bluuebunny/crossref_metadata_2025 huggingface dataset:
Dating Climatic Episodes of the Holocene
Authors: Wendland Wayne M. , Bryson Reid A.
Published: December 2004

Monitoring evidence indicates that the Holocene embraced a sequence of rather discrete climatic episodes. The transitions between these environmental episodes apparently were abrupt and globally synchronous. This paper reports on statistical analyses of radiocarbon dates associated with environmental change and cultural change.

Over 800 14C dates associated with pollen maxima and minima, sea level maxima and minima, and top and bottom surfaces of peat beds were simultaneously analyzed to identify times of globally synchronous environmental discontinuities.

Some 3700 14C dates associated with 155 cultural continua of the world were collectively analyzed to identify worldwide synchroneities in appearance and termination of the cultures.

Significant globally synchronous discontinuities were identified in each independent analysis. The dates of environmental and cultural discontinuities are rather similar, particularly during the recent half of the Holocene. The fact that the cultural discontinuities mostly follow rather closely those of the paleobotanical record suggests that there has been a distinct climatic impact on the cultural history of man.
Quaternary Deposits in Southwestern Afghanistan
Authors: Smith George I.
Published: December 2004

Geologic evidence in the closed Seistan Basin of southwestern Afghanistan and adjacent parts of Iran and Pakistan indicates that a lake as much as 65,000 sq km in size occupied this closed depression during Pleistocene time. The deposits consist mostly of lacustrine silt and clay and have a maximum observed thickness of about 250 m. A layer of alluvial gravels overlies the sequence. The deposits are probably early or middle Pleistocene in age; they are old enough to have sustained nearly 300 m of erosion over large areas but are not faulted or detectably folded in the central part of the basin although they are upwarped along the west edge of the basin.

Sand dunes cover extensive areas of the basin. Dune orientation shows that the strong surface winds enter the basin blowing toward the south-southeast and then are deflected to the east, apparently as a response to mountains bordering the basin on its south side. The Gawdezereh, a large deflation depression, may be a result of an augmented excavation ability of winds that occurs where turbulence is created along a zone of deflection.
Palynology and Depositional Environment of the Río Ignao Nonglacial Deposit, Province of Valdivia, Chile
Authors: Heusser Calvin J.
Published: December 2004

In south-central Chile, the Río Ignao nonglacial deposit with a minimal radiocarbon age of 56,000 +2000, −1700 yr shows the following sequence of pollen assemblages, starting with the oldest: Gramineae (zone 1), Gramineae-Corynabutilon-Lomatia-Ovidia (zone 2), Nothofagus-Embothrium-Gramineae (zone 3A), Nothofagus-Gramineae-Tubuliflorae (zone 3B and D), and Nothofagus-Drimys-Myrtaceae (zone 3A). This sequence implies an initial dry and rather cold climate that later became wetter and somewhat warmer, reached a warm peak, and ultimately became colder and drier. At the warmest time, the Andean tree line is estimated to have been about 900 m lower and average January (summer) temperature about 3–4°C colder than at present. The Río Ignao deposit is believed to represent an early interstade of the last glaciation, known in southern Chile as the Llanquihue Glaciation.
Calcium Carbonate dissolution History in Late Quaternary Deep-sea Sediments, Western Gulf of Mexico
Authors: Thunell Robert C.
Published: December 2004

Calcium carbonate dissolution has been studied in eight piston cores from the western Gulf of Mexico ranging in depth from 965 to 3630 m. The degree of dissolution throughout the cores was determined by studies of foraminiferal test fragmentation, benthonic foraminiferal abudance, calcium carbonate concentration, and various relationships between solution-resistant and solution-susceptible species. The paleoclimatic history recorded in these cores is similar to those defined previously in the Gulf of Mexico and equatorial Atlantic. Two mesgascopically distinct ash layers and well-defined planktonic foraminiferal subzones permit precise intercore correlation of dissolution horizons. All cores demonstrate intense dissolution during several subzones, especially during the early-middle Y, X1, and W1. Other less consistent dissolution horizons occur in various cores. Sedimentation rates increase while calcite concentrations decrease during glacial episodes suggesting increased dilution by terrigenous materials. Despite this, glacial episodes show greater dissolution and worse preservation of foraminiferal tests. Therefore, increased dissolution of calcium carbonate during glacial episodes must be a function of some mechanism that more than compensates for the increased rate of burial by terrigenous sediments. Dissolution is dissolution processes are not responsible for the observed effects. The oxidation of organic material may be the primary mechanism controlling the dissolution of calcium carbonate in the western Gulf of Mexico.
Comparison of Radiolarian/Planktonic Foraminiferal Paleoceanography of the Subantarctic Indian Ocean
Authors: Williams Douglas F. , Keany John
Published: December 2004

A detailed paleoceanographic history of the Subantarctic region for the last million years was determined using paleomagnetic stratigraphy, radiolarian and planktonic foraminiferal biostratigraphy, and the oxygen isotope record from stages 1 to 13 (0.5 MY) in a deep-sea core (E45-74) from the southern Indian Ocean. Changes in the abundances ofAntarctissa strelkoviandNeogloboquadrina pachydermarecord 12 glacial/interglacial cycles. The paleoceanographic events based on the combined results of these siliceous and calcareous indexes agree with changes in the global ice-volume record. Calcium carbonate dissolution selectively alters the planktonic foraminiferal fauna and causes test fragmentation and increased numbers of benthic foraminifera and radiolarians. Intense periods of calcium carbonate dissolution are associated principally with glacial episodes and are probably related to increased Antarctic bottom-water activity as well as changes in surface-water mass positions.
Age of the Last Major Scabland Flood of the Columbia Plateau in Eastern Washington
Authors: Mullineaux Donal R. , Wilcox Ray E. , Ebaugh Walter F. , Fryxell Roald , Rubin Meyer
Published: December 2004

