Stratigraphy/Correlation + Dating Flashcards
what are the 4 types of stratigraphy?
- lithostratigraphy: defined by what its made of (lithic charictaristics
- biostratigraphy: fossil content and what they contain
- sequence stratigraphy: organizing sediments into major packets, allostratigraphy,siesmic stratigraphy
- under surface, good for oils - chronostratigraphy: based on geological time, uses all methods of stratigraphy, define correlate, categorize
what are steno’s 3 principles?
- original horizontality (deposited horizontally)
- principle of superposition (young rocks on top)
- lateral continuity until i. it thins ii. edges of a depression/another sediment iii. edge of a basin is reached
what was neptunism?
werner: all rocks are igneous anf formed in sequence from a global ocean (noah’s ark) - supported by the church
what was catastrophism?
curvier: 6 catastrophies that wiped all of life out (i.e. 6 days of biblical creation - so the church agreed to it!!
what was uniformitarianism?
Hutton!! the other views lacked evidence, so it challenged them - slow erosion process -world must be old as heck - "present is the key to the past" - world is slow and cyclic - igneous rocks came from MAGMA
what is actualism?
the modern version of uniformitarianism in which it allows for short changes
what is an unconformity and what are the 3 types?
gaps in the record of geology (hutton realized this)
period of nondeposition or active erosion
1. angular: tilted, eroded sediments on top, possibly tilted again!
2. non conformity: deposited onto something that wasn’t always sediments
3. disconformity: horizontal deposits (not tilted), but eroded randomly
*** see images of this on slides when this card arrives
whats cross cutting/fault?
cross cutting: invasion of sediment
fault: fracture in the rock that moves occasionally
what is the maximum missing time represented by an unconformity?
oldest possible rock - youngest possible rock!
whats a pluton?
magma cooled into granite/rock
who is james usher?
challenged the ‘young earth’ idea, that earth was 6000 years old, but uniformitariansts didn’t agree cause it wasn’t enough time
who was Charles lyell and what did he find out?
he liked the etna volcano, and discovered that etna must have formed AFTER all these little volcanos surrounding it. since it took thousands of years to come into existence (there are only records of one appearing), all the others must be even older!
-he found old fossils in limestone near etna, and the limestone went UNDER etna
whats a lithostratigraphic formation?
distinct rock with units above/below
must be able to move around and MAP it
dependant on rock type/fossils/structure of sediments
whats a formation and a group?
formation: one rock type or associations of rock types
group: association of formations
distinct but related
what is a facies?
sediments deposited that reflect the environment in which they were being deposited
- sediment type, structure, fossil content all depend on whereabouts
i. e. when talking about sea level, many facies depend on the depth of water, turbulence and size of sediments
whats the change of sediment deposition as you go DEEPER into the ocean?
starts with coarse material, then goes to finer material, then at the bottom you get carbonates (algae secreting skeletons that are dependent on biology and water temperature)
what are the 3 types of sea level change?
- no change, deposits stay in the same type of area
- Transgression (levels rise), using a core sample, the deep material would be at the top and the shallow at the bottom
- facies boundaries tilted towards shore !! - Regression (levels fall) using a core sample, the opposite would be true ^
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what does diachronous mean?
time crossing
what is walthers law?
all facies are laterally adjacent but when sea levels change, they migrate over one another
EVIDENCE FOR THIS:
- facies are distrubuted due to changing conditions
- as conditions change, facies migrate to follow their patterns
- facies can be over top of each other
- verticle rock sucessions allows us to understand sea level change
Formally: facies of conformable verticle sucession of strata were once deposited laterally and adjacent to each other
what are local mechanisms of sea level change?
Crustal Deformation: mountains building due to subduction zone + continental collison
- sea level may fall locally depending on rate
Isosatatic redress: removing ice sheets causes earth to “bounce back” upwards again after being compressed.
- i.e. scotland (regression) and UK (transgression)
what is happening at England’s Temmes?
something to protect england from flooding, but now levels are getting too high to accomodate it, and the bridge can’t protect them much longer!
what is the michegan basin?
sediments deposited into a basin caused it to ‘sag’, which depresses the crust, making room for more sediments, which depress the crust POSTIVE FEEDBACK LOOP
(eventually the process was stopped by the north american plate slammin into european plate)
what are some methods of Global sea level change?
glaciation: ice on top of continents
spreading ridge activity: large ocean ridges displace water as they rise and push continents aside
- basically big long volcanos that cause transgression when they are very active,
- low activity = regression of sea levels
sea levels effect deposition over the entire planet !!
what are ways that sea level can affect deposition over the planet?
- distance travelled by sediments
- areas of deposition
- erosion
- climate
- sediments produced!! all change when sea level rises/falls
