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Northern Half (northern + half)
Selected AbstractsMesozoic,Paleogene sedimentary facies and paleogeography of Tibet, western China: tectonic implicationsGEOLOGICAL JOURNAL, Issue 3 2002Kai-Jun Zhang Abstract In Early,Middle Triassic time, an abyssal sea covered most of the Songpan,Ganzi area, whereas a Central Tibetan Landmass, up to 400,km wide, may have stretched across the Lhasa and Western Qiangtang terrains. In Late Triassic time, the Songpan,Ganzi sea closed, the Central Tibetan Landmass receded westwards away from southern Western Qiangtang, a littoral environment dominated Eastern Qiangtang, middle Western Qiangtang, and southeastern Lhasa, a shelf environment existed only in northern and southeastern Western Qiangtang and northwestern Eastern Qiangtang, and abyssal flysch was spread along the eastern Bangonghu,Nüjiang zone. In Early,Middle Jurassic time, Songpan,Ganzi had become part of the Eurasian continent, abyssal flysch sediments stretched throughout the Bangonghu,Nüjiang zone, the Central Tibetan Landmass was only locally present in southwestern Lhasa, and the Tethyan epicontinental sea nearly covered all Tibet southwest of the Jinsajiang suture. In Late Jurassic time, oceanic flysch deposition existed only along the westernmost Bangonghu,Nüjiang zone, nearly all of Tibet was covered by coastal deposits, and shelf deposits existed only in northern Western Qiangtang and westernmost Lhasa. In the early stage of Early Cretaceous time, the majority of Qiangtang had become dry land, and a supralittoral environment dominated across the entire Lhasa terrain. However, during the late stage of the Early Cretaceous time, platform,shelf carbonates prevailed on southern Western Qiangtang and northern Lhasa. In Late Cretaceous time, the majority of Qiangtang had become emergent land, and a supratidal environment dominated Lhasa, the western rim of Western Qiangtang, and Tarim. In Paleogene time, the majority of Tibet became emergent land, and a supratidal environment existed only on the southern and western rims. The dominance of Upper Triassic,Jurassic shelf carbonates on the northwestern Eastern Qiangtang corner and the northern Western Qiangtang rim suggests a diachronous closing of the Jinsajiang paleo-Tethys ocean, first during latest Triassic time when the Eastern Qiangtang terrain collided with Asia and finally in Jurassic time when the Western Qiangtang terrain was amalgamated to Asia. Rich picotites in Upper Triassic sandstones of middle Qiangtang suggest that the Shuanghu suture could have extended along the middle of Qiangtang, and stable shelf sedimentation during Late Triassic,Middle Jurassic time in the Western Qiangtang terrain shows that the suture probably could not have formed until Middle Jurassic time. The opening time of the Bangonghu,Nüjiang mid-Tethys ocean could be Late Triassic time due to the existence of the Central Tibetan Landmass across Western Qiangtang and Lhasa during Early,Middle Triassic time. However, its opening was diachronous, at Late Triassic time in the east and at Early,Middle Jurassic time in the west. Furthermore, its closing was also diachronous, first in the east at the beginning of Late Jurassic time and later in the west in latest Jurassic to earliest Cretaceous time. Widespread upper Lower Cretaceous limestone up to 5,km thick over the northern half of Lhasa indicates that southern Tibet could have undergone an extensive backarc subsidence during late Early Cretaceous time. Continuous shallow marine sedimentation through the entire Cretaceous time over much of southern Tibet indicates that southern Tibet was intensely elevated only after the end of Paleogene time, its high topography being the product of the Indo-Asian collision. Copyright © 2002 John Wiley & Sons, Ltd. [source] Crustal structure of central and northern Iceland from analysis of teleseismic receiver functionsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2000Fiona A. Darbyshire We present results from a teleseismic receiver function study of central and northern Iceland, carried out during the period 1995,1998. Data from eight broad-band seismometers installed in the SIL network operated by the Icelandic Meteorological Office were used for analysis. Receiver functions for each station were generated from events for a wide range of backazimuths and a combination of inversion and forward modelling was used to infer the crustal structure below each station. The models generated show