Pumice layers of set S from Mount St. Helens can be correlated with certain ash beds associated with young flood deposits of the channeled scabland. The correlation points to an age of about 13,000 14C yr B.P. for the last major flood to have crossed the scabland. Until recently, the last major episode of flooding was thought to be closer to 20,000 yr B.P., an age inferred chiefly from the relation of the flood to glacial events of the northern Rocky Mountains. Several investigations within the last few years have suggested that the last major flood occurred well after 20,000 yr B.P. Tentative correlations of ash beds of the scabland with set S pumice layers, the relations of flood and glacial events along the northwestern margin of the Columbia Plateau, and a radiocarbon date from the Snake River drainage southeast of the plateau all indicate an age much younger than 20,000 yr. The postulated age of about 13,000 yr B.P. is further supported by a radiocarbon date in the Columbia River valley downstream from the scabland tract. Basal peat from a bog on the Portland delta of Bretz, which is a downvalley deposit of the last major scabland flood, has been dated as 13,080 ± 300 yr B.P. (W-3404).
The Marine Oxygen Isotope Record in Pleistocene Coral, Barbados, West Indies
Authors: Fairbanks Richard G. , Matthews R.K.
Published: December 2004

The reef-crest coral Acropora palmata from late Pleistocene reefs on Barbados has recorded the same global variations in oxygen isotopes as planktonic and benthonic foraminifera. Although the record of oxygen isotopes in Acropora palmata is discontinuous, it offers several advantages over the isotope records from deep-sea sediments: (1) the coral grows at water depths of less than 5 m; (2) the samples are unmixed; (3) specimens may be sampled from various elevations of paleo-sea level; and (4) aragonitic corals are suitable for 230Th/234U and He/U dating techniques. The latter advantage means that direct dating of the marine oxygen isotope record is possible. Oxygen isotope stage 5e corresponds to Barbados III, dated at 125,000 ± 6000 yr BP. Petrographic and geochemical evidence from five boreholes drilled into the south coast of Barbados indicates a major eustatic lowering (greater than 100 m below present sea level) occurred between 180,000 and 125,000 yr BP. The age and isotopic data suggest correlation of this change in sea level to Emiliani's oxygen isotope stage 6. Acropora palmata deposited at various elevations of sea level during oxygen isotope stage 6 vary by 0.11 ‰ δ18O for each 10 m of change in sea level. We further hypothesize a minimum drop of 2°C in the average temperature occurred during the regressive phase of oxygen isotope stage 6. These data indicate that temperature lowering of surface water near Barbados lagged behind a major glacial buildup during this time period. Using the δ18O vs sea level calibration herein derived, we estimate the relative height of sea stands responsible for Barbados coral reef terraces in the time range 80,000 to 220,000 yr BP.
Multivariate Statistical Estimates of Holocene Vegetation and Climate Change, Forest-Tundra Transition Zone, NWT, Canada
Authors: Kay Paul A.
Published: December 2004

Newly derived fossil pollen data were obtained from four sites along a transect from the boreal forest limit into tundra in the eastern Northwest Territories. Multivariate statistical analyses were employed to interpret the pollen assemblages. Transfer functions were constructed between the pollen data and climatic data, and paleoclimatic estimates were derived. The objective nature of the reconstructions provides an independent verification of the general outlines of the chronology of tree-line movements during the mid- and late-Holocene as established in previous paleosol and pollen studies. Boreal forest extended to approximately 62°N, associated with mean July temperatures 1 to 3°C above modern means, from at least 5500 to 3700 yr B.P. Although a major episode of southward displacement of tree line at about 3700 yr B.P. is recorded, later events are not clearly represented. Considerations of the statistics, the time scales, and the nature of the pollen rain suggest only conservative interpretations of the results are possible. It is suggested that the pollen sites may have been sensitive recorders of regional vegetation change only when they were near the ecotone, corresponding to a climatic threshold.
Holocene Insect Fossils from Two Sites at Ennadai Lake, Keewatin, Northwest Territories, Canada
Authors: Elias Scott A.
Published: December 2004

Ennadai Lake, in the forest-tundra ecotonal region of Keewatin, Northwest Territories, Canada, has been the subject of several paleoecological investigations (palynology, plant macrofossils, fossil soils). This study concerns Holocene insect fossils at Ennadai, a new approach in a region shown to be sensitive to climatic change. The Ennadai I site yielded 53 taxa, representing 13 families of Coleoptera and 7 families of other insects and arachnids, including abundant ants. These fossils range in age from about 6300 to 630 yr B.P. The Ennadai II site produced fossils of 58 taxa, including 13 beetle families and 15 families of other arthropods, ranging in age from 4700 to 870 yr B.P. The insect evidence suggests the presence of trees in the Ennadai region from 6000 to 2200 yr B.P. A conifer pollen decline from 4800 to 4500 yr B.P. at Ennadai has previously been interpreted as an opening up or retreat of forest in response to climatic cooling, but the insect fossils reveal the continued presence of trees during this interval. Both insect assemblages suggest trends of forest retreat and tundra expansion between about 2200 and 1500 yr B.P., presumably due to climatic cooling, with a return of woodland by about 1000 yr B.P.
Recent Rainfall Trends on the Margins of the Subtropical Deserts: A Comparison of Selected Northern Hemisphere Regions
Authors: Byrne Roger , Granger Orman , Monteverdi John
Published: December 2004

