bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Sorediate Species of Menegazzia (Parmeliaceae, Lichenized Ascomycota) from Chile
Authors: Bjerke J. W.
Published: September 2002

Menegazzia wandae Bjerke from Chile is newly described. It is characterized by lacerate soraliathat are formed on laminar pustules; the sinuous, rather imbricate lobes with brown-black margins, and the presence of thamnolic acid in the medulla. Apothecia are unknown, and pycnidia are rare. The species is known from Chile between latitudes 38°30´S and 46°40´S.
Studies in Bacidia Sensu lato (Lichenized Ascomycetes: Lecanorales). II. Six new Combinations in Fellhanera Vězda
Authors: Lücking R. , Cáceres M. E. S. , Kalb K. , Sérusiaux E.
Published: September 2002

In the framework of ongoing studies on tropical representatives of Bacidiasensu lato, six species so far included in that genus are transferred to Fellhanera: Fellhanera Africana(Vězda) Lücking comb. nov. (Bas.: Bacidia Africana (Vězda), Fellhanera albidocincta Vain.) Lücking comb. nov. (Bas.: Bilimbia albidocincta Vain.), Fellhanera fragilis (Vězda) Lücking & Kalb comb. nov. (Bas.: Bacidia fragilis (Vězda), Fellhanera mastothallina (Vain.) Lücking & Serus. comb.nov. (Bas.: Bacidia mastothallina Vain.), Fellhanera naevia(Vain.) Lücking & Caceres comb. nov. (Bas.: Bacidia naevia Vain.), and Fellhanera submicrommata (Vězda) Lücking & Kalb comb. nov. (Bas.: Bacidia submicrommata Vězda). Fellhanera angustispora Lücking is reduced into synonymy with F. naevia.
New Species or Interesting Records of Foliicolous Lichens. VIII. Two New Taxa from Tropical Africa, with a Key to Sorediate Fellhanera Species
Authors: Lücking Robert , Santesson Rolf
Published: September 2002

Two new species belonging to the lichen families Pilocarpaceae and Ectolechiaceae are described from tropical Africa: Calopadia lucida sp. nov. (Ectolechiaceae) from Tanzania, being similar to C. puiggarii but differing in the UV fluorescent thallus and the pruinose apothecia, and Fellhanera ivoriensis sp. nov. (Pilocarpaceae) from the Ivory Coast, differing from the related F.rhapidophylli by the sorediate thallus and from other sorediate taxa by the combination of pale soralia, dark brown apothecia, and the ellipsoid-bacillar conidia. A key to the nine sorediate species of Fellhanera is provided.
Accurate lifespan estimates cannot be obtained from 14C profiles in the crustose lichen Rhizocarpon geographicum (L.) DC.
Authors: Bench G. , Clark B.M. , Mangelson N.F. , St. Clair L. L. , Rees L. B. , Grant P.G. , Southon J. R.
Published: September 2002

Radial 14C/C profiles across three individuals of the crustose lichen Rhizocarpon geographicum (L.) DC. have been determined using accelerator mass spectrometry. These data were used to assess whether lifespan estimates can be determined in this species using 14C/C isotope ratio measurements. 14C/C profiles are relatively flat with Δ14C values (deviations from the modern radiocarbon standard) for the radial samples displaying a small spread ranging from 130 to 200 per mil. The data are consistent with carbon cycling based on growth patterns involving replacement and fusion of areoles within the thallus as well as or instead of cellular or molecular replacement. Consequently, lifespan estimates cannot be obtained from 14C/C measurements of this species and the Δ14C profiles provide no insights into whether the relationship between size and age is linear or curvilinear in this species.
North American Pika (Ochotona princeps) as a Late Quaternary Biogeographic Indicator Species
Authors: Hafner David J.
Published: September 2002

Reevaluation of Quaternary sites of fossil pika (Ochotona) lends no support for the inference that Nearctic pikas were not restricted to rocky habitat. The saxicolous nature of all widespread, isolated populations of extant Nearctic pikas and their closest Palearctic sister taxa support consideration ofO. princeps, and perhaps all Nearctic QuaternaryOchotona, as indicators of cool, mesic, rocky situations. As indicators of rocky microhabitat, fossil remains ofO. princepsdo not require that the entire region was cool and mesic, but only that suitable rocky microhabitat existed in the vicinity. Use of fossil pika dung alone as indicative of pikas in the immediate community is suspect, as the small, round, and buoyant pellets may be transported downslope by hydraulic flushing of talus habitat. Current local elevational lower limits (E) of appropriate habitat for paleoecological reconstruction at extralimital fossil sites are predicted by the equation:E(m) = 14087 - (56.6)°N - (82.9)°W.
Extensive Boulder Erosion Resulting from a Range Fire on the Type-Pinedale Moraines, Fremont Lake, Wyoming
Authors: Zimmerman Susan G. , Evenson Edward B. , Gosse John C. , Erskine Charles P.
Published: September 2002

