Upcoming Division Events
“Foldastic” and “Faultastic” Deformation Features at the Base of the Lewis Thrust Sheet in the Kananaskis Area
Speaker: Normand Bégin | Nanook Geo-Exploration Inc.
Location: Schlumberger Canada, Province Conference Rooms 2nd floor - Palliser One Building, 200, 125 9th Avenue SE
November 7, 2019, 11:30am
*CSPG members can register for free and track their CPD hours!
The Lewis Thrust Fault extends over 450 km in mapped view length, from the Rockies in Montana to the Southern Canadian Cordillera, where it dies into folded carbonate beds of the Mississippian-age Rundle Group at Mount Kidd in the Kananaskis Area. South of Mount Kidd and along the Highway 40, the thrust juxtaposed steeply SW-dipping (50-70 degrees) carbonaceous units of the Rundle Group in the hangingwall, against also steeply SW-dipping clastic units of Mesozoic-age in the footwall. Although complex folding is somewhat visible in the hangingwall, when driving by the highway and looking up to the various summits of the Lewis Range, hiking and scrambling up peaks and ridges reveal far more spectacular views of the deformation features in the basal part of the Lewis Thrust Sheet. In the summer of 2019, several named and unnamed summits from King Ridge and northward to Opal Ridge South were climbed, capturing a series of photos that outline a range of complex deformation features in the Lewis Thrust Sheet, otherwise not present further south along the Lewis Range in the vicinity of Highwood Pass.
Heading from the Highway 40 and northeastward to about three quarters of the way up those summits, in the structurally highest levels of the Lewis Sheet, a train of broad open folding (100’s meters in wavelength) with essentially no faulting is observed. Higher up towards the summits and structurally lower where the deformed panel gets at its steepest for this portion of the Lewis Range examined, duplexes and ramp anticlines are common. Thrust faults have m’s to 10’s m of displacement with a NE sense of displacement. Multiple detachment horizons are present in the thinly laminated carbonaceous units, with faulted offsets on thickly and massive carbonate layers. The basalmost part of the Lewis Thrust hangingwall section, on the backside (NE) of the summits, display folded units with the interlimb angle typical of a tight to almost isoclinal geometry. C-S fabrics (top to the NE) in cataclasites are observed in thinly laminated interbeds.
Collectively, those structures described above could represent a broad strain gradient from higher up to lower down in the basal part of the Lewis Thrust Sheet in the Kananaskis Area. The folds, detachment and other shear-related structures would have been passively tilted to the SW, as a result of motion on the easterly and underlying major imbricates like the Rundle and Misty thrust sheets. Further south in the Lewis Range such as Little Highwood Pass, the hangingwall section structurally above the Jurassic units consists mainly of a SW-dipping homocline in Mississippian units, with a much thinner sheared package above the thrust.
Normand graduated with a BSc in Geological Engineering at Laval University in 1985, then completed a Ph.D. in Geology at Queen’s University in 1989. He worked as a Postdoctoral Fellow at the University of Calgary (1990-1992), then in mining exploration in the NWT for 2 years as a structural geologist and field mapper. He worked with the Foothills Research Project (U of C) from 1994 to 1996, before joining Talisman Energy as an exploration geologist and structural specialist in various deformed belts around the world. Along with his teammates, he has successfully geosteered over 50 wells with several commercial hydrocarbon discoveries in thrust-fold belts of the Canadian Rockies Foothills, Llanos Foothills of Columbia, Zagros Belt of Kurdistan. For the last four years with Repsol Canada, he worked on projects in Papua New Guinea, Russia, Algeria and Bolivia. Since the late 1990’s, he has led several structural geology trips for the industry Alberta, Kurdistan and Australia.