Amsden Creek, WY
Purpose and Introduction
This project is a two-day introduction to geologic mapping. During this project you will begin to learn how to locate yourself on a topographic map, recognize, define and map rock units, collect structural data, locate formation contacts, take quality field notes and make field cross sections.
The field area is located within state-owned land of the Amsden Creek Big Game Winter Range, northwest of Dayton, Wyoming. Because this project is an introduction to geologic mapping, we will begin mapping as a single large group. The faculty will remain with the group for a least one half of the first day, and you will be free to map the area with your partner thereafter. The geology of the area consists of homoclinally dipping Mesozoic and Paleozoic strata: the same rocks that the class described and measured in the Regional Stratigraphy Project. No mappable faults or stratigraphic pinch-outs are present in this area.
Helpful Hints
- review your field notes from the Regional Stratigraphy Project to aid in defining rock units.
- the Tensleep Formation is thinner in this area (use a thickness of 120')
- structure, unit thicknesses, and geomorphic expression must be consistent for an accurate map.
- draw schematic cross sections in your field notes to determine structural and stratigraphic relationships.
- be sure to have complete coverage of structural data throughout the map area; you should have at least fifteen strike and dip measurements on your finished map.
Project Components and Layout
Follow the Guidelines for Map and Cross Section construction when preparing your project. The map, explanation and both cross sections should be constructed on The paper provided to you. You are free to design the layout of these items any way you like, but they all must fit on the same sheet of paper.
When mapping in the field or drawing your cross section, observe the following guidelines:
- rock units below the Cretaceous should be mapped separately.
- in the Cretaceous succession, map the Cloverly Fm. as a separate unit, and lump all younger Cretaceous units together as Ku (Cretaceous Strata, undivided).
- draw your geologic cross section down to an elevation of 1000' above sea level.
At the end of this project you will turn in
- a final colored and inked map,
- the map explanation with brief descriptions and formal names for each map unit,
- one geologic cross section assigned by the instructor(s),
- your field notebook.
- your field map