Structural Cross-Section and Tectonic Model of the Southeastern Canadian Cordillera

1973 ◽  
Vol 10 (11) ◽  
pp. 1607-1620 ◽  
Author(s):  
R. B. Campbell
Keyword(s):  
Cross Sections ◽  
Rocky Mountains ◽  
Structural Evolution ◽  
Crystalline Basement ◽  
Canadian Rocky Mountains ◽  
Vertical Movements ◽  
Tectonic Model ◽  
Columbia Mountains ◽  
Thrust Sheets ◽  
Flanking Regions

Recent models for the structural evolution of the southern Canadian Rocky Mountains have emphasized 'thin-skinned' tectonics whereby thrust sheets piled up from west to east above a décollement on a passive crystalline basement. The concept implies that the more westernly Omineca Crystalline Belt, including granitoid gneiss believed to be basement more than 800 m.y. old, is allochthonous and has moved eastward by at least the amount of shortening in the thrust-faulted zone.Mildly deformed and metamorphosed stratified rocks in the northern Columbia Mountains (central Omineca Crystalline Belt) and adjacent Rocky Mountains permit construction of well-controlled structural and restored stratigraphic cross-sections, which show that the Crystalline Belt and Main Ranges were relatively uniformly uplifted by about 35 000 ft (11 km) whereas flanking regions experienced minor uplifts. Combined with other evidence this indicates that 'thick-skinned' tectonics with vertical movements of the entire crust affected the Omineca Crystalline Belt and the Main Ranges; major horizontal movements seem unnecessary. The Omineca Crystalline Belt is regarded as an autochthon in which the basement was extensively deformed and it is suggested that basement is deformed beneath the Main Ranges. The zone of thrusting and décollement above the basement is restricted to the Front Ranges and Foothills and may result from westward underthrusting of the craton.

Structure, strain and AMS of the Uzunakhmat thrust sheet (Talas Range, Kyrgyz North Tian Shan)

2020 ◽  
Author(s):  
Anastasia Kushnareva ◽  
Artem Moskalenko ◽  
Alexander Pasenko
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Structural Evolution ◽  
Middle Part ◽  
Tien Shan ◽  
Initial Shape ◽  
Thrust Sheet ◽  
Structural Style ◽  
Thrust Sheets ◽  
Tian Shan

<p>The Talas Range forms the northwest part of the Caledonides of the Northern Tian Shan. Based on differences in the structural style, metamorphism and sedimentary successions, three thrust sheets have been identified – the Uzunakhmat, Talas, and Kumyshtag thrust sheets. The Talas and Kumyshtag thrust sheets consist of Neoproterozoic-Ordovician terrigenous and carbonate rock units, whereas the Uzunakhmat thrust sheet consists of Neoproterozoic terrigenous rocks metamorphosed up to greenschist facies. The Uzunakhmat thrust sheet is separated from the Talas and Kumyshtag thrust sheets by the southwest-dipping Central Talas thrust (CTT). The dextral strike-slip Talas-Fergana Fault bounds the Uzunakhmat thrust sheet in the southwest. The main deformation events occurred in the Middle-Late Ordovician.</p><p>Structural and strain studies were done along profiles normal to the strike of folds and faults and located in the northwest and southeast parts of the Uzunakhmat thrust sheet. We also incorporate in our study structural profile in the central part of the Uzunakhmat thrust sheet, documented by Khudoley (1993) and Voytenko & Khudoley (2012).</p><p>The main strain indicators were detrital quartz grains in sandstones. Rf/φ and Normalized Fry methods were used to identify the amount of strain. Oblate ellipsoids predominate with Rxz values varying mostly from 1,6 to 2,4. Long axes of strain ellipsoids are sub-horizontal with the southeast to east-southeast trend. Similar trends have long axes of the anisotropy magnetic susceptibility ellipsoid being parallel to fold axes, cleavage-bedding intersection and mineral lineation as well as the trend of the major thrusts, including CTT.</p><p>The modern shape of the Uzunakhmat thrust sheet is similar to an elongated triangle, pinching out northwest and expanding southeast. Cross-section balancing corrected for the amount of strain shows along-strike decreasing of shortening in the southeast direction. Total shortening varies from 35% to 55% between sections located about 15 km from each other. Such significant variation in shortening corresponds to variation in structural style with much more tight folds and more numerous thrusts for cross-sections with a higher amount of shortening. However, the restored length of all cross-sections is quite similar pointing to the approximately rectangular initial shape of the Uzunakhmat thrust sheet. Our interpretation is that during the Caledonian tectonic events, the Uzunakhmat thrust sheet was displaced in the northwest direction with accompanied thrusting and folding of rock units within the thrust sheet. These deformations formed the modern shape of the thrust sheet in accordance with the amount of shortening detected by cross-section balancing. This interpretation also implies that modern erosion did not significantly affect shape of the Uzunakhmat thrust sheet formed after the Caledonian deformation.</p><p>Khudoley, A.K., 1993. Structural and strain analyses of the middle part of the Talassian Alatau ridge (Middle Asia, Kirgiystan). J. Struct. Geol. 6, 693–706.</p><p>Voytenko N.V., Khudoley A.K. Structural evolution of metamorphic rocks in the Talas Alatau, Tien Shan, Central Asia: Implication for early stages of the Talas-Ferghana Fault. // C. R. Geoscience. 2012. V. 344. P. 138–148.</p>

