Lecture 7 - Sedimentary Rocks

Lecture 7 - Sedimentary Rocks - Envir Sc 1G03: Earth &...

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Unformatted text preview: Envir Sc 1G03: Earth & the Environment Sedimentary Rocks and the Local Area Field Trip Outline Introduction the rock cycle Sediments Sedimentary rocks Depositional environments Stratigraphy Naming of rock units Field Trip Introduction: the rock cycle Igneous, sedimentary & metamorphic rocks sediment ends up i n/near a body of water above surface Below surface LITHIFICATION compress/compact, cementation Change from one type to another with time molten material goes to surface and solidifies What are sediments? Sediments: loose, solid particles that can originate by... 1. weathering and erosion of pre-existing rocks 2. chemical precipitation from solution (usually in water) !"#$%& http://www.geo.uu.nl/fg/palaeogeography/researchprogram '("%$&)%#$&*%+",&-$%.& What are sedimentary rocks? Clastic sedimentary rocks Non clastic (chemical) are made of fragments of preexisting rocks or fossils sedimentary rocks are made of minerals precipitated from solution conglomerate halite (salt) How do sediments change into sedimentary rocks? Sediments become Lithified due to COMPACTION - decrease in rock volume due to weight of overlying sediment AND/OR CEMENTATION - binds grains together with other minerals/components - carbonate (CaCO3) or silica (SiO2) : &!/%0"1"2/2& !"#$%&'($%))can be diagentically altered by the movement of Mg-rich fluids ) through the rock ) Substitution of Mg for Ca ions in rock produce new carbonate )))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))34#42$41"&&& rock called ----------------------> ) )) )) ) Decreases in rock volume and formation of void spaces called "vugs"- shows if i ts dolostone rather than limestone 5602& Clastic Sedimentary Rocks Clastic sediment defined by weathering and erosion of pre-existing rocks particles transported by ice/air/water deposited in sedimentary basins Clastic Sedimentary Rocks Composed of fragments of pre-existing rock OR organic particles such as shells, skeletal fragments (bioclastic) Shale (mudstone) cemented silt and clay conglomerate cemented gravel Sandstone - cemented sand Coquina cemented shell fragments Clastic Sedimentary Rocks Classified according to the size of the fragments they contain " grain size" More energy on the gravel side b/c gravel is heavier - NRG decreasing as grain size decreases Clastic < 0.0039 mm 0.0039 - 0.0625 0.0625 - 2 mm > 2 mm Bioclastic Mudstone Shale Siltstone Sandstone Conglomerate Micrite Calcisiltite Calcarenite Calcirudite Chemical Sedimentary Rocks Formed by direct precipitation of minerals from solution crystalline limestones and cherts evaporite deposits (ex: halite, gypsium) commonly form in arid, tropical environments '("%$&)%#$&*%+",&-$%.& 7%#/$"&& & & Depositional Environments The grain size of sedimentary rocks tells a story about the environment the rock was deposited in! Coarse grains (sand and gravel) require higher NRG in order to be transported (ex: rivers, glacier) Fine grains (silts, clays) settle out of suspension in calm environments - oceans, lakes Braided river sands & gravels Glacial lake clays silts & Depositional Environments Typically, grain sizes are: Coarser - closer to the sediment source Finer - further away from the sediment source What is stratigraphy? The study of layered rocks; in order to understand their composition, origin and changes in space and time )"3/8"1$%(9&&& usually *$+"#$(&,-.)-'/0%),-$))) layered or bedded 1,.$-%)/,11$+)!s)trata, or stratum for single beds &2$)3$-&"/,1)%$45$(/$)'6)1,.$-"(7)"%)/,11$+),)stratigraphic succesion )) strata stratum Naming of Rock Units Distinctive rock units that can be mapped over a l arge area are called formations usually named after a type locality where the rocks were first described Guelph Formation Gasport Member Goat Island Member Eramosa Member Lockport Formation Lockport Formation Clinton Group sub-divided into members formations are lumped together to form groups ) Local Area Field Trip: Geo-Environments Past and Present Field Trip! Friday leaves at 1 pm Saturday leaves at 9 am In front of Hamilton Hall Wear suitable clothing/footwear (no flip flops!) FREE pizza and pop afterwards! &&:';<&=/"#3$(/>& What do I wear? comfortable clothing hiking shoes, sneakers What do I bring? clip board lab assignment pencil blank & graph paper water & snack rain gear ? camera ? How do I prepare? - read the assignment available on Avenue! ) ) Where are we going?&&& & Rock Chapel Tiffany Falls Dundas Arena What will we be doing? Answering series of questions Drawing sketch maps title with date scale north arrow border Legend Things you have to do! 8$,+)*&$$1)9"&.):-"'-)&')&2$)6"$1+)&-":) 92$/0)'();3$(5$)6'-)5:+,&$%)&')/'5-%$) %/2$+51$) ...
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This note was uploaded on 11/28/2011 for the course ENV SCI 1G03 taught by Professor Padden during the Fall '11 term at McMaster University.

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