bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quaternary Sea Level Fluctuations on a Tectonic coast: New 230Th/234U Dates from the Huon Peninsula, New Guinea
Authors: Bloom A.L. , Broecker W.S. , Chappell J.M.A. , Matthews R.K. , Mesolella K.J. 
Published: December 2004

Emerged coral reef terraces on the Huon Peninsula in New Guinea were reported in a reconnaissance dating study by Veeh and Chappell 1970. Age definition achieved was not good for several important terraces, and we report here a series of new 230Th/234U dates, which further clarify the history of late Quaternary eustatic sea level fluctuations. More than 20 reef complexes are present, ranging well beyond 250,000 yr old: we are concerned with the seven lowest complexes. Major reef-building episodes dated by 30Th/234U are reef complex I at 5–9 ka (kilo anno = 1000 yr), r.c. IIIb at 41 ka (four dates), r.c. IV at 61 ka (four dates), r.c. V at 85 ka (two dates), r.c. VI at 107 ka (two dates), and r.c. VII at 118–142 ka. Complex II was previously dated by 14C at 29 ka: this age has not yet been confirmed, and may be only a lower limit. The reef crests were built during or immediately before intervals of sea level maxima, when rates of rising sea level and tectonic uplift briefly coincided. The culmination of each reef-building episode was only a few thousand years in duration, and multiple dates from the same reef complex generally group within the statistical errors of the individual dates.Several methods can be used to estimate the altitude of each sea level maximum relative to present sea level. The least complicated is to calculate mean tectonic uplift rate for each profile of the terraces, and use the mean rate to calculate the tectonic displacement of each dated reef complex on that profile. The difference between the present altitude of a reef complex and its calculated tectonic uplift gives the paleosea level at the time the reef grew. We estimate uplift rates for six surveyed sections by calibrating against published paleosea level estimates from Barbados and elsewhere, viz 125 ka, paleosea at +6 m; 103 ka, −15 m; 82 ka, −13 m. For each section the individual uplift rates for reefs V, VI, and VIIb are within 5% of their section means. Using the mean rates. paleosea level estimates for reef crests II, IIIB, and IV are made for each section. Consistency of estimates between sections is good, giving −28 m for the 60 ka paleosea level, around −38 m for the 42 ka level and −41 m for the 28 ka level (if the age is older the paleosea level would be lower. Using the mean uplift rates, the 82 ka and 103 ka paleosea levels are also estimated for each section: all individual estimates are plotted graphically, and a sea level curve drawn. The reef stratigraphy indicates sea level lowerings between each dated reef crest: the crests probably represent the interstadials of the Wisconsin (Würm, Weichsel) Glaciation, and intervening lower levels correspond to stadials. Since the last time of eustatic sea level higher than the present (about 125 ka), five sea level maxima occurred at roughly 20-ka intervals, none being as high as the present.
A Study of Late Pleistocene Loess Deposits, South Canterbury, New Zealand Part II. Paleosols and their Stratigraphic Implications
Authors: Tonkin P.J. , Runge E.C.A. , Ives D.W. 
Published: December 2004

Examination of loess columns in coastal South Canterbury, New Zealand, and the recognition of paleosols with comparable morphology to surface soils allowed the division of the loess column into six members. The upper loess members 1–4 are grouped into a proposed Dashing Rocks Formation. This commonly overlies an erosion surface on Timaru Basalt, but in some situations is underlain by loess member 5 and mixed loess and weathered basalt member 6. The paleosol developed on loess member 5, on both morphological and chemical evidence, is indicative of a period of soil formation of longer duration or greater intensity than is indicated by the overlying paleosols or surface soils. Therefore members 5 and 6 are grouped into a separate formation.A radiocarbon chronology for loess members 1 and 2 of the Dashing Rocks Formation, suggests loess accumulation phases from 9900 to 11,800 and prior to 31,000 radiocarbon yr BP, followed by periods of soil formation and contemporary peat development in surface depressions.A hypothesis is presented suggesting that at least loess members 1 and 2 of the Dashing Rocks Formation accumulated during periods of glacial recession which in turn precipitated fluvial and eolian erosion, transport and redeposition of fluvioglacial deposits. The periods of soil development indicated by the paleosols were initiated during warm interstadial conditions and continued throughout the cooling of the following stadial. Such an interpretation has its parallels in the northern hemisphere but is in slight disagreement with previous glacial and fluvioglacial chronologies accepted in New Zealand.
Postglacial Forest Patterns Associated with till and Outwash in Northcentral Upper Michigan
Authors: Brubaker Linda B. 
Published: December 2004

