Deep structure beneath the Southern Rocky Mountains from the Rocky Mountain Front Broadband Seismic Experiment

1998 ◽  
Vol 33 (2) ◽  
pp. 199-216 ◽  
Author(s):  
A. L. Lerner-Lam ◽  
A. Sheehan ◽  
S. Grand ◽  
E. Humphreys ◽  
K. Dueker ◽  
...  
Keyword(s):  
Rocky Mountains ◽  
Deep Structure ◽  
Rocky Mountain ◽  
Southern Rocky Mountains ◽  
Seismic Experiment ◽  
Mountain Front

Tectonic controls on basement exhumation in the southern Rocky Mountains (United States): The power of combined zircon (U-Th)/He and K-feldspar 40Ar/39Ar thermochronology

Geology ◽  
2021 ◽  
Author(s):  
Jason W. Ricketts ◽  
Jacoup Roiz ◽  
Karl E. Karlstrom ◽  
Matthew T. Heizler ◽  
William R. Guenthner ◽  
...  
Keyword(s):  
Rocky Mountains ◽  
Rocky Mountain ◽  
Snowball Earth ◽  
Southern Rocky Mountains ◽  
Basement Rocks ◽  
Rocky Mountain Region ◽  
Multi Stage ◽  
Inverse Models ◽  
Multiple Pulses ◽  
Differential Uplift

The Great Unconformity of the Rocky Mountain region (western North America), where Precambrian crystalline basement is nonconformably overlain by Phanerozoic strata, represents the removal of as much as 1.5 b.y. of rock record during 10-km-scale basement exhumation. We evaluate the timing of exhumation of basement rocks at five locations by combining geologic data with multiple thermochronometers. 40Ar/39Ar K-feldspar multi-diffusion domain (MDD) modeling indicates regional multi-stage basement cooling from 275 to 150 °C occurred at 1250–1100 Ma and/or 1000–700 Ma. Zircon (U-Th)/He (ZHe) dates from the Rocky Mountains range from 20 to 864 Ma, and independent forward modeling of ZHe data is also most consistent with multi-stage cooling. ZHe inverse models at five locations, combined with K-feldspar MDD and sample-specific geochronologic and/or thermochronologic constraints, document multiple pulses of basement cooling from 250 °C to surface temperatures with a major regional basement exhumation event 1300–900 Ma, limited cooling in some samples during the 770–570 Ma breakup of Rodinia and/or the 717–635 Ma snowball Earth, and ca. 300 Ma Ancestral Rocky Mountains cooling. These data argue for a tectonic control on basement exhumation leading up to formation of the Precambrian-Cambrian Great Unconformity and document the formation of composite erosional surfaces developed by faulting and differential uplift.

Carbon dynamics of pristine and hydrologically modified fens in the southern Rocky Mountains

2003 ◽  
Vol 81 (5) ◽  
pp. 477-491 ◽  
Author(s):  
Rodney A Chimner ◽  
David J Cooper
Keyword(s):  
Water Table ◽  
Rocky Mountains ◽  
National Park ◽  
Net Primary Production ◽  
Rocky Mountain ◽  
Rocky Mountain National Park ◽  
Plant Production ◽  
Water Diversion ◽  
Southern Rocky Mountains ◽  
Diversion Structure

We measured water table levels, above- and below-ground plant production, and CO2 and CH4 emissions for five fens in Rocky Mountain National Park, Colorado, to determine whether a water diversion project was adversely affecting carbon cycling. Two fens were located beneath the water diversion, and three fens were located in an adjacent pristine watershed. The diversion lowered water table levels in one fen, while the other fen was not hydrologically modified. Total NPP (net primary production) for all sites ranged from 130 to 316 g C·m–2·year–1, with a mean of 217 g C·m–2·year–1, and belowground NPP accounted for ~60% of the total. Maximum CO2 emissions for pristine fens ranged between 170 and 273 mg CO2-C·m–2·h–1, with annual emissions of 230–388 g CO2-C·m–2·year–1. However, the hydrologically modified fen had maximum CO2 emissions of 457 mg CO2-C·m–2·h–1 and had an annual flux of 573 g CO2-C·m–2·year–1. Maximum CH4 emissions ranged from 3 to 25 mg CH4-C·m–2·h–1, with annual emissions of 9–61 g CH4-C·m–2·year–1. The water diversion structure lowered water tables, increased CO2, decreased CH4 and NPP, and resulted in the site likely becoming a net source of carbon.Key words: peatlands, fens, CO2, CH4, hydrology, Rocky Mountains, Rocky Mountain National Park, plant production.

Oxygen isotope records of goethite from ferricrete deposits indicate regionally varying holocene climate change in the Rocky Mountain region, U.S.A.

