Chapter 8 - Early Paleozoic Events

I.	Early Paleozoic Periods (m.y. = million years)
	A.  Cambrian:  570-505 m.y.
	B.  Ordovician:  505-438 m.y.
	C.  Silurian:  438-408 m.y.

II.	Overview
	A.  Broad Sequence of Events (in order)
	    1.  Gradual marine invasion of low continents (first)
	    2.  Wide epeiric (shallow)seas; moderated climates
	    3.  Wide shallow habitats for marine organisms
	    4.  Wide epeiric seas retreated; instability occurred
	    5.  Thick sedimentary kyers and volcanics developed
	    6.  Collisional mountain ranges built (last)
	B.  Plate Tectonic events (in order)
	    1.  Breakup of Rodinia (proto-Pangaea)
	    2.  Oceanic closing and orogeny to form Pangaea
		a.  Taconic orogeny
		b.  Acadian orogeny
		c.  Alleghenian orogeny
		d.  Caledonian orogeny
		e.  Hercynian orogeny

III.	Clues to Paleogeography
	A.  Paleomagnetic evidence
	    1.  Limestone (shallow marine, subtropical)
	    2.  Evaporites (equatorial dry conditions)
	    3.  Lithic sandstone and greywacke (mountain uplift)
	    4.  Arkose (arid conditions)
	    5.  Tillites (glacial deposits)
	    6.  Quartz sandstone (shorelines, deserts)
	    7.  Shales (deep marine)

IV.	Laurentia (N. America) and Gondwanaland (first stage in forming Pangaea)
	A.  Gondwanaland
	    1.  Formed in southern hemisphere
	    2.  Consist of S. America, African, and other shields
	    3.  Drifted south to polar position
	B.  Laurentia
	    1.  Lay on equator
	    2.  Rotated counterclockwise

V.	Continental Framework
	A.  Stable Interior
	    1.  Arches
	    2.  Synclines
	    3.  Basins
	    4.  Domes
	B.  Orogenic Belts (sites of Wilson Cycle)
	    1.  Cordillerian mountains
	    2.  Franklin mountains
	    3.  Appalachian mountains
	    4.  Caladonian mountains (northern Europe)

VI.	Paleogeography of Laurentia (N. America)
	A.  Equator:  North central Mexico to Ellsmere Island, Canada
	B.  Vast epeiric sea (+- 30 degrees latitude; vast carbonate deposits)
	C.  Vast lowlands of Canadian Shield exposed (desert)
	D.  Seaways
	    1.  Appalachian (on east)
	    2.  Cordillerian (on west)
	    3.  Franklinian (on north)
	    4.  Caledonian (on north west)
	E.  Extensive sediment belts
    	    1.  Shales in seaways
	    2.  Limestone's in epeiric seas
	    3.  Quartz sand on shorelines and deserts
	F.  Volcanic mountains:  Texas and New England areas

VII.	Base of the Cambrian
	A.  Sedgwick original base (1835)
	    1.  At top of nonconformity in Wales
	    2.  First, trilobite-bearing fossiliferous beds
	    3.  Later dated 560 m.y.
	B.  New Concept:  Tommotian Stage (1970)
	    1.  Base of Cambrian lowered to 570 m.y.
    	    2.  New stage included fossiliferous rocks above Vendian (latest Proterozoic) 
            nonfossiliferous rocks 
    	    3.  Fossils in new stage:  Porifera, brachiopods, and unknown organisms

VIII.	Cratonic Sequences of Paleozoic
	A.  Sauk Sequence:  Late proterozoic to Early Ordovician
	B.  Tippecanoe Sequence:  Early Ordovician to Early Devonian
	C.  Kaskaskia Sequence:  Early Devonian to End of Mississippian
	D.  Absaroka Sequence:  Pennsylvanian to Early Jurassic

IX.	Early Paleozoic History
	A.  Synopsis of Sauk Transgression
	    1.  Canadian shield eroded for 50 m.y. prior to transgression
	    2.  Gradual transgression covered shield
	    3.  Transcontinent Arch (highlands) became island chain in shallow epeiric sea
	    4.  Transcontinent Arch:  Ontario to Mexico, parallel to Cambrian equator
	    5.  Late Cambrian seas:  MT to NY
	    6.  Cordillerian deposits of Grand Canyon (AZ)
		a.  Tapeats Sandstone (oldest)
		b.  Bright Angel Shale
		c.  Mauv Limestone (youngest)
	    7.  Bright Angel Shale:  Good example of temporal transgression of facies
		a.  Early Cambrian age in CA
		b.  Middle Cambrian age in AZ
	    8.  Early Ordovician regression ended deposition 
		a.  vast continental scale unconformity
		b.  karst topography on carbonate rocks
	B.  Synopsis of Tippecanoe Transgression
	    1.  Initially vast sandstone deposits covering hundreds of square miles (super
    	    mature sands, e.g. St. Peter Sandstone of Midwestern states)
    	    2.  Shallow marine limestone's with vast fauna
		a.  brachiopods
		b.  bryozoans
		c.  echinoderms
		d.  mollusks
		e.  corals
		f.  algae
	    3.  Great organic reefs formed
	    4.  Extensive shales in Queenston Clastic Wedge of Niagara Falls area, NY
	    5.  Landlocked, reef fringed (barred) basins formed
		a.  Michigan Basin (extensive evaporite deposits)
		b.  Appalachian Basin

