bluuebunny/crossref_metadata_2025_split huggingface dataset:
Causes of Antarctic Glaciation in the Cenozoic
Authors: Kvasov D.D. , Verbitsky M.Ya. 
Published: July 2006

AbstractThe causes of Antarctic glaciation are analyzed by means of numeral experiments based on the three-dimensional thermodynamic model of a large ice sheet. Refrigeration of the climate between the Eocene and the Oligocene was due to the opening of the passage south of Australia and to the formation of the South Ring Stream. Calculations have shown that this led to the development of the East Antarctic Ice Sheet which might have existed in spite of relatively high temperatures of the surrounding ocean air. A new cooling of the climate in the Middle Miocene is connected with the fact that the South Ring Stream found its way through the Drake Passage glaciers spreading on to the Western Antarctic. Between Miocene and Pliocene, glaciation of the South Polar regions was at its maximum due to the regression of the world ocean. In Quaternary time, sea level was lowering due to the glaciation of the Northern Hemisphere, which resulted in glacier growth in the Antarctic. The anticipated warming of the climate due to the activity of man is not likely to bring about any considerable change in the size of the East Antarctic Ice Sheet.
Marine Plio-Pleistocene of Iceland and problems of Its Correlation
Authors: Gladenkov Y.B. 
Published: July 2006

AbstractThe marine Pliocene-Pleistocene sequence of Iceland contains four main assemblages of mollusks: (1)Venerupis rhomboides et al., (2)Serripes groenlandicus et al., (3)Portlandia arctica et al., and (4) recent species. Analysis of the stratigraphic distribution of 100 species shows that the percentage of extinct species in the assemblages decreases from 40% in the oldest to 4–8% in the youngest. There is also a change from south boreal affinities in the oldest assemblage to north boreal in the youngest. The molluskan assemblages of Iceland can be correlated with Pliocene-Pleistocene assemblages of England and North Europe: (1) Coralline Crag, (2) Red Crag—lower part of the Icenian strata, (3) upper part of the Icenian-Cromerian strata. The upper boundaries of the Pliocene and Eopleistocene are defined by paleomagnetic data and radiological dating. The upper boundary of the Pliocene presumably should be established in the basalts lying between the Tjörnes and the Breidavik deposits by changes between the second and third mollusk assemblages and by the Gilsa paleomagnetic event.
Energy-Dispersive X-ray Fluorescence Analysis as a Rapid Method for Identifying Tephras
Authors: Cormie A. B. , Nelson D. E. 
Published: July 2006

AbstractThe use of energy-dispersive X-ray fluorescence analysis (XES) for the routine identification of three tephras (Mazama, Bridge River, Mount St. Helens Yn) commonly found in archeological sites in British Columbia has been investigated. Researchers have often assumed that chemical analysis of bulk samples of glass separates would be hampered by contamination and weathering effects. Our results indicate that XES of bulk glass separates provides a very reliable method for rapidly identifying the three tephras in question, even with a very simple sample preparation. This should enable persons not skilled in geology or in tephrochronology to collect and to identify samples of these tephras. Finally, as a part of the study, similar measurements were made on the separated glass portions of these three tephras and of three others (Glacier Peak B and G, White River) from northwest North America. The results suggest that this method may provide tephrochronologists with a useful additional tool for studying tephras in other regions.
Full-Glacial Southwestern United States: Mild and Wet or Cold and Dry?
Authors: Galloway R. W. 
Published: July 2006

AbstractThis paper considers a model of cold and dry full-glacial climates for the southwestern United States in the light of published studies. The evidence from fossil plants is shown to be reconcilable with temperatures some 10°C below their present levels and a concomitant shift of the upper timberline which varied according to regional summer lapse rates. Fossils of “thermophilous” or “mesophytic” plants are cited by some writers as evidence for mild, pluvial conditions although today these plants occur in relatively cold and dry situations. Mean annual and July temperatures for the United States as a whole, derived from the model, are in accord with periglacial and palynological evidence.
Human Response to Environmental Change in the Perspective of Future, Global Climate
Authors: Butzer Karl W. 
Published: July 2006

