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what do Igneous rocks help decipher about
earth history
-help ID ancient convergent plate boundaries and areas ancient volcanism-help find Absolute dates/ages for sedimentary rocks thur their associated igneous rocks-help decide if plutonic=slow cooling magma=coarse grained texture with lg minerals able to see-help decide if volcanic=fast cooling magma=fine grained texture with minerals to small to see without magnification TERM 2
Metamorphic Rocks help decipher about earth
history
DEFINITION 2 tells us something about the temps and pressures that prevailed in earths crust esp where plates collided and mountains formed - heat- yeild different minerals source =plutons and deep burial- pressure=compact minerals and som recrystalize=smaller and denser in lithostatic pressure= deep burial-foliated(minerals parallel) in differential pressure =convergent- nonfoliated=regional(large elongated areas from pressure, elevated temp, and fluid activity in convergent or it can be div if just temp and flud) or contact(heat and chem flu from igne alter adjacent rocks) TERM 3
Sedimentary rocks decipher about history
DEFINITION 3 -preserve evidence in surface processes responsible for deposition of sediment by water,, wind, glacier, waves and so on-may contain fossils TERM 4
Detrital Sedimentary rocks
DEFINITION 4 made up of solid particles from pre-existing rocksmost common minerals= quartz, feldspar, and clay TERM 5
Rock composition of detrital S. Rocks tell
us?
DEFINITION 5 -rock composition tells area from which the sediment originateddoesn't tell us how deposition took place
Limestones
sedimetary rock made largely of minerals calcite and dolomite (different forms of calcium carbonate)deposited mostly in warm shallow seas, but small amount forms in lakes TERM 7
Evaporites indicate what
DEFINITION 7 arid environments where evaporation rates are high TERM 8
Sediments deposited in high energy stream
will have (larger or smaller) particle size than
those deposited in low energy stream
DEFINITION 8 -high energy= larger particle (conglomerte, sand)-low energy= smaller particle (silt clay) TERM 9
Rounding
DEFINITION 9 smaller particles suspended in water= not usualy rounded- sand after far transport can be rounded-gravel rounds quickly-the further the transport from the source the more rounded TERM 10
Sorting
DEFINITION 10 wind has limited capacity to transport and deposit sediment so its deposits tend to be well sortedglaciers transport anything in path so deposits are poorly sortedwell sorted means transported farther from source then poorly sorted
Contiental
Environment
1)fluvualdesertglacial TERM 17
Fluvial environemnt
DEFINITION 17
- Braided stream= horizontially bedded conglomerte and corss bedded sandstone, mudrocks not common2)meandering stream= mostly mudrocks deposited on floodplains, subordinate but distincitve lenticular sandstones deposited in point bars TERM 18
Desert environments
DEFINITION 18 alluvial fan= poorly sorted conglom from debris flows and sandstone-conglom filled channelssand dune= well sorted, rounded sandstone with large scare cross bedsplaya lake= laminated mudstone/siltstone, evaporites, rock salt, rock gypsum, and others TERM 19
Glacial Environments
DEFINITION 19 outwash= much like braided streams= horizon bedded conglom and cross bedded sandstone, mudrocks not theremoraines= unsorted, nonstratified deposits of sand and gravel (till) TERM 20
Transitional environments
DEFINITION 20 deltabeachbarrier island
Delta Marine environemnt
mudrocks and sandstone in coarsening upward sequences, associated rocks of marine origin, fossils of marine and land dwelling orgamisms TERM 22
Beach
DEFINITION 22 rounded sandstone with variable sorting, commonly with shells or shell fragments, wave-formed ripple marks. and small scale cross bedding TERM 23
Barrier Island
DEFINITION 23 beach- same as before=rounded sandstone with variable sorting, with shell frags or shells commonly, wave-foremed ripple marks, small scale cross-beddingsand dunes= like desert but with sand sized shell fragmentstidal flat=mudstone and sandstone in fining-upward sequences, distinct herringbone corss beding in sand stone TERM 24
Marine environemnts
DEFINITION 24 continental shelfcontinental slope and risecarbonate shelfDeep ocean basinevaporite environments TERM 25
Continental shelf environemnts
DEFINITION 25 (marine)inner shelf= cross bedded sandstone with wave formed ripples, marine fossils, and bioturbationouter shelf= moslty mudrocks with subordinate sandstone, marine fossils and bioturbation
