GEOLOGY OF NATIONAL PARKSSC 211

JOHN BUSH

NOVEMBER 15, 2015

Rodinia1.3 BY – 650 MYA • First “confirmed” Supercontinent

• Formed from dispersed remains of Columbia and accretion of smaller land masses

• Formation created new shallow seas• Grenville Orogeny is an important part of

Rodinia formation

1.3 – 1.1 MYA 750 MYA

SuperoceanMirovia

Ur??

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Pangaea335 – 175 MYA

• Latest and best documented Supercontinent• Formed from collision of Laurasia and

Gondwana• Began to break apart ~215 MYA and continues

to do so today

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DVDACADIA’S HIGHLANDS

AND ISLANDS

GEOLOGY (IS ABOUT) ROCKS

• Rocks are solid mixtures (mostly) of minerals • Brittle—break under stress• Ductile—flow under stress

• The properties depend on the rocks’ chemical composition & physical structure and on conditions of temperature and pressure

• The properties of rocks can tell a geologist the rocks’ history• How and when did they form?• What did they form from?• How have they been modified since they were formed?

• The history of a region’s rocks reveal the geologic history of the region.

SOME WAYS TO TALK ABOUT ROCKS

• Conditions of formation• Igneous—plutonic, intrusive, volcanic*• Sedimentary*--clastic, biochemical, chemical (diagenesis)• Metamorphic—foliated, non-foliated

*Form initially on the Earth’s surface

• Composition of dominant minerals• Sodium, potassium, calcium, aluminum silicates (sialic, felsic)• Abundant iron, magnesium silicates

• Mafic--dense• Ultramafic—denser

• Carbonates, oxides, sulfates, chlorides, sulfides, phosphates

• Subcategories are based on physical and optical properties and on texture

SOME ROCKS OF THE SHENANDOAH/GREAT SMOKY/ACADIA NATIONAL PARKS

• Sedimentary• Mudstone/Shale • Sandstone• Conglomerate/ Breccia• Limestone/ Dolostone

• Igneous• Granite (felsic, sialic)• Basalt (mafic)• Peridotite (ultramafic)

• Metamorphic• Gneiss• Slate• Greenstone• Marble

MUDSTONE/SHALESEDIMENTARY/CLASTIC

SANDSTONESEDIMENTARY/CLASTIC

CONGLOMERATE/BRECCIASEDIMENTARY/CLASTIC

BRECCIA

CONGLOMERATE

LIMESTONE/DOLOSTONESEDIMENTARY: BIOLOGICAL, CHEMICAL

LIMESTONE

DOLOSTONE

IGNEOUS ROCKS

•Granite-like (Felsic, Sialic)

•Basalt-like (Mafic)

•Olivine-like (Ultramafic)

FELSIC IGNEOUS ROCKSFORMS OF “GRANITE”

• Volcanic—Rhyolite—lava, ash, tuff, pumice, glass (obsidian)

• Intrusive -- Rhyolite

• Plutonic -- Granite, Granodiorite

PLUTONIC FELSIC IGNEOUS ROCKSGRANITE AND GRANODIORITE

FORMS OF “GRANITE”

PUMICE RHYOLITEOBSIDIAN

FORMS OF BASALT

• Volcanic – Lava, ash, tuff, tachylyte

• Intrusive – Diabase (Dolerite, Microgabbro)

• Plutonic -- Gabbro

MAFIC IGNEOUS ROCKSFORMS OF “BASALT”

LAVA

DIABASE GABBRO

DIABASE ASH

LAVA

METAMORPHIC ROCKS

QUARTZITE MARBLE

METAMORPHIC ROCKS

SLATE GNEISS

METAMORPHIC ROCKS

MUSCOVITE SCHISTNOVACULITE

METAMORPHIC ROCKS

GREENSTONE EKLOGITE

ULTRAMAFIC ROCKS

KIMBERLITELHERZOLITE

QUARTZ

• Macrocrystalline--milky quartz, rock crystal, amethyst

• Microcrystalline—chalcedony (agate, onyx, carnelian)

• Cryptocrystalline—chert, flint, jasper, novaculite

• Amorphous -- radiolarian chert, opal

MASSIVE QUARTZ VEINS

QUARTZ: CHALCEDONY

CRYPTOCRYSTALLINE QUARTZ

CHERT

FLINT

JASPER JASPER

JASPER NOVACULITE

AMORPHOUS QUARTZ

RADIOLARIAN CHERT MEXICAN FIRE OPAL COMMON OPAL

PRECIOUS OPAL