bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiocarbon Evidence for Rates of Lateral Expansion in Raised Mires in Southern Finland
Authors: Korhola Atte A.
Published: September 2002

Radiocarbon ages from the bottom peat deposits and detailed morphometric measurements at five peatlands in the boreal region of southern Finland were used to reconstruct the Holocene patterns of raised mire development. The results suggest that the areal expansion of the mires has been extremely rapid at times—up to several hundreds hectares per millennium—but the periods of more rapid expansion were not coincident among the mires. The rate of lateral extension was shown to depend mainly on the topography of the mineral substrate. Horizontal expansion did not always correlate with vertical growth. Mires expanded slowly between ca. 6000 and 4000 yr B.P., probably as a consequence of drier climatic conditions at that time. The mires also expanded slowly during the two to three recent millennia, the reason for this most probably lying in steepening of the bottom gradient toward the marginal areas of the present mires, The results point to a substantial measure of local environmental control over the lateral extension in raised mire ecosystems.
Lake Evolution in the Tengger Desert, Northwestern China, during the Last 40,000 Years
Authors: Pachur Hans-Joachim , Wünnemann Bernd , Zhang Hucai
Published: September 2002

Climatic changes inferred from lacustrine deposits and lake-level fluctuations in northwestern and central China are mainly based on paleoclimatic records from the Tibetan Plateau, while there is still a lack of data relating to the semiarid/arid desert regions of Inner Mongolia. In the Tengger Desert, different paleolake levels at Baijian Hu are documented by six paleoshorelines and stratified lake carbonates. The highest lake level occurred ca. 39,000 14C yr B.P. and prevailed over about 16,000 km2. From sediment structure, geochemical composition, and ostracods we infer humid/cool conditions until 23,000 14C yr B.P. In the northern Badanjilin Desert at Gaxan Nur/Sogu Nur, high lake levels can be deduced from mollusc-bearing paleobeaches and lake carbonates, which have been dated to 34,000 14C yr B.P. and indicate a lake that covered some 32,000 km2. After ca. 20,000 yr B.P. the climate became dry with increased eolian activity and decreasing lake levels. Reestablishment of wet conditions occurred ca. 13,000 yr B.P. The Holocene is represented by stratified lake deposits that alternate with fluvial and eolian deposits, indicating a longterm oscillating trend toward arid conditions. The existence of widespread freshwater lakes during the late Pleistocene indicates a semihumid climate without an accompanying fall in temperature to arctic conditions.
Late Holocene Coastal Plain Stratigraphy and Sea-Level History at Hanalei, Kauai, Hawaiian Islands
Authors: Calhoun R. Scott , Fletcher Charles H.
Published: September 2002

Fluvial, marine, and mixed fluvial-marine deposition on the coastal plain of Hanalei Bay on the north shore of Kauai, Hawaii, records a middle- to late-Holocene fall of relative sea level. Radiocarbon dating of the regression boundary preserved in the stratigraphy of the coastal plain documents a seaward shift of the shoreline beginning at least 4800–4580 cal yr B.P. and continuing until at least 2160–1940 cal yr B.P. Marine sands stranded in the backshore and coastal plain environment are buried by fluvial floodplain and channel sands, silts, and muds. In places, erosion at the regression contact exposed older marine sands thus increasing the hiatus at the regression disconformity. The shoreline regression is best explained as the result of a fall in relative sea level. The age and elevation of the cored regression boundary at sites that have not been influenced by erosion are consistent with a middle- to late-Holocene highstand of relative sea level as predicted by geophysical models of whole Earth deformation related to deglaciation.
Ochotona (Lagomorpha) from Late Quaternary Cave Deposits in Eastern North America
Authors: Mead Jim I. , Grady Frederick
Published: September 2002

Pikas (Ochtona)—small gnawing mammals, related to rabbits—range today throughout parts of the Northern Hemisphere, but had a wider distribution during the Pleistocene. Nine caves from northeastern North America (a region not occupied by pikas today) have Pleistocene deposits containing remains of Ochotona. We examine 526 fossil specimens (ranging in age from approximately 850,000 to 8670 yr B.P.) from five of these caves. Two morphological forms of Ochotona lived in northeastern North America during the late Pleistocene—a large species (probably O. whartoni) and a small species (probably O. princeps).Ochotona of glacial age are not necessarily indicative of talus slopes and mesic communities. O. princeps-like of the Irvingtonian of West Virginia were living with an amphibian-reptilian assemblage found in the area today, implying winters not much, if at all, colder than at present. Late glacial and postglacial change in climate south of the ice sheets in effect would have isolated Ochotona in eastern North America, where they were unable to retreat to the west or north. Whereas western pika had the option of moving up in elevation, into boreal islands, eastern forms became restricted to ever-diminishing habitats, culminating in extinction and extirpation. Radiocarbon ages imply that Ochotona lived in eastern North America during the late Pleistocene (late Rancholabrean) and into the earliest Holocene. We describe the youngest remains of Ochotona in eastern North America and the youngest for the extinct large form, O. whartoni.
Middle Pleistocene (Early Toringian) Carnivore Remains from Northern Israel
Authors: Tchernov Eitan , Tsoukala Evangelia
Published: September 2002

