bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rock-Weathering Rates as Functions of Time
Authors: Colman Steven M. 
Published: December 2004

AbstractThe scarcity of documented numerical relations between rock weathering and time has led to a common assumption that rates of weathering are linear. This assumption has been strengthened by studies that have calculated long-term average rates. However, little theoretical or empirical evidence exists to support linear rates for most chemical-weathering processes, with the exception of congruent dissolution processes. The few previous studies of rock-weathering rates that contain quantitative documentation of the relation between chemical weathering and time suggest that the rates of most weathering processes decrease with time. Recent studies of weathering rinds on basaltic and andesitic stones in glacial deposits in the western United States also clearly demonstrate that rock-weathering processes slow with time. Some weathering processes appear to conform to exponential functions of time, such as the square-root time function for hydration of volcanic glass, which conforms to the theoretical predictions of diffusion kinetics. However, weathering of mineralogically heterogeneous rocks involves complex physical and chemical processes that generally can be expressed only empirically, commonly by way of logarithmic time functions. Incongruent dissolution and other weathering processes produce residues, which are commonly used as measures of weathering. These residues appear to slow movement of water to unaltered material and impede chemical transport away from it. If weathering residues impede weathering processes then rates of weathering and rates of residue production are inversely proportional to some function of the residue thickness. This results in simple mathematical analogs for weathering that imply nonlinear time functions. The rate of weathering becomes constant only when an equilibrium thickness of the residue is reached. Because weathering residues are relatively stable chemically, and because physical removal of residues below the ground surface is slight, many weathering features require considerable time to reach constant rates of change. For weathering rinds on volcanic stones in the western United States, this time is at least 0.5 my.
The Northern Limits of Glacial Lake Algonquin in Upper Michigan
Authors: Futyma Richard P. 
Published: December 2004

AbstractA number of ancient shorelines formed by late-Pleistocene proglacial lakes have been found in eastern upper Michigan. These shorelines delimit several water planes, the uppermost of which is correlated with the Main Lake Algonquin stage. This correlation is based on the continuity of the highest water plane with Main Algonquin shorelines in Wisconsin and Ontario, the strength of the shoreline features, its altitudinal relationship with lower water planes, and a reinterpretation of radiocarbon dates from the Sault Ste. Maria area. The isobases of this water plane have a bearing of S75°E. At the time of the maximum extent of Lake Algonquin, ca. 10,600 yr B.P., its northern, ice-limited border lay along the Munising moraine, the northernmost of the two main morainic systems of eastern upper Michigan. This interpretation lends support to the idea of a period of slow deglaciation from ca. 11,000 to 10,000 yr B.P. An ice lobe occupied the central Lake Superior basin until early Holocene time. Radiocarbon dates on wood found beneath till or outwash at several sites indicate a minor ice readvance from the central Lake Superior basin ca. 10,000 yr B.P. If true, this would have prevented the development of the post-Duluth series of glacial lakes in the western Lake Superior basin until ca. 9900 yr B.P., well after the end of the main Lake Algonquin stage.
Major Change in Atlantic Deep and Bottom Waters 700,000 yr Ago: Benthonic Foraminiferal Evidence from the South Atlantic
Authors: Peterson L. C. , Lohmann G. P. 
Published: December 2004

AbstractIn the modern South Atlantic the transition between deep water and bottom water is marked by a clear change in the associated benthonic foraminiferal fauna. Uvigerina and Globocassidulina characterize oxygen-poor Circumpolar Deep Water which has long been isolated from the surface. Planulina and miliolids are found associated with the more newly formed, oxygen-rich North Atlantic Deep Water. Antarctic Bottom Water is characterized by “Epistominella” umbonifera. Analysis of the benthonic foraminiferal faunas in two sediment cores recovered from the Vema and Hunter Channels in the western South Atlantic shows that the level of the transition between deep and bottom waters shallowed sharply about 700,000 yr ago. This rise indicates a sharp, sustained increase in the volume of bottom water flowing through the South Atlantic after this time. Prior to about 700,000 yr ago, the amount of Antarctic Bottom Water entering the western South Atlantic was greatly reduced and Circumpolar Deep Water apparently accounted for the bulk of northward flow. Production of southward-flowing North Atlantic Deep Water seems not to have been affected. The timing of this change in circulation regime suggests a possible causal link to similar changes in records of terrestrial and sea-surface climate.
Evidence of Stream Response to Holocene Climatic Change in a Small Wisconsin Watershed
Authors: McDowell Patricia F. 
Published: December 2004

