Unformatted text preview: Envir Sc 1G03: Earth & the Environment Sedimentary Rocks and the
Local Area Field Trip Outline
Introduction the rock cycle
Naming of rock units Field Trip Introduction: the rock cycle
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
- 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
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
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
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
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$%(9&&&
*$+"#$(&,-.)-'/0%),-$))) layered or bedded
1,.$-%)/,11$+)!s)trata, or stratum for single beds
)) 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
Goat Island Member
Eramosa Member Lockport
Formation Clinton Group sub-divided into members
formations are lumped together to form groups ) Local Area Field Trip:
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
What do I wear?
hiking shoes, sneakers What do I bring?
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
Legend Things you have to do!
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- Fall '11
- Sedimentary rocks, clastic sedimentary rocks