scholarly journals Evaluation of Amino Acid Composition as a Geochronometer in Buried Soils on Mount Kenya, East Africa

2007 ◽  
Vol 40 (2) ◽  
pp. 171-183 ◽  
Author(s):  
William C. Mahaney ◽  
Michael G. Boyer ◽  
Nathaniel W. Rutter
Keyword(s):  
Amino Acid ◽  
East Africa ◽  
Aspartic Acid ◽  
Age Dating ◽  
Buried Soils ◽  
Radiocarbon Dates ◽  
Radiocarbon Age ◽  
Acid Ratio ◽  
History Of ◽  
Quaternary History

ABSTRACT A sequence of surface and buried paleosols from the slopes of Mount Kenya, East Africa, has been identified and dated by radiocarbon and amino acid dating techniques in order to elucidate the Quaternary history of the area. Buried paleosols vary in radiocarbon age from 900 to > 40,000 yrs BP. They have developed in glacial and periglacial deposits of variable texture, consisting of a high percentage of clasts of phonolite, basalt and syenite. All but two paleosols are located in the Afroalpine zone (above 3200 m). D/L ratios of amino acids in Ab horizons were determined in order to establish their reliability for relative age dating. Alanine, aspartic acid, glutamic acid, leucine, valine, and phenylalanine were routinely analyzed. Aspartic acid, as in other cases, proved reliable yielding remarkably consistent results, with higher ratios corresponding to increasing age. Other acids analyzed showed distinct trends, although not as convincing as aspartic acid. In most cases, the aspartic acid ratio/ age relationships were supported by radiocarbon dates. D/L ratios of aspartic acid varied from approximately 0.07 for modern samples, to approximately 0.45 in samples > 40,000 years old.

The last interglacial–glacial cycle, Clyde foreland, Baffin Island, N.W.T.: stratigraphy, biostratigraphy, and chronology

1977 ◽  
Vol 14 (12) ◽  
pp. 2824-2857 ◽  
Author(s):  
G. H. Miller ◽  
J. T. Andrews ◽  
S. K. Short
Keyword(s):  
Amino Acid ◽  
Marine Sediments ◽  
Baffin Island ◽  
Buried Soils ◽  
Last Interglacial ◽  
Pollen Assemblage ◽  
Outlet Glacier ◽  
Radiocarbon Dates ◽  
Last Glaciation

A study of the stratigraphic sequence (14C and amino acid age control), marine bivalve faunal changes, and palynology of buried soils and organic-rich sediment collected from the Clyde Foreland Formation in the extensive cliff sections of the Clyde foreland, eastern Baffin Island, N.W.T., suggests the following last interglacial – Foxe (last glaciation) glacial – present interglacial sequence.(1) Cape Christian Member (ca. 130 000 years BP?)Consists of the Sledgepointer till overlain by the Cape Christian marine sediments. In situ molluscan fauna, collected from the marine sediments, contain a moderately warm bivalve assemblage. A well-developed soil that formed on the marine sediments (Cape Christian soil) contains an interglacial pollen assemblage dominated by dwarf birch. U-series dates of > 115 000 and ca. 130 000 years BP on molluscs from the Cape Christian marine sediments suggest that they were deposited during the last interglaciation, here termed the Cape Christian Interglaciation. The development of a subarctic pollen assemblage in the Cape Christian soil has not been duplicated during the present interglaciation, suggesting higher summer temperatures and perhaps a duration well in excess of 10 000 years for the last interglaciation.(2) Kuvinilk MemberConsists of fossiliferous marine sediments, locally divided by the Clyde till into upper and lower units. The Clyde till was deposited by the earliest and most extensive advance of the Foxe (last) Glaciation. Kuvinilk marine sediments both under- and overlying the Clyde till contain the pecten Chlamys islandicus, indicating that the outlet glacier advanced into a subarctic marine environment. Amino acid ratios from in situ pelecypod shells abovę and below the Clyde till are not statistically different, but contrast markedly with ratios obtained from the same species in the Cape Christian Member. Organic horizons within the Kuvinilk marine sediments contain a relatively rich pollen assemblage, although 'absolute' counts are low.(3) Kogalu Member (> 35 00014C years BP)Sediments of the Kogalu Member unconformably overlie those of the Kuvinilk Member, but are of a similar character. The dominant sediments are marine in origin, but in places are divided into upper and lower units by the Ayr Lake till. Amino acid ratios from in situ shells above and below the Ayr Lake till are indistinguishable, but substantially less than those in the Kuvinilk Member, suggesting the two members are separated by a considerable time interval. Radiocarbon dates on shells in the Kogalu marine sediments range from 33 000 to 47 700 years BP, but these may be only minimum estimates. The sea transgressed to a maximum level 70–80 m asl, coincident with the glacial maximum. Subarctic marine fauna of interstadial–interglacial character occur within the Kogalu marine sediments.(4) Eglinton Member (10 000 years BP to present)A major unconformity exists between the Kogalu and Eglinton Members. Ravenscraig marine sediments were deposited during an early Holocene marine transgression–regression cycle; the oldest dates on these sediments are ca. 10 000 years BP. Locally a vegetation mat occurs at the base or within the Ravenscraig unit. Pollen from these beds is sparse, but indicates a terrestrial vegetation assemblage as diverse as that of today. There is no evidence that Laurentide Ice reached the foreland during the last 30 000 years. Eolian sands that overlie a soil developed on the marine sediments record a late Holocene climatic deterioration. Pollen in organic-rich sediments at the base of, and within, the eolian sands record a vegetation shift in response to climatic change.

