Exam II Flashcards
What is a facies?
characteristics that distinguish a sedimentary rock from others nearby (grain size, lithology, structures)
What influences sediment color?
mineral composition, oxidation, reduction (lack of oxygen), incorporation of organic material
What does grain size indicate about the strength of the current?
large particles - strong current
small particles - weak current
What does grain shape indicate about distance transported?
Angular: recently weathered, close to source
Rounded: long transport distance
What is sorting?
uniformity of particle size
What is the difference between clastic conglomerate, sandstone, and mudstone/shale?
conglomerate: form close to source areas, mountains, fast moving currents, poorly sorted
sandstone: close to/far from source, desert dunes and rivers and beaches, intermediate currents, well sorted
mudstone/shale: far from source, deep marine basins and lakes and floodplains, slow currents
What is the difference between chemical evaporite, carbonate limestones, and organic coal? What environments do they represent?
evaporites: form in water by evaporation/chem reactions, lakes/oceans in arid setting
carbonate limestones: w/ or w/o fossils, chalk, low sediment + photosynthesis, deep marine and continental shelves and reefs
organic coal: compressed remains of plants, swamps and deltas and lagoons
How are sedimentary structures formed? Mud cracks, cross bedding, ripples, graded bedding, trace fossils
Mud cracks: Fractures that form in clay sediment upon drying
cross bedding: a. Layers form at an angle due to the avalanche of sand down the face of a dune (orientation shows current direction)
ripples: Wavy forms in sand that form from currents in water or winds
graded bedding: Grain size changes systematically upward within a single bed, density settling of sediment in water as current energy decreases
trace fossils: a. Structures in sediment made by an organism (not the organism itself but evidence of it)
How are sedimentary rocks used to interpret key environments?
you can apply uniformitarianism to the sedim rocks to interpret past environments and change
Compare alluvial fans, rivers (meandering vs braided), lakes, swamps, desert dunes, loess, glaciers, near shore and continental shelf, and deep water
alluvial fans: angular to rounded poorly sorted gravel and sand, close to source
meandering: finer grained, cross beds, mud cracks, trace fossils
braided: coarser grained (angular to rounded), low vegetation, cross beds
lakes: low energy, filled with mudstones (evaporites if arid), can contain beds, ripples, mud cracks, fossils
swamps: coal, mudstones, shales, low energy
desert dunes: cross bedded sandstone, well sorted, well rounded sand grains
loess: which beds of wind-blown silt (mudstone), associated with glaciers and deserts
Glaciers: poorly sorted sediment and til, glacial outwash (braided rivers)
beaches and continental shelf: well sorted with ripples and cross beds, fossils/shells, sandstone to shale to limestone
deep marine: beds of clays and organisms, low energy, shale and chert
What is stratigraphy?
the study of layers in rocks
What is a basin and how to they form?
Basins are depressions where sediment can accumulate, formed by tectonic processes– faulting and folding of crust
How do facies change vertical and laterally and with changes in sea level?
vertical: through principles of superposition, inclusions
lateral: lateral continuity (also pinch outs and grading into different rock types)
sea level: transgressions and regressions, changing laterally and vertically
What are transgressions and regressions?
transgressions: sea level rise, sandstone on bottom, shale, limestone
regressions: sea level lowers, sandstone on top, shale, limestone
What produces fining up or coarsening up sequences?
Coarsening up: regression
fining up: transgression
What causes global scale changes in sea level?
1) water volume expands when heated
2) ice sheet growth and retreat
3) sea floor spreading
What are the types of stratigraphic correlation?
Lithostratigraphy
Biostratigraphy
Chronostratigraphy
What is a formation?
basic rock unit with distinct upper and lower boundaries that can be mapped
What is the principle of faunal succession?
There is a unique non-repeating pattern of fossils through time
What is the range zone vs overlapping range zone of fossils? How are they used in correlation?
range zone: rock body that represents the total life span of a fossil
concurrent range zone: overlapping ranges of 2 or more species
allows recognition of smaller increments of time, making for more accurate time matching
What are some examples of chronostratigraphy?
numerical ages
volcanic ash
asteroid impacts
rates of deposition
What conditions are best for fossil preservation?
quick burial
hard parts (lol ur dad)
sediment
low oxygen
Which rock type are most fossils preserved in?
sedimentary
What is an articulated vs disarticulated fossils and which is most common to find?
articulated: all bones still attached
disarticulated: bones separated (scavenging, erosion), more common?
What is the difference between permineralization, replacement, carbonization, and molds and casts?
per-mineralization: water + minerals build up in openings, reinforcing original remains
replacement: exchange of original substance with a new mineral
carbonization: soft tissues preserved as thin films of carbon in an impression
molds: imprints left behind by fossil
cast: when molds become filled with sediment
What are some key trends in fossils through time?
- Organisms began primitive and became more complex over time
- Early fossil record contains rare soft bodied organisms
- Fossils hard parts originated as shells, and eventually bones
- Early animal fossils are dominated by marine invertebrates
- Phanerozoic Eon contains unique groups of organisms (and fossils) due to a combination of evolution and mass extinction events
What are pelagic vs benthic organisms?
