Paleomagnetism and age of three Canadian Rocky Mountain diatremes

1992 ◽  
Vol 29 (1) ◽  
pp. 35-47 ◽  
Author(s):  
P. Jane Wynne ◽  
E. Irving ◽  
Daniel J. Schulze ◽  
Douglas C. Hall ◽  
Hewart H. Helmstaedt
Keyword(s):  
North America ◽  
Rocky Mountains ◽  
Rocky Mountain ◽  
Canadian Rocky Mountains ◽  
Early Devonian ◽  
Polar Wander ◽  
Middle Ordovician ◽  
Normal Polarity ◽  
The Cross ◽  
Age Estimates

Paleomagnetic results, and age estimates derived from them, arc presented for three diatremes, using as a basis of comparison the combined apparent polar wander (APW) path for North America and Europe of Van der Voo. The Cross diatreme of the Front Ranges of the Canadian Rocky Mountains has yielded a radiometric age of 241 Ma (earliest Triassic) and is hosted by the flat-lying Pennsylvanian Tunnel Mountain Formation. It has normal polarity magnetization and yields a paleopole correctly placed according to its radiometric age on the APW path. The Blackpool diatreme (for which no radiometric age is available), which is located in the Main Ranges of the Rocky Mountains, is known to be post-Late Ordovician because it is hosted by rocks of that age. It also has magnetization of normal polarity and yields a paleopole that, when calculated with respect to present horizontal, is coincident with the latest Cretaceous to Paleocene paleopole for North America. The paleopole, when calculated with respect to bedding, lies on the Middle Ordovician portion of the combined APW path. A clockwise rotation of 10° brings the paleopole into agreement with the latest Ordovician. Hence, from a paleomagnetic standpoint, a latest Cretaceous to Paleocene or latest Ordovician age is possible. The HP pipe (radiometric age 391 ± 5 Ma or Early Devonian), previously studied by D. T. A. Symons and M. T. Lewchuk, is hosted in limestones of Upper Cambrian to Middle Ordovician age. It has reversed polarity and yields a paleopole that, when compared with the combined APW path, suggests an age of mid-Permian, although errors are such that it could be somewhat younger, roughly coeval with the Cross diatreme. We conclude, therefore, that the radiometric age estimated for the HP pipe could be too old by about 130 million years.

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.

THE ROCKY MOUNTAIN TRENCH: A PROBLEM

1964 ◽  
Vol 1 (3) ◽  
pp. 184-205 ◽  
Author(s):  
C. H. Crickmay
Keyword(s):  
Rocky Mountains ◽  
Rocky Mountain ◽  
Canadian Rocky Mountains ◽  
The West ◽  
West Side ◽  
Combined Action ◽  
Headward Erosion

The Rocky Mountain Trench is defined as the 1 000-mile valley which marks the west side of the Canadian Rocky Mountains. The background of the Trench as a problem is examined, and descriptions, geographical and geological, are given. Previous work on Trench origin is reviewed and note is taken of the seeming inapplicability of accepted erosion theories to the making of the erosion-made Trench. An hypothesis is offered in which the combined action of drainage hemmed in by bordering uplifts, guided headward erosion, lateral corrasion, and streams repeatedly reversed by continuing diastrophism is suggested as the excavator of the Trench, a valley characterized by the puzzling peculiarity of continuous depth without a consistent gradient.

The amalgamation of Pangea: Paleomagnetic and geological observations revisited

2020 ◽  
Author(s):  
Lei Wu ◽  
J. Brendan Murphy ◽  
Cecilio Quesada ◽  
Zheng-Xiang Li ◽  
John W.F. Waldron ◽  
...  
Keyword(s):  
Selection Criteria ◽  
Late Paleozoic ◽  
Geological Data ◽  
High Quality ◽  
Early Devonian ◽  
Polar Wander ◽  
Middle Ordovician ◽  
Oblique Convergence ◽  
Q Factors ◽  
European Variscides

The supercontinent Pangea formed by the subduction of the Iapetus and Rheic oceans between Gondwana, Laurentia, and Baltica during mid-to-late Paleozoic times. However, there remains much debate regarding how this amalgamation was achieved. Most paleogeographic models based on paleomagnetic data argue that the juxtaposition of Gondwana and Laurussia (Laurentia-Baltica) was achieved via long-lasting highly oblique convergence in the late Paleozoic. In contrast, many geology-based reconstructions suggest that the collision between the two continents was likely initiated via a Gondwanan promontory comprising the Iberian, Armorican, and Bohemian massifs, and parts of the basement units in the Alpine orogen during the Early Devonian. To help resolve this discrepancy, we present an updated compilation of high-quality paleopoles of mid-to-late Paleozoic ages (spanning Middle Ordovician and Carboniferous times) from Gondwana, Laurentia, and Baltica. These paleopoles were evaluated with the Van der Voo selection criteria, corrected for inclination error where necessary, and were used to revise their apparent polar wander (APW) paths. The revised APW paths were constructed using an innovative approach in which age errors, A95 ovals, and Q-factors of individual paleopoles are taken into account. By combining the resulting APW paths with existing geological data and field relationships in the European Variscides, we provide mid-to-late Paleozoic paleogeographic reconstructions which indicate that the formation of Pangea was likely initiated at 400 Ma via the collision between Laurussia and a ribbon-like Gondwanan promontory that was itself formed by a scissor-like opening of the Paleotethys Ocean, and that the amalgamation culminated in the mostly orthogonal convergence between Gondwana and Laurussia.