In July 1988, the FlatFish Range Fire burned over the type-Pinedale moraines at Fremont Lake, Wyoming, and caused extensive exfoliation of exposed boulder surfaces. The mass of exfoliated material from 130 of 1030 boulders investigated was measured and recorded with information concerning factors that could influence the extent of fire-induced exfoliation. The range in thickness of material removed from 98 randomly selected boulders within the burn area (averaged over the entire exposed boulder surface area) is 6.1 to < 0.1 mm. The mean thickness loss for all 98 boulders is 0.9 mm/fire and the expected loss from individual boulders (median) is 0.4 mm/fire. At the 95% confidence level there is no significant relationship between the degree of exfoliation and boulder size, lithology, grain size, proximity to vegetation, or vegetation density. The expected fire-induced boulder surface erosion rates range from 5.9 to 0.3 x 10-3mm/yr on boulders in sagebrush rangeland where fire recurrence intervals are typically every 20 to 400 yr. Fire-induced exfoliation may account for differences in boulder size and abundance on Pinedale and Bull Lake moraines. Surface dating methods using varnish or cosmogenic nuclides may yield exposure ages that are too young if the consequences of range fires are not considered when sampling boulder surfaces that are within about 2 m above ground level.
Glacial Lowstand Deposits on the Outer Continental Shelf of Southeastern Australia
Authors: Ferland Marie A. , Roy Peter S. , Murray-Wallace Colin V.
Published: September 2002

Vibracores collected from water depths of 130 to 150 m on the outer continental shelf of southeastern Australia contain evidence for several cycles of shallow marine deposition. One of these vibracores (112/VC/134; lat. 33°24′S, long, 151°58′ E) preserves evidence for the last three glacial lowstands, as inferred from radiocarbon dating, amino acid racemization, and fossil mollusc assemblages. The core contains the inner-shelf molluscsPecten fumatus, Placamen placidium, andTawera gallinula, which today live in water depths of 10 to 50 m, in the cool waters of southern Australia. Radiocarbon dating and amino acid racemization analyses on multiple valves ofP. fumatusin the core indicate three distinct age groupings of fossil molluscs: (1) those younger than 20,000 yr B.P., (2) those with minimum ages of about 100,000 yr, and (3) those with minimum ages of about 200,000 yr. We assign these sediments to oxygen isotope stages 2, 6, and 8, respectively. The core contains the first shallow-marine lowstand deposits to be recovered from the shelf of eastern Australia. These deposits constrain the last three glacial lowstands on this margin to water depths <130 m below present sea level.
Age of Pre-late-Wisconsin Glacial-Estuarine Sedimentation, Bristol Bay, Alaska
Authors: Kaufman Darrell S. , Forman Steven L. , Lea Peter D. , Wobus Cameron W.
Published: September 2002

Pleistocene glacial-estuarine sediment deposited in an intertidal environment of northeastern Bristol Bay, southwestern Alaska, was dated using a variety of approaches, including infrared stimulated and thermoluminescence (IRSL and TL) techniques. Analysis of modern and14C-dated Holocene tide-flat mud demonstrates that the bulk of sediment in this environment is reset by solar radiation, thereby lending confidence to ages obtained from similar Pleistocene deposits by luminescence techniques. IRSL seems to be especially well suited for dating, with resolution on time scales of <10,000 yr. The ages of tide-flat mud of the Nushagak Formation, derived from the Ahklun Mountains to the northwest of Bristol Bay, and of Halfmoon Bay drift, derived from the Alaska Peninsula to the southeast, suggest contemporaneous glacial-estuarine deposition related to independent glacial source areas about 75,000–80,000 yr ago. This age is consistent with other geochronological data that indicate a pre-late-Wisconsin and post-substage-5e age, including nonfinite14C ages, a lack of interglacial indicators, and Old Crow tephra (∼140,000 yr) atop the drift, normal paleomagnetic inclinations, and amino acid (isoleucine) epimerization ratios (aIle/Ile). AIle/Ile ratios inPortlandia arctica(0.052 ± 0.003) from a marine-lag horizon at South Naknek beach, which separates Halfmoon Bay drift above from older glacial-estuarine drift below, are only slightly higher than inMya truncata(0.041 ± 0.007) from last-interglacial Pelukian deposits at Nome. As laboratory heating experiments show that the two genera epimerize at similar rates, these data imply correlation of the marine lag at South Naknek beach with Pelukian deposits. Hence, glaciers on the Alaska Peninsula experienced major pre-late-Wisconsin advances both before and after the last interglaciation. Shells reworked into Halfmoon Bay drift yield aIle/Ile ratios of 0.028 ± 0.005 forPortlandiaat Second Point and 0.027 ± 0.001 forHiatella arcticaat Etolin Point. Together with assumptions about the postdepositional temperature history, these ratios indicate that the shells are at least 55,000 yr, and probably closer to ∼90,000 yr, although the uncertainty in this age estimate is broad. The amino acid and luminescence data converge on an age between about 75,000, and 90,000 yr, late during oxygen-isotope stage 5, for a major ice advance far beyond late-Wisconsin limits.
Quaternary Sedimentary Processes and Budgets in Orphan Basin, Southwestern Labrador Sea
Authors: Hiscott Richard N. , Aksu Ali E.
Published: September 2002

The continental slope in Orphan Basin, northeast of Newfoundland, is underlain by several seaward-thinning debris-flow wedges alternating with acoustically stratified, regionally extensive, mainly hemipelagic sediments. δ18O stratigraphy and volcanic ash layers in a 11.67-m core indicate that the uppermost debris-flow wedge formed during the last of several sea-level lowstands in isotopic stages 2–4. Similarly, seismic reflection correlation of dated levels at DSDP Site 111 with the Orphan Basin succession suggests that two deeper debris-flow wedges were deposited during oxygen isotopic stages 6 and 8. The oldest of the debris-flow deposits in at least three of the wedges formed well into the corresponding glacial cycle, after ice sheets had reached the edge of the continental shelf. Slower deposition by hemipelagic processes and ice rafting formed the acoustically stratified units, including Heinrich layers. The youngest three debris-flow wedges each have volumes of 1300–1650 km3. Approximately two-thirds of this material is attributed to glacial erosion of Mesozoic and Tertiary strata beneath the Northeast Newfoundland Shelf. The remainder is believed to have been derived by glacial erosion of older bedrock that now forms the island of Newfoundland. The observed sediment volumes and the inferred basal and upper ages of the debris-flow wedges imply an average glacial denudation rate of about 0.13 mm/yr for this older bedrock, and an average of about 60 m of glacial bedrock erosion since oxygen isotope stage 22. This denudation rate is similar to estimates from the Barents Sea region off Norway.
Boreal Ecosystem Development in the Northwestern Alaska Range since 11,000 yr B.P.
Authors: Hu Feng Sheng , Brubaker Linda B. , Anderson Patricia M.
Published: September 2002

