Filters: Tags: Paleo and Holocene (X)
764 results (55ms)|
Filters
Date Range
Extensions Types
Contacts Categories |
This paper presents paleoecological analyses of 48 fossil arctic ground squirrel (Spermophilus parryii) middens (nests and caches) recovered from ice-rich loess sediments in the Klondike region of west-central Yukon Territory. AMS radiocarbon dates and stratigraphic association of middens with Dawson tephra (∼25 300 14C yr BP), indicate these paleoecological data reflect the onset of glacial conditions of early Marine Isotope Stage (MIS) 2 and terminal MIS 3 (∼24 000–29 450 14C yr BP). Plant macrofossils include at least 60 plant taxa, including diverse graminoids (Poa, Elymus trachycaulus, Kobresia myosuroides), steppe forbs (Penstemon gormanii, Anemone patens var. multifida, Plantago cf. canescens), tundra forbs...
Four intervals of late Holocene glacier advance are recognized from study of nine valley glaciers in the Wrangell and westernmost St. Elias Mountains of Alaska. The oldest glacial advance is recognized at the Nabesna and Barnard Glaciers where live radiocarbon ages suggest advance as early as 2700 cal. (calibrated) yr B.P. Two additional radiocarbon-dated advances are centered on cal. yr A.D. 300 and the beginning of the Little Ice Age about A.D. 1200. The best-documented Little Ice Age advances occurred during the mid-1600s through the 1800s and are recognized at all nine glaciers. These latter advances are dated by tree rings of trees overrun by glaciers in five glacier valley, by 17 radiocarbon dates, and by...
Categories: Publication;
Types: Citation;
Tags: P2-Changes in Plant and Animal Species Due to Climate Change,
Paleo and Holocene
A large increase in Betula during a narrow 1000 year window, ~13,800 years before present (YBP) in Alaska and Yukon corresponded in time with the extinction of mammoths and the arrival of humans. Pollen data indicate the increase in Betula during this time was widespread across Siberia and Beringia. We hypothesize that Betula increased due to a combination of a warming climate and reduced herbivory following the extinction of the Pleistocene mega herbivores. The rapid increase in Betula modified land surface albedo which climate-model simulations indicate would cause an average net warming of ~0.021°C per percent increase in high latitude (5373°N) Betula cover. We hypothesize that the extinction of mammoths increased...
Categories: Publication;
Types: Citation;
Tags: Paleo and Holocene,
Projecting Future States 3a-Future Vulnerability to Land use Change
Plant and insect macrofossil assemblages dating to the full-glacial (late Wisconsinan) are rare from eastern Beringia. Here we present an assemblage of fossil pollen, insect and plant macrofossils recovered from alluvium at the Bluefish Exposure, northern Yukon Territory. Nine AMS radiocarbon ages place these data between ca. 18,880–16,440 14C yr BP (22,313–19,597 cal. yr BP). These data indicate that xeric steppe, rich in bunchgrasses Poa and Elymus, Artemisia frigida and diverse forbs was interspersed within a mosaic of local vegetation types, including mid-rich fens, mesic graminoid meadows, steppe-tundra and herb-tundra. Macrofossils and minor pollen of tundra forbs suggest steppe-tundra plant associations within...
This paper presents paleoecological analyses of 48 fossil arctic ground squirrel (Spermophilus parryii) middens (nests and caches) recovered from ice-rich loess sediments in the Klondike region of west-central Yukon Territory. AMS radiocarbon dates and stratigraphic association of middens with Dawson tephra (∼25 300 14C yr BP), indicate these paleoecological data reflect the onset of glacial conditions of early Marine Isotope Stage (MIS) 2 and terminal MIS 3 (∼24 000–29 450 14C yr BP). Plant macrofossils include at least 60 plant taxa, including diverse graminoids (Poa, Elymus trachycaulus, Kobresia myosuroides), steppe forbs (Penstemon gormanii, Anemone patens var. multifida, Plantago cf. canescens), tundra forbs...
Late Pleistocene - early Holocene plant macrofossils and pollen from the Yukon Flats, central Alaska
Dramatic climate changes and expansion of new biomes characterize the late Pleistocene - early Holocene of eastern Beringia. Analysis of plant macrofossils and pollen from three different sites in the Yukon Flats, central Alaska, record the past vegetation during the late Pleistocene - early Holocene (ca. 11,500-6,900 14 C yrs BP) transition. The first paper deals with plant macrofossils associated with one of the earliest post glacial beaver dams (ca. 9,300 14 C yrs BP) found in central Alaska. Vegetation reconstruction suggests a warmer than modern climate during the early Holocene. The second paper examines eight paleosols and their associated plant macrofossils and pollen within eolian deposits at two sites...
Categories: Publication;
Types: Citation;
Tags: Baseline 5-Data,
Beaver,
Paleo and Holocene,
Species of Concern: Mammals
The late Pleistocene Dawson tephra was deposited by one of the largest Quaternary eruptions in northwestern North America. Its distribution is known sparsely from sites near the source area in southwestern Alaska and central Yukon Territory, where more than 20 occurrences are documented in the Klondike region. Dawson tephra erupted about 25 , 300 14 C yr BP , near the onset of the last glaciation, and provides a stratigraphic marker across Eastern Beringia. We report radiocarbon ages, paleobotanical data, and cryostratigraphic observations from a new Dawson tephra locale at Goldbottom Creek, in the Klondike region of Yukon Territory, which collectively indicate that the eruption occurred in the late winter or early...
Response of the Porcupine and Old Crow rivers in northern Yukon, Canada, to Holocene climatic change
A major aggradation took place from 8000 BP to 4000 BP in the Porcupine and Old Crow rivers, northern Yukon. The aggradation was a consequence of an increase in flow and the result of a perturbation of the permafrost active layer following the early-Holocene climatic warming of northwestern Canada. These findings are useful for improving our understanding of how natural landscapes and river systems evolved in regions that experienced a permafrost history and, more particularly, an increase in climatic warming. This article also contributes to an improved understanding of natural landscape evolution along the Porcupine and Old Crow rivers in eastern Beringia, where there has been much interest in questions related...
Categories: Publication;
Types: Citation;
Tags: P2-Changes in Plant and Animal Species Due to Climate Change,
Paleo and Holocene
Species interactions form food webs, impacting community structure and, potentially, ecological dynamics. It is likely that global climatic perturbations that occur over long periods of time have a significant influence on species interaction patterns. Here, we integrate stable isotope analysis and network theory to reconstruct patterns of trophic interactions for six independent mammalian communities that inhabited mammoth steppe environments spanning western Europe to eastern Alaska (Beringia) during the Late Pleistocene. We use a Bayesian mixing model to quantify the contribution of prey to the diets of local predators, and assess how the structure of trophic interactions changed across space and the Last Glacial...
|
