Sedimentary Rocks

Sedimentary Rocks

• Sedimentary Rocks - Those rocks that form from the aggregation of sediments that have been transported, deposited, and later lithified.

• Sediments are essentially fragments and particles of other rocks and/or minerals.

How is a sedimentary rock produced?

– The Sedimentation Process - producing sediments.

• Weathering and Erosion

• Transportation

• Deposition

– Lithification Process - How to convert sediments into rocks.

• Compaction

• Dehydration

• Cementation


• Two types of sedimentary rocks based on the sources of their major components -

– 1. Detrital sedimentary rocks - composed of particles call detritus, which means rock particles and/or minerals from other rock types. Also known as Clastic !

– 2. Chemical sedimentary rocks - composed of precipitates or chemicals that were in solution within a liquid, usually water. Note Biochemical used by textbook.


• Detrital Sedimentary Rocks -

– These rocks are composed of other rock types. Quartz is one of the most resistant rocks to weathering and is a dominate component of many sedimentary rocks.

• Gravel = Conglomerate or breccia 2-> 256 mm

• Sand = Sandstone 1/16-2 mm

• Mud = Mudstone to shale < 1/16 mm


• Chemical Sedimentary Rocks

– These rocks are composed of materials carried in solution within lakes and oceans and/or of a biological origin.

• Limestone from dissolved CaCO

3

• Conquina is a coarse rock composed mostly of loosely cemented shells and shell fragments.

• Chert, flint, agate, etc. is from SiO

2

• Evaporites are salts - rock gypsum

• Coal - from organic material


• The importance of these rocks is that they typically make-up 75 volume % of the upper most part of continental crust and are expressed as strata or beds or rock layers .

• Strata are the record of paleoenvironments .




• The study of strata, beds, and their respected paleo-environments is the science of stratigraphy .

• Stratigraphic formation -sequence of strata distinctive enough to be traced across a large region.

• Special kinds of Bedding - Cross beds and graded beds.






• Sedimentary Environments - these are environments where sediments were deposited.

– Glaciers, mountain streams, alluvial fans, sand-dunes, lake, ponds, rivers, etc.

– Reflective of a specific type of depositional energy.











Sedimentary Rocks - What Next?


• What processes produce sediments?

– Weathering - disintegration and decomposition of rock at or near surface (Mechanical and chemical)

– Mass wasting - transfer of rock material down-slope under the influence of gravity.

– Erosion - incorporation and transportation of material by a mobile agent, usually water, wind, and/or ice.

Sedimentary Rocks - Connolly, Harold

How is a sedimentary rock produced?

Sedimentary Rocks