Geology 106: Exam 4- Kristie Cornell

What are the time periods and periods of the Mesozoic?

245 Million Years ago - 66 Million years ago

Cretaceous

Jurassic

Triassic (oldest)

Mesozoic Era saw evolution of:

Reptiles (dinosaurs) -- "Age of dinosaurs"

Mammals

Birds

Flowering Plants

What did the Breakup of Pangea influence?

Global Climate

Ocean Circulation

Life (isolation)

What was the first stage of the Breakup of Pangea?

During Triassic:

Rifting of Laurasia and Gondwana

What was the second stage of the Breakup of Pangea?

During Jurassic:

Breakup of East Gondwana

What was the third stage of the Breakup of Pangea?

During Cretaceous:

South America and Africa seperate

What was the fourth stage of the Breakup of Pangea?

During Cenozoic: (past Mesozoic)

Greenland separates

What is the Wilson cycle?

Cyclic process of closure and opening of the oceans

How much of the earths surface did Pangea cover?

1/4

What was Pangea surrounded by?

Pantalassa (ocean)

What kind of climate did Pangea have?

dry and arid

rain shadow desert (created when mountain ranges lie parallel to moist, coastal areas)

What were the climate indicators of Pangea?

Evaporites (rocks composed mostly of minerals produced by evaporation of saline solutions)

Red Beds

Desert Dunes

During the Cretaceous:

continents....

warm oceans....

Continents were split apart

Warm ocean currents reach high latitudes

Mesozoic History- Triassic

Continental deposition

Red beds

Mesozoic History- Jurassic

Gulf of Mexico...

Appalachians....

Gulf of Mexico= 1000 m evaporites

Rising sea level

Appalachians= block faulting

Orogeny: W margin

Mesozoic History- Cretaceous

Transgression.....

Transgression:

-Rifting causes increased heat flow

-Reefs

-Interior seaway

Cretaceous Orogeny in West:

Cordilleran Mobile Belts

Rifting produces...?

passive continental margins

Eastern Coastal Region:

Appalachians...

Coarse clastic....

Appalachians eroding

Coarse clastic debris fills intermontane basins

Intermontane basin sediments on coastline

What are intermontane basins?

An intermontane is a feature that lies between mountains:

Basins are formed by run-off sediment from the surrounding mountains

What are normal faults stress type?

Tension!

What are reverse fault and thrust fault stress types?

Compression!

What are Left and Right lateral faults stress types?

Shear!

Normal faults occur at....?

Diverging plate boundaries

Eastern Coastal Region:

Newark Group

Coarse clastics

Up to 6 km thick

Weathering in the Newark Group:

weathering of granitic highlands bordered by fault basins

Terrestrial conditions of Newark Group:

Mud-cracks

Dinosaur footprints

Raindrop impressions

Newark Group Volcanism

Fissure volcanism with ash deposit

Widespread volcanic activity= breakup of Pangaea

Newark Group Volcanism:

How much was covered by basalt?

7,000,000 km^2

Eastern Coastal Region: Late Triassic/Jurassic

Fault....

Atlantic...

Fault block mountains severely eroded

Atlantic grows

Late Triassic/Jurassic:

East coast becomes?

Passive Margin

Gulf Coast Region: Late Triassic

ABOVE sea level

Late Triassic: Gulf of Mexico

Formed when N and S America separated

Gulf of Mexico: Evaporites

Dry area with salt and gypsum deposition

Thickness: up to 1,000 m

Source of salt domes on Gulf Coast

Salt domes

Domelike rock structure that is formed beneath the earth's surface by the upward movement of a mass of salt

Possible oil traps!!

Gulf Coast Region:

Evaporite conditions...

Evaporite conditions eventually vanished - Gulf less restricted

Gulf Coast Region:

Normal marine limestone....

deposited in transgressing and regressing seas

Gulf Coast Region:

Deeply buried under..

Cretaceous and Cenozoic sediments

Gulf Coast Region:

Well known...

by drilling activities of oil companies

Major flooding during Cretaceous:

Appalachian belt remains elevated

Atlantic coastal plains subsided

Subsiding coastal plains:

Alternate...

Alternate layers of marine and terrestrial deposits

Thick wedge of sediments accumulated

Gulf Coastal Region:

Cretaceous Transgression

Rifting causes increased heat flow

Reefs

Interior seaway

Orogeny in W:

Cordilleran mobile belts

Carbonate reefs:

extensive in warm waters

Important reef builders:

Rudists: Coral like bivalves

Porosity and Permeability: reservoir rocks for petroleum

Western Region: Mesozoic Tectonics

North America - Pacific collision = Active Continental Margin

Western Region: Mesozoic Tectonics

1st Orogeny...

