Geology Final

Marine Photosynthesis is restricted to the:

Photic Zone

Rocks are solids never made of several mineral crystals

False

According to Steno’s Principles of Superposition, which of the following is true:

Sedimentary layers appear in a stratigraphic sequence such that the oldest sediments are at the bottom and the youngest are at the top

If a shale was compressed and heated such that its mineral grains aligned and recrystallized without melting, what type of rock would the resulting solid be?

Metamorphic

If presented with a stratigraphic sequence that included, from bottom to top, a deep-sea limestone, shale, siltstone, and sandstone containing trace fossils representing shallow water, how might we interpret the history of environmental change?

Marine regression

Which of the following would we consider events in “Earth History” that can be addressed through historical geology?

• Indian subcontinent colliding with Eurasia

• A lake drying up and leaving an evaporite flat

• A river meander getting cut off and forming an oxbow lake

Which of the following are qualities of a good index fossil?

• Organism existed for a short amount of time

• Extinction of the organism took place quickly

• Organism had a global geographic range

If a sandstone was melted to a liquid state and resolidified, what type of rock would the resulting solid be?

Igneous

Which of the following statements would be an example of uniformitarianism?

Rivers deposit sand which becomes sandstone in the present, therefore ancient sandstones could have originally been sand deposited by ancient rivers

Of the following minerals, which would you expect to be most common in the Earth’s crust?

Feldspar

Continents at and near the equator receive a lot of rainfall relative to the more desert-dominated regions to the north and south of that wet tropical zone. Which of the following accounts for this higher precipitation around the equator?

Hot air rises at the equator and drops moisture as it does so

Which of the following may be indicative of the facies of a sandstone?

All of the above

Which of the following interpretations might we make if we find a stromatolite preserved in sedimentary rock?

Prokaryotic organisms were active at the location at the time of formation

Which of the following is an example of evolution by natural selection?

A group of snakes are less likely to be eaten if they are darker in color, as predators remove snakes of lighter colors, the population shifts towards darker colors overtime

Geologic Eons are divided into Eras. Which of the following are Eras most directly divided into?

Periods

Which of the following are among the defining characteristics of minerals?

• Naturally occurring

• Crystalline structure

• Solid

• Inorganic

• Relatively consistent chemical composition

Silicate minerals are defined by containing tetrahedral molecules of SiO4 (sometimes also expressed as SiO2).

True

Which of the following processes represents the way that minerals form in an igneous rock?

Freezing

In what type of environment should we expect asymmetrical ripples to form on the surface of a body of deposited sediment?

In water that is flowing one direction, like a river or stream

Cnidarians are never preserved in the sedimentary record because they do not produce mineralized skeletons.

False

Which of the following was the most recently acquired piece of evidence for plate tectonics?

Mapping of the seafloor capturing and measuring spreading at mid-ocean ridges

Continental crust is thinner and more dense than oceanic crust

False

What tectonic setting exhibits the highest concentration of earthquakes?

Convergent boundaries

What would the structure be called if there is a linear fold with rock layers dipping away from the central fold axis?

Anticline

Which of the following is the largest reservoir of water?

Groundwater

In the process of evapotranspiration, where is water moved to and from?

From soil to the atmosphere

Which of the following would result in the drawdown of carbon dioxide from the atmosphere (even if somewhat indirectly)?

Weathering of continental rocks

In a case of eutrophication, excess dissolved nutrients contributes to the depletion of oxygen in water.

True

Greenhouse gases in the Earth’s atmosphere contribute to warming of the Earth by absorbing are reradiating long-wave radiation that was previously radiated by the Earth’s surface (having already absorbed short-wave radiation from the sun).

True

What of the following types of surface should we expect to have the highest albedo?

Glacial ice

Which can serve as proxies for climate conditions in the distant geologic past?

Fossils, rocks that form in specific climates, stable isotopes in mollusk shells

How are isotopes of the same element different?

Different number of neutrons

If for a given radioactive isotope 2 half-lives have gone by, what proportion of the original parent materials is still present?

25%

Uranium-lead dating used on a grain of the mineral zircon found in a sandstone would tell us which of the following?

The time since that zircon grain reaches its closure temperature as it cooled from melt

Paleolatitude can be recorded in rocks that contain evidence of magnetic inclination.

True

The original environment in which the precursors to coal form are places with:

High precipitation

Most meteorites are approximately 4.6 billion years old

True

Which of the following contains the oldest crust?

North-eastern Canada

Which is NOT true of prokaryotes?

They are more restricted in terms of the types of metabolism they can exhibit relative to eukaryotes

Which is most likely a place for life to have originated on Earth?

