Download Laramide Orogeny - Major Tectonic event that formed the Rocky

Laramide Orogeny ‐ Major Tectonic event that formed the Rocky Mountains. ‐Occurred 70‐40 million y BP ‐Occurred in the interior of the North American Plate. ‐Occurred 1,000 miles from the nearest subduction zone! ‐Laramide uplifts are topographically high areas. ‐Cause: DEBATED ‐ Centainly related to ongoing convergence/subduction of the ‘Oceanic Farallan Plate’ and possibly other oceanic plates off the coast. I ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐1,000 miles‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐I Ancient Plate Boundary Nevadan Orogeny (170 Million) ‐Farallon Plate = Steeper Subduction Sevier Orogeny (100 Million) Laramide Orogeny (70‐40 Million) ‐Farallon Plate = Shallower Subduction (No one knows why!) ‐Black Hills, SD eastern extent ‐Mountain building in Colorado, etc. Black Hills Granite, igneous intrusion that poped up through a sedimentary cap during the Laramide Orogeny (70‐40 Million) Eastern most extent of Rocky Mountain building. REGIONS of the ROCKYS Canadian Rockies : 100 km. wide (narrow), steep, mostly “sedimentary rocks”, that has been thrust up. ‐Mountain Front (Continuous) Middle/Central Rockies : wider, more dispersed Mountain ranges separated by large areas of High Plains (Big Horn Basin, Wyoming Basin) Southern Rockies : (Colorado / New Mexico) “Front Range” – marks eastern edge ‐53 peaks over 14,000 ft. in Colorado! 75‐40 Million y BP (Laramide Orogeny) Crystalline Rock “UPLIFTED” 34‐10 Million y BP (Cascadian Orogeny) “Rocky Mountain Erosion Surface” forms Crystalline Rock buried by its own eroded sediments. Extended the HIGH PLAINS to present day Utah, Wyoming, and Idaho. 10 Million “UPLIFT EVENT” Eroded sediments are removed – transported toward the Great Plains Evidence for Buried Mountains = Eroded Sediments in the High/Great Plains Laramie, WY – local left over buried sediments ‐Gang Plank Further to the east = Sediments (geographically higher) Basins – Formed by the erosion of the High Plains (was once a continuous surface). High Plains – stratified sands (granite/quartz), carried by streams (Platte, Missouri, Arkansas) Spanish P
Peaks, South
hern Colorad
do Formed via Volcanism West & Eaast Spanish Peak ‐Cryystalline; Igneous Rock ‐Pro
oduced Radiall Dikes Before75 Million y BP Stratified Sandstone (d
dep. ‐ shallow
w sea) 75‐25 Million y BP Dikes form Batholith and Radial D
n y BP ‐ NOW 25 Million
Erosion – sediments on
n Great Plainss RADIAL D
DIKES Jemez LLineamentt ayton Volcaniic Field Raton‐Cla
‐ Clo
osest active vo
olcanic to MI ‐You
ungest in field
d (9‐10 Million
n y BP) Migration
n of the North
h American Pllate over a Hot Spot. SSPANISH PEA
AKS ALPINE GLACIERSS Source: High County (M
Mountains; “C
Cirques”) + No
ormally 300 ftt. thick, due tto continued movement ‐doesn’t need thicknesss like contineental glaciers
Gllaciation Age Range* A
Oxyggen‐isotope
stage
e Mid‐continent M
c
correlation prre‐Bull Lake 500,000‐700,0
000 14 an
nd 16 P
Pre‐Illinoisan
prre‐Bull Lake 0,000 300,000 to 500
8 and
d 12 p
pre‐Illinoisan Bu
ull Lake 0,000 130,000 to 300
6 (an
nd 8) Illlinoisan Pinedale 0 12,000‐23,000
2 n L
Late Wisconsi
Orograph