Pelagic: anywhere in the water column
benthic: on the sea floor
What are key differences between the phyla: Porifera, Mollusca, Brachiopoda, Echinodermata, Arthopoda, Cnideria, Bryozoa, Chordata?
Porifera: porous, anchored in reefs
mollusca: mollusks
brachiopoda: must abundant/diverse, 2 valves, symmetrical within shell
Echinodermata: starfish, sea urchins (spiny)
arthropoda: insects, spiders, lobsters, trilobites, eurypterids, segmented bodies
cnideria: corals, jelly fish, sea anemones
bryozoa: moss animals, twig like
chordata: contains notochord (nerve chord) fish, mammals
Linnaeus taxonomic hierarchy: know kingdom and phylum vs. genus and species.
kingdom phylum class order family genus species
What is Lamarckian evolution (in regards to acquired traits). How is that different from natural selection?
Lamarckian: new features come from “inner want” and can be passed down
natural selection: variation in offspring is what leads to passing of traits
What are the key components of natural selection?
1) Always variation among offspring
2) Offspring with the most favorable traits have the competitive edge for food, shelter, sexual partners
3) Those with favorable traits are more likely to survive and pass those traits on to offspring
What is adaptive radiation in Darwin’s tortoises and finches?
descendent adapts to a particular environment, adaptation in particular environments leads to diversification
what is a genotype, phenotype?
genotype: genetic makeup
phenotype: genotype + effects of the environment
What is DNA and how does cell division occur (sexual vs asexual)
DNA: container of genetic code
sexual division: meiosis (1/2 chromosomes from each parent)
asexual: mitosis, exact replica
What is mutation?
Change of genes spawned by UV light, cosmic rays, chemical changes
What produces genetic variability?
sexual reproduction
What is microevolution versus macroevolution and what are some examples?
Micro: changes in gene frequency on a small scale
(observed in modern bacteria, evolution of resistance)
macro: fossil record shows how species have evolved over time, physical features and behaviors (origin and evolution of types of mammals, variability in different arthropods)
What is a Hox gene?
regulatory genes that control the early development of certain body regions (turned on/off during development)
What is a species and what causes speciation?
species: a group of organisms that have structural, functional, and developmental similarities that can interbreed
speciation: origin of a new species, can be caused when populations are geographically isolated for generations (allopatric speciation)
What roles do mutation and geographic isolation play?
favorable mutations can be spread by interbreeding and geologic isolation can limit the spread of the mutation
What is the difference between phyletic gradualism and punctuated equilibrium?
phyletic gradualism: gradual progressive change
punctuated equilibrium: evolution by sudden advances that punctuate long intervals of little change (stasis)
What is a transitional fossil?
fossils that exhibit traits similar to both a fossil ancestor and its descendants
What are homologous, analogous, and vestigal structures?
homologous: common ancestry but evolved for different functions (divergent evolution, ex: mammal limbs)
analogous: similar function, different ancestry (convergent evolution, ex: wings on insects vs birds)
vestigal: remains of body parts from earlier ancestral forms
What are divergent evolution and convergent evolution?
divergent: common ancestry, different functions
convergent: different ancestry, similar functions
Why are mass extinctions important in evolution and increasing biodiversity?
it creates evolutionary opportunities because habitats become open and new species can fill the niches of previous species
What are some of the characteristics of the Big 5 mass extinctions?
Ordovician: 439 Ma, glaciation
Devonian: 364 Ma, evolution of land plants and changes in ocean chemistry
Permian: 251 Ma, largest (the Great Dying), volcanism
Triassic: 200 Ma, volcanic eruptions from rifting of Pangea
Cretaceous: 65 ma, meteorite
What is the Big Bang?
the theory that the universe began as an infinitely dense primeval atom (a singularity)
What does it mean if galaxies are red-shifted?
they are moving away at an increasingly faster rate (meaning the universe is expanding)
What is the solar nebula theory? How does it explain the distribution and type of planets in the solar system?
The theory that our solar system started as a disk of gases and matter, rotating around a common central mass (Sun)
the solar winds separated denser particles from low density gas (blew light elements outwards)
What is the difference between accretion and differentiation?
accretion: gravity attracting particles
differentiation: density drives the separation of materials
How do we know the Earth has layers? How do we know the core is iron?
Layers: earthquake seismic waves indicate thickness/density of layers
core is iron/nickel: density matches up with seismic readings and it’s more common than gold
What are the different types of meteorites?
Ordinary chondrites: spherical particles of molten droplets
Carbonaceous chondrites: 5% organic compounds
Iron: iron and nickel, from asteroids that have metallic cores
stony iron: least abundant, contains silicate minerals
What is the primary hypothesis of how the moon formed?
Giant impact hypothesis
other theories: fission, simultaneous accretion, capture
What roles do meteorites and volcanoes play in the origin of water?
Carbonaceous chondrites brought in water
volcanic eruptions emit water vapor
Know all the eons, eras, and periods
Eons: HAPPH
Eras: PMC
Periods: COSDC(MP)P, TJC, P(T)N(Q)
What are trace fossils?
a fossil that records an organism’s activity but not the organism itself