An analysis of recent (1898–1972) seasonal rainfall data from California (winter) and Mexico (summer) provides no evidence of an inverse relationship such as has been reported by Winstanley for climatically analogous areas of Eurasia and Africa. However, California and Old World winter rain trends have been remarkably similar during this time period. Also, summer rain in northwestern Mexico (Mazatlan) correlates highly with winter rainfall in southern California (San Diego) when allowance is made for a 7-year lag. Winstanley suggested that the expansion and contraction of the circumpolar vortex is a primary control of rainfall trends on the margins of the subtropical deserts. The alternative proposed here is that, at least on this time scale, variations in the longitudinal position of troughs and ridges in the upper air westerlies are more important.
Pollen Analysis of Some Mid-Pleistocene Interglacial Lagoonal Sediments from Southern Delaware
Authors: Nickmann Rudy J. , Demarest James M.
Published: December 2004

Results of pollen analysis on lagoonal sediments from southern Delaware, dated at 500,000–1,000,000 yr B.P. by amino acid racemization, are presented. Three pollen zones are identified in sediments that were deposited during the final stage of an interglacial cycle. A closed forest of mixed conifer-deciduous trees dominated by Tsuga, Pinus, Fagus, Liquidambar, and Quercus is recorded in the basal zone (Zone I). The inferred climate at this time was temperate and moist. A probable lowering of sea level during the deposition of Zone II exposed large areas in the surrounding estuaries and tidal flats which were colonized by marsh and bog plant taxa. Zone III is characterized by Pinus, Quercus, and Picea pollen. A scrub oak-pine association may have been favored on the coarse sandy soils of the Delmarva Peninsula at this time because of a drop in the local water table. The inferred climate during this interval was colder and probably drier than in Zone I.
Historic Eruptions of Tambora (1815), Krakatau (1883), and Agung (1963), their Stratospheric Aerosols, and Climatic Impact
Authors: Rampino Michael R. , Self Stephen
Published: December 2004

Decreases in surface temperatures after the eruptions of Tambora (1815), Krakatau (1883), and Agung (1963) were of similar magnitude, even though the amount of material (dust and volatiles) injected into the stratosphere by these three events differed greatly. Large amounts of fine ash and volatiles were dispersed into the upper atmosphere by Krakatau and Tambora; the Agung eruption in 1963 was a much smaller, vulcanian-type eruption which injected dust and volatiles into the stratospheric aerosol layer more directly. Analyses of magmatic volatiles indicate that the Agung eruption was proportionately richer in SO2 and Cl than either Tambora or Krakatau. Relative amounts of fine ash produced by the Tambora, Krakatau, and Agung eruptions are estimated at about 150:20:1, whereas the masses of atmospheric sulfate aerosols produced were on the order of 7.5:3:1.

Decreases in surface temperature of a few tenths of a degree C for several years following volcanic eruptions are primarily a result of the sulfate aerosols, rather than of the silicate dust. The similarity in the atmospheric response after these three eruptions supports the idea of limiting mechanisms on volcanic stratospheric-aerosol loading, which is suggested by microphysical processes of aerosol particles. Fluctuations in stratospheric aerosol optical depth seem to be controlled to a large degree by high-intensity sulfur-rich eruptions (e.g., Agung, 1963), which may however be relatively small in total ejecta volume. Such eruptions leave little geologic record, but appear as acidity peaks in polar ice cores.
Recent Seasonal Rainfall and Temperature Relationships in Peninsular Florida
Authors: Coleman James M.
Published: December 2004

Rainfall and temperature records for the last half century are analyzed for peninsular Florida. A recent increase in winter precipitation, weakening toward the south, appears to be related to the temperature decline of the last several decades. Autumn decrease in precipitation in the last two decades is apparently due to suppression of tropical cyclonic activity. The reverse of both of these trends was evident prior to the 1940s. These climatic patterns have resulted in seasonal redistribution of precipitation throughout the Florida peninsula and extended drought conditions for the southern half of the peninsula.
Comparisons of210Pb and Pollen Methods for Determining Rates of Estuarine Sediment Accumulation
Authors: Brush Grace S. , Martin E. Ann , DeFries Ruth S. , Rice Cynthia A.
Published: December 2004

