Formation and Types of Sedimentary Rocks: Transport, Deposition, and Diagenesis - Prof. Da, Study notes of Environmental Science

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Sedimentary Rocks

Let’s first look brieflyat how sediments

and soil are transportedfrom source area to siteof deposition.

…^ or as shown below in the Sudan. http://www.funonthenet.in/articles/Dust-Storms.html

Sediment can be transported by

running water

as shown below at the

confluence of a tributary with the Mississippi River. http://www.soils.umn.edu/academics/classes/soil2125/img/erosrtrv.jpg

Now let’s look at howsedimentary rocks areformed.

What is a sedimentary rock?

¾^ Sedimentary rocks arerocks that form on theEarth’s surface either fromsediments, animal and plantdebris, or precipitation. ¾^ They account for about 5%(by volume) of Earth’souter 10 miles ¾^ Sedimentary rocks containevidence of pastenvironments (depositionenvironments, fossils)

Grand Canyon

Pores in a sandstone (poresare stained blue).

Data from drilling ofocean sediments (mbsf =meters below seafloor)^ http://www-odp.tamu.edu/publications/168_SR/chap_06/images/13_f05.gif

mud sand

http://www.kgs.ukans.edu/Publications/Oil/gifs/fig2d.jpg

Oil and natural gas oftentimes reside in these pores! http://pubs.usgs.gov/dds/dds-033/USGS_3D/ssx_gif/oilstn.gif

2) Cementation - gluing together of particles commonly with calcite,quartz, or iron-oxide cement.

http://www.gly.uga.edu/railsback/speleoatlas/SAimage0223.jpeg

3) Mineral dissolution / formation - some minerals dissolve or transforminto new materials that are more stable at higher temperatures/pressures.

http://www-odp.tamu.edu/publications/195_IR/chap_04/images/04_f22.jpg

Zeolite (diagenetic mineralthat grew into pore)^ clay

Shale^ •Mud-sized particles in thin layers thatare commonly referred to as lamina^ • Most common sedimentary rock

Figure 7.

Limina^ in shale

http://www.fredonia.edu/department/geosciences/Lash/fractures/CapSeal/20-31.jpg

Highlighted below are three common environments in which mudstonesare deposited (some lakes, protected lagoons, and deep sea floor) http://www.winona.edu/geology/MRW/mrwimages/sedenvs.jpg

Highlighted below are three common environments in which sandstonesare deposited (rivers/deltas, ocean shoreline, and turbite

deposits which

are sediment-laden flows that come off the shelf-slope environment) http://www.winona.edu/geology/MRW/mrwimages/sedenvs.jpg

Conglomerate / breccia^ •Conglomerate consists largely ofrounded gravels^ •Breccia is composed mainly of largeangular particles. (This term isoftentimes reserved for rocks that looklike conglomerates but were actuallyproduced by deformation)

Figure 7.

Conglomerate

Breccia Figure 7.