Analyses of pollen, plant macrofossils, macroscopic charcoal, mollusks, magnetic susceptibility, and geochemical content of a sediment core from Farewell Lake yield a 11,000-yr record of terrestrial and aquatic ecosystem changes in the northwestern foothills of the Alaska Range. Between 11,000 and 8500 yr B.P., the regional landscape was dominated by aBetulashrub tundra, in whichPopulus-Salixcommunities were common. Abundant charcoal in sediments indicates that fires were common in the lake catchment during this period, and high mineral accumulation rates, allogenic elemental content, and magnetic susceptibility suggest intense soil erosion. In addition, mollusks, pollen and macrofossils of aquatic macrophytes, and biogenic silica provide evidence that the lake was substantially shallower and more productive 11,000–8500 yr B.P. than later. Low lake level and high aquatic productivity might have been caused by warm and dry summers associated with early postglacial insolation maximum in northern high latitudes. About 8000 yr B.P.,Picea glaucaarrived within the lake catchment, forming a forest tundra association until ca. 6000 yr B.P.Alnusshrub thickets established in the region ca. 6500 yr B.P., andBetula papyriferaarrived ca. 6000 yr B.P. ClosedP. glaucaforests developed ca. 6000 yr B.P.Picea marianabecame important subsequently and replacedP. glaucaas the dominant tree species in the region ca. 4000 yr B.P. An increase in authigenic Fe/Mn ratios suggests that the development of waterlogged soils accompanied this vegetation change. Fires increased in importance at this time and might have accelerated soil erosion. The establishment ofP. marianaforests probably reflected complex responses of forest ecosystems to the onset of cooler and wetter climate conditions during the late Holocene.
Paleoclimates Off Northwest Africa (28°–35°N) about 18,000 yr B.P. Based on Continental Eolian Deposits
Authors: Rognon Pierre , Coudé-Gaussen Geneviève
Published: September 2002

Most conceptual models of atmospheric circulation deduced from bottom sediments or isopollen maps off NW Africa assume the occurrence of intensified NNE trade winds about 18,000 yr B.P. in latitudes of 28°–35°N, and oversimplify the glacial atmospheric circulation over Africa. An alternative method for reconstructing paleowinds of the last glacial maximum in these latitudes was recently put forward, and uses sedimentological records from the Canary Islands and coastal regions of Morocco. The continental data do not agree with the previous models and show the prevalence of westerlies. All the data from deep sea cores (reduction of sea surface temperature, increase of biogenic opal accumulation, distribution patterns of pollen or dinoflagellate cysts, and xeric conditions on the adjacent continent) can be explained without increased activity of the trade winds, but with a discharge current of cold meltwater from the European and North American ice sheets. The model is backed up by a comparison with the present-day Humboldt Current off subtropical South America.
Implications of Stratigraphic and Paleoclimatic Records of the Last Interglaciation from the Nordic Seas
Authors: Bauch Henning A. , Erlenkeuser Helmut , Grootes Pieter M. , Jouzel Jean
Published: September 2002

Climatic reconstruction of glacial to interglacial episodes from oxygen isotopes in sediment cores from the Nordic seas is complicated by strong local meltwater contributions to the oxygen isotope changes. Combination of benthic and planktic foraminiferal isotope data with foraminiferal abundances and ice-rafted debris (IRD) allows separation of local and global effects and subdivision of the marine oxygen isotope events 6.2–5.4, which include the last interglaciation, into: (1) a meltwater phase after glacial stage 6, recorded by large amounts of IRD and low foraminiferal abundance, indicating surface water warming; (2) an IRD-free period with high deposition rates of subpolar foraminifera and other CaCO3 pelagic components, recognized here as the “full” interglaciation; and (3) a phase with the recurrence of IRD and the demise of subpolar species. Comparison of ice-core records and marine data implies that the global climate during the last full interglaciation and that during the postdeglacial Holocene were similar. The records show no significantly different variations in the proxy data. In contrast, the oxygen isotopes of planktic foraminifera and ice cores indicate significant differences during each of the deglacial transitions (Terminations I and II) that preceded these two interglaciations. These suggest that during Termination II the climatic evolution in the Nordic seas was less affected by abrupt changes in ocean–atmosphere circulation than during the last glacial to interglacial transition.
Nonassociation of Paleoindians with AMS-Dated Late Pleistocene Mammals from the Dutchess Quarry Caves, New York
Authors: Steadman David W. , Stafford Thomas W. , Funk Robert E.
Published: September 2002

