Cutting Edge > Develop Program-Wide Abilities > Geoscience in the Field > Designing Field Experiences > Activities > A Traverse Through Time and Space: A Paleoenvironmental Analysis of Devonian Strata in New York State

A Traverse Through Time and Space: A Paleoenvironmental Analysis of Devonian Strata in New York State

Tara Curtin
,
Geoscience Department, Hobart & William Smith Colleges
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This activity was selected for the On the Cutting Edge Reviewed Teaching Collection

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This page first made public: Dec 8, 2011

Summary

This is a field-based mini-project that requires students to synthesize their field data to 1) determine the depositional environments both across New York State (from the Catskills, NY to Rochester, NY) during the Lower and Middle Devonian, 2) recognize major unconformities, and 3) decipher the relationship between tectonics and sedimentation.

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Context

Audience

This several week long project is designed for an undergraduate course in sedimentology. I assume that students have completed one semester of physical geology prior to enrollment. There are anywhere between 9 and 16 students who enroll in this course.

Skills and concepts that students must have mastered

By this time in the semester, students have learned to identify common minerals and rock fragments found in sedimentary rocks and sedimentary structures in different environments based on field observations and lab simulations. Students know how to identify siliciclastic and carbonate rocks. Students have also been introduced to proper use of a Brunton compass for mapping (pace and compass) and measuring a stratigraphic section with a Jacob staff.

How the activity is situated in the course

This project is comprised of a sequence of field exercises that occurs during the middle portion of the course that spans five weeks. Each week, during the 3.5 hr long lab period, we visit different Devonian outcrops that are within 20-40 minutes of campus. We also take a required 3-day trip to the Catskills (4.5 hrs from campus) to explore different Devonian strata. Students are aware that this trip is required prior to enrollment in the class.

Goals

Content/concepts goals for this activity

At each field locality, students, in groups of 2 or 3, will:
Back in the lab, each student will:

For this project, we visit five local outcrops and take one 3-day trip to the Catksills, NY region. Students have 8 stratigraphic columns to use for their paleoenvironmental analysis of Lower and Middle Devonian strata across New York State.

Higher order thinking skills goals for this activity

Other skills goals for this activity

Description of the activity/assignment

The purpose of this project is to develop students' field skills by starting at the outcrop scale and then building on these experiences to create a regional picture of events by visiting multiple sites across NY. Students become proficient and efficient at measuring stratigraphic sections in teams after 5 weeks of field work. We visit eight outcrops within 5 weeks and measure detailed stratigraphic sections at each site. We begin by learning how to measure a detailed ~6 m thick stratigraphic section of siliciclastic rocks exposed in a local state park (that students visited during their introductory physical geology course) using a Jacob staff and Brunton. The outcrop is comprised of only 3 lithologies, but many sedimentary structures (bioturbation, flute casts, drag marks, groove casts, asymmetric ripples (plan view) and trough cross-beds). These lithofacies repeat several times even within the ~6 m measured section as these are turbidite deposits. We return to the lab after measuring the section and students work up their field data to construct a detailed, hand-drawn stratigraphic section for the first time. Students also make paleocurrent measurements in the field when possible and learn to plot these pooled class data during the next class meeting. For the other local sections, students perform the same field observations and measurements. At these locales, several formations crop out and students learn to recognize them based on their lithologic and paleontologic composition. Both carbonate and siliciclastic rocks occur at these sites. During the 3-day weekend field trip, students measure three stratigraphic sections of Lower Devonian through Middle Devonian strata and recognize that, for example, western NY lacks the Helderberg carbonate sequence and that the Oriskany Sandstone is thicker and laterally continuous in eastern NY rather than the lenses that crop out in central-western NY. Students also realize that the Hamilton Group changes character as they march across NY, building on their reading of Walther's Law in Boggs (2006) and their in-class stratigraphic correlation (lithostratigraphy, biostratigraphy) exercises from Fichter and Poche (2001) completed prior to the weekend field trip.

Determining whether students have met the goals

  1. I collect field notebooks and make comments and suggestions on how to improve their work using large Post-It notes rather than writing in their notebook. Because I expect students to read these comments and use them to do a better job during the next field exercise, I collect their notebooks at the end of lab, and return them by the beginning of the next class meeting. Their graded work depends on the quality of their field notes. To grade the notebook and the work penalizes students twice.
  2. I grade the hand-drawn stratigraphic sections as this is the basis of all other analyses. These are submitted each week.
  3. I also grade any paleocurrent plots generated each week.
  4. Each week, I pose a few questions before we go into the field to focus our work that day. I grade their responses each week.
  5. As part of the culminating assignment, students submit facies maps and correlated stratigraphic columns for a grade and identify any stratigraphic pinchouts and unconformities that occur across the state as well as coarsening or fining upwards sequences.
  6. The culminating exercise is to write a geologic history (~6 typed pages, single-spaced, not including figures) of New York during the Lower and Middle Devonian using all the data and figures already submitted and returned. All of their previously work (stratigraphic columns, stereonets, etc.) are re-submitted with the paper. I expect any errors in the figures, maps, and sections to be corrected in this final version.

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