Palynology of six sections of Late Quaternary sediments from the Old Crow River, Yukon Territory

1973 ◽  
Vol 51 (3) ◽  
pp. 553-564 ◽  
Author(s):  
Sigrid Lichti-Federovich
Keyword(s):  
Late Quaternary ◽  
Yukon Territory ◽  
Quaternary Sediments ◽  
Pollen Assemblage ◽  
Alluvial Deposits ◽  
Pollen Stratigraphy ◽  
Tundra Vegetation ◽  
Pollen Diagrams ◽  
Shrub Tundra ◽  
Basin Fill

The Old Crow Plain, northern Yukon Territory, Canada, is a large flat lowland consisting of basin-fill sediments of Late Quaternary age. The modern Arctic treeline passes across the northern tip of the lowland, and much of the vegetation consists of tundra and shrub tundra, with scattered groves of spruce mainly on alluvial deposits. Steep scarps have been exposed by the downcutting of the Old Crow River in these basin-fill sediments, and good exposures of Late Quaternary sediments are available for investigation. Samples from six of these exposures were analyzed for pollen. Although many parts of the sections were barren, it has been possible to derive pollen diagrams with discrete pollen zones for the six sections, and four pollen assemblage types have been identified. Their occurrence in the stratigraphie sequence suggests the following pattern of pollen stratigraphy: the lowermost sedimentary units, probably deposited early in the interstadial following an Early Wisconsin glaciation, are of pollen assemblage types III (Glumiflorae–herb) or IV (Betula–herb), both indicative of tundra vegetation; the middle levels of the sediment show, consistently, pollen spectra of type II (Picea–Betula–Glumiflorae–herb), indicating forest groves with tundra, quite similar to the modern vegetation. The sediment underlying the Upper Glaciolacustrine Unit (correlative, according to Hughes (1969), with the Classical Wisconsin Stadial) yields pollen assemblage type III (Glumiflorae–herb), which is interpreted as indicating a rich and varied tundra. These vegetation reconstructions are consonant with a tentative palaeoclimatic interpretation in terms of a tripartite interstadial climate showing severe tundra climate – milder forest or forest–tundra climate – severe tundra climate. Two of the sections have incomplete pollen stratigraphy for the uppermost postglacial silts and peats. They suggest that vegetation similar to the present day became established in the Old Crow Plain in mid-postglacial time.

scholarly journals A late Quaternary record of eolian silt deposition in a maar lake, St. Michael Island, western Alaska

2003 ◽  
Vol 60 (1) ◽  
pp. 110-122 ◽  
Author(s):  
Daniel R. Muhs ◽  
Thomas A. Ager ◽  
Josh Been ◽  
J. Platt Bradbury ◽  
Walter E. Dean
Keyword(s):  
Lake Sediments ◽  
Late Quaternary ◽  
Geochemical Data ◽  
Unexpected Finding ◽  
The Holocene ◽  
Tundra Vegetation ◽  
Shrub Tundra ◽  
Loess Deposition ◽  
Maar Lake ◽  
Glacial Time

AbstractRecent stratigraphic studies in central Alaska have yielded the unexpected finding that there is little evidence for full-glacial (late Wisconsin) loess deposition. Because the loess record of western Alaska is poorly exposed and not well known, we analyzed a core from Zagoskin Lake, a maar lake on St. Michael Island, to determine if a full-glacial eolian record could be found in that region. Particle size and geochemical data indicate that the mineral fraction of the lake sediments is not derived from the local basalt and is probably eolian. Silt deposition took place from at least the latter part of the mid-Wisconsin interstadial period through the Holocene, based on radiocarbon dating. Based on the locations of likely loess sources, eolian silt in western Alaska was probably deflated by northeasterly winds from glaciofluvial sediments. If last-glacial winds that deposited loess were indeed from the northeast, this reconstruction is in conflict with a model-derived reconstruction of paleowinds in Alaska. Mass accumulation rates in Zagoskin Lake were higher during the Pleistocene than during the Holocene. In addition, more eolian sediment is recorded in the lake sediments than as loess on the adjacent landscape. The thinner loess record on land may be due to the sparse, herb tundra vegetation that dominated the landscape in full-glacial time. Herb tundra would have been an inefficient loess trap compared to forest or even shrub tundra due to its low roughness height. The lack of abundant, full-glacial, eolian silt deposition in the loess stratigraphic record of central Alaska may be due, therefore, to a mimimal ability of the landscape to trap loess, rather than a lack of available eolian sediment.