Seventy well-preserved fossil remains from deposits of an eroded karstic cave in the Upper Galilee of northern Israel includeUrsus deningeri(Ursidae),Canis lupuscf.mosbachensis(Canidae),Crocuta crocuta cf. praespelaea(Hyaenidae),Panthera leocf.spelaea(Felidae), andDamasp. (Cervidae). This assemblage probably dates to the Early Toringian (MQ2, Middle Pleistocene).Ursus deningeriandPanthera leo cf. spelaeahave never before been recorded south of the Taurus–Zagros mountain chain. We correlate the carnivore faunule with some Near Eastern and southern Levantine sites and assume that only a severe cold phase could have shifted these species over the Taurus–Zagros mountain chain this far to the south. Due to the relative scarcity of Middle Pleistocene assemblages, especially carnivores, in the southern Levant, the biogeographic connection between the southern Levant and the Near East is still not well known. This faunule elucidates Pleistocene biotic exchanges between Europe and the Levant during this period.
Wind-Transverse Corrugations in Pleistocene Periglacial Landscapes of Central Pennsylvania
Authors: Marsh Ben
Published: September 2002

Periglacial conditions beyond the Wisconsin glacial limit produced wind-transverse corrugations in east-central Pennsylvania. The corrugations are low, linear ridges typically several hundred meters long, 10–30 m wide, and 3–8 m above the local slope. They are composed of matrix-supported diamictons. Depending upon landscape position, the corrugations form welts, step and risers, or ground-ice-scar ramparts. The average direction normal to the corrugations is clustered at 118°/298°, similar to the late Wisconsin or early Holocene wind direction of 284° measured from a nearby fossil dune field. But the corrugations were neither eroded nor deposited by wind. Rather, they record nivation beside snow that accumulated in wind-transverse patterns. Their wide distribution implies that the region was treeless during the late Wisconsin maximum. Present discontinuities in these and other periglacial features suggest wasting of ice-rich fill in upland valleys, with consequent widening of stream channels and fan growth, at the end of periglacial time.
Evidence at Lomax, Illinois, for Mid-Wisconsin (∼40,000 yr B.P.) Position of the Des Moines Lobe and for Diversion of the Mississippi River by the Lake Michigan Lobe (20,350 yr B.P.)
Authors: Curry B. Brandon
Published: September 2002

An abrupt change in environment from a wetland to a deeper slackwater lake at 20,345 ± 85 yr B.P. occurred in a second-order valley tributary to the Mississippi River near Lomax, Illinois. The age of this shift is associated with the overflow of glacial Lake Milan and diversion of the Mississippi River from the Princeton Valley (Rock Island to Peoria) to its present course (Rock Island to St. Louis). The diversion occurred due to blockage of the Princeton Valley segment of the ancient Mississippi River by the Lake Michigan Lobe, impoundment of glacial Lake Milan, and eventual overflow of the lake southwest of Rock Island across a former drainage divide near Andalusia, Illinois. Fossil ostracode assemblages in the slackwater sediment at Lomax indicate changes in the post-diversion, full-glacial paleohydrology and based on multivariate analysis, hint at the area's paleoclimate. An older part of the succession at Lomax is consistent with glaciation in the upper Iowa River basin about 40,000 yr B.P. Aggradation of sediment rich in coarse silt is attributed to a response of the ancient Iowa River basin associated with deposition of the glacigenic Sheldon Creek Formation by the Des Moines Lobe.
Sediment Characterization and Porewater Isotope Chemistry of Quaternary Deposits from the St. Clair Delta, Ontario, Canada
Authors: Cumming John D. , Al-Aasm Ihsan S.
Published: September 2002

Walpole Island is part of a large freshwater delta located at the St. Clair River mouth in southwestern Ontario. Quaternary deposits on the island consist of Lake Nipissing to Lake St. Clair stage deltaic sediments underlain by a thick sequence of Late Wisconsin glaciolacustrine rhythmites and massive clayey till. These sediments overlie a thin freshwater aquifer resting on Paleozoic bedrock. Porewater δ18O, δD, and δ13CDICprofiles of cores taken from northern and central Walpole Island show that older (>10,000 yr B.P.), deeper glaciogenic porewaters have mixed with, and have been displaced by, younger modern surficial water. In contrast, isotopic profiles from a core taken from southern Walpole Island indicate that modern St. Clair River waters have penetrated the entire 20-m core via fractures, effectively displacing all glaciogenic porewater. Fracturing and faulting are clearly visible throughout the southern core, and their presence may be attributed to its location on the trend of the Electric Fault. These features are interpreted as the product of renewed Holocene fault movement. Porewater Na+, K+, Ca2+, and Mg2+concentration gradients are consistent with the presence of upwardly diffusing deep brine, for which the Electric Fault may serve as a conduit.
Groundwater-Mediated Response to Holocene Climatic Change Recorded by the Diatom Stratigraphy of an Ethiopian Crater Lake
Authors: Telford Richard J. , Lamb Henry F.
Published: September 2002

The diatom stratigraphy of a 23-m sediment core from Lake Tilo, a maar lake in the Ethiopian Rift Valley, provides a 10,000-yr record of lake salinity and trophic status. Until 5500 14C yr B.P., the phytoplankton was dominated by Aulacoseira granulata, with only minor changes in the abundance of other diatoms; the lake was over 50 m deep, eutrophic, and oligosaline. At 5500 yr B.P., geothermal groundwater inflow, inferred from calcite and silica deposition rates, declined abruptly, and the lake became more oligotrophic, as indicated by a rapid rise in Cyclotella stelligera. About 4500 yr B.P., lake salinity began to increase, reaching approximately its present state ca. 2500 yr B.P., but with a temporary reversal to lower salinity at 4000–3500 yr B.P. The record shows no evidence of salinity increases equivalent to early Holocene low stands of the larger river-fed Rift Valley lakes, probably because of high rates of geothermal groundwater influx. It responded to reduced rainfall at 4500 yr B.P., when levels of the larger lakes also fell, because geothermal groundwater flux had diminished 1000 year earlier, independently of climate. Because geothermal groundwaters can form a significant proportion of a crater lake's hydrological budget and dominate its salinity budget, these results show that variable geothermal groundwater flux can override lake hydrochemical response to climate change. Palaeoclimatic interpretation of palaeosalinity proxies from the sediments of volcanic crater lakes should be approached with caution.
Folsom Drought and Episodic Drying on the Southern High Plains from 10,900–10,20014C yr B.P
Authors: Holliday Vance T.
Published: September 2002

