bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development and Environmental Significance of an Eolian Sand Ramp of Last-Glacial Age, Central Iran
Authors: Thomas David S.G. , Bateman Mark D. , Mehrshahi Daryoush , O'Hara Sarah L. 
Published: September 2002

AbstractA 25-m-thick section of mostly eolian sediment is exposed in the stream-cut flank of a sand ramp accumulated in a mountain saddle near Ardakan playa, central Iran. The well-sorted eolian sediments of the ramp contain talus beds and incipient paleosols. Morphology and bedding structures imply that southeasterly winds were primarily responsible for deposition of the eolian sand. Optical dating shows that the sand was deposited near the last glacial maximum within about 5000 yr. Surface stabilization, lack of surface scree, and the development of a stream cut between the mountain and the ramp show that sediment accumulation ceased after this time. The Siberian high pressure system may have been established over central Iran during the last glacial maximum, causing cooler temperatures and a prevalence of southeasterly winds. These colder, windier conditions would have led to frost shattering and eolian transport, both of which are not significant processes today but which are evident as past processes from the ramp sediments.
High-Resolution Modeling of the Advance of the Younger Dryas Ice Sheet and Its Climate in Scotland
Authors: Hubbard Alun 
Published: September 2002

Ice-sheet modeling tightly constrained by empirical studies provides an effective framework to reconstruct past climatic and environmental conditions. Scotland was severely affected by the abrupt climate change associated with the Younger Dryas Stade, during which an extensive ice sheet formed across the west highlands after a period of ice-free conditions. Here, a quasi-three-dimensional, time-dependent ice flow/mass-balance model is developed and applied to Scotland at 1 km resolution. The flow model is based on the driving stress approximation with an additional longitudinal correction term, essential at this scale of operation. Surface mass balance is driven by temperature and precipitation changes and further mass wastage is achieved through an empirically defined calving term. The ice dynamics and mass-balance components are coupled through the equation for mass continuity, which is integrated through time over a finite-difference grid which yields the geometric evolution of the ice sheet. Initial experiments reveal the model to be relatively insensitive to internal parameters but highly sensitive to mass balance. Furthermore, these experiments indicate that Scotland is readily susceptible to glaciation with large glaciers building up on the flanks of Ben Nevis after a temperature depression of 2.5°C, under present-day precipitation.The Younger Dryas is modeled using a GRIP temperature series locally adjusted for amplitude and a systematic series of runs enables the isolation of the climate which best matches mapped ice limits. This “optimum-fit” configuration requires an annual temperature cooling of 8°C and the introduction of substantial west–east and south–north precipitation gradients of 40 and 50%, respectively, to the present-day regime. Under these conditions, a series of substantial independent regional ice centers develop in agreement with trimline studies and after 550 year the modeled ice sheet closely resembles the maximum limits as indicated by field mapping. However, modeled ice continues to expand beyond 550 yr, in conflict with the mapped ice limits which suggest a prolonged period of stability. This discrepancy may be explained by the onset of extreme aridity ca. 400 yr into the Stade associated with a southern migration of the Polar Front, leading to a reduction in atmospheric circulation which effectively starved the ice sheet of its moisture source, preventing further expansion. Introduction of an additional 20% reduction in precipitation to the “optimum-fit” regime after 350 yr brings the modeled ice sheet to equilibrium, substantiating this conclusion.
The Full-Glacial Environment of the Northern Seward Peninsula, Alaska, Reconstructed from the 21,500-Year-Old Kitluk Paleosol
Authors: Höfle Claudia , Edwards Mary E. , Hopkins David M. , Mann Daniel H. , Ping Chien-Lu 
Published: September 2002

