7.5 Common Clastic Sedimentary Rocks

7.5 Common Clastic Sedimentary Rocks

Clastic Sedimentary Rocks with Gravel-Sized Clast

• Notice the conglomerate rock on the left has clast with smooth rounded clast.

• While the breccia on the right has clast with sharp angular edges.

Sand -Size Clasts

• Sandstone and Quartz sandstone are difficult to differentiate. Principally, quartz sandstone will be very light in color compared to a darker sandstone

• Arkose sandstone contains slight larger/coarse particles composed of pinkish colored feldspar.

• Graywacke, common in the Bay Area, is composed of several different minerals such as quartz, feldspars and dark micas.

Mud-Sized Clasts

• As you can see, siltstone has slight large silt-sized particles in medium-thick layers.

• Shale, on the other hand has very small clay sized minerals and breaks in sheetlike pieces or chips.

Multiple Choice

Identify this rock

• sandstone

• shale

• breccia

Multiple Choice

Identify this sand-sized clastic rock.

• siltstone

• arkose

• conglomerate

Multiple Choice

Identify this rock by it's thin layers.

• shale

• graywacke

• quartz sandstone

Multiple Choice

Identify this gravel-sized clastic rock.

• conglomerate

• breccia

Multiple Choice

Identify this clastic rock that is common to the Bay Area.

• shale

• graywacke

• arkose

Multiple Choice

This clastic rock can be found throughout Utah and Arizona.

• graywack

• breccia

• sandstone