2004 ◽  
Vol 61 (1) ◽  
pp. 64-71 ◽  
Author(s):  
Derek J. Sjostrom ◽  
Michael T. Hren ◽  
C. Page Chamberlain
Keyword(s):  
Oxygen Isotope ◽  
Rocky Mountains ◽  
Regional Scale ◽  
Rocky Mountain ◽  
Summer Precipitation ◽  
Relative Increase ◽  
Holocene Climate ◽  
Climate History ◽  
Southern Rocky Mountains ◽  
Rocky Mountain Region

Oxygen isotopes of goethite from ferricrete deposits were measured from both northern and southern Rocky Mountain localities to assess geographic variability in regional Holocene paleoclimate change. A ∼3.7‰ increase in oxygen isotope values of 14C-dated goethites in the northern Rocky Mountains suggests a regional-scale relative increase in amounts of isotopically heavy summer precipitation since the early Holocene. In contrast, oxygen isotope values from the southern Rocky Mountains increase abruptly ∼2.1‰ at ∼6200 14C yr B.P. then decrease ∼2.4‰ between ∼2000 14C yr B.P. and the present. We interpret this period of relatively high δ18O values as evidence for a middle Holocene warm period combined with a relatively strong summer monsoon. These variable climate records suggest that the Rocky Mountains of the western United States have had a spatially heterogeneous Holocene climate history.

scholarly journals Beryllium-10 dating of the Foothills Erratics Train in Alberta, Canada, indicates detachment of the Laurentide Ice Sheet from the Rocky Mountains at ~15 ka

2019 ◽  
Vol 92 (2) ◽  
pp. 469-482 ◽  
Author(s):  
Martin Margold ◽  
John C. Gosse ◽  
Alan J. Hidy ◽  
Robin J. Woywitka ◽  
Joseph M. Young ◽  
...  
Keyword(s):  
Rocky Mountains ◽  
Ice Sheet ◽  
Younger Dryas ◽  
Rocky Mountain ◽  
Laurentide Ice Sheet ◽  
Exposure Dating ◽  
Mountain Front ◽  
Ice Retreat ◽  
Cordilleran Ice Sheet ◽  
Latitudinal Trend

AbstractThe Foothills Erratics Train consists of large quartzite blocks of Rocky Mountains origin deposited on the eastern slopes of the Rocky Mountain Foothills in Alberta between ~53.5°N and 49°N. The blocks were deposited in their present locations when the western margin of the Laurentide Ice Sheet (LIS) detached from the local ice masses of the Rocky Mountains, which initiated the opening of the southern end of the ice-free corridor between the Cordilleran Ice Sheet and the LIS. We use 10Be exposure dating to constrain the beginning of this decoupling. Based on a group of 12 samples well-clustered in time, we date the detachment of the western LIS margin from the Rocky Mountain front to ~14.9 ± 0.9 ka. This is ~1000 years later than previously assumed, but a lack of a latitudinal trend in the ages over a distance of ~500 km is consistent with the rapid opening of a long wedge of unglaciated terrain portrayed in existing ice-retreat reconstructions. A later separation of the western LIS margin from the mountain front implies higher ice margin–retreat rates in order to meet the Younger Dryas ice margin position near the boundary of the Canadian Shield ~2000 years later.

A structural interpretation across part of the northern Rocky Mountains, British Columbia, Canada

1979 ◽  
Vol 16 (6) ◽  
pp. 1228-1241 ◽  
Author(s):  
Robert I. Thompson
Keyword(s):  
British Columbia ◽  
Rocky Mountains ◽  
Lateral Displacement ◽  
Rocky Mountain ◽  
Thrust Faults ◽  
Northern Rocky Mountains ◽  
Eastern Margin ◽  
The North ◽  
Structural Style ◽  
Mountain Front

The northern Canadian Rocky Mountains, as exemplified by the Halfway River map-area (94B) in British Columbia, consists of a rugged and mountainous structurally complex Foothills subprovince of large amplitude box and chevron-style folds in rocks of late Paleozoic and Mesozoic age, and a structurally diverse Rocky Mountain subprovince with open folds and apparently inconspicuous thrust faults in upper Precambrian to upper Paleozoic rocks; separating them is a narrow topographically subdued and heavily vegetated 'transition interval' comprising more penetratively folded and faulted shales and thin-bedded carbonate rocks of late Devonian and Mississippian age.Flat thrust faults, with displacements in the order of 10 km, which occur under the eastern margin of the Rocky Mountain subprovince (mountain front) extend across the 'transition interval' and beneath the western margin of the Foothills subprovince. These faults terminate within a décollement along the Devonian and Mississippian Besa River shale, as the displacement on them is transformed into disharmonic kink-type box and chevron folds in overlying units and into tectonic thickening within the Besa River shale. Because most of the major thrust faults along the Rocky Mountains are 'blind' and cannot be traced to surface exposures, one is left with the erroneous impression that very little lateral displacement (foreshortening) has occurred in the northern Canadian Rocky Mountains.The basic change from a well organized thrust-fault terrane in the southern Rockies to a more diverse fold terrane with few large mappable thrusts in the north is consistent with changes in the stratigraphic character of the rock prism that was deformed: the proportion of thick incompetent shale units increases northward, and major lateral carbonate to shale facies transitions traverse the eastern margin of the Rocky Mountain subprovince.Despite the differences in structural style from south to north, strain patterns within the northern Rocky Mountains are consistent with the lateral eastward movement of a detached prism of sedimentary rocks, and support the basic tenets of thin-skinned tectonics.