a considerable variation in the nature and thickness of the crust across Iceland. The thinnest crust (20,21 km) is found in the northern half of the Northern Volcanic Zone approximately 120 km north of the centre of the Iceland mantle plume. Thicker crust (24,30 km) is found elsewhere in northern and central Iceland and the thickest crust (37 km) is found close to the plume centre. Velocity,depth profiles show a distinct division of the crust into two main sections, an upper high-velocity-gradient section of thickness 2,8 km and a lower crustal section with small or zero overall velocity gradient. The thickness of the upper crust correlates with the tectonic structure of Iceland; the upper crust is thickest on the flanks of the northern and central volcanic rift zones and thinnest close to active or extinct central volcanoes. Below the Krafla central volcano in northeastern Iceland the receiver function models show a prominent low-velocity zone at 10,15 km depth with minimum shear wave velocities of 2.0,2.5 km s,1. We suggest that this feature results from the presence of partially molten sills in the lower crust. Less prominent low-velocity zones found in other regions of Iceland may arise from locally high temperatures in the crust or from acidic intrusive bodies at depth. A combination of the receiver function results and seismic refraction results constrains the crustal thickness across a large part of Iceland. Melting by passive decompression of the hot mantle below the rift zone in northern Iceland forms a crust of thickness ,20 km. In contrast, the larger crustal thickness below central Iceland probably arises from enhanced melt production due to active upwelling in the plume core. [source] Michigan Basin Regional Ground Water Flow Discharge to Three Great LakesGROUND WATER, Issue 4 2002John Robert Hoaglund III Ground water discharge to the Great Lakes around the Lower Peninsula of Michigan is primarily from recharge in riparian basins and proximal upland areas that are especially important to the northern half of the Lake Michigan shoreline. A steady-state finite-difference model was developed to simulate ground water flow in four regional aquifers in Michigan's Lower Peninsula: the Glaciofluvial, Saginaw, Parma-Bayport, and Marshall aquifers interlayered with the Till/"red beds," Saginaw, and Michigan confining units, respectively. The model domain was laterally bound by a continuous specified-head boundary, formed from lakes Michigan, Huron, St. Clair, and Erie, with the St. Clair and Detroit River connecting channels. The model was developed to quantify regional ground water flow in the aquifer systems using independently determined recharge estimates. According to the flow model, local stream stages and discharges account for 95% of the overall model water budget; only 5% enters the lakes directly from the ground water system. Direct ground water discharge to the Great Lakes' shorelines was calculated at 36 m3/sec, accounting for 5% of the overall model water budget. Lowland areas contribute far less ground water discharge to the Great Lakes than upland areas. The model indicates that Saginaw Bay receives only ,1.13 m3/sec ground water; the southern half of the Lake Michigan shoreline receives only ,2.83 m3/sec. In contrast, the northern half of the Lake Michigan shoreline receives more than 17 m3/sec from upland areas. [source] Post-Hypsithermal plant disjunctions in western Alberta, CanadaJOURNAL OF BIOGEOGRAPHY, Issue 3 2003W. L Strong Abstract Aim, Evaluate the hypothesis that nine disjunct vascular plant species along the eastern slopes of the Rocky Mountains and in the Peace River District of west-central Alberta represent remnants of more southerly vegetation that occupied these areas during the Holocene Hypsithermal (9000,6000 yr bp). Alternatively, these plants represent populations that became established because of independent chance dispersal events. Location, This study focuses on the area east of the Rocky Mountain Continental Divide in the Province of Alberta and the State of Montana in western Canada and USA, respectively. Methods, Disjunct species were identified and their distributions mapped based on a review of occurrence maps and records, botanical floras and checklists, herbaria specimens, ecological and botanical studies, and field surveys of selected species. A disjunct species was defined as a plant population separated from its next nearest occurrence by a distance of > 300 km. Evaluation of the hypothesis was based