Download Lab #22: Sedimentary Rock Identification

Name: _________________________
Date: _____________
Lab #22: Sedimentary Rock Identification
Class: __________
Science
Introduction: As you know, rocks are composed of minerals or a combination of minerals. Rocks are categorized into types
based on the way in which they form. Sedimentary rocks form as weathered, eroded and deposited materials are compacted
and cemented together beneath the weight of overlying sediments.
Sedimentary rocks are classified into three major categories based on their composition:
1. Clastic or fragmental rocks derived from weathering and erosion of land materials. They are identified by their grain size.
2. Crystalline which form from precipitation of dissolved salts in sea water. They are identified by composition.
3. Bioclastic rocks which are made up of fragments of living organisms. They are identified by composition.
The above characteristics, in turn, signify a particular environment of formation. As you know from our study of igneous
rocks, if you know the rock, you know the past environment! Using your senses and the Scheme for Sedimentary Rock
Identification, you will be able to first classify and identify the rocks and their environments of formation.
Procedure:
First take some time to familiarize yourself with the flow if the identification chart. The chart is read by deciding on
the texture first. The outline below be helpful as a guide.
The texture and composition of sedimentary rocks are determined by the environment in which they form. As you already
know, sediments sort out by size, both vertically and horizontally. Horizontal sorting is a major player in where sedimentary
rocks form.
Sample #
Texture
Composition
Rock Name
Other Characteristics
(Comments Column)
Environment of Formation:
1. Compaction and cementation of inorganic land-derived sediments
2. Compaction and cementation of organic material
3. Evaporation of a super-saturated solution
Environment of
Formation
Questions: All answers must be in full sentences and should be typed or written
1. What are the minimum and maximum dimensions (the size range) for the following particle sizes? (Hint: Use pg. 6 of the
Earth Science Reference Tables)
Cobbles:
________-cm to ________-cm
Pebble:
________-cm to ________-cm
Sand:
________-cm to ________-cm
2. How can you distinguish between a clastic (fragmental) sedimentary rock from a chemically formed sedimentary rock?
______________________________________________________________________________________________
______________________________________________________________________________________________
3. Describe the sequence of events in the formation of an evaporite (3-steps).
1) Water containing the dissolved minerals evaporates.
2) ____________________________________________________________________________________________
3) ____________________________________________________________________________________________
4. Describe the sequence of events in the lithification (cementation) of a sandstone (3-steps).
1) First, the weathering of older rock produces fragments which are carried by an agent of erosion.
2) ________________________________________________________________________________
3) ________________________________________________________________________________