bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new Erioderma taxon from the Azores
Authors: Jørgensen Per M. , James Peter W. 
Published: September 2002

AbstractThe Azorean lichen previously and erroneously referred in the literature to Erioderma wnghtii, belongs to the complex, widespread species E. leylandii, and is escribed as subsp. azoricum, possibly representing a relic, ancestral form with a composite chemistry. It is presently only known from Pico where it is under threat owing to the destruction of the forests.
Geoarchaeology and Geochronology of the Miami (Clovis) Site, Southern High Plains of Texas
Authors: Holliday Vance T. , Haynes C. Vance , Hofman Jack L. , Meltzer David J. 
Published: September 2002

AbstractThe Miami site, excavated in 1937, is in a small "playa" basin on the High Plains surface. The site is one of the earliest documented co-occurrences of Clovis points and mammoth. Reinvestigation of the site and related collections was undertaken to better understand the stratigraphy, geochronology, and archaeology. The basin, 23 m diameter × 1.6 m deep, filled with (1) dark gray silty clay, and (2) near the top of the section, a lens of well-sorted silt or loess. The basin started to fill ca. 13,700 yr B.P., the loess dates to ca. 11,400 yr B.P., and the bone bed probably dates to ca. 11,400-10,500 yr B.P. The loess may be the local manifestation of a "Clovis drought." The partial remains of five mammoths (three adults and two juveniles) were recovered in 1937; no other animal remains are known. The bone is heavily weathered and there are no clear indications of human modification. Artifacts found at the site include three Clovis points and a scraper found among the bones and two flakes and a scraper found on the surface near the playa. The origins of the bone and stone assemblage are uncertain but four scenarios are offered: a successful mammoth kill, an unsuccessful kill with wounded animals dying at the watering hole, opportunistic scavenging following natural deaths, or a palimpsest of multiple deaths following both natural and human causes.
Loess of the Upper Mississippi Valley Driftless Area
Authors: Leigh David S. , Knox James C. 
Published: September 2002

AbstractLoess of the Driftless Area includes four distinct late Quaternary lithostratigraphic units: the Wyalusing (new), Loveland, Roxana, and Peoria formations. Erosion has removed parts or all of the pre-late Wisconsian loess at many sites. These formations consist largely of loess and retransported loess that typically occurs on uplands, terraces, and valley margins in the region. The oldest widespread formation (probably > 125,000 yr B.P.) is here formally named the Wyalusing Formation. The three younger formations correlate with the Loveland (probably > 125,000 yr B.P.), Roxana (55,000-25,000 yr B.P.), and Peoria (25,000-12,000 yr B.P.) loesses recognized elsewhere in the midcontinental United States. The soil/stratigraphic morphology of the Wyalusing-Loveland and Roxana-Peoria couplets appears to represent two distinct loess sedimentation sequences related to major expansion and contraction of the Laurentide Ice Sheet during oxygen isotope stages 6 and 3-2, respectively. The occurrence-frequency of loess units is inversely related to age, illustrating the erosional nature of the Driftless area landscape. The occurrence of four loess units at some sites in Driftless Area stratigraphic sections corroborates loess stratigraphy along the length of the Mississippi Valley, where typically not more than four or five loess units are found and they represent only the late and middle Pleistocene (<790,000 yr B.P.). Past climatic conditions, which favored erosion of loess, as well as a temporally erratic spatial extent of former continental ice sheets in North America, which provided the dust supply, probably account for the low number of loess units along the Mississippi Valley.
Tropical Climatic Variation on the Pacific Slopes of the Ecuadorian Andes Based on a 25,000-Year Pollen Record from Deep-Sea Sediment Core Tri 163-31B
Authors: Heusser Linda E. , Shackleton Nicholas J. 
Published: September 2002

AbstractMarine sediments from 3°37′S, 83°58′W yield a well-dated pollen record of equatorial Andean vegetation. Moderate development of Podocarpus -high montane rainforest (∼34,000-28,000 yr B.P.) and increase of high Andean grassland pollen (∼28,000-16,000 yr B.P.) imply an extended dry, cool glacial period following a brief interstade. Rapid stepwise expansion in coastal and montane forest pollen characterizes the deglacial interval. The general correspondence between pollen and oxygen isotope variations in Tri 163-31B suggests that tropical climatic variations in the northern Andes were basically coherent with northern hemisphere glacier variations.
Determining Paleosol Topography Using Seismic Refraction
Authors: Rolph Tim C. , Shaw John , Derbyshire Edward , Zhisheng An 
Published: September 2002