Conductive structures under the Canadian Rocky Mountains

1985 ◽  
Vol 22 (3) ◽  
pp. 384-398 ◽  
Author(s):  
D. K. Bingham ◽  
D. I. Gough ◽  
M. R. Ingham
Keyword(s):  
Rocky Mountains ◽  
Transfer Functions ◽  
Three Dimensional ◽  
Vertical Component ◽  
Rocky Mountain ◽  
Auroral Zone ◽  
Event Analysis ◽  
Canadian Rocky Mountains ◽  
Period Range ◽  
Single Station

The paper reports results from an array of 33 three-component magnetometers that recorded time-varying fields in 1981 over an area of some 56 000 km2 in the Canadian Cordillera. The array was centred at Tête Jaune Cache in the Rocky Mountain Trench, where a large magnetovariation anomaly had been located in an earlier array study. It was bisected by the trench and extended to the northeast across the Rocky Mountains to the Alberta Foothills and to the southwest across the Cariboo and Monashee mountains. Magnetograms and Fourier transform maps covering the period range 10–91 min show strong attenuation of the vertical component, Z, southwest of the Rocky Mountain Trench, with very large Z amplitudes in the Main Ranges of the Rockies. The horizontal components show an elongated anomaly along the Rocky Mountains Main Ranges and Trench, with three-dimensional features superimposed. The conductive structures include a highly conductive layer, probably in the lower crust, southwest of the trench and a conductive ridge rising into the upper crust near the edge of that layer. Current models have been fitted to observed vertical -and horizontal-component anomalies and show that both layer and ridge are necessary for a fit and that the ridge is 50–80 km wide. Single-station transfer functions at periods of 10 and 22 min have been calculated from a number of variation events of various polarizations, to reduce any displacement of the anomalies by auroral-zone source currents. Artificial-event analysis, with these transfer functions, shows that the conductive ridge lies under the Main Ranges of the Rockies and not under the trench. Its great width indicates a structure of major tectonic significance, which will be considered in another paper.

Mid-Cambrian (Marjuman) trilobites from the Pika Formation, southern Canadian Rocky Mountains, Alberta

1994 ◽  
Vol 31 (6) ◽  
pp. 969-985 ◽  
Author(s):  
Adam Melzak ◽  
Stephen R. Westrop
Keyword(s):  
New Species ◽  
North America ◽  
Rocky Mountains ◽  
Canadian Rocky Mountains ◽  
Inner Shelf ◽  
Low Diversity ◽  
A New Species ◽  
Open Shelf

The carbonates and fine siliciclastics of the Mid-Cambrian (Marjuman) Pika Formation in the southern Canadian Rocky Mountains provide an important record of inner-shelf trilobite biofacies. The faunas are characterized by low diversity and, in contrast to the more diverse open-shelf faunas of other parts of North America, agnostid trilobites are absent. A new biostratigraphic framework of two zones and two informal faunas is proposed for use in inner-shelf settings. Twenty-seven collections from three sections yielded at least eight genera and thirteen species; Marjumia bagginsi is a new species.

Distribution and Life History of the Lodgepole Needle Miner (Recurvaria sp.) (Lepidoptera: Gelechiidae) in Canadian Rocky Mountain Parks

1954 ◽  
Vol 86 (1) ◽  
pp. 1-12 ◽  
Author(s):  
R. W. Stark
Keyword(s):  
Life History ◽  
Rocky Mountains ◽  
National Park ◽  
Life Histories ◽  
Rocky Mountain ◽  
Yosemite National Park ◽  
Canadian Rocky Mountains ◽  
History Of

General. The life history of the lodgepole needle miner in Yosemite National Park, California, has been described (24). The Canadian outbreak was discovered in 1942 but intensive investigations were not commenced until 1948. Many differences have been noted between the Canadian and Californian life histories since the discovery of the outbreak.It is the purpose of this paper to bring together all information collected by the author and staff of the Laboratory of Forest Zoology at Calgary, Alberta, concerning the life history of the lodgepole needle miner in the Canadian Rocky mountains.

