Sedimentary Rocks 101

What is a sedimentary rock?

sedimentary rock is an accumulation of fragments of pre-existing rocks (sediments). There are three types of sedimentary rocks; Clastic (detrital), Chemical, and Biochemical (organic) rocks.

How is a sedimentary rock made?

Since sedimentary rocks are pieces of many different rocks they must be lithified together to form a solid rock before they can actually be called a sedimentary rock. There are three types of lithification; compaction, cementation, and crystallization.

What is the difference between compaction, cementation, and crystallization?

Compaction happens when weight from the materials above compact sediments together to form a solid rock. Cementation happens when a precipitation from a mineral cements surrounding sediments together making them a solid rock. Crystallization happens when a solid rock is created from a solution.

Where do the sediments that make up sedimentary rocks come from?

Sediments are the result of weathering which breaks up pre-existing rocks. There are two types of weathering; Mechanical and Chemical. After the rocks are weathered and broken down into sediments they are transported via water, wind, glaciers, or gravity to different depositional environments. Finally after being deposited the sediments accumulate to form a sedimentary rock through lithification. Sediments come in all different shapes, sizes, and sortings. The way sediments are sized, shaped, and sorted can tell us about their depositional environment and how they journeyed to get there.

What’s the difference between Clastic, Chemical and Biochemical sedimentary rocks?

Clastic or detrital sedimentary rocks are made of sediments that are the result of weathering and transport. Chemical rocks are created from chemical precipitation. Biochemical or organic rocks are made up biological remains.

What are properties of Sedimentary rocks used to identify them?

Properties of sedimentary rocks used to identify them include texture, composition, particle size and sedimentary structures. Not only do these properties help you identify the type of sedimentary rock you have but also in what type of depositional environment the rock was formed.

What are the different textures associated with Sedimentary rocks?

Types of sedimentary textures include clastic, bioclastic, crystalline, amorphous, and oolitic. To see further definition of these textures click on them so you can be redirected to the glossary.

What matter is found in the composition of Sedimentary rocks?

The composition of sedimentary rocks can be made up of the following things: carbonates, silica, clay minerals, organic matter, evaporites, rock particles, heavy minerals, and feldspar.

What is a Sedimentary Structure?

A sedimentary structure is a structural feature in a sedimentary rock formed as a result of weathering or transportation. Types of sedimentary structures include: stratification, cross bedding, graded bedding, ripple marks, oscillation marks, mud cracks, raindrops, and trace fossils.

What is a depositional environment?

Depositional environments are the places where sediment accumulates. There are three different groupings of sedimentary environments: continental, marine, and transitional. They are then further broken down into sub groups such as dunes, marsh, mountains, etc.

How does looking at sedimentary rocks properties tell me about where the rock was formed?

In order to determine where a sedimentary rock was formed you must look at every aspect of it. From the sediment size, shape, and sorting to the structures present in it. For example lets say we are looking at a conglomerate. In it we see angular sediments that are poorly sorted. This tells us that the rock did not travel far from its source because the sediments are sharp and jagged and there are many different types of rocks. Most likely it came form a mountainous or piedmont region. On the other hand if we had sandstone with ripple marks and cross bedding we could say that it was by a source of water because of the ripple marks and that wind probably caused the cross bedding. Therefore it was probably formed in a costal area.

Sedimentary Rock Flow Charts

Sedimentary Rock Flow Chart Part 1

Sedimentary Rock Flow Chart Part 2