on a review of published and unpublished pollen stratigraphy and palaeoecological studies. The potential geographical distribution of Hypsithermal vegetation was based on modern regional-based ecosystem mapping and associated monthly temperature summaries as well as future climatic warming models. Results, The hypothesis was compatible with Holocene pollen stratigraphy, Hypsithermal permafrost and fen occurrence, and palaeosol phytolith analyses; and future global climatic warming models. Modelled regional Hypsithermal vegetation based on a 1 °C increase in July temperatures relative to current conditions, indicated that much of the boreal forest zone in Alberta could have been grassland, which would explain the occurrence of Prairie species in the Peace River District. This amount of latitudinal vegetation shift (6.5°) was similar to an earlier Hypsithermal permafrost zone location study. An equivalent shift in vegetation along the eastern Cordillera would have placed south-western Montana-like vegetation and species such as Boykinia heucheriformis (Rydb.) Rosend. and Saxifraga odontoloma Piper within the northern half of the Rocky Mountains and foothills in Alberta, which represents the location of modern-day disjunct populations of these species. Main conclusions, Warmer and drier climatic conditions during the Holocene Hypsithermal resulted in the northward displacement of vegetation zones relative to their current distribution patterns. Most of Alberta was probably dominated by grasslands during this period, except the Rocky Mountains and northern highlands. Modern-day species disjunctions within the Rocky Mountains and Peace River District as well as more northerly areas such as the Yukon Territory occurred when the vegetation receded southward in response to climatic cooling after the Hypsithermal. Wind dispersal was considered an unlikely possibility to explain the occurrence of the disjunct species, as most of the plants lack morphological adaptations for long distance transport and the prevailing winds were from west to east rather than south to north. However, consumption and transport of seeds by northward migrating birds could not be excluded as a possibility. [source] The Languages of SiberiaLINGUISTICS & LANGUAGE COMPASS (ELECTRONIC), Issue 1 2009Edward J. Vajda Although Russian today is the dominant language in virtually every corner of North Asia, Siberia and the Northern Pacific Rim of Asia remain home to over three dozen mutually unintelligible indigenous language varieties. Except for Tuvan, Buryat, and Yakut, most are rapidly losing ground to Russian if not already critically endangered. Several more have already become extinct in the four centuries since the area's incorporation into the Russian state. From an ethnographic perspective, Siberian languages merit attention for their interplay of pastoral and hunter,gatherer influences and also for the fact that Siberia represents the staging ground for prehistoric migrations into the Americas. North Asia contains several autochthonous microfamilies and isolates not found outside this region , the so-called ,Paleo-Asiatic' (or ,Paleosiberian') languages Ket, Yukaghir, Nivkh, and the Chukotko-Kamchatkan microfamily, which includes Chukchi, Koryak, and Itelmen. Ainu, formerly spoken on Sakhalin and the Kuriles as well as in Hokkaido, and the three varieties of Eskimoan spoken in historic times on the Russian side of Bering Strait, likewise belong to the earlier, non-food producing layers of ethnolinguistic diversity in North Asia. All of these languages, aside from Eskimoan, are entirely autochthonous to the northern half of Asia. Siberian languages spoken by pastoral groups, on the other hand, belong to families represented more prominently elsewhere. Families, such as Uralic, Turkic, Mongolic, and especially Tungusic (the northern branch of the Tungus-Manchu family), became dominant in Siberia long before the coming of the Russians. As an extension of pastoral Inner Eurasia, Siberia displays many traits characteristic of a linguistic area: suffixal agglutination, widespread dependent marking typology, a fairly elaborate system of spatial case markers, and the use of case suffixes or postpositions to signal syntactic subordination. There are also notable idiosyncratic features, particularly among the so-called Paleo-Siberian languages. These include the areally atypical feature of possessive prefixes and verb-internal subject/object prefixes in Ket, the unique verb-internal focus markers