AbstractDuring the Holocene, moderate climatic and vegetational changes triggered several episodes of adjustment in the Brush Creek fluvial system. The alluvial chronology includes an episode of erosion at 7800 – 5700 yr B.P. corresponding to the mid-Holocene precipitation minimum and an episode of floodplain construction at 5700 – 5000 yr B.P. corresponding to a rapid increase in precipitation. Holocene climatic changes have influenced the sedimentology of the alluvial deposits and soil development on them. Fluvial adjustment is caused primarily by hydrologic and hydraulic changes related to climatic change, but there is no simple model for fluvial response to climatic change. The relationship between the direction of climatic change and the type of fluvial response is complex.
Age Dating and the Orbital Theory of the Ice Ages: Development of a High-Resolution 0 to 300,000-Year Chronostratigraphy
Authors: Martinson Douglas G. , Pisias Nicklas G. , Hays James D. , Imbrie John , Moore Theodore C. , Shackleton Nicholas J. 
Published: December 2004

AbstractUsing the concept of “orbital tuning”, a continuous, high-resolution deep-sea chronostratigraphy has been developed spanning the last 300,000 yr. The chronology is developed using a stacked oxygen-isotope stratigraphy and four different orbital tuning approaches, each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data. Each approach yields a separate chronology. The error measured by the standard deviation about the average of these four results (which represents the “best” chronology) has an average magnitude of only 2500 yr. This small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used. Excellent convergence between chronologies developed using each of five different paleoclimatological indicators (from a single core) is also obtained. The resultant chronology is also insensitive to the specific indicator used. The error associated with each tuning approach is estimated independently and propagated through to the average result. The resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr, in excellent agreement with the 2500-yr estimate. Transfer of the final chronology to the stacked record leads to an estimated error of ±1500 yr. Thus the final chronology has an average error of ±5000 yr.
Late Weichselian and Holocene Relative Sea-level History of Bröggerhalvöya, Spitsbergen
Authors: Forman Steven L. , Mann Daniel H. , Miller Gifford H. 
Published: December 2004

AbstractRadiocarbon-dated whalebones from raised beaches record a relative sea-level history for Bröggerhalvöya, western Spitsbergen that suggest a two-step deglaciation on Svalbard at the end of the late Weichselian glaciation. The late Weichselian marine limit was reached at about 13,000 yr B.P. and was followed by relatively slow emergence until about 10,000 yr B.P. either in response to ice unloading in the Barents Sea, initial retreat of local fjord glaciers, or some combination of the two. Rare whale skeletons dating between 13,000 and 10,000 yr B.P. indicate that the Norwegian Sea was at least seasonally ice free during that interval. Deglaciation of Spitsbergen is recorded by the rapid emergence of Bröggerhalvöya after 10,000 yr B.P. This was followed by a transgression during the mid-Holocene, here named the Talavera Transgression, and another in modern times. Raised beach morphologies suggest striking differences in nearshore depositional processes before and after 10,000 yr B.P. that are probably related to changes in the rate of uplift and in sea-ice conditions.
Chironomidae (Diptera) and Postglacial Climate at Marion Lake, British Columbia, Canada
Authors: Walker Ian R. , Mathewes Rolf W. 
Published: December 2004

AbstractChironomid (midge) remains analyzed from an 8.95-m-long sediment core from Marion Lake reveal successional changes over the last 12,000 yr since deglaciation. A late-glacial Heterotrissocladius-dominated association characterizes the earliest sediments. Succeeding this community, at the onset of the Holocene, is a Tanytarsini-dominated assemblage. The transition between these communities occurs during a time of rapid climatic amelioration, preceding an early Holocene xerothermic interval. The late-glacial fossil fauna is suggestive of more northerly affinities. Similar sequences have been reported in late-glacial lake sediments elsewhere in North America and in Europe. The composite picture of these chironomid assemblages suggests the gradual retreat of a formerly widely distributed, cold stenothermous fauna. The response of the chironomid community accords well with paleoclimatic inferences based on pollen data at the lake. Subsequent postglacial changes are less pronounced and most are probably attributable to the gradual shallowing of the basin. Chironomid remains from shallow, weakly stratified lakes may yield valuable paleoclimatological data.
Terrestrial Gastropod Succession in a Late Holocene Stream Deposit in South Texas
Authors: Neck Raymond W. 
Published: December 2004