Raising the West: Mid-Cenozoic Colorado-plano related to subvolcanic batholith assembly in the Southern Rocky Mountains (USA)?

Geology ◽  
2021 ◽  
Author(s):  
Peter W. Lipman
Keyword(s):  
United States ◽  
Rocky Mountains ◽  
Rocky Mountain ◽  
The United States ◽  
Crustal Thickness ◽  
Crustal Thickening ◽  
High Plains ◽  
High Potassium ◽  
Southern Rocky Mountains ◽  
Moho Depths

The Southern Rocky Mountains of Colorado, United States, have the highest regional elevation in North America, but present-day crustal thickness (~42–47 km) is no greater than for the adjacent, topographically lower High Plains and Colorado Plateau. The chemistry of continental-arc rocks of the mid-Cenozoic Southern Rocky Mountain volcanic field, calibrated to compositions and Moho depths at young arcs, suggests that paleocrustal thickness may have been 20%–35% greater than at present and elevations accordingly higher. Thick mid-Cenozoic Rocky Mountain crust and high paleo-elevations, comparable to those inferred for the Nevadaplano farther west in the United States from analogous volcanic chemistry, could be consistent with otherwise-perplexing evidence for widespread rapid erosion during volcanism. Variable mid-Cenozoic crustal thickening and uplift could have resulted from composite batholith growth during volcanism, superimposed on prior crustal thickening during early Cenozoic (Laramide) compression. Alternatively, the arc–crustal thickness calibration may be inappropriate for high-potassium continental arcs, in which case other published interpretations using similar methods may also be unreliable.

Studies of the Salix lucida and Salix reticulata complexes in North America

1986 ◽  
Vol 64 (3) ◽  
pp. 541-551 ◽  
Author(s):  
George W. Argus
Keyword(s):  
North America ◽  
Morphological Variation ◽  
Rocky Mountains ◽  
Rocky Mountain ◽  
Western North America ◽  
Northeastern North America ◽  
Southern Rocky Mountains ◽  
The North ◽  
Rocky Mountain Region ◽  
Hybridization And Introgression

A study of morphological variation in the Salix lucida complex revealed three geographical races: one in northeastern North America, a second in western North America extending from Alaska to California, and a third in the southern Rocky Mountains, S. lucida ssp. lucida, Salix lucida ssp. lasiandra comb, nov., and Salix lucida ssp. caudata comb, nov., respectively. The Salix reticulata complex in the Rocky Mountain region is represented by two geographical races, ssp. reticulata in the north and ssp. nivalis in the south. Variation in ssp. nivalis suggests that hybridization and introgression occur where the two races overlap, and that the results of past hybridization are still evident in the southern Rocky Mountains.

Mitbringsel aus den Ferien

Praxis ◽  
2005 ◽  
Vol 94 (47) ◽  
pp. 1869-1870
Author(s):  
Balestra ◽  
Nüesch
Keyword(s):  
Rocky Mountains ◽  
Spotted Fever ◽  
Rocky Mountain ◽  
Rickettsia Conorii ◽  
Rocky Mountain Spotted Fever ◽  
Klinische Diagnose ◽  
Rickettsia Rickettsii

Eine 37-jährige Patientin stellt sich nach der Rückkehr von einer Rundreise durch Nordamerika mit einem Status febrilis seit zehn Tagen und einem makulösem extremitätenbetontem Exanthem seit einem Tag vor. Bei suggestiver Klinik und Besuch der Rocky Mountains wird ein Rocky Mountain spotted fever diagnostiziert. Die Serologie für Rickettsia conorii, die mit Rickettsia rickettsii kreuzreagiert, war positiv und bestätigte die klinische Diagnose. Allerdings konnte der beweisende vierfache Titeranstieg, möglicherweise wegen spät abgenommener ersten Serologie, nicht nachgewiesen werden. Nach zweiwöchiger antibiotischer Therapie mit Doxycycline waren Status febrilis und Exanthem regredient.

Pruning to manage white pine blister rust in the southern Rocky Mountains

2011 ◽  
Author(s):  
Amanda Crump ◽  
William R. Jacobi ◽  
Kelly S. Burns ◽  
Brian E. Howell
Keyword(s):  
Rocky Mountains ◽  
White Pine Blister Rust ◽  
White Pine ◽  
Southern Rocky Mountains ◽  
Blister Rust

LITHOSPHERIC RESISTIVITY STRUCTURE BENEATH THE ROCKY MOUNTAIN FRONT: 2D ANISOTROPIC INVERSION OF MAGNETOTELLURIC DATA

2016 ◽  
Author(s):  
Daniel Feucht ◽  
◽  
Paul A. Bedrosian ◽  
Anne Sheehan
Keyword(s):  
Rocky Mountain ◽  
Resistivity Structure ◽  
Magnetotelluric Data ◽  
Mountain Front
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