Virtual Geological Mapping Field Trip - Glens of Tekoa, New Zealand

Travis Horton (Associate Professor); Kate Pedley (Lecturer); Sam Davidson (Ph.D. candidate); Jamie Delano (Ph.D. candidate); Yusuf Bhatti (Ph.D. candidate)

Te Kura Aronukurangi/School of Earth & Environment, University of Canterbury, Christchurch, New Zealand


Summary

Geological mapping involves the observation, recording, presentation and interpretation of field data, all fundamental skills required by practicing geologists. This virtual geological mapping exercise enables intermediate undergraduates studying geoscience to create a geologic map and cross-section for the tectonically deformed Glens of Tekoa area of North Canterbury on the South Island, New Zealand.

Resources available include: 1) a virtual field trip resources document; 2) a virtual field trip video with associated photographs of 19 outcrops at varying scales; 3) an outcrop data sheet; 4) a topographic basemap; 5) a topographic profile for cross-section drafting; 6) a New Zealand Journal of Geology and Geophysics background reading on the map area's stratigraphy and geological history by W.D. Sevon (1969).

Learning goals include: 1) Having fun!; 2) Recognizing and recording the structure, texture and composition of common rocks; 3) Accurately using geological terminology; 4) Creation of a geological map and cross-section.

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Context

Audience

This virtual field trip is aligned to a second-year undergraduate field course in Geology at the University of Canterbury, Christchurch, New Zealand. The target audience for this virtual geological mapping experience is: upper-level undergraduate students of geology, with a platform of moderate understanding of rocks, minerals, and structural geology.

Skills and concepts that students must have mastered

Students should have a moderate (i.e. above first-year undergraduate) understanding and knowledge of basic geological terms and processes, including: 1) common rocks and minerals; 2) basic geological structures (i.e. simple folds and faults); 3) a conceptual understanding of strike and dip; 4) proficiency in reading topographic maps and using geographic latitude/longitude coordinates; 5) a basic understanding of tectonics and deformation.

Undergraduate geology curricula differ between institutions and instructors will be best able to determine how this virtual field trip aligns to their institution's curriculum and scaffolding. At the University of Canterbury, 40-120 first-semester second-year (i.e. sophomore) successfully complete this learning experience every year. Prior to completing this exercise, these students will have passed at least 2 introductory level (i.e. first-year) undergraduate geology courses, including introductory coursework covering: a) sedimentary, igneous and metamorphic rocks; b) common rock-forming minerals; c) basic faults and folds; d) strike and dip; e) geological time/time-scale; f) aspects of geological history and tectonics.

Upper-level undergraduate students of geology should be able to successfully complete this virtual field trip experience.

How the activity is situated in the course

This virtual field trip activity is positioned as a stand-alone geological map making exercise that is worth ~60% of course marks/grade in the equivalent University of Canterbury course in Geological Science (School of Earth and Environment). At the University of Canterbury, the remaining 40% of course marks/grade is covered by a separate geological map reading examination.

Goals

Content/concepts goals for this activity

Learning goals include: 1) Having fun!; 2) Recognizing and accurately recording the structure, texture and composition of common rocks; 3) Accurately using geological terminology; 4) Creation of a geological map and cross-section that is geologically consistent with the available structural, textural and compositional information/data.

Higher order thinking skills goals for this activity

Higher order thinking skills goals include the development of a student's ability to interpret geological events/history from virtual outcrop observations (i.e. outcrop structure, rock texture, rock composition) and geospatial context.

Other skills goals for this activity

Students successfully completing this virtual field trip exercise will be able to:


1) observe, record and interpret a variety of geological phenomena
2) systematically record geological outcrop data and measure/recognize basic structural, textural and compositional information
3) carry out geological mapping of moderately deformed bedrock
4) use topographic maps, Google Earth imagery and drone/unoccupied aerial system videos as an aid to geological mapping
5) interpret basic geological history

6) create a geologically reasonable bedrock map and cross-section for a moderately deformed igneous/sedimentary sequence of Mesozoic and Cenozoic rocks.

Description and Teaching Materials

HiMaterials for this virtual geological mapping field trip are available at:

https://www.dropbox.com/sh/6k1h09zbxfx8gu2/AACqeLL4xOzDZGRwhFSPNS3Na?dl=0

The above DropBox link includes the following individual files:

1) Field trip resources handout, including learning activities, learning goals and learning aids. GEOL.240.VIRTUAL.FIELDTRIP.resources.2020.docx (Microsoft Word 2007 (.docx) 41.2MB Jan3 21)

2) Basemap (blank) with topographic contour lines in three different formats (.eps; .png; .tif). GoT.2020.Basemap.v1.eps (Encapsulated Postscript 101.1MB Jan3 21)

GoT.2020.Basemap.v1.tif (TIFF 49.8MB Jan3 21)

3) Cross-sectional profile (blank) in three different formats (.eps; .png; .tif). GoT.2020.Cross-Section.v1.eps (Encapsulated Postscript 101.6MB Jan3 21)

GoT.2020.Cross-Section.v1.tif (TIFF 50MB Jan3 21)

4) Outcrop data entry/summary sheet (blank; one sheet for each outcrop). GoT.virtual.Fieldtrip.Outcrop.Data.Sheet.docx (Microsoft Word 2007 (.docx) 8.4MB Jan3 21)

5) PDF of a publicly available published article (Sevon, 1969) on the geology of the mapping area, including a coarse geological map at coarse scale. Sevon.1969.pdf (Acrobat (PDF) 5.4MB Jan3 21)

6) Copy of a virtual field trip video (~84 minutes) presenting the structural, textural and compositional information and context for all of the mapping area's geological outcrops. https://www.youtube.com/watch?v=YXxs0G4e8eU

7) Image files for all of the coarse scale and close-up outcrop photographs included in the virtual field trip video. For example:

Kia ora!

Your task is to make a detailed bedrock geological map and cross-section of the Glens of Tekoa area. A wide variety of tectonically deformed rocks occur at Glens of Tekoa, making the area perfect for learning basic geological mapping skills and terminology.

Your task can be broken down into four key activities:

  1. Familiarise yourself with the background information and resources provided to you, including this Glens of Tekoa – Virtual Field Trip Resources document. Other key resources include an article by Sevon (1969), the on-line Glens of Tekoa – Virtual Field Trip Video, Outcrop Data Sheets, and separate Basemap and Cross-Section files.
  2. Observe and collect geological outcrop data by watching the Virtual Field Trip Video and completing at least 19 separate Outcrop Data Sheets (at least one for each outcrop).
  3. Create a Geological Map of the Glens of Tekoa Area based on your structural, textural and compositional outcrop observations and data. You should create your maps using the Sketchbook app (https://sketchbook.com/) or similar software and the Basemap (A3 page size) file provided.
  4. Create a Geological Cross-Section based on the data and interpretations presented in your geological map. You should create your cross-section using the Sketchbook app (https://sketchbook.com/) or similar software and the Cross-Section (A3 page size) file provided.

Your completed outcrop data sheets will convey the data and observations you make using the materials provided. The virtual field trip video will be your primary source of information, but you encouraged to use the information included in Sevon (1969) to assist your observations and data collection.

When completed, your map should show the boundaries (i.e. contacts) between the geological units established by W. D. Sevon (1969). Major faults, fold axes and structural data (dips/strikes, trend/plunge of any fold axes) will be appropriately symbolised and drawn on a complete map.

Your cross-section should illustrate the geological sequence and structure. Please, use the A-A' topographic profile provided.

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Overview of Virtual Geologic Mapping Workflow

1) Prepare – identify the key questions/objectives of your mapping experience and visit outcrop #1, the library (i.e. read the relevant literature and resources provided!).

2) Orient –consider the mapping area and familiarise yourself with your basemap and associated resources (e.g. Google Earth). Take extra care to ensure that you are entirely confident in your ability to link your observations/data to a precise location on your basemap. Master the mapping area's stratigraphy (see: Sevon, 1969).

3) Plan – devise a reasonable plan for your work. We are all new to this virtual field trip experience and it is important to recognise and value the novelty of this exercise. If your initial plan/approach isn't working for you, change your approach!

4) Investigate – study (i.e. peruse) the outcrop information included in the Glens of Tekoa - Virtual Field Trip video. Short on-site video clips focusing on the location and structural aspects of the outcrops is provided, as well as photographs of the outcrops at various scales. Use the pause button liberally! If your video-browser does not zoom in enough, try downloading the video file and using the zoom capability of free apps like VLC. Record relevant information on your Outcrop Data Sheets.

5) Reflect (and Revise) – You want to be sure you are making good progress towards achieving your objectives/learning goals and outcomes, so take time for reflection. Jot down your thoughts, questions, feelings as you take this journey, and please share these reflections via Learn or email with your instructors. We can help you achieve your learning goals provided we know where you're at with your learning.

6) Start Drafting Your Map - it's a good idea to put all your structural observations on your geologic basemap map in one or more layers in SketchBook (n.b. turn on 'Layer Editor' under the Window tab so you can see what's in your map's layers; here's a YouTube video I made that shows some of the basics: [https://www.youtube.com/watch?v=M8nV3Em4swk]). Geological maps are highly condensed databases, and you will want to organise your map's effectively and efficiently (save your file regularly!). Drawing map unit contacts on a basemap is incredibly satisfying, but also a point of stress and anxiety for many geologists. The unit thicknesses given in Sevon (1969) will help immensely as there is inevitably a large amount of inference based on geological reasoning irrespective of whether you .are in the field or on a virtual field trip! Here's a second YouTube video, specific to this Glens of Tekoa VFT, on drawing and filling using Sketchbook: [https://www.youtube.com/watch?v=5LklS47NRBQ&t=26s].

7) Interpret –it is helpful to have dedicated time to interpretation once you have recorded your observations on your draft map. Interpreting helps to understand the geological story behind the data recorded on your map. Don't be afraid to question your observations – at any stage of the process. It's rock science, not rocket science, and things should make sense at fundamental levels. For example, older rocks are typically beneath younger rocks – superposition. Yet, when older rocks are over/above younger rocks, it's not necessarily wrong, it just needs a rigorous geological explanation. Tectonics/deformation tend to be a choice solver of riddles!

[Repeat 1-7 Daily]

8) Prepare you Final Geological Map, Cross section, and Outcrop Data Sheets – my only advice here is don't wait until the last minute! You should be making regular progress on your data sheets and map. The cross-section should be last.

***************************************************************

Overview of Virtual Geologic Cross-Section Workflow

Construction of a cross-section is a critical part of geological mapping. Although we live on the ground surface and tend to focus our attention on what's above ground, most geology is in the sub-surface. If we are to accurately predict the location of oil, gas, mineral deposits (or water resources) we need to have a good understanding of subsurface geology. Cross-sections are crucial.

A geologic cross-section is an interpretation of the distribution and structure of rock units in the subsurface. Geologic cross-sections are constructed by first considering and understanding the surface geology (i.e. make your map first!). Once a reasonable understanding of the geology exposed at the surface is attained, we start placing geologic unit contacts on the base map, and by combining these data with structural observations (e.g. strike and dip data) we construct a cross-section.

The basic procedure for construction of a geologic cross section is as follows:

1) Make comprehensive observations with regard to the geology at the surface and record accurate notes of outcrop structure. If your structural data is poor, your cross-section will also be poor. If your structural data is clear, well organized, and comprehensive, you are very likely to produce a high-quality cross-section!

2) Using your topographic profile, add the geologic unit contacts to the cross section. The degree to which you will be able to locate contacts on your geologic map will vary. Some of the geologic contacts you will be able to locate precisely. Others you will only be able to approximate. Use a solid black line for well-located contacts and a dashed line for contacts that are less precisely located.

5) Project the geologic contacts into the subsurface to form your cross section, make use of any strike and dip information you have regarding the orientation of the map units (at the surface). Be sure that your cross-section is geologically reasonable. For example, don't project your contacts straight down to great depth using a straight edge! If you think the contacts are deformed (curved/folded), show that on your cross-section! Deformed rocks can – and do – have rapidly changing dip angles over relatively short distances. Don't forget to infer the location (and tilt!) of any major faults/fold axes.

6) Finalize your cross section. Colour the units on your map and cross-section using the same colour scheme and symbols. Complete a legend/stratigraphic column/ symbol explanation.

Teaching Notes and Tips

Here is one version of a geological map and cross-section 'key'.

Geologic Map (Key: version 1):

Cross-Section (Key: version 1):

Assessment

Here is one version of a detailed marking schedule/rubric. We weighted the map, cross-section, and outcrop data sheet points such that each of these three assessment areas constituted one-third of the total assignment marks/grade.

Marking Schedule/Rubric:

References and Resources

Please refer to the University of Canterbury web-page for the associated undergraduate course:

GEOL240: Field Studies A

https://www.canterbury.ac.nz/courseinfo/GetCourseDetails.aspx?course=GEOL240&occurrence=20S1(C)&year=2020

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