scholarly journals Short Notes: Note on the “Arikaree Stade” of the Rocky Mountains Neoglacial

1971 ◽  
Vol 10 (58) ◽  
pp. 143-144
Author(s):  
William Mahaney
Keyword(s):  
Growth Rate ◽  
Rocky Mountains ◽  
Colorado Front Range ◽  
Rate Curve ◽  
Front Range ◽  
Rhizocarpon Geographicum ◽  
Alternative Type ◽  
The Temple

AbstractNeoglacial deposits in the Indian Peaks section of the Colorado Front Range have been dated lichenometrically by recourse to a growth-rate curve developed for Rhizocarpon geographicum and three glacial fluctuations of the Temple Lake (4500–2700 B.P. ), “Arikaree” (1900–1000 B.P.) and Gannett Peak (300–50 B.P.) have been recognized and identified by Benedict (1968). Recent soil investigations on neoglacial deposits suggest the need to define an alternative type “Arikaree” in the Indian Peaks.

scholarly journals Short Notes: Note on the “Arikaree Stade” of the Rocky Mountains Neoglacial

1971 ◽  
Vol 10 (58) ◽  
pp. 143-144 ◽  
Author(s):  
William Mahaney
Keyword(s):  
Growth Rate ◽  
Rocky Mountains ◽  
Colorado Front Range ◽  
Rate Curve ◽  
Front Range ◽  
Rhizocarpon Geographicum ◽  
Alternative Type ◽  
The Temple

AbstractNeoglacial deposits in the Indian Peaks section of the Colorado Front Range have been dated lichenometrically by recourse to a growth-rate curve developed forRhizocarpon geographicumand three glacial fluctuations of the Temple Lake (4500–2700B.P.), “Arikaree” (1900–1000B.P.) and Gannett Peak (300–50B.P.) have been recognized and identified by Benedict (1968). Recent soil investigations on neoglacial deposits suggest the need to define an alternative type “Arikaree” in the Indian Peaks.

scholarly journals Recent Glacial History of an Alpine Area in the Colorado Front Range, U.S.A.: I. Establishing a Lichen-Growth Curve

1967 ◽  
Vol 6 (48) ◽  
pp. 817-832 ◽  
Author(s):  
James B. Benedict
Keyword(s):  
Growth Curve ◽  
Average Rate ◽  
Colorado Front Range ◽  
Ground Moraine ◽  
Front Range ◽  
Exposure Age ◽  
Rhizocarpon Geographicum ◽  
Valley Glacier ◽  
History Of ◽  
Lichen Growth

A lichen-growth curve has been developed for dating Recent glacial and periglacial deposits in the Indian Peaks area of the Colorado Front Range.Rhizocarpon geographicumwas selected for the study because of its long life span and consistent size-age relationship. The species grows at different rates in different micro-environments, with moisture, stability of substrate and length of snow-free growing season having the greatest effect. Growth rates were determined indirectly, by measuring the maximum diameters of circular or nearly circular thalli growing on surfaces of known exposure age. Measurements were made on 24 historically dated surfaces, ranging in age from 25 to 69 yr., and on three radiocarbon-dated surfaces, including (1) mudflow levees younger than 180 yr., (2) a rock wall built by prehistoric Indians about 970 yr. ago, and (3) ground moraine deposited by a retreating valley glacier about 2,460 radiocarbon years ago.R. geographicurrzgrows very rapidly (14. mm./100 yr.) during the First 100 yr. of its life. Growth then slows to an average rate of 3.3 mm./100 yr. The completed growth curve is believed to be suitable for dating deposits at least as old as 3,000 yr.

scholarly journals Recent Glacial History of an Alpine Area in the Colorado Front Range, U.S.A.: II. Dating the Glacial Deposits

1968 ◽  
Vol 7 (49) ◽  
pp. 77-87 ◽  
Author(s):  
James B. Benedict
Keyword(s):  
Local Development ◽  
Colorado Front Range ◽  
Front Range ◽  
Glacial History ◽  
Glacial Deposits ◽  
Radiocarbon Dates ◽  
The Past ◽  
Rhizocarpon Geographicum ◽  
History Of ◽  
Mountain Glaciation

AbstractRecent glacial deposits in the Indian Peaks area of the Colorado Front Range have been dated lichenometricaily, using a growth curve developed locally forRhizocarpon geographicum. Radiocarbon dates, where available, tend to support the lichen chronology. Three distinct intervals of glaciation, each consisting of several minor pulsations, have occurred in the area during the past 4500 years. The earliest advance (Temple Lake Stade) is dated at 2500–700 b.c. A later advance (Arikaree Stade) began in about a.d. 100 and ended in a.d. 1000. The most recent advance (Gannett Peak Stade) is dated at a.d. 1650–1850. It remains to be seen whether the Arikaree Stade was purely a local development or whether glaciers were advancing elsewhere in the cordilleran region during this interval. Alluviation on the plains east of the Colorado Front Range seems to have occurred during the waning stages of mountain glaciation.

scholarly journals Recent Glacial History of an Alpine Area in the Colorado Front Range, U.S.A.: I. Establishing a Lichen-Growth Curve