AbstractPaleoenvironmental conditions are reconstructed from soils buried under volcanic ash ca. 21,500 years ago on the Seward Peninsula. Soil development was minimal, reflecting the continuous regional deposition of loess, which originated from river floodplains and the exposed Chukchi shelf. Cryoturbated soil horizons, ice wedges, and ice-lens formation indicate a permafrost environment and mean annual temperatures below −6° to −8°C. Shallow active layers (average 45 cm), minimal evidence for chemical leaching of soils, and the presence of earthen hummocks indicate a cold and seasonally dry climate. Neither steppe nor polar desert soils are appropriate analogues for these zonal soils of loess-covered central Beringia. No exact analogues are known; however, soils underlying dry tundra near the arctic coast of northern Yakutia, Russia, and under moist, nonacidic tundra of the Alaskan North Slope have properties in common with the buried soils.
Geochemical Evidence for an Eolian Sand Dam across the North and South Platte Rivers in Nebraska
Authors: Muhs Daniel R. , Swinehart James B. , Loope David B. , Been Josh , Mahan Shannon A. , Bush Charles A. 
Published: September 2002

AbstractGeochemical and geomorphic data from dune fields in southwestern Nebraska provide new evidence that the Nebraska Sand Hills once migrated across the North and South Platte rivers and dammed the largest tributary system to the Missouri River. The Lincoln County and Imperial dune fields, which lie downwind of the South Platte River, have compositions intermediate between the Nebraska Sand Hills (quartz-rich) and northeastern Colorado dunes (K-feldspar-rich). The most likely explanation for the intermediate composition is that the Lincoln County and Imperial dunes are derived in part from the Nebraska Sand Hills and in part from the South Platte River. The only mechanism by which the Nebraska Sand Hills could have migrated this far south is by complete infilling of what were probably perennially dry North Platte and South Platte river valleys. Such a series of events would have required an extended drought, both for activation of eolian sand and decreased discharges in the Platte River system. A nearby major tributary of the North Platte River is postulated to have been blocked by eolian sand about 12,00014C yr B.P. We propose that an eolian sand dam across the Plattes was constructed at about this same time.
Skeleton of Extinct North American Sea Mink (Mustela macrodon)
Authors: Mead Jim I. , Spiess Arthur E. , Sobolik Kristin D. 
Published: September 2002

AbstractMustela macrodon(extinct sea mink) is known only from prehistoric and historic Native American shell middens dating less than 5100 years old along coastal islands of the Gulf of Maine, northeastern North America. The species is distinct from all known extant subspecies ofM. vison(American mink) but still belongs to the North American subgenusVison.Metric comparisons betweenM. macrodonand five subspecies ofM. vison,using skull, mandible, humerus, radius, femur, and tibia skeletal elements, show thatM. macrodonis larger in overall size and robustness and is proportionately larger in the dental region. Many habitat-related parallels exist between coastal island mink of the Gulf of Maine and those of the Alexander Archipelago, southeastern Alaska, where the overall largest living subspecies of mink is found (M. v. nesolestes).
Late-Quaternary Recharge Determined from Chloride in Shallow Groundwater in the Central Great Plains
Authors: Macfarlane P. Allen , Clark Jordan F. , Davisson M. Lee , Hudson G. Bryant , Whittemore Donald O. 
Published: September 2002

AbstractAn extensive suite of isotopic and geochemical tracers in groundwater has been used to provide hydrologic assessments of the hierarchy of flow systems in aquifers underlying the central Great Plains (southeastern Colorado and western Kansas) of the United States and to determine the late Pleistocene and Holocene paleotemperature and paleorecharge record. Hydrogeologic and geochemical tracer data permit classification of the samples into late Holocene, late Pleistocene–early Holocene, and much older Pleistocene groups. Paleorecharge rates calculated from the Cl concentration in the samples show that recharge rates were at least twice the late Holocene rate during late Pleistocene–early Holocene time, which is consistent with their relative depletion in16O andD.Noble gas (Ne, Ar, Kr, Xe) temperature calculations confirm that these older samples represent a recharge environment approximately 5°C cooler than late Holocene values. These results are consistent with the global climate models that show a trend toward a warmer, more arid climate during the Holocene.
Hydrologic Variation in the Northern Great Plains During the Last Two Millennia
Authors: Fritz Sherilyn C. , Ito Emi , Yu Zicheng , Laird Kathleen R. , Engstrom Daniel R. 
Published: September 2002