AbstractHuman response to severe environmental stress is conceived and implemented by individuals, but must be approved by the group. These decisions are made with respect to perceived circumstances. Societies are enmeshed within adaptive systems that provide a matrix of opportunities and constraints for a wide range of potential behavioral variability. Such systems repeatedly readjust to short-term crises, e.g., droughts, but persistent and severe environmental stress may require substantial revision of adaptive strategies. The Sahel drought of 1968–1973 is an example of a brief but severe crisis, recurring along the Saharan margins perhaps once every 30 years. Closer inspection shows links between intensified intertribal warfare and ecological stress in the lower Omo Valley. The decline of the Egyptian New Kingdom during the 12th century B.C., in response to economic stagnation, sociopolitical instability, dynastic weakness, foreign pressures, and poor Nile floods over 50–70 years, represents a more complex and fundamental modification, with systemic simplification lasting 450 years. Such insights can be applied to future, global climatic change due to increasing atmospheric CO2. Simulation and paleoclimatic experience suggest a drier climate for the North American and Soviet breadbaskets, to threaten world food supplies at a time of maximum demographic pressures and declining resources. Public perception and remedial planning should receive the attention of Quaternary scientists, in order to preempt an involuntary, global, systemic simplification.
Evidence for a Postglacial Low Relative Sea-Level Stand in the Drowned Delta of the Merrimack River, Western Gulf of Maine
Authors: Oldale R. N. , Wommack L. E. , Whitney A. B. 
Published: July 2006

AbstractA submerged delta of the Merrimack River, located offshore between Cape Ann, Massachusetts, and the New Hampshire border, indicates a postglacial low relative see-level stand of about −47 m. The low stand is inferred to date to 10,500 yr B.P., but a lack of age control makes this assignment uncertain. A curve based on a late Wisconsinan, high relative sea-level stand of +32m at 13,000 yr B.P., a low stand of −47m at 10,500 yr B.P., and younger radiocarbon dates related to sea-level rise indicates an early postglacial crustal rise of at least 5 m per century.
Holocene Vegetation History of the Prince William Sound Region, South-Central Alaska
Authors: Heusser Calvin J. 
Published: July 2006

AbstractVegetation history during the Holocene is interpreted from the pollen and sedimentary records of nine sections of peat deposits located in sedge tundra at sites in the northern and northwestern parts of the Prince William Sound region. Basal radiocarbon ages of the deposits are between 10,015 and 580 yr B.P. Modern surface pollen data from these and 25 additional sites, ranging from lowlands to an altitude of 675 m in the alpine tundra, were used to aid in the interpretation of the fossil records. Both frequency and influx pollen diagrams of the oldest section disclose a sequence of communities beginning with sedge tundra, containing thickets of willow and alder, followed by alder, which became predominant at about 8300 yr B.P. Later, alder declined, and an inferred growth of sedge tundra and the establishment of colonies of mountain hemlock and Sitka spruce with some western hemlock occurred about 2680 yr B.P. Finally, regrowth of sedge tundra accompanied by the development of forest communites took place over the past 2000 yr. The influence of glacier advances on the vegetation in the fjords occurred during Neoglacial episodes dated at 3200–2500 yr B.P. and during recent centuries. Regional Holocene tectonic activity was also an influential factor, especially at the time of the 1964 earthquake.
Geochronology and Settlement Disposition in the Early Palaeo-Indian Occupation of Southern Ontario, Canada
Authors: Jackson L. J. 
Published: July 2006

AbstractExamination of a sample of 150 fluted-point localities from southern Ontario, Canada in relation to datable features of Late Wisconsinan ice retreat discloses maximum possible ages for early Palaeo-Indian occupation and reveals selection of specific physiographic situations. General relationship to maximum ice-advance positions suggests occupation during the Two Creeks Interstade after Port Huron ice retreat about 12,300 yr B.P. Specific relationship to 14C-dated proglacial Great Lake strands favors occupation during the North Bay Interstade after Greatlakean ice retreat about 11,500 yr B.P. Locality frequency on Lake Algonquin strands suggests contemporaneity with the main stage of this lake about 11,500 to 10,400 yr B.P., with a small number of lake-plain localities indicating minor post-Algonquin persistence. Radiocarbon dates for fluted-point sites elsewhere in the glaciated northeast place occupation coeval with the southwestern Folsom fluted-point tradition of about 10,850 to 10,200 yr B.P. Locality situation in regions dominated by proglacial sediments, on lake-edge features adjacent to strand-dissecting tributaries, within major river valleys, implies selectivity reflecting primary adaptation. Fluted-point associations with caribou and elk remains suggest that “focal” adaptation to cervids, comparable to southwestern Folsom bison exploitation, might underlie the homogeneous nature and distribution of early Palaeo-Indian localities throughout the northeast.
Paleoentomology and Paleoecology of a Possible Sangamonian Site Near Innerkip, Ontario
Authors: Pilny Jerry J. , Morgan Alan V. 
Published: July 2006