X.	Cordillerian Region History (western Laurentia)
	A.  Sauk interval
	    1.  Passive margin on opening ocean; deep marine basin on west
	    2.  Western ocean opened; block rotated out; included Siberian region of Asian
    	    continent
    	    3.  Arms of rifts filled with thick sediments
		a.  Belt Supergroup (MT, ID, BC)
		b.  Uinta Series (UT)
		c.  Pahrump Series (CA)
		d.  Canadian Rockies Section (BC, Alberta)
	B.  Tippecanoe interval
    	    1.  Conversion to active margin with subduction (closing phase of Wilson cycle)
    	    2.  Volcanic chain formed along western trench
    	    3.  Trench deposits:  Greywacke and volcanics
   	    4.  Western ocean deposits:  Siliceous black shales and bedded cherts with
   	    graptolites ("graptolite facies")
	    5.  East of subduction zone:  "Shelly facies"  deposited in back arc basins
    	    (fossiliferous carbonates)

XI.	Appalachian Belt History:  Newfoundland to Alabama
	A.  Appalachian trough deformed three times over Paleozoic
	B.  Subdivisions of trough
	    1.  Eastern sediment belt:  Greywacke, volcanics, siliceous shale
	    2.  Western sediment belt:  Shale, sandstone, limestone
	C.  Physiographic regions today
	    1.  Eastern belt:  Blue Ridge and Piedmont
	    2.  Western belt:  Valley and Ridge and Plateau
	D.  Sauk interval
	    1.  Trough was a passive margin on opening ocean
		a.  shelf sediments:  Sandstone and limestone
		b.  oceanic sediments:  Shales
	    2.  Transgression spread deposits westward across craton; thick carbonates
   	    formed on subsiding shelf
   	    3.  Abrupt end with onset of subduction and ocean closure in mid-Ordovician
	E.  Tippecanoe interval
    	    1.  Carbonate sedimentation ceased; platform downwarped by subduction
   	    2.  Thick graptolite black shale and shoreline immature sands spread west
 	    3.  Volcanic flows and pyroclastic beds formed when volcanoes emerged to
	    coast 
	    4.  Rapid closing of eastern ocean (Iapetus); coastal and volcanic arc developed
	    5.  454 m.y.a. Millerberg ash bed formed (1-2 m thick; estimated volume 1140 
	    km3)
	    6.  Taconic orogeny occurred in 3 phases
		a.  first Appalachian mountains built in collision with part of western
		Europe
		b.  compression folded shelf sediments into mountains and Logan's thrust
		formed (48 km displacement)
	    7.  Giant granite batholiths produced by Taconic melting
	    8.  Taconic mountains weathered to form vast sandstone's of PA, WY, OH, NY
	    9.  Great clastic wedges spread westward (age tracks deformation)
		a.  Middle Ordovician (southern Appalachians)
		b.  Late Ordovician - early Silurian (northern Appalachians, Queenston
		clastic wedge)
	    10.  Clinton iron ore deposited in southern Appalachian region near end of 
	    interval
	    11.  Development of Ouachita-Marathon trough; connects Appalachian and
	    Cordilleran troughs (greywackes, shales, siliceous sediments, 10 km thick)

XII.	Caledonian History (Caledonia = Scotland)
	A. Geographic extent:  Scotland and northwestern Scandinavia
	B.  Trans.-Atlantic continuation of Appalachian mountains
	C.  Tectonic History:  Wilson Cycle
	    1.  Opening:  Late Proterozoic to mid-Ordovician
	    2.  Closing:  Mid-Ordovician to early Devonian
	D.  Iapetus Ocean (opening phase)
	    1.  Between Laurentia and Baltica (Europe)
	    2.  Three main facies
		a.  graphtolite-facies:  Volcanics, greywacke, shale
		b.  shelly facies:  Mature sandstone's and fossiliferous limestone's
		c.  eurypterid facies:  Shales with terrestrial arthropods
	E.  Closing phase of Iapetus
	    1.  Caledonian orogeny was result
	    2.  Volcanic beds:  NW England, Greenland, Norway
	    3.  Climax of orogeny:  Late Silurian to Early Devonian
		a.  Norway - most intensive deformation
		b.  England - least intensive effects
	    4.  Old Red Sandstone:  Clastic wedge deposited south and east of Caledonian
	    mountains (area known as "Old Red Continent")
	    5.  Old Red Sandstone analogue to Queenston clastic wedge
	    6.  Greenland-Spitbergen sequence (10 km thick): Shows Wilson cycle
	    stratigraphy of Iapetus

