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1.
Jens Böcher 《Boreas: An International Journal of Quaternary Research》2012,41(4):644-659
Sediments from the last interglacial (Eemian) in Jameson Land, East Greenland, and the Thule area, NW Greenland, have revealed a number of insect fragments of both arctic and more or less warmth‐demanding species. Altogether, the interglacial fauna of Coleoptera (beetles) indicates boreal conditions. Undoubtedly, a large fraction of the insect fauna succumbed when the mild Eemian climate cooled drastically during the last glacial stage. However, a group of hardy species now found far north into the High Arctic might be glacial survivors. It is, however, still puzzling why well‐adapted arctic beetle species such as Amara alpina and Isochnus arcticus did not survive the last glacial stage in Greenland. Two factors that have not been sufficiently considered when discussing survival contra extinction are the importance of microclimate and the number of sun‐hours during the Arctic summer. Even among the Coleoptera, which as a group fares quite badly in the Arctic, there might be survivors, at least among those found both during the interglacial and as fossils during the early Holocene. First of all, glacial survival applies to the seed bug Nysius groenlandicus, which was widespread during the Eemian, was found soon after the last deglaciation, and is now almost omnipresent in Greenland. 相似文献
2.
Human activities have an impact on extant biotic communities, and may have had just as important an impact in the past. We assess human impact on limpet assemblages during the Upper Palaeolithic in Asturias (north‐west Spain). The intensely exploited genus Patella exhibited a marked size decrease and a change in species assemblage composition, substituting the larger species P. vulgata for the smaller P. depressa. The present Patella assemblages in the upper tidal level exhibit the same pattern as those of the Epipalaeolithic (approx. 12 000 to 6000 years before the present). Although climate change may have contributed to such species replacement, spatial differences between close areas with different densities of Palaeolithic human settlements indicate unequivocal human impact. Present Patella species sampled from the region exhibit genetic signatures of past bottlenecks in mitochondrial DNA, which also indicate recent demographic expansion, suggesting that old impacts have been sufficiently important to leave genetic traces in current populations. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
3.
I. L. Jones Volker Heine Maurice Leslie Geoffrey D. Price 《Physics and Chemistry of Minerals》1990,17(3):238-245
The technique of calculating lattice dissociation energies using static, minimum lattice energy, ionic models has been extended to allow for multiple occupancy of the ionic sites. A particular lattice site can have a fraction x of an ionic species A and a fraction y of an ionic species B, where the position of each can be relaxed separately along with the unit cell dimensions until an equilibrium is reached. Various degrees of long and short range order can be modelled. This technique has been applied to the mineral sillimanite, Al2SiO5, to calculate the effect on the lattice energy of (Al, Si) ordering over the tetrahedral sites. It is found using this method that (Al, Si) ordering with space group Pbmn stabilizes the material by 29.25 kcal/mol (Aliv-O-Aliv), with respect to the completely disordered material. 相似文献
4.
1975年我们报道了泥河湾盆地怀来及蔚县境内发现半咸水有孔虫化石,当时认为它们的层位可能属第四系上部,后来进一步工作证实应是泥河湾组上部沉积。1977年我们对华北平原第四纪海进海退现象作了初步报道,认为华北平原在早更新世时发生过海进(渤海海进),并引用陈方吉在北京东南发现海相介形虫资料,说明早更新世渤海海进时海水曾经到达这一地区。1978年李鼎容等在北京市顺义县早更新世地层中发现大量有孔虫化石。进一步证实北京地区早更新世确曾发生过海进,使我们解释怀来及蔚县所发现的半咸水有孔虫来源,有更多证据。这一发现,对于北京地区第四纪地层划分对比、新构造运动判别和古地理恢复有重大意义。 相似文献
5.