AMS14C ages of 10 bones of the caribou (Rangifer tarandus), flat-headed peccary (Platygonus compressus), and giant beaver (Castoroides ohioensis) from the Dutchess Quarry Caves, New York, range from 13,840 ± 80 to 11,670 ± 70 yr B.P. No bones from any of these species are demonstrably associated with Paleoindian artifacts (fluted points) or other cultural materials from the sites because the bones lack unequivocal stratigraphic association with artifacts, as well as physical (taphonomic) evidence for human association (e.g., burning, cut marks, distinctive breakage). Together with the Holocene conventional14C dates of charcoal and the varied stratigraphic proveniences of the fluted points and the dated bones, the new AMS14C dates argue that most strata at the Dutchess Quarry Caves contain a mixture of late Pleistocene and Holocene materials. This mixing probably resulted from post-depositional bioturbation (by humans, rodents, carnivores, and scavengers) and cryoturbation (annual freeze–thaw cycles). Rather than being of cultural origin, the bones of caribou, flat-headed peccary, and giant beaver likely were deposited in the Dutchess Quarry Caves by nonhuman predators or scavengers, such as ursids, canids, felids, condors, or eagles.
Tephrochronologic Constraints on the Late Pleistocene History of the Southern Margin of the Cordilleran Ice Sheet, Western Washington
Authors: Begét James E. , Keskinen Mary J. , Severin Kenneth P.
Published: September 2002

An ash layer that appears geochemically correlative with Mt. St. Helens tephra set S occurs in a sequence of Pleistocene lake sediments in the Ohop Valley of the southern Puget Lowland, below Vashon till deposited during the maximum late Pleistocene advance (Fraser Glaciation) of the Puget Lobe of the Cordilleran Ice Sheet. The Puget Lobe reached its maximum southern extent ca. 14,000–14,500 yr B.P., and at least part of set S is evidently somewhat older. Previous radiocarbon and thermoluminescence dates for set S have ranged from 13,000 to 16,000 yr B.P.

Geochemically correlative deposits of set S tephra occur in slackwater sediments coeval with the Missoula Floods in eastern Washington, produced by jökulhlaups through the Purcell Trench Lobe of the Cordilleran Ice Sheet. These relationships suggest that advances of glacier lobes on the southern margin of the Cordilleran Ice Sheet were nonsynchronous, as the Pucell Trench lobe east of the Cascade Range advanced to its maximum southern extent prior to the time of the eruption of set S, before the Puget Lobe west of the Cascades reached its maximum southern extent.
Pleistocene Deposits in Pierre Saint-Martin Cave, French Pyrenees
Authors: Quinif Yves , Maire Richard
Published: September 2002

Pleistocene deposits in alpine Pierre Saint-Martin cave are preserved in an abandoned river gallery. The deposits, 300 m long and 25 m high, are composed of a lower unit of fallen blocks overlain by debris flows, a main unit of laminated clay, and a series of river terraces inset into these units. The lower and main units are each overlain by speleothems. The lower unit represents a cold period, probably isotope stage 10. Corroded speleothems above it have given U/Th ages greater than 300,000–330,000 yr B.P. The main unit, with carbonate-rich varves devoid of pollen, represents a glaciation that occurred before 225,000 yr B.P. and probably correlates with stage 8, even though such a glaciation has not been previously recognized in the Pyrenees. The river terraces, covered by many noncorroded speleothems, probably formed during stage 7 (U/Th ages between 194,000 and 211,000–225,000 yr B.P.). Subsequent sinking of an underground river protected the deposits from erosion.
Measuring Late Quaternary Ursid Diminution in the Midwest
Authors: Wolverton Steve , Lyman R.Lee
Published: September 2002

Paleobiologists generally agree that within the past 10,000 yr North American black bears (Ursus americanus) have decreased in body and tooth size. Some researchers infer that diminution was gradual and continuous; thus, one might infer that a specimen is old if it is larger than an average-size modern bear. Ursid remains recovered in the 1950s from Lawson Cave, Missouri, that are larger than some modern bears have been reported to date to the late Pleistocene, but association with modern taxa, taphonomic considerations, and a radiocarbon date of 200 yr B.P. indicate that they are modern. Modern specimens from Lawson Cave and other parts of the American Midwest are relatively large compared to modern North American black bears from other areas, suggesting that many supposed late Pleistocene bears from the area might be modern also.
Response of Bushy-Tailed Woodrats (Neotoma cinerea) to Late Quaternary Climatic Change in the Colorado Plateau
Authors: Smith Felisa A. , Betancourt Julio L.
Published: September 2002

Temperature profoundly influences the physiology and life history characteristics of organisms, particularly in terms of body size. Because so many critical parameters scale with body mass, long-term temperature fluctuations can have dramatic impacts. We examined the response of a small mammalian herbivore, the bushy-tailed woodrat ( Neotoma cinerea), to temperature change from 20,000 yr B.P. to present, at five sites within the Colorado Plateau. Our investigations focused on the relationship between temperature, plant composition and abundance, and woodrat size. Body size was estimated by measuring fossil fecal pellets, a technique validated in earlier work. We found significant and highly covariable patterns in body mass over the five locations, suggesting that responses to temperature fluctuations during the late Quaternary have been very similar. Although woodrat mass and the occurrence of several plant species in the fossil record weresignificantly correlated, in virtually all instances changes in woodrat size preceded changes in vegetational composition. These results may be due to the greater sensitivity of woodrats to temperature, or to the shorter generation times of woodrats as compared to most plants. An alternative hypothesis is that winter temperatures increased before summer ones. Woodrats are highly sensitive to warmer winters, whereas little response would be expected from forest/woodland plants growing at their lower limits. Our work suggests that woodrat size is a precise paleothermometer, yielding information about temperature variation over relatively short-term temporal and regional scales.
Late-Glacial to Early Holocene Climate Changes from a Central Appalachian Pollen and Macrofossil Record
Authors: Kneller Margaret , Peteet Dorothy
Published: September 2002

