Geology Exam 2

detrital

composed of fragments of other rocks

quartz, feldspar, clay

vast majority of grains that make up detrital rocks

carbonate

composed of calcium carbonate (CaCO3) and magnesium carbonate (MgCO3)

it’s a crystalline

what does it mean if a carbonate precipitated directly from sea water

warm and shallow areas (ocean, spring-fed lakes, or streams)

where can you find carbonates

evaporite

composed of carbonate, salt, or gypsum

evaporating lake or ocean, with hot/dry climate

where can you find evaporite?

coal

composed of compressed organic matter

swamp with rapid burial and turnover of organics

where can you find coal?

grain size and sorting of detrital rocks

what two things help us identify the texture of sedimentary rocks?

conglomerate

fragments greater than 2mm

sandstone

fragments 2mm-0.0625mm

silt and clay

fragments less than 0.0625mm

sorting

the uniformity of grain size

poorly sorted

many grain sizes, rapid deposition, little time spent in transport

well sorted

only one size, much time spent in transport by wind and water

bedding

tells us thickness, composition, and texture

cross bedding

sloping layers within a rock unit

graded bedding

changes in grain size within a bed

ripple marks

wavy layers and structures

mud cracks

intersecting cracks in mudstone or shale with dry surfaces

the rate at which sediment accumulates

what can thickness of sedimentary layers tell us?

places where water has flown in the past

what type of area do we often find cross bedding, graded bedding, and ripple marks?

where sediments contract, such as dry lakebeds

where can mud cracks form?

Erosion is on the side the wind is coming from, while deposition is on the opposite side (NE)

if wind is coming from the SW, what sides do erosion and deposition occur?

fluvial

environment made from rivers or streams

big and small grains

what type of sediments in a fluvial environment come from fast-flowing water?

only small grains

what type of sediments in a fluvial environment come from slow-flowing water?

braided streams near mountains

fluvial environment that crisscrosses, is fast-flowing, and has small channels

sand and gravel, fine detrital sediments, conglomerates

what type of sediments do braided streams transport?

meandering channels on gently sloping floodplains

fluvial environment that is only capable of carrying small sand and mud

The Red River

what is a real-world example of a meandering channel?

desert

dry environment where sediments get deposited

sand dunes and tall cross beds preserved in sandstone

what are two common features of desert environments

glacial

environment where sediments are deposited by or near ice

unsorted, coarse-grained detrital sediments (conglomerates)

what type of sediments are found in glacial environments

ice can’t sort sediment

why do glacial environments have poorly sorted sediments

melting water

what helps sort sediments in glacial environments?

stratigraphy

the study of layered rock units

they form layers that preserve time

why is stratigraphy mainly used with sedimentary rocks?

conformable rocks

represent a slow, continuous change in sedimentary environments

unconformities

appear as sharp boundaries between layers representing different environments

angular unconformity, disconformity, nonconformity

3 types of unconformities

they show gaps in rock records

why are unconformities important in stratigraphy

facies

environment with characteristic sediments

sandstone accumulating on a beach would be a beach facies

example of facies

marine regression

if sea level falls, facies shift oceanward

marine transgression

if sea level rises, the facies shift landward

Walther’s principle

raising or lowering sea level will result in a facies shift

fine-upward sequence

what does transgression result in, when it comes to rock units?

coarsening-upward sequence

what does regression result in?

it will show water getting shallower with time

how does regression affect stratigraphy?

body fossil

preserved remains of an organism

trace fossil

trace of an organism’s activity such as footprints

rapid burial

fossilization that prevents scavenging and minimizes decompositions

they are the same age

how are fossils related to the rocks they are preserved in

shells

what is the most common fossil

permineralization

fills void spaces with minerals

quartz, carbonates, pyrites

what common minerals are deposited into open pore spaces?

replacement/recrystallization

as tissues dissolve or decompose, they are replaced by minerals

circulating groundwater

where do minerals commonly come from?

carbonization

complex proteins and carbohydrates partially decompose, leaving behind carbon, which remains as a sea le film

carbonized leaves in lake sediments

what is an example of carbonization?

where sediments collect

where does rapid burial have a high chance of taking place?

where they first appeared in rock records and when they went extinct

what helps determine the age of fossils

principle of fossil succession

a technique used to define the relative age of a fossil, by implying that older rocks/fossils are replaced by younger ones

stratigraphic column

chart that shows the different layers of rocks in a specific area

index fossil

fossils that can be assigned to a specific interval of time

abundant in rock record and easy to identify,

key properties of index fossils

small plants and animals

what index fossils are common in sedimentary rocks

Ammonoid

shelled relative of squid/octopi and lived 400-65 MA

they were widespread and lived for a short time

why are ammonites good index fossils

ammonite

ancient creature with a coiled shell

sedimentary basin

area with space for sediment to accumulate

ocean basin

edges of continent or deep marine

fluvial, deserts, glacial

what are the three continental settings?

they stir sediments

how do waves affect sedimentary environments?

wave base

the depth at which wave movement ceases

it gets sandy and we see few fossils

what happens when waves hit bottom?

muddy with many fossils

what happens below a wave base

inner shelf

which shelf does wave action stir sediments

outer shelf

shelf is shallow but below wave base

slope

huge fans of sediment from underwater landslides

turbidite

underwater landslide deposit that usually consists of sand, mud, and graded bedding

deep marine

no stirring action of any kind with very fine muds, metals, and fossil ooze

reefs

animals that secrete carbonate skeletons, and build outward and upward

platform

build up where CaCO3 precipitates from a Ca-saturated water

transitional environment

middle ground between two different types of environments

beaches

sand with complex bedding and shell fragments, where cross bedding and symmetrical ripples occur

lagoons

sand and mud with trace fossils

delta

massive sediment piles where rivers enter the sea

sandstone and conglomerate

in transitional environments, what sediments are above sea level

turbidites and deep marine muds

in transitional environments, what sediments are below sea level

natural selection

survival of the fittest

predation and competition eliminate the less fit from the population

how does natural selection apply to a population

Lamarck thought traits could change throughout an organism’s life, Darwin thought an organism was born with traits due to random chance

what was the difference between Lamarck and Darwin’s theories?

in response to major geologic events

what is a leading cause for extinction and speciation

law of segregation

Each parent passes an allele at random to their offspring, meaning there is a 50% of getting either parent’s genes

law of independent assortment

different traits won’t influence one another

a person having a hitchhiker thumb has nothing to do with having attached earlobes

what is an example of the law of independent assortment