bluuebunny/crossref_metadata_2025 huggingface dataset:
Geochemical and Petrological Characterization of Ash Samples from Cascade Range Volcanoes
Authors: Randle Keith , Goles Gordon G. , Kittleman Laurence R.
Published: December 2004

Twenty-nine samples of volcanic ash from the Pacific Northwest were analyzed by instrumental neutron activation techniques, with the aim of distinguishing among ashes from different sources. Preliminary results of petrographic studies of 42 ash or pumice samples are also reported. Geochemical characteristics of Mazama ash are defined, and problems induced by winnowing of crystalline material during transport and by weathering are discussed. Contents of La, Th, and Co, and La/Yb ratios are shown to be good discriminants. Data on refractive indices and on proportions of crystalline materials also aid in distinguishing among the various volcanic ashes studied. Ash and pumice found in archaeological contexts at Fort Rock Cave, Paisley Cave, Wildcat Canyon, and Hobo Cave are all from Mount Mazama, presumably from the culminating cruption of 7000 years ago.
Pollen Grains in Lake Sediments: Pollen Percentages in Surface Sediments from Southern Michigan
Authors: Davis M. B. , Brubaker L. B. , Beiswenger J. M.
Published: December 2004

Pollen in surface sediments from five lakes in southern Michigan shows evidence of differential deposition. In most lakes, pollen from ragweed occurs in a higher ratio to tree pollen in shallow-water sediment than in deep water. Pine and certain herbs with small pollen grains follow the same pattern. One very deep lake is an exception, with the ratio of ragweed to tree pollen highest in deep-water sediment. Pollen from local aquatics and from willow, which grows along the lake shore, is also unevenly distributed, occurring in highest frequencies near the parent plants. Pollen from deciduous trees, however, occurs in similar ratios at all sampling stations within each lake. Deciduous pollen occurs in uniform ratios, also in older sediment, deposited in the early 19th century, when the landscape was still forested.

Percentages of deciduous tree pollen (as percent tree pollen) were compared among lakes. Single samples were taken for this purpose from the deepest part of each lake basin. Oak pollen percentages are higher in three lakes in western Washtenaw County than in three lakes in eastern Washtenaw County. This difference reflects a similar difference in present-day vegetation: second-growth oak forests grow near the lakes in the western half of the county, while all but 5% of the area in the eastern part of the county is farmland. (The difference in the ratio of farmland to forestland in the two parts of the county is not reflected clearly in the ratio of herb pollen to tree pollen, because there is so much variation within each lake.) In 140-year-old sediment, on the other hand, tree pollen percentages in the six samples are homogeneous as shown by a chi-square test. The homogeneity in sediment deposited before the forest was cleared is surprising, because witness-tree data from presettlement time show that the frequencies of tree species in the two areas were quite different. Pollen dispersal at that time must have been effective enough, to counteract differences over distances of a few tens of kilometers in the amounts and kinds of pollen produced by the vegetation.
Late-Quaternary Vegetation and Climate Near the Arctic Tree Line of Northwestern North America
Authors: Ritchie J.C. , Hare F.K.
Published: December 2004

Earlier studies in Alaska and northwest Canada have shown inconsistent evidence for the expected northward extension of the Arctic tree line during the Hypsithermal Interval. Only megafossil evidence has supported this suggestion; the palynological findings have been inconclusive. The Tuktoyaktuk Peninsula, in the Northwest Territories of Canada, offers critical sites for studies of late-Pleistocene ecology, because of its geological, biotic, and climatological features. Palynological and megafossil evidence is presented from sites on the Tuktoyaktuk Peninsula, indicating northward advance of the Arctic tree line during the period 8500-5500 B.P. Relative pollen frequencies of a core of lake sediment suggest a late-Pleistocene sequence as follows: 12,900-11,600 dwarf birch tundra; 11600-8500 forest tundra; 8500-5500 closed-crown spruce-birch forest; 5500-4000 tall shrub tundra; 4000-present dwarf birch heath tundra. These results suggest that during the Hypsithermal Interval the Arctic Front (July position) was further north, over the Beaufort Sea, a displacement from its present position of about 350 km. The Tuktoyaktuk Peninsula, presently occupied by tundra, and dominated by the Arctic airstream in July, was apparently under forest, with warm, moist Pacific air during the Hypsithermal Interval.
Quaternary Research in France
Authors: Alimen H.
Published: December 2004

Between the two wars, studies on the Quaternary were scarcely in favor in France. However. from the beginning of the 19th century recent terrains had held the attention of our country’s eminent geologists, and later that of the prehistorians, and starting in the 1850s these terrains were given the first chronological classifications based, on the one hand, on the evolution of Mammals. and on the other hand, on the succession of prehistoric civilizations.
Pleistocene Terraces of the Alto Henares (Guadalajara), Spain
Authors: Gladfelter Bruce G.
Published: December 2004

A suite of four terraces in the upper Rio Henares drainage system (Rio Tajo basin) now provides a partial geomorphological link between the Middle Pleistocene, Lower Paleolithic archeological sites at Ambrona and Torralba (upper Ebro basin) and those in the vicinity of Madrid. The Campiña and Low Terrace features are shown by radiocarbon dating to be of Holocene and Würm ages, respectively, while the Middle and High Terraces are best designated as being Middle and Lower Pleistocene ages, respectively. Stratigraphic relationships between the upper and lower Rio Henares segments need to be established.
Carbon-14 Dates from the Snowy Mountains area, Southeastern Australia, and their Interpretation
Authors: Costin A.B.
Published: December 2004