hic Effect Powell Terrace – down cutting during an interglacial (less sediment) Cody Terrace – lower terrace, formed after the Powell Terrace. Shoshone River – coarse sediment, builds terraces. Powerhouse Section, Baniff NP, Canada Thicker ice produces a more linear stone fabric! Glaciated Not Glaciated Glaciated Not Glaciated Colorado Plateau ‐Parts of Wyoming, Utah, Colorado, Arizonia, and New Mexico. ‐Mongollon Rim (Escarpment) ‐ Southern Colorado Plateau ‐ Uplifted, Horizontal Rocks Colorado Plateau – thick crust, which all was lifted up. ‐ Uplifted in the last 10 Million Years Mongollon Rim (below) 25‐ 10 Million y BP Hypothesized Mantle Plume or Up Welling raised the boundary between the Sierra Nevada and the Basin and Range. 10 Million y BP, the Colorado Plateau was also uplifted. Because of the thick crust the whole region was uplifted, instead of succumbing to faulting. 10 Million y BP Shiprock, New Mexico ‐ Volcanic Neck with Radial Dikes ‐ Radial Dikes – olivine rich magma (deep within mantle). ‐ A lot of erosion has taken place! San Francisco Volcanic Field ‐Active 6 Million y BP in Arizona ‐600 “Basalt Cinder Cones” ‐ Low Viscosity (rapid/fluid) ‐Sunset Crater ‐ Cinder Cone = 1 event, Quick!, small (< 1,000 ft.), Spray lava bombs/flows. Structural Controls (Differential Erosion; Different Erosion Rates) Red Rocks = Permian Period Rocks (298 – 252 million y BP) ‐ elevated levels of oxygen in the atmosphere (heavily oxidized) ‐ Long record of sedimentary rocks (horizontal structure) ‐ Upper Mesozoic Period = shallow interior sea (easy to trace) Monument Upwarp ‐LARGE, BROAD, Gentle Anticline, SE Utah ‐ Uplifting, followed by Jointing, followed by Erosion, followed by Differential Erosion. ‐Cap Rocks (Resistant SANDSTONE) protecting (erodible SHALE). HEAVY RAIN EVEENTS (RARE), FLUSH MATEERIAL OUT OFF THE VALLEY
Y Grand C
Canyon (Still a “YOU
UNG STREA
AM” in Davisian Thero
oy) 330‐530 M
Million y BP ‐Mississip
ppi Delta 550 Millio
on y BP ‐Coastal SSetting (Dune Field) “LARGE G
GAP” 2 Billion yy BP ‐Crystallin
ne Rocks Canyon De Chelly, NE Arizona & Mesa Verde, SW Colorado Overlying Sandstones let infiltrating water penetrate to the underlying Shale. Dissolved Salts created NICHE – People lived in there. The dating of RAT MITTENS (14C ‐ Radiocarbon) allowed researchers to see when/why people left! ‐Juniper Trees there 1,000 y BP ‐Indians cut all the trees down. ‐Climate warms!!! ‐Juniper not able to grow back. Arroyos ‐Stream systems characterized by steep canyon walls and flat “sandy” basin floors. +Major periods of cutting – 2,000‐700 y BP (WARMING)! +Recently between 1865‐1915 (LANDUSE CHANGES – GRAZING)! FACTORS Climate Change (el nino, la nina) Internal Adjustments (base level changes, uplifting?) Land Change (Grazing) Cutting & Filling events. Invasion of Tamarisk (SALT CEDAR) Highly invasive!!!! ‐Loves wet/sandy sites (produces a lot of seeds) 1942 2000 ‐Less discharge on the system ‐Deeper channel, less width ‐Sediment deposits near vegetation Basin & Range Extensional Faulting (Normal Faults) Playa – Old Lake Bed, Pleistocene in age (Glacial Times; Pluvial Lake) ‐Wetter Climates (Southerly Jet Stream) DUNES! ‐Found in Grabens, accumulations of salts (evaporated) Pediment‐ plained bedrock surface, exposed at ground level. ‐Backwasting Alluvial Fan‐ Fluvial fan shaped depositional features. ‐Distrubutary channels across the landscape surface ‐Located on the Pediment surface ‐Most extensive in arid/semi arid regioins ‐ Often along mountain fronts ‐Erosion/Depositon ‐Streams primary transport system ‐Grow outward/Conical shape Bajada – entrenchment/coalesce of Alluvial Fans. ‐Larger Drainage Basin = Larger Fan ‐Smaller Drainage Basin = Smaller Fan Bajada Dating A
Alluvial Fa
ans OSL Datin
ng ‐Streams (turbidity) maay not ZERO o
out the sand grain. AT CAUTION!! ‐USE GREA
‐LIGHT SEDIMENTS = YYoung DIMENTS = O
Old, manganesse/iron) ‐DARK SED
‐Dessert Pavemen
nt, clays blow
w in. The use of Desert Pavement for dating = 144C – Radiocarb