XIII.	Ural Seaway History
	A.  Initially seaway separated Russian platform (west) from Angaran shield (east)
	B.  Russian platform stratigraphy:  Shelf carbonates, sandstone's, shales (thinning
	toward interior)
	C.  Angaran shield stratigraphy:  Deep marine trough turbidites, shales, volcanics
	D.  Wilson Cycle in seaway
	    1.  Opening phase:  Early Cambrian to Late Silurian
	    2.  Closing phase:  Silurian/Devonian to Late Permian
	E.  Age of volcanics, mafic intrusions, and folding all closing phase

XIV.	Asian continental history
	A.  Encompasses 9 microcontinents with narrow seaways (like Uralian seaway)
	between them
	B.  All seaways began closing phase during Early Paleozoic
	C.  Asia assemblage completed in Late Paleozoic
	D.  Characteristics of Asian orogenic belts
	    1. Narrow zones of high pressure metamorphism
	    2.  Ophiolite zones
	E.  Some deformation continued into Triassic and Jurassic

XV.	African history:  Mid to late Ordovician
	A.  Mid-Ordovician:  Africa "upside down" relative to orientation today; located
	near S pole, moving S
	B.  Late Ordovician:  S polar ice cap covers 1000s km2 (is now Sahara desert
	region)
	C.  Evidence of glaciation
	    1.  Glacial striations on Archean granitic and Cambrian sandstone (10 + km
	    long)
	    2.  Tillites
	    3.  Outwash, moraine, meltwater channel deposits over 100s km2 on shield
	    rocks

XVI.	Australian history
	A.  Rocks of Tasman Trough (belt):  Late Proterozoic to Ordovician
	    1.  Mature sandstone (oldest):  Stability
	    2.  Greywacke and volcanics:  Instability
	    3.  Sorted sandstone and limestone (younger):  Stability
	B.  Tasman Trough connected laterally to several others
	    1.  Andean trough of western S. America
	    2.  Cape trough of South Africa
	    3.  Transarctic trough of Antarctica
	    4.  New Zealand trough

XVII.	Early Paleozoic Climates
	A.  Transgressions = mild climates, windswept low terrain's
	B.  Regressions and orogenic episodes = harsher more diverse climates; winds
	diverted by mountains
	C.  Earth rotation was faster (days shorter, tidal effects greater)
	D.  No land plants
	    1.  solar radiation reflected, not absorbed
	    2.  severe temperature differences resulting
	E.  Rapid changes in solar energy output:  Temperature effects dramatic
	F.  End of Late Proterozoic glacial cycle:  Cool beginning for Early Paleozoic
	G.  Melting polar caps = rising sea levels and warming
	H.  Equatorial position = tropical climates for Laurentia, Baltica, and Antarctica
	I.  No ice caps = warm polar seas
	J.  Ordovician reefs flourished +- 30 degrees latitude
	K.  Cross bedding in desert sand shows wind blew NE to SW across eastern
	Laurentia (opposite of today)
	L.  Silurian temperature zonation
	    1.  glacial deposits above 65 degrees latitude
	    2.  reefs, evaporites, eolian sands below 40 degrees latitude
	M.  Ordovician sea levels and biotic extinctions
	    1.  African glaciation lowered sea level and cooled global temperatures
	    2.  End Ordovician extinctions in many families
		a.  bryozoans
		b.  tabulate corals
		c.  brachiopods
		d.  sponges
		e.  nautiloid cephalopods
		f.  crinoids
	    3.  Specific physical effects
		a.  loss of epeiric sea areas
		b.  lower sea levels
		c.  erosion of vast areas
		d.  cooling tropical seas

XVIII.	Early Paleozoic Paleogeography
	A.  Late Cambrian
	    1.  Major land areas at low latitudes
	    2.  Well connected global ocean
	    3.  Main continents (4)
		a.  Kazakhstania (east Asia and northern Iran)
		b.  Siberia
		c.  Baltica (Europe)
		d.  Laurentia (N. America)
		e.  Gondwanaland
	    4.  No land areas N or S of 60 degrees (polar oceans)
	B.  Ordovician - Silurian
	    1.  Major shift of Gondwanaland (largest continent) to south polar position
	    2.  Baltica circled and moved toward Laurentia (started closing Iapetus Ocean)

XIX.	Mineral Resources
	A.  Slates and building stones of NJ and PA
	B.  Marbles of New England
	C.  St. Peter Sandstone (glass making) of Midwestern USA
	D.  Silurian salt (NY, MI)
	E.  Silurian iron ores (Newfoundland to NY to AL)
	F.  Petroleum in sedimentary basins (Ordovician and Silurian)
	    1.  OH, OK, TX
	    2.  Western Europe