User:Draconrex/Gunnison Country Geology

This is a work in progress and is not a Wikipedia article.

Gunnison Country Geology is indicative of the geology of the State of Colorado. It would appear that the Gunnison Country is a culmination of Earth's geologic history, at least as it pertains to Colorado. Each era and their twelve periods are represented at some point on the map of the Gunnison Country.

Geologic Formations of the Gunnison Country

Hartman's Rocks

• Circular ring of granite 6 miles in diameter
• Aberdeen Quarry on opposite side, granite used in State Capital Building

Palisades

• Mud flow deposits of West Elks Volcano - 30 mil yrs
• Same rock forms the Castles and Dillon Pinnacles

'W' Mountain

• Volcanic activity from San Juan Mountains
• 'W' Mountain and Signal Peak northern extent of volcanic ash from San Juan Mountains

Tomichi Dome

• Igneous activity (melting within the earth) - lacolith formation
• Gunnison could be called the Laccolith Capital of the World
• Laccoliths of the Gunnison Country are Crested Butte Mountain, Gothic Mountain, Mt. Whetstone, Mt. Axtel, Anthracite Range, Round Mountain, Carbon Peak, Beckwith Mountains, Marcillina Mountians and Mt. Gunnison

Red Mountain and Flat Top Mountain

• Fissure eruptions of lava which cooled to form cap rocks
• Mancos Shale eroded forming Ohio Creek and East River Valleys
• Lava flows resisted erosion formed the flat-topped mountians
  • Blue Mesa, Black Mesa, Big Mesa,

Sapinero Mesa, Willow Mesa, Pine Creek Mesa, Carpenter Ridge and Soap Mesa

• Flat topped hills of welded tuffs (hot avalaches of volcanic ash from San Juan Mountains)

Tomichi Creek, Ohio Creek, Gunnison River

• Flood Plains - broad valleys carved by erosion of meandering streams depositing stream gravel across width of valleys

• Appendix A, Common geologic questions
• Appendix B, Road Logs
  • Gunnison to Montrose
  • Gunnison to Monarch Pass
  • Gunnison to Crested Butte

Formations

• Group of sedimentary beds of similar rock types deposited under similar conditions or same enviroments
• They bear Place Names - Type sections
• Morrison formation - Morrison, Colorado
• Morrison formation - humid conditions, broad rivers shifting course, sediment
• Mancos shale - Mesa Verde formation above Mancos, Colorado, also
• Mesa Verde formation is sandstone cap of the mesa
• Red Rocks Park at Denver - Precambrian, igneous metamorphic
• Fountain formation - Alluvial fans of adjacent mountain range of the Ancient Rockies
• Lyons sandstone - cross-bedding, dunes
• Lykins formation - terrestrial conditions, red and iron oxide (not underwater)
• Entrada formation - Sandstone, mostly Arches National Park, Utah
• Epeiric sea - Dakota formation, near shore; Pierre formation, deeper shale
• Law of Uniformatarianism - assumption of constant processes

Geologic Time Scales (chapt. 3)

Four Eras

• Cenozoic, Mammols (recent life)
• Mesosoic, Reptiles (dinosaurs, mid-life)
• Paleozoic, Marine Invertabrates (early life)
• Precambrian, No fossils found, no historic data to assimilate

Twelve Periods

• Cenozoic periods from latin prefixes,
  • Quaternary, consists of Pleistocene, Pliocene and Miocene Epochs
  • Tertiary, consists of Oligocene, Eocene and Paleocene Epochs
    • Developement of life through the Cenozoic Era

• Mesozoic periods
  • Cretaceous - Chalk cliffs of Dover
  • Jurrasic - Jural Mountains of the Alps
  • Triassic - Germany for Three Rocks

• Paleozoic periods named for areas of discovery
  • Permian - Province of Perm, Russia
  • Pennsylvanian }
  • Mississippian } In England these are know as Carboniferous
  • Devonian - Devonshire, England
  • Silurian - Silures Tribe of Wales
  • Ordovician - Ordovices Tribe of Wales
  • Cambrian - Cambria, England

Correlation of Fossils

• Index fossils - lived for a time then became extinct

Radiometric dating

• Cenozoic, 50 mil yr
• Mesozoic, 225 mil yr
• Paleozoic, 600 mil yr
• Origin of earth, 5 bil yr
  • Few geologist refer to millions of years

Cartographic analysis of Drainage basins

• Emerald Lake of Schofield Pass
• Gothic Creek
• Washington Gulch
• Slate River
  • Confluences above Crested Butte