Hydrothermal vents

What describes tectonic settings of the coastlines of Laurentia during the Cambrian Period?

Passive margins all the way around the continent

Coastlines of Laurentia during the Ordovician Period?

A subduction zone one one side of the continent and passive margins around the rest of the coastline

Silurian Tectonics

• Salinic Orogeny

  • Follows Taconic Orogeny

  • Microcontinents collide with Laurentia

  • Now, Laurasia

Devonian Tectonics

• Acadian Orogeny

  • Andean-type subduction

    • Oceanic crust subducting under continental crust → causes crustal thickening → uplift

  • Continues to uplift “Appalachian” region

Carboniferous Tectonics

• Beginnings of the Alleghanian Orogeny

  • Gondwana collides with Laurasia → Pangea

  • MASSIVE uplift

  • Himalayan-scale mountains

    • Similar scale to how to mountains would be like during this period

Permian Tectonics

• Alleghanian Orogeny continues

• Pangea is built

Triassic Tectonics

• Rifting of Pangea has begun

• Pangea beings to rift

• elongated lakes at rift basins

Silurian Climates

• deglaciation

• high sea levels

• extensive shallow marine environments

Devonian Climates

• warm through most of the period

• Glaciation becomes prominent at south pole (Gondwana) toward the end of the period

  • ice cap forming again on Gondwana

• Drawdown of CO2 causes south pole glaciation at the end

Carboniferous Climates

• Generally warm temperatures

• Beginning in Pennsylvanian, temps drop and:

  • Glacial-interglacial cycles begin

  • Milankovitch forcing

Permian Climates

• was a global icehouse

• large igneous province volcanism (short period of low viscosity volcanic activity) —> influx of atmospheric carbon

• temps and ocean acidification goes up

Triassic Climates

• hothouse

• Pangea is one giant desert

Cause and Mechanisms of end-Permian mass extinction

• flood basalt volcanism/LIP erupts through peat and coal —> a lot of burning and CO2 release

• warming melts ice (less reflectiveness = more heat absorption), destabilizes permafrost and releases methane, and causes forest fires —> WARM

• sea levels rising —> loss of coastal habitat

• ocean acidification via CO2 —> no one can calcify and reefs collapse

• Algal booms via CO2 —> eutrophication and suffocation of bottom dwellers

• Acid rain kills plants —> desertification

• warming that is reducing ice/snow

• losing ice caps

• reflectiveness of Earth is lower

• losing methane hydrates

• forests have been prevalent and common for a whole —> warming = forest fires

• fires are much more common due to warming

• carbon tied up in biosphere is now also becoming released at this time

End-Permian Mass Extinction

• Compounding Effects:

  • rapid warming —> sea level rise —> habitat loss in coastal and near-shore environments

  • carbon dioxide dissolved into ocean —> ocean acidification —> marine organisms can’t calcify anymore —> reef collapse

  • carbon dioxide serves as fertilizer for marine phytoplankton —> algal blooms —> choke out light and dissolved oxygen in body of water —> causing other organisms to suffocate

• hydrogen sulfide emissions and desertification

Effects of the rise of Devonian forests

root systems become deeper and more complex —> better at retaining sediment

Late Paleozoic to Early Mesozoic Life

• Colonization of land

  • Devonian forests

  • Arthropods (millipedes, centipedes, arachnids) move onto land in Silurian/Devonian

Early Devonian Trees

• taller (~1 meter), a bit more complicated

  • larger (not very large)

• reproduce by spores, not seeds

  • produce individual cells

  • prone to desiccation and starvation

  • spores have to be present in a climate

• can only live in moist environments

Late Devonian Trees

• trees become common

• widespread forests

  • forests become ecologically significant —> trees

• no seeds yet — can’t move into dry habitats

ex.) Archaeopteris —> A 12 m tree that formed early forests (Late Devonian Forests)

Arthropods

• move onto land in Silurian and Devonian

• Millipedes, centipedes, arachnids, insects

  • whole bodies under exceptional conditions

Major evolutionary developments to facilitate life on land

• lobefin fish had fleshy, muscular appendages at bases of fins —> tetrapod ancestors

• stem tetrapods: amphibians, some aquatic some terrestrial, but had eggs in water

• Ammonite eggs allow tetrapods to move inland

Lobefin Fish

• ancestors of tetrapods (land vertebrates)