scholarly journals Glaciation in Columbia Mountains and Rocky Mountains in Canada

Geografie ◽  
1998 ◽  
Vol 103 (4) ◽  
pp. 414-427
Author(s):  
Pavel Červinka
Keyword(s):  
Rocky Mountains ◽  
Field Research ◽  
Climatic Changes ◽  
Canadian Rocky Mountains ◽  
Slope Movements ◽  
Columbia Mountains

The article deals with the glaciation of selected regions in Canadian Rocky Mountains and Columbia Mountains and examines in detail glacial morphological forms. It is based on author's field research and interpretation with regard to the glacial forms classification and origins. Glacial fluctuations in the area studied were influenced by climatic changes; most glacial morphological forms are supposed to be relatively recent. Frequent slope movements cause ongoing creation of talus and other accummulations.

Construction of the Lesser Himalayan–Subhimalayan thrust belt: The primary driver of thickening, exhumation, and high elevations in the Himalayan orogen since the middle Miocene

Geology ◽  
2021 ◽  
Author(s):  
Sean P. Long ◽  
Delores M. Robinson
Keyword(s):  
Cross Sections ◽  
Middle Miocene ◽  
Structural Evolution ◽  
Crustal Thickening ◽  
Thrust Belt ◽  
Himalayan Orogen ◽  
Orogenic Wedge ◽  
Primary Driver ◽  
Thrust Sheets ◽  
High Elevations

Documenting the structural evolution of the Himalayan orogen is fundamental for understanding the dynamics of collisional orogenesis. We argue that the importance of deformation in the frontal, Lesser Himalayan–Subhimalayan (LH-SH) portion of the Himalayan thrust belt for driving crustal thickening over the past ~15–13 m.y. has long been overlooked. To quantify its contribution to thickening, we measured parameters from 22 published cross sections that span the length of the orogen. The mean structural uplift accomplished by the LH-SH thrust belt increases from 10–15 km in the eastern half of the orogen to 15–23 km in the western half. An antiformal culmination constructed by LH duplexing is observed across the orogen and increases in structural height (to as much as 15–20 km) and north-south width moving westward. Construction of the culmination was the primary mechanism for building and maintaining wedge taper. The westward scaling of culmination size is accompanied by doubling and tripling of LH-SH shortening and accretion magnitude, respectively; when combined with a consistent orogen-wide modern taper angle (11° ± 2°), this indicates that duplexing facilitated the growth of an overall larger orogenic wedge moving westward. Following the initial southward propagation of deformation into LH rocks at ca. 15–13 Ma, the Himalayan orogenic wedge has been characterized by stacking of multiple thin, smalldisplacement thrust sheets to develop a high-taper orogenic wedge. Thus, LH-SH deformation has had a profound effect on driving thickening, exhumation, and the attainment of high elevations since the middle Miocene.

