Sedimentary Structures

The word texture is used specifically to describe the size and arrangement of grains or crystals which make up a rock.  The texture of a sedimentary rock can usually be described accurately based on a specimen which you can hold in your hand.

In contrast, sedimentary structures describe properties of whole layers of sedimentary rock.  Sedimentary structures are thus best observed in the field, or on large slabs of rock.  With practice, sedimentary structures can be accurately identified from photographs.

Sedimentary structures provide valuable clues about the conditions on the ancient earth under which layers of sediment were deposited.  In combination with clues from the composition of sedimentary particles they allow geologists to reconstruct the environment of the past.

Students in Earth Science 110 and Geology 110 should be able to recognize and interpret these three basic types of sedimentary structures:

• Crossbedding
• Mudcracks
• Ripple Marks

Students in Geology 101 should also be able to distinguish current from wave ripple marks, and identify and interpret graded beds.

In our Geology 201 (earth history) course sedimentary structures are a major topic, and several additional, more specialized, structures will be added to this list.  More material will be posted for the Geology 201 course when that course is next taught (in the spring of 2002).

Review your text and notes concerning sedimentary structures, then click here to begin this on-line review.

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