AbstractReconstructions of lake-water salinity at decadal resolution for the last 2000 yr are compared among three lakes in North Dakota to infer regional patterns of drought. The intersite comparisons are used to distinguish local variation in climate or hydrology from regional patterns of change. At one lake, diatom-inferred salinity and lake-water Mg/Ca inferred from ostracode shell chemistry are coherent, both in terms of direction and magnitude of change, indicating that each is a robust technique for reconstructing lake-water chemistry. The data show that the last 2000 yr have been characterized by frequent shifts between high and low salinity, suggesting shifts between dry and moist periods. Long intervals of high salinity suggest periods of multiple decades when droughts were intense and frequent, thus indicating times when drought was more persistent than in the 20th century. Both the Medieval Period and Little Ice Age were hydrologically complex, and there is no clear evidence to suggest that either interval was coherent or unusual in effective moisture relative to long-term patterns. Differences among the three sites may be attributed to variation in local hydrology, and these differences emphasize the need for multiple sites in deriving regional climate interpretations from paleoecological data.
Vegetation, Climate, and Sea Level in the Past 55,000 Years, Hanjiang Delta, Southeastern China
Authors: Zheng Zhuo , Li Qianyu 
Published: September 2002

AbstractPollen in Quaternary deposits from the subtropical Hanjiang Delta records three major phases in the local vegetation and climate history during the last 55,000 yr: (1) a prevalent cool-to-temperate and humid climate at ca. 24,000 14C yr B.P. is indicated by abundant pollen of temperate trees including conifers; (2) between 20,000 and 15,000 14C yr B.P., a cold, dry environment was associated with low sea level during the last glaciation, leading to subaerial exposure, weathering, and interruption of sedimentation, as well as departure from the region of Dacrydium and Sonneratia; (3) a short-term expansion of grassland at ca. 10,300 14C yr B.P. reduced the predominant Lauraceae-Fagaceae evergreen forest, possibly corresponding to the Younger Dryas cooling. The combined data indicate a maximum sea-level rise in the mid-Holocene (7500–4000 14C yr B.P.) and a marine influence in the late Pleistocene at 45,000–20,000 14C yr B.P. The Holocene warming, however, did not bring back moisture-sensitive taxa, indicating high seasonal aridity probably caused by renewed monsoon conditions.
Tree-Ring Dating of Extreme Lake Levels at the Subarctic–Boreal Interface
Authors: Bégin Yves 
Published: September 2002

AbstractThe dates of extreme water levels of two large lakes in northern Quebec have been recorded over the last century by ice scars on shoreline trees and sequences of reaction wood in shore trees tilted by wave erosion. Ice-scar chronologies indicate high water levels in spring, whereas tree-tilting by waves is caused by summer high waters. A major increase in both the amplitude and frequency of ice floods occurred in the 1930s. No such change was indicated by the tree-tilting chronologies, but wave erosion occurred in exceptionally rainy years. According to the modern record, spring lake-level rise is due to increased snowfalls since the 1930s. However, the absence of erosional marks in a large number of years since 1930 suggests a high frequency of low-water-level years resulting from dry conditions. Intercalary years with very large numbers of marked trees (e.g., 1935) indicate that the interannual range of summer lake levels has increased since the 1930s. Increased lake-flood frequency is postulated to be related to a slower expansion of arctic anticyclones, favoring the passage of cyclonic air masses over the area and resulting in abundant snowfall in early winter. Conditions in summer are due to the rate of weakening of the anticyclones controlling the position of the arctic front in summer. This position influences the path of the cyclonic air masses, which control summer precipitation and consequently, summer lake levels in the area.
Far-Field Test of the ICE-4G Model of Global Isostatic Response to Deglaciation Using Empirical and Theoretical Holocene Sea-Level Reconstructions for the Fiji Islands, Southwestern Pacific
Authors: Nunn Patrick D. , Peltier W. Richard 
Published: September 2002

