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.

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 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.

Holocene glacial history of the Lituya District, southeast Alaska

1985 ◽  
Vol 22 (6) ◽  
pp. 913-928 ◽  
Author(s):  
D. H. Mann ◽  
F. C. Ugolini
Keyword(s):  
Buried Soils ◽  
Glacial History ◽  
Southeast Alaska ◽  
Radiocarbon Dates ◽  
Relative Age ◽  
The Past ◽  
History Of ◽  
Organic Deposits ◽  
Glacial Periods ◽  
Regional Comparisons

Radiocarbon dates from the Lituya District of southeast Alaska indicate the occurrence of at least four glacial periods during the past 10 000 years. Further detail is added to the record by a relative-age chronology for moraines based on cross-cutting relationships, as well as soil, vegetation, and boulder weathering characteristics. The most recent deglaciation occurred approximately 350–500 years BP, ending advances begun shortly after 1500 years BP. The relative-age chronology for moraines indicates that at least three episodes of moraine building occurred during this period. Dates on logs in outwash and organic deposits in a moraine pond indicate glacial recession 1500–1900 years BP. This recession was preceded by advances beginning sometime after 3600 years BP and including several periods of moraine construction. Radiocarbon-dated basal organics in moraine ponds, buried soils, and overridden forest beds delimit a mid-Holocene advance ending before 5000 years BP and probably starting around 6000 years BP. Another advance probably occurred between 7400 and 9000 years BP; alternatively, it may have been earlier, but after 11 000 years BP. Regional comparisons are limited by the shortage of, and innate problems with, the glacial records, but do suggest that mid- and early Holocene advances were widespread in the southern Alaska region.

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.

Past and recent biodiversity profiling in ancient Lake Chalco Mexico by a metagenomics analysis

2021 ◽  
Author(s):  
Bárbara Moguel ◽  
Liseth Pérez ◽  
Luis David Alcaraz ◽  
Socorro Lozano-García ◽  
Luis Herrera-Estrella ◽  
...  
Keyword(s):  
Volcanic Belt ◽  
Environmental Dna ◽  
Radiocarbon Dates ◽  
The Past ◽  
Mexican Volcanic Belt ◽  
History Of ◽  
High Throughput Dna Sequencing ◽  
High Altitude Lake ◽  
Taxonomic Groups ◽  
The Relationship

<p>For decades, paleoecological studies in lake sediments have focused on reconstructing the environments of the past and explaining phenomena linked to climatic variations. Recent advances in high-throughput DNA sequencing have allowed access to environmental DNA (eDNA) and ancient sedimentary DNA (sedaDNA) as a new and efficient proxy for past and present biodiversity. The basin of Mexico (BM) is located in the central part of the Trans-Mexican Volcanic Belt at 2,200 m a.s.l.; with the southern portion harboring the Chalco sub-basin. Lake Chalco is one of the last remaining natural aquatic ecosystems within the ever-expanding urban area surrounding Mexico City. The paleoenvironmental history of this lake has been previously characterized using sedimentological and geochemical proxies, as well as preserved microfossils (diatoms, pollen) with a temporal framework based on multiple radiocarbon dates. However, information for the remaining taxonomic groups and metabolic pathways remained unexplored. Here, we present the first metagenomics-based study for the Holocene in a high-altitude lake in Central Mexico –Lake Chalco. We explored the relationship between the lake’s paleoenvironmental condition and estimations of taxonomic and metabolic profiles across the sedimentary sequence (2.5 meters long). Multiple biological and abiotic variables revealed three main environmental phases: 1) a cool freshwater lake (FW1: 11,500-11,000 cal years BP), 2) a warm hyposaline lake (HS2: 11,000-6,000 cal years BP), and 3) a temperate, subsaline lake (SS3, <6,000 cal years BP). We describe the structure of the microbiota community and taxonomy richness turnover in the three Holocene paleoenvironmental phases. During the past 12 000 years BP the most abundant domains in Lake Chalco sediments were Bacteria, followed by Archaea, and Eukarya (36,722 genera). The analysis of functional proteins showed high biodiversity with a total of 27,636,243 proteins identified, but it was only possible to annotate 3,227,398 of them. Also, we identified several genes associated with some relevant pathways, such as methanogenesis. Altogether, this study allowed us to reconstruct the natural history of lake Chalco and its surroundings.</p>

Dendrochronology and Late Holocene History of Bering Piedmont Glacier, Alaska

1999 ◽  
Vol 52 (2) ◽  
pp. 185-195 ◽  
Author(s):  
Gregory C. Wiles ◽  
Austin Post ◽  
Ernest H. Muller ◽  
Bruce F. Molnia
Keyword(s):  
Gulf Of Alaska ◽  
17Th Century ◽  
Glacial Retreat ◽  
General Sequence ◽  
Radiocarbon Dates ◽  
The Past ◽  
Tree Ring Data ◽  
Bering Glacier ◽  
Forested Areas ◽  
History Of

Fluctuations of the piedmont lobe of Bering Glacier and its sublobe Steller Glacier over the past two millennia are reconstructed using 34 radiocarbon dates and tree-ring data from 16 sites across the glaciers' forelands. The general sequence of glacial activity is consistent with well-dated fluctuations of tidewater and land-terminating glaciers elsewhere along the Gulf of Alaska. Extensive forested areas along 25 km of the Bering ice margin were inundated by glacio-lacustrine and glacio-fluvial sediments during a probable ice advance shortly before 500 cal yr A.D. Regrowth of forests followed the retreating ice as early as the 7th century A.D., with frequent interruptions of tree growth due to outwash aggradation. Forests overrun by ice and buried in outwash indicate readvance about 1080 cal yr A.D. Retreat followed, with ice-free conditions maintained along the distal portions of the forefield until the early 17th century after which the ice advanced to within a few kilometers of its outer Neoglacial moraine. Ice reached this position after the mid-17th century and prior to 200 yr ago. Since the early 20th century, glacial retreat has been punctuated by periodic surges. The record from forests overrun by the nonsurging Steller Lobe shows that this western ice margin was advancing by 1250 A.D., reaching near its outer moraine after 1420 cal yr A.D. Since the late 19th century, the lobe has dominantly retreated.

scholarly journals Glacial History of Kolahoi Glacier, Kashmir, India

1974 ◽  
Vol 13 (68) ◽  
pp. 279-283
Author(s):  
N. Ahmad ◽  
N. H. Hashimi
Keyword(s):  
Major Advance ◽  
Glacial History ◽  
The Past ◽  
History Of

Kolahoi Glacier is one of the longest glaciers in Kashmir and in the past it extended for at least 35 km. In the Pleistocene there were three advances of Kolahoi Glacier and the last one of them was a major advance when the glacier extended as far as Pahalgam.

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