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.

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.

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.

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.

NOTES ON PLANT DISTRIBUTION IN THE ROCKY MOUNTAINS OF ALBERTA

1962 ◽  
Vol 40 (8) ◽  
pp. 1091-1094 ◽  
Author(s):  
R. T. Ogilvie
Keyword(s):  
Rocky Mountains ◽  
Storm Track ◽  
Rocky Mountain ◽  
Distribution Patterns ◽  
Plant Distribution ◽  
Mountain Region ◽  
Climatic Effects ◽  
Southern Area ◽  
Rocky Mountain Region ◽  
Number Of Plant Species

Three kinds of variability in the Rocky Mountain flora of Alberta are considered. The flora is composed of species with two gross distribution patterns: the boreal element and the cordilleran element. There are minor floristic differences from valley to valley; such differences involve the sporadic occurrence of certain species in different valleys. Main consideration is given to another type of floristic variability which involves a major floristic difference between the southern part of the mountain region and the northern part.The Crowsnest–Waterton area in the southern part of Alberta is distinctive climatically and phytosociologically from the rest of the Rocky Mountain region of Alberta. Moreover, a large number of plant species and some animal taxa occur in Alberta only in this area. Two possible features are suggested as being responsible for the distinctiveness of the southern area: the climatic effects of the occurrence of the area within a major storm track; and the existence of an adjacent unglaciated area which, during Pleistocene, could have served as a refugium for taxa which subsequently expanded in the southern area.

‘A Turrible Looking and Furious Anamal’: Comparative Psychology in the Rocky Mountains from Lewis and Clark to Washoe

1987 ◽  
Vol 60 (1) ◽  
pp. 59-62 ◽  
Author(s):  
Philip Howard Gray
Keyword(s):  
Animal Behavior ◽  
Rocky Mountains ◽  
Comparative Psychology ◽  
Rocky Mountain ◽  
Mountain Region ◽  
Laboratory Studies ◽  
Preliminary Attempt ◽  
Complete Enumeration ◽  
Rocky Mountain Region ◽  
Lewis And Clark

A preliminary attempt is made to identify the progress of the study of animal behavior, from native bears to imported apes, in the Rocky Mountain region. The survey includes naturalistic encounters, ethological observations, and laboratory studies, but is not a complete enumeration of animal research in the Rocky Mountains.

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

Late Pleistocene and Holocene Seasonal Temperatures Reconstructed from Fossil Beetle Assemblages in the Rocky Mountains

1996 ◽  
Vol 46 (3) ◽  
pp. 311-318 ◽  
Author(s):  
Scott A. Elias
Keyword(s):  
Late Pleistocene ◽  
Rocky Mountains ◽  
Rocky Mountain ◽  
Mountain Region ◽  
Small Scale ◽  
Rocky Mountain Region ◽  
Winter Temperatures ◽  
Summer Warming ◽  
Beetle Assemblages ◽  
Climatic Range

Mutual Climatic Range (MCR) analysis was applied to 20 fossil beetle assemblages from 11 sites dating from 14,500 to 400 yr B.P. The fossil sites represent a transect of the Rocky Mountain region from northern Montana to central Colorado. The analyses yielded estimates of mean July and mean January temperatures. The oldest assemblage (14,500 yr B.P.) yielded mean July values of 10–11°C colder than present and mean January values 26–30°C colder than present. Postglacial summer warming was rapid, as indicated by an assemblage dating 13,200 yr B.P., with mean July values only 3–4°C cooler than modern. By 10,000 yr B.P., several assemblages indicate warmer-than-modern mean summer and winter values. By 9000 yr B.P., MCR reconstructions indicate that both summer and winter temperatures were already declining from an early Holocene peak. Mean July values remained above modern levels and mean January values remained below modern levels until 3000 yr B.P. A series of small-scale oscillations followed.

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.

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.

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