Late Quaternary vegetation of the Aleutian Islands, southwestern Alaska

1990 ◽  
Vol 68 (6) ◽  
pp. 1320-1326 ◽  
Author(s):  
Calvin J. Heusser
Keyword(s):  
Late Quaternary ◽  
Thickness Distribution ◽  
Patch Dynamics ◽  
Volcanic Eruptions ◽  
Ice Age ◽  
Aleutian Islands ◽  
Fossil Pollen ◽  
History Of ◽  
Tephra Layers ◽  
Radiocarbon Chronology

Late Quaternary vegetational history of the Aleutian Islands is interpreted from fossil pollen and spore stratigraphy and radiocarbon chronology of sections of mires on the islands of Attu, Adak, Atka, and Umnak. Mires postdate the withdrawal of ice-age glaciers between approximately 12 000 and 10 000 years ago with the exception of the mire on Attu Island, where deglaciation apparently began as late as 7000 years ago. No uniform pattern of change in Pacific coastal tundra communities is evident in the fossil assemblages. Pollen assemblages, consisting variably of Gramineae, Cyperaceae, Empetrum, Umbelliferae, Salix, Ranunculaceae, Compositae, Polypodiaceae, and Lycopodium, reflect conditions in effect in different sectors of the Aleutian chain. Climate, soil, topography, volcanism, and seismic activity are noteworthy parameters influencing vegetation composition and distribution. Volcanism has been of major importance, as shown by thickness, distribution, and frequency of tephra layers that number 5 on Attu, 24 on Adak, 17 on Atka, and 5 on Umnak. A repeated condition of patch dynamics, created in the main by recurrent volcanic eruptions with widespread accompanying ashfalls, has apparently overprinted the effects of climatic change. Key words: Aleutian Islands, Quaternary, vegetation, fossil pollen, volcanism.

scholarly journals Late-Quaternary Vegetational and Climatic History of the Yellowstone/Grand Teton Region

1988 ◽  
Vol 12 ◽  
pp. 189-192
Author(s):  
Cathy Barnosky
Keyword(s):  
Environmental History ◽  
Late Quaternary ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Fire Frequency ◽  
Ice Age ◽  
Sediment Chemistry ◽  
History Of ◽  
Climatic History

The research underway has focused on two different aspects of the environmental history of the Yellowstone/Grand Teton region. One objective has been to examine the long-term vegetational and climatic history of Jackson Hole, the Pinyon Peak Highlands, and Yellowstone Park since the end of late Pinedale glaciation, about 14,000 years ago. Fossil pollen in sediment cores from lakes in the region is being analyzed to clarify the nature and composition of ice-age refugia, the rate and direction of plant migrations in the initial stages of reforestation, and the long-term stability of postglacial communities. Sedimentary charcoal also is being examined to reconstruct fire frequency during different climatic regions and different vegetation types in the past. This information is necessary to assess the sensitivity of plant communities to environmental change and to understand postglacial landscapes of the northern rocky Mountains. The second objective has been a multidisciplinary investigation of the relationship of climate to sedimentation rates in lakes and ponds in Yellowstone, undertaken with Drs. Wright, D.R. Engstrom and S.C. Fritz of the University of Minnesota. This facet of the research examines the relative importance of climate, fire, hillslope erosion induced by overgrazing, and nutrient enrichment in the last 150 years, as recorded in selected lakes in the northern range of Yellowstone. Populations of elk and bison are known to have fluctuated greatly during this interval, and slight climatic changes are suggested from other lines of research. In this study pollen, diatoms, charcoal, sediment chemistry, and sediment accumulation rates are analyzed in short cores from small lakes.

Geochemical and mineralogical characterization of sediments from Lake Futalaufquen (42.8°S, Andean Patagonia) to evaluate their potential as paleoclimatic proxies

2020 ◽  
Vol 98 ◽  
pp. 1-18
Author(s):  
Romina Daga ◽  
Sergio Ribeiro Guevara ◽  
Andrea Rizzo ◽  
Polona Vreča ◽  
Sonja Lojen ◽  
...  
Keyword(s):  
Atmospheric Transport ◽  
Ice Age ◽  
Long Distance ◽  
Mineralogical Characterization ◽  
Depositional History ◽  
Medieval Climatic Anomaly ◽  
Northern Patagonia ◽  
The Andes ◽  
History Of ◽  
Tephra Layers

AbstractLake sediments are key archives for paleoenvironmental investigation as they provide continuous records of the depositional history of the lake and its watershed. Lake Futalaufquen (42.8°S) is an oligotrophic waterbody located in Los Alerces National Park in the Andes of northern Patagonia, South America. A sedimentary sequence covering 1600 years was recovered to analyze the potential for paleoenvironmental reconstructions of the last millennia. Integration of different geochemical and mineralogical parameters and comparison with climatic reconstructions from other Patagonian records give clues for the identification of a warm period around AD 800–1000, associated with the Medieval Climatic Anomaly. The high frequency of tephra layers beginning in the mid-sixteenth century precludes identification of the Little Ice Age, recorded in northern Patagonia as a cold period from the fourteenth to the eighteenth century. Furthermore, the parameters analysed do not provide evidence of late-twentieth-century global warming. However, Zn deposition, a long-distance atmospheric transport process of anthropogenic origin, was identified during the last century.