Biogeochemical Prospecting of Sulphide Minerals in Winder Valley, Balochistan, Pakistan 总被引：1，自引：0，他引：1
Abstract: The Mor Range is mountainous terrain in southern Balochistan dominantly occupied by exposures of rocks of the Ferozabad Group which is comprised of Lower‐Middle Jurassic carbonates and siliciclastics. This group contains syngenetic and epigenetic Zn–Pb–Ba mineralization classified as Stratiform Sediment‐Hosted (SSH) and Mississippi Valley Type (MVT) deposits. Three important flora of the Saharo–Sindian, phytogeographical region of Pakistan, namely Tamarix aphyl–la, Salvadora oleoides and Acacia arabica have been studied as a mineralization prospecting tool. Samples of these species were collected from Winder Valley adjoining the Mor Range to prospect for new areas of mineralization, besides the known sulphide deposits. This study revealed the Draber, Thorar, Raj, Mithi and Kanrach localities as new prospect. Quantitative estimation of biophile elements (Zn–Cu–Pb) from the three species was made. A number of new Zn, Cu and Pb anomalies were distinguished in the area. The variation in the constituents of these species from different localities possibly varies with nature and distance from bedrock, mobility, climate, average abundance in the plant ash and exclusion mechanism of the flora. Acacia arabica with deep penetrating roots shows the best results and could be used to delineate new horizons of mineralization. In these species Zn and Cu are relatively concentrated whereas Pb shows limited enrichment. Lead therefore is the element best suited for pinpointing the mineralization owing to its relatively less mobile character. Relationships among Zn–Cu–Pb have been established using scattergrams and triangular variation diagram, which also demonstrate their genetic affiliation. Statistical analyses, such as determination of mean, mode, median, standard deviation, and coefficient of correlation, were also made to improve the raw geochemical data. These biogeochemical methods appear to be suitable in arid climate of Balochistan, if proper attention is paid to species selection. 相似文献
6.
Forty-seven samples from Upper Cretaceous sections penetrated by the Kachi-1 and Inga-1 wells in the South Yellow Sea Basin have been analysed for their spore and pollen content. Thirty-five species of 18 spore genera and 54 species of 28 pollen genera are documented. One new monotypic genus, Diporocolpopollenites, and its type species, D. kachiensis sp. nov., are erected, and Dilwynites Harris, 1965, and its type species, D. granulatus Harris, 1965, are emended. There are also three new combinations: Ephedripites eocaenicus (Selling, 1944), E. praeclarus (Chlonova, 1961), and Retitricolpites anguloluminosus (Anderson, 1960). Two palynological zones are erected: anAquilapollenites attenuatus Assemblage Zone, which encompasses deposits that are considered to be latest Campanian–Early Maastrichtian in age, and an Aquilapollenites eurypteronus Assemblage Zone for sections that have been dated as Late Maastrichtian. The assemblages are typical of the Yenisey-Amur Subprovince of the Aquilapollenites (floral) Province. Lowland floodplain to shallow, commonly mesotrophic, lacustrine environments of deposition are indicated. The climate was probably wet subtropical, with rainfall being somewhat higher during the Late Maastrichtian than through the latest Campanian–Early Maastrichtian. 相似文献
7.
Pinaki Roy Subhendu Bardhan Aparajita Mitra Sudipta K. Jana 《Journal of Asian Earth Sciences》2007,30(5-6):629-651
The Bathonian ammonite assemblages have been previously poorly recorded in Kutch. The present study has unearthed a rich array of ammonite taxa ranging from the Middle to Upper Bathonian. While Oxycerites Rollier (1909) is a new record from Kutch, the oldest occurrence of Choffatia Siemiradzki (1898) has been found from the Middle Bathonian horizon. Oxycerites cf. orbis (Giebel) is a zonal index of the Late Bathonian in other areas and thus facilitates interprovincial correlation. Besides, palaeobiogeographic and stratigraphic distribution of many species have been modified based on new information. For example, macrocephalitin species, i.e., Kamptokephalites cf. etheridgei Spath (1928), Macrocephalites bifurcatus transient intermedius Spath (1928), M. cf. mantataranus Boehm (1912) were previously known from West Pacific, Indonesia have been now found in Kutch. Gracilisphinctes Buckman (1920) has been previously known to occur during the Middle Bathonian time, the present work extends its stratigraphic distribution up to the definite Upper Bathonian horizon. Procerites hians (Waagen) an endemic species in Kutch previously known from the Upper Bathonian beds, its stratigraphic range has been extended down to the Middle Bathonian.Detail taxonomy of the newly obtained taxa has been done and in many cases sexual dimorphism has been recognized. 相似文献
8.