A late-glacial to early Holocene record of pollen, plant macrofossils, and charcoal has been obtained from two cores from Browns Pond in the central Appalachians of Virginia. An AMS radiocarbon chronology defines the timing of moist and cold excursions, superimposed on the overall warming trend from 14,200 to 750014C yr B.P. This site had cold, moist conditions from ca. 14,200 to 12,70014C yr B.P., with warming at 12,730, 11,280, and 10,05014C yr B.P. A decrease in deciduous broad-leaved tree taxa andPinus strobus(haploxylon) pollen, simultaneous with a reexpansion ofAbies,denotes a brief, cold reversal from 12,260 to 12,20014C yr B.P. A second cold reversal, inferred from increases in montane conifers, is centered at 750014C yr B.P. The cold reversals at Browns Pond may be synchronous with climate change in Greenland and northwestern Europe. Warming at 11,28014C yr B.P. shows the complexity of regional climate responses during the Younger Dryas chronozone.
Cyclic Aggradation and Downcutting, Fluvial Response to Volcanic Activity, and Calibration of Soil-Carbonate Stages in the Western Grand Canyon, Arizona
Authors: Lucchitta Ivo , Curtis Garniss H. , Davis Marie E. , Davis Sidney W. , Turrin Brent
Published: September 2002

In the western Grand Canyon, fluvial terraces and pediment surfaces, both associated with a Pleistocene basalt flow, document Quaternary aggradation and downcutting by the Colorado River, illuminate the river's response to overload and the end of overload, and allow calibration of soil-carbonate stages and determination of downcutting rates. Four downcutting–aggradation cycles are present. Each begins with erosion of older deposits to form a new river channel in which a characteristic suite of deposits is laid down. The current cycle (I) started ∼700 yr B.P. The oldest (IV) includes the 603,000 ± 8000 to 524,000 ± 7000 yr Black Ledge basalt flow, emplaced when the river channel was ∼30 m higher than it is now. The flow is overlain by basalt–cobble gravel and basalt sand. Soils reach the stage V level of carbonate development. Calibrated ages for soil stages are Stage V, ∼525,000 yr; stage IV, <525,000 yr, ≥250,000 yr; stage III, <250,000 yr, ≥100,000 yr. The monolithologic basalt sand beds represent overloading by volcanic ash produced by an eruption 30–50 km upstream. The basalt–cobble beds signal breaching and rapid destruction of lava dams and erosion of flows. These deposits show that the Colorado River responds to overload by aggrading vigorously during the overload and then downcutting equally vigorously when the overload ends. The overall downcutting rate for the interval studied is 1.6 cm/1000 yr, much lower than rates upstream. The current downcutting rate, 11–14 m/1000 yr, likely is a response both to the end of late Pleistocene and early Holocene overload and to the reduction of sediment supply caused by Glen Canyon Dam.
African Monsoonal Precipitation Modulated by Interhemispheric Temperature Gradients
Authors: Mulitza Stefan , Rühlemann Carsten
Published: September 2002

The deglacial pattern of a high-resolution alkenone-derived temperature record from the southeastern tropical Atlantic was compared with one from the northeastern subtropical Atlantic. During Termination 1b, surface waters in the eastern tropical Atlantic (6°S) reached modern temperatures, whereas those in the subtropical northeastern Atlantic (21°N) were still considerably colder than today. This asymmetrical warming may reflect meltwater-induced reductions in the northward heat transport and helps to explain rapid changes in monsoonal precipitation over Africa during the early Holocene.
14,000 Years of Sediment, Vegetation, and Water-Level Changes at the Makepeace Cedar Swamp, Southeastern Massachusetts
Authors: Newby Paige E. , Killoran Peter , Waldorf Mahlon R. , Shuman Bryan N. , Webb Robert S. , Webb Thompson
Published: September 2002

Data from a transect of four cores collected in the Makepeace Cedar Swamp, near Carver, Massachusetts, record past changes in deposition, vegetation, and water level. Time series of palynological data provide a 14,000-yr record of regional and local vegetation development, a means for biostratigraphic correlation and dating, and information about changes in water level. Differences in records among cores in the basin show that water level decreased at least 1.5 m between ∼10,800 and 9700 cal yr B.P., after which sediment accumulation was slow and intermittent across the basin for about 1700 yr. Between 8000 and 5600 cal yr B.P., water level rose ∼2.0 m, after which slow peat accumulation indicates a low stand about the time of the hemlock decline at 5300 ± 200 cal yr B.P. Dry conditions may have continued after this time, but by 3200 cal yr B.P., the onset of peat accumulation in shallow cores indicates that water level had risen to close to its highest postglacial level, where it is today. Peat has accumulated across the whole basin since 3200 cal yr B.P. Data from Makepeace and the Pequot Cedar Swamp, near Ledyard, Connecticut, indicate an early Holocene dry interval in southern New England that began 11,500 yr ago near the end of the Younger Dryas interval. The dry conditions prevailed between 10,800 and 8000 cal yr B.P. and coincide with the arrival and later rise to dominance of white pine trees (Pinus strobus) both regionally and near the basins. Our results indicate a climatic cause for the “pine period” in New England.
Glacial Sediment–Landform Associations and Paleoclimate during the Last Glaciation, Strait of Magellan, Chile
Authors: Benn Douglas I. , Clapperton C. M.
Published: September 2002