• East River drainage from Elk Mountains
• Pearl Pass at Pearl Mountain
• East Brush and Brush Creeks
  • Confluences at Riverside

• Taylor Pass and Cement Creek
  • Confluences at Crested Butte South

• Taylor Park drainage
• Taylor River and Spring Creek
  • Confluences at Almont

Part Two - Geologic History of Gunnison Country

• Precambrian: numerous and complex geologic events take place to form the basement complex
• Lower Paleozoic: Cambrian, Ordovician, Silurian,Devonian and Mississippian;
  • low lying land periodically covered by epeiric seas
  • sedimentary rocks are shallow marine deposits, mostly carbonates
• Pennsylvanian - Permian: another epeiric sea covered Colorado followed by uplift of Ancestral Rockies, heavy deposition at flanks of the mountain
• Triassic - Jurrasic: a plains area above sea level,climate at first arid with sand dunes, then tropical with dinosaurs
• Cretaceous: final epeiric sea covers Colorado, leaving important sequence of marine and near shore sedimentary rocks
• Laramide Orogeny (mountain building): the uplift of modern Rocky Mountains folding and faulting of the previous deposited sedimentary rock
• Cenezoic:
  • Erosion and re-uplift of mountains
  • Igneous intrusives formed Gunnison Mineral Belt
  • Vulcanism, widespread volcanic activity concentrated around Gunnison
  • Glaciation, ice age, formed much scenic grandeur

• igneous
• metamorphic

• pre-cambrian basement exposed in areas of heavy erosion,
  • Black Canyon of the Gunnison
  • Glenwood Canyon
  • Grand Canyon of the Colorado

• the cores of mountain ranges which eroded to the basement layer
  • Hartman's Rocks - ring dykes
  • Gold Basin
  • Gunnison Gold Belt - south of Gunnison, Sawtooth Mountains,
    • from east to west towns, Iris, Chance, Vulcan, Midway, Spencer and Dubois
    • also known as greenstone belt ;see Canadian Sheild ;
    • oldest rocks on the continent ;
    • mining active in 1890s ;
    • 1970s studies show zinc-copper-lead sulfides ;
    • also found at Northwest Territories, Canada and Crandon, Wisconsin ;
      • see Conoco Minerals Exploration
  • Elk Creek section of Blue Mesa Reservois
  • Taylor Canyon
  • Quartz Creek
  • Sawatch Range

• pre-cambrian rocks age 1.4 bil yr to 1.7 bil yr

Lower Paleozoic

• Sawatch sandstone beach deposit edge of first epeiric sea
• Manitou dolimite of Ordovician, see Harding sandsone (contains fish fossils); and Freemont limestone
• 50 mil yr of Colorado above sea level
• early Devonian, second epeiric sea covers the land
• Chaffee formation first deposition
• Leadville limestone occured when the sea deepened

Ancestral Rockies

• Uncompahgre Highland and Front Range Highland
• Belden formation
• Gothic formation, brown in color typical of marine
• Maroon formation, red in color terrestrial; see Maroon Bells
• Minturn formation

Triassic - Jurrasic

• Morrison formation, famous for fossills
  • 74 species dinosaurs
  • 25 species tiny primative animals
  • 3 species of crocadile
  • 25 species of river clams, snails
  • 23 species plants
    • economic importance of uranium found in Morrison

between Entrada and Morrison formations

• Wanakah formation
• Junction Creek formation

Cretaceous sea

• Laramide Orogeny, uplift of the modern Rockies

• Orogenic mountains - 65 -72 mil yrs

• Epeiric mountains - 10 mil yrs

Colorado Mineral Belt

• contain Dyke, Sill, Laccolith, Stock, Batholith

Three periods of intrusive activity

• 70 mil yrs, Aspen
• 30 mil yrs, Crested Butte, Snowmass, Italian mountains, Mt Princeton
• 12.5 mil yrs, Treasure Mountain Dome, Round Mountain, Tomichi Dome

Glaciation

• Wisconsin Ice Age, 10,000 yrs
• 9000 foot elevation for glaciers

Part Three, Geologic Provinces

• Sawatch Range
• Elk Mountains
• West Elk Mountains
• San Juan Mountains
• Gunnison Uplift and Black Canyon of the Gunnison River
• Fossil Ridge, Tincup and PItkin
• Powderhorn

Bibliography

1. Prather, Thomas. Geology of the Gunnison Country. Gunnison: B&B Printers, 1982, 1st edition.

External links

1. GPO Catalogue. U.S. Geo Survey
2. U.S. Geological Survey, Annual Reports in Volumes