• fleshy, muscular appendages form bases of fins —> arms and legs

• modern coelacanth, lungfish

Stem Tetrapods

• amphibians

  • lay eggs in water

  • breathe air as adults

  • not much like modern amphibians, which appear in the early Mesozoic

• some were more aquatic, some more terrestrial

• common in Carboniferous-Permian

Outcomes of end-Permian mass extinction

• LARGEST EVER

• delayed biotic recovery

• reefs eliminated

• reduction in size of many marine taxa

• resurgence of stromatolites

• devastates Paleozoic fauna, modern fauna survived and took over

Permian Mass Extinction

• largest ever

  • ~83% of marine genera went extinct

  • ~70% of terrestrial vertebrate species go extinct

  • plants and insects affected too (loss of plants and insects)

• extinct

  • trilobites

  • rugose and tabulate corals

  • major groups of brachiopods, crinoids, bryozoans, ammonoids, therapsids, and reptiles

• 250 mya

• devastates members of the Paleozoic Fauna

• the Modern Fauna survived well and took over in its aftermath (although it was present before, too)

• the living fauna consists of the survivors of this extinction

Effects of Extinction in Permian

• delayed biotic recovery: millions of years of low diversity

• reefs eliminated

• reduction in size of many marine taxa

• resurgence of stromatolites

Features of rocks of Newark Supergroup

• rift basins on East Coast

• Fluvial facies: immature (poorly sorted, large grains), Arkosic sandstones

• Ripple marks and mudcracks —> shallow waves and drying

• Basalt ridges from Central Atlantic Magmatic Province (erode slower than other rocks)

• East Berlin Formation: red mudstone and sandstone (lakes) and dark shale (deeper)

What do the rocks tell us about tectonic and geologic history of the East Coast (Newark)

• North America is rifting from Pangea

• Rivers change direction and lakes form, causing sediment to accumulate in wedge shapes

• Climate change in East Berlin Formation: lakes changing depth

• Volcanic activity from Central Atlantic Magmatic Province

• Fault occurring east ward

• Basin became more steeper

• East side is doing the faulting = more steep

• Rifting occurring at East

Fossils of Newark Supergroup

• Invertebrates (clams, insects)

• Fish

  • living in freshwater

  • Hartford Basin Fish

• Terrestrial vertebrates: lots of dinosaur tracks but few bones

  • bones dissolve in acidic conditions

  • tracks remain as long as they are undisturbed, sediment fills in and creates a cast

  • Early Jurassic: lots of dinos, some small crocs and lizards

    • Plateosaurs, lesothosaurs, coelophysis, dilophosaurs

• Bone dissolve under acidic conditions

• Require particular chemical conditions in the sediment for preservation

• footprints are basically sedimentary structures

• if the sediment isn’t disturbed, the print will remain

  • little bone material

  • footprints don’t require specific chemicals for preservation

Jurassic Tectonics

• rifting of Pangea

• Beginnings of Sevier Orogeny in Western NA

  • subduction

  • thrust belt (scrunching up of crust)

    • shallow —> sed rocks that are deposited and being thrusted

  • Andean-style volcanism

    • small, narrow oceanic basin

    • going farther south

Cretaceous Tectonics

• Atlantic widens

• Tethys narrows

• Laramide Orogeny

  • NA Carton fractures

  • Intense crustal thickening

    • Fracturing at depth —> new reverse fault

• a lot of land area exposed

• Marine fossils on land far away from ocean now —> due to the stretching and sea level over time

Paleogene Tectonics

• Atlantic continues to widen

• Tethys continues to narrow

• India on collision course with Euraisa

Jurassic Climates

• generally warm and humid

• deserts and seasonally wet climates common on large continents

  • semi-arid climate still

• Triassic deserts have been divided

Cretaceous Climates

• lots of coastlines and shallow seas

• Deccan Traps volcanism at end

Paleogene Climates

• global greenhouse conditions

• warm and humid relative today

• Paleocene-Eocene Thermal Maximum (PETM) —> spike in temp followed by decrease

Causes of K-Pg mass extinction

• Chicxulub impact and Deccan Traps volcanic event caused big environmental changes

• Chicxulub caused:

  • massive dust cloud: blocked sun —> loss of primary productivity and global cooling

  • greenhouse gases released —> warming

  • vaporization of sulfur —> acid rain

  • widespread wildfires

  • tsunamis

Chicxulub Crater: Identified in the late 1980’s by geophysical imaging and drilling. Called the “smoking gun.”