AbstractA stream section near Innerkip, Ontario, exposes several meters of organic silts and peaty detritus beneath two late Wisconsinan tills. Radiocarbon dates provide a minimal middle Wisconsinan age of >50,000 yr B.P. A 250-kg bulk sample from the peat stratum was processed for vertebrates, plant macrofossils, and insects. Vertebrate remains include teeth from deer, muskrat, and vole as well as plates from a turtle shell. At least 6000 insect fragments from a minimum of 19 Coleoptera families were identified. The most common groups are hydrophilids and dytiscids (water beetles), curculionids (weevils), staphylinids (rove beetles), and carabids (ground beetles). The majority of identified beetles are associated with fresh water as aquatic predators, scavengers, or grazers, while others prefer hygric substrates and moist plant litter. The large number of plant-dependent beetles, the numerous floating and emergent aquatic plant seeds, and the presence of the associated vertebrates point toward a locally rich and varied flora and fauna, probably deposited in a well-vegetated pond. The modern distributions and ecologies of the identified fossil insects suggest temperatures similar to those found in southern Ontario today. On these grounds the Innerkip peat represents either a very warm interstadial or a possible interglacial deposit. If the latter is true this is the second presumed Sangamon-aged site known in southern Ontario.
Early Holocene Basinal Sediments of the Dakhleh Oasis Region, South Central Egypt
Authors: Brookes Ian A. 
Published: July 2006

AbstractTwenty samples of artifactual ostrich eggshell and hearth charcoal, firmly to loosely associated with basinal lacustrine, playa, and sand sheet sediments in the Dakhleh Oasis region of south-central Egypt, yield radiocarbon ages between ca. 8800 and ca. 4700 yr B.P. The sediments record variable sedimentary responses to an early Holocene pluvial interval in this virtually rainless region. Differences of hydrogeology and morphometry among and within basin types complicate paleoclimatic interpretation.
Humid to Arid to Subhumid Vegetation Shift on Pilliga Sandstone, Ulungra Springs, New South Wales
Authors: Dodson J.R. , Wright R.V.S. 
Published: July 2006

AbstractThe Pilliga Sandstone region of the northwest slope of New South Wales has a natural vegetation cover of sclerophyllous relatively closed to open forests with a largely heathy understorey, and a warm, subhumid and continental climate. Pollen analysis of spring-fed deposits gives a vegetation history extending from at least 30,000 yr B.P. to the late Holocene. Tree pollen became scarce after about 25,000 yr B.P. and an assemblage dominated by Chenopodiaceae, Liguliflorae, Tubuliflorae, and probably Poaceae developed. No similar assemblage is known from present pollen rain studies carried out in Australia. However, it clearly represents a treeless open shrub-steppe formation and therefore an arid or semiarid environment. The site thus provides evidence of an eastward late Pleistocene extension of the arid zone in Australia, and is the first full-glacial vegetation record between 20° and 35° latitude in Australia. The present vegetation cover did not become reestablished until the beginning of the Holocene, which raises questions about the form in which Pilliga Sandstone vegetation survived full-glacial conditions.
Holocene Vegetation Change at Treeline North of Yellowknife, Northwest Territories, Canada
Authors: Moser K. A. , MacDonald G. M. 
Published: July 2006

AbstractTwo radiocarbon-dated cores from small lakes located approximately 25 km north of the mapped boundary between forest-tundra and tundra provide records of postglacial vegetation change at the treeline near Yellowknife, NWT, Canada. Basal radiocarbon dates of 6180 and 7470 yr B.P. were obtained from the cores. The fossil pollen evidence suggests that the initial vegetation wasBetulatundra with a peatland component.Alnusbecame an important constituent of the pollen assemblages between 6900 and 5500 yr B.P. Both lakes record sharp increases inPiceacf.marianapollen at approximately 5000 yr B.P., suggesting the establishment of forest-tundra. By 3500 yr B.P.Picea marianaforest-tundra had withdrawn. The proportion of organic to inorganic sediment in the cores was at a maximum between 5000 and 3500 yr B.P. Tundra has dominated the region since 3500 yr B.P. In northwestern Canada, the maximum northward advance of treeline occurred between 9000 and 5000 yr B.P. The asynchrony in treeline advance in central and northwestern Canada may reflect that glacial ice persisted in the interior NWT longer than previously believed. Alternatively, the asynchronous history of the treeline may be a result of the geometric properties of the long-wave westerly disturbance that is manifest in the median summer position of the arctic front and ultimately controls the geographic location of the treeline.
Fossil Insect Evidence for Late Quaternary Climatic Change in the Big Bend Region, Chihuahuan Desert, Texas
Authors: Elias Scott A. , Van Devender Thomas R. 
Published: July 2006