Goniomya sp. ind., and Goniomya sp. ind. aff. G. kasanensis (Geinitz), described by Diener (1903) from the Permian of the Central Himalayas, are shown to belong to Undulomya. Goniomya uhligi Holdhaus, 1913, thought by Holdhaus to be of Jurassic age, is also regarded as an Undulomya and con‐specific with or closely related to the above species. Cosmomya egregaria Holdhaus, 1913, the type species of Cosmomya Holdhaus, 1913, which comes from the same locality as Undulomya uhligi, is regarded as congeneric with Palaeocosmomya Fletcher, 1946. Palaeocosmomya therefore, becomes a synonym of Cosmomya, but is retained at the subgeneric level. The evidence now available indicates that Undulomya uhligi and Cosmomya egregaria are of Late Permian age. Undulomya and Cosmomya are regarded as two quite distinctive genera which also differ from the Jurassic genus Goniomya, in which species of both have hitherto often been included. Undulomya and Cosmomya have so far been recorded from Australia, India, Madagascar and the Soviet Union and Cosmomya, in addition, from Greenland. 相似文献
9.
Javier Ortega‐Hernández David A. Legg Jonathan Tremewan Simon J. Braddy 《Geology Today》2010,26(5):195-198
The euthycarcinoids are a mysterious group of extinct, possibly amphibious, arthropods. Like many groups of arthropods their affinities remain enigmatic. They comprise 15 species known mainly from the Late Carboniferous Coal Measures of Europe and North America, although they have been found in older rocks in Argentina and Australia. The oldest known euthycarcinoid is Apankura machu, from the Late Cambrian of Argentina, and the youngest is Euthycarcinus kessleri, from the Middle Triassic of France. 相似文献
10.
Bruce Runnegar 《Australian Journal of Earth Sciences》2013,60(2):227-252
Megadesmus Sowerby 1838 and Astartila Dana 1847 are bivalves from the Australian Permian, which belong to a group that Newell has termed “primitive desmodonts”. Both genera have a single blunt tooth in the right valve and a corresponding socket in the left. The tooth and socket are derived from folds in the valve margin and are not related to the teeth of heterodonts. Differences in shape, size, and pedal musculature separate Astartila from Megadesmus. Cleobis Dana 1847 differs only in having slightly different dentition and a small siphonal gape and is retained as a subgenus of Megadesmus. Astartila (Pleurikodonta) n. subgen. has been proposed for a small Astartila‐like species with well‐developed radial ornament. 相似文献
11.
Salt marshes respond to both slowly increasing tidal inundation with sea level rise and abrupt disturbances, such as storm-induced
wrack deposition. The effects of inundation pattern and wrack deposition have been studied independently but not in combination.
We manipulated inundation of tidal creek water and wrack presence individually and in combination, in two neighboring communities
within a Virginia high salt marsh during 1994 and 1995. The effects of these manipulations were assessed by measurements of
aboveground plant biomass. Altered inundation by itself produced little response in the various categories of plant biomass
measured. Wrack deposition affected all species (i.e., Juncus roemerianus, Spartina patens, and Distichlis spicata) showing a significant reduction in aboveground biomass, as expected. Recovery after wrack deposition was dependent on the
species. S. patens and D. spicata recovered from wrack deposition within one growing season, while J. roemerianus did not. Because the effects of wrack deposition greatly exceeded those of experimentally increased inundation, the possible
interactions between the two were masked. Increased inundation may have inhibited the colonization of bare areas by some species
after the removal of wrack from an area, although statistical significance at α=0.01 was not reached. Our results confirm
that wrack deposition can cause the redistribution of species within the high marsh community. Altered inundation may have
a greater effect on the re-establishment of the plant community after wrack deposition than it does without wrack deposition. 相似文献
12.