Late Quaternary History of Tundra Vegetation in Northwestern Alaska

1994 ◽  
Vol 41 (3) ◽  
pp. 306-315 ◽  
Author(s):  
Patricia M. Anderson ◽  
Patrick J. Bartlein ◽  
Linda B. Brubaker
Keyword(s):  
Vegetation Type ◽  
Late Quaternary ◽  
Vegetation Types ◽  
The Past ◽  
Modern Pollen ◽  
Qualitative Approaches ◽  
Tundra Vegetation ◽  
Shrub Tundra ◽  
History Of ◽  
Quaternary History

AbstractPollen analysis of a new core from Joe Lake indicates that the late Quaternary vegetation of northwestern Alaska was characterized by four tundra and two forest-tundra types. These vegetation types were differentiated by combining quantitative comparisons of fossil and modern pollen assemblages with traditional, qualitative approaches for inferring past vegetation, such as the use of indicator species. Although imprecisely dated, the core probably spans at least the past 40,000 yr. A graminoid-Salix tundra dominated during the later and early portions of the glacial record. The middle glacial interval and the transition from glacial to interglacial conditions are characterized by a graminoid-Betula-Salix tundra. A Populus forest-Betula shrub tundra existed during the middle potion of this transition, being replaced in the early Holocene by a Betula-Alnus shrub tundra. The modern Picea forest-shrub tundra was established by the middle Holocene. These results suggest that the composition of modem tundra communities in northwestern Alaska developed relatively recently and that throughout much of the late Quaternary, tundra communities were unlike the predominant types found today in northern North America. Although descriptions of vegetation variations within the tundra will always be restricted by the innate taxonomic limitations of their herb-dominated pollen spectra, the application of multiple interpretive approaches improves the ability to reconstruct the historical development of this vegetation type.

scholarly journals Late Quaternary Pollen Records and Vegetation History of the Southwest Yukon Territory: A Review

2007 ◽  
Vol 45 (2) ◽  
pp. 175-193 ◽  
Author(s):  
Xia-Cheng Wang ◽  
Marie-Anne Geurts
Keyword(s):  
Vegetation History ◽  
Late Quaternary ◽  
Late Glacial ◽  
Yukon Territory ◽  
Circulation System ◽  
Spruce Forest ◽  
Migration Routes ◽  
Shrub Tundra ◽  
History Of ◽  
Pollen Records

ABSTRACTThis paper is a summary of all known late Quaternary palynostratigraphic records from the southwest Yukon Territory. Thirty two pollen sites available by the end of 1988 are reviewed. Most pollen records in the region are of Holocene age. During the late-glacial to early Holocene, the southwest Yukon supported a herb-dominated tundra vegetation which was replaced by a birch-dominated shrub-tundra at about 10,000 yr BP. Spruce invaded the area between 9000 and 8600 yr BP at different localities, and a southward time transgression is visible in the Aishihik Basin. The current regional vegetation has been stable since 7600-8000 yr BP when dense spruce forest and/or spruce forest-tundra was established in most localities. In the Snag area, however, dense spruce forest developed only around 5700 yr BP, which is about 2000 years later than in the Aishihik Basin. The exotic pine pollen records in the region exhibit an interesting pattern, suggesting a frequent shift of the atmospheric circulation system. Anomalous records of alder pollen from the Aishihik Basin and adjacent regions suggest that alder has never been widespread in these areas due to aridity, and alder pollen is greatly overrepresented in pollen spectra. Spruce arrival dates suggest that further investigations in the Tintina Valley, Yukon River Valley, and Car-macks region might provide useful information concerning the spruce migration routes.

Late Quaternary vegetational history of the Black River region in northeastern Alaska

1988 ◽  
Vol 25 (1) ◽  
pp. 84-94 ◽  
Author(s):  
Patricia M. Anderson ◽  
Richard E. Reanier ◽  
Linda B. Brubaker
Keyword(s):  
Picea Glauca ◽  
Late Quaternary ◽  
Major Change ◽  
Migration Route ◽  
Herbaceous Species ◽  
Geographical Patterns ◽  
Pollen Diagrams ◽  
River Region ◽  
Shrub Tundra ◽  
History Of

