Field Trip 4 Geologic Mapping of a Virtual

Field Trip 4: Geologic Mapping of a Virtual Landscape Outline for Today • • • 10 am Tech. issues, printed maps, intro. to project 10: 30 Get started individually – discover and map outcrops 11: 00 Reassemble: address general questions 11: 15 Breakout Room (9 + staff member): address breakout questions Noon Reassemble to answer questions 12: 30 Lunch 1: 15 Reassemble: afternoon instructions 1: 30 Individual work to finish outcrop mapping 2: 30 Reassemble: instructions for finishing map using strike lines 3: 00 -5: 00 Finish mapping? & stratigraphic section? M. Helper, Geo 420 k, UT Austin 1/20/2022

Lighthouse Bay: Mapping a Virtual Landscape Steps 1. Visit and record observation at 33 outcrops to create an outcrop map Lig h No t col o te xpo red; sed from limited observations using educated guesses Da rk ou color tcr op ed s The Challenge: Create a geologic map 2. Use strike & dip data to create strike lines 3. Use intersection of strike lines and topo. contours to extend rock units across the map and fill in the blanks M. Helper, Geo 420 k, UT Austin Example outcrop map with inferred (dashed) contacts 1/20/2022

Lighthouse Bay: Products; Stratigraphic Column 1. Map and map key 2. Stratigraphic column Carefully read the directions in the handout for details of what these products should contain M. Helper, Geo 420 k, UT Austin Example Only! Trip 4 Products: Sample Strat. Column 1/20/2022

Outcrop Colors and Proper Strike & Dip Symbols 22 Strike and Dip of Bedding Symbol • Long line parallel to strike azimuth • Short line parallel to dip direction (perp. to strike!) • Number is measured dip Color outcrops by rock types/units; may discover more than one unit of the same rock type M. Helper, Geo 420 k, UT Austin 1/20/2022

Lighthouse Bay: Mapping Tips • • • Use topography, features, GPS (G) and Compass (C) to locate outcrops Color and plot strike and dip (with protractor) as you go! Pay attention to rock descriptions, not just rock type Screen capture or copy rock descriptions; number them by outcrop Beware of misplaced windmills – remap M. Helper, Geo 420 k, UT Austin 1/20/2022

Let’s Get Started We reassemble at 11: 00 –What can you accomplish and where did you have problems? M. Helper, Geo 420 k, UT Austin 1/20/2022

11 am Reassemble: What Did You Discover? • How Many Outcrops Visited? • How Many Rock Types? • Does Strike and Dip Change? • Do You Have a Strategy of Where to Go Next Based on What You’ve Mapped? M. Helper, Geo 420 k, UT Austin 1/20/2022

3 Teams: Breakout Room Questions: Team 1: Where are the oldest rocks on the map? Answer with outcrop number(s) Team 2: What is the stratigraphic sequence, from oldest to youngest? Answer by placing outcrop numbers in ordered list Team 3: What does the orientation of strike & dip predict for the shape and direction of V’s as rock units cross valleys and ridges? Answer via annotated shared screen - Answers in Chat Window and shared screen at Noon M. Helper, Geo 420 k, UT Austin 1/20/2022

Noon Reassemble: Breakout Group Reports 1. Where are the oldest rocks on the map? Answer with outcrop number(s) 2. What is the stratigraphic sequence, from oldest to youngest? Answer by placing outcrop numbers in ordered list 3. What does the orientation of strike & dip predict for the shape and direction of V’s as rock units cross valleys and ridges? Answer via annotated screen share M. Helper, Geo 420 k, UT Austin 1/20/2022

Group 3 M. Helper, Geo 420 k, UT Austin Scratch Copy 1/20/2022

12: 30 Lunch Break Be back online by 1: 15 Afternoon Schedule • 1: 30 Individual work to finish outcrop mapping • 2: 30 Reassemble: Instructions for finishing map using strike lines – Bugaloo Butte Example • 3: 00 -5: 00 Finish map, key & stratigraphic section M. Helper, Geo 420 k, UT Austin 1/20/2022

1: 15 Back to Work! Afternoon Schedule • 1: 30 Individual work to finish outcrop mapping • 2: 30 Reassemble: Instructions for finishing map using strike lines – Bugaloo Butte Example on Canvas, Trip 4 Assignment • 3: 00 -5: 00 Finish map, key & stratigraphic section M. Helper, Geo 420 k, UT Austin 1/20/2022

2: 30 Reassemble: Instructions for finishing map Using strike lines to extend rocks across the landscape – where do rock unit contacts go? Bugaloo Butte Example Shows How! M. Helper, Geo 420 k, UT Austin 1/20/2022

Making a Map from a Strike and Dip Measurement Bugaloo Butte Example Point A is on a contact that strikes E-W and dips 45 o South. Map the trace of the contact on Bugaloo Butte using 100 m strike lines. (Note: this is an animated slide that can’t be viewed as such in a PDF or a. pptx previewer. Please see the posted Power. Point or MP 4 of this slide for the step-by-step example) M. Helper, Geo 420 k, UT Austin 1/20/2022

Strike Lines and Contacts (schematic) 70 60 50 40 30 20 10 ? ? 70 50 m 60 50 40 30 20 10 60 m intersections 1: 5000 1 cm = 50 meters M. Helper, Geo 420 k, UT Austin 1/20/2022

Strike Line Spacing Calculation North X South (Strike line spacing for 10 m elev. change) 22 o Dip pin g ro ck uni t 10 m con tac t X = 24. 75 m M. Helper, Geo 420 k, UT Austin 60 m contour 50 m contour 1/20/2022

Scaling Strike Line Spacing For Map Scale: 1: 5000 How far apart are strike lines on map for 24. 75 meter spacing? 1 map distance 5000 ground distance = X m on map 24. 75 m on ground X= Map distance is 0. 00495 m, ~5 mm M. Helper, Geo 420 k, UT Austin 1/20/2022

Strike Lines and Contacts (at 1: 5000 scale) 70 70 60 50 40 30 20 10 50 m ~5 mm 60 50 40 30 20 10 1: 5000 1 cm = 50 meters M. Helper, Geo 420 k, UT Austin 1/20/2022

Finishing Your Map and Strat. Column • Please read and carefully follow the instructions • Emulate the examples in the handout to finish your work • For strat. column, assume all units are Jurassic QUESTIONS? M. Helper, Geo 420 k, UT Austin 1/20/2022

Scratch Copy M. Helper, Geo 420 k, UT Austin 1/20/2022