Comparisons of sedimentation rates obtained by210Pb and pollen analyses of 1-m cores collected throughout the Potomac Estuary show good agreement in the majority of cores that can be analyzed by both methods. Most of the discrepancy between the methods can be explained by the analytical precision of the210Pb method and by the exactness with which time horizons can be identified and dated for the pollen method. X-radiographs of the cores and the distinctness of the pollen horizons preclude significant displacement by reworking and/or mixing of sediments. Differences between the methods are greatest where uncertainties exist in assigning a rate by one or both methods (i.e.,210Pb trends and/or “possible” horizon assignments). Both methods show the same relative rates, with greater sediment accumulation more common in the upper and middle estuary and less toward the mouth. The results indicate that geochronologic studies of estuarine sediments should be preceded by careful observation of sedimentary structures, preferably by X-radiography, to evaluate the extent of mixing of the sediments. Time horizons, whether paleontologic or isotopic, are generally blurred where mixing has occurred, precluding precise identification. Whenever possible, two methods should be used for dating sediments because a rate, albeit erroneous, can be obtained isotopically in sediments that are mixed; accurate sedimentation rates are also difficult to determine where the time boundary is a zone rather than a horizon, where the historical record does not provide a precise date for the pollen horizon, or where scouring has removed some of the sediment above a dated pollen horizon.
The Overkill Hypothesis as a Plausible Explanation for the Extinctions of Late Wisconsin Megafauna
Authors: Spaulding W. Geoffrey
Published: December 2004

The pulse of large mammal extinctions at the close of the last ice age was a pronounced ecological catastrophe in the Western Hemisphere. Available paleoenvironmental, paleontological, and archeological data are largely concordant with the “overkill” hypothesis proposing that human predation was the cause of these extinctions. Climatic explanations fail to postulate specific mechanisms accounting for the event's timing, differential impact, geographic extent, and stratigraphic singularity. Lack of provisional acceptance of the overkill hypothesis, when no viable alternatives exist, may be in part because this unconventional hypothesis violates a strong sociocultural bias, the image of prehistoric man as the “noble savage”.
Paleoecology of an Early Holocene Faunal and Floral Assemblage from the Dows Local Biota of North-Central Iowa
Authors: Hudak Curtis M.
Published: December 2004

The faunas and floras from the Dows Local Biota provide an opportunity to compare Holocene taxa without a cultural bias. The Dows Local Biota is located in a large depression on the back side (north) of the Altamont I Moraine complex within the Des Moines Lobe. The Dows Silt Fauna/Flora ( = DSF; ca. 9380 ± 130 yr B.P.), one horizon of the Dows Local Biota, was collected for plant macrofossils, mollusks, and micromammals. DSF terrestrial gastropods are upland mesic forest dwellers although one species, Strobilops affinis, is characteristic of more xeric forests and may represent open woods. The aquatic gastropods reflect both permanent and periodic waters. DSF micromammals prefer an open, mesic, deciduous forest. The micromammal sympatry is restricted to a small area within the tension zone and deciduous forest belt of west-central Wisconsin. DSF plants are characteristic of upland forests, moist meadowlands or disturbed areas, and aquatic habitats. The DSF plant sympatry is large but restricted to the conifer-hardwood and deciduous forests along the Great Lakes-New England regions. Quantitative climatic data for the combined DSF sympatries suggest that Dows (ca. 9380 yr B.P.) was cooler than at present, and is nearly identical to that achieved by pollen analyses at the Cherokee Sewer-Lake West Okoboji sites (ca. 9000 yr B.P.) in northwest Iowa. Based on common habitat interpretations and sympatries, about 9380 yr B.P. north-central Iowa was cooler and moister than at present and was occupied by an open deciduous forest.
Fossil Mammoths from Santa Cruz Island, California
Authors: Cushing John , Daily Marla , Noble Elmer , Roth V. Louise , Wenner Adrian
Published: December 2004

Mammoth remains on Santa Cruz Island, one of the four Northern Channel Islands of California, are very sparse, in marked contrast to those reported from Santa Rosa and San Miguel Islands of the same island group. A probable major reason for this scarcity is that Quaternary deposits are greatly restricted on Santa Cruz Island. It is proposed, contrary to popular opinion, that fossils found on Santa Cruz Island were derived from animals which died on the island, and were not transported there by humans. Reasons for this conclusion are that the size and geological context of the fossils are similar to those of the largest mammoth fossils of Santa Rosa Island, and that, in spite of extensive investigations by many persons, mammoth remains have not been found in middens, either on the islands or on the adjacent mainland.
New Faunal and Isotopic Evidence on the Late Weichselian—Holocene Oceanographic Changes in the Norwegian Sea
Authors: Sejrup Hans Petter , Jansen Eystein , Erlenkeuser Helmut , Holtedahl Hans
Published: December 2004

Downcore studies of planktonic and benthonic foraminifera and δ18O and δ13C in the planktonic foraminifer Neogloboquadrina pachyderma (sin.) in two piston cores from the southern part of the Norwegian Sea suggest large changes in the oceanic circulation pattern at the end of oxygenisotope stage 2 and in the early part of stage 1. Prior to oxygen-isotope Termination IA (16,000–13,000 yr B.P.), an isolated watermass with lower oxygen content and temperature warmer than today existed below a low salinity ice-covered surface layer in the Norwegian Sea. Close to Termination IA, well-oxygenated deep water, probably with positive temperatures, was introduced. This deep water, which must have had physical and/or chemical parameters different from those of present deep water in the Norwegian Sea, could have been introduced from the North Atlantic or been formed within the basin by another mechanism than that which forms the present deep water of the Norwegian Sea. A seasonal ice cover in the southern part of the Norwegian Sea is proposed for the period between Termination IA and the beginning of IB (close to 10,000 yr B.P.). The present situation, with strong influx of warm Atlantic surface-water and deep-water formation by surface cooling, was established at Termination IB.
Quaternary Fluctuations in the Northern Hemisphere Trade Winds and Westerlies
Authors: Janecek Thomas R. , Rea David K.
Published: December 2004

