Chapter 11 - The Mesozoic Era

I.	Overview of Mesozoic (245 to 65 million years ago)
	A.  Begins and ends with biotic crises (extinction’s)
	B.  Spans 160 million years, three periods
	    1.  Triassic 245 to 208 m.y.
	    2.  Jurassic 208 to 188 m.y.
	    3.  Cretaceous 144 to 65 m.y.
	C.  Evolution
	    1.  Many new families of plants and animals
	    2.  Two new vertebrate classes (birds and mammals)
	D.  Supercontinent of Pangaea was rifted apart over a span of 150 million years

II.	Breakup of Pangaea:  4 stages (3 in Mesozoic)
	A.  Stage One:  Triassic
	    1.  Rifting and volcanism, normal faulting
		a.  tensional stresses separated N. America and Gondwanaland
		b.  similarly Mexico from S. America
		c.  similarly eastern N. America from N. Africa
	    2.  Sea floor generation in opening oceans (basaltic volcanism)
	B.  Stage Two:
	    1.  Rifting of narrow oceans between S. Africa and Antarctica, Africa and India
	    2.  Massive outpouring of basaltic lava
	C.  Stage Three:  Jurassic-Cretaceous
	    1.  Atlantic Ocean rift extended northward
	    2.  Clockwise rotation of Eurasia
	    3.  Close eastern Tethys Sea (pre-Mediterranean)
	    4.  S. America and Africa split apart
	    5.  Australia and Antarctica remained intact
	    6.  Eastern N. America and Greenland remained intact
	D.  Stage Four:  Post Mesozoic
	    1.  Complete N. America Eurasian split
	    2.  Antarctica-Australia split

III.	Mesozoic History of N. America
	A.  Triassic and Jurassic (E and S areas)
	    1.  Normal fault-bounded basins developed due to rifting:  Nova Scotia to North 
   	    Carolina
		a.  troughs filled with terrestrial sediments and volcanics
		b.  Newark Group (Late Triassic-Early Jurassic)
		c.  Palisades Basalt’s of NJ and NY (190 m.y.)
	    2.  Fall Line:  Boundary of rift-faulted rocks, a prominent physiographic feature
	    3.  Development of gulf of Mexico
		a.  occupied areas opening south of Appalachian-Ouachita folded 
		mountains
		b.  filled with Late Triassic salts and evaporates into Jurassic (indicating 
		avidity); over 1000 m deposited; origin of salt domes today
	B.  Cretaceous (E and S areas)
	    1.  Flooding of coastal lowlands due to high sea levels
		a.  Atlantic and Gulf Coastal Plains inundated as they acted as subsiding 
		shelves at this time
		b.  thick deposits of deltas, barrier islands, shelves, reefs, etc. formed
		c.  Florida:  Shallow submarine bank for limestone’s
		d.  Reefs made of rudist bivalves rimmed Gulf Coastal area in Early 
		Cretaceous
		e.  Extensive chalk deposits of Cretaceous sea due to massive production 
		of microscopic calcareous plankton (coccoliths); creta = chalk
	    2.  Rifting and ocean opening on eastern side led to closure and compression on 
	    the western side of continent; subduction resulted
	C.  Triassic (western areas)
	    1.  Accretionary Tectonics -  characteristics of west coast subduction at this 
	    time
		a.  steeply dipping subduction zone
		b.  volcanic arcs and microcontinents carried to western margin (displaced 
		or allochthonous terrains - as many as 50 now known)
		c.  massive accretion by subduction (including volcanism), obduction and 
		tectonic accretion of displaced terrains
		d.  tectonic collage of displaced terrains may be 70% of total western 
		accretion; termed accretionary tectonics
	    2.  Cordilleran region divisions
		a.  western belt:  Volcanics and siliceous deposits (800 m)
		b.  eastern belt:  Stable interior sediments
	    3.  Sonoma Orogeny:  Permian-Triassic, Nevada
		a.  Golconda arc collided with west coast
		b.  then a west dipping subduction zone
		c.  added 300 km new area to west
		d.  massive thrust faulting
		e.  Sonoma terrain-additional rocks added in accretion
	    4.  Eastern belt deposition
		a.  sandstones and limestone’s (shallow marine, 1000 m in Idaho, early 
		Triassic)
		b.  continental red-bed facies farther east-Early Triassic
		c.  Late Triassic sediments:  Rivers flowed west across area
		d.  Late Triassic Jurassic stratigraphy (Arizona):  Moenkopi Fm. (oldest), 
		Shinarup Fm.,  Chinle and Kayenta Fms., Navajo Sandstone, Wingate 
		Sandstone
	D.  Jurassic-Early Tertiary (western area)
	    1.  Nevadan Orogeny:  Eastward shift in orogenic effect
		a.  formation of convergent melange deposits
		b.  Franciscan belt of California (classic melange)
		c.  great volumes of granodiorite intruded:  Sierra Nevada, Idaho, and 
		Coast Range batholiths
	    2.  Sevier Orogeny:  Mid-Jurassic-earliest Cenozoic
		a.  precedes batholith intrusion
		b.  basement involved tectonics:  Multiple imbricated thrust faults (low 
	 	angle decollement structures)
		c.  mainly seen in NV and UT, also MT, BC, and Alberta
		d.  most famous thrust fault:  Lewis Thrust (65 km displacement)
	    3.  Jurassic and Cretaceous sedimentation
		a.  Navajo Sandstone (Early Jurassic, MT, WY, NV, Alberta); Clean 
		recycled eolian sands
		b.  Sundance Formation (Middle) Jurassic, famous for fossil reptiles):  
		Deposits of the Sundance Sea
		c.  Morrison Formation (Late Jurassic, famous for dinosaurs):  Swampy 
		plain deposits formed as Sundance Sea regressed upon rising of Cordilleran 
		highlands to the west
		d.  Volcanics and Clastics of Border Region (Cretaceous):  up to 15,000 m 
		in places
		e.  Early Cretaceous Seaway:  Marine intrusions leaving deposits south 
		from Arctic Ocean and north from Gulf of Mexico, dry land between two			seaways (UT and CO),  seas withdrew in a Mid-Cretaceous regression
		f.  Late Cretaceous Seaway:  Greatest of marine intrusions (transgressions)
 		connected Gulf of Mexico and Arctic Ocean via epicontinental seaway 
		(Western Interior Seaway); flooded area = foreland basin
		g.  Dakota Group:  Transgressive phase clastics of late Cretaceous Seaway 
		(Great Plains area)
		h.  Niobrara Formation:  Highstand phase carbonates (limestones and 
		marls) of Seaway
IV.	Mesozoic History of Eurasia
	A.  Tethys Seaway history (southern margin of Eurasia)
	    1.  Triassic
		a.  limestone deposition
		b.  highlands developed to north (Vindelician arch)
		c.  New Red Sandstone deposited as clastic wedge
	    2.  Cretaceous
		a.  Africa moves north toward Eurasia
		b.  compression during collision deforms Tethys sediments
		c.  complex overturned folds, thrust faults, and ophiolites develop as a 
		result
		d.  Tethys seaway narrowed and marine transgression linked Tethys with 
		Alpine Sea to north inundating most of Europe
		e.  Opening of Bay of Biscay and Pyrenees uplift
		f.  Volcanism in Himalayan region