General discussion

1988 ◽  
Vol 326 (1589) ◽  
pp. 321-325 ◽  
Keyword(s):  
Cross Sections ◽  
Rocky Mountains ◽  
Rock Properties ◽  
Soft Sediment ◽  
Structural Geometry ◽  
Rock Property ◽  
Fault Bend ◽  
Thrust Sheets ◽  
Sediment Deformation ◽  
Geometric Techniques

J. G. R amsay, F.R.S. (ETH-Zentrum, Zurich, Switzerland). Several of the cross sections and profiles through various parts of the Himalayas that have been presented at the Meeting were based on geometric techniques appropriate to the frontal thrust belt of the Rocky Mountains of Canada and the U.S.A., or to the soft sediment deformation in and around Taiwan. In these reconstructions, faults, especially thrusts, are considered to exert the dominant Control on the forms of structures. Fold forms appear only as fault bend folds developed as a consequence of movement of thrust sheets over irregular step-like thrust plane topography. In these models the effect of rock competence only seems to be considered as a characteristic rock property controlling the ramp-flat geometry of the fault planes, and the rock properties seem to exert little or no influence on the fold style. I would suggest that this current fashion of making constructions to depth is not only mechanically unsound, but it does not accord with the observations of structural geometry.

Conodont geothermometry and tectonic overburden in the northernmost East Greenland Caledonides

2001 ◽  
Vol 138 (6) ◽  
pp. 687-698 ◽  
Author(s):  
JAN AUDUN RASMUSSEN ◽  
M. PAUL SMITH
Keyword(s):  
Cross Sections ◽  
Hanging Wall ◽  
Crystalline Basement ◽  
Continuous Increase ◽  
East Greenland ◽  
Predominant Component ◽  
Overburden Thickness ◽  
Half Graben ◽  
Thrust Sheets ◽  
Lower Palaeozoic

Kronprins Christian Land lies at the northernmost limit of the East Greenland Caledonides, and may be divided into four main tracts: foreland, parautochthon, thin-skinned thrust sheets containing Neoproterozoic sediments, and thick-skinned thrust sheets of crystalline basement. The eastern part of the foreland and the parautochthon are composed of Ordovician–Silurian shelf carbonates overlain by Llandovery–lower Wenlock turbidites deposited at the southern margin of the Franklinian Basin. Deformation of the parautochthon occurred beneath a major detachment, the Vandredalen thrust, with Neoproterozoic sediments of the Rivieradal Group lying in the hanging wall. The Rivieradal Group was deposited in an E-facing half-graben and was displaced westwards across its rift shoulders during Caledonian thrusting. Extensive sampling for conodonts has been carried out within the Lower Palaeozoic rocks of the foreland and parautochthon in order to increase the precision of structural interpretations and to provide data on maximum burial temperature and, in turn, the thickness of overburden. In contrast to earlier studies, conodont colour alteration indices (CAI) show a gradual and continuous increase from CAI 3 in the eastern part of the foreland to CAI 5+ in the easternmost parts of the parautochthon. The isopleths are not disrupted or truncated by thrusting, as previously suspected, indicating that the heating is not attributable to pre-thrusting stratigraphic overburden. Furthermore, considerations of the regional geology indicate that there was no significant accumulation of sedimentary overburden in post-Caledonian time; the predominant component is thus considered to be loading by thrust sheets. Modelling of the overburden thickness suggests that, prior to erosion, it increased from 3.9 km (CAI 3) in the easternmost foreland to a maximum of 12.5 km beneath the Vandredalen thrust sheet in the easternmost part of the area, providing constraints for restoring cross-sections across the orogen.

Wildfires in the southern Canadian Rocky Mountains and their relationship to mid-tropospheric anomalies

1993 ◽  
Vol 23 (6) ◽  
pp. 1213-1222 ◽  
Author(s):  
E.A. Johnson ◽  
D.R. Wowchuk
Keyword(s):  
North America ◽  
Rocky Mountains ◽  
Large Scale ◽  
Fire Frequency ◽  
Fuel Moisture ◽  
Large Fire ◽  
Canadian Rocky Mountains ◽  
Area Burned ◽  
Upper Level ◽  
Moisture Conditions