The paleoenvironments of late Pleistocene and early Holocene time on the Southern High Plains have been studied for decades, but regionally extensive or long-term, easily recoverable proxy climate indicators are difficult to find. The stratigraphy of valley fill and upland eolian deposits and stable-carbon isotope data, in addition to geographically limited paleontological data, now provide clues to the environment during this time, which includes the earliest, or Paleoindian period (∼11,200–800014C yr B.P.) of human occupation. During the Clovis occupation (∼11,200–10,90014C yr B.P.), valleys contained perennial streams. This was followed in Folsom time (10,900–10,20014C yr B.P.) by an abrupt change to lakes and ponds (with water levels fluctuating between several meters depth and no surface water) and marshes and accumulation of sheet sands on uplands, starting the earliest phase of construction of the regional dune fields. These changing conditions indicate a shift from relatively wetter to relatively drier conditions with episodic drought. Stable-C isotopes further indicate that warming characterized the Clovis–Folsom transition. During the rest of the Paleoindian period the environment was relatively cool but fluctuated between wetter and drier conditions with an overall trend toward drying that resulted in further enlargement of the dune fields and culminated in the warm, dry Altithermal beginning ∼800014C yr B.P. Clovis time probably was the wettest of any Paleoindian period in terms of runoff and spring discharge. The Folsom period was drier and was the earliest episode of regional wind erosion and eolian deposition and may have been the warmest of Paleoindian times. Evidence of a previously hypothesized “Clovis drought” in this region is sparse.
Origin of Eolian Sand Mobilization during the Past 2300 Years in the Mu Us Desert, China
Authors: Sun Jimin
Published: September 2002

Eolian sand dunes and sand sheets are extensive in the semiarid regions of northern-central China. Previous studies indicated that these eolian sands mainly formed during historical times. However, the sand sources and their reworking processes have not been well studied, and even the reasons for their occurrence are still controversial. Field investigation and sedimentary evidence indicate that both the inner Mu Us Desert and its southern marginal region, both sources of modern eolian sand, are largely associated with reworking of sands of the last glaciation. Based on geological, documentary, and archaeological data, three phases of land cultivation during the past 2300 years, together with historical droughts, high wind energy, and the easily reworked sand sources, largely account for the occurrence of active sand dunes and sand sheets in the Mu Us Desert.
A Proposed Diachronic Revision of Late Quaternary Time-Stratigraphic Classification in the Eastern and Northern Great Lakes Area
Authors: Karrow Paul F. , Dreimanis Aleksis , Barnett Peter J.
Published: September 2002

A succession of stratigraphic codes (1933, 1961, 1983) has guided attempts to refine classifications and naming of stratigraphic units for Quaternary deposits of the Great Lakes region. The most recent classifications for the late Quaternary of the Lake Michigan lobe (1968) and the eastern Great Lakes (1972) have been widely used, but later work has created the need for revision. An attempt has been made to integrate the two previous classifications following the diachronic system of the 1983 Code of Stratigraphic Nomenclature. A new nomenclature for the higher, more broadly recognized units was presented in 1997. We here present the diachronic nomenclature for finer subdivisions recognized in the eastern and northern Great Lakes. Following the interglacial Sangamon Episode, the three parts of the Wisconsin Episode are further subdivided as follows: the Ontario Subepisode (former Early Wisconsinan) comprises the Greenwood, Willowvale, and Guildwood phases; the Elgin Subepisode (former Middle Wisconsinan) comprises the Port Talbot, Brimley, and Farmdale phases; and the Michigan Subepisode (former Late Wisconsinan) consists of Nissouri, Erie, Port Bruce, Mackinaw, Port Huron, Two Creeks, Onaway, Gribben, Marquette, Abitibi, and Driftwood phases. Succeeding interglacial time to the present is the Hudson Episode.
Late Quaternary Geology of the Middle Gila River, Gila River Indian Reservation, Arizona
Authors: Waters Michael R. , Ravesloot John C.
Published: September 2002

Stratigraphy and dating provide an 18,000 yr record of erosion and deposition by the middle Gila River. Prior to 18,000 cal yr B.P., the Gila River cut into its floodplain and created a deep, wide channel. Sand and gravel accumulated within this channel until 4250–4400 cal yr B.P. By this time, the channel of the Gila River was narrow and deep. Around 5000 cal yr B.P., fine-grained sediments began to accumulate on the floodplain. At 800–950 cal yr B.P., there was a major period of channel widening. After this erosional episode, the channel again narrowed as it filled with sand and gravel until around 200 cal yr B.P. On the floodplain, deposition continued from about 5000 cal yr B.P. to 500 cal yr B.P. A period of stability and soil formation occurred on the floodplain between 500 and 200 cal yr B.P., after which overbank deposition resumed and buried the soil. Channel widening again occurred in the late 19th century. The changes observed in the sedimentologic history of the Gila River show that during the late Pleistocene, the Gila River was a competent stream capable of carrying and depositing coarse sediment loads. Later deposition of sand and gravel during the first half of the Holocene implies an increase in sediment yield from upstream watersheds. Changes during the last 4000 years reflect the response of the river to climatic perturbations, the timing of large floods, internal landscape thresholds, and human impacts.
A Quantitative Holocene Climatic Record from Diatoms in Northern Fennoscandia
Authors: Korhola Atte , Weckström Jan , Holmström Lasse , Erästö Panu
Published: September 2002