AbstractInvestigation of snail-bearing alluvium from the Smyth Crossing site in Uvalde County, Texas, indicates that the terrestrial gastropod fauna of this area has been stable for at least 3000 yr. However, relative proportions and presence/absence variations indicate changes in the relative occurrence of preferred microhabitats of certain snails. Gastropods from an excavated soil column reveal a succession of gastropod associations in response to succession of the plant community of the site from a riverside gravel bar to an upland savannah/grassland. Human impact on the gastropods is mostly contemporary, with apparent local extirpations of some species having occurred. The recovered paleofaunas provide no evidence for regional climatic change since 3000 yr B.P.
Comparison of Thermoluminescence and Radiocarbon Age-Determinations from Late-Pleistocene Alluvial Deposits Near Sydney, Australia
Authors: Nanson G.C. , Young R.W. 
Published: December 2004

AbstractRadiocarbon and thermoluminescence (TL) age-determinations have been obtained for a large Pleistocene alluvial terrace on the Nepean River near Sydney, New South Wales, Australia. The deposit was laid down by a braided river system prior to the last glacial maximum. Six thoroughly pretreated samples of charcoal and degraded wood buried within gravels at the base of the terrace yielded apparent 14C ages of ∼37,000–42,000 yr B.P. These compare favorably with four TL determinations that gave apparent ages of ∼41,000–47,000 yr B.P. for the same deposit. Adjustment of the 14C ages to take geomagnetic effects into account further improves the correlation between these two independent dating techniques. In addition, 14C and TL correctly identified a reworked portion of the fine-grained alluvial overburden as being substantially younger than the main body of the terrace. These results augur well for the usefulness of TL age determinations of certain alluvial deposits.
Late-Glacial and Holocene Glacier Fluctuations and Environmental Change on South Georgia, Southern Ocean
Authors: Clapperton Chalmers M. , Sugden David E. , Birnie Jacqueline , Wilson Mandy J. 
Published: December 2004

AbstractSouth Georgia provides a terrestrial record of postglacial environmental change from a largely oceanic zone of the Earth. The record is representative of the southern westerlies and provides a link between Antarctica and the temperate zones of southern South America. Evidence from glacial geomorphology, slope stratigraphy, and analyses of environmental indicators in peat and lake cores is used to interpret this record. Wastage of the full-glacial ice cap was interrupted by a late-glacial stade of the outlet and valley glaciers before ca. 10,000 yr B.P. Plant growth had begun at low altitude (<50 m) on the sheltered (lee side) northeast coast within the late-glacial moraine limits by 9700 yr B.P. Environmental conditions on slopes above 80 m probably were too rigorous for a stable vegetation cover until ca. 6400 yr B.P. This was followed by a period from 5600 to 4800 yr B.P. when conditions were warmer than at present by up to 0.6°C. Periods of climatic cooling occurred at ca. 4800-3800 yr B.P., ca. 3400-1800 yr B.P., and within the last 1400 yr. The most extensive Holocene advance of South Georgia glaciers culminated just before 2200 yr B.P. These Holocene temperature changes of between 0.5 and 1.0°C are comparable in scale and timing to those identified from recent analyses of Vostok ice cores from the Antarctic ice sheet.
Accuracy of North American Human Skeleton Ages
Authors: Stafford Thomas W. , Hare P.E. , Currie Lloyd , Jull A. J. T. , Donahue Douglas 
Published: December 2004