bon. Decomp
posed bacteriaa in the rinds. Evidencce for Rapiid/Recent Uplift alon
ng Fault Bllocks +WINE GLLASS CANYON
N Downcuttting – Stream
m/Canyon Uplift – M
Mountains aro
ound the canyyon W
Wine Glass Ca
anyon D LAKE SEDIM
MENTS +FAULTED
+FAULTED
D ALLUVIAL FFANS FFaulted Lake Sediments Fau
ulted Alluviall Fans/Toes Desert Pavement (EOLIAN) ‐Coarse, Angular, COMPACT! ‐OLD THEORY: Sand blew away. ‐NEW MODEL: Sand blows in, rain event deposits sands below rocks, evaporation of water in the sand causes the sand to expand/contract, which moves the rocks upward. Sand River Plane / Columbia Plateau Type of Volcanoes; Shield Volcanoes – Broad, Gentle Slope, Large Cinder Cones – Small, One Event, Fast Composite Volcanoes – Explosive, Large Eruption, Smaller than Shield Volcanoes SHIELD VOLCANO CINDER CONE COMPOSITE VOLCANO SNAKE RIVER PLAIN – associated with the Yellowstone Hot Spot. ‐Over 16 Million years old (Hot Spot Migrated; toward the SW, North American Plate Movement) ‐Many Shield Volcanoes (various sizes, liquid lava; low viscosity) Pearlette Ash (Lava Creek) – From the Yellowstone Caldera (600,000 y BP) Columbia Plateau (SE Washington / NE Oregon) ‐Created from the subduction of the Juan de Fuca Plate. ‐17‐13,000 y BP ‐MANY DIKES, highly fluid magmas flowing out of cracks over the landscape. Columbia River “Basalt” Group (CRBG) +Imnaha Basalt (17.5‐17 Million y BP) 5.5% +Grande Ronde Basalt (17‐15 Million y BP) 87 % +Wanapum Basalt (15.5‐14.5 Million y BP) 6% +Saddle Mountain Basalt (14‐6 Million y BP) 1.5% Not all lavva flows depo
osit basalt oveer one anotheer. Different flow patternss are noticed in different rregions. OWING on thee original surface. Consequeent Flow – FLO
Subsequent Flow – NO
OT FLOWING o
on the originaal surface. Cordilleeran Ice Sh
heet ‐Orograph
hic Effect‐ mo
oist Pacific airr snows in thee high elevaations, soon p
producing glaciers on the windward
d slopes. Most Receent; FRASER G
GLACIATION (15,000 y BP) ‐VASSHON STADEE – furthest exxtent of the
Corrdilleran Ice SSheet. ‐NASSSIOU STADEE – furthest exxtent of the
Lau
urentide Ice SSheet. Scablan
nds J. Harlan B
Bretz (1920’s) ‐Proposed
d Scabland features were p
produced from a Catastrop
phic Flood! ‐Higghly Criticized ‐App
plied Uniform
mitarianism (P
Processes in the PASST happen NO
OW) ‐VERY LAR
RGE RIPPLES o
on the landsccape, found in
n the 1970’s/80
0’s. ‐40 JJokulhlaups ((Catastrophicc Floods) foun
nd! OTHER CA
ATASTROPHIC
C FLOODS; ‐Lake Bon
nneville at Red
d Rock Pass, IIdaho ‐Lake Agassiz ‐Lake Saginaw ‐Mars! Cascadees ‐Step Ang
gle Subductio
on of the Juan
n de Fuca Platte ‐30 Millio
on y BP – early
ly cascade episode ‐7 Million
n y BP MAJOR
R OUTPOURIN
NGS; ‐Major vo
olcanic outpou
urings ‐Formatio
on of small vo
olcanoes ‐Magma/Mud blaanketed the rregion een at the coast in the figu
ure) ‐Sedimentary Prism (Se
me the modern
n ‐Waas also uplifteed and becam
Olyympic Range ‐Cascadess are deformeed remnants of an earlier
volcanic ssediment. ‐Still somee sporadic vo
olcanoes (13,5
500 ‐ 14,000 feet high) ‐Surround
ding Volcanoe
es typically (5
5,000 – 6,000 feet high) ‐Mount Stt. Helens exp
plodes the mo
ost ‐Hiigh Viscosity &
& Pressure Reconstructing Past Eruptions ‐Looking at Lahars (fast mudflows = glacier melting due to volcanic eruptions). ‐ Old tree bases ‐14C – Radiocarbon trees and counting tree rings ‐Allows researchers to estimate eruptions and tree age. LAHAR Lake Russell and Puget Lobe ‐The Puget Lobe collected meltwater in depressions (Lakes Russell, Sammamish, Snaqualmie, and Skykomish) ‐Uplift influenced the region (Known from elevated marine sediments)