AbstractA series of 50 packrat midden assemblages from the Big Bend region of the Chihuahuan Desert, ranging in age from >36,000 yr B.P. to recent, yielded abundant, diverse arthropod faunas. The mesic nature of regional Wisconsin age climates is substantiated by the fauna from 30,000–12,000 yr B.P., especially during the middle Wisconsin (30,000–20,000 yr B.P.). Late Wisconsin faunas contained grassland species which are confined today to cooler, moister regions. Following 12,000 yr B.P., most of these temperate species were replaced either by desert species or by more cosmopolitan taxa, marking the climatic shift from late Wisconsin to postglacial time. Insects indicative of more severe aridity are first recorded at about 6000 yr B.P., but some temperate species persisted until about 2500 yr B.P. After this, only desert dwellers are recorded.
Time of Maximum Late Wisconsin Glaciation, West Coast of Canada
Authors: Blaise Bertrand , Clague John J. , Mathewes Rolf W. 
Published: July 2006

AbstractNew data from a deep-sea core in the eastern North Pacific Ocean indicate that the western margin of the Late Wisconsin Cordilleran Ice Sheet began to retreat from its maximum position after 15,600 yr B.P. Ice-rafted detritus is present in the core below the 15,600 yr B.P. level and was deposited while lobes of the Cordilleran Ice Sheet advanced across the continental shelf in Queen Charlotte Sound, Hecate Strait, and Dixon Entrance. The core data are complemented by stratigraphic evidence and radiocarbon ages from Quaternary exposures bordering Hecate Strait and Dixon Entrance. These indicate that piedmont lobes reached the east and north shores of Graham Island (part of the Queen Charlotte Islands) between about 23,000 and 21,000 yr B.P. Sometime thereafter, but before 15,000–16,000 yr B.P., these glaciers achieved their greatest Late Wisconsin extent. Radiocarbon ages of late-glacial and postglacial sediments from Queen Charlotte Sound, Hecate Strait, and adjacent land areas show that deglaciation began in these areas before 15,000 yr B.P. and that the shelf was completely free of ice by 13,000 yr B.P.
The Hayes Tephra Deposits, and Upper Holocene Marker Horizon in South-Central Alaska
Authors: Riehle James R. , Bowers Peter M. , Ager Thomas A. 
Published: July 2006

AbstractThe most widespread of all Holocene tephra deposits in the Cook Inlet region of south-central Alaska is a set of deposits from Hayes volcano. Because of their unique phenocryst content—biotite in rare amounts and a high proportion of amphibole to pyroxene—the deposits are readily identifiable at all but the most distant sites where they are very fine grained. Eighteen radiocarbon dates from eight upland sites limit the age of the tephra set to between about 3500 and 3800 yr. The set originated at Hayes volcano in the Tordrillo Mountains 150 km northwest of Anchorage; seven or possibly eight closely succeeding deposits, low-silica dacite in composition, compose two main lobes that extend northeast for 400 km and south for at least 250 km from the vent. We estimate the total tephra volume to be 10 km3; multiple layers imply four to six larger and two or three smaller eruptions. The deposits are a nearly isochronous marker horizon that should be useful in future archeologic, geologic, and palynologic studies in the region.
Dynamic Pedogenesis: New Views on Some Key Soil Concepts, and a Model for Interpreting Quaternary Soils
Authors: Johnson D. L. , Keller E. A. , Rockwell T. K. 
Published: July 2006