The mass accumulation rate and grain size of the total colian component isolated from pelagic sediment in two North Pacific cores, piston core KK75-02 under the prevailing westerlies and Deep-Sea Drilling Project Site 503 beneath the trade winds, have been used to evaluate changes in the intensity of atmospheric circulation and source-area aridity over the past 700,000 yr. The eolian grain size, a direct indicator of wind intensity, fluctuates at periodicities similar to those calculated for the earth's orbital parameters of precession, obliquity, and eccentricity. Both sites display greater variability in wind intensity prior to 250,000 yr ago. Eolian accumulation rates, an indicator of source-area aridity, fluctuate at periodicities similar to those of the glacial-interglacial cycles. Lower eolian accumulation rates during colder (glacial) times most likely reflect increased glacial-age humidity at central Asian and Central American source areas.
Paleoclimatic Implications of U-Series Dates for Lake Sediments and Travertines in the Arava Rift Valley, Israel
Authors: Livnat A. , Kronfeld J.
Published: December 2004

The Sayif travertines and lacustrine limestones cropping out in the northern Arava Valley, a region of extreme aridity, have been dated by the 230Th/234U disequilibrium method. The consistency between the stratigraphic position and the apparent ages at each of the sampling sites strongly supports the reliability of the ages. Most of the ages fall within two clusters that are coincident with ages representative of oceanic oxygen-isotope stages 5 and 7. The colder intervening stage 6 was not a period of substantial travertine formation. During the warmer global episodes of isotopic stages 5 and 7 the arid south of Israel apparently was considerably wetter than at present.
Near East Paleomagnetic Secular Variation Recorded in Sediments from the Sea of Galilee (Lake Kinneret)
Authors: Thompson R. , Turner G. M. , Stiller M. , Kaufman A.
Published: December 2004

Paleomagnetic records of declination and inclination from sediments recovered from the bed of Lake Kinneret (32.4°N, 35.7°E) have been dated by radiocarbon techniques. The sediments span the last 5000 yr. The changes in inclination down the sediment cores are more pronounced than the declination fluctuations and are repeatable between the three coring sites, which are several kilometers apart. Magnetic susceptibility logs display 13 maxima in the 5-m-long sequences, with a pronounced susceptibility minimum about 1000 yr B.P. Many of the susceptibility maxima and minima can be easily correlated between coring sites and are shown to be dominantly related to changes in sediment carbonate content. The natural remanent magnetization intensity follows a similar pattern to that of susceptibility, and the natural remanence of the Kinneret sediments is presumed to reside in detrital magnetite grains carried into the lake by the river Jordan from the basalt-rich bedrock of the rift floor and the Golan Heights. The 14C chronology is strongly supported by a pollen study in which pronounced changes in the proportion of olive pollen were interpreted as being due to extensive cultivation of olives around Galilee in the Hellenistic and Byzantine periods. The Kinneret paleosecular variation records, if accurately dated, point to a complex spatial pattern of Holocene secular variation with significant variations over distances as small as 1000–2000 km.
Changes in the Content and Composition of Pedogenic Iron Oxyhydroxides in a Chronosequence of Soils in Southern California
Authors: McFadden Leslie D. , Hendricks David M.
Published: December 2004

Studies of the pedogenic iron oxyhydroxides in suites of latest Holocene to middle Pleistocene soils formed on fluvial deposits of the transverse ranges, southern California, indicate that the content and composition of iron oxyhydroxide change in a systematic manner. Analysis of total secondary free iron oxides (dithionite extractable, Fe2O3d) and ferrihydrite (oxalate extractable, Fe2O3o) shows that (1) a single-logarithmic model (Y = a + b log X) or double logarithmic model (log Y = a + b log X), where Y is the total mass of pedogenic Fe oxides (g/cm2-soil column) and X is soil age, describes the rate of increase in Fe2O3d with time; (2) the Fe2O3d content correlates linearly with soil reddening and clay content; (3) the Fe2O3oFe2O3d ratio, which indicates the degree of Fe oxide crystallinity, is moderately high to very high (0.22–0.58) in middle Holocene to latest Pleistocene soils and progressively decreases to less than 0.10 in older soils; (4) the value of the Fe2O3oFe2O3d ratio also appears to be infuenced by climate; and (5) temporal changes in Fe oxide content and mineralogy are accompanied by related, systematic changes in clay mineralogy and organic matter content. These relationships are attributed to a soil environment that must initially favor ferrihydrite precipitation and/or organic matter-Fe complexation. Subsequent transformation to hematite causes increasingly intense reddening and a concomitant decrease in the Fe2O3oFe2O3d ratio. The results demonstrate that iron oxide analysis is useful for numerical age studies of noncalcic soils and shows potential as an indicator of paleoclimates.
Glaciations of the West Coast Range, Tasmania
Authors: Colhoun Eric A.
Published: December 2004