1967 ◽  
Vol 6 (48) ◽  
pp. 817-832 ◽  
Author(s):  
James B. Benedict
Keyword(s):  
Growth Curve ◽  
Average Rate ◽  
Colorado Front Range ◽  
Ground Moraine ◽  
Front Range ◽  
Exposure Age ◽  
Rhizocarpon Geographicum ◽  
Valley Glacier ◽  
History Of ◽  
Lichen Growth

A lichen-growth curve has been developed for dating Recent glacial and periglacial deposits in the Indian Peaks area of the Colorado Front Range. Rhizocarpon geographicum was selected for the study because of its long life span and consistent size-age relationship. The species grows at different rates in different micro-environments, with moisture, stability of substrate and length of snow-free growing season having the greatest effect. Growth rates were determined indirectly, by measuring the maximum diameters of circular or nearly circular thalli growing on surfaces of known exposure age. Measurements were made on 24 historically dated surfaces, ranging in age from 25 to 69 yr., and on three radiocarbon-dated surfaces, including (1) mudflow levees younger than 180 yr., (2) a rock wall built by prehistoric Indians about 970 yr. ago, and (3) ground moraine deposited by a retreating valley glacier about 2,460 radiocarbon years ago. R. geographicurrz grows very rapidly (14. mm./100 yr.) during the First 100 yr. of its life. Growth then slows to an average rate of 3.3 mm./100 yr. The completed growth curve is believed to be suitable for dating deposits at least as old as 3,000 yr.

scholarly journals Recent Glacial History of an Alpine Area in the Colorado Front Range, U.S.A.: II. Dating the Glacial Deposits

1968 ◽  
Vol 7 (49) ◽  
pp. 77-87 ◽  
Author(s):  
James B. Benedict
Keyword(s):  
Local Development ◽  
Colorado Front Range ◽  
Front Range ◽  
Glacial History ◽  
Glacial Deposits ◽  
Radiocarbon Dates ◽  
The Past ◽  
Rhizocarpon Geographicum ◽  
History Of ◽  
Mountain Glaciation

AbstractRecent glacial deposits in the Indian Peaks area of the Colorado Front Range have been dated lichenometricaily, using a growth curve developed locally for Rhizocarpon geographicum. Radiocarbon dates, where available, tend to support the lichen chronology. Three distinct intervals of glaciation, each consisting of several minor pulsations, have occurred in the area during the past 4500 years. The earliest advance (Temple Lake Stade) is dated at 2500–700 b.c. A later advance (Arikaree Stade) began in about a.d. 100 and ended in a.d. 1000. The most recent advance (Gannett Peak Stade) is dated at a.d. 1650–1850. It remains to be seen whether the Arikaree Stade was purely a local development or whether glaciers were advancing elsewhere in the cordilleran region during this interval. Alluviation on the plains east of the Colorado Front Range seems to have occurred during the waning stages of mountain glaciation.

The 1990 Valentine's Day Arctic Outbreak. Part I: Mesoscale and Microscale Structure and Evolution of a Colorado Front Range Shallow Upslope Cloud

1995 ◽  
Vol 34 (7) ◽  
pp. 1481-1511 ◽  
Author(s):  
Roy M. Rasmussen ◽  
Ben C. Bernstein ◽  
Masataka Murakami ◽  
Greg Stossmeister ◽  
Jon Reisner ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Transition Zone ◽  
Liquid Water ◽  
Rocky Mountains ◽  
Supercooled Liquid ◽  
Colorado Front Range ◽  
Neutral Stability ◽  
Strong Wind ◽  
Front Range ◽  
Low Level

Abstract The mesoscale and microscale structure and evolution of a shallow, upslope cloud is described using observations obtained during the Winter Icing and Storms Project (WISP) and model stimulations. The upslope cloud formed within a shallow arctic air mass that moved into the region east of the Rocky Mountains between 12 and 16 February and contained significant amounts of supercooled liquid water for nearly 30 h. Two distinct layers were evident in the cloud. The lower layer was near neutral stability (boundary layer air) and contained easterly upslope flow. The upper layer (frontal transition zone) was thermodynamically stable and contained southerly flow. Overlying the upslope cloud was a dry, southwesterly flow of 20–25 m s −1, resulting in strong wind shear near cloud top. Within 10 km of the Rocky Mountain barrier, easterly low-level flow was lifted up and over the mountains. The above-described kinematic and thermodynamic structure produced three distinct mechanisms leading to the production of supercooled liquid water: 1) upslope flow over the gently rising terrain leading into the Colorado Front Range, up the slopes of the Rocky Mountains and over local ridges, 2)upglide flow within a frontal transition zone, and 3) turbulent mixing in the boundary layer. Supercooled liquid water was also produced by 1) upward motion at the leading edge of three cold surges and 2) vertical motion produced by low-level convergence in the surface wind field. Large cloud droplets were present near the top of this cloud (approximately 50-µm diameter), which grew by a direct coalescence process into freezing drizzle in regions of the storm where the liquid water content was greater than 0.25 g m −3 and vertical velocity was at 10 cm s −1 Ice crystal concentrations greater than 1 L−1 were observed in the lower cloud layer containing boundary layer air when the top of the boundary layer air when the top of the boundary layer was colder than −12°C. The upper half of the cloud was ice-free despite temperatures as low as −15°C, resulting in long-lived supercooled liquid water in this region of the cloud.

Sign in / Sign up

Export Citation Format

Share Document