AbstractInasmuch as soils are open systems and rarely, if ever, achieve equilibrium with their environments, it is philosophically sound to view all soils as expressing varying levels of polygenesis as that term has been redefined. Soil genesis and resultant morphology may then be viewed in a comprehensive framework of soil evolution that consists of two linked pathways, one developmental and the other regressive, that reflect interactions of both exogenous and endogenous vectors (vectors are factors, processes, and conditions of pedogenesis). Following this philosophy, a model of pedogenesis is framed in an evolutional paradigm that emphasizes the integrated effects of dynamic and passive pedogenic vectors in directing pathways and in controlling rates of soil genesis through time. The dynamic vectors include energy and mass fluxes, frequencies of soil wetting and drying, water table dynamics, organisms, feedback processes, and pedoturbation. The passive vectors include parent materials, soil chemical environment, stability of geomorphic surfaces, and various evolved soil properties and conditions (accessions). Both sets of vectors vary spatially, and the dynamic vectors, more so than passive vectors, fluctuate through time. The model is expressed as S=f(D,P,dD/dt,dD/dt) where S is the state of the soil or degree of profile evolution, D is the set of dynamic vectors, P is the set of passive vectors, and dD/dt and dP/dt denote change through time t. The model helps explain the apparent minimal development and regressed character of some old soils and the rapid and strong development of some young ones.
Plant and Insect Remains from the Wisconsinan Interstadial/Stadial Transition at Wedron, North-Central Illinois
Authors: Garry Clarke E. , Schwert Donald P. , Baker Richard G. , Kemmis Tim J. , Horton Diana G. , Sullivan Amy E. 
Published: July 2006

AbstractOrganic material exposed within a small swale fill in Pit 6 of the Wedron Silica Sand Co. near Wedron in LaSalle County, Illinois, includes well-preserved pollen, plant macrofossils, and insect remains. This material occurs in slackwater sediment in the lower part of the Peddicord Formation, which was deposited as existing valleys were dammed by fluvial aggradation during the initial late Wisconsinan advance of Laurentide ice into the Wedron area. Wood from the organic horizon has a radiocarbon age of 21,460 ± 470 yr B.P. (ISGS-1486). The pollen spectrum is dominated byPicea, Pinus, and Cyperaceae. Plant macrofossils comprise a mix of boreal-forest taxa, includingPicea, Larix laricina, and the mossCampylium stellatum; subarctic species includingBetula glandulosa, Empetrum nigrum, andSelaginella selaginoides; along with the predominantly arcticVaccinium uliginosumvar.alpinum, Dryas integrifolia, andRhododendron lapponicum. The insect fauna contains the western montane ground beetleOpisthius richardsoni; several arctic-subarctic ground beetles includingDiacheila polita, Helophorus sibiricus, andPterostichus (Cryobius) caribou; and a diverse assemblage of insects that today inhabit the boreal forest. We interpret the biotic record to record a phase in the transition from closed boreal forest to open tundra as climatic conditions deteriorated in advance of continental glaciation.
Late Holocene tephrochronology of the northern Antarctic Peninsula
Authors: Björck Svante , Sandgren Per , Zale Rolf 
Published: July 2006

AbstractAndesitic and basaltic andesitic tephra layers are abundant in Holocene deposits from the Antarctic Peninsula. Visually discernible tephra horizons occur in three lakes on Livingston Island. Tephra in two other lakes and in a moss bank on Elephant Island, with very low ash concentrations, were detected magnetically. Deception Island is the most likely volcanic source for the tephra. With direct14C dating, age/depth curves, and cross-correlations at least 14 tephra horizons dating to between ca. 4700 and 250 yr B.P. were identified and now form the basis for a preliminary regional tephrochronology that will be a valuable dating tool for investigating the Holocene climatic history of Antarctica.
Late Pleistocene chronology of loess deposition near Luochuan, China
Authors: Forman Steven L. 
Published: July 2006

AbstractLoess near Luochuan was sampled for thermoluminescence (TL) dating simultaneously with magnetic susceptibility measurements to provide the first independent age estimates on a susceptibility record from the Loess Plateau of China. TL age estimates on late Pleistocene loess (L1) are stratigraphically consistent with no statistical difference in TL ages by the total or partial bleach techniques or by measuring ultraviolet or green wavelengths in the TL analysis. Loess below the last interglacial soil (S1) yielded disparate results and is in many localities in central and eastern China unsuitable for TL dating because of complications of TL saturation and uncertainties in estimating the environmental radiation. TL age estimates on the L1 loess are consistent with previously reported TL ages for sites near Beijing and Xian as well as in general agreement with age models for loess deposition based on paleomagnetics and magnetic susceptibility. The convergence of a variety of geochronologic indices indicate that the last major period of loess deposition in central China began 70,000 ± 10,000 yr B.P. and terminated <20,000 yr B.P. This event is probably recorded in sediments from the adjacent Pacific Ocean and possibly in dust records from the Antarctic Ice Sheet.