A diatom-based calibration model for predicting summer temperatures was developed using climatically sensitive subarctic lakes in northern Fennoscandia. The model was applied to a sediment core from a treeline lake to infer trends in Holocene climate. The record exhibits long-term variations, as well as a series of shorter-term fluctuations on a time scale of centuries. Summers were warmest in the area about 6200 cal yr B.P. and featured distinct cooling episodes around 8300, 7200, 4200, 3000, and 400 cal yr B.P., most of these coinciding with some known climate events (e.g., the 8200 cal yr B.P. event and the Little Ice Age). The similarity of the observed shifts with the pacings of climate events from marine and ice-core records represents evidence for coupled ocean–atmosphere forcing of the regional climate.
Changes in the Bathymetry and Volume of Glacial Lake Agassiz Between 11,000 and 9300 14C yr B.P.
Authors: Leverington David W. , Mann Jason D. , Teller James T.
Published: September 2002

The volume and surface area of glacial Lake Agassiz varied considerably during its 4000-year history. Computer models for seven stages of Lake Agassiz were used to quantify these variations over the lake's early history, between about 11,000 and 9300 14C yr B.P. (ca. 13,000 to 10,300 cal yr B.P.). Just after formation of the Herman strandlines (ca. 11,000 14C yr B.P.), the volume of Lake Agassiz appears to have decreased by >85% as a consequence of the abrupt rerouting of overflow to its eastern outlet from its southward routing into the Mississippi River basin. This drainage released about 9500 km3 of water into the North Atlantic Ocean via the Great Lakes and Gulf of St. Lawrence. Following closure of this eastern routing of overflow, the lake reached its maximum size at about 9400 14C yr B.P. with an area of >260,000 km2 and a volume of >22,700 km3. A second major reduction in volume occurred shortly after that, when its volume decreased >10% following the opening of the Kaiashk outlet to the east into the Great Lakes, and 2500–7000 km3 of water was released into the North Atlantic Ocean. These discharges may have affected ocean circulation and North Atlantic Deep Water production.
Trends in River Flow Affecting the Northeastern Reach of the San Francisco Bay Estuary over the Past 7000 Years
Authors: Goman Michelle , Wells Lisa
Published: September 2002

A variety of stratigraphic analyses (particle grain size, iron concentration, loss on ignition, and macrofossils) from sediments obtained from two marsh sites are used to reconstruct a middle to late Holocene record of stream flow into San Francisco Bay. Browns Island, a freshwater/brackish site, is located at the confluence of the Sacramento and San Joaquin rivers and is dominated by stands ofScirpus americanus.Peyton Hill is a brackish site located near Carquinez Straits and is dominated by stands ofScirpus robustus.Twenty-five AMS14C dates provide chronostratigraphic control. During the Holocene, discharge from the Sacramento and San Joaquin rivers was broadly comparable to modern flows; however, an extended period of higher flow began 3800 cal yr B.P. and continued for almost two millennia. At this time Browns Island supportedPhragmites communis,a freshwater species, and Peyton Hill supportedS. americanus.At least two floods, recognized by discrete increases in sand and silt, occurred at 3600 and 530 cal yr B.P.
Holocene Relative Sea Level Changes along the Seattle Fault at Restoration Point, Washington
Authors: Sherrod Brian L. , Bucknam Robert C. , Leopold Estella B.
Published: September 2002

At a marsh on the hanging wall of the Seattle fault, fossil brackish water diatom and plant seed assemblages show that the marsh lay near sea level between ∼7500 and 1000 cal yr B.P. This marsh is uniquely situated for recording environmental changes associated with past earthquakes on the Seattle fault. Since 7500 cal yr B.P., changes in fossil diatoms and seeds record several rapid environmental changes. In the earliest of these, brackish conditions changed to freshwater ∼6900 cal yr B.P., possibly because of coseismic uplift or beach berm accretion. If coseismic uplift produced the freshening ∼6900 cal yr B.P., that uplift probably did not exceed 2 m. During another event about 1700 cal yr B.P., brackish plant and diatom assemblages changed rapidly to a tidal flat assemblage because of either tectonic subsidence or berm erosion. The site then remained a tideflat until the most recent event, when an abrupt shift from tideflat diatoms to freshwater taxa resulted from ∼7 m of uplift during an earthquake on the Seattle fault ∼1000 cal yr B.P. Regardless of the earlier events, no Seattle fault earthquake similar to the one ∼1000 cal yr B.P. occurred at any other time in the past 7500 years.
Late- and Postglacial Sea-Level Change and Paleoenvironments in the Oder Estuary, Southern Baltic Sea
Authors: Müller Anne
Published: September 2002