Sonoman Orogeny

Sonoman Orogeny:

Triassic: island arc collision

Adds 300 km to continent !!

Western Region: Mesozoic Tectonics

2nd Orogeny...

Cordilleran Orogeny

Cordilleran Orogeny:

North America - Pacific collision

divided into three separate phases called:

1. Nevadan, 2. Sevier, and 3. Laramide orogenies

1. Nevadan Orogeny:

During Cretaceous:

Continued eastward subduction of oceanic lithosphere underneath North America

1. Nevadan Orogeny-

Franciscan Group

AKA 'Melange'

Chaotic mixture of rocks from trench: up to 7,000 m thick

1. Nevadan Orogeny-

Great Valley Group

conglomerates, sandstones, siltstones, shales:

shelf deposits

up to 16,000 m thick

Melange

Jumbled mixture of sea-floor and land derived materials, formed in ocean trenches

Nevadan Orogeny had:

lots of granitic magma emplaced in Sierra Nevada and Idaho

2. Sevier orogeny:

During: Cretaceous

Thrust faults forced blocks of older strata eastward onto younger strata - 100 km of shortening !!

3. Laramide Orogeny

During: Late Cretaceous - Cenozoic

Present rocking mountains are result of this !!!

Mesozoic sediments in Western Cordillera:

Early Triassic

Shallow marine sandstones, shales, and limestones

Mesozoic sediments in Western Cordillera:

Middle Triassic

Regression:

As western shallow seas regressed.. large areas were exposed to erosion

( Continental depositional environments )

Continental Sedimentation:

Chinle Formation

Fluvial, flood plain deposits -- Found: Streams and Lakes

Terrestrial fossils and trace fossils

Petrified wood

Continental Sedimentation:

Navajo Sandstone

Found: Coastal sand dunes

Clean sandstone

Cross-bedded

Coastal dunes

Canyonlands National Park

Near shore / coastal dune environment

Middle Jurassic Sedimentation:

Sundance Sea

West-central part of continent flooded by wide seaway

The Morrison Formation:

regression of Sundance Sea due to Nevadan Orogeny

Terrestrial deposits

Flood plain environment - Meandering Rivers

The Morrison Formation has....

70 species of dinosaurs -- including biggest ever existed

Cretaceous Sedimentation:

Cretaceous Transgression

1/3rd of land now emerged under water

little evidence of glaciation at the time

Volume of new ocean crust formed was high

What is accretionary tectonics?

growth of continent by attachment of terranes

Accretion of Terranes

along a subduction zone can form mountains

What are some of the important resources from the Mesozoic?

Coal in Rocky Mt. states

Gulf coast oil

Louann salt

Uranium

Cooper at convergent plate boundaries

What was the Paleozoic Mass Extinction?

greatest recorded mass extinction ever !!

What are Molluscs and the 3 classes?

Major invertebrates of Mesozoic

3 important classes:

1) Bivalves*

2) Cephalopods*

3) Gastropods*

Molluscs:

What are *cephalopods?

squids and octopuses

nektonic animals, fast hunters

What are the two groups of cephalopods?

Nautiloids and Ammonoids

What are belemnites?

type of cephalopods

good index fossil during triassic - cretaceous

squid-like animal with internal shell

Bivalves that diversified?

oysters and clams

reef-forming nudists

infernal burrowers

What are rudists?

Carbonate reef builders

forms lots of reefs in the Mesozoic

Good place to find oysters and other marine animals in the Mesozoic:

Sundance formation

Why are ancient reefs of interest to the geologist?

They can store oil and gas

also... used as reservoirs

Early Scleractinians or hexacorals:

low mounds in early triassic, later grew larger

early corals were deep water

Scleractinians or hexacorals:

!! All modern corals !!

Solitary and colonial

developed symbiotic relationship with algae

moved into shallow water

What are coccolithophores made of?

calcium carbonate

evolved in Jurassic

What are the two single celled algae's?

Dinoflagellates (triassic - present)

and

Diatoms (cretaceous - present)

Angisperms:

flowering plants !!

"Age of the cycads"

Seed plants without flowers

Decline in Cretaceous

EX: sago palm

Ginkgo:

permian to present

seed plants without flowers

Mammals and birds:

warm blooded vertebrates

Reptiles:

cold-blooded animals with backbones and lungs

What are pterosaurs?

flying reptiles

long wings-small back legs

In all flying vertebrates:

forelimb has been modified into a wing

What are ichthyosaurs?

"fish lizard" -marine reptile

early Jurassic

What are plesiosaurs?

Sea lion like reptiles

late jurassic

What are archaeopteryx?

Jurassic

small wingspan- sharp teeth

link between birds and reptiles

Do birds have teeth?

No

Do birds have claws at their wings?

No