AbstractHolocene paleosea-level data for Fiji, represented by 77 dates and emergence magnitudes, are presented, screened, and adjusted. Most data are from coral microatolls, potentially the most precise paleosea-level indicators in this region. Holocene sea-level changes are reconstructed for five areas within Fiji known to have had different late Quaternary tectonic histories. Resulting analysis suggests that postglacial sea level in Fiji reached its present level more than 6900 14C yr B.P. It also suggests either that a single maximum 5650–3200 14C yr B.P. (perhaps +2.19 m but more likely +1.35–1.50 m) occurred or that two maxima occurred 6100–4550 14C yr B.P. (+0.75–1.85 m) and 3590–2800 14C yr B.P. (+0.90–2.46 m). Broad agreement exists between these empirical sea-level reconstructions and those derived theoretically using the ICE-4G model (predicted maximum ∼4000 14C yr B.P.; ∼+2.1 m). This suggests that both methods of reconstructing Holocene sea-level changes are valid, as are the assumptions underpinning the ICE-4G model. The most important of these, that eustatic sea level had effectively stopped rising by late middle-Holocene time (5000–4000 yr B.P.), is confirmed by observations from Fiji.
Implications for Late Pleistocene Mastodon Diet from Opal Phytoliths in Tooth Calculus
Authors: Gobetz Katrina E. , Bozarth Steven R. 
Published: September 2002

AbstractCalculus removed from the molar teeth of four American mastodons (Mammut americanum) contained opal phytoliths which reflect major dietary components. Three samples contained abundant grass phytoliths (ca. 86% of total), with long cells and trapezoidal pooid short cells dominant (ca. 25 and 31%, respectively). Dicot phytoliths from hackberry (Celtissp.) seeds and indeterminate deciduous trees were rare (1–3%), though well preserved, whereas phytoliths from conifer trees were not recognizable in any of the samples. Comparative analysis of calculus from modern and fossil browsers and mixed feeders implies that dicots and conifers are nearly invisible in the phytolith record. This scarcity may result from poor preservation, low silica production in woody taxa, and/or animals' selection of young, silica-poor leaves and shoots. However, abundant grass phytoliths in the mixed feeders suggest that presence versus absence of grass phytoliths may distinguish mixed feeders and grazers from browsers. Mastodons are traditionally considered browsers, but grass phytolith assemblages in three individual mastodons contained similarly high concentrations of pooids, suggesting that these grasses were a significant part of the diet. Abundant pooid phytoliths, in addition to diatoms, indicate that these mastodons grazed in a cool, moist late Pleistocene environment, possibly near water.
Ecosystem Impact of the Campanian Ignimbrite Eruption in Late Pleistocene Europe
Authors: Fedele Francesco G. , Giaccio Biagio , Isaia Roberto , Orsi Giovanni 
Published: September 2002

AbstractThe dating of the Campanian Ignimbrite (CI) eruption to ∼37,000 cal yr B.P. draws attention to the coincidence of this volcanic catastrophe and the suite of coeval, Late Pleistocene biocultural changes that occurred within and outside the Mediterranean region. These included the Middle to Upper Paleolithic cultural transition and the supposed change from Neanderthal to “modern” Homo sapiens anatomy, a subject of sustained debate. No less than 150 km3 of magma were extruded in the CI eruption, the signal of which can be detected in Greenland ice cores. As widespread discontinuities in archaeological sequences are observed at or following the CI event, a significant interference with ongoing human processes in Mediterranean Europe is hypothesized.
Changes in the Thermal Climate in Northwestern Europe during Marine Oxygen Isotope Stage 3, Estimated from Fossil Insect assemblages
Authors: Coope G. Russell 
Published: September 2002

AbstractMore than 30 fossil coleopteran (beetle) assemblages have been recorded from oxygen isotope stage 3 in northern Europe, comprising several hundred identified species. Using the mutual climatic range method for quantifying palaeotemperatures, these assemblages show that the climates of the times can be divided into two distinct interstadial types. One, a short phase of temperate/oceanic climate occurred between 43,000 and 42,000 14C yr B.P. when conditions were not much different from those of the present day. In spite of the temperate climate, trees did not colonize northwestern Europe at this time. Two, both before and after this temperate interlude there were phases of cold/continental climate during which summers were too cold for trees to grow and winters were of Siberian intensity. It is possible that periods of even colder conditions intervened from time to time between the interstadial but, because of the intensity of the cold, biological systems were so inhibited that no fossil evidence for them can be found in northern Europe. Evidence for them must be sought in the fossil records from the warmer parts of southern Europe or in the physical evidence in the Greenland ice cores.
Distinct roles of GPVI and integrin α2β1 in platelet shape change and aggregation induced by different collagens
Authors: Jarvis Gavin E , Atkinson Ben T , Snell Daniel C , Watson Steve P 
Published: September 2002