Knowledge of sea-level change in the southern Baltic Sea region is important for understanding the variations in late Pleistocene and Holocene sea-level change across northern Europe. These variations are a consequence of the response of the Earth's crust to the deglaciation of Fennoscandia and of the water added to the oceans from the melting of all Pleistocene ice sheets. The sedimentological and geochemical composition of five sediment cores from the lagoonal Oder Estuary offers new observational evidence for sea-level change and coastal development in the southern Baltic Sea region. The combined use of several geochemical proxies (organic carbon, nitrogen, calcium carbonate and biogenic opal contents, Corg/S and Corg/N ratios, δ13C values of organic matter, and δ15N values) is a new approach for the study area. The chemical evidence of this multiproxy approach allows clear identification of several stages in the development of the lagoonal environment: postglacial lake stages with sandy sedimentation during the Older Dryas and the Allerød stades, lacustrine phases with high autochthonous productivity during the Atlantic stade, terrestrial stages with peat formation at the beginning of the Subboreal stade, sedimentation as a result of marine transgression, and brackish sedimentation after the formation of sand spits and barrier islands during the Subatlantic stade. The stages are the result of regional sea-level change owing to complex shoreline development. They support the tentative sea-level curve proposed nearly 20 years ago for the region. In addition, changes in Oder River input in response to climate conditions is monitored. Whereas high terrigenous input of organic matter from the Oder River occurred during periods of humid climate during the Allerød, Atlantic, and Subatlantic stades, Oder River discharge decreased with drier and cooler climate conditions during the Subboreal stade. Furthermore, the geochemical evidence points to local anomalies such as the significance of river input and additional sulfate supply into the Oder lagoon for the composition of the sediments. Overall, the results provide a framework for future studies, which would allow for a more detailed comparison with other, similar environments.
Paleovegetation Simulations of Lowland Amazonia and Implications for Neotropical Allopatry and Speciation
Authors: Cowling Sharon A. , Maslin Mark A. , Sykes Martin T.
Published: September 2002

Paleovegetation modeling simulations of the lowland Amazon basin were made to assess the relative importance of glacial climate and atmospheric CO2 for altering vegetation type and structure, as well as to explore the potential physiological mechanisms underlying these ecosystem-level responses. Modeling results support the view that widespread invasion of grasslands into the Amazon lowlands during the last glaciation was not likely. Glacial cooling was probably responsible for maintaining glacial forest cover via its effects in reducing photorespiration and decreasing evapotranspiration, which collectively improve plant carbon and water relations. Modeling results confirm that leaf area index (LAI), a common proxy for canopy density, is highly sensitive to independent and interactive changes in climate and low concentration of atmospheric CO2, and the results show considerable region-to-region variation during the last glaciation. Heterogeneous variations in glacial vegetation LAI may have promoted allopatric speciation by geographically isolating species (called vicariance) in the forest (sub)canopy. The proposed vicariance hypothesis incorporating spatial variations in canopy density conforms to many of the essential tenets addressed by previous neotropical speciation models, but also helps to overcome some of their inconsistencies.
Paleoecology and Geochronology of Uruguayan Coastal Marine Pleistocene Deposits
Authors: Martı́nez Sergio , Ubilla Martı́n , Verde Mariano , Perea Daniel , Rojas Alejandra , Guérèquiz Rosario , Piñeiro Graciela
Published: September 2002

Minimum radiocarbon ages of marine Pleistocene molluscs from Uruguay range from 29,500±600 to 35,500±1900 14C yr B.P. Because knowledge of the marine Quaternary stratigraphy of Uruguay remains inadequate, no attempt is made to correlate between these deposits and recognized lithostratigraphic units. Analysis of the temperature and salinity ranges of the various molluscs suggests the establishment of a poly-euhaline fauna that inhabited waters warmer than present at the same latitude. This is supported by a northward retreat in the recent distribution of Chrysallida cf. C. gemmulosa, Nioche subrostrata, and probably Anomalocardia brasiliana. These marine Pleistocene deposits can probably be correlated with the last interglaciation (oxygen-isotopic substage 5e). At that time the fluvial-marine front of the Rio de la Plata was displaced much further northwestward than previously supposed. Chrysallida cf. C. gemmulosa and Limaria sp. are recorded in Uruguayan Quaternary deposits for the first time.
Dependence of Near-Surface Magnetic Susceptibility on Dust Accumulation Rate and Precipitation on the Chinese Loess Plateau
Authors: Porter Stephen C. , Hallet Bernard , Wu Xihao , An Zhisheng
Published: September 2002

Magnetic susceptibility (MS) of surface sediment varies systematically across the Loess Plateau in central China, decreasing exponentially from >200×10−8 m3/kg at the northern margin of the Qinling Shan to ≤30×10−8 m3/kg near the southern margin of the Mu Us Desert. MS correlates highly with loess median grain size (r2=0.79), which decreases south-southeastward across the plateau. It also correlates with mean annual temperature (MAT) and mean annual precipitation (MAP) (r2=0.58 and 0.60, respectively), and with their product MAT×MAP (r2=0.83), which is considered a measure of potential pedogenic activity. Because regional isopleths depicting grain size and the primary meteorological parameters are nearly parallel, it is difficult to determine their relative influence on MS. A simple MS model, based on the observed spatial variation in loess thickness, permits quantitative assessment of the effect of the dust accumulation rate on the MS signal of surface sediment and isolates the likely role of climate in the production of magnetic minerals. The model suggests that 84% of the loess MS variance is dictated by the diluting effect of dust and 10–11% is associated with meteorological factors, primarily precipitation. The observed and modeled relationships support hypotheses that attribute variations in MS in the loess-paleosol succession to varying rates of dust deposition and in situ production of magnetic minerals in the accretionary soils, both of which are controlled by monsoon climate.
Late Quaternary Diatom Assemblages from Prydz Bay, Eastern Antarctica
Authors: Taylor Fiona , McMinn Andrew
Published: September 2002