Carbon-14 dates for fossil wood, peats, and organic soils from periglacial and glucial sites between 1100 and 2100 m in the Snowy Mountains area, southeastern Australia, are interpreted in relation to the site characteristics and the present climate. The dates indicate a widespread cold period commencing about 34,000-31,000 years ago, the effects of which apparently continued until about 15,000 and locally until about 9000 years ago; a subsequent warmer period; and a colder phase about 3000-1500 years ago. Mean annual temperatures during the first cold period are estimated to have been at least 8–10°C lower than at present, and at least 3°C lower during the cold phase of 3000-1500 years ago.
Glacio-Periglacial Landforms within the Susquehanna Great Bend Area of New York and Pennsylvania
Authors: King Cuchlaine A.M. , Coates Donald R.
Published: December 2004

Previous attention has been called to the morphology of the glaciated Appalachian Plateau, including periglacial phenomena (Coates, 1970; Conners, 1969). This paper deals with an unusually well-developed hierarchy of small landforms in the Great Bend area of the Susquehanna River. Essential properties of these features include: (1) concentration in N-S valleys, (2) till composition, (3) concavo-convex form, sometimes ending in a hill on the valley floor, (4) alternation with steep, truncated bedrock spurs, (5) a col in the interfluve at their head. These characteristics could be explained by the following sequence of events. A prior fluvial landscape was eroded with tributary streams forming lateral valleys that head in cols along the divides. The main stream flowed south between interlocking spurs. Ice then widened the valley, leaving truncated spurs and a straightened stream. Deposition of locally derived till filled tributary valleys, similar to till shadows (Coates, 1966). In periglacial conditions, while nivation was widening the tributary valley heads, solifluction in the unstable till was forming the concavo-convexities that alternate with the truncated bedrock spurs. The hierarchy of forms range from minor convexities to small hills on the main valley floor. Thus, the features are primarily of periglacial origin, but owe their development and position to prior subaerial and glacial events. The cycle may have occurred during more than a single glacial episode. The recession of bedrock spurs and the valley floor convexity of the till features have caused a reversal in stream sinuosity of the main valley.
Pleistocene Chronology: Long or Short?
Authors: Cooke H.B.S.
Published: December 2004

European geologists, in general, have tended to favor a “short” chronology for the glacial Pleistocene, with four major glacial cycles in the past 500,000 or 600,000 yr. Interpretation of ocean floor sediments by Emiliani and others has accorded with this view, in contrast to the “long” chronology of Ericson and Wollin and their followers, who spread the four North American glacial episodes over a 2-m.y. period. An examination of the available radiometric dates and age estimates from paleomagnetic polarity zones serves to confirm Richmond's view that the four major European glacials do not equate with the four North American glacials in a simple one-to-one manner, but that the Illinoian matches the Elster (Mindel) rather than the Saale (Riss). The Alpine Günz is then equated broadly with the Kansan and overlaps in time with the Jaramillo normal polarity event at about 900,000 y.a. The Nebraskan is older than 1.2 m.y. and is thus coeval with the European Upper Villafranchian, within which the Donau and Biber glacial events may be traced. Montane glaciation certainly extended back into the Tertiary but cold pulses of sufficient duration to produce continental glaciation were more marked through the past 1.5 m.y. More critical studies of the terrestrial record are needed before firm correlations can be made.
Late-Quaternary Sea Level Changes, Umnak Island, Aleutians—Their Effects on Ancient Aleuts and their Causes
Authors: Black Robert F.
Published: December 2004

Late-Quaternary sea level changes in the eastern Aleutian Islands are of paramount importance in the reconstruction of the migrations and environment of the ancient Aleuts. A radiocarbon-dated ash stratigraphy provides the chronology into which geomorphic events can be fitted. These provide evidence for the sea level changes. Deployment of beach material and coastal configuration intimate that sea level was about 2–3 m above the present level about 8250 radiocarbon yr BP. Beach deposits suggest that sea level remained high until about 3000 radiocarbon y.a. when it gradually dropped to its present position. It is concluded that the ancient Aleuts that settled Anangula about 8400 y.a. used boats; all major passes in the eastern Aleutians were flooded, and did not have winter ice. Those ancient Aleuts did not have available the major year-around food resources of the present strandflats as they were cut during the high sea level stand 8250–3000 yr BP. The ancient Aleuts must have been marine oriented, for land-based food resources would have been limited.

The cause of relative sea level changes on Umnak Island is considered indeterminate with present data. Eustatic, glacial isostatic, water isostatic, tectonic, and volcanic causes are considered the main possible controls in combinations such that a basic eustatic sea level curve and likely a glacial-water isostatic curve must be common to any solution. Representative solutions are given to illustrate some of the problems.
The Deglaciation History of the Lake Superior Region and its Climatic Implications
Authors: Saarnisto Matti
Published: December 2004

A zone of synchronous end moraines has been recognized in the Lake Superior region across northern Ontario and Michigan. The moraines were formed between 11,000 and 10,100 y.a. as cold climate resulted in successive halts in the general ice retreat. The cold climate is also indicated by the presence of tundra near Lake Superior until about 10,000 y.a. This episode is here referred to as the Algonquin Stadial. It was preceded and followed by rapid deglaciation. The Algonquin Stadial is comparable in age with the Younger Dryas Stadial of Europe, and indicates a reversal in the continuous trend toward a warmer climate during Late-Wisconsin (an) time. The apparent conflict between the present result (based on geologic evidence) and earlier pollen stratigraphical studies with no reversal is discussed.

Glacial Lake Duluth formed in the western Lake Superior basin before 11,000 BP, followed by a series of Post-Duluth lakes between approximately 11,000 and over 10,100 BP. The Main Lake Algonquin stage in the Huron and Michigan basins terminated approximately 11,000 BP. The subsequent high-level post-Main Algonquin lakes, which were contemporaneous with the Post-Duluth lakes, existed in the southeastern Lake Superior basin. When the ice margin was along the north shore 9500 BP Lake Minong occupied the whole Lake Superior basin. By 9000 BP the ice had retreated north of Lake Superior-Hudson Bay divide.
A Climatic Model of Solar Radiation and Temperature Change
Authors: Reitan Clayton H.
Published: December 2004

Mean monthly temperatures for the Northern Hemisphere were determined for the years 1955 through 1968 following the same procedures used by H. C. Willett and J. M. Mitchell, Jr., in their studies of long-term trends. It was found that the downward trend they reported starting in the 1940s continued, though interrupted, into the 1960s.

The temperature data when combined with radiation data and other components of the hemispheric energy budget led to the formulation of the response ratio, the relationship between change in incoming solar radiation and change in temperature. When this response ratio was applied to the reported trends in direct solar radiation and to the decrease in direct solar radiation following the eruption of Agung in 1963, a probable cause-effect relationship was suggested.
A Study of Late Pleistocene Loess Deposits, South Canterbury, New Zealand Part I. Forms and Amounts of Phosphorus Compared with other Techniques for Identifying Paleosols,
Authors: Runge E.C.A. , Walker T.W. , Howarth D.T.
Published: December 2004

Four paleosols, and soil horizons within paleosols, were clearly identified in the thick calcium carbonate-free loess sections at Timaru, South Island, New Zealand, by changes in the distribution of total phosphorus and calcium phosphate in the upper 2 m to each paleosol. Extractable manganese was also sensitive in identifying paleosols, particularly the upper horizons. The distribution of bulk density values was useful in identifying paleosols; however, the maximum bulk density (>1.7 g/cc) occurred in horizons identified as B2 rather than fragipan horizons in three of four cases. The distribution of clay particles was useful in understanding the genesis of the modern soil and paleosols, but not in identifying paleosols.
Lichenometry on Calcareous Substrates in the Canadian Rockies
Authors: Osborn Gerald , Taylor John
Published: December 2004

Lichen distribution and growth were examined at several sites in the Canadian Rockies between Mt. Robson and Banff townsite to determine the feasibility of lichenometry on calcareous deposits. The only lichen common enough to be of use is Xanthoria elegans, a bright orange lichen with round or elliptical thalli. It is not an ideal species for lichenometry because (a) it grows fairly quickly and has a range of only a few centuries, (b) growth is influenced by the presence of animal dung, (c) parts of some thalli weather away before maximum size is attained, (d) thalli may thicken as well as grow laterally with age, (e) the species is succeeded by other species relatively quickly in heavily forested environments, and (f) the species is not abundant on some deposits due to sometimes-unexplained environmental influences. However, when used with caution the species is still useful for dating purposes.

A growth curve for Xanthoria elegans was developed using moraines dated dendro-chronologically and man-made structures. After an ecesis interval of one or two decades the lichen grows at a rate of 0.68 mm/yr for several decades, then slows down to a rate of 0.22 mm/yr.
Glacial history of Southernmost South America
Authors: Mercer J.H.
Published: December 2004

In southernmost South America, an incomplete radiometrically dated glacial chronology has been obtained by K–Ar dating for the interval 3.5-1 MY ago, and a more detailed chronology by C-14 dating for the last 25,000 years, with some older minimal ages. The first major glaciation was about 3.5 MY ago during the middle Pliocene. Little is yet known about glacial fluctuations during the interval 3.5-2.1 MY ago. Between 2.1 and 1 MY ago many glaciations occurred, probably including the greatest of late Cenozoic time which took place after 1.2 MY and, according to inconclusive evidence, before 1 MY ago. The Patagonian Gravel in its type area is mid-Pliocene to early Pleistocene glacial outwash that accumulated from the first to the greatest glaciations. During the late Pleistocene several glaciations occurred, but only the most recent has been radiometrically dated. During the last glaciation the glaciers were most extensive before 56,000 BP. Successively smaller advances that culminated about 19,500 BP and, probably, about 13,000 BP were separated by an interstade when glaciers shrank by more than half. The glaciers receded rapidly after 13,000 BP and were within their present borders by 11,000 BP; they remained so during the European YoungerDryasStade 11,000-10,000 BP. Neoglacial regional readvances culminated 4600-4200 BP, probably 2700-2000 BP, and during the last three centuries; most glaciers reached their Neoglacial maxima during the first episode. Between readvances, the glaciers shrank within their present borders.
Quaternary Buried Paleosols: A Critical Review
Authors: Valentine K.W.G. , Dalrymple J.B.
Published: December 2004

A review of work on buried paleosols in the disciplines of pedology, Quaternary geology, and archaeology is presented under the headings of (1) the problems of identification, (2) techniques of study, (3) buried paleosols and Quaternary stratigraphy, (4) archaeological stratigraphy and dating, (5) layered soils, and (6) past environment from buried paleosols. It is suggested that future pedological research of interest to Quaternary studies should concentrate on clarifying what is a soil as opposed to a weathered sediment, what processes and features are peculiar to pedogenesis as opposed to diagenesis, and what are the relationships between soil-site conditions and soil characteristics.
Macrofossil Analysis of wood rat (Neotoma) Middens as a Key to the Quaternary Vegetational History of Arid America
Authors: Wells Philip V.
Published: December 2004

Wood rat (Neotoma) deposits preserved in dry rock shelters have radiocarbon ages extending from close to the present to >40,000 BP, thus providing elaborate samples of changing vegetation during the climatic shifts of the late Pleistocene and Holocene. The established record extends geographically from Oregon and Wyoming (at 45°N) south to Baja California, Sonora, and to Tehuacan (at 18°N) in southern Mexico. Several hundred ancient middens have been uncovered, and over 130 have been radiocarbon-dated.

There are about 20 extant species ofNeotomawith a combined range extending from the Yukon and New England to Nicaragua and Florida. Hence, a wider application for the method seems likely, wherever dry caves favor preservation. The acquisitive rats accumulate an incredibly detailed inventory of the local flora and fauna within a small home range, measured at about 100 m or less in radius. The biomass spectrum of a modern wood rat deposit was compared with associated pollen spectra and source vegetation. The most dominant arborescent species, as determined by a quantitative study of the local vegetation, were proportionately represented in the midden, but not in the pollen rain. Less dominant species were variable in proportionality.

A novel approach to the comparative ecological physiology of long-dead plants has been demonstrated with macrofossils from ancient wood rat deposits. The ratio of the stable isotopes of carbon (13C/12C) is more altered from the atmospheric proportion during CO2fixation by C3plants than it is by the different (PEP) carboxylating enzyme of heliophile or xerophytic, C4or CAM plants. Mass spectrometry of the carbon of macrofossils enables the distinction to be made in the past.

The desiccated, allelochemic urine, or amberat, indurates and preserves the middens by cementing the loose debris of macrofossils into a tough, coherent mass of surprising strength and rigidity, that adheres tenaciously to rock surfaces. Water softens the most indurated middens by dissolving the crystallized urine, causing them to dislodge and to fall apart; it also removes the osmotic and allelochemic deterrent to decay by fungi, or to consumption by termites, crickets, or other decomposing herbivores. A secure position in a dry rock shelter is therefore essential to preservation of the macrofossils for time periods on the order of 104years. Attrition with time is seen in the frequency distribution of radiocarbon dates obtained on 132Neotomamiddens. The distribution is skewed toward the end of the Wisconsin glacial and the Holocene, and there is a decline in frequency with age. Cave erosion, including destructive rockfalls and new crevices that admit seepage and cause deterioration and dislodgement of the middens, is probably the main factor in the progressive attrition with increasing age.
Recent Paleolimnology of Three Lakes in Northwestern Minnesota
Authors: Birks Hilary H. , Whiteside M.C. , Stark Donna M. , Bright R.C.
Published: December 2004

A paleolimnological study was undertaken to investigate changes in three Minnesota lakes over the last 100 years and to demonstrate the stratigraphic effects of cultural eutrophication in two of them. The study combined the analysis of the lake sediment from short cores with stratigraphic analyses of pollen, plant macrofossils, mollusks, diatoms and certain other algae, chydorid Cladocera, and Daphnia ephippia.

The rise of Ambrosia type pollen (ragweed) marks the onset of interference with the landscape by European man, which can be closely dated. Calculations of sedimentation rates from this base gave reasonable correlations of other stratigraphic events with historical events.

Elk Lake is considered “unpolluted” today and was chosen as a control. Man's effects are limited to logging some of the surrounding forest and to the construction of a dam. Small changes in the lake's fauna and flora are demonstrated, showing the sensitivity of the lake to changes in its catchment area.

Lake Sallie and St. Clair Lake, in the same watershed as the city of Detroit Lakes, have been affected not only by logging but also by addition of nutrients from agricultural runoff and sewage effluent. Considerable responses by the lake organisms are apparent. In Lake Sallie the changes were gradual, but in St. Clair Lake they were very abrupt because the lake was partially drained at the same time and the water volume was thereby reduced.

The merits of such an integrated study, the types of information gained from the analyses of the various fossils, and the wider application of the results are discussed.
Late Quaternary Climatic Variations in Northwest Africa Deduced from East Atlantic Sediment cores
Authors: Diester-Haass Liselotte
Published: December 2004

Characteristic variations in glacial and interglacial periods are shown by the CaCO3contents, amounts and grain size of terrigenous material (>40 μm), quartz/mica ratios, and desert quartz numbers in East Atlantic sediment cores, collected during Meteor cruise 25 off Sahara and Senegal, 15–27°N. The following results were obtained. DuringHolocenean arid climate with eolian supply from the continent prevailed throughout the region (fine grained, slight terrigenous input; high CaCO3values; high desert quartz numbers) except in the Senegal area. Here terrigenous muds indicate river supply and hence humid climate. During upper and lowerWürnthe climate was humid in the present day Sahara north of 20°N (low desert quartz numbers: input of large quantities of coarse terrigenous material; low CaCO3values). South of 20°N the climate was arid, the Senegal river input disappeared during upperWürm, desert quartz numbers are as high as in Sahara dune samples, and wind strength was stronger than in theHolocene. Climate during middleWürmresembledHoloceneclimatic conditions. Climatic conditions during Eem (Riss) were probably similar to those duringHolocene(Würm).
Quaternary Palynology of the Pacific Slope of Washington
Authors: Heusser Calvin J.
Published: December 2004

Quaternary deposits on the Pacific slope of Washington range in age from the earliest known interglaciation, the Alderton, through the Holocene. Pollen stratigraphy of these deposits is represented by 12 major pollen zones and is ostensibly continuous through Zone 8 over more than 47,000 radiocarbon yr. Before this, the stratigraphy is discontinuous and the chronology less certain. Environments over the time span of the deposits are reconstructed by the comparison of fossil and modern pollen assemblages and the use of relevant meteorological data. The Alderton Interglaciation is characterized by forests of Douglas fir (Pseudotsuga menziesii), alder (Alnus), and fir (Abies). During the next younger interglaciation, the Puyallup, forests were mostly of pine, apparently lodgepole (Pinus contorta), except midway in the interval when fir, western hemlock (Tsuga heterophylla), and Douglas fir temporarily replaced much of the pine. Vegetation outside the limits of Salmon Springs ice (>47,00034,000 yr BP) varied chiefly between park tundra and forests of western hemlock, spruce (Picea), and pine. The Salmon Springs nonglacial interval at the type locality records early park tundra followed by forests of pine and of fir. During the Olympia Interglaciation (34,000–28,000 yr BP), pine invaded the Puget Lowland, whereas western hemlock and spruce became manifest on the Olympic Peninsula. Park tundra was widespread during the Fraser Glaciation (28,000–10,000 yr BP) with pine becoming more important from about 15,000 to 10,000 yr BP. Holocene vegetation consisted first of open communities of Douglas fir and alder; later, closed forests succeeded, formed principally of western hemlock on the Olympic Peninsula and of western hemlock and Douglas fir in the Puget Lowland. Over the length of the reconstructed environmental record, climate shifted between cool and humid or relatively warm, semihumid forest types and cold, relatively dry tundra or park tundra types. During times of glaciation, average July temperatures are estimated to have been at least 7°C lower than today. Only during the Alderton Interglaciation and during the Holocene were temperatures higher for protracted periods than at present.
A Holocene Vegetation Record from the Mississippi River Valley, Southeastern Missouri
Authors: King James E. , Allen William H.
Published: December 2004

Pollen preserved in a peat deposit from a large swamp, the Old Field in the Mississippi River Valley near Advance, Missouri, records radiocarbon-dated vegetation changes between 9000 and about 3000 years ago. The principal feature of both the percentage and influx pollen diagrams is the replacement of arboreal pollen, primarilyQuercus, Fraxinus, andCephalanthus, with Gramineae and NAP between 8700 and 5000 years BP. This vegetation shift is interpreted as reflecting a decrease in the extent of the Old Field swamp and its associated bottomland forest species along with the expansion of a grass-dominated herb community, as a result of a reduction in available ground water. The desiccation of the swamp during this period indicates a reduction in precipitation within the ground-water source area and a shift to a drier climate in the southern Midwest. The pollen suggests that the lowest water levels and driest climate in southeastern Missouri lasted from 8700 to 6500 years BP, at which time there is a partial reappearance of swamp species. Relatively dry conditions, however, continued until at least 5000 years BP. Although pollen influx data are lacking from the upper part of the profile, the relative pollen frequencies suggest an increase in trees after 5000 BP. The replacement of the arboreal vegetation by grasses and herbs between 8700 and 5000 years BP reflects the period of maximum expansion of the Prairie Peninsula in southeastern Missouri. The Old Field swamp provides the first pollen evidence that the vegetational changes along the southern border of the Prairie Peninsula were chronologically similar to those on the northern and northeastern margins.
The Relation of the Southern Trade Winds to Upwelling Processes During the Last 75,000 years
Authors: Molina-Cruz Adolfo
Published: December 2004

In the equatorial Pacific, between the Galapagos Islands and the coast of South America, two kinds of upwelling of oceanic waters occur. One is related to coastal upwelling and the other to surfacing of the Equatorial Undercurrent. Both of those processes are associated with the development of the southeast trade winds blowing in this area. Coastal upwelling is increased when the trade winds are intensified, and the surfacing of the Equatorial Undercurrent occurs when the trades weaken. The development of coastal upwelling and the surfacing of the Equatorial Undercurrent are inferred from the radiolarian assemblages in the sediments. The abundance of quartz, opal, and radiolarian assemblages in the deep-sea sediments of this area, as well as the distance from the sample locations to land and to the quartz source, is correlated with the intensity of the trade winds (in February and August) through multiple regression analysis. The chronostratigraphy of core V19-29 (3°35′S, 83°56′W), used in this study, is inferred on basis of its δ180 record. During the last 75,000 years, the fluctuations in intensity of the trade winds have been concurrent with or preceded the fluctuations in the amount of ice stored on the continents. In general, the wind velocity of the winter trades has been intensified during cool climatic stages of the earth (δ180 stages 4 and 2) and they have been relaxed during warm stages (δ180 stages 3 and 1). Seasonal contrast of the trade winds has also fluctuated within time, having been relatively high during the upper part of δ180 stage 3.
Transfer functions Under no-Analog Conditions: Experiments With Indian Ocean Planktonic Foraminifera
Authors: Hutson William Halsey
Published: December 2004

This paper documents and investigates an important source of inaccuracy when paleoecological equations calibrated on modern biological data are applied downcore: fossil assemblages for which there are no modern analogs. Algebraic experiments with five calibration techniques are used to evaluate the sensitivity of the methods with respect to no-analog conditions. The five techniques are: species regression; principal-components regression [e.g., Imbrie, J., and Kipp, N. G. (1971). In “The Late Cenozoic Ages,” 71–181]; distance-index regression [Hecht, A. D. (1973). Micropaleontology 19 , 68–77]; diversity-index regression (Williams, D. F., and Johnson, W. C. (1975). Quaternary Research 5 , 237–250]; weighted-average method [Jones, J. I. (1964). Unpublished Ph. D. Thesis, Univ. of Wisconsin]. The experiments indicate that the four regression techniques extrapolate under no-analog conditions, yielding erroneous estimates. The weighted-average technique, however, does not extrapolate under no-analog conditions and consequently is more accurate than the other techniques. Methods for recognizing no-analog conditions downcore are discussed, and ways to minimize inaccuracy are suggested. Using several equations based on different calibration techniques is recommended. Divergent estimates suggest that no-analog conditions occur and that estimates are unreliable. The value determined by the weighted-average technique, however, may well be the most accurate.
Ice-Sheet Initiation and Climatic Influences of Expanded Snow Cover in Arctic Canada
Authors: Williams Larry D.
Published: December 2004

It has been suggested that the Laurentide Ice Sheet originated with extensive perennial snow cover, and that the snow cover affected climate so as to aid ice-sheet development. In this study, a large increase in extent of October 1st snow cover in the Canadian Arctic from 1967–1970 to 1971–1975 is compared to changes in October means of other climate variables. Over the area of snow-cover expansion, mean surface air temperature decreased by up to 3°C, mean 500-mbar height was lowered by over 60 m, and precipitation was increased by up to a factor of two. These effects, if applied to the entire summer, together with the temperature change computed by Shaw and Donn for a Northern Hemisphere summer insolation minimum (the Milankovich effect), can account for glacierization of the Central Canadian Arctic.
The Origin of Island Mammoths and the Quaternary Land Bridge of the Northern Channel Islands, California
Authors: Johnson Donald Lee
Published: December 2004

Pygmy proboscidean remains of Mammuthus exilis occur abundantly in late Quaternary deposits on the Northern Channel Islands, California. On the assumption that ancestral elephants could not have swum to the islands and must therefore have walked out, various land bridges have been hypothesized that link the northern islands to the mainland by a peninsula. Geological evidence for a land bridge, however, is lacking, and new evidence shows that elephants are excellent swimmers and skilled at crossing watergaps. The Santa Barbara Channel was narrowed to only 6 km during glacially lowered sea levels. Modern elephants swim much further, and at speeds ranging from 0.96–2.70 km/hr. Motives for California elephants to cross Pleistocene watergaps are inferred from motives that lead modern elephants in Asia and Africa to cross watergaps. These are the visual and olfactory sensing of islands and of insular food during times of drought or fire-induced food shortage. Diminutive size of M. exilis principally reflects lack of island predators, an adaption to periodic food stress in a finite forage area affected by periodic drought and fire, and an adaptation for keeping population numbers high to maintain genetic variability and to ensure survival despite accidents. A late Quaternary scenario describes the environmental setting of the Santa Barbara Channel and the conditions that led to proboscidean dispersal to the preexistent super-island Santarosae.
Late Pleistocene Piñon Pines in the Chihuahuan Desert
Authors: Lanner Ronald M. , Van Devender Thomas R.
Published: December 2004

Examination of late Pleistocene packrat middens from the northern and central Chihuahuan Desert disclosed macrofossils of Colorado piñon (Pinus edulis) and Texas piñon (P. remota). Radiocarbon dating indicates that Texas piñon was widespread in Trans-Pecos Texas and northeastern Mexico between 30,000 and 11,000 yr B.P. Today it is found in small refugia east of its former range. In the late Pleistocene Colorado piñon occurred at lower elevations on the northern edge of the Chihuahuan Desert. Both species occurred in the Hueco Mountains, near El Paso, Texas. No clear evidence was found of the presence of Mexican piñon (P. cembroides), though today it is abundant in the Davis and Chisos Mountains. A paleoclimate is postulated that had the following characteristics: increased winter precipitation from Pacific frontal sources, reduced summer temperatures and precipitation, and milder winter temperatures due to a reduced frequency of Arctic airmass incursion. Winter precipitation appears to have decreased from north to south, while winter temperatures, and, possibly, summer precipitation, increased from north to south. During the late Pleistocene, the northern Chihuahuan Desert was dominated by woodlands of piñon pines, junipers, and oaks. The desert-scrub communities that characterize the area today are a Holocene phenomenon.
Late Quaternary Evolution of Coastal Sand Barriers, Port Stephens-Myall Lakes Area, Central New South Wales, Australia
Authors: Thom B.G. , Bowman G.M. , Roy P.S.
Published: December 2004

The geomorphic and stratigraphic history of six coastal embayments has been studied in the vicinity of Newcastle, New South Wales (N.S.W.), Australia, in order to determine modes of deposition, and the degree to which marine and estuarine deposits can be correlated and dated. Each embayment possesses its own distinctive suite of landforms ranging from those dominated by coastal dunes to those in which beach ridges occur. In four of the bays dual sand barriers, comprising an Inner Barrier and an Outer Barrier, provide the framework for correlation between embayments. Six stages are recognized in the deposition of late Quaternary sediments in this area: (i) Pre-Last Interglacial, involving accumulation of separate composite units consisting of estuarine clays and transgressive dune complexes; (ii) Last Interglacial stage during which Inner Barriers were formed; (iii) Last Glacial reworking of barrier and dune sands by westerly winds; (iv) Postglacial Marine Transgression during which the Outer Barriers were initiated; (v) Mid-Holocene stage following cessation of sea-level rise ca. 6000–6500 yr B.P. on this coast, and involving progradation of Outer Barriers in some embayments; and (vi) Late Holocene episodic eolian reworking of dune complexes and Outer Barriers. The relatively high wave and wind energy as well as the tectonic setting of the central N.S.W. coast results in somewhat different geomorphic histories from barrier-island coasts in North America and Europe.
Historical Ecology in Beringia: The South Land Bridge Coast at St. Paul Island
Authors: Colinvaux Paul
Published: December 2004

A 14-m core of lake sediments from St. Paul Island yields a long environmental history of the south coast of the Bering land bridge. Tritium assay demonstrates that sands in the bottom 8 m of deposit are injected with modern water, suggesting that a radiocarbon anomaly is the result of modern carbon introduced in groundwater. The remaining radiocarbon chronology, coupled with a time-stratigraphic pollen-zone boundary suggests that the record penetrates to the mid-Wisconsin interstadial. Pollen percentage data,Piceapollen influx, and pollen species lists allow reconstruction of the land bridge vegetation, which was tundra, without shrubs or trees, with bare ground, and comparable to Bering land bridge tundras found further north. There was no coastal mild or wet strip. Plant associations comparable to those of the modern Aleutians or Pribilofs probably did not exist along the land bridge coast and the region was probably not suitable for breeding by fur seals and other marine mammals. A cold, dry, continental air-mass system reached to the coast itself. The south land bridge coast did not offer an environment to aboriginal human populations that was significantly milder than that of the land bridge plains to the north. At about 11,000 yr B.P. the Wisconsin dry climate was replaced by a regimen comparable to that at the modern tree line of the interior, and this climate in turn was replaced with the modern system at about 9500 yr B.P. Climatic change was independent of fluctuating sea level.
Late Quaternary History of Lake Manitoba, Canada
Authors: Teller James T. , Last William M.
Published: December 2004

The postglacial history of Lake Manitoba has been deduced from a study of the changes in physical, mineralogical, and chemical variables in sediment cores collected from the lake. Six lithostratigraphic units are recognized in the South Basin of the lake. Weakly developed pedogenic zones, reflecting dry or extremely low water conditions in the basin, separate five of these six units. The initial phase of lacustrine sedimentation in the Lake Manitoba basin began shortly after 12,000 yr B.P. as water was impounded in front of the receding glacier to form Lake Agassiz. By 11,000 yr ago, continued retreat of the ice sheet opened lower outlets to the east and much of Lake Agassiz drained, including the Lake Manitoba basin. Water levels again rose at 9900 yr B.P., but by about 9200 yr B.P. the South Basin was again dry. For the next 4700 yr there was an alternation of wet and dry conditions in the basin in response to the interaction of a warmer and drier climate and differential crustal rebound of the basin. About 4500 yr ago a new phase of Lake Manitoba sedimentation was initiated when the Assiniboine River began to discharge into the South Basin. The Assiniboine River was diverted out of the Lake Manitoba watershed about 2200 yr ago. Erosion and redistribution of the sandy deltaic sediments deposited by the Assiniboine River has created the barrier beach that now separates the extensive marsh to the south of the lake from the main lake.
Evidence of Multiple Late-Wisconsin Floods from Glacial Lake Missoula in Badger Coulee, Washington
Authors: Bunker Russell C.
Published: December 2004

Catastrophic floods from glacial Lake Missoula entered the Pasco Basin in south-central Washington and backflooded its marginal valleys. Badger Coulee, one such valley, contains beds of fine-grained slackwater sediment deposited by these floods. The slackwater sediment contains two ash layers of the Mount St. Helens set S tephra, about 13,000 yr old. The ash was deposited on a ground surface developed atop slackwater sediment deposited during preash flooding. Evidence of the former ground surface includes the reworked ash, inferred trace fossils, stream and debris-flow deposits, slopewash and/or eolian sediment, and colluvium at the ash horizon. These features and the ash were buried by slackwater sediment deposited during postash flooding. Nonflood, subaerial deposits are not present atop other beds. Instead, beds commonly are reversely graded across “contacts,” suggesting that multiple beds were continuously deposited. The exposed beds thus record at least two late-Wisconsin floods, one preash, the other postash. The pre- and postash floods may be correlative with earlier-reported floods thought to have occurred 17,500-14,000 and 14,000–13,000 yr B.P., respectively.
A Climate-Related Oxidizing Event in Deep-Sea Sediment from the Bering Sea
Authors: Gardner James V. , Dean Walter E. , Klise David H. , Baldauf Jack G.
Published: December 2004

Many cores from the deep basins of the Bering Sea have a thin oxidized zone within otherwise reduced sediment. This oxidized zone began to form about 6000 yr ago and represents an interval of about 3200 yr. Mineralogically, the oxidized and reduced sediments are similar, but chemically they differ. Concentrations of Fe and C are lower, and concentrations of Mn, Ba, Co, Mo, and Ni are higher in the oxidized than in the reduced sediment. Mn is enriched about 10-fold in the oxidized zone relative to its concentration in the reduced sediment, Mo about threefold, and Ba, Co, and Ni about twofold. These data suggest that the oxidized zone developed diagenetically as the result of the balance between the flux of organic matter and the available dissolved oxygen in bottom and interstitial waters.

We propose that the Bering Sea was substantially ice covered when global glacial conditions prevailed. during the transition to global interglacial conditions, seasonal meltwater from thawing sea ice formed a lens of fresh water that decreased organic productivity. During the winter seasons, however, sea ice reformed and caused downwelling of dense, oxygen-rich waters to recharge bottom waters. The combination of lower organic productivity and more oxygen-rich bottom water allowed oxidized sediment to accumulate. Once full interglacial conditions were established, the volume of sea ice produced was insufficient to affect either productivity or the supply of dissolved oxygen and so bottom conditions again became reducing.

Similar events probably occurred during the onset of global glacial conditions, and similar oxidized layers probably formed at these times. Such oxidized zones are highly unstable, however, in a reducing environment and, once buried beyond the influence of bacterial and infaunal activities, are depleted of their available oxygen and converted to reduced sediment.
Stratigraphy, Pollen Analysis, and Paleoclimatic Interpretation of Pulbeena Swamp, Northwestern Tasmania
Authors: Colhoun E. A. , van de Geer G. , Mook W. G.
Published: December 2004

Sedimentary, palynologic, and14C analysis of 480 cm of freshwater marl and swamp-peat deposits, formed under the influence of fluctuating artesian springs, provides a paleoenvironmental and paleoclimatic record of approximately 65,000 yr for northwestern Tasmania.

The Holocene (Pollen Zone 1, 11,000-0 yr B.P.) climate was warm and moist, and forest vegetation was dominant throughout the area. During the later part of the last glacial stage (Pollen Zone 2, 35,000–11,000 yr B.P.) the climate was generally drier, and grassy open environments were widespread. The driest part of this period occurred between 25,000 to 11,000 yr B.P., when temperatures in western Tasmania were markedly reduced during the last major phase of glaciation. Prior to 35,000 yr B.P. (Pollen Zones 3–9) a long “interstadial complex” dating to the middle of the last glacial stage is recognized. During this period the climate was generally moist, and forest and scrub communities were more important than during the later part of the last glacial stage, except during Pollen Zone 5 when high Gramineae plus Compositae values suggest drier conditions. High Gramineae and Compositae values also occur in Pollen Zone 10 at the base of the diagram. They suggest that a phase of drier and cooler climatic conditions occurred during the early part of the last glacial stage.
A Late Quaternary Pollen Record from the Transvaal Bushveld, South Africa
Authors: Scott Louis
Published: December 2004

Pollen spectra from cores of organic spring deposits from the Transvaal provide evidence for the climatic evolution of the province during the last 35,000 yr B.P. or more. The past climatic phases are derived from palynological reconstructions of past vegetation types by comparison of fossil pollen data with modern surface pollen spectra from various localities. Evidence is provided for an early moist, cool phase with relatively mesic bushveld and expanded montane forest in the central Transvaal, followed by a drier period with drier bushveld which probably lasted until approximately 25,000 yr B.P. During the next phase, which at the latest ended about 11,000 yr B.P., the temperatures were probably 5°–6°C cooler than at present. At that time bushveld vegetation in the central Transvaal was replaced by open grassland with macchia elements. Climatic amelioration came and semiarid savanna returned to the plains, at first gradually and then developing into a warm Kalahari thornveld-type vegetation. After 6000 yr B.P. it apparently became slightly wetter and a more broad-leafed bushveld developed. About 4000 yr B.P. it again became cooler and slightly wetter and the bushveld vegetation on the central and northern plains was comparable to present open upland types. After 2000 yr B.P. conditions gradually became warner until about 1000 yr B.P., when the modern climate of the central Transvaal bushveld originated.