AbstractThe seismic refraction reversed profiling technique has been used to investigate the topography of the last interglacial soil (paleosol S1) within the central Chinese Loess Plateau near Xifeng. The results suggest an essentially flat-lying soil at a depth which varies by only a few meters over an area of more than 10 km2. In addition, the results indicate a high-velocity layer at 50-60 m depth which is thought to coincide with a layer of carbonate concretions at the base of paleosol S5. The results agree well with the local loess-paleosol stratigraphy for this area and indicate that the seismic refraction method is a rapid technique for investigating paleotopography.
Holocene Sea-Level Rise Recorded by a Radiocarbon-Dated Mussel in a Submerged Speleothem beneath the Mediterranean Sea
Authors: Antonioli Fabrizio , Oliverio Marco 
Published: September 2002

AbstractFossil shells of the boring mussel Lithophaga lithophaga provide a means for dating changes in relative sea level. These bivalves, being among the first colonizers of bare calcareous substrates, can mark the earliest stages of marine submergence of caves. Here we report data concerning the deepest submerged speleothem presently sampled in a temperate area, at 48 m below present sea level off the west coast of Italy (Mediterranean Sea). A fossil mussel shell beneath encrusting layers from later marine colonists gave an AMS age of 9580 ± 35 14C yr B.P. (10,253 ± 72 cal yr B.P.).
Radiocarbon Dating of Soil Organic Matter
Authors: Wang Yang , Amundson Ronald , Trumbore Susan 
Published: September 2002

AbstractRadiocarbon ages of soil organic matter are evaluated with a model which incorporates the dynamics of the 14C content of soil organic matter. Measured 14C ages of soil organic matter or its fractions are always younger than the true ages of soils due to continuous input of organic matter into soils. Differences in soil C dynamics due to climate or soil depth will result in significantly different 14C signatures of soil organic matter for soils of the same age. As a result, the deviation of the measured 14C age from the true age of soil formation could differ significantly among different soils or soil horizons. Our model calculations also suggest that 14C ages of soil organic matter will eventually reach a steady state provided that no climatic or ecological perturbations occur. Once a soil or a soil horizon has reached a steady state, 14C dating of soil organic matter will provide no useful information regarding the age of the soil. However, for soils in which steady state has not been reached, it is possible to estimate the age of soil formation by modeling the measured 14C contents of soil organic matter. Radiocarbon dating of buried soils could, in general, overestimate the true age of the burial by as much as the steady-state age of the soil or soil horizon.
Atmospheric Circulation and Variations in Scandinavian Glacier Mass Balance
Authors: Pohjola Veijo Allan , Rogers Jeffrey C. 
Published: September 2002

AbstractMountain glaciers in Scandinavia are currently advancing while most of the monitored mountain glaciers of the world are retreating. We examine atmospheric circulation variability and compare changes in air pressure indices to changes in the mass balance of glaciers in the northeastern part of the Atlantic Ocean. The glacier mass balance correlates well with the strength of maritime flow in both winter and summer, the presence of high pressure over the Barents Sea being a critical factor in summer. The advance of Scandinavian glaciers is due partly to persistently strong westerlies over the northeastern Atlantic during post-1980 winters and partly to cold summertime flow, which together have helped maintain positive glacier net balance by decreasing ablation since 1980.
Quaternary Moraines vs Catastrophic Rock Avalanches in the Karakoram Himalaya, Northern Pakistan
Authors: Hewitt Kenneth 
Published: September 2002

AbstractA history and conception of glacial events for the central Karakoram Himalaya, proposed some 80 years ago by Giotto Dainelli, are largely accepted today. However, certain deposits identified as terminal moraine complexes marking glacial episodes were actually emplaced by rock avalanches. In the Skardu and Shigar intermontane basins of Baltistan, at least 15 rock avalanche events were previously mapped as moraine or till. Criteria used for distinguishing these catastrophic landslide deposits emphasize homogeneous lithology of rubble and matrix, clast shape, facies characteristics, the large scale unity of emplacement, and morphological relations to valley topography. The deposits of three events, at Katzarah, Satpura, and the north end of Shigar Valley, have been reconstructed in detail. Thick supraglacial debris does not result in similar deposits. Extensive valley fills, river terraces, large sediment fans, and lacustrine sediments formerly attributed to late-glacial conditions are reinterpreted as postglacial events involving rock avalanches that interrupted fluvial development. Existing reconstructions of glaciations are left in doubt, especially late-glacial events in the central Karakoram, as are the roles assigned to Karakoram, main Indus Valley, and western Himalayan ice.
High-Resolution Paleoclimatic Information from Chinese Eolian Sediments Based on Grayscale Intensity Profiles
Authors: Porter Stephen C. 
Published: September 2002