Stephen K. Donovan David A. T. Harper Zhan Renbin Lars Stemmerik Liu Jianbo Svend Stouge 《Geological Journal》2012,47(6):653-660
A collection of numerous crinoid pluricolumnals from the uppermost Darriwilian (Middle Ordovician) of Tibet were derived from one biological species of crinoid. The specimens were collected from well‐lithified, bioclastic shelf limestones of the upper part of the Lower Chiatsun Group, Pygodus serra Biozone; coeval rocks of similar lithology outcrop at the summit of Everest. A new crinoid morphospecies, Segmentocolumnus (col.) hanshessi, is tentatively considered a ‘stem‐group cladid’, perhaps a dendrocrinid. The proxistele is broad and pentagonal in section with a broad, pentagonal axial canal; the mesistele of similar gross morphology is more slender with a regularly heteromorphic column and a similarly wide axial canal; the dististele is a terminal dendritic radice with a pentastellate axial canal. In the mesistele, the meric sutures correspond to the centres of the sides of the column, but in the dististele they occur in the angles. This range of morphologies would have led to their inclusion in at least two morphogenera if they had not been closely associated; as they belong to a single biological species, they have been ‘lumped’ together herein. This is a rare contribution to our knowledge of the early crinoids from a region outside Europe and North America. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
13.
14.
Palaeolithic people commonly hunted Equus hydruntinus, an extinct species of equid whose cursorial body proportions suggest an adaptation to semi-arid conditions. Despite the frequency with which it is encountered in fossil deposits, only partial cranial remains have been reported until now. As a result, the systematic affiliation of the species remains a subject of controversy. Two nearly complete E. hydruntinus crania are presented here for the first time. These skulls show that E. hydruntinus is a distinct species, more closely related to the hemiones (Asiatic asses) than to any other equid. This suggests that the social organisation of E. hydruntinus followed one of two known equid sociotypes: resource defense territoriality. 相似文献
15.
Five species belonging to five genera and an unidentified rhynchonellid have been recognised in a Late Eocene (Priabonian) brachiopod assemblage from Castelnuovo in the Euganean Hills, north-eastern Italy. One genus and two species are new, i. e. Venetocrania euganea gen. et sp. nov. and “Terebratula” italica sp. nov. Orthothyris pectinoides (von Koenen 1894) is recorded for the first time from Italy. The other species are Terebratulina sp. cf. T. tenuistriata (Leymerie 1846) and Lacazella mediterranea (Risso 1826), both already known from the Italian Eocene. 相似文献
16.
Abstract: Abundant benthic foraminifera have been identified in thin sections of the siliceous black ore in the Ezuri Kuroko deposit, Hokuroku, Japan. By treating samples with conventional hydrofluoric acid digestion techniques, sponge spicules and radiolaria have also been recognized in the residue. Under microscopic observations, 94 individual foraminiferal specimens have been detected. However, as it is difficult to identify species or genera by means of microscope observations alone, only a small number of genera have been identified based on morphology. The foraminiferal assemblage is composed predominantly of agglutinated species (83%) with subordinate calcareous species (17%), and is assigned to the Cyclammina Assemblage based on the preponderance of Cyclammina (57%). The foraminifera are generally well preserved within micro‐crystalline to cryptocrystalline quartz, and exhibit no obvious features related to compaction or secondary deformation. Textural observations suggest that the siliceous component of this rock was not derived from an allochthonous block but instead constitutes autochthonous proto‐Kuroko sediment. The Cyclammina Assemblage in the ore is different from recently described foraminiferal assemblages in the vicinity of present deep‐sea hydrothermal vents, but is identical to those found in black shales of the Onnagawa to Funakawa stages in the Green Tuff region. The proto‐Kuroko sediment is assumed to have been deposited in an oxygen‐deficient environment within a closed, deep‐seated basin. The existence of siliceous microfossils suggests that the silica in the siliceous ore did not originate from silica sinter deposits produced by submarine hydrothermal activities, but from a biogenic siliceous ooze, probably composed of diatoms. Sulfide mineralization in the interstices of some of the microfossils is inferred to relate primarily to bacterial sulfate reduction associated with the decomposition of organic matter. The later sulfide mineralization associated with larger crystals (which contain fluid inclusions with homogenization temperatures of approximately 250C) cuts across the siliceous masses and foraminiferal septa, and may have been formed after consolidation of the siliceous ooze, accompanying the formation of acidic intrusive rocks during the late Onnagawa stage. 相似文献
17.
