Introduction
Several dolomite and shale formations of Silurian age are exposed in Clifty Falls State Park--primarily the Salomonie Dolomite. The formation, formed in a shallow ocean, consists of unique layers that share the same properties. Click for a larger image (IUPUI Earth Sciences).
All 100-level geology courses discuss the rock cycle—the process responsible for creating all Earth material. In this laboratory, we are going to focus on only two parts of the rock cycle—sedimentary rocks and sediment. Why? Indiana is dominated by these two types of Earth material—and we wanted you to only spend your laboratory time learning about the material you will see in Indiana.
However, your laboratory exercise assumes you already know about the rock cycle. So, in this overview, we will review the rock cycle and some basics of sedimentary rocks in Indiana. The readings included within the laboratory exercise will give you most of the background you need to identify your rocks. As part of this course, we had you purchase a set of sedimentary rocks. In this lab, you will work on identifying their properties before you visit some state parks. This will help you identify rocks on your field trips.
Identifying a rock in a landscape is like being able to identify a color in a painting--you are only looking at part of the picture. Geologists identify rocks in order to interpret the environment they formed within. Geologists term this a paleoenvironment, or ancient environment--meaning a unique combination of the living and non-living materials present and the earth processes that affected them. After we discuss the rock cycle, we will discuss paleoenvironments that can be determined from those rocks.
Reading
You have quite a bit of reading for this lab, however, this is a very important exercise for the field trips for this lab. Indiana's surface is covered with sediment and sedimentary rocks, so an understanding of these Earth materials is critical to your understanding the geology of the state.
BEFORE continuing this overview, please read the following pages in your lab book:
Pages 69-81: Please read all the text associated with this lab, and review the figures. Pay special attention to figures 2, 3, and 10, as we will refer to these again in our field trip work.
Pages 97-133: Focus on the following pages that describe common sedimentary rocks and their environments of deposition:
- Scope and Methods and Rock Cycle Overview (pages 97-98)
- Sedimentary Rocks Overview (pages 98-101)
- Transformation of Sediment into Sedimentary Rocks (page 102-103)
- Classification of Sedimentary Rocks (108-120)
- Shales (pages 121-122)
- Carbonate and Chemical Rocks (pages 123-129)
- Chemical Precipitates and Organic Deposits (pages 129-131)
- Sedimentary Environments of Deposition (pages 131-133)
The workbook reading is organized in the following way: First, a section reviews the rock cycle and properties of each different rock type. Then, it goes into much more detail on how to identify sedimentary rocks, and how sediments turn into sedimentary rocks. Next, it explains how geologists "read" sedimentary rocks to determine information about the paleoenvironment they formed within--followed by a rock by rock description of each sedimentary rock, and the different types of environments they form within--starting with shale.
Finally, it ends by describing the common types of paleoenvironments found on earth, and the types of sedimentary rocks and rock features you would expect to find in each environment. Directions for completing the exercises are found in the "content" section.
This lab is very important for your field trips - as you complete each field trip in this course, you will spend a lot of time looking at different sediments, and in some cases trying to determine what type of paleoenvironment or modern environment the sedimentary rocks or sediment formed within.