In this paper we present evidence for a large-scale (synoptic-scale) meteorological mechanism controlling the fire frequency in the southern Canadian Rocky Mountains. This large-scale control may explain the similarity in average fire frequencies and timing of change in average fire frequencies for the southern Canadian Rocky Mountains. Over the last 86 years the size distribution of fires (annual area burned) in the southern Canadian Rockies was distinctly bimodal, with a separation between small- and large-fire years at approximately 10–25 ha annual area burned. During the last 35 years, large-fire years had significantly lower fuel moisture conditions and many mid-tropospheric surface-blocking events (high-pressure upper level ridges) during July and August (the period of greatest fire activity). Small-fire years in this period exhibited significantly higher fuel moisture conditions and fewer persistent mid-tropospheric surface-blocking events during July and August. Mid-tropospheric surface-blocking events during large-fire years were teleconnected (spatially and temporally correlated in 50 kPa heights) to upper level troughs in the North Pacific and eastern North America. This relationship takes the form of the positive mode of the Pacific North America pattern.

Canadian Rocky Mountains

1903 ◽  
Vol 21 (6) ◽  
pp. 685
Author(s):  
J. Norman Collie
Keyword(s):  
Rocky Mountains ◽  
Canadian Rocky Mountains

Spatial and temporal variations of fire regimes in the Canadian Rocky Mountains and Foothills of southern Alberta

2016 ◽  
Vol 25 (11) ◽  
pp. 1117 ◽  
Author(s):  
Marie-Pierre Rogeau ◽  
Mike D. Flannigan ◽  
Brad C. Hawkes ◽  
Marc-André Parisien ◽  
Rick Arthur
Keyword(s):  
Rocky Mountains ◽  
Fire History ◽  
Fire Severity ◽  
Ecological Integrity ◽  
Fire Regimes ◽  
Temporal Variations ◽  
Fire Season ◽  
Canadian Rocky Mountains ◽  
Southern Alberta ◽  
Fire Exclusion

Like many fire-adapted ecosystems, decades of fire exclusion policy in the Rocky Mountains and Foothills natural regions of southern Alberta, Canada are raising concern over the loss of ecological integrity. Departure from historical conditions is evaluated using median fire return intervals (MdFRI) based on fire history data from the Subalpine (SUB), Montane (MT) and Upper Foothills (UF) natural subregions. Fire severity, seasonality and cause are also documented. Pre-1948 MdFRI ranged between 65 and 85 years in SUB, between 26 and 35 years in MT and was 39 years in UF. The fire exclusion era resulted in a critical departure of 197–223% in MT (MdFRI = 84–104 years). The departure in UF was 170% (MdFRI = 104 years), while regions of continuous fuels in SUB were departed by 129% (MdFRI = 149 years). The most rugged region of SUB is within its historical range of variation with a departure of 42% (MdFRI = 121 years). More mixed-severity burning took place in MT and UF. SUB and MT are in a lightning shadow pointing to a predominance of anthropogenic burning. A summer fire season prevails in SUB, but occurs from spring to fall elsewhere. These findings will assist in developing fire and forest management policies and adaptive strategies in the future.

Structural evolution in the Moine of northwest Scotland: a Caledonian linked thrust system?

1986 ◽  
Vol 123 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Robert W. H. Butler
Keyword(s):  
Cross Sections ◽  
Lower Crust ◽  
Structural Evolution ◽  
Amphibolite Facies ◽  
Metamorphic Basement ◽  
Thrust System ◽  
Lower Crustal

AbstractA model is proposed whereby the Caledonian metamorphic basement-cover complex of northwest Scotland (the Moine) is considered as a linked thrust system. This system lies between the Moine thrust at its base and the Naver–Sgurr Beag slide at its top. Ductile fold and thrust zones, which developed at mid crustal levels at metamorphic grades from greenschist to amphibolite facies, are interpreted as decoupling from a detachment presently situated at relatively shallow depths. This model is illustrated by two preliminary balanced cross-sections. These imply shortening across the northwest Scottish Caledonides in excess of 130 km and probably over 200 km. When these structures are restored onto a crustal template a considerable quantity of lower crust is found to be required at depth. The most likely location for the lower crustal wedge is beneath the Grampian Highlands.

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