Late Quaternary history of the Lake O'Hara region, British Columbia – an evaluation of sedimentation rates and bulk amino acid ratios in lacustrine records

1988 ◽  
Vol 25 (7) ◽  
pp. 1037-1048 ◽  
Author(s):  
Mel A. Reasoner ◽  
Nathaniel W. Rutter
Keyword(s):  
Amino Acid ◽  
Aspartic Acid ◽  
Sedimentation Rate ◽  
River Sediments ◽  
Sedimentation Rates ◽  
Rate Data ◽  
Radiocarbon Dates ◽  
Clastic Sediments ◽  
Lake Cores ◽  
Total Sedimentation

Lake O'Hara (subalpine) and Opabin Lake (alpine) are situated directly adjacent to a high section of the Continental Divide in the central Canadian Rocky Mountains. Core samples recovered from the lakes show a consistent stratigraphy comprising gyttja and underlying inorganic clastic sediments. The gyttja contains Bridge River (2350 years BP) and Mazama (6800 years BP) tephras and is separated from the lower clastic sediments by a sharp, conformable contact. Radiocarbon dates obtained from conifer needles, extracted from directly above the contact, indicate that deglaciation had proceeded upvalley from the O'Hara basin priorto ca. 10 100 years BP. Preliminary palaeobotanical and macrofossil data suggest that a Pinus–Abies forest with lesser Picea was established in the vicinity of Lake O'Hara by this time. Consequently, the minimum age of moraine systems situated downvalley from Lake O'Hara is Late Wisconsinan.Mean annual sedimentation rates were derived from sediment thickness data from 14 Lake O'Hara and 2 Opabin Lake cores. Averaged total sedimentation rate values from the Lake O'Hara cores are 0.13 mm/year (post-Bridge River), 0.13 mm/year (Mazama – Bridge River) and 0.05 mm/year (11 000 years BP – Mazama). Averaged total sedimentation rate values from the Opabin Lake cores are 0.19 mm/year (post-Bridge River), 0.07 mm/year (Mazama – Bridge River), and 0.06 mm/year (8530 years BP – Mazama). Higher total sedimentation rates in post-Bridge River sediments of Opabin Lake are presumably related to climatic conditions associated with more extensive upvalley ice during the last ca. 2300 years. Highly variable sedimentation rate data obtained from the Lake O'Hara cores suggest that the use of sedimentation rate data as a proxy record of upvalley glacial activity is inappropriate in the Lake O'Hara setting where inflowing glacial stream systems are interrupted by upvalley lake basins.Aspartic acid D/L ratios were derived from bulk gyttja samples of known age from seven Lake O'Hara and one Opabin Lake core. In all but two cases, aspartic acid D/L ratios increase consistently with respect to sediment age. The increasing downcore trends in the aspartic acid D/L ratios suggest the possibility of using amino acid data from bulk gyttja samples as a check for reworking in cases where chronostratigraphic markers are absent.

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.