AbstractGrayscale intensity profiles from photographic images offer a rapid means of obtaining paleoclimate proxy records from Chinese loess, dune sand, and paleosols. Although the data can be obtained using conventional 35-mm film images, a digital camera and laptop computer will produce a high-resolution grayscale profile at a field site within minutes. Comparison of grayscale profiles with profiles of magnetic susceptibility measured down loess and dune-sand sections at sites on the Loess Plateau and Tibetan Plateau in a range of altitudes and climatic regimes shows that the two parameters are highly correlated. Therefore, grayscale intensity is a convenient alternative to magnetic susceptibility for generating paleoclimatic data in the loess and desert-margin regions of China. The resolution of both grayscale and susceptibility profiles ultimately is limited by bioturbation, which is most pronounced in paleosols.
Interglacial Growth of Tufa in Croatia
Authors: Horvatinčić Nada , Čalić Romana , Geyh Mebus A. 
Published: September 2002

AbstractTufa samples from the Krka River area in Croatia were dated by 14C and 230Th/234U methods. The study area is situated in the karst region of the southern Dinarides. 14C ages of 40 tufa samples collected at the waterfalls coincide with the early Holocene interglaciation, up to 6000 14C yr B.P. Comparison of conventional 14C dates of Holocene tufa and those of speleothems in the Dinaric Karst shows that speleothem formation started several thousand years earlier than tufa growth. Samples of old tufa deposits from the Krka River (17) and Plitvice Lakes (12) area and speleothem samples from caves in Dinaric Karst (5) yield 34 230Th/234U dates, most of which cluster around interglacial marine δ18O stage 5 (21). Eight of 13 older dates belong to interglacial stages 7 and 9; only 5 dates fall within stage 6 and 8 glaciations. 230Th/234U dates of speleothems and tufa samples from central Europe have indicated that these were formed preferentially during warm and humid interglacial and interstadial periods, and it appears that this is true of southern Croatia as well. Stable isotope (δ13C, δ18O) analyses of 40 tufa samples from the Krka River area were compared with stable isotope analyses of tufa from the Plitvice Lakes area. The δ13C values for both locations are similar and range from −10 to −6‰, indicating similar conditions of tufa formation. A systematic difference between the δ18O values of tufa in these two areas reflects the regional distribution of the oxygen composition of precipitation.
Modeling a 200-Yr Interruption of the Holocene Sapropel S1
Authors: Myers Paul G. , Rohling Eelco J. 
Published: September 2002

AbstractAn oceanic general circulation model, previously used to simulate the conditions associated with the Holocene Sapropel S1, is used to simulate the effects of a climate deterioration (represented as a cooling event) on the sapropelic circulation mode. The enhanced cooling (2°–3°C) induces deep convection in the Adriatic and the Gulf of Lions and intermediate water formation in the Aegean, where in all cases there had previously been only stagnant unventilated waters. The depths of ventilation (to ∼1250 m) are in agreement with core data from this period. The short decadal timescales involved in modifying the sapropelic circulation suggest that such a climatic deterioration may be associated with the interruption of S1 between 7100 and 6900 14C yr B.P., which divided the sapropel into two subunits.
Late-Glacial Environmental Changes South of the Wisconsinan Terminal Moraine in the Eastern United States
Authors: Russell Emily W.B. , Stanford Scott D. 
Published: September 2002