Geomorphic, stratigraphic, palynologic and14C evidence indicates that the West Coast Range, Tasmania, was glaciated at least three times during the late Cenozoic. The last or Margaret Glaciation commenced after 30,000 yr B.P., culminated about 19,000 yr B.P., and ended by 10,000 yr B.P. During this period a small ice cap, ca. 250 m thick, and cirque and valley glaciers covered 108 km2. The glacial deposits show little chemical weathering or erosional dissection. The snow line ranged from 690 to 1000 m with an average of 830 m for the ice cap. Mean temperature was 6.5°C below the present temperature. During the preceding Henty Glaciation a 300- to 400-m-thick ice cap and outlet glaciers exceeded 1000 km2. The glacial deposits are beyond14C assay. They are more weathered chemically and more dissected than Margaret age deposits, and the degree suggests a pre-last interglaciation age (> 130,000 yr B.P.). The snow line of the ice cap lay at 740 m, and annual temperature was reduced by 7°C. Ice of the earliest Linda Glaciation slightly exceeded that of the Henty Glaciation but had a similar distribution. The glacial deposits are intensely weathered, have reversed magnetization, and overlie a paleosol containing pollen of Tertiary type. An early Pleistocene or Tertiary age is indicated.
Wolverine in Northern England at About 83,000 yr B.P.: Faunal Evidence for Climatic Change during Isotope Stage 5
Authors: Sutcliffe Antony J. , Lord Thomas C. , Harmon Russell S. , Ivanovich Miro , Rae Angela , Hess John W.
Published: December 2004

Cave sediments from Stump Cross Cave in northern England contain Pleistocene mammal remains. Uranium-series dating of calcium carbonate deposits closely associated with the fossiliferous horizons has established an absolute age of 83,000 ± 6000 yr B.P. for a faunal assemblage largely comprised of wolverines (Gulo gulo). This date lies firmly within the younger portion of oxygen-isotope stage 5. The occurrence of wolverines in the vicinity of Stump Cross Cave at ca. 83,000 yr B.P. indicates a significant climatic deterioration from ca. 120,000 yr B.P., when an Ipswichian interglacial fauna with hippopotamus was present in this part of northern England.
14C and Th/U Dating of Pleistocene and Holocene Stromatolites from East African Paleolakes
Authors: Hillaire-Marcel Claude , Carro Odette , Casanova Joel
Published: December 2004

During recent humid episodes, stromatolites were built along paleolake margins, some 60 m above the modern water level of Lakes Natron and Magadi (southern Gregory Rift Valley). Three generations of stromatolites are observed, the more recent ones frequently covering pebbles and boulders eroded from the older ones. The youngest one yielded 14C ages ranging from approximately 12,000 to 10,000 yr B.P. Their δ13C values (≥2.6%) suggest isotopic equilibrium between the paleolake total inorganic dissolved carbon and the atmospheric CO2, thereby lending credence to the reliability of the 14C. An initial 230Th/232Th ratio in the detrital component was determined by Th/U measurements on the 14C dated stromatolites. Using this value a 230Th/234U chronology for the older stromatolites was calculated. Ages of ≥240,000 and 135,000 ± 10,000 yr were obtained for the first and second generations, respectively. A humid episode apparently characterized eastern Africa during each glacial-interglacial transition. 18O and 13C measurements on stromatolites, when compared to values on modern waters and carbonates, provide paleohydrological information. Long residence time of the paleolake waters and less seasonally contrasted regimes are inferred.
Electron Spin Resonance Dating of the Pleistocene Coral Reef Tracts of Barbados
Authors: Radtke Ulrich , Grün Rainer , Schwarcz Henry P.
Published: December 2004

The reef tracts of Barbados have been investigated by electron spin resonance dating; all parameters necessary for ESR dating (including effective α-efficiency and thermal stability) were determined without cross checking with another independent dating method. In addition, some U-series analyses were carried out in order to test the reliability of ESR. In most cases, the results show a satisfactory agreement between ESR and both these and previously published U-series dates (M. L. Bender, R. G. Fairbanks, F. W. Taylor, R. K. Matthews, J. G. Goddard, and W. S. Broecker (1979). Geological Society of America. Bulletin 90 , 577–594). For the oldest samples, ESR dates tend to exceed He/U dates, suggesting that there might have been He loss from aragonite. Raised reef tracts are assigned to high sea stands from successive interglacial stages 5, 7, 9, 11, 13, and 15. ESR and U-series (230Th/234U) dates for corals and molluses in North Barbados do not support the suggestion of N. P. James ((1971). Unpublished Thesis, McGill University, Montreal) that this region has subsided during part of the past 125,000 yr. Whereas the experimentally determined mean life (τ) of trapped electrons is only 500,000 yr for the ambient temperature in Barbados, there is no evidence from the comparison between ESR and other dates for thermal fading. This emphasizes the difficulty of experimental measurement of τ.
Late Wisconsin Groundwater Discharge Environments of the Southwestern Indian Springs Valley, Southern Nevada
Authors: Quade Jay , Pratt William L.
Published: December 2004

Badland exposures in the Indian Springs Valley, southern Nevada, contain evidence of formerly widespread spring and seep discharge. The stratigraphic position and appearance of most of these deposits suggests correlation with late Wisconsin (30,000 to ca. 10,000 yr B.P.) marsh sediments in nearby Las Vegas Valley. Previously, all these deposits have been loosely described as lacustrine because of the presence of extensive green mudstones associated with aquatic mollusks. However, this association also typifies modern groundwater discharge environments in many basins of northeast Nevada such as the Steptoe Valley, basins often without hydrographic closure. Such analogs best explain the origin of late Wisconsin fine-grained deposits in the unclosed southwestern arm of the Indian Springs Valley. Key features of these depositional systems are the lack of shoreline deposits, the presence of a broad belt of subaerially deposited plae-brown silts surrounding spring, “wet meadow,” and marsh deposits, and the intermixture of terrestrial and aquatic mollusks in most horizons where mollusks occur.
Absence of Altonian Glaciation in Illinois
Authors: Curry B. Brandon
Published: December 2004

Illinois was free of glacier ice from about 130,000 to 25,000 yr B.P. Deposits of this time interval in northeastern Illinois, represented by core samples from test-hole ISGS S-30, are composed of leached, nonglacigenic, stratified, or pedoturbated silty sediments that typically are organic-rich and pedogenically modified. These deposits overlie the Sangamon Soil, which is identified by its stratigraphic position, soil morphology, and distinct alteration products in the clay-mineral fraction, including a variably swelling vermiculite-like phase and a randomly interstratified kaolinite/10 Å phase. The regional extent of these deposits suggests that if Altonian ice existed in the Lake Michigan basin, it did not extend westward beyond the cuesta of Silurian dolomite that rims the southwestern shore of Lake Michigan.
Vegetation Response to Climatic Change in Central Rift Valley, Kenya
Authors: Mworia Maitima Joseph
Published: December 2004

Pollen analysis of a 15.5-m sediment core from Lake Naivasha, central Rift Valley of Kenya, reveals that the vegetation from before 20,290 to nearly 12,000 yr B.P. was dominated by open grassland, indicating arid conditions. Within this period a moderately wetter climate existed between 17,000 and 15,000 yr B.P., shown by relatively slight increase in both the montane and lowland forest vegetation. From approximately 12,000 to 6500 yr B.P., a change toward more trees and forests started at lower altitudes around the basin of Lake Naivasha, and later in the higher montane regions. After 6000 yr B.P. a decline in forest and lowland trees opened the vegetation into more grasslands and by 4000 yr B.P. a vegetation similar to the present was attained and has persisted to the present. During this period shallow-water aquatic plants became abundant in Lake Naivasha.
Climatic, Solar, Oceanic, and Geomagnetic Influences on Late-Glacial and Holocene Atmospheric 14C/12C Change
Authors: Stuiver Minze , Braziunas Thomas F. , Becker Bernd , Kromer Bernd
Published: December 2004

Late-glacial and Holocene 14C/12C ratios of atmospheric CO2 vary in magnitude from a few per mil for annual/decadal pertubations to more than 10% for events lasting millennia. A data set illuminating 10- to 104-yr variability refines our understanding of oceanic (climatic) versus geomagnetic or solar forcing of atmospheric 14C/12C ratios. Most of the variance in the Holocene atmospheric 14C/12C record can be attributed to the geomagnetic (millennia time scale) and solar (century time scale) influence on the flux of primary cosmic rays entering the atmosphere. Attributing the observed atmospheric 14C/12C changes to climate alone leads to ocean circulation and/or global wind speed changes incompatible with proxy records. Climate-(ocean-)related 14C redistribution between carbon reservoirs, while evidently playing a minor role during the Holocene, may have perturbed atmospheric 14C/12C ratios measurably during the late-glacial Younger Dryas event. First-order corrections to the radiocarbon time scale (12,000–30,000 14C yr B.P.) are calculated from adjusted lake-sediment and tree-ring records and from geomagnetically defined model 14C histories. Paleosunspot numbers (100–9700 cal yr B.P.) are derived from the relationship of model 14C production rates to sunspot observations. The spectral interpretation of the 14C/12C atmospheric record favors higher than average solar activity levels for the next century. Minimal evidence was found for a sun-weather relationship.
Interglacial Deposits at Birch Creek, Northeast Interior Alaska
Authors: Edwards Mary E. , McDowell Patricia F.
Published: December 2004

A 12-m sequence of lake sediment and peat in a 45-m high exposure on Birch Creek, northeast Alaska, contains pollen of Picea, Betula, Alnus and Populus, and wood of Picea and Populus. This sequence, which may represent 10,000 yr of more of accumulation, is beyond the limit of radiocarbon dating. It lies between two units of loess; the underlying loess lies above the Old Crow Tephra, recently dated at 149,000 ± 13,000 yr B.P. The lake sediments probably were deposited during the last interglaciation (isotope substage 5e) and subsequently buried by Wisconsinan loess. Analogs for the ancient lake may be deep, long-lived thaw lakes that are present in the modern landscape. When Birch Creek is correlated with other sites across nonglaciated Alaska and northwest Canada, there appears to be a common interglacial signal in sediments overlying the Old Crow Tephra.
Bias, innateness and domain specificity
Authors: KIRBY SIMON
Published: December 2004

For over 35 years, beliefs about the learnability of natural language have acted as roadblocks in the way of further development in linguistics. Rigorous and useful formal work has led to the unwarranted adoption of extreme positions which in turn have tended to stifle collaboration and polarize debate. In his article, MacWhinney suggests a way around such roadblocks – or rather many ways around. He demonstrates that we should look for multiple mechanisms to help understand how it is that children learn language from the evidence to which they are exposed.
Clarifying the logical problem of language acquisition
Authors: PINKER STEVEN
Published: December 2004

MacWhinney is to be commended for reopening questions about the logical problem of language acquisition in the light of new data and models. Unfortunately his discussion is marred by technical errors, false dichotomies, and inadequate attention to detail.
Learnability, stochastic input, and connectionist networks: a response to Brian MacWhinney's ‘A multiple process solution to the logical problem of language acquisition’
Authors: ROHDE DOUGLAS L. T.
Published: December 2004

