sedimentary structures - SEDIMENTARY STRUCTURES Mechanical...

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SEDIMENTARY STRUCTURES Larger features brought on by deposition Layer by layer deposits - Sediments are commonly transported by a medium and then deposited horizontally, layer by layer. Although they may differ in setting/environment (terrestrial, marine), thickness, direction/pattern, etc.) - Sedimentary structures may be inorganic or organic. Inorganic structures are subdivided into Primary and secondary structures. Primary structures are made by physical processes and secondary structures are made by chemical processes. - Primary – “mechanical processes” - Secondary – “chemical processes” - Organic – “living forms interacting with the sediment” PRIMARY STRUCTURES Varying types of layering and thickness of compacted sediments Mechanical or Physical - Primary structures have various types of layering which results to a difference in thickness and form. These are the basis for classifying primary structures. – They undergo physical processes, and physical change, like a change in form. - Sedimentation Unit – Deposits made at a specific time period, under same conditions - Current flow in nature is never absolutely uniform but there is a prevailing current that deposits a prevailing size of sediment for a considerable period of time. The sedimentation unit is the deposit made during this time period. When the current changes and a new set of conditions are formed, it is now a new sedimentary unit. a. Lamina - < 1cm thick - Fine layers made of fine- grained sediments - Materials could be varied
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- Forms in very slow currents - They are the thinnest type primary structures. They are made of very fine grained sediments. They could be composed of different types of materials. This explains the
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This note was uploaded on 07/26/2011 for the course GEO 11 taught by Professor Lim during the Spring '10 term at University of the Philippines Diliman.

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sedimentary structures - SEDIMENTARY STRUCTURES Mechanical...

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