scholarly journals The rise and fall of the Refugial Hypothesis of Amazonian speciation: a paleoecological perspective

2006 ◽  
Vol 6 (1) ◽  
Author(s):  
Mark B. Bush ◽  
Paulo E. de Oliveira
Keyword(s):  
Amazon Basin ◽  
Late Quaternary ◽  
Indirect Evidence ◽  
Ice Age ◽  
Data Set ◽  
The Andes ◽  
History Of ◽  
Last Ice Age ◽  
Northern Hemispheric ◽  
Amazonian Forests

The refugial hypothesis is treated as the definitive history of Amazonian forests in many texts. Surprisingly, this important theoretical framework has not been based on paleoecological data. Consequently, a model of Amazonian aridity during the northern hemispheric glaciation has been accepted uncritically. Ironically, the Refuge Hypothesis has not been tested by paleobotanical data. We present a revision of the concept of Neotropical Pleistocene Forest Refuges and test it in the light of paleocological studies derived from pollen analysis of Amazonian lake sediments deposited during the last 20,000 years. Our analysis is based primarily on paleoenvironmental data obtained from sites in Brazil and Ecuador. These data are contrasted with those that favor the hypothesis of fragmented tropical forests in a landscape dominated mainly by tropical savannas under an arid climate. The Ecuadorian data set strongly suggests a 5ºC cooling and presence of humid forests at the foot of the Andes, during the last Ice Age. The same climatic and vegetational scenario was found in the western Brazilian Amazon. On the other hand, somewhat drier conditions were observed in the central Amazon, but the landscape remained a forested landscape during the supposedly arid phases of the Late Quaternary. Data obtained from the Amazon Fan sediments containing pollen derived from extensive sections of the Amazon Basin, were fundamental to the conclusion that the predominance of savannas in this region is not supported by botanical data. Our revision of the assumptions derived from the Refuge Hypothesis indicates that it has succumbed to the test now permitted by a larger paleocological data set, which were not available during the golden age of this paradigm, when indirect evidence was considered satisfactory to support it.

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.

Mountain glaciation and paleoclimate reconstruction in the Picos de Europa (Iberian Peninsula, SW Europe)

2012 ◽  
Vol 78 (2) ◽  
pp. 303-314 ◽  
Author(s):  
Enrique Serrano ◽  
Juan José González-Trueba ◽  
María González-García
Keyword(s):  
Late Quaternary ◽  
Ice Age ◽  
Equilibrium Line Altitude ◽  
Sedimentary Characteristics ◽  
Geomorphic Mapping ◽  
Stratigraphic Analysis ◽  
History Of ◽  
Northwestern Spain ◽  
The 19Th Century ◽  
Lake Deposits

AbstractGeomorphic mapping and stratigraphic analysis of a lake core document the late Quaternary glacial history of the Central and Eastern Massifs of the Picos de Europa, northwestern Spain. The distribution of glacial deposits indicates that at their most advanced positions glaciers occupied 9.1 km2, extended as far as 7 km down-valley and had an estimated equilibrium-line altitude (ELA) ranging between 1666 and 1722 m. Radiocarbon dating of sediment deposited in a lake dammed by moraines of this advance show that the maximum glacial extent was prior to 35,280 ± 440 cal yr BP. This advance was followed by two subsequent but less extensive late Pleistocene advances, recorded by multiple moraines flanking both massifs and sedimentary characteristics in the lake deposits. The last recognized glacial episode is the 19th-century maximum extent of small Little Ice Age glaciers in the highest cirques above 2200 m.

scholarly journals The long and intertwined record of humans and the Campi Flegrei volcano (Italy)

2021 ◽  
Vol 84 (1) ◽  
Author(s):  
A. Costa ◽  
M. A. Di Vito ◽  
G. P. Ricciardi ◽  
V. C. Smith ◽  
P. Talamo
Keyword(s):  
Ground Deformation ◽  
Volcanic Eruptions ◽  
Campi Flegrei ◽  
Volcanic System ◽  
Phlegraean Fields ◽  
Volcanic Lakes ◽  
History Of ◽  
Tephra Layers ◽  
Historic Record ◽  
Key Aspects