Glacial sediments and landforms preserved beside the Strait of Magellan record repeated advances of an outlet of the Patagonian Icefield during and following the last glacial maximum (LGM; ∼25,000–14,00014C yr B.P.). Ice-marginal landform assemblages consist of thrust moraine complexes, kame and kettle topography, and lateral meltwater channels, very similar to those found at the margins of modern subpolar glaciers. Taken together with other forms of paleoenvironmental evidence, the landform assemblages show that, during the LGM and late-glacial time, permafrost occurred near sea level in southernmost South America. This finding implies that mean annual temperatures were ∼7–8°C lower than at present, somewhat lower than those reconstructed by current glacier–climatic models. Comparison with precipitation–temperature relationships for modern glaciers suggests, in addition, that precipitation levels were lower than today. Reduced glacial-age precipitation may have resulted from a precipitation shadow induced by the Patagonian Icefield, an equatorward migration of the average position of westerly cyclonic storm tracks in the southern midlatitudes, or both these factors.
Late Wisconsinan Glaciation of the Central Sector of the Canadian High Arctic
Authors: Lamoureux Scott F. , England John H.
Published: September 2002

Geomorphic and chronological evidence from Cornwall Island in the Canadian High Arctic Archipelago provides direct evidence for the age and dynamics of the center and northern flank of the Innuitian Ice Sheet that covered the islands during the Late Wisconsonian glacial maximum. Dispersal of erratics and glacial landforms indicate that ice flowed north across the island and converged with ice flowing northwest from Norwegian Bay. Cornwall Island was initially deglaciated at 9000 14C yr B.P. in near synchrony with widely separated sites in adjacent parts of the archipelago. This regional chronology suggests rapid breakup of a marine-based Innuitian Ice Sheet that was destabilized by rapid eustatic sea-level rise and ice thinning during the early Holocene. This evidence provides strong support for a recently proposed ice divide spanning the central part of the Canadian High Arctic and indicates that most, if not all, of the region was glaciated during the Late Wisconsinan.
Late-Glacial History of Lago Argentino, Argentina, and Age of the Puerto Bandera Moraines
Authors: Strelin Jorge A. , Malagnino Eduardo C.
Published: September 2002

In the west-central part of Lago Argentino, the Puerto Bandera moraines are clearly detached from longer, more prominent moraines of the last glaciation and from shorter and smaller Neoglacial moraines. Scientists have long speculated about the age of the Puerto Bandera moraines. Detailed geomorphologic studies in the western area of Lago Argentino, including stratigraphic profiles at Bahı́a del Quemado in the northern branch (Brazo Norte), indicate that the Puerto Bandera moraines were deposited by three pulses of ice. Each of the three pulses is represented by single moraine ridges and belts of tightly arranged ridges. The timing of the three glacier advances was established by radiocarbon dating, including data published by John Mercer. The oldest moraine system, formed during the Puerto Bandera I substade, was deposited ca. 13,000 14C yr B.P. Moraines of the Puerto Bandera II substade were deposited ca. 11,000 14C yr B.P. The youngest moraine system was deposited during a minor readvance, shortly before 10,390 C14 yr B.P., and thus appears to have occurred some time during the European Younger Dryas interval. After this third substade, the ice tongues retreated into the interior branches of Lago Argentino and have remained there since. Evidence found at Bahı́a del Quemado, together with data provided by other authors, attests to a significant climatic change by the middle Holocene, which we believe occurred during the Herminita advance, the first Holocene glacial readvance recognized within the area.
Late-Glacial Cooling in Amazonia Inferred from Pollen at Lagoa do Caçó, Northern Brazil
Authors: Ledru Marie-Pierre , Cordeiro Renato Campello , Dominguez José Maria Landim , Martin Louis , Mourguiart Philippe , Sifeddine Abdelfetah , Turcq Bruno
Published: September 2002

New pollen data from a core at Lagoa do Caçó, Maranhão state, Brazil (2°58′S 43°25′W; 120 m elevation), show higher frequencies of Podocarpus at the end of the Pleistocene than today. The increase in Podocarpus, which follows the successive increase of various pioneer species such as Didymopanax, Melastomataceae/Combretaceae, and Cecropia, implies a progressive late-glacial increase of moist and cool climatic conditions. A comparable increase in Podocarpus is found in other lowland records in Amazonia. A review of published pollen data from Amazonia suggests that the moisture source was from the southeast. By contrast, present-day moisture comes from the tropical Atlantic and from the Amazon basin, with its convective precipitation. The likely cause for the southeastern moisture source between ca. 15,000 and 14,500 cal yr B.P. was enhanced polar (Antarctic) advection that reached low latitudes and maintained year-round the meteorological equator in its austral-winter position at northern latitudes or reduced drastically its southward summer displacement. This hypothesis is consistent with marine and ice core records.
Carbon-Isotope, Diatom, and Pollen Evidence for Late Holocene Salinity Change in a Brackish Marsh in the San Francisco Estuary
Authors: Byrne Roger , Ingram B. Lynn , Starratt Scott , Malamud-Roam Frances , Collins Joshua N. , Conrad Mark E.
Published: September 2002