Late Quaternary Glacial History of George VI Sound Area, West Antarctica

1982 ◽  
Vol 18 (3) ◽  
pp. 243-267 ◽  
Author(s):  
Chalmers M. Clapperton ◽  
David E. Sugden
Keyword(s):  
Amino Acid ◽  
Late Quaternary ◽  
Ice Age ◽  
Dry Valleys ◽  
West Antarctica ◽  
Ice Shelf ◽  
Ice Caps ◽  
Climatic Control ◽  
Acid Ratio ◽  
History Of

AbstractDuring the last glacial maximum in West Antarctica separate ice caps developed on Alexander Island and on Palmer Land, became confluent in George VI Sound, and discharged northward from latitude 72° S. Radiocarbon (>32,000 yr) and amino acid (approximately 120,000 yr) age determinations on shell fragments (Hiatella solida) found in basal till suggest a Wisconsin age for the glaciation that incorporated them. The pattern of ice flow differed from that deduced for this area in the CLIMAP reconstruction. Following the maximum stage, there was a stadial event when outlet valley glaciers flowed from smaller ice caps into George VI Sound. More widespread recession permitted the George VI ice shelf to deposit Palmer Land erratics on eastern Alexander Island before isostatic recovery raised them to final elevations of about 82 m. The ice shelf may have been absent at about 6500 yr B.P., when large barnacles (Bathylasma corolliforme) were living in the sound. Small glaciers readvanced to form at least two terminal moraines before the ice shelf re-formed and incorporated the barnacle shells into its moraine on Alexander Island. The shells gave a 14C age (corrected for Antarctic conditions) of about 6500 yr B.P. and an amino acid ratio consistent with a Holocene age. Valley glaciers readvanced over the ice-shelf moraine before oscillations of both valley glaciers and the ice shelf led to the formation of the present sequence of contiguous ice-cored moraines, probably during the Little Ice Age. Such oscillations may represent a climatic control not yet observed in the dry valleys of Victoria Land, the only other part of Antarctica studied in detail for glacier fluctuations.

Late Quaternary Glacial and Climatic History of Northern Cumberland Peninsula, Baffin Island, N.W.T., Canada

1973 ◽  
Vol 3 (4) ◽  
pp. 561-583 ◽  
Author(s):  
Gifford H. Miller
Keyword(s):  
Late Quaternary ◽  
Climatic Conditions ◽  
Age Dating ◽  
Radiocarbon Dates ◽  
Ice Cap ◽  
Ice Coverage ◽  
Organic Horizons ◽  
History Of ◽  
Marine Facies ◽  
Reported Data

AbstractRadiocarbon dates on molluses in marine facies associated with glacial deposits in northern Cumberland Peninsula indicate both main fiord (Laurentide) ice and local glaciers remained at their late Wisconsin maxima until ca. 8000 BP. Essentially continuous deglaciation followed; local corrie glaciers melted out by 7100 BP and by 5500 BP fiord glaciers had receded behind the present margin of the Penny Ice Cap. The Hypsithermal warm interval probably lasted from ca. 8000 to 5000 BP. Lichenometry and radiocarbon dates on peat and buried organic horizons delimit a detailed Neoglacial chronology. Of 46 outlet and corrie glaciers investigated, the oldest Neoglacial moraines are dated lichenometrically at 3200 ± 600 BP. Subsequent advances terminated immediately prior to ca. 1650, 780, 350, and 65 yr BP, the most recent of which marked the most extensive ice coverage during the Neoglacial. The highest occurrence of lateral moraines from late Wisconsin advances of local and Laurentide ice suggest that at the late Wisconsin glacial maximum, depression of snowline varied from 450 m below present at the coast to 350 m below present level in the vicinity of the Penny Ice Cap. Moraines, surrounded by glacial ice and lying above the present steady-state ELA, suggest that during the Hypsithermal snowline was up to ca. 200 m above its present elevation. A radiometrically controlled reconstruction of relative summer paleotemperatures for the postglacial derived independently of lichenometry agrees well with the lichenometric age dating of moraines. The data suggest that between ca. 1650 and 900 BP climatic conditions were unfavorable for glacier growth, whereas the period ca. 800-65 yr BP was one of general glacial activity. During the last decade permanent snow cover has been increasing in the area. Previously reported data on climatic trends in the Canadian Arctic based on palynological analyses are similar to the chronology reported here.

scholarly journals Purification of a phosphoprotein from chromatin of rat liver

1979 ◽  
Vol 183 (1) ◽  
pp. 147-156 ◽  
Author(s):  
P K Chan ◽  
C C Liew
Keyword(s):  
Amino Acid ◽  
Glutamic Acid ◽  
Aspartic Acid ◽  
Rat Liver ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Basic Amino Acid ◽  
Phosphate Content ◽  
Acid Ratio ◽  
Chromatin Proteins

