Class Note for NATS 101 at UA
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Date Created: 02/06/15
NATS 101 A Geological Perspective GEOLOGIC HIGHLIGHTS OF SOUTHEASTERN ARIZONA AND VICINITY YEARS AGO GEOLOGIC TIME SCALE GEOLOGIC AND LIFE HISTORY OHONOZD39JO imam QUATERNARY PERIOD 0 100 years Holocene 10000 years Holocene 10000 16 my Pleistocene TERTIARY PERIOD 16 53 my Pliocene 53 15 my Miocene 15 237 my Miocene 237 366 my Oligocene Industrialized society develops mineral and water resources Today39s Sonoran Desert appears Many mammals go extinct Glacialinterglacial climate uctuations with associated changes in lakes rivers ora and fauna Large mammals like mammoths mastodons and giant ground sloths roamed across southern Arizona Hunters and gatherers arrive in southern Arizona about 11000 years ago eg Murray Springs Mammoth Kill Site Episodes of basaltic volcanism occur in the Pinacates San Francisco Peaks White Mountains and San Bernardino Valley The presentday Basin and Range landscape of the Sonoran Desert began to take shape 15 my ago Deep pervasive fracturing of the crust and earthquake activity broke up a high mountainous southern Arizona into blocks Some of these crustal blocks drop down to form the basins while others tilt but remain high to be the mountains Present stream systems evolve The initially closed basins ll up with sediments washed off the surrounding mountains and slowly integrate into regional drainage systems eg Gila Salt and Colorado Rivers The climate becomes semiarid The Gulf of California and the San Andreas fault develop as southwestern North America begins to get torn apart by plate tectonic processes With the opening of the Gulf the Colorado River drains south and excavates the Grand Canyon Subduction of ocean crust along the western margin of North America continues until the East Paci c Rise interacts with the continental crust resulting in the activation of the San Andreas plus Basin and Range faults Rivers carry sediments off the high mountains in southern Arizona and deposit gravels to the north on what is now the edge of the Colorado Plateau The horse evolves in North America and other modern mammals diversify Between about 2030 my tremendously explosive volcanic eruptions ripped across the southwest and northern Mexico The landscape was built up higher by layers of volcanic rocks eg tuffs ash and rhyolite These volcanic rocks now make up the Chiricahua Tucson Galiuro Superstition Ajo and Atascosa Mountains in southern Arizona and the Sierra Madre Occidental in Mexico During this volcanism plutons were emplaced into the upper crust eg Kitt Peak and Stronghold Dragoon Mountains granites i SEE REVERSE SIDE i NATS 101 A Geological Perspective 366 578 my Eocene 578 664 my Paleocene YEARS AGO GEOLOGIC TIME SCALE Volcanic mountains exist in southern Arizona A tremendous geologic upheaval occurs in western North America called the Laramide Orogeny Intrusions of molten rock into the crust and associated volcanism form new continental crust enlarging the North American continent Plutonic rocks now exposed in Texas Canyon Catalina Rincons Graham Tucson Sierra Nevada and many other mountains were intruded and metamorphosed large portions of the upper crust As the Pacific Ocean crust was rapidly subducted under colliding North America the continen GEOLOGIC AND LIFE HISTORY oHoNowmg gt76 CRETACEOUS PERIOD 664 80 my 80 144 my JURASSIC PERIOD 144 208 my TRIASSIC PERIOD 208 245 my PERMIAN PERIOD 245 286 my tal crust was deformed and folded buckling like an accordion Beneath some volcanoes most copper and molybdenum now being mined in Arizona were forming by hydrothermal interactions Dinosaurs go extinct around 66 my ago Mountains called the Mogollon Highlands begin to build up in southern Arizona as great quantities of granitic magma intrude the crust of western North America Some molten rock erupted onto the Earth39s surface eg 20000 feet of volcanic rock in the Santa Rita Mountains These high volcanic peaks formed a mountain chain stretching from Alaska to Mexico The Bisbee copper deposit formed beneath one of these volcanoes Other parts of Arizona were covered by an extensive swampy mud at across which meandered rivers jammed with logs now the Petrified Forest Volcanic ash blown in from the south and west must have occasionally fallen on these swamps Later a great sand desert extended across northern Arizona and into Utah and Colorado Fossilized sand dunes from this desert are now exposed in the cliffs of Zion and Arches National Parks A shallow sea covered southeastern and northeastern Arizona about 100 my ago Abundant plant growth along the swampy margins of that seaway accumulated to form coal now being mined in Black Mesa Flowering plants and birds evolve in Jurassic time Dinosaurs and insects become abundant in Triassic and Jurassic time North America was part of a supercontinent called Pangaea Reptiles become abundant i SEE REVERSE SIDE i NATS 101 A Geological Perspective OHONOWFgtFU imam PENNSYLVANIAN PERIOD 286 320 my MISSISSIPPI PERIOD 320 360 my DEVONIAN PERIOD 360 408 my SILURIAN PERIOD 408 438 my ORDOVICIAN PERIOD 438 505 my CAMBRIAN PERIOD 505 570 my PRECAMBRIAN PROTEROZOIC 570 2500 my ARCHEAN 2500 4500 my Tropical shallow sea and coastal environments existed in Arizona for a few 100 million years There were at least three cycles of shallow sea inundation transgressions followed by uplift and emergence of land regression Coral reefs fishes and marine invertebrates were abundant in the warm shallow waters that cover the continental crust Thick deposits of limestone mudstone shale and sandstone formed in these marine and tidalbeach environments Paleozoic marine sedimentary rocks are exposed now throughout Arizona notably in the Grand Canyon and Whetstone Mountains The first abundant fossils of marine life with hard parts appear in Cambrian rocks Arizona crust formed around 2 billion years ago during an orogenic event as the continental crust continued to grow in size by accretion The first four billion years of geologic history is obscured by more recent events and changes First life probably evolved 35 to 3 billion years ago but remained much the same algae for billions of years Cycles of mountain buildingerosion deposition reshaped the land as continents must have drifted across the earth i SEE REVERSE SIDE i
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