AbstractAccelerator mass spectrometry (AMS) radiocarbon dates fail to provide conclusive evidence that all New World human fossils are younger than approximately 11,000 yr. Because fossil bones vary widely in preservation, their radiocarbon dates are not equally accurate. Molecular-level radiocarbon dating, which used individual amino acids to assess fossil diagenesis, revealed that dates on known-age, noncollagenous bone were underestimated by at least 2000 to 9000 yr. The significance is that >11,000-yr-old fossil bones with poor preservation would yield Holocene and not Pleistocene radiocarbon ages, regardless of what chemical pretreatment or 14C counting method was used. Irreplaceable evidence for Pleistocene-age fossils in the New World could be lost if the diagenesis of fossil bones is not evaluated before the bones are radiocarbon dated. In contrast, radiocarbon ages for collagenous fossils can be determined more accurately if 14C is measured in several individual amino acids that are isolated from collagenous bone protein. Molecular-level radiocarbon dating will greatly improve not only the accuracy of chronologies for human migrations and animal extinctions, but of all late Quaternary chronologies that are based upon the 14C dating of fossil proteins.
Correlation of the Holocene Jarvis Creek, Tangle Lakes, Cantwell, and Hayes Tephras in South-Central and Central Alaska
Authors: Begét James E. , Reger Richard D. , Pinney DeAnne , Gillispie Tom , Campbell Kathy 
Published: December 2004

AbstractThe geochemistry, petrography, and distribution of the Jarvis Creek Ash (Péwé, 1965, 1975a) indicate that this tephra from the lower Delta River area of central Alaska is correlative with vol volcanic ash from sites in south-central Alaska near Tangle Lakes (upper Delta River area) and the Cantwell ash from Hayes volcano found in the upper Nenana River area (Riehle et al., 1990). Volcanic glass compositions of distal Jarvis Creek and Tangle Lakes tephra samples are compositionally restricted, while several discrete glass populations are present in some samples are compositionally collected nearer Hayes volcano. These correlations extend the known distribution of Hayes volcano tephras across the Alaska Range and into central Alaska, a distance of more than 650 km. New geochronologic data for the Jarvis Creek Ash suggest it was deposited ca. 3660 ± 125 yr B.P., consistent with previous age estimates of tephra eruptions at the Hayes volcano. The name “Jarvis Creek Ash” has well-established priority with respect to “Cantwell ash” or other local names for this tephra layer from the Hayes volcano.
Periodic Variations in Late Pleistocene Speleothem Abundance in Britain
Authors: Kashiwaya Kenji , Atkinson Timothy C. , Smart Peter L. 
Published: December 2004

AbstractTemporal change in the growth of speleothems in the United Kingdom during the past 150,000 years is shown to be related to the insolation variation by the Milankovitch theory. The speleothem data compiled by Gordon et al. (1989. Quarternary Research 31, 14–26) have two Milanokovitch frequencies: the ca. 40,000-yr period related to change in the earth's obliquity and the ca. 20,000-yr period related to the precession of the equinoxes. The abundance of speleothem growth was, in general, large during the last interglaciation and small during the last glaciation. In both periods, however, speleothem abundance was greater during periods of strong insolation and less during weak insolation.
Land-Sea Correlations and Evolution of the Cambridge Fiord Marine Basin during the Last Deglaciation of Northern Baffin Island
Authors: Stravers Jay A. , Syvitski James P.M. 
Published: December 2004

AbstractCambridge Fiord functions as a major outlet trough whenever Laurentide ice approaches the eastern coast of Baffin Island. During the last glacial maximum (late Foxe glaciation), an outlet glacier occupied most of the fiord, possibly terminating as far seaward as Buchan Gulf. Glacier retreat began prior to 8800 yr B.P. and was punctuated by the formation of two onshore moraines with upper age limits of 7900 and 7200 yr B.P. Correlative offshore moraines (recognized on seismic reflection profiles) formed prominent submarine sills which partitioned the fiord into three basins. These formed effective sediment traps that restricted the seaward migration of debris flows and turbidites, thus facilitating the accumulation of thick (> 100 m) stratified glacialmarine sediments in the inner fiord. Correlations of onshore and offshore moraines allow time lines to be placed within an offshore seismic stratigraphic section that is inaccessible to piston coring. Resultant estimates of sediment accumulation rates give a mean value of 2.34 × 106 m3/yer for deposits trapped in the inner fiord basins. These thick sequences of sediments do not represent extended Foxe/Wisconsin time periods, but, rather, were rapidly deposited in the inner fiord during the last deglaciation.
Source Areas and Transport Mechanisms for Freshwater and Brackish-Water Diatoms Deposited in Pelagic Sediments of the Equatorial Atlantic
Authors: Pokras Edward M. 
Published: December 2004

