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1.
《International Geology Review》2012,54(7):811-822
The author discusses dimorphism in Egorovella and his new genus Egorovellina. A new term, "marginal dimorphism," is proposed for dimorphism involving a broadening of the marginal surface, as contrasted with "velar" and "histial" dimorphism which refer to modifications of various types of carinal structures. The author suggests that this type of dimorphism may indicate that the males and females lived in different biotopes. Seven new species of Egorovella and the genus and two species of Egorovellina are described and illustrated. --J. M. Berdan. 相似文献
2.
Ischadites lindstroemi Hinde 1884 is described from the Ordovician Daylesford Formation (lower part of the Bowan Park Group) of central western New South Wales. The species characterises a distinctive unit in the formation, occurring in bands throughout the unit. From a study of the associated lithofacies and their stratigraphic distribution in the limestones, an interpretation of the environment in which the species lived is presented. The species is considered to have inhabited a shallow‐water, lime‐mud environment, which was off‐shore and marginal to calcarenite shoals. 相似文献
3.
Marie-Françoise Bonifay 《Quaternary Research》1980,14(2):251-262
This study is the first test of correlation between the results obtained on the large Plio-Pleistocene European faunas and the main climatic stages (cold as well as temperate) demonstrated in marine isotopic records. In particular, there are cold stages which often explain the disappearance of some species, as well as climatic events that promote the substitution of some species by other groups. A rather evident parallelism appears between the European succession of large faunal associations and paleoclimatic stages revealed in oceanic areas, but some discordance occurs in the later periods. Faced with the great diversification of the Quaternary faunas, probably due to the multiplicity of climatic environments, and with global information from oceanic records, only local biostratigraphic studies will allow precise reconstruction of the different biotopes. 相似文献
4.
In the latest Early to Middle Miocene section of the Kingfish 8 well, offshore Gippsland Basin, the characteristically deep‐marine ostracod genus Zabythocypris is a conspicuous component of ostracod assemblages dominated by species of the genera Argilloecia, Krithe and Parakrithe. The taphonomy and taxonomic composition of the assemblages suggests that they accumulated in an upper bathyal environment (500–1000 m water depth) occurring in a lower continental slope setting. Supporting evidence for these deep‐marine ostracod assemblages occurring near the upper limit of their palaeobathymetrical range is the broadly coincident occurrence of the deep‐marine taxa Legitimocythere sp. and Neonesidea whatleyi Warne, in what would otherwise be considered an outer‐shelf (120–160 m) ostracod fauna at Fossil Beach, Mornington. Ostracod occurrences indicative of dysaerobic sea‐floor conditions in the Kingfish 8 well and Fossil Beach sections, when considered together, appear to record a shallowing of the oceanic oxygen‐minimum zone during the latest Early Miocene to earliest Middle Miocene transgressive phase of southeast Australia. 相似文献
5.
Michael G. Michie 《Mathematical Geology》1982,14(6):661-667
Transformation of data effectively limits the distortion by outlying values on the Bray-Curtis similarity measure. It represents an effective method of using cluster analysis in distinguishing biotopes of benthic foraminifera. 相似文献
6.
J. W. Pickett 《Australian Journal of Earth Sciences》2013,60(3):313-320
The distribution, mode of occurrence and population densities of extensive colonies of worms, and the morphology of their thick‐walled tubes are described. Interaction between two species occurring in certain strata enables the feeding habits of the tube‐builders to be reconstructed, and they are thus identified as terebellid worms. The worms when alive were less than 5 mm in diameter and had tentacles 27 mm long. Their environmental situation was near the southern edge of an extensive area of marine deposition covering much of the Sydney Basin. The depth was below wave base. The worm populations were buried alive during deposition of sheets of sediment, probably resulting from intermittent sudden flooding events in coastal rivers. 相似文献
7.
<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
8.
9.
L. G. Bragina 《Stratigraphy and Geological Correlation》2009,17(4):430-442
The work is aimed at summarizing data on Late Cