Reconnaissance mapping of the Block Mountain area, MT
Summary
For this module, students are given to task of preparing a reconnaissance report for an oil company that is interested in exploring an area near Dillon, MT. In an effort to keep this field site in a pristine condition for future field camp classes, the module is designed around a reconnaissance level mapping where minimal actual field data is provided. Students will be expected to: draw lithological boundaries on Google Earth; define unit boundaries using provided field photos and stratigraphic information compiled from regional maps, and published literature and construct a representative stratigraphic column; conduct a stereonet analysis of the main fold using a set of strike/dip data that is not geo-located; construct two geological cross-sections across the field area; and write a geologic report on their findings that summarizes the general geologic features of the field area. This module is designed as a follow up module to the "Reconnaissance Mapping of the Frying Pan Gulch, MT) module which mainly focused on the stratigraphy and the description of the depositional setting of the units also found at the Block Mountain field area. The focus of this module is on the description of the structures and their evolution in a regional tectonic setting. Details of specific exercises within the module are described below:
Exercise 1a: This exercise consists of two parts. 1a is the geological mapping of a small portion of the field area. 1b is the maping of the entire field area. Utilizing the provided unit descriptions compiled from regional geologic maps and outcrop photos and brief descriptions as needed, students will be completing a geological map of a small, nearly 0.5 square mile area. A large group discussion will be held at the end of the day to discuss the contact choices. Smaller groups will construct schematic cross-sections and review and compare each other's at the end of the day. Google earth project file with labeled contacts will be submitted as a .kmz file by the beginning of the second day of the module. Final map will be drafted in Adobe Illustrator or a similar drafting software using the exported images of the Google Earth project. Exercise 1b is due the final day of the module.
Exercise 2: Stereonet Fold analysis. Students will be given a table of strike/dip data provided by one of their company colleagues grouped according to their corresponding fold limb. No actual location information will be provided. Students will conduct a stereonet analysis of the data and describe the fold and its geometry. This exercise is recommended to be given on day 3, after the students have a chance to complete most of the geological mapping and have a better understanding of the overall geology of the area.
Exercise 3: This exercise consists of two parts. Main part, Exercise 3a is the construction of a stratigraphic column. Those who have already completed the Frying Pan Gulch project can utilize their stratigraphic columns from that project and only add the few new units that were not exposed there. This representative stratigraphic column will utilize unit descriptions and ages from published maps and literature. Unit thicknesses will be obtained from the Frying Pan Gulch module. Thicknesses for the Dinwoody and Phosphoria formations will determined through a mini drill core exercise (Exercise 3b). Final stratigraphic column will be drafted in Strat Desktop and edited in Adobe Illustrator or a similar software as needed. 3b: This is a mini drill core exercise where depths to two of the units with missing thickness information will be determined using a combination of three points analysis and trigonometry.
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Context
Audience
Skills and concepts that students must have mastered
How the activity is situated in the course
Activity Length
6 daysGoals
Content/concepts goals for this activity
2. Collect accurate and sufficient data on field relationships and record these using disciplinary conventions (field notes, map symbols, etc.).
3. Synthesize geologic data and integrate with core concepts and skills into a cohesive spatial and temporal scientific interpretation.
4. Interpret earth systems and past/current/future processes using multiple lines of spatially distributed evidence.
5. Develop an argument that is consistent with available evidence and uncertainty.
6. Communicate clearly using written, verbal, and/or visual media (e.g., maps, cross-sections, reports) with discipline-specific terminology appropriate to your audience.
7. Work effectively independently and collaboratively (e.g., commitment, reliability, leadership, open for advice, channels of communication, supportive, inclusive).
8. Reflect on personal strengths and challenges (e.g. in study design, safety, time management, independent and collaborative work).
9. Demonstrate behaviors expected of professional geoscientists (e.g., time management, work preparation, collegiality, health and safety, ethics).
Higher order thinking skills goals for this activity
2) Synthesizing data to create a geologic map and cross section interpretation of the geology of the field area,
3) Answer any project specific questions based on the geologic cross-section interpretation, and
4) Synthesizing background and field data to write a summary of the geology and geologic history of the field area.
Other skills goals for this activity
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 a strongly deformed area
4) use topographic maps, Google Earth imagery and drone/unoccupied aerial system videos as an aid to geological mapping
5) interpret geological history
6) prepare geologic reports and maps using Google Earth, Adobe Illustrator, any stereonet software, and Strat Desktop.
Description and Teaching Materials
Students are given a .kmz file which contains the following folders and layers:
- Map areas and cross-sections
- Block Mountain Quadrangle
- 5m contour lines
- Photos
- Contacts
- Faults
- Folds
- Surficial deposits
- Unit labels
Stratigraphy_v3.doc contains a brief stratigraphic unit description compilation from regional geologic maps. This and any other information students can find will be utilized to decide formation boundaries.
Stereonet_data_BlockMt contains the Strike/dip data for the fold analysis exercise/
Block_Topo and Block_Naip are two basemap .pdf files that students will use as a basemap for their final maps.
Main contact mapping will be done on Google Earth. Lines will be exported to Adobe Illustrator (or a drafting software of choice) and retraced over an identical topographic map and satellite imagery. No geo-located strike/dip data will be provided to the students. However, once the contacts are drawn, students can determine strike/dip using three-points problem techniques. Students are encouraged to focus at least around the cross-section line. Two separate cross-section lines are included with the .kmz file. The northerly one (cross-section 1) requires the utilization of the stereonet analysis results into the construction of the cross-section. As an instructor, you can chose any one of these lines or assign a different line to your students. A review of structures observed in contractional tectonic settings and construction of balanced cross-sections as a class might be helpful.
Technology Needs
Google Earth, any drafting software (this module will refer to Adobe Illustrator), any stereographic projection software for basic fold analysis ( this module will refer to Stereonet 11 by Rick Allmendinger), Strat Desktop (by Rcik Allmendinger). Real-time internet access is needed to use google earth for drawing contacts and viewing photos. A scanner app on a smartphone is highly recommended for collecting the notebook entries as .pdf files Photos can be compiled into a pdf document and distributed if internet connection problems occur.
Teaching Notes and Tips
Project.kmz file can be shared with the students via the Learning Management Software package of choice. All individual assignments and the final reconnaissance report can be collected via the LMS as well.
Students should spend day 1 in drawing contacts and deciding which ones to assign as unit boundaries in the southern portion of the project area as it is structurally not complicated. Similar to the Frying Pan Gulch exercise, this can be combination of individual and group project. Once the contacts in the simpler area are established, students should continue with their contact drawing individually. Overview and outcrop photos will be critical determining some of the critical contacts. Similar to a real field mapping experience, random field notebook and map checks can be orchestrated.
Contacts drawn on Google Earth will be exported to Adobe Illustrator where final map and cross-section construction will be complicated. Students should be able to utilize the stratigraphic column, and map legend from the Frying Pan Gulch project and modify it only slightly for the this module.