Tustin CA Badlands vs. So. Dakota Badlands...Verde National Park 8,000-8,570’ 6,000-6,200’...
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Tustin CA Badlands vs. So. Dakota Badlands
Transcript of Tustin CA Badlands vs. So. Dakota Badlands...Verde National Park 8,000-8,570’ 6,000-6,200’...
Tustin CA Badlands vs. So. Dakota Badlands
Geology of National Parks: Mesa Verde and Ancient Settlements
1) Geologic setting 2) Landslides 3) Bandelier National Monument
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View of Cliff Palace; largest cliff dwelling in the US; about 150 rooms for ~120 people; from inhab from 1100-1300
Mesa Verde National Park Cuesta
8,000-8,570’
6,000-6,200’
6,700-6,900’
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Note “cuesta” gentle slope and cliff faces (N and E)’ drainage from top to south; in Four Corner area of CO - From DVD book - The first Spanish explorers to the area called it Mesa Verde, or “green table.” This expression is actually a mis-nomer. The correct geological term for the area is a cuesta, not a mesa. Mesas are isolated, flat-topped highlands with steeply sloping sides or cliffs, and are topped by a cap of much harder rocks that are resistant to erosion. The cap protects the softer underlying slopes or cliffs from being quickly weathered away. The only difference between a cuesta and a mesa is that a cuesta gently dips in one direction. Mesa Verde is inclined slightly to the south at about a 2-3% slope. This cuesta is made up of many separate, smaller “mesas” situated between the canyons. Although technically we should call the park “Cuesta Verde,” convention dictates that we use the term “mesa” when describing the area.
Only one road for access
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MV drains south to Mancos River, then to San Juan River flowing west into CO River; The steep northern escarpment with its high erosion rate has cut headward back (south) into the rim of the northern escarpment such that upper parts of Morefield and Prater Canyons have been cut away and removed by erosion. These valleys are called “beheaded valleys” as the upper part of their drainage has been removed and their valley floors simply end abruptly at the escarpment.
Western Interior Seaway ~130-70 MYA
Colorado Plateau
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Seds. laid down in MVNP from 94 – 80 MYA within time when Western Interior Seaway covered the area; whole CO Plateau area uplifted several times beginning with the Laramide Orogeny 66 MYA and continues
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2:13 Geol. X-sect (next better from USGS) Mancos Shale late Cret ~85-75 MYA fines deposited in Western Interior Seaway Mesa Verde Group > Point Lookout SS near-shore marine SS Menefee Fmn. deposited as inland area as seaway slowly dried in coastal swamps and floodplains with some coal Lower and Upper Cliff House SS marine coastal sands
~80 MYA
From: USGS
~82 MYA
~94 MYA
~25 MYA Minette Dikes
Mancos Shale,2,000-2,240’ thick Marine offshore origin
Pt. Lookout SS 330 – 375’ thick Marine nearshore origin
Menefee Fmn. 350-400’ thick River floodplain and coastal swamp
Cliff House SS 400’ thick Marine nearshore origin
~3,500’ (not to scale)
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From: https://gec.cr.usgs.gov/archive/mverde/fig4.png Note two dikes not shown in DVD x-sect Figure 4: . Stratigraphic column of formations present in Mesa Verde National Park (after Wanek, 1959, and Griffitts, 1990).
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From: https://gec.cr.usgs.gov/archive/mverde/ - Figure 2. Cliff Canyon, a typical canyon in Mesa Verde National Park, showing the broad mesa top and deep canyon entrenched by an ephemeral stream. The Cliff House Sandstone forms the two prominent cliffs below the mesa surface, while the steep slope below the lower cliff is formed in the underlying Menefee Formation.
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Fro: USGS - Figure 3. Photograph from Point Lookout looking west showing the steep northern escarpment, which drops off into Montezuma Valley.
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Figure 7. Photograph of the entrance road into Mesa Verde National Park. The road traverses a steep slope of Mancos Shale, along the eastern side of Point Lookout, which is prone to slope failure.