AbstractDistributions of freshwater and brackish-water diatoms from dust samples and modern sediments of the equatorial Atlantic demonstrate different transport mechanisms and source areas. Both Melosira spp. and Stephanodiscus spp. are transported via winds from the southern Sahara and Sahel in Northern Hemisphere winter. The core-top distribution of Cyclotella striata delineates the extent of the low-salinity plume formed by runoff from the Zaire River into the extreme eastern Atlantic. The transport mechanism and source areas for Melosira spp. during arid phases have not changed appreciably in the last 130,000 yr. There is no evidence for long-distance transport of freshwater diatoms by the southeast trade winds. This study confirms the validity of paleoclimatic research which inferred eolian transport of Melosira spp. in the winter dust plume from source regions north of the equator, although fluviatile input of Melosira valves into nearshore sediments cannot be ruled out.
Effects of Schistosoma mansoni infection on inorganic elements in the snail Biomphalaria glabrata
Authors: Ong J.H.L. , Chejlava M. , Fried B. , Koehnlein K.M. , Bosavage G.L. , Sherma J. 
Published: December 2004

AbstractInductively coupled plasma atomic emission spectrometry (ICP-AES) was used to study element ions in whole bodies of uninfected Biomphalaria glabrata snails and those experimentally infected with larval Schistosoma mansoni trematodes. Infected snails were analysed 8 weeks post-infection. Cohort snails that were left uninfected were analysed at the same time as the infected snails. Sixteen elements (aluminum, boron, barium, calcium, cadmium, copper, iron, potassium, magnesium, manganese, sodium, nickel, lead, selenium, tin and zinc) were found to be present in infected and uninfected whole bodies at concentrations above the detection limit of the ICP-AES analysis. Of these, calcium, cadmium, manganese and sodium were present in significantly higher amounts (Student's t-test, P<0.05) in whole infected versus whole uninfected snails. Variations in the present results compared with other studies reflect intrinsic differences in the larval trematode–snail systems used.
Prevalence of Libyostrongylus douglassii in commercially reared ostriches in the highveld region of Zimbabwe
Authors: Mukaratirwa S. , Cindzi Z.M. , Maononga D.B. 
Published: December 2004

AbstractA total of 435 freshly dropped faecal samples were collected from 11 randomly selected ostrich farms during September and November 2002 to determine the prevalence of Libyostrongylus douglassii (ostrich wireworm) in the highveld region of Zimbabwe. Samples, which consisted of 339 samples from breeder birds and 96 samples from pre-slaughter grower birds were screened for nematode eggs using the modified McMaster technique before being individually cultured in an incubator at 28°C. Cultures were examined for the presence of L. douglassii third stage larvae (L3). Using faecal egg counts, eight of 11 farms (72.7%) were positive for L. douglassii in breeders but no eggs were detected in the growers. The faecal culture method detected wireworm larvae in the breeding stock of all farms that were surveyed (100%) and five of the eight farms (62.5%) which had grower birds. Libyostrongylus douglassii was detected in all farms (100%) based on the faecal culture method. Libyostrongylus douglassii was detected for the first time in 7 of 11 farms (64%) surveyed. Data from questionnaires designed to assess farm management practices showed that four out of seven (57.1%) of the ostrich producers were unaware of the importance of wireworms in ostriches. The farms did not have a regular deworming programme for their birds and no faecal samples were sent routinely to the veterinary laboratory for screening of wireworms. Wireworm infections were not taken into consideration by farmers during buying and selling of birds.
Metacercariae of Clinostomum attenuatum in Ambystoma tigrinum mavortium, Bufo cognatus and Spea multiplicata from west Texas
Authors: Miller D.L. , Bursey C.R. , Gray M.J. , Smith L.M. 
Published: December 2004

AbstractTissues from barred tiger salamanders (Ambystoma tigrinum mavortium), Great Plains toads (Bufo cognatus) and New Mexico spadefoots (Spea multiplicata) collected from 16 playa wetlands in Texas during 1999 and 2000 were examined by light microscopy. Digenean cysts were primarily distributed subcutaneously throughout the specimens and occasionally coelomic invasion was noted. The parasites within the cysts were 1.5–2 mm in diameter, with a thin (c. 10 μm wide) eosinophilic-staining tegument, two suckers (oral and ventral), posteriorly located primordial genitalia and paired digestive caeca. These digeneans were identified as the metacercariae of Clinostomum attenuatum. This is the first record of Clinostomum attenuatum in these amphibian species.