Pollen analysis of lake sediments reveals that small areas of till and outwash in northcentral Upper Michigan have influenced plant distributions throughout postglacial time. Each substrate has different textural characteristics. Modern forest communities form a mosaic, with jack pine woodlands occupying the medium sands of the Yellow Dog Plains outwash and white pine-hardwood communities on both till and outwash soils in the Michigamme Highlands to the south.The analysis of modern pollen samples from 21 lakes within the area indicates that pollen can be used to study the distribution of local vegetation in relation to substrate type. Fossil pollen from three of the lakes documents the character of ancient forest on Yellow Dog outwash, Michigamme outwash, and Michigamme till.Unique boreal communities occupied each area immediately after deglaciation. Between 8000 and 7000 y.a., white pine and maples migrated into the study area and replaced jack pine in forests on the Highlands, but not on the Plains. Jack pine has continued to occupy the Plains since early postglacial time. White pine reached highest densities on Michigamme outwash, and deciduous trees increased primarily on till during the presumably dry climates which existed 8000-5000 yr BP. As the climate became more mesic, forests on the Highlands changed, so that by 3000 yr BP the communities on Michigamme outwash and till were indistinguishable on the basis of pollen. Present-day forest patterns of the area became established at that time.Pollen influx rates, measured at each lake, generally support interpretations based on pollen percentages and were similar to values reported elsewhere. Variations in influx values are within the range expected for the method.
The Present Flora and Vegetation of the Moraines of the Klutlan Glacier, Yukon Territory, Canada: A Study in Plant Succession
Authors: Birks H. J. B. 
Published: December 2004

AbstractThe flora and vegetation of six ice-cored moraines of the Klutlan Glacier were analyzed in 65 plots by European plant-sociological techniques. The age of each plot was estimated from annual growth rings of shrubs or trees in the plots. Nine major vegetation types are distinguished: Crepis nana, Dryas drummondii, Hedysarum mackenzii, Hedysarum-Salix, Salix-Shepherdia canadensis, Picea-Salix, Picea-Arctostaphylos, Picea-Ledum, and Picea-Rhytidium. These contain plants aged 2–6, 9–23, 10–20, 24–30, 32–58, 58–80, 96–178, 177–240, and >163- >339 yr, respectively. Six other vegetation types are described from windthrow areas, drainage channels, volcanic tephra slopes, lake margins, fens, and drained lakes. The major vegetation types reflect a vegetational succession related to moraine age and stability, with the Crepis nana type as the pioneer vegetation developing through the other vegetation types to the Picea-Rhytidium type on the oldest moraines. Changes in species diversity and soil development, particularly humus accumulation, parallel the vegetational succession. This succession differs from patterns of revegetation of deglaciated landscapes in Alaska and British Columbia today and in Minnesota in late-Wisconsin times because of differences in climate, plant migration, and local ecology.
Limnology of the Klutlan Moraines, Yukon Territory, Canada
Authors: Whiteside M. C. , Bradbury J. Platt , Tarapchak S. J. 
Published: December 2004

AbstractLakes of the Klutlan moraines originate by down-melting of stagnant ice under a mantle of rock debris and vegetation ranging from scattered herbs and shrubs on the younger moraines to multiple-generation closed spruce forest on the oldest moraines, which are 600–1200 yr old. Lakes on the youngest moraines are temporary, turbid with glacial silt, and marked by unstable ice-cored slopes. On older moraines most lakes have clear water and stable slopes. On the oldest moraines many lakes have brown water caused by dissolved humic materials derived from the thick forest floor, but even here some slopes are unstable because of continued melting of buried ice. Morainic lakes contain bicarbonate waters of moderate alkalinity and conductivity and low levels of nutrients. The highly diverse phytoplankton is dominated by chrysophytes and cryptomonads, with few diatoms. Extremely low values for phytoplankton biomass place most of the lakes in an “ultraoligotrophic” category. Zooplankton is dominated by copepods, which were found even in ice ponds only a few years old, and by the cladoceranDaphnia pulex. Surface-sediment samples contained a total of 16 species of chydoridCladocera. Of these,Alonella excisaandAlona barbulataare apparently the pioneer species in the youngest lakes.Chydorus sphaericusonly appears in lakes of the oldest moraines. A successional pattern is not conspicuous, however, partly because some of the lakes on the older moraines originated by recent collapse over buried ice. Lakes on the upland outside the dead-ice moraines yielded 39 species in the zooplankton. The distinctive assemblage on upland lakes may relate more to different water chemistry than to age.
Instantaneous Glacierization, the Rate of Albedo Change, and Feedback Effects at the Beginning of an Ice Age
Authors: Koerner R. M. 
Published: December 2004