The paleo-depositional environment of inner Prydz Bay, East Antarctica, has been reconstructed for the past 21,320 14C yr B.P., using diatom assemblages and sediment facies from a short, 352-cm-long gravity core. Between 21,320 and 11,650 14C yr B.P., compact tillite and diamicton are present in the core, and diatom frustules are rare to absent. These data suggest that an ice sheet grounded over the site during the last glacial maximum. Following glacial retreat, siliceous muddy ooze was deposited, from 11,650 to 2600 14C yr B.P., in an open marine setting. During this stage, diatom frustules are abundant and well preserved, and Thalassiosira antarctica resting spores and Fragilariopsis curta dominate the assemblage. This assemblage suggests open marine deposition in an environment where the spatial and temporal distribution of sea ice is less than today. Since 2600 14C yr B.P., sea-ice and ice-edge diatom species have become more abundant, and neoglacial cooling is inferred. The assemblage is similar to that forming currently in Prydz Bay, where sea ice is absent (<10% cover) for 2–3 months of the year and permanent ice edge and/or multiyear sea ice remains in close proximity to the site.
Two Tephra Layers Bracketing Late Holocene Paleoecological Changes in Northern Germany
Authors: van den Bogaard Christel , Dörfler Walter , Glos Rainer , Nadeau Marie-Josée , Grootes Pieter M. , Erlenkeuser Helmut
Published: September 2002

Paleoecological records from two Holocene peat bogs in northern Germany are linked by two microscopic volcanic ash layers, correlated by petrology and geochemistry to explosive volcanism on Iceland. The younger “Microlite tephra” cannot be correlated to any known eruption, while the older tephra layer is identified as a deposit of the Hekla 3 eruption. The tephra layers are dated by an age–depth regression of accelerator mass spectrometry 14C ages that have been calibrated and combined in probability distributions. This procedure gives an age of 730–664 cal yr B.C. for the “Microlite tephra” event and 1087–1006 cal yr B.C. for the Hekla 3 event. Accordingly, the tephra layers were deposited during the late Bronze Age. At this time, human settlement slowly increased pressure on the environment, as indicated by changes in woodland pollen composition at the two bogs. The tephra-marker horizons further show that the palynologically defined transition from the Subboreal to the Subatlantic Period is synchronous in the investigated area. However, the macroscopic visible marker in peat, the change from fibrous to sapric peat, the “Schwarztorf-Weißtorf-Kontakt,” is asynchronous. Bog vegetation did not immediately react in unison to a climatic change at this pollen zone boundary; instead, the timing of vegetation change depended on the location within the bog.
Glibenclamide binding to sulphonylurea receptor subtypes: dependence on adenine nucleotides
Authors: Hambrock Annette , Löffler‐Walz Cornelia , Quast Ulrich
Published: September 2002

ATP‐sensitive K+ channels are composed of pore‐forming subunits Kir6.2 and of sulphonylurea receptors (SURs); the latter are the target of the hypoglycaemic sulphonylureas like glibenclamide. Here, we report on the negative allosteric modulation by MgATP and MgADP of glibenclamide binding to SUR1 and to SUR2 mutants with high glibenclamide affinity, SUR2A(Y1206S) and SUR2B(Y1206S).

ATP, in the presence of an ATP‐regenerating system to oppose hydrolysis during incubation, inhibited glibenclamide binding to SUR1 and SUR2B(Y1206S) by ∼60%, to SUR2A(Y1206S) by 21%). Inhibition curves for the SUR2(Y1206S) isoforms were monophasic with IC50 values of 5–10 μM; the curve for SUR1 was biphasic (IC50 values 4.7 and 1300 μM).

Glibenclamide inhibition curves for ADP, performed in the presence of an ATP‐consuming system to oppose ATP formation from ADP, were generally shifted rightwards and showed positive cooperativity, in particular with the SUR2(Y1206S) isoforms.

In the absence of the coupled enzyme systems, inhibition curves of MgATP or MgADP were generally shifted leftwards. This indicated synergy of MgATP and MgATP in acting together.

Coexpression of SUR1 and SUR2B(Y1206S) with Kir6.2 reduced both potency and efficacy of ATP in inhibiting glibenclamide binding; this was particularly marked for Kir6.2/SUR1.

The data show (a) that the inhibitory effects of ATP and ADP on glibenclamide binding differ from one another, (b) that they depend on the SUR subtype, and (c) that they are weakened by coexpression with Kir6.2.

British Journal of Pharmacology (2002) 136, 995–1004. doi:10.1038/sj.bjp.0704801
Evidence that the novel imidazoline compound FT005 is anα2‐adrenoceptor agonist
Authors: Slough Scott , Guillaumet Gerald , Taberner Peter V
Published: September 2002

The aim of this study was to determine whether the hyperglycaemic action of the novel imidazoline compound FT005 could be mediated by activation of α2‐adrenoceptors, using a variety of in vivo and in vitro methods including radioligand binding.

FT005 produced a dose‐dependent increase in blood glucose levels of CBA/Ca mice (0.125–25 mg kg−1, i.p.). The time course of this hyperglycaemic effect matched that of adrenaline (1 mg kg−1) more closely than glucagon (1 mg kg−1) or the KATP channel opener diazoxide (25 mg kg−1). The hyperglycaemic effect of FT005 (1 mg kg−1) was significantly reduced by the α2‐adrenoceptor antagonist rauwolscine (0.5 mg kg−1).

FT005 produced a significant reduction in plasma insulin levels of mice 30 min after administration. The hyperglycaemic effect of FT005 (25 mg kg−1), although still present, was significantly less in fasted mice in which insulin levels are lower, suggesting that a reduction of insulin secretion contributes to the action of FT005.

When studied in the mouse isolated vas deferens preparation, FT005 produced a complete inhibition of neurogenic contractions, which was blocked by rauwolscine. This is consistent with activation of pre‐synaptic α2‐adrenoceptors.

