Canadian Rockies | GeologyVirtualTrips

CANADIAN ROCKIES - BANFF & JASPER N.P.

FIELD TRIP STOPS – THRUST FAULTING CREATES MOUNTAIN RANGES THAT ARE LATER SCULPTED BY GLACIAL ACTION.

LOCATION: Banff and Jasper Canadian National Parks in Alberta, Canada.

GEOLOGIC FEATURES: Thrust Faults; Phanerozoic Sedimentary Strata; Cirques; Aretes; U- and Hanging Glacial Valleys; Terminal and Lateral Moraines; Anticlines and Synclines; Glacial Striations; Glacial Flour

DESCRIPTION:

The Canadian Rockies consist of Northwest to Southeast trending ranges – the Main Ranges, which form the Continental Divide, and the Front Ranges that appear directly to the east .

Rocks of the Canadian Rockies are composed mainly of shallow marine sedimentary rocks, predominantly shale, sandstone, dolomite, and limestone. Rock formations are dominantly Precambrian to Jurassic (600 -145 mya) in age, though, in places, there are rocks as young as Lower Cretaceous. The main period of mountain-building was between 80-60 mya during the Laramide Orogeny..

The result of deformation was several parallel thrust faults accompanied by folding of sedimentary strata, many of which dip to the west between 40-60 degrees. Thrust faults are often associated with periods of mountain building and caused sediments to move laterally and upwards. This tectonic process often resulted in older strata being emplaced over younger rocks. Cambrian rocks, for example, were often thrust over Mississippian to Cretaceous rocks. Thrusting commonly took place on shales which are weaker sedimentary rocks.

Glacial erosion during the last ice age. has resulted in cirques, aretes, U-shaped and Hanging Valleys, and moraines giving the Canadian Rockies their jagged topography and glacial lakes.

STUDENT QUESTIONS:

(1) Why are beds of shale commonly associated with the fault plane of a thrust fault?

(2) Folding is commonly associated with tectonic compression. What is an Anticline and how does it compare to a Syncline?

(3) Why are thrust faults and their corresponding mountainous terrain associated with Convergent Plate Boundaries?

(4) Glaciers always move away from the mountainous highlands. If this is so, then why is it commonly said that glaciers are currently receding?

(5) Glacial lakes often have waters that are bright blue or green. Explain why this is so.

(6) Explain the origin of Cirques and how they are associated with U-shaped Valleys.

(7) Explain the origin of terminal moraines. Why have the positions of terminal moraines receded towards the mountains over the past several decades? Explain the origin of Lateral Moraines.

(8) Describe the physical process by which glacial striations are formed.

(9) CHALLENGE: Draw a cross-section illustrating how thrust faults have moved thousands of feet of older rock over younger strata.

(10) CHALLENGE: What is a Palinspastic Map and how is it related to the thrust faults of the Canadian Rockies?(

SELECTED REFERENCES:

-Banff National Park. New World Encyclopedia. Accessed on : https://www.newworldencyclopedia.org/entry/Banff_National_Park

-Hargreaves, A. 2015. The Magnificent Southern Canadian Rockies. GEOExpro, v. 12, No. 2. Accessed on 4/15/20: http://www.geoexpro.com/articles/2015/04/the-magnificent-southern-canadian-rockies

-Kumar, A. 2013. Geology and scenery of The Banff National Park, Canada in Earth Science India, Popular Issue, VI (10/1/13), pp. 1-19. Accessed 4/15/20: http://www.earthscienceindia.info/popular%20archival/pdf-54.pdf

PHOTOS: (Photos are sequenced approximately from southeast to northwest as one travels through Banff N.P. and Jasper N.P.)

BANFF NATIONAL PARK

Figure 1 - Cascade Mountain rises abruptly near downtown Banff. Rocks seen represent, from top (younger) to bottom (older), the Paleozoic Rundle and Banff Formations (Mississippian) and Devonian Pallister Fm. (Devonian). (Photo 2016)

Figure 2 - On the Garden Path Trail at Sunshine Meadows, Banff N.P. Note the mountains in the distance with beds dipping away from each other suggesting a breached Anticline. (Photo 2016)

Figure 3 - Further down the trail we cross the Continental Divide, a characteristic of the Main Ranges. Water to the left of the divide flows to the Pacific while water to the right flows to the Atlantic or Gulf of Mexico. (Photo 2016)

Figure 4 - Near the end of the trail is Rock Isle Lake lying within the Main Range of the Canadian Rockies in Banff N.P. (Photo 2016)

Figure 5 - Lower Falls at Johnston Canyon, Banff N.P. Johnston Creek cuts through relatively soft limestone on its way to Bow River. (Photo 2016)

Figure 6 - Castle Mountain (formerly Mt. Eisenhower) is the easternmost member of the Main Ranges in Bow Valley. The Castle Mt. Thrust Fault passes through the mountain just below the tree line. Rock Formations present from the top down are the Cambrian Eldon Fm. (Dolomite/LS), Stephen Fm. (Shale), and Cathedral Fm. (Dolomite/LS) which forms the lowest formed cliff. Below the Cathedral and covered by a forested slope are the Lower Cambrian Grog Fm. and PreCambrian Miette Fm. below which is the Thrust Fault that lies above Upper Paleozoic and Mesozoic sediments. (Photo 1973)