AbstractA study of the average annual- and melt-season albedos for the northwest side of the Devon Island Ice Cap shows that there is no step in the average albedo either at the equilibrium or firn line. Similarly, during a period of increasing glacierization there is nowhere any dramatic increase in the average annual- or melt-season albedo with time as the equilibrium line gradually moves downslope. This means that the inception of ice caps and permanent snowfields does not make a significant change to the rate of increasing albedo and its associated feedback effects during the same period of glacierization. The extension of the annual period of snowcover generally is much more important to the feedback process (by increasing albedo) than the specific lowering of the equilibrium line. A decreased variability of summer climate, and hence the disappearance of “anomalously” warm summers, may be an integral part of the glacierizing process.
Holocene Desert Soil Formation under Sodium Salt Influence in a Playa-Margin Environment
Authors: Peterson Frederick F. 
Published: December 2004

AbstractA visually prominent desert soil with a horizon of clay accumulation (Typic Natrargid) has formed under an arid climate in Panamint Valley, California, in sandy, very calcareous, saline fan alluvium in less than about 3500 yr, and probably less than 2000 yr. Such soils can be used as stratigraphic markers, but could be confused with other desert soils with clay-accumulation horizons (Haplargids) which occur much more commonly on desert alluvial fans, are mostly late Pleistocene or older, and do not form in parent materials that are still calcareous. This Natrargid formed in a playa-margin environment, where clay for translocation and sodium salts that engender rapid clay movement probably were provided by dust fall.
Biostratigraphic Correlation of Pleistocene Marine Deposits and Sea Levels, Atlantic Coastal Plain of the Southeastern United States
Authors: Cronin Thomas M. 
Published: December 2004

AbstractMarine ostracodes from 50 localities were studied to determine the age and elevation of Pleistocene sea levels in the Atlantic coastal plain from Maryland to northern Florida. Using ostracode taxon and concurrent ranges, published planktic biostratigraphic, paleomagnetic, and radiometric data, ostracode assemblage zones representing early (1.8-1.0 my), middle (0.7-0.4 my), and late (0.3-0.01 my) Pleistocene deposition were recognized and used as a basis for correlation. Ostracode biofacies signifying lagoonal, oyster bank, estuarine, open sound, and inner sublittoral environments provided estimated ranges of paleodepths for each locality. From these data the following minimum and maximum Pleistocene sea-level estimates were determined for the southeastern coastal plain: late Pleistocene, 2–10 m from Maryland to northern Florida; middle Pleistocene, 6–15 m in northern South Carolina; early Pleistocene, 4–22 m in central North Carolina, 13–35 m in southern North Carolina, and 6–27 m in South Carolina. Climatically induced glacio-eustatic sea-level fluctuations adequately account for the late Pleistocene sea-level data, but other factors, possibly differential crustal uplift, may have complicated the early Pleistocene record.
New Evidence from Beneath the Western North Atlantic for the Depth of Glacial Erosion in Greenland and North America
Authors: Laine Edward P. 
Published: December 2004

AbstractInterpretation of Deep Sea Drilling Project results and air-gun seismic profiles suggests that about 106 km3 of sediment have been eroded from eastern North America and southern Greenland and deposited in the adjacent North Atlantic since the beginning of continental glaciation. This volume is a minimum estimate which does not account for sediment beneath the continental shelf nor that portion carried south of the Blake-Bahama Outer Ridge by the Western Boundary Undercurrent. It represents erosion of about 100 m of solid rock and indicates that more than 90% of the sediment eroded from these areas was deposited as sands, silts, and clays in the adjacent western North Atlantic. Glaciation accounts for between 55 and 95 m of this average 100 m, and fluvial processes account for the remainder. The documented erosion in part substantiates W. A. White's (1972, Geological Society of America Bulletin83, 1037–1056) hypothesis of deep erosion and exhumation of shield regions, but is not in agreement with the entire volume of erosion implied by his model.
Holocene Sea-Level Changes in Palau, West Caroline Islands
Authors: Easton William H. , Ku Teh-Lung 
Published: December 2004