Chicxulub impact: a ~10 km diameter asteroid triggered environmental disruptions

Evidence for asteroid impact

• Iridium anomaly: 300 times normal concentration

• Shocked quartz: high pressure generating parallel fractures

• Glassy microspherules: rock is melted on impact and sprayed and freezes in air as drops

Iridium Anomaly

• Tertiary

• Cretaceous

• 300 times the normal concentration of iridium

• Rare in the Earth’s crust but common in some asteroids

  • common in concentration in asteroids

• The K/T iridium anomaly has been found in over 100 localities around the world. Such anomalies have proven to be extremely rare in general in geologic time

Deccan Traps volcanic event

• large scale volcanic event over India

• Carbon gases released —> greenhouse effect

• Hydrogen sulfide gas —> acid rain and lowered temps on short scale

• variable climate

Deccan Traps

• Outgassing

• Acidification

• Variables Climate

  • Thickness > 2000 m

  • Area ~ 500,000 km²

  • Volume ~ 1.5 million km³

Jurassic Plants Gymnosperms and spore-bearers

• conifers

• cycads

• ferns horsetails

Angiosperms

• flowering plants

  • showing up in late Cretaceous

• many are pollinated by animals, esp. insects

• insects diversify along with angiosperms

• first fossils from the Early Cretaceous

• Common in the Late Cretaceous

• Dominant in many ecosystems in the Cenozoic

Sauropodomorphs

• Prosauropods —> sauropods

• smaller four limbs —> heavier four limbs (heavier bodies, longer tails and necks)

Therapoda

• Bi-pedal Dinosaurs

• Carnivores (in Mesozoic)

• start to get birds

Feathers on Theropods (Caudipteryx)

• feather visible on tail

• preserved feathers

• feathers on various dinosaurs

Herrerasaurus

• traditionally considered a theropod

• look like theropods, and were included with theropods

Ornithischia

• bird-hipping dinosaurs

  • sub set

• getting our build dinosaurs, frills, horns, prominent back plates/spikes

• birds evolved from lizard-hipped dinosaurs

Psittacosaurus

• an ornithischian (ceratopsian) with feather-like structures. Was this ancestral dinosaur characteristic?

• doesn’t have the frill

• small —> size of a small dog

• preservation of hair-like quills

  • eventually yields feathers

Ornithischia versus Saurischia

• Ornithischia (bird-hipped): a branch of the pubis bone points backwards, resting against the ischium, increasing the space for intestines

• Saurischia (lizard-hipped): pubis points forward, except in the bird clade

  • point forward

Archaeopteryx

• Late Jurassic

• Earliest known theropod with powered flight (= first bird)

  • able to fly short distances —> not like modern birds

• had flight feathers, but would not have been a skilled flier relative to modern birds

• retains many theropod traits (teeth, long tail, unfused wrist and ankle bones, etc.)

• soft body features

Cretaceous Birds

• more and more “bird-like”

• Late Jurassic

• Getting more like modern birds

• tail features

• aquatic life

• propelling off of feet, not with wings/features

Pterosaurs

• Late Tri-Late Cretaceous

• Archosaurs — but direct ancestors unknown

• Lightly built with air spaces in bones and powerful flight muscles

• teeth well-suited for catching fish

• sometimes preserved with scales in their stomachs

• birds were light in order to be able to fly

• some had teeth, but more beak-like structures

Mammals

• mostly small and egg-laying mammals

• fossil record consists mostly of teeth

• By the Cretaceous, there are marsupial and placental mammals (non-egg laying)

  • show up in Mesozoic

• Diversify after the K-Pg extinction

Cretaceous Plants as Before, Plus Angiosperms

• Pollination by animals may have led to faster speciation

• produce seeds more rapidly than gymnosperms — can reproduce faster. Allows annual life cycles, colonization in unstable environments, “weedy” life habits

• should have feathers

• angiosperms

Rudists

• bivalves that look like corals

• formed mounds or reefs

• show up in Cretaceous period

• Grown asymmetrically

• resting on sift sediment

• growing in numbers producing reefs

Turtles and Crocodiles in the Jurassic and Cretaceous

• common as aquatic and semi-aquatic predators

• successful in seas and estuaries

• very large turtle bones were found

Other Mesozoic Marine Reptiles

• Ichthyosaurs: Early Triassic-Late Cret

  • fish like

• Plesiosaurs and Pliosaurs: Late Triassic-Late Cret

  • large flippers

• Mosasaurs: Late Cret

  • related to lizards and snakes

Teleost Fish

• dominant modern group

• Radiate in Meso-Ceonozoic

• Maneuverable

• Mobile jaws improve prey capture/feeding

Body Size of Marine Animals

• mean size goes up from Paleozoic to Cenozoic

• large animals getting larger

Diversification of Modern Phytoplankton

• theory: more food —> larger, more active animals and more predators

Cretaceous Extinction

• almost 50% of marine animal genera died out