AbstractThe Campi Flegrei volcano (or Phlegraean Fields), Campania, Italy, generated the largest eruption in Europe in at least 200 ka. Here we summarise the volcanic and human history of Campi Flegrei and discuss the interactions between humans and the environment within the “burning fields” from around 10,000 years until the 1538 CE Monte Nuovo eruption and more recent times. The region’s incredibly rich written history documents how the landscape changed both naturally and anthropogenically, with the volcanic system fuelling these considerable natural changes. Humans have exploited the beautiful landscape, accessible resources (e.g. volcanic ash for pulvis puteolana mortar) and natural thermal springs associated with the volcano for millennia, but they have also endured the downsides of living in a volcanically active region—earthquakes, significant ground deformation and landscape altering eruptions. The pre-historic record is detailed, and various archaeological sites indicate that the region was certainly occupied in the last 10,000 years. This history has been reconstructed by identifying archaeological finds in sequences that often contain ash (tephra) layers from some of the numerous volcanic eruptions from Campi Flegrei and the other volcanoes in the region that were active at the time (Vesuvius and Ischia). These tephra layers provide both a relative and absolute chronology and allow the archaeology to be placed on a relatively precise timescale. The records testify that people have inhabited the area even when Campi Flegrei was particularly active. The archaeological sequences and outcrops of pyroclastic material preserve details about the eruption dynamics, buildings from Roman times, impressive craters that now host volcanic lakes and nature reserves, all of which make this region particularly mystic and fascinating, especially when we observe how society continues to live within the active caldera system. The volcanic activity and long record of occupation and use of volcanic resources in the region make it unique and here we outline key aspects of its geoheritage.

A 7300-yr-old environmental history of seabird, human, and volcano impacts on Carlisle Island (the Islands of Four Mountains, eastern Aleutians, Alaska)

2019 ◽  
Vol 91 (03) ◽  
pp. 934-952 ◽  
Author(s):  
Evgeniya A. Kuzmicheva ◽  
Olesya I. Smyshlyaeva ◽  
Dmitry D. Vasyukov ◽  
Bulat F. Khasanov ◽  
Olga A. Krylovich ◽  
...  
Keyword(s):  
Environmental History ◽  
Volcanic Eruptions ◽  
Long Distance ◽  
Initial Stage ◽  
History Of ◽  
Tephra Layers ◽  
Strong Winds ◽  
Human Predation ◽  
The Fourier Transform ◽  
Fertilizing Effect

AbstractWe present the results of multiproxy study of a peat deposit from Carlisle Island (the Islands of Four Mountains, Aleutians). Vegetation on the initial stage of the peat is characterized by heath vegetation dominated by Ericales indicating cold conditions at 7300–6100 cal yr BP. The appearance of Betula and Alnus is the result of long-distance transportation attributable to strong winds at this time. Sedge-grass (Cyperaceae and Poaceae) communities began replacing heath vegetation at 6100 cal yr BP because of the climatic amelioration. C/N ratios and pollen spectra remain relatively stable at 6100–2450 cal yr BP. For the CR-03 peatland, volcanic tephra contributed significantly to the Fourier transform infrared spectroscopy spectral data. Volcanic input created overlap of an aluminosilicate signal with carbohydrate vibrations. Significant changes occurred at approximately 2450 cal yr BP when there is the some evidence of cooler and wetter conditions of the Neoglacial. High values of δ15N observed at 7100–7000 cal yr BP reflect the fertilizing effect of seabird nesting colonies. A decrease in δ15N ca. 6900 cal yr BP may indicate initial settlement on Carlisle Island corresponding with harvesting seabirds. Human predation continued until a series of volcanic eruptions, which deposited Okmok II and CR-02 tephra layers at ca. 2000 and 1050 cal yr BP, respectively.

A fossil pollen based reconstruction of the late Quaternary history of lodgepole pine (Pinuscontorta ssp. latifolia) in the western interior of Canada

1985 ◽  
Vol 15 (6) ◽  
pp. 1039-1044 ◽  
Author(s):  
Glen M. MacDonald ◽  
Les C. Cwynar
Keyword(s):  
Late Holocene ◽  
Lodgepole Pine ◽  
Late Quaternary ◽  
Rocky Mountain ◽  
Glacial Refugia ◽  
Range Limits ◽  
Fossil Pollen ◽  
Relict Populations ◽  
History Of ◽  
Quaternary History

Previous reconstructions of the late Quaternary biogeographical history of lodgepole pine (Pinuscontorta Dougl.) have been based upon inferences from the modern geographical distribution of morphological and genetic variation. These studies have led to the widely accepted conclusion that relict populations of the Rocky Mountain subspecies of lodgepole pine (ssp. latifolia Engelm.) persisted in glacial refugia located in northwestern Canada. New fossil pollen evidence of the late Pleistocene and Holocene distribution of lodgepole pine in the western interior of Canada contradicts this view. Pinuscontorta ssp. latifolia migrated northward into Canada from refugia located south of the continental glacial limits and did not reach its northern range limits in the southern Yukon until the late Holocene.

The California Ice-Age Refugium and the Rancholabrean Extinction Problem

1977 ◽  
Vol 8 (2) ◽  
pp. 149-153 ◽  
Author(s):  
Donald Lee Johnson
Keyword(s):  
Environmental Impact ◽  
Environmental Change ◽  
Late Quaternary ◽  
Ice Age ◽  
Glacial Refugium ◽  
Principal Agent ◽  
Extinction Event ◽  
History Of

The question of what caused the late Quaternary extinction of the Rancholabrean fauna in the California glacial refugium is examined. In the absence of significant climatic and other natural environmental change, man was probably the principal agent of extinction in California. This extinction event marked the beginning of a long history of environmental impact in the area by humans.

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