Analysis of diatoms, pollen, and the carbon-isotopic composition of a sediment core from a brackish marsh in the northern part of the San Francisco Estuary has provided a paleosalinity record that covers the past 3000 yr. Changes in marsh composition and diatom frequencies are assumed to represent variations in freshwater inflow to the estuary. Three periods of relatively high salinity (low freshwater inflow) are indicated, 3000 to 2500 cal yr B.P., 1700 to 730 cal yr B.P., and ca. A.D. 1930 to the present. The most recent period of high salinity is primarily due to upstream storage and water diversion within the Sacramento–San Joaquin watershed, although drought may also have been a factor. The two earlier high-salinity periods are likely the result of reduced precipitation. Low salinity (high freshwater flow) is indicated for the period 750 cal yr B.P. to A.D. 1930.
Biogenic Silica Record of the Lake Baikal Response to Climatic Forcing during the Brunhes
Authors: Prokopenko Alexander A. , Karabanov Eugene B. , Williams Douglas F. , Kuzmin Mikhail I. , Shackleton Nicholas J. , Crowhurst Simon J. , Peck John A. , Gvozdkov Alexander N. , King John W.
Published: September 2002

This work presents a detailed, orbitally tuned biogenic silica record of continental paleoclimate change during the Brunhes chron. The Brunhes/Matuyama boundary lies within the warm isotopic stage 19 in Baikal, and the boundaries between eight lithological cycles correspond to terminations in the marine oxygen isotope record. The high amplitude and resolution of climatically driven changes in BioSi content in Lake Baikal sediments permits tuning of almost every precessional cycle during the Brunhes and reveals the structure of interglacial stages. For example, the last three interglacial stages (MIS 5, 7, and 9) clearly consist of five substages (a, b, c, d, e) corresponding to precessional insolation peaks. Abrupt and intense regional glaciations in Siberia during substages 5d and 7d were driven by extreme insolation minima. During substage 9d cooling was more gradual in response to more moderate forcing. The impact of strong glaciation is also observed in the middle of stage 15, where full glacial conditions appear to have lasted for over 30,000 yr during substages 15d, 15c, and 15b. Marine oxygen isotopic stage 11 appears to be the warmest period during the Brunhes in the Lake Baikal record, with at least three substages.

A new hypothesis is presented regarding the response of the Lake Baikal BioSi record to insolation forcing. Based on the mechanism controlling modern diatom blooms, biogenic silica production is hypothesized to be dependent on changes in the heat balance of the lake and consequently on changes in the thermal structure of the water column. This mechanism is also sensitive to short-term sub-Milankovich cooling events, such as the mid-Eemian cooling, the Montaigu event during substage 5c, and a cooling which appears to be analogous to the Montaigu event during substage 9c. The continuity of the Lake Baikal paleoclimate record, its sensitivity to orbital forcing, and its high resolution make it an excellent candidate for a new “paleoclimatic stratotype” section for continental Asia.
Late Quaternary Inland Dunes of Southern Louisiana and Arid Climate Phases in the Gulf Coast Region
Authors: Otvos Ervin G. , Price David M.
Published: September 2002

Thirty-five sand hills that form six scattered groups rise abruptly from the flat late Pleistocene coastal plain in southeastern Louisiana. New studies confirm their eolian origin. For the first time, several late Wisconsin to early Holocene episodes of arid climate conditions have been recognized and dated in this currently humid warm-temperate subtropical region. Periods of dune formation and reactivation (28,800 to 7900 yr B.P.) were determined by the thermoluminescence method. The onset of the current climate in this Gulf coastal region postdates early Holocene time. The textural and structural homogeneity of the ridge lithosomes, good sorting of their sand fraction, and the dominantly orange hues of the dune sediments contrast with the underlying yellowish–brown to light-brown sandy silts and the well-stratified, occasionally gravelly sands of the underlying alluvial Prairie Formation. Sharply defined, unconformable ridge bases; symmetrical, oval, occasionally parabolic mound shapes; and steep slopes confirm the dune origins. The dominant orientations of ridges and ridge chains clearly reflect paleowind directions. Age comparison with dunes of the lower Mississippi Valley, the northeastern–eastern Gulf of Mexico coast, and south Atlantic coastal areas confirms the existence of at least seasonally dry climate conditions from early Wisconsin to middle Holocene times. The onset of the modern humid-subtropical climate phase in this region thus dates back only to the middle Holocene.
Terminal Pleistocene/Early Holocene Environmental Change at the Sunshine Locality, North-Central Nevada, U.S.A.
Authors: Huckleberry Gary , Beck Charlotte , Jones George T. , Holmes Amy , Cannon Michael , Livingston Stephanie , Broughton Jack M.
Published: September 2002

Sedimentological, faunal, and archaeological investigations at the Sunshine Locality, Long Valley, Nevada reveal a history of human adaptation and environmental change at the last glacial–interglacial transition in North America's north-central Great Basin. The locality contains a suite of lacustrine, alluvial, and eolian deposits associated with fluvially reworked faunal remains and Paleoindian artifacts. Radiocarbon-dated stratigraphy indicates a history of receding pluvial lake levels followed by alluvial downcutting and subsequent valley filling with marsh-like conditions at the end of the Pleistocene. A period of alluvial deposition and shallow water tables (9,800 to 11,00014C yr B.P.) correlates to the Younger Dryas. Subsequent drier conditions and reduced surface runoff mark the early Holocene; sand dunes replace wetlands by 8,00014C yr B.P. The stratigraphy at Sunshine is similar to sites located 400 km south and supports regional climatic synchroneity in the central and southern Great Basin during the terminal Pleistocene/early Holocene. Given regional climate change and recurrent geomorphic settings comparable to Sunshine, we believe that there is a high potential for buried Paleoindian features in primary association with extinct fauna elsewhere in the region yet to be discovered due to limited stratigraphic exposure and consequent low visibility.
Mid-Holocene Glacier Peak and Mount St. Helens We Tephra Layers Detected in Lake Sediments from Southern British Columbia Using High-Resolution Techniques
Authors: Hallett Douglas J. , Mathewes Rolf W. , Foit Franklin F.
Published: September 2002