Various platelet membrane glycoproteins have been proposed as receptors for collagen, in some cases as receptors for specific collagen types. In this study we have compared the ability of a range of collagen types to activate platelets.
Bovine collagen types I–V, native equine tendon collagen fibrils and collagen‐related peptide (CRP) all induced platelet aggregation and shape change.
Responses were abolished in FcRγ chain‐deficient platelets, which also lack GPVI, indicating a critical dependence on the GPVI/FcRγ chain complex.
Responses to all collagens were unaffected in CD36‐deficient platelets.
A monoclonal antibody (6F1) which binds to the α2 integrin subunit of human platelets had a minimal effect on the rate and extent of aggregation induced by the collagens; however, it delayed the onset of aggregation following addition of all collagens. For shape change, 6F1 abolished the response induced by collagen types I and IV, substantially attenuated that to collagen types II, III and V, but only partially inhibited Horm collagen.
Simultaneous blockade of the P2Y1 and P2Y12 receptors, and inhibition of cyclo‐oxygenase demonstrated that CRP can activate platelets independently of ADP and TxA2; however, responses to the collagens were dependent on these mediators.
This study confirms the importance of the GPVI/FcRγ chain complex in platelet responses induced by a range of collagen agonists, while providing no evidence for collagen type‐specific receptors. It also provides evidence for a modulatory role of α2β1, the significance of which depends on the collagen preparation.

British Journal of Pharmacology (2002) 137, 107–117. doi:10.1038/sj.bjp.0704834
Endothelial nitric oxide modulates perivascular sensory neurotransmission in the rat isolated mesenteric arterial bed
Authors: Ralevic Vera 
Published: September 2002

A possible role of nitric oxide (NO) as a modulator of capsaicin‐sensitive sensory neurotransmission in blood vessels was investigated in the rat isolated mesenteric arterial bed.
Electrical field stimulation (EFS) of methoxamine‐preconstricted mesenteric beds elicited frequency‐dependent vasorelaxation mediated by capsaicin‐sensitive sensory nerves. NG‐nitro‐L‐arginine methyl ester (L‐NAME, 10 and 300 μM) and 7‐nitroindazole (7‐NI, 100 μM), inhibitors of nitric oxide synthase (NOS), augmented sensory neurogenic vasorelaxation. D‐NAME (300 μM), 6‐aminoindazole (100 μM) and Nω‐propyl‐L‐arginine (50 nM), a selective inhibitor of neuronal NOS, were without effect. The effect of 10 μM L‐NAME was reversed by L‐arginine (1 mM), the substrate for NOS.
L‐NAME (300 μM) and 7‐NI (100 μM) had no significant effect on vasorelaxations to calcitonin gene‐related peptide (CGRP), the principal motor neurotransmitter of capsaicin‐sensitive sensory nerves in rat mesenteric arteries, or to capsaicin, indicating a prejunctional action. The inhibitors of NOS had no effect on vasorelaxation to forskolin, but augmented vasorelaxation to sodium nitroprusside (SNP).
Removal of the endothelium augmented sensory neurogenic vasorelaxation, but did not affect vasorelaxation to CGRP, indicating a prejunctional action of endothelial NO.
In the absence of endothelium, L‐NAME (300 μM) inhibited, and 7‐NI (100 μM) caused no further augmentation of sensory neurotransmission.
SNP (100 nM), a nitric oxide donor, attenuated sensory neurogenic relaxations to EFS.
In rat isolated thoracic aortic rings, L‐NAME (100 μM) and 7‐NI (100 μM) attenuated concentration‐dependent relaxations to acetylcholine.
These data show that NO modulates sensory neurotransmission evoked by EFS of the rat isolated mesenteric arterial bed, and that when NO synthesis is blocked sensory neurogenic relaxation is augmented. The source of NO is the vascular endothelium.

British Journal of Pharmacology (2002) 137, 19–28. doi:10.1038/sj.bjp.0704837