In radioligand binding studies FT005 completely displaced the α2‐adrenoceptor antagonist [3H]‐RX821002 from mouse whole brain homogenates. The displacement was best described by a two‐site model of interaction comprising high and low affinity components.

The results indicate that FT005 is an agonist at α2‐adrenoceptors. A reduction in insulin secretion contributes to the hyperglycaemic action of FT005, although an additional mechanism can not be excluded.

British Journal of Pharmacology (2002) 136, 1049–1057. doi:10.1038/sj.bjp.0704810
Studies of GABAB receptors labelled with [3H]‐CGP62349 in hippocampus resected from patients with temporal lobe epilepsy
Authors: Princivalle A P , Duncan J S , Thom M , Bowery N G
Published: September 2002

The aim of this study was to investigate the binding of a novel GABAB receptor radioligand, [3H]‐CGP62349, to human post‐mortem control and epileptic hippocampal sections using quantitative receptor autoradiography. Utilizing human control hippocampal sections it was shown that [3H]‐CGP62349 bound with high affinity (KD 0.5 nM) to this tissue.

Hippocampal slices from surgical specimens obtained from patients with hippocampal sclerosis (HS) and temporal lobe epilepsy (TLE) were compared with neurologically normal post‐mortem control subjects for neuropathology and GABAB receptor density and affinity. Neuronal loss was observed in most of the hippocampal subregions, but in the subiculum no significant difference was detected.

The localization of GABAB receptors with the antagonist [3H]‐CGP62349 in human control hippocampal sections supported and extended earlier studies using the agonist ligand [3H]‐GABA.

The kinetics of binding to the GABAB receptor in human hippocampus using this novel compound was comparable to previous data obtained in rat hippocampal membranes.

GABAB receptor density (Bmax) was significantly reduced in CA3, hilus, and dentate gyrus (DG); the affinity was increased exclusively in DG. The trend is identical in all the hippocampal subregions with the agonist and the antagonist, although significant differences with the antagonist where recorded in CA3 and hilus, whereas with the agonist a significant reduction was reported in all of the hippocampal subfields.

GABAB receptor expression per remaining neuron appeared significantly increased in CA3 and hilus. These results suggest altered GABAB receptor function may occur in human TLE, possibly as a result of synaptic reorganization, and may contribute to epileptogenesis.

British Journal of Pharmacology (2002) 136, 1099–1106 doi:10.1038/sj.bjp.0704812
Role of the endocannabinoid system in MDMA intracerebral self‐administration in rats
Authors: Braida Daniela , Sala Mariaelvina
Published: September 2002

I.c.v. self‐administration of MDMA (0.01–2 μg per infusion), alone and in combination with CP 55,940 (0.4 μg infusion−1), was studied on an operant responding procedure. On the basis of individual preference for one of two levers, developed during training, rats were allowed to self‐administer vehicle from the preferred lever and MDMA from the other. Pressings on the MDMA associated‐lever, except for the maximal unit dose, progressively increased. The combination of CP 55,940 with MDMA (1 μg infusion−1) reduced the number of drug‐associated lever pressings compared to the single drugs. Pre‐treatment with SR 141716A (0.5 mg kg−1 i.p.), 15 min before each daily session, significantly increased MDMA self‐administration. These findings suggest that MDMA self‐administration is under endogenous tonic control by the endocannabinoid system.

British Journal of Pharmacology (2002) 136, 1089–1092. doi:10.1038/sj.bjp.0704825
Comparative pharmacology of rat and human α7 nAChR conducted with net charge analysis
Authors: Papke Roger L , Porter Papke Julia K
Published: September 2002

Pharmacological studies of α7 nicotinic acetylcholine receptors are confounded by the fact that rapid desensitization to high agonist concentration causes α7 peak responses to occur well in advance of complete solution exchange. For this reason, peak currents are an invalid measure of response to applied agonist concentrations. We show that results comparable to those that have been corrected for instantaneous concentration are obtained if net charge is used as the measure of receptor response.

Dose response curves obtained with these methods indicate that α7 receptors are approximately 10 fold more sensitive to agonist than previously reported. The agonists, ACh, choline, cytisine, GTS‐21, 4OH‐GTS‐21 and 4‐MeO‐CA have the same rank order potency for both human and rat receptors: 4‐MeO‐CA > 4OH‐GTS‐21 > GTS‐21 > cytisine > ACh > choline. However, differences in efficacy exist between rat and human receptors. GTS‐21 is more efficacious for rat than human α7 receptors and cytisine more efficacious for human than rat α7 receptors.

Choline is the least potent agonist for both human and rat α7, with a potency approximately 10 fold lower than that of ACh. While the EC50 for the activation of α7 receptors by choline (400–500 μM) is outside the normal physiological range (10–100 μM), choline can nonetheless produce detectable levels of channel activation in the physiological concentration range. Since these concentrations are relatively non‐desensitizing, the contribution of choline‐activated α7 receptor current may play a significant role in the regulation of calcium homeostasis in α7‐expressing neurons.

British Journal of Pharmacology (2002) 137, 49–61. doi:10.1038/sj.bjp.0704833
Nitric oxide synthase inhibitors can antagonize neurogenic and calcitonin gene‐related peptide induced dilation of dural meningeal vessels
Authors: Akerman S , Williamson D J , Kaube H , Goadsby P J
Published: September 2002

The detailed pathophysiology of migraine is beginning to be understood and is likely to involve activation of trigeminovascular afferents.

