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Heart Mountain, WY

Purpose and Introduction

This mapping area is in part of the Heart Mountain Detachment area. The Heart Mountain Detachment is a classic structure whose important features are outlined in the accompanying field guide (Malone and others, 1999). This area consists of gently dipping upper Paleozoic and Mesozoic strata that are cut by steeply-inclined dip-slip faults, allochthonous Paleozoic rocks that are bounded below by the gently inclined Heart Mountain Detachment fault, and Eocene volcanic and plutonic rocks of the Absaroka Volcanic Supergroup.

The goal of this project is to answer the following questions about the tectonic history of this area:

  • In which segment of the Heart Mountain Detachment is this project area located?
  • Which formed first, the steeply inclined faults or the Heart Mountain Detachment?
  • Which formed first, the Heart Mountain Detachment or the deposition/emplacement of Eocene volcanic rocks?
  • Which model of Heart Mountain faulting is best supported by your field observations?

Helpful Hints

  • Grizzly bears and moose use this area. Be careful.
  • In this area, you will be mapping in an area with limited outcrop, and little alluvium.
  • You should indicate areas of abundant outcrop on your map in darker than usual coloring.
  • Float mapping is important. You may find yourself using more dashed contacts on this 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 you are provided. 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.

  • Draw cross sections down to a depth of 5000’ above sea level.
  • Use the following color scheme for formations in the area.
    • Eocene Volcanic Rocks - pink, Tv
    • Chugwater Formation - red, TRc
    • Dinwoody-Park City - green TR-Pdp
    • Tensleep Sandstone - orange Pt
    • Amsden Shale - brown Pa
    • Madison Formation - blue Mm

At the end of this project you will turn in:

  1. a final colored and inked map,
  2. the map explanation with brief descriptions and formal names for each map unit,
  3. two geologic cross sections assigned by the instructor(s),
  4. your field notebook.