Transcript Geology of Virginia

Geology of Virginia
•
Why?
Pulls together what they already know:
• Rocks
• Plate Tectonics
• Wilson Cycles
• Geologic Structures
• Stratigraphic Principles/Sequence of Events
• Geologic Time
• Map and Cross Section Interpretation
ES.8 The student will investigate and understand geologic processes including
plate tectonics. Key concepts include
• a) how geologic processes are evidenced in the physiographic provinces
of Virginia including the Coastal Plain, Piedmont, Blue Ridge, Valley and
Ridge, and Appalachian Plateau;
• b) processes (faulting, folding, volcanism, metamorphism, weathering,
erosion, deposition, and sedimentation) and their resulting features; and
• c) tectonic processes (subduction, rifting and sea floor spreading, and
continental collision).
Defining Characteristics of PC:
• formation of Earth’s crust and main
bombardment
• first life appears
• first multicellular animals at end of interval
Defining characteristics from Smithsonian site (link on portaportal):
http://www.nmnh.si.edu/paleo/geotime/main/index.html
Grenville Orogeny
Grenville Orogeny As A
Cordilleran (Andean-type) Orogeny
Rocks now exposed in the Blue Ridge
Formed deep below the mountain roots.
Virginia ~ 1 Billion Years Ago
Grenville Mountains Would Have Looked Like
These Modern Andes Mountains
http://www.astro.uni-bonn.de/~maltmann/photgal_cz.htm
Late Precambrian Supercontinent
This map illustrates the break-up of the supercontinent, Rodinia,
which formed 1100 million years ago. The Late Precambrian was
an "Ice House" World, much like the present-day.
Cambrian Rifting
Defining Characteristics of the Cambrian:
• Cambrian Explosion
• skeletonized animals
• early animal diversification
Antietem Sandstone – base of Blue Ridge, Luray, Virginia
Antietem: Quartzites
Protoatlantic DCM
Conocheague: Limestone & Dolomite
Conocheague: Intertidal
Taconic Orogeny
Edinburg Limestone – Page Valley east of Luray: deep water black limestones
Martinsburg – Page Valley east of Luray: turbidity sandstones and shales
Defining Characteristics of Ordovician:
• diversification of marine invertebrate Paleozoic Fauna
• end-Ordovician extinction
• During the Ordovician ancient oceans separated the barren continents
of Laurentia, Baltica, Siberia and Gondwana.
•The end of the Ordovician was one of the coldest times in Earth history.
Ice covered much of the southern region of Gondwana.
Interorogenic Calm
Acadian Orogeny
Defining Characteristics of the Devonian:
• “Age of Fishes”
• diverse land invertebrates and first land vertebrates
• diversification of vascular plants
http://brattahlid.tripod.com/sw3-73webb.htm
http://www.pbs.org/wgbh/nova/link/hist_05.html
Interorogenic Calm
100's of meters
above present sea level
6 5 4 3 2 1
Mississippian
0
Qt.
present sea level
SAUK SEA
6
5
Juriassic
Miss
Ordovicin
TIPPECANOE SEA
4 3 2 1
100's of meters
above present sea level
Silurian Devonian
KASKASKIA SEA
0
Protero. Cambrian
1st ord
er c
urve
ABSAROKA
SEA
Pennsylv. Perm Triassic
falling
Cretaceous
Tertiary
rising
Carboniferous Coal Swamps
http://www.coe.ilstu.edu/iga/IMCanal/IMCanal/coal.jpg
Alleghanian Orogeny
Continent-Continent Collision Orogeny
Himalaya Mountains
http://www.cliffshade.com/colorado/tectonics.htm
Atlantic Rifting
Pre-rifting
Early Rifting
Rifting
Continued Rifting – Opening of Atlantic
Continued Rifting – Opening of the Atlantic
Continued Rifting – Opening of the Atlantic
Triassic Rift Basins
Triassic Dinosaur Footprints from
Eastern North America
The Atlantic Rifting Zone, especially the basins of the Newark Supergroup, are famous for their
reptile footprints. Tens of thousands of Triassic and Jurassic tracks have been found since they
were first recognized in 1836 by Edward Hitchcock. The tracks of Triassic age are especially
important because they document the rise to dominance of the dinosaurs. They are also very, very
well preserved.
Grallator parallelum track from Furnace Hill, PA.
(track found by Mike Szajna and Brian Hartline)
Theropod tracks called Grallator and
Anchisauripus appear in Newark Supergroup
rocks in strata of early Late Triassic age and
become larger and more abundant into younger
strata. The structure of this kind of track
suggests that it was probably made by a small
(?young) theropod dinosaur similar to
Coelophysis.
Reconstruction of Atreipus based on the hypothesis that it
was made by an ornithischian dinosaur. From Olsen and
Baird (1986).
http://rainbow.ldeo.columbia.edu/courses/v1001/10.html
Atlantic DCM
Rejuvenation
Well-preserved layer of material ejected from Chesapeake Bay meteor-strike discovered
http://www.spaceref.com/news/august2004.html