Clinically effective anti‐migraine compounds are believed to have actions that include peripheral inhibition of calcitonin gene‐related peptide (CGRP) release from trigeminal neurones, or preventing dural vessel dilation, or both. CGRP antagonists can block both neurogenic and CGRP‐induced dural vessel dilation.

Nitric oxide (NO) can induce headache in migraine patients and often triggers a delayed migraine. The initial headache is thought to be caused via a direct action of the NO–cGMP pathway that causes vasodilation by vascular smooth muscle relaxation, while the delayed headache is likely to be a result of triggering trigeminovascular activation. Nitric oxide synthase (NOS) inhibitors are effective in the treatment of acute migraine.

The present studies used intravital microscopy to examine the effects of specific NOS inhibitors on neurogenic dural vasodilation (NDV) and CGRP‐induced dilation.

The non‐specific and neuronal NOS (nNOS) inhibitors were able to partially inhibit NDV, while the non‐specific and endothelial NOS (eNOS) inhibitors were able to partially inhibit the CGRP induced dilation.

There was no effect of the inducible NOS (iNOS) inhibitor.

The data suggest that the delayed headache response triggered by NO donors in humans may be due, in part, to increased nNOS activity in the trigeminal system that causes CGRP release and dural vessel dilation.

Further, eNOS activity in the endothelium causes NO production and smooth muscle relaxation by direct activation of the NO–cGMP pathway, and may be involved in the initial headache response.

British Journal of Pharmacology (2002) 137, 62–68. doi:10.1038/sj.bjp.0704842
Characterization of the β‐adrenoceptor subtype involved in mediation of glucose transport in L6 cells
Authors: Nevzorova Julia , Bengtsson Tore , Evans Bronwyn A , Summers Roger J
Published: September 2002

The receptor that mediates the increase in glucose transport (GT) in response to β‐adrenoceptor (β‐AR) agonists was characterized in the rat skeletal muscle cell line L6, using the 2‐deoxy‐[3H]‐D‐glucose assay.

The β3‐AR agonist BRL37344 (pEC50=6.89±0.21), the β‐AR agonist isoprenaline (pEC50=8.99±0.24) and the β2‐AR agonist zinterol (pEC50=9.74±0.15) increased GT as did insulin (pEC50=6.93±0.15). The highly selective β3‐AR agonist CL316243 only weakly stimulated GT.

The pKB values calculated from the shift of the pEC50 values of the agonists in the presence of the β1‐AR selective antagonist CGP 20712A or the β3‐AR selective antagonist SR 59230A were not indicative of activation of β1‐ or β3‐ARs. Only (−)‐propranolol and the β2‐AR selective antagonist ICI 118551 caused marked rightward shifts of CR curves to isoprenaline (pKB=10.2±0.2 and 9.6±0.3), zinterol (pKB=9.0±0.1 and 9.4±0.3) and BRL 37344 (pKB=9.4±0.3 and 8.4±.2), indicating participation of β2‐ARs.

The pharmacological analysis was supported by reverse transcription and polymerase chain reaction analysis of L6 mRNA, which showed high levels of expression of β2‐AR but not β1‐ or β3‐AR in these cells.

Forskolin and dibutyryl cyclic AMP produced negligible increases in GT while the phosphatidylinositol‐3 kinase inhibitor, wortmannin, significantly decreased both insulin‐ and zinterol‐stimulated GT, suggesting a possible interaction between the insulin and β2‐AR pathways.

This study demonstrates that β2‐ARs mediate the increase in GT in L6 cells to β‐AR agonists, including the β3‐AR selective agonist BRL 37344. This effect does not appear to be directly related to increases in cyclic AMP but requires P13K.

British Journal of Pharmacology (2002) 137, 9–18. doi:10.1038/sj.bjp.0704845
Allogeneic stem cell transplantation of adult chronic myelomonocytic leukaemia. A report on behalf of the Chronic Leukaemia Working Party of the European Group for Blood and Marrow Transplantation (EBMT)
Authors: Kröger Nicolaus , Zabelina Tatjana , Guardiola Philipe , Runde Volker , Sierra Jorge , Van Biezen Anja , Niederwieser Dietger , Zander Axel R. , De Witte Theo
Published: September 2002

Summary. We report the results of 50 allogeneic transplantations from related (n = 43) or unrelated (n = 7) donors, performed for chronic myelomonocytic leukaemia (CMML) in 43 European centres. The median age at transplant was 44 years (range 19–61). Eighteen patients had excess blasts ranging from 5% to 30% at the time of transplantation. Two graft failures were observed (4%). Neutrophil (> 0·5 × 109/l) and platelet engraftment (> 50 × 109/l) was reached after a median of 17 d (range 11–38) and 27 d (range 11–48) respectively. Acute graft‐versus‐host disease (GvHD grade II–IV was seen in 35% of patients, while 20% developed severe‐acute GvHD grade III/IV. Twenty‐six patients (52%) died of treatment‐related causes. After a median follow‐up of 40 months (range 11–110), the 5‐year‐estimated overall survival was 21% (95% CI: 15–27%) and the 5‐year‐estimated disease‐free survival (DFS) was 18% (95% CI: 13–23%). Earlier transplantation in the course of disease, male donor, use of unmanipulated grafts, allogeneic transplantation and occurrence of acute GvHD favoured better DFS, but did not reach statistical significance. The 5‐year estimated probability of relapse was 49%. The data showed a trend for a lower relapse probability of acute GvHD grade II–IV (24% vs 54%; P = 0·07), and for a higher relapse rate in patients with T cell‐depleted grafts (62% vs 45%), suggesting a ‘graft‐versus‐CMML effect’.