Abstract14C ages supplemented by 230Th/234U determinations have been obtained for calcareous deposits on Koror, Babelthuap, Auluptagel, and Adorius Islands in the Palau Group, West Caroline Islands. Test borings for a bridge between Koror and Babelthuap reveal shoreface terraces consisting largely of bioclastic sand, but resembling fringing reefs. The base of the shoreface terraces dates to between 7000 and 8000 14C yr B.P. and the upper surfaces are slightly younger than 4000 yr B.P. Spacing of the subsurface isochrons indicates that the rate of sedimentation increased up-section on Koror terrace and decreased up-section on Babelthuap terrace. The average rate of deposition in the terraces was 0.5 cm/yr. Isochrons in the Babelthuap shoreface terrace are 7 m higher than those in the Koror terrace. If deposition was sufficient to keep the surfaces of the terraces at low tide level, then the Babelthuap side was essentially stable and the Koror side was uplifted between about 8000 and 6300 yr ago, and then subsided until 4000 yr ago; since then there has been about 2 m of uplift. “Top hat” microatolls on Koror terrace indicate that relative sea level has dropped about 30 cm in the past 75 yr. In the absence of good evidence for changes of level in water ponded in a moat, it is likely that the microatolls indicate uplift of the terrace. On the other hand, if tectonic activity was minimal, then differences in the two terraces are due to differences in sedimentation with the Koror side of the channel being substantially subtidal between about 7000 and 5000 yr B.P. Taking the composite eustatic sea-level curve of Hawaii and elsewhere as a reference standard, it is deduced that Auluptagel Island has risen 0.8 m in the last 2900 yr, and Adorius Island has risen approximately 8 m in the last 5000–6000 yr.
Estimates of Past Climate at Paleolake Chad, North Africa, Based on a Hydrological and Energy-Balance Model
Authors: Kutzbach John E. 
Published: December 2004

AbstractModeling the combined hydrological and energy balances of Paleolake Chad and its drainage basin yields an estimate of at least 650 mm/yr for annual precipitation during portions of the early Holocene (10,000 to 5000 yr B.P.); the current rainfall in Chad Basin is 350 mm/yr. Two versions of the model are developed. The first version is one in which precipitation and lake area are linearly related. This version requires specification first of the area, net radiation, and Bowen ratio of the lake and second of the paleovegetation, net radiation, and Bowen ratio of the surrounding basin. In the second version of the model the ralationship between precipitation and lake area is nonlinear because the runoff ratio and Bowen ratio of the basin are made functions of precipitation. As the lake increases in area in response to increased precipitation, this version of the model allows for further increases in runoff (from the basin into the lake) as the vegetation changes from steppe to savanna and swamp. This nonlinear process may provide a partial explanation for the expansive paleolakes of the early Holocene. The results derived from both models are in good agreement with previously derived estimates of precipitation for North Africa during the early Holocene.
The Origin and Distribution of Subbottom Sediments in Southern Lake Champlain
Authors: Freeman-Lynde R. P. , Hutchinson D. R. , Folger D. W. , Wiley B. H. , Hewett M. J. 
Published: December 2004

AbstractThree units, correlatable with recent Lake Champlain, late-glacial marine Champlain Sea, and proglacial Lake Vermont sediments, have been identified from about 200 km of high-resolution seismic reflection profiles and eight piston cores collected in southern Lake Champlain. Lake Vermont deposits are nonfossiliferous and range from thin to absent nearshore and on bedrock highs to more than 126 m thick near Split Rock Point. Champlain Sea sediments contain marine foraminifers and ostracodes and are fairly uniform in thickness (20–30 m). Recent Lake Champlain sediments range in thickness from 0 to 25 m. Average sedimentation rates for Lake Vermont are considerably higher (4–8 cm/yr) than those for the Champlain Sea (0.8–1.2 cm/yr) and Lake Champlain (0.14–0.15 cm/yr). Bedrock, till, and deltaic and alluvial deposits were also identified on the acoustic records but were not sampled. An unconformity separating Champlain Sea deposits from Lake Champlain deposits is associated with numerous benches at water depths of 20–30 m. These benches, the alluvial deposits, and the onset of deltaic deposition are probably associated with a low water level stillstand at the close of the Champlain Sea episode.
The Los Chocoyos Ash, Guatemala: A Major Stratigraphic Marker in Middle America and in Three Ocean Basins
Authors: Drexler John W. , Rose W. I. , Sparks R. S. J. , Ledbetter M. T. 
Published: December 2004