Figure 7 - In Banff N.P. on the way from Castle Mt. to Morant's Curve. (Photo 2016)

Figure 8 - From Morant's Curve, Banff N.P. Prominent U-shaped Valley and Cirques appear in the background behind the Bow River. (Photo 2016)

Figure 9 - .Moraine Lake, Banff N.P. Mountains are part of the Wenkchemna Range (Valley of the 10 Peaks). The Lake is not the result of a moraine, but instead is the result of damming due to rock collapse from the Tower of Babel. The landscape is carved by glacial action into a series of U-shaped Valleys and Cirques. (Photo 2016)

Figure 10 - Moraine Lake, Banff N.P. Note the Talus Cone at the base of the cliff.

Figure 11 - Lake Louise, Banff, N.P. lies below Victoria Glacier. Water is Emerald Green due to the nature of sunlight absorbed and reflected by Rock Flour (Glacial Silt), a common phenomenon of glacial lakes. Rock Formations seen are (fron top down) Middle Cambrian Eldon Fm. (Dolomite/LS), Stephen Fm. (Shale), Cathedral Fm. (Dolomite/LS) and Lower Cambrian Grog Fm. Lake Louise was formed by damming of meltwater by a Terminal Moraine.

Figure 12 - Bow Lake and Glacier, Banff N.P. U-shaped Valley to the left and Bow Glacier to its right in the process of carving the mountain. This photo, taken in 1973, shows the glacier before it receded due to worldwide global warming.

Figure 13 - Peyto Lake, Banff N.P. This lake is particularly known for its intense turquoise color. Glacial lakes are often Bluish or Greenish in color due to the presence of Rock Flour - silt produced by the grinding of ice against rock. The glacial flour absorbs the shortest wavelengths of sunlight while the water absorbs the longer wavelengths. The remaining middle wavelengths (blue and green) are left to be reflected to be seen by the eye. (Photo 2016)

Figure 14 - Inclined sedimentary strata adjacent to Peyto Lake.. Banff N.P. (Photo 2016)

JASPER NATIONAL PARK

Figure 15 - The Athabasca Glacier emerges from the Columbia Icefield in Jasper N.P. Photo taken from the Icefield Discovery Center. (Photo 2016)

Figure 16 - Terminal and Lateral Moraines of the Athabasca Glacier. Jasper N.P. (Photo 1973)

Figure 17 - This photo of the Athabasca Glacier was taken 43 years after the Figure directly above. Current indications are that that this glacier has receded about 1500 ft. over that time. Jasper N.P. (Photo 2016)

Figure 18 - Athabasca Glacier extends out from the Columbia Icefield. The latest Terminal Moraine is seen at the proximal end of the glacier. Jasper N.P. (Photo 2016)

Figure 19 - Glacial Striations etched into the bedrock by rock particles embedded in the base of the advancing glacier. These particular grooves were not exposed in 1973 since ice covered this specific area at that time. Only the recession of the glacier due to global warming has exposed these striations.The view is towards the current glacial edge. Jasper N.P. (Photo 2016)

Figure 20 - Glacial Striations in the bedrock. View is in the direction away from the glacier's terminal edge. Jasper N.P.(Photo 2016)

Figure 21 - Stutfield Glacier. Jasper N.P. (Photo 1973)

Figure 22 - PreCambrian quartzites form a limb of a syncline on Endless Chain Ridge. Jasper N.P. (Photo 1973)

Figure 23 - Athabasca Falls is noteworthy for the huge volume of water that cuts through a hard Precambrian/Cambrian quartzite cap rock, carving the underlying limestones. Jasper N.P. (Photo 1973)

Figure 24 - Sawtooth mountains of the Colin Range. Erosion of near vertical beds of Devonian and Mississippian limestone give rise to a sawtooth pattern when exposed along a ridge.Jasper N.P. (Photo 1973)

PRE-DEVONIAN

DEVONIAN

CARBONIFEROUS

Figure 25 - The Three Peaks of Chetamon Mountain (Jasper N.P.). Thrust faulting has produced an interesting geological display - the peak to the far left is composed of Pre-Devonian strata; the Middle Peak is comprised of the Devonian Pallister Fm and older Devonian Rocks; the peak to the right is composed of Carboniferous. So, we see two thrust faults that move three slabs of rock so that the older rocks are on top of younger. Arrows represent the relative motion of slabs above and below each thrust fault. Jasper N.P.(Photo 1973)

Figure 26 - Folding and faulting. Jasper N.P. (Photo 1973)

Figure 27 - Large synclinal fold spans the top of the mountain.Jasper N.P. (Photo 1973)

Figure 28 - Intense rock deformation. Braided glacial streams with coarse sediment occupy the foreground. Jasper N.P. (Photo 1973)

Figure 29 - Mt. Robson is the highest point in the Canadian Rockies at 12,972 ft. Local relief above the valley floor is over 10,000 ft. Strata are are composed of Cambrian Limestone/Dolomite and Quartzite. Though these layers are horizontal, they actually represent the bottom of a broad syncline. Jasper N.P. (Photo 1973)