Zooplankton are an important trophic link and a key food source for many larval fish species in estuarine ecosystems. The
present study documents temporal and spatial zooplankton dynamics in Suisun Bay and the Sacramento–San Joaquin Delta—the landward
portion of the San Francisco Estuary (California, USA)—over a 37-year period (1972–2008). The zooplankton community experienced
major changes in species composition, largely associated with direct and indirect effects of introductions of non-native bivalve
and zooplankton species. A major clam invasion and many subsequent changes in zooplankton abundance and composition coincided
with an extended drought and accompanying low-flow/high-salinity conditions during 1987–1994. In the downstream mesohaline
region, the historically abundant calanoid copepods and rotifers have declined significantly, but their biomass has been compensated
to some extent by the introduced cyclopoid Limnothoina tetraspina. The more upstream estuary has also experienced long-term declining biomass trends, particularly of cladocerans and rotifers,
although calanoid copepods have increased since the early 1990s due to the introduced Pseudodiaptomus spp. In addition, mysid biomass has dropped significantly throughout the estuary. Shifts in zooplankton species composition
have also been accompanied by an observed decrease in mean zooplankton size and an inferred decrease in zooplankton food quality.
These changes in the biomass, size, and possibly chemical composition of the zooplankton community imply major alterations
in pelagic food web processes, including a drop in prey quantity and quality for foraging fish and an increase in the importance
of the microbial food web for higher trophic levels. 相似文献
18.
<正>A new specimen assigned to the species Iverya averyi gen.nov.and sp.nov.is described.This species is considered as a triadotypomorphan insect,a poorly known group of Triassic stem-odonatans.Like other triadotypomorphans,this species exhibits an area between MA and MP that is comparatively broad,and a cubitoanal area involving an AA stem distinct from CuA+CuP+AA emitting several posterior branches.Diagnostic character states of the new species are listed.Although incomplete,the specimen provides new information on the wing morphology of triadotypomorphans.This discovery might contribute to better assessment of the phylogenetic position of triadotypomorphan species with respect to other stem-odonatans. 相似文献
19.
Biogeochemical investigation of Tamarix aphylla,a plant species, of the Las-bela area has been made.This area mainly consists of ophiolites associated with sed-imentary rocks of Jurassic and Cretaceous age .Quantitative estimations of important biogenic trace elements such as Fe,Mn,Pb,Zn,Cu,Cr,Ni, and Co have been carried out .Anomalous concentrations of these elements in plant species of certain regions can be used to locate possible occurrences of ore deposits in the area.The comparative strdy also reveals appreciable variations in the composition of trace elements in plants.The possible causes of variation in the constitrents of Tamarix aphylla from different localities have been discussed in the light of bed rock nature, mo-bility of element and average abundance in the plant. 相似文献
20.
Karen Helen Wiltshire Alexandra Kraberg Inka Bartsch Maarten Boersma Heinz-Dieter Franke Jan Freund Christina Gebühr Gunnar Gerdts Karina Stockmann Antje Wichels 《Estuaries and Coasts》2010,33(2):295-310
The Helgoland Roads time series is one of the richest temporal marine data sets available. Running since 1962, it documents
changes for phytoplankton, salinity, Secchi disc depths and macronutrients. Uniquely, the data have been carefully quality
controlled and linked to relevant meta-data, and the pelagic time series is further augmented by zooplankton, intertidal macroalgae,
macro-zoobenthos and bacterioplankton data. Data analyses have shown changes in hydrography and biota around Helgoland. In
the late 1970s, water inflows from the south-west to the German Bight increased with a corresponding increase in flushing
rates. Salinity and annual mean temperature have also increased since 1962 and the latter by an average of 1.67°C. This has
influenced seasonal phytoplankton growth causing significant shifts in diatom densities and the numbers of large diatoms (e.
g. Coscinodiscus wailesii). Changes in zooplankton diversity have included the appearance of the ctenophore Mnemiopsis leidyi. The macroalgal community also showed an increase in green algal and a decrease in brown algal species after 1959. Over 30
benthic macrofaunal species have been newly recorded at Helgoland over the last 20 years, with a distinct shift towards southern
species. These detailed data provide the basis for long-term analyses of changes on many trophic levels at Helgoland Roads. 相似文献