V.	Gondwanaland’s Continents
	A.  Africa
	    1.  Early Triassic:  Still joined to S. America
	    2.  Triassic-Jurassic:  Karoo basin filled with continental clastics, then 1000 m of 
	    basalt flows due to rifting
	    3.  Jurassic-Cretaceous:  Stable continent
	B.  Australia and New Zealand
	    1.  Triassic:  Continental masses joined
	    2.  Late Jurassic:  Subduction and sedimentation of extensive immature clastics 
	    in New Zealand
	    3.  Early Cretaceous:  Transgressive sandstones and chalks in Australia
	C.  India
	    1.  Triassic Cretaceous:  Moved continually north
	    2.  Jurassic:  Interior sedimentation (dinosaurs well represented)
	    3.  Cretaceous:  Vast outpourings of basaltic lava in northern regions (Deccan
    	    Traps covering 500,000 km squared, as much as 1 million km cubed of basalt 
    	    makes it Earth’s greatest known outpouring)
	D.  South America
	    1.  Triassic:  3 depositional areas
		a.  western tract:  Turbidites, conglomerates, and siliceous sediments
		b.  eastern tract:  Deeper water carbonates and shales
		c.  southeastern area:  Eolian and fluvial sediments
		d.  lava flows of Karoo-age in southeastern area
	    2.  Jurassic
		a.  widening split of S. America and Africa
		b.  Andean belt deformation and volcanism
	    3.  Late Cretaceous
		a.  climax of Andean orogenesis
		b.  regional uplift
		c.  evaporite deposition
		d.  great outpourings of andesite in volcanic chain
	E.  Antarctica
	    1.  eastern areas:  Continental deposition, volcanic flows, ash beds
	    2.  western areas (Antarctic Peninsula):  Andes-age orogenesis and continuity 
	    with that range

VI.	Economic Resources
	A.  Uranium ores (carnotite)
	    1.  Triassic and Jurassic rocks of NM, CO, UT, WY, TX
	    2.  Situated in sandstones and fossil logs
	    3.  Dissolved originally from host lavas and ash beds
	B.  Fossil fuels
	    1.  Jurassic coals:  Siberia, China, Australia, Tasmania, Spitbergen, N. America
	    2.  Mesozoic oil and gas
		a.  Jurassic and Cretaceous of Middle East and North Africa
		b.  Western U.S., Alaska, Gulf Coast U.S.
		c.  Arctic Canada, Venezuela, North Sea, southeast Asia
	C.  Metallic mineral deposits (orogenic belts)
	    1.  batholithic intrusions in the Rocky Mountains, Pacific
	    2.  gold-bearing quartz veins of "mother load" (California)
	    3.  Cu, Ag, Zn, veins of Butte, Montana and Coeur d’Alene, Idaho mining 
	    districts; Colorado and Arizona’s
	D.  Non-metallic mineral deposits
	    1.  sulfur and salts (salt domes)
	    2.  diamond-bearing intrusions (Siberia and Africa)