Download Sedimentary Rocks - Connolly, Harold

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
Sedimentary Rocks
• 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.
Sedimentary Rocks
• 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
Sedimentary Rocks
• 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 CaCO3
• Conquina is a coarse rock composed mostly of
loosely cemented shells and shell fragments.
• Chert, flint, agate, etc. is from SiO2
• Evaporites are salts - rock gypsum
• Coal - from organic material
Sedimentary Rocks
• 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.
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• 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.
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• 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.
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Sedimentary Rocks - What Next?
Sedimentary Rocks
• 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.