A simple and effective method to purify a phosphoprotein (B2) (Mr 68,000, pI 6.2-8) from phenol-soluble non-histone chromatin proteins of rat liver is described. The purification involved only two steps, CM-cellulose chromatography and preparative SDS/polyacrylamide (10%)-gel electrophoresis. The purified phosphoprotein B2 was shown to be homogeneous by SDS/polyacrylamide-gel electrophoresis. The yield was 2% of total non-histone chromatin proteins. The acidic to basic amino acid ratio of phosphoprotein B2 was less than 1, with high contents of glutamic acid, aspartic acid, arginine, lysine, glycine and alanine. The phosphate content of this protein is 0.3%.

Early Man in Arizona: The Pollen Evidence

1963 ◽  
Vol 29 (1) ◽  
pp. 67-73 ◽  
Author(s):  
Paul S. Martin
Keyword(s):  
Pollen Analysis ◽  
High Plains ◽  
Pollen Record ◽  
Desert Grassland ◽  
Alluvial Deposits ◽  
Radiocarbon Dates ◽  
Radiocarbon Age ◽  
Pollen Content ◽  
History Of ◽  
Sulphur Spring

AbstractUnder the classic Bryan-Antevs model the climatic history of the Southwest has been divided into (1) pluvial, (2) early postpluvial or Anathermal, (3) mid-postpluvial or Altithermal, (4) late postpluvial or Medithermal. Pollen analysis of radiocarbon-dated pluvial deposits shows that the desert grassland of southern Arizona and the short grassland of the Texas High Plains were invaded by a pine forest or pine savanna during the last pluvial period. Sulphur Spring-age alluvial deposits at Double Adobe, dated as pluvial in age by Sayles and Antevs, do not contain the pine-pollen record associated with pluvial conditions elsewhere; six radiocarbon dates from deep alluvial deposits at Double Adobe range from 7756 to 9350 years B.P. On the basis of pollen content and radiocarbon-age estimates, the beds are of early postpluvial rather than pluvial age, and thus the Sulphur Spring-stage artifacts found there are also early postpluvial in age.Under the Bryan-Antevs model the Altithermal, 7500-4000 B.P., is considered an especially hot, dry period. Sediments associated with three radiocarbon dates within this interval contain slightly more pollen of mesic and hygric indicators than do sediments postdating the Altithermal. Interpreting the results literally, the Altithermal was wetter, not hotter and drier, than at present. The limitations of pollen analysis are not fully understood. But the traditional view of a hot, dry Altithermal in southern Arizona cannot be verified from fossil pollen evidence available to date.

Geomorphology and Quaternary History of the Mackenzie River Valley near Fort Good Hope, N.W.T., Canada

1973 ◽  
Vol 10 (1) ◽  
pp. 26-41 ◽  
Author(s):  
J. Ross Mackay ◽  
W. H. Mathews
Keyword(s):  
Late Glacial ◽  
Sharp Change ◽  
Radiocarbon Dates ◽  
Plunge Pool ◽  
Free Drainage ◽  
History Of ◽  
Quaternary History ◽  
Abandoned Channels ◽  
Floodplain Sediments ◽  
Mackenzie River

The Mackenzie River displays a sharp change in geomorphic character at The Ramparts, a postglacially-developed rock-walled canyon near Fort Good Hope, N.W.T. Upstream for at least 70 km the river is cut into late-glacial and early postglacial lacustrine, deltaic, and floodplain sediments with radiocarbon dates of 11 000 to 11 500 years. These sediments are overlain by peat dating back 6120 radiocarbon years. Downstream the river reoccupies, for more than 350 km, a Pleistocene channel containing glacial and fluvial sediments yielding only dates beyond the range of carbon dating. Abandoned channels west of The Ramparts record the overflow, in early postglacial time, from a rock-rimmed lake athwart the newly developed Mackenzie drainage. The deepest of the channels, believed to have been abandoned in mid-postglacial time, contained a major waterfall with its plunge-pool floor close to present sea level. Free drainage from the foot of the falls to the ocean at the time it operated is indicated. Erosion continues along the Mackenzie River above The Ramparts but some aggradation occurs below it. Permafrost thaw and heavy rainfall contribute to landsliding along the river banks in both segments.

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