quiz 4 Flashcards
what feature indicates the top of a sedimentary bed, or bed surface, marker?
mud cracks, graded bedding, fossil footprints and scour marks
true or false, obvious sandstone beach deposits overlain by marine mudstone indicate transgression of the sea
true
what are the methods to determine numerical age
-carbon-14 dating
-radioactive decay of uranium to lead
-fission-track dating
-dendrochronology (tree ring dating)
true or false, the oldest rocks found so far in our solar system are 4.57 billion-years-old meteorites, leading scientists to conclude that this is the approximate age of the Earth
True
a mud of fine calcite and/or aragonite shell debris could become which rock?
micrite
what are the names that fit the three descriptions: Age of Mammals, Age of dinosaurs and longest-named geologic unit of time
Cenozoic, Mesozoic, Precambrian
what is the most logical past environment to have produced a deposit consisting of layers of unsorted, unstratified sedimentary coasts, clay-sized to boulder-sized?
glacial valley
before the development of isotopic dating methods, the age of the earth was estimated by?
-counting the age of people within succesive generations as described in the bible
-comparing rates of change on Earth’s surface today with the geologic record
-calculating the rate of cooling of Earth from an assumed initial temperature
-estimating evolution rates from the fossil record
sedimentary rocks can form…
-by the precipitation of minerals from water solution
-by the cementing together of loose grains of preexisting rock
-from shell fragments or carbon-rich relicts of plants
what is the most logical environement to have produced a deposit consisting of layers of well sorted sandstone with cross beddings several meters high
sand dunes
true or false, lithification is a general term used to describe all the physical, chemical and biological processes that make a sedimentary rock from sediments
true
as sediment is transported downstream, away from its point of origin, the particles found in the stream become…
-of greater resistance
-rounder
-smaller
-better sorted by size
uniformitarianism…
is illustrated by scientists’ seeing pillow lava form only underwater, then theorizing that pillow lava found high in the mountains today did nevertheless form underwater
go see pictures q.14
1,3,2,4
what assumption you might use in radiometric age-dating would cause you to underestimate the age of a rock?
the rock had been a closed system since the time it formed, but it had been metamorphosed enough that some daughter product, no parent product, escaped
when sea level rises, the shoreline migrate inland, flooding the land and depositing coastal sediments over preexisting terrestrial sediments. this process is called?
transgression
what is the proper listing of detritus terms, grading from smallest to largest
mud, silt, sand
rocks formed dominantly from the calcium carbonate shells of marine organisms are classified as … and called ….
biochemical and limestone
flint and jasper were prized in early human cultures because…
they broke with conchoidal fracture and thus made good cutting tools
closure temperature is ?
the temperature at which a rock system ceases to interchange parent or daughter product with surrounding material
what geological feature was not formed by sedimentary processes but rather by igneous processes
Columbia River Plateau (LIP), Washington
an organic sedimentary rock originated as decaying plant matter is?
coal
ripple marks on a bedding plane…
could suggest an ancient stream bed or a seashore
a non marine clastic sedimentary rock composed of angular fragments surrounded by matrix is…
breccia
true or false, radiometric dating can be used only if theres some uranium present in the rock
false
a clastic sedimentary rock with clay and silt-sized grains that breaks in thin sheets is called
shale
geologists find a thick sequence of alternating shales and sandstones. the probable depositional environment and interpretation of these are?
deep marine deposits near the continental shelf
indentify the true statement:
-chemical sedimentary rocks are crystalline in texture
-Flint, jasper, agate, and petrified wood are all varieties of the siliceous rock chert
-both chert and limestone may have either chemical or biochemical origin
-gypsum and halite are evaporite minerals
-all of the above are correct
all the answers are correct
ripple marks, dunes, and cross bedding are useful indicators of ?
current direction
True or false, the presence of mudcracks indicates the sediments lithified in deep water
False