A Glacier Peak tephra has been found in the mid-Holocene sediment records of two subalpine lakes, Frozen Lake in the southern Coast Mountains and Mount Barr Cirque Lake in the North Cascade Mountains of British Columbia, Canada. The age–depth relationship for each lake suggests an age of 5000–508014C yr B.P. (5500–5900 cal yr B.P.) for the eruption which closely approximates the estimated age (5100–550014C yr B.P.) of the Dusty Creek tephra assemblage found near Glacier Peak. The tephra layer, which has not been reported previously from distal sites and was not readily visible in the sediments, was located using contiguous sampling, magnetic susceptibility measurements, wet sieving, and light microscopy. The composition of the glass in pumice fragments was determined by electron microprobe analysis and used to confirm the probable source of this mid-Holocene tephra layer. Using the same methods, the A.D. 1481–1482 Mount St. Helens We tephra layer was identified in sediments from Dog Lake in southeastern British Columbia, suggesting the plume drifted further north than previously thought. This high-resolution method for identifying tephra layers in lake sediments, which has worldwide application in tephrachronologic/paleoenvironmental studies, has furthered our knowledge of the timing and airfall distribution of Holocene tephras from two important Cascade volcanoes.
High-Resolution Seismic Reflection Evidence for Middle Holocene Environmental Change, Owasco Lake, New York
Authors: Mullins Henry T. , Halfman John D.
Published: September 2002

Approximately 70 km of new decimeter-resolution seismic reflection profile data from Owasco Lake, New York define a middle Holocene (∼4600 14C yr B.P.) erosion surface in the north end of the lake at water depths as great as 26 m. Beneath the lake, post-glacial sediments are up to 9 m thick and represent about 10% of the total sediment fill. Early to middle Holocene sediments, ∼6 m thick, contain biogenic gas at the south end of the basin and a large (4 km × 300 m × 15 m) subaqueous slide deposit along the east-central portion of the lake. Late Holocene sediments are thinner or absent, particularly at the north end of the lake. The middle Holocene erosion surface may have been produced by a drop in lake level. Alternatively, it may represent a change in climate during the transition between the relatively warm Holocene hypsithermal and cool neoglacial. At this time (∼4600 14C yr B.P.) circulation in Owasco Lake appears to have evolved from sluggish to active. The increased circulation, which persists today, probably resulted from atmospheric cold fronts with strong southwesterly winds that piled up water at the north end of the lake. The increased water circulation may have been ultimately driven by decreasing insolation, which produced an increased pole-to-equator thermal gradient and thus, stronger global winds that began at the transition between the hypsithermal and neoglacial.
Evidence for Lake Formation as a Response to an Inferred Holocene Climatic Transition in Brazil
Authors: Rodrigues-Filho Saulo , Behling Hermann , Irion George , Müller German
Published: September 2002

Geochemical, mineralogical, and palynological records from a Holocene sediment core 12.7 m long from Lake Silvana, southeastern Brazil, served to identify the source of detrital sediments within catchment soils. The lake basin was first flooded in the early Holocene (9400 14C yr B.P.), when a gibbsite-rich B soil horizon started to accumulate. Four distinct hydrologic phases are consistent with vegetational changes indicated by pollen data. Phases of slope instability (colluviation) and low lake level correspond to pollen-free intervals and point to a severe retreat of the vegetation cover. The rapid sedimentation of slope-wash sediments alternating with alluvial sediments appears to have formed a tributary fan 7.8 m thick that dammed the Lake Silvana Basin 8500 14C yr B.P., probably as a response to a drastic increase in precipitation rates.
Early Holocene Juniper Woodland and Chaparral Taxa in the Central Baja California Peninsula, Mexico
Authors: Rhode David
Published: September 2002

A packrat midden located in the Sierra San Francisco, Baja California Sur, Mexico, dating to ca. 10,20014C yr B.P., contains remains of California juniper (Juniperus californica) and other taxa now associated with southern California chaparral. California juniper does not occur in the Sierra San Francisco today, although “relict” populations of a few chaparral taxa still occur at higher elevations. This midden record documents the early Holocene occurrence of Baja California coniferous woodland and chaparral vegetation far south of its present distribution or its previously known extent from other fossil records. Based on modern climatic tolerances of California juniper and other taxa, central Baja California experienced a mild Mediterranean-type climate at least 5°–6°C cooler than the climate of today, with at least twice the winter precipitation the region now receives.
Historic Dead Sea Level Fluctuations Calibrated with Geological and Archaeological Evidence
Authors: Frumkin Amos , Elitzur Yoel
Published: September 2002

The Dead Sea, the Holocene terminal lake of the Jordan River catchment, has fluctuated during its history in response to climatic change. Biblical records, calibrated by radiocarbon-dated geological and archaeological evidence, reinforce and add detail to the chronology of the lake-level fluctuations. There are three historically documented phases of the Dead Sea in the Biblical record: low lake levels ca. 2000–1500 B.C.E. (before common era); high lake levels ca. 1500–1200 B.C.E.; and low lake levels between ca. 1000 and 700 B.C.E. The Biblical evidence indicates that during the dry periods the southern basin of the Dead Sea was completely dry, a fact that was not clear from the geological and archaeological data alone.