AbstractPalynological analyses of two sediment cores, one 2.4 m long from northern Delaware, dated about 16,300 to 14,70014C yr B.P., and one 1.8 m long from New Jersey just south of the Wisconsinan terminal moraine and dated about 13,600 to 12,50014C yr B.P., give the first detailed evidence of vegetation in this area during these periods. The overall assemblages are similar to each other, withPiceaandPinusdominating the arboreal pollen and Poaceae and Cyperaceae the herbaceous flora. Nonarboreal pollen contributes about 30–50% of the total, indicating a very open vegetation or a mix of forest patches and open areas. Especially in Delaware, there is a diversity of other herbaceous pollen, including members of the Asteraceae, Fabaceae, and Ranunculaceae. The assemblages do not resemble current North American tundra or boreal forest assemblages; rather, they resemble assemblages characteristic of tundra on recently exposed land surfaces north of the Wisconsinan terminal moraine. The persistence of the assemblages for 1500–2000 years in late-glacial time suggests stable and cold climate during this time of glacier retreat.
Ancient Meteorite Finds and the Earth's Surface Environment
Authors: Bland Philip A. , Bevan Alex W. R. , Jull A. J. Tim 
Published: September 2002

AbstractThe flux of meteorites to the Earth over the last 50,000 yr has remained approximately constant. Most meteorites that fall in temperate or tropical areas are destroyed on a time scale which is short compared to the rate of infall; however, in arid regions (both “hot” deserts and the “cold” desert of Antarctica) weathering is slower and accumulations of meteorites may occur. The initial composition for many meteorite groups is well known from modern falls, and terrestrial ages may be established from analyses of the abundance of cosmogenic radionuclides, providing an absolute chronology for recording terrestrial processes. As samples are falling constantly, and are distributed approximately evenly over the Earth, meteorites may thus be thought of as an appropriate “standard sample” for studying aspects of the terrestrial surface environment. Studies involving 14C and 36Cl terrestrial ages of meteorites, 57Fe Mössbauer spectroscopy (to quantify the degree of oxidation in samples), stable isotopes, and determination of halogen abundances are yielding information on the terrestrial history of meteorites: (i) terrestrial age and oxidation-frequency distributions for populations of samples allow the ages of surfaces to be estimated; (ii) differences in the weathering rate of samples between sites allows constraints to be imposed on the effect of climate on rock weathering rates; (iii) carbon isotopic compositions of generations of carbonate growth within meteorites allows, in some cases, temperatures of formation of carbonates to be estimated; (iv) structure in the oxidation–terrestrial age distribution for meteorites from some arid accumulation sites (specifically, the Nullarbor of Australia) appears to be linked to previous humid/arid cycles; (v) meteorite accumulations in Antarctica have been used to constrain aspects of the Quaternary evolution of the ice sheet, and terrestrial age and oxidation data have been used to constrain ice flow.
Precise Temporal Correlation of Holocene Mollusk Shells Using Sclerochronology
Authors: Marchitto Thomas M. , Jones Glenn A. , Goodfriend Glenn A. , Weidman Christopher R. 
Published: September 2002

AbstractAnnual growth bands of mollusk shells record several types of paleoenvironmental information, including geochemical proxies for water properties and morphological characteristics of growth and mortality. Sclerochronology, the marine counterpart of dendrochronology, offers a way to link individual shells together to form long continuous records of such parameters. It also allows for precise dating of recent shells and identification of contemporaneous fossil individuals. The longevity of the ocean quahogArctica islandica(commonly >100 yr) makes this species well suited for sclerochronology. Band width records of contemporaneousA. islandicaspecimens from the same region exhibit high correlations (ρ = 0.60–0.80 for spans of ≥30 bands), indicating some common environmental influences on shell growth. By adopting several strict criteria, fossil (dead-collected) shells can be linked into composite sclerochronologies. A seven-shell 154-yr chronology was constructed for Georges Bank using three live-collected and four dead-collected shells. Band width matching indicates that the dead-collected individuals died in A.D. 1950, 1971, 1978, and 1989. Sclerochronological age assignments were verified using aspartic acid racemization dating. Construction of a 1000-yr sclerochronology is judged to be feasible using the described methods.
Paleobiogeographic Changes at the Pleistocene–Holocene Boundary near Pintwater Cave, Southern Nevada
Authors: Hockett Bryan Scott 
Published: September 2002