AbstractThe Los Chocoyos Ash, having erupted from vents near the Lake Atitlán caldera, Guatemala, is perhaps the largest Quaternary silicic pyroclastic unit in Central America. It consists of an underlying H-tephra member and an overlying ash-flow member. One-hundred-and-five samples of ash from the Guatemalan Highlands and deep-sea cores in the equatorial Pacific and Gulf of Mexico were analyzed by neutron activation and/or electron microprobe. Glass shard chemistry, determined by microprobe, is useful for distinguishing several very widespread, distinct, deep-sea ash layers, but needs support from trace-element data when applied on land to distinguish between many individual eruptions from the same province. Data from this study support the correlation of the Worzel ‘D’ layer and the Los Chocoyos Ash proposed by Hahn et al. (1979) and Bowles et al. (1973). Chemical data from this study are used to correlate the Y-8 ash layer of the Gulf of Mexico with the Los Chocoyos Ash. The recognition of the Los Chocoyos Ash in the Gulf of Mexico and equatorial Pacific increases the known areal extent of the unit to more than 6 × 106 km2 and allows an age of 84,000 yr B.P. to be assigned to the formation on the basis of oxygen-isotope stratigraphy, biostratigraphy, and Pa-Th-isotope data. Trace-element data obtained from seven other ash layers in the Gulf of Mexico and the equatorial Pacific, when combined with new land-based data, should allow further correlation and dating of ash units in Central America.
A Late Holocene Marine Terrace on the Kidnappers Coast, North Island, New Zealand: Some Implications for Shore Platform Development Processes and Uplift Mechanism
Authors: Hull Alan G. 
Published: December 2004

AbstractA marine terrace up to 6 m above present mean sea level is preserved along 15 km of the Kidnappers coast, Hawke's Bay, North Island, New Zealand. Radiocarbon dates for 10 shell samples collected from intertidal marine deposits overlying an uplifted shore platform have a total age range of 590 yr (from 2280 ± 50 to 2750 ± 70 yr B.P.). Sample age decreases landward suggesting a small relative sea-level rise, probably as a result of tectonic subsidence prior to uplift. Rates of contemporary shore platform formation preclude the preservation of a marine terrace subjected to constant, aseismic uplift. Preservation of a subhorizontal uplifted shore platform mantled by intertidal marine deposits with in situ fauna is best explained by abrupt coseismic uplift 2300 yr B.P. and preceded by tectonic subsidence. The presence of a single marine terrace does not permit the calculation of past earthquake magnitude or recurrence, but the NNE tilt of the 2300-yr-old marine terrace indicates continued growth of the north-trending late Pleistocene Kidnappers Anticline.
Holocene Development of Parabolic Dunes in the Central St. Lawrence Lowland, Québec
Authors: Filion Louise 
Published: December 2004

AbstractStabilized parabolic dunes in the central St. Lawrence Lowland are oriented NE-SW, in the postulated direction of dune-building winds coming from anticyclonic air circulation induced by the retreating Laurentide Ice Sheet about 10,000 yr ago. The eolian chronology reconstructed from several sections in mixed dune-peatland environments indicates that postglacial plant colonization, characterized by a fortuitous assemblage of arctic-subarctic and boreal elements, preceded dune formation during Champlain Sea regression around 10,000 yr B.P. Confined peatlands and small forests were buried by eolian sands between 10,000 and 7500 yr B.P. under dry and temperate conditions. This eolian episode lasted about 250014C yr and ended when cyclonic air circulation similar to the present humid climatic regime was established following the breakup and disappearance of the Laurentide Ice Sheet over Hudson Bay and peripheral areas. Dune stabilization, through paludification of well-drained eolian sands about 7500 yr B.P., suggests a major shift in climate toward wetter conditions that have been characteristic during most of the Holocene in eastern North America. Minor eolian erosion induced by wildfire was recorded during late Holocene time (about 1250 yr B.P.). Anthropogenic perturbation (logging and agriculture practice) was also responsible for recent very local eolian activity.