecture in visualizing 3d geology & cross
section
making review
7/3 Thursday Frying Pan Gulch mapping
**Map check at 7:30 pm*
7/4 Friday
7/5 Saturday
7/6 Sunday
Off Day – Happy b-day ‘merica!
Frying Pan Gulch mapping
Office day
Strat column, + Frying Pan map project due 9 pm (don’t be
late!)
7/7 Monday
lecture
7/8 Tuesday
DAY OFF – 8 pm “Frying Pan redux”
Start of Block Mountain