Anomalous paleomagnetism of the Crowsnest Formation of the Rocky Mountains

1986 ◽  
Vol 23 (5) ◽  
pp. 591-598 ◽  
Author(s):  
E. Irving ◽  
P. J. Wynne ◽  
M. E. Evans ◽  
W. Gough
Keyword(s):  
North America ◽  
Early Cretaceous ◽  
Rocky Mountains ◽  
Remanent Magnetization ◽  
Rocky Mountain ◽  
Thrust Belt ◽  
Present Position ◽  
Paleosecular Variation ◽  
The Third ◽  
Fold And Thrust Belt

The volcanic Crowsnest Formation of Albian age (late Early Cretaceous) from the Rocky Mountain fold and thrust belt of Alberta has a stable remanent magnetization with a mean direction of 349°, 59 °(α95 = 5°) and paleopole at 78°N, 108°E(dm = 7°, dp = 5°). The inclination is lower than, and the declination clockwise of, the expected mid-Cretaceous paleogeomagnetic field for cratonic North America. Taken at face value the result indicates that the Crowsnest Formation and the thrust sheet in which it occurs have been transported from the south relative to cratonic North America by 17 ± 6 °(about 1800 km) and rotated 24 ± 10° clockwise. It is also possible that flattening of inclination is caused by magnetic anistropy, but tests show this to be unlikely. A third possibility is that the magnetization is secondary and of latest Cretaceous age, but there are good reasons for believing this is not so. Lastly, it is possible that the unit could have been formed close to its present position relative to the craton but was deposited so quickly that the paleosecular variation was not adequately sampled, and the result is only a "spot" reading of the paleofield. The last is our preferred interpretation of the flattened inclination, but the clockwise deflection of the declination could reflect rotation. Other paleomagnetic data from the fold and thrust belt are generally consistent with the third interpretation.

scholarly journals An Early Devonian permineralized rhyniopsid from the Battery Point Formation of Gaspé (Canada)

2017 ◽  
Author(s):  
Kelly C. Pfeiler ◽  
Alexandru M.F. Tomescu
Keyword(s):  
North America ◽  
Thin Layer ◽  
Surface Area ◽  
Water Transfer ◽  
Serial Sections ◽  
Cross Sectional ◽  
Early Devonian ◽  
The Cross ◽  
Sectional Surface

AbstractThe Emsian deposits of the Battery Point Formation (GaspéCanada) host the most diverse Early Devonian flora in North America. While most of this diversity has been described from plant compressions, the permineralized component of the flora is incompletely explored. Based on >15 axes studied in serial sections, we describe a new anatomically preserved rhyniopsid from the Battery Point Formation, Eddianna gaspiana gen. & sp. nov.. Eddianna axes are up to 2 mm in diameter and have a well-developed terete xylem strand with potential centrarch maturation (comprising 80% of the cross sectional surface area) that features Sennicaulis-type tracheid wall thickenings. A thin layer interpreted as phloem is preserved around the central xylem and an irregular sclerenchymatous cortex forms longitudinal anastomosing ridges on the outside of the axes. The anatomy of Eddianna axes suggests that they represent lower portions, specialized in efficient water transfer, of a larger plant whose distal regions have yet to be discovered. Eddianna, the first permineralized rhyniopsid described from the Battery Point Formation, is one of only four anatomically preserved plants reported from this unit. These fossils reiterate the potential for additional discoveries of anatomically preserved plants in the Battery Point Formation.

scholarly journals The Quaternary Geologic History of the Canadian Rocky Mountains

2007 ◽  
Vol 46 (1) ◽  
pp. 5-50 ◽  
Author(s):  
Peter Bobrowsky ◽  
Nathaniel W. Rutter
Keyword(s):  
Central Region ◽  
Rocky Mountains ◽  
Ice Sheet ◽  
Rocky Mountain ◽  
Canadian Rocky Mountains ◽  
Geologic History ◽  
Physical Form ◽  
History Of ◽  
Central Rocky Mountains ◽  
Late Wisconsinan

ABSTRACT The Canadian Rocky Mountains figured prominently during the glacial history of western Canada. First as a western limit or boundary to the Laurentide Ice Sheet, second as an eastern margin of the Cordilleran Ice Sheet, and finally as a centre of local Montane ice. Throughout the Quaternary, complex interactions of glacier ice from these three ice sources markedly changed the physical form of the Rocky Mountains, Trench and Foothills areas. Investigations into the Quaternary history of this region have been ongoing since the beginning of the last century. Since about 1950, the number of studies performed in this area have increased significantly. This paper briefly reviews the historical accomplishments of Quaternary work in the region up to the period of about 1950. From this time to the present, individual study efforts are examined in detail according to the three geographic regions: 1) the northern Rocky Mountains (from the Liard Plateau south to the McGregor Plateau), 2) the central Rocky Mountains (from the McGregor Plateau south to the Porcupine Hills) and 3) the southern Rocky Mountains (from the Porcupine Hills south to the international border). In the northern region, geologic data suggest a maximum of two Rocky Mountain glaciations and only one Laurentide glaciation and no ice coalescence. In the central region, three of four Rocky Mountain events, and at least two Laurentide events are known. Only in the central region is there good evidence for ice coalescence, but the timing of this event is not clearly established. In the south, at least three Rocky Mountain episodes and a variable number of Laurentide episodes are recognized. There is no evidence for ice coalescence. A number of facts support the proposal that Cordilleran ice crossed the Continental Divide and joined with local Montane ice at several locations. However, this expansion of western ice occurred before the Late Wisconsinan in all areas but Jasper. In general, the chronological data presented suggest that the Late Wisconsinan glaciation in the Rocky Mountains was a short-lived event which started around or after 20 ka years ago and ended before 12 ka ago.

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