of Yukaghir, the extensive numeral allomorphs that serve as nominal classifiers in Nivkh, and the reduplicative stem augmentation used by Chukchi nouns to express the absolutive singular (in contrast to plurals and oblique case forms, where the stem is simple). While North Asia has long been the preserve of linguists writing in Russian or German (including many Finns and Hungarians), since the collapse of the Soviet Union the number of English-language treatments of Siberian languages is increasing. [source] On estimating contributions of basin ejecta to regolith deposits at lunar sitesMETEORITICS & PLANETARY SCIENCE, Issue 1 2003Larry A. Haskin This model is based on impact crater scaling equations (Housen, Schmitt, and Holsapple 1983; Holsapple 1993) and the concept of ballistic sedimentation (Oberbeck 1975), and takes into account the size distribution of the individual fragments ejected from the primary crater. Using the model, we can estimate, for an area centered at the chosen location of interest, the average distribution of thicknesses of basin ejecta deposits within the area and the fraction of primary ejecta contained within the deposits. Model estimates of ejecta deposit thicknesses are calibrated using those of the Orientale Basin (Moore, Hodges, and Scott 1974) and of the Ries Basin (Hörz, Ostertag, and Rainey 1983). Observed densities of secondary craters surrounding the Imbrium and Orientale Basins are much lower than the modeled densities. Similarly, crater counts for part of the northern half of the Copernicus secondary cratering field are much lower than the model predicts, and variation in crater densities with distance from Copernicus is less than expected. These results suggest that mutual obliteration erases essentially all secondary craters associated with the debris surge that arises from the impacting primary fragments during ballistic sedimentation; if so, a process other than ballistic sedimentation is needed to produce observable secondary craters. Regardless, our ejecta deposit model can be useful for suggesting provenances of sampled lunar materials, providing information complementary to photogeological and remote sensing interpretations, and as a tool for planning rover traverses (e.g., Haskin et al. 1995, 2002). [source] Population structure and phylogeography of Solanum pimpinellifolium inferred from a nuclear geneMOLECULAR ECOLOGY, Issue 7 2004Ana Lucía Caicedo Abstract Phylogeographical studies are emerging as a powerful tool for understanding the population structure and evolution of wild relatives of crop species. Because of their value as genetic resources, there is great interest in exploring the distribution of variation in wild relatives of cultivated plants. In this study, we use sequence variation from the nuclear gene, fruit vacuolar invertase (Vac), to investigate the population history of Solanum pimpinellifolium. Solanum pimpinellifolium is a close relative of the cultivated tomato and has repeatedly served as a source of valuable traits for crop improvement. We sequenced the second intron of the Vac gene in 129 individuals, representing 16 populations from the northern half of Peru. Patterns of haplotype sharing among populations indicate that there is isolation by distance. However, there is no congruence between the geographical distribution of haplotypes and their genealogical relationships. Levels of outcrossing decrease towards the southernmost populations, as previously observed in an allozyme study. The geographical pattern of Vac variation supports a centre of origin in northern Peru for S. pimpinellifolium and a gradual colonization along the Pacific coast. This implies that inbreeding populations are derived from outcrossing ones and that variation present at the Vac locus predates the spread of S. pimpinellifolium. The expansion of cities and human agricultural activity in the habitat of S. pimpinellifolium currently pose a threat to the species. [source] Regional differences in craniofacial diversity and the population history of Jomon JapanAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2009Tsunehiko Hanihara Abstract The people associated with the Jomon culture, the Neolithic inhabitants of Japan, are one of the key groups in the population history of East Asia, because they retain many archaic characters that may be traced back to Eurasian Upper Palaeolithic hunter,gatherers. In this study, the regional diversity of the Jomon skeletal series was estimated by applying the R-matrix