Exam 2 Flashcards
(28 cards)
Describe the basic units of the coast range geology.
“3-layer sandwhich”
- Older volcanics in center
- Marine sediments in middle
- Columbia River Basalt on outside
Describe the structure of the coast range geology.
Northward plunging anticline
Describe the 6 major events making up the coastal range’s geologic history.
- Accretion of island chain onto North American continent
- Marine sediments deposited on accreted terrane due to subduction zone jumping westard.
- Cascade volcanoes buried eastern edge existing material.
- Crustal stretching released CRBs from fissures in east.
- “Push” from Juan de Fuca plate causes uplift of Coast Range, folding Coast Range strata into broad arch, with the oldest rocks in center. (anticline)
- Missolua floods covered everything beloq 400’ elevation with blanket of silt
List the 4 types of sedimentary rocks, describe process of formation, and give an example of each.
- Clastic rocks are composed of broken pieces (or clasts) of older weathered and eroded rocks. Classified based on grain size.
Ex: Sandstone, conglomerate, breccia - Biochemical rocks are formed from organic processes that involve living organisms producing the sediments.
Ex: limestone, chert. - Chemical rock forms when mineral components in solution become supersaturated and inorganically precipitate.
Ex: rock salt, gypsum - Organic rocks form from the accumulation and lithification of organic debris, such as leaves, roots, and other plant or animal material.
Ex: coal, oil shale
List some examples of where you would find sediment (gravel, sand, mud) deposited today.
- Gravel:
- Landslide
- Glacier
- Mountain – River
- Alluvial fans
- Pyroclastic flows
- Sand:
- Ocean beaches
- Desert
- Rivers
- Pyroclastic flows
- Mud:
- Delta
- Swamp
- Rivers
- Lakes
- Ocean floor
- Lahar (mudflow mix – diamictite)
- Pyroclastic flows
Describe what grains can tell you about sedimentary rocks.
- Size indicates energy of flow:
- Large grains: high energy
- Small grains: low energy
- Sorting indicates transport agent:
- Well sorted: indicates water/wind
- Poorly sored: indicates ice/ landslide/ mudflows
- Shape indicates length of transport:
- Angular: short transport
- Round: long transport
- Composition indicates source and maturity:
- As distance transported increases, mineral variety decreases (weak grains destroyed, resistant grains remain [quartz])
Describe some sedimentary rock structures/formations and their indications.
- Bedding - well defined planes separating stratigraphic rock from layers above and below.
- Cross bedding - inclined layers formed by wind/river direction
- Graded bedding - (turbidites) sorted by size; created by underwater landslides (turbidity currents) where coarse grains settle first, fine settle last – so: coarse on bottom, fine on top
- Mud cracks - formed as muddy sediment dries and contracts
- Ripple marks - formed by agitation from water or wind
- Fossils
List the 3 depositional environments and the type of sedimentary rocks they produce.
- Terrestrial: conglomerate, breccia, sandstone, siltstone, shales, coal
- Coastal: sandstone, shale, limestone
- Marine: sandstone, siltstone, clay, turbidites, limestone, chert
Describe transgression vs. regression
-
Transgression associated with deposits during rising sea level
(“…oceans transgress onto continents”) -
Regression associated with deposits during falling sea level
(“…oceans regress off continents”)
How many known species are there, and how many estimated are there?
1-2 million described species
10? million estimate species
Describe body vs. trace vs. chemical fossils
- Body fossils – pieces of organisms
- Trace fossils – products of an organism’s behavior (ex: foot prints, “chomp marks”)
- Chemical fossils – chemical traces of past life
Describe some biases of the fossil record.
- Hard parts are favorable
- Marine setting (low energy environment) is favorable (vs. terrestrial)
- Anoxic environments (low O2 – so, no decomposition) favorable
- Cold temperatures favorable
- Invertebrates (due to structure; shell is entire organism) favorable
- While vertebrates tend to “fall to pieces” vertebrae by vertebrae
- Rapid burial circumstances favorable
- Turbidity currents
- Ash falls
Describe the difference between a cast vs. mold
Organisms buried in sediment can dissolve away leaving a mold.
If the space is filled with sediment, an external cast is made.
Identify this organism, and describe characteristics:
Trilobite
- arthropod, has exoskeleton; results in cast of exoskeleton
- broken into three parts (across), and three lobes (up/down)
- very abundant.
Identify this organism and describe some characteristics:
Coral
- Filter feeders
- Colonial organisms; series of “cups” in which organisms live arranged in various ways
- Been around since Cambrian; sometimes denser in population, sometimes less
- Reef corals symbiotic with photosynthetic organisms/ solitary corals can live in deeper waters
Identify this organism and describe some characteristics:
Brachiopod
- Filter feeders; sea water filtered through lophophore
- Two types: articulate (two shells joined together) or inarticulate (two shells not joined)
- Shells are symmetrical, but don’t match
Identify this organism and describe some characteristics:
Bryozoan
- Moss animals; colonial; grows in mats.
- Attached to sea floor.
- Filter feeds.
- Still alive today.
Identify this organism and describe some characteristics:
Graptolite
- Thought to maybe be ancestor to chordates (animals with backbones) (this is debated)
- Filter feeders
- Planktonic (float in upper part of water column)
- Colonial
- Very small
Identify this organism and describe some characteristics:
Crinoid
- “Sea lilies”
- Stem often breaks into pieces
- Still alive today
- Filter feeders living on bottom of seafloor
Identify this organism and describe some characteristics:
Bivalve
- Clams
- Filter feeders
- Two matching shells; but are asymmetrical
Identify this organism:
Gastropod
- Snails
- Coiled shells; not chambered – one continuous spiral
- Can be single planes or highly spiraled planes
Identify this organism:
Ammonite
- Cephalopods
- Coiled, chambered shells
- Control buoyancy or movement by adding water or air to chambers
Describe Sepkoski’s Curve
Based on marine invertebrates; describes diversity increasing over time “in steps” associated with 3 major faunas:
- Cambrian:
- Trilobites and other arthropods
- Organisms living on top of mud
- Little burrowing
- Little predation
- Paleozoic:
- Brachiopods, crinoids
- Stalked fauna
- Burrowing
- Predators
- Modern:
- Extensive burrowing
- Very active predation
- Fewer stalked fauna
Describe the structure of an atom:
- Electron cloud (> 99.9% volume)
- Nucleus (> 99.9% mass)
- Electrons (e) negative charge
- Protons (p) positive charge - # determines element
- Neutrons (n) neutral charge - # determines isotope
- # Protons vs. # neutrons determine stability
- Unstable isotopes are radioactive