AbstractIn 1996, approximately 70,000 mammal and lizard bones were recovered from Pintwater Cave in the northern Mojave Desert of southern Nevada. These bones date between 32,000 and 735014C yr B.P. Between 32,000 and 10,10014C yr B.P. the local fauna consisted of a mix of xeric- and cool/mesic-adapted species.Ochotona princepsandThomomys talpoidesthen occupied the region, although these animals were extirpated by the onset of the middle Holocene.Sauromalus obesusandDipodomys desertiprobably migrated to the region during the latest Pleistocene.Dipsosaurus dorsalisentered the Pintwater Cave record after 800014C yr B.P. Consistent with climatic interpretations for the northern Great Basin, these data suggest a cool and moist latest Pleistocene climate for the northern Mojave Desert. In contrast to the northern Great Basin, however, this region experienced predictable summer precipitation coupled with increasingly warmer winters by 10,10014C yr B.P. In both regions, the warm middle Holocene began ca. 830014C yr B.P. However, whereas the northern Great Basin probably experienced warm and dry conditions at that time, the northern Mojave Desert remained warm with relatively predictable summer precipitation. The modern northern Mojave Desert biota probably was not established until after 830014C yr B.P.
Comparison of Conventional K–Ar and 40Ar/39Ar Dating of Young Mafic Volcanic Rocks
Authors: Lanphere Marvin A. 
Published: September 2002

AbstractK–Ar and 40Ar/39Ar ages have been measured on nine mafic volcanic rocks younger than 1 myr from the Snake River Plain (Idaho), Mount Adams (Washington), and Crater Lake (Oregon). The K–Ar ages were calculated from Ar measurements made by isotope dilution and K2O measurements by flame photometry. The 40Ar/39Ar ages are incremental-heating experiments using a low-blank resistance-heated furnace. The results indicate that high-quality ages can be measured on young, mafic volcanic rocks using either the K–Ar or the 40Ar/39Ar technique. The precision of an 40Ar/39Ar plateau age generally is better than the precision of a K–Ar age because the plateau age is calculated by pooling the ages of several gas increments. The precision of a plateau age generally is better than the precision of an isotope correlation (isochron) age for the same sample. For one sample the intercept of the isochron yielded an 40Ar/36Ar value significantly different from the atmospheric value of 295.5. Recalculation of increment ages using the isochron intercept for the composition of nonradiogenic Ar in the sample resulted in much better agreement of ages for this sample. The results of this study also indicate that, given suitable material and modern equipment, precise K–Ar and 40Ar/39Ar ages can be measured on volcanic rocks as young as the latest Pleistocene, and perhaps even the Holocene.
Glacio-isostasy and Glacial Ice Load at Law Dome, Wilkes Land, East Antarctica
Authors: Goodwin Ian D. , Zweck Christopher 
Published: September 2002

AbstractThe Holocene sea-level high stand or “marine limit” in Wilkes Land, East Antarctica, reached ∼30 m above present sea level at a few dispersed sites. The most detailed marine limit data have been recorded for the Windmill Islands and Budd Coast at the margin of the Law Dome ice cap, a dome of the East Antarctic Ice Sheet (EAIS). Relative sea-level lowering of 30 m and the associated emergence of the Windmill Islands have occurred since 6900 14C (corr.) yr B.P. Numerical modeling of the Earth's rheology is used to determine the glacio-isostatic component of the observed relative sea-level lowering. Glaciological evidence suggests that most of EAIS thickening occurred around its margin, with expansion onto the continental shelf. Consequently, a regional ice history for the last glacial maximum (LGM) was applied in the glacio-isostatic modeling to test whether the observed relative sea-level lowering was primarily produced by regional ice-sheet changes. The results of the modeling indicate that the postglacial (13,000 to 8000 14C yr B.P) removal of an ice load of between 770 and 1000 m from around the margin of the Law Dome and adjacent EAIS have produced the observed relative sea-level lowering. Such an additional ice load would have been associated with a 40- to 65-km expansion of the Law Dome to near the continental shelf break, together with a few hundred meters of ice thickening on the adjoining coastal slope of the EAIS up to 2000 m elevation. Whereas the observed changes in relative sea level are shown to be strongly influenced by regional ice sheet changes, the glacio-isostatic response at the Windmill Islands results from a combination of regional and to a lesser extent, Antarctic-wide effects. The correspondence between the Holocene relative sea-level lowering interpreted at the margin of the Law Dome and the lowering interpreted along the remainder of the Wilkes Land and Oates Land coasts (105°–160° E) suggests that a similar ice load of up to 1000 m existed along the EAIS margin between Wilkes Land and Oates Land.