I would like to begin by clarifying some technical points regarding learnability and Gold's theorem and will work my way around to advocating the power of distributed connectionist networks. I may wind up repeating much of what MacWhinney has already said, but I hope to do so in a manner that clarifies the status of and relationship between his seven solutions to the language acquisition problem.
Expressing communicative intents in Estonian, Finnish, and Swedish mother–adolescent interactions
Authors: TULVISTE TIIA , MIZERA LUULE , DE GEER BOEL
Published: December 2004

The present article focused on two types of communicative intent (directing behaviour vs. eliciting talk) expressed by mothers and teenagers during everyday family interactions in Estonian, Finnish, and Swedish mono- and bicultural families. Three monocultural groups consisted of 17 Estonian, 19 Swedish, and 18 Finnish families living in their country of origin; two bicultural and bilingual groups consisted of 18 Estonian and 18 Finnish families residing in Sweden. All the children were between 9;0 and 13;0. The results revealed that the Estonian monocultural mothers were highly directive and direct: issuing behavioural directives most frequently and using the highest proportion of imperatives among all samples. Contrary to our expectations, the mothers who tended to be more concerned with controlling their children's behaviour also elicited conversation more frequently from teenagers by using a larger number of information requests. These requests seemed to serve as another form of attempted control over adolescents' behaviour – their communicative behaviour. The Swedish monocultural children were more active in controlling their mothers' behaviour than their counterparts, possibly illustrating the Swedish value of generational equality.
Vocabulary competence in first- and secondborn siblings of the same chronological age
Authors: BORNSTEIN MARC H. , LEACH DIANE B. , MAURICE HAYNES O.
Published: December 2004

We explored vocabulary competence in 55 firstborn and secondborn sibling pairs when each child reached 1;8 using multiple measures of maternal report, child speech, and experimenter assessment. Measures from each of the three sources were interrelated. Firstborns' vocabulary competence exceeded secondborns' only in maternal reports, not in child speech or in experimenter assessments. Firstborn girls outperformed boys on all vocabulary competence measures, and secondborn girls outperformed boys on most measures. Vocabulary competence was independent of the gender composition and, generally, of the age difference in sibling pairs. Vocabulary competence in firstborns and secondborns was only weakly related.
Intonation development from five to thirteen
Authors: WELLS BILL , PEPPÉ SUE , GOULANDRIS NATA
Published: December 2004

Research undertaken to date suggests that important developments in the understanding and use of intonation may take place after the age of 5;0. The present study aims to provide a more comprehensive account of these developments. A specially designed battery of prosodic tasks was administered to four groups of thirty children, from London (U.K.), with mean ages of 5;6, 8;7, 10;10 and 13;9. The tasks tap comprehension and production of functional aspects of intonation, in four communicative areas: CHUNKING (i.e. prosodic phrasing), AFFECT, INTERACTION and FOCUS. Results indicate that there is considerable variability among children within each age band on most tasks. The ability to produce intonation functionally is largely established in five-year-olds, though some specific functional contrasts are not mastered until C.A. 8;7. Aspects of intonation comprehension continue to develop up to C.A. 10;10, correlating with measures of expressive and receptive language development.
Characterizing changes in parent labelling and gesturing and their relation to early communicative development
Authors: NAMY LAURA L. , NOLAN SUSAN A.
Published: December 2004

In a longitudinal study, 17 parent–child dyads were observed during free-play when the children were 1;0, 1;6, and 2;0. Parents' labelling input in the verbal and gestural modalities was coded at each session, and parents completed a vocabulary checklist for their children at each visit. We analysed how the frequency of labelling in the verbal and gestural modalities changed across observation points and how changes in parental input related to children's vocabulary development. As a group, parents' verbal labelling remained constant across sessions, but gestural labelling declined at 2;0. However, there are notable individual differences in parental trajectories in both modalities. Parents whose verbal labelling frequency increased over time had children whose vocabulary grew more slowly than those whose labelling frequency decreased, remained constant, or peaked at 1;6. There were few systematic relations between patterns of parental gesturing and children's vocabulary development. Parents' verbal and gestural labelling patterns also appeared dissociable. However, parents' words and gestures were correlated when their children were 1;6, suggesting that gestures serve an important bootstrapping function at a critical point in children's vocabulary development.
Perception of utterance relatedness during the first-word-period
Authors: BALOG HEATHER L. , ROBERTS FELICIA D.
Published: December 2004

Interactions between six toddlers (aged 1;0 to 1;6) and adults were examined to ascertain adult perceptions of toddler utterance relatedness and to determine temporal and interactional features that underlie those perceptions. Five raters made judgments regarding relatedness of the child utterances to the previous adult utterances; 251 utterances were examined. Utterances judged by adults as related occurred within 4·25 seconds of the preceding adult utterance nearly 90% of the time. This study also points to the need for using interactional categories that go beyond describing utterance relatedness, and introduces terms (i.e. co-participatory, initiation, narrowed focus) for doing so.
Editorial
Authors: LIEVEN ELENA
Published: December 2004

Ann Peters and Dan Dinnsen are leaving our editorial team. Ann Peters has served as an Associate Editor for 8 years and Dan Dinnsen for 5 years. In both cases, their contribution to the Journal has been invaluable and on behalf of the Editorial Team, of those who submit papers to the Journal and of those who read it, I would like to thank them for their collegiality and for all their extremely careful and hard work.