method to 34 craniofacial measurements. The patterns of intraregional variation indicate little effect on the genetic structure of the Jomon from long-term gene flow stemming from an outside source. The regional diversities were further estimated by pooling all individuals into regional aggregates, and by computing the mean variance within local groups in each region. Although the pattern of phenotypic variation differs depending on the unit of analysis, the gradient of the diversity retains its identity. The Hokkaido region, the northernmost part of the Japanese archipelago, has the highest variance, followed by the regions of eastern Japan, while the southwestern regions have the lowest variance. These findings suggest that the Jomon ancestors of the northern part of Japan might have expanded southward to Honshu Island. Global analyses including samples from Eurasia, Africa, and Australia dating roughly to the same chronological periods as those of the Jomon samples, indicate that the Jomon cranial series share part of their ancestral gene pool with early northeastern Asians. The present findings support the archeologically suggested population growth and expansion in the northern half of the Eurasian continent during the late Pleistocene and early Holocene periods. Am J Phys Anthropol, 2009. © 2008 Wiley-Liss, Inc. [source] Bergmanns's size cline in New Zealand marine spray zone spiders (Araneae: Anyphaenidae: Amaurobioides)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010BRENT D. OPELL Members of the spider genus Amaurobioides are restricted to the spray zone of rocky marine coasts, where they construct and hunt from silk retreats. Collecting for this study shows these spiders to be distributed around the entire New Zealand coast. A Templeton, Crandall, and Sing (TCS) analysis of the ND1 mitochondrial gene places specimens from the North Island and the northern half of the South Island into a group distinct from Amaurobioides maritima O.P.-Cambridge, 1883, which is restricted to the southern half of the South Island. Females of this northern group exhibit latitude- and temperature-related clines in body length, body mass, and residual index of condition, with larger individuals with greater indices of condition being found at cooler, southern sites. This size cline also appeared in a broader geographical analysis that included Amaurobioides piscator Hogg, 1909 from the sub-Antarctic Auckland and Campbell Islands. Thirteen ND1 haplotypes are represented in the northern group. Both independent contrast analyses and standard regressions of the mean body lengths and mean masses of these haplotypes, and the mean latitudes and temperatures of the sites where haplotypes were present, document a Bergmann's size cline, and provide evidence for an underlying genetic component. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 78,92. [source] Apoptolidinone A: Synthesis of the Apoptolidin A AglyconeCHEMISTRY - A EUROPEAN JOURNAL, Issue 28 2006Julia Schuppan Dr. Abstract An efficient stereocontrolled synthesis of apoptolidinone A, the aglycone of apoptolidin A is described. The synthetic strategy relies on a cross coupling between C11/C12 of a northern half (C1,C11) and a southern part (C12,C28) followed by a ring-size selective macrolactonization. Key steps for the introduction of the southern half stereocenters are a stereoselective aldol reaction, a substrate controlled dihydroxylation and a chelation-controlled Grignard/aldehyde addition. The conjugated triene of the northern half was built up successively by E -selective Wittig reactions. L -Malic acid was chosen as the chiral pool source for the C8/C9 stereocenters. The final cleavage of the silyl ethers and the conversion of the C21 methyl ketal into the hemiketal was achieved by HF,pyridine. [source] New Guinea: A Correlation between Accreting Areas and Dispersing SapindaceaeCLADISTICS, Issue 3 2001Peter C. van Welzen A correlation between accreting (hybridizing) areas and dispersing taxa (several genera of Southeast Asian/Australian Sapindaceae) is theoretically impossible in cladistic biogeography. However, in particular circumstances (primitive absence followed by colonization and speciation) cladistic methods can reconstruct (part of) the historical sequence of accretion. In this example, the phases in the accretion history of more than 30 terranes of the northern half of New Guinea correspond reasonably well with the generalized area cladogram of the Sapindaceae. [source] | ||||||||||||||||