Two pollen diagrams describe the previously unknown vegetational history of the Black River and Little Black River drain ages of northeastern Alaska. Tundra grew throughout much of the region between ca. 19 800 and 15 000 years BP. Prior to 18 000 years BP, the vegetation was dominated perhaps by xeric Cyperaceae communities, but apparently between ca. 18 000 and 15 000 years BP a more diverse herb tundra characterized the vegetation. Herbaceous species continued to be important in the vegetation until ca. 9700 years BP, although Betula nana–glandulosa and Salix species became more common after 15 000 years BP. At ca. 9700 years BP a major change in the vegetation occurred with the spread of Populus (probably P. balsamifera), B. nana–glandulosa, and Salix, possibly resulting in a mosaic of shrub tundra and Populus gallery forest. Picea glauca migrated into the Black River region ca. 7500 years BP, followed by Alnus ca. 7200 years BP and Picea mariana ca. 6000 years BP.Herb zone records from the Black River region support the hypothesis that eastern Beringian vegetation was characterized by a tundra mosaic prior to 14 000 years BP. Chronological and geographical patterns in the Populus subzone from eastern Beringia suggest that the expansion of Populus populations may not have been exclusively in response to climate change. Dates of Picea arrival on the western Porcupine Plateau indicate that this area probably was not an early Holocene migration route for Picea.

Late Quaternary chronology and environments of Square Lake, Torngat Mountains, Labrador

1989 ◽  
Vol 26 (10) ◽  
pp. 2130-2144 ◽  
Author(s):  
Peter U. Clark ◽  
Susan K. Short ◽  
Kerstin M. Williams ◽  
John T. Andrews
Keyword(s):  
Late Quaternary ◽  
Organic Soils ◽  
Pollen Record ◽  
Lake Ice ◽  
Tundra Vegetation ◽  
Major Transition ◽  
Shrub Tundra ◽  
Ice Retreat ◽  
Late Wisconsinan ◽  
Lake Ice Cover

Sediment, pollen, and diatom records from Square Lake, a small lake dammed by a segment of Saglek Moraine, cover the period of deposition of and deglaciation from the Saglek Moraine. The basal radiocarbon date (18 210 ± 1900 years BP) is on sediment contaminated by reworked pollen and is thus a maximum age. However, the date was measured on organic carbon recovered from glaciolacustrine couplets associated with deposition of the Saglek Moraine and thus establishes a Late Wisconsinan age for the Saglek Moraine. Vegetation on the ice-free upland surrounding Square Lake at this time was a sparse tundra vegetation dominated by grasses and herbs. The absence of diatoms indicates perennial lake-ice cover. A major transition is recorded by pollen and diatoms at > 8.5 ka. Vegetation probably remained sparse tundra, but birch and willow may have arrived in the area by 8 ka. Diatoms are first dominated by alkaliphil species, reflecting continued influence of glaciolacustrine sedimentation. An abrupt change in depositional environment ≥ 8 ka indicates ice retreat from the Saglek Moraine and start of nonglacial lacustrine sedimentation that has continued to the present. This was accompanied by an increase in organic matter, reflecting the newly established rich shrub tundra. At this time the diatoms also change, suggesting development of acidic organic soils around the lake. At 7.5 ka, diatoms indicate continued evolution of water chemistry and nutrient availability in the lake. Diatom concentrations and transfer function analyses of the pollen record identify the Holocene climatic optimum at 6.5 ka in the southern Torngat Mountains. The modern diatom flora was established at that time, but a decrease in diatom concentrations and estimated July temperatures suggest climatic deterioration in the area since 6.5 ka.

OSL ages and origin of Late Quaternary sediments in the North Transdanubian Hills (Hungary): timing of neotectonic activity

2010 ◽  
Vol 222 (1-2) ◽  
pp. 209-220 ◽  
Author(s):  
Edit Thamó-Bozsó ◽  
Árpád Magyari ◽  
Balázs Musitz ◽  
Attila Nagy
Keyword(s):  
Late Quaternary ◽  
Quaternary Sediments ◽  
Neotectonic Activity ◽  
The North

Chronology and stratigraphy of Late Quaternary sediments in the Konya Basin, Turkey: Results from the KOPAL Project

1999 ◽  
Vol 18 (4-5) ◽  
pp. 611-630 ◽  
Author(s):  
N. Roberts ◽  
S. Black ◽  
P. Boyer ◽  
W.J. Eastwood ◽  
H.I. Griffiths ◽  
...  
Keyword(s):  
Late Quaternary ◽  
Quaternary Sediments ◽  
Konya Basin
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