Gila Cliff Dwellings Nat. Monument, So. Rocky Mountains Volcanic Field – Eruptions 40-25 MYA
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17:02 Gila Cliff Dwellings Nat. Mon. occupies So. Rocky Mountains Volcanic Field
Minette - An intrusive, generally dike-building
igneous rock
Loess – deposit of fine silt,
wind-blown 3-30’ thick when
laid down
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Figure 9. The minette dike in Navajo Canyon from which an 40Ar/39Ar age of 25.65±0.08 million years was obtained.
Cliff House Sandstone (SS)
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Google images; called “alcoves”, not caves which are below ground
Cliff dweller “post-holes”
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Cliff dweller “post-holes”
Black desert varnish
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2:05 Black desert varnish
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5:55 GW that has infiltrated exits as seeps along face
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6:46 “Alcove” formed by GW then collapses forming alcove with running water
Bandelier National Monument
Fe/Mn oxides (red and black)
Smoke residue (creosote??)
SS demo
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Series from Location near Sante Fe NM; Pueblo Indian cliff dwellings at Bandelier National Monument, near Los Alamos, New Mexico; we were there in late 2005; note chemical glaze on outside from water depos of Fe/Mn oxides and fixed to surface by bacteria, whereas inside is from fires (creosote??)
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smart dwellers built in upper CHSS > dryer, below thick loess soil layer to absorb water; and shale floor with trench possible for running water
Long House cliff dwelling (~150 rooms) built in a large alcove formed in the upper sandstone unit of the Cliff House Sandstone.
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From: USGS - Figure 5. Long House cliff dwelling built in a large alcove formed in the upper sandstone unit of the Cliff House Sandstone.
Menefee Shale
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Ditto above for USGS landslide report; landslides are orange areas; The map depicts more than 200 landslides ranging in size from small (0.01 square miles) earthflows and rock slumps to large (greater than 0.50 square miles) translational slides and complex landslides - Many of the landslides depicted on this map are probably stable as they date to the Pleistocene (approximately 1.8–0.011 Ma) and hence formed under a different climate regime.
Cuesta slope erosion as cap-rock of sandstone slows erosion of shale below
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3:33 “Cuesta” > steep face with gently sloping land approaching it
Fajada Butte - Slope landslides – Cliff House SS cap-rock over erosive Menefee Shale (side slopes)
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13:30 Fajada Butte (island of stone amidst remnants of long eroded material) with Menefee Fmn. slopes topped by Cliff House SS (steep cliffs); in Chaco Culture National Historic Park - ref. landslides of this variety with SS topping erosive shale (look out below!)
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USGS - This rubbly SS debris buries the shale, protecting it from erosion, often leaving a pile of SS over shale rubble, like above which is 300’ high pile Figure 8. Isolated hills of Mancos Shale capped by Point Lookout Sandstone rubble along the entrance road. The sandstone rubble was originally deposited by large rockfalls, rock avalanches, or debris flows on a Mancos Shale surface. The sandstone rubble then acts as a protective cap, while surrounding areas of Mancos Shale without caps were lowered by erosion.
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Landslide in from left?? (note slope of dotted line and higher elevation on top of left slope)
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NOTE next 4 slides focus on landslides; Landslides are a regular occurrence in the area. The shale of the Mancos and Menefee Formations are very unstable because they weather so easily. This makes regular construction and maintenance of the roads necessary. From - https://pubs.usgs.gov/sim/3090/ > Preliminary map of Landslide Deposits in the Mesa Verde National Park area, Colorado, 2016 Author or Editor By Paul E. Carrara
Bandelier National Monument, south of Los Alamos, NM
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Bandelier National Monument, NM south of Los Alamos; close to Georgia O’Keefe Ranch where you can see her works in the surrounding mountains
Frejoles Cr. tributary to Rio Grande River
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Frejoles Cr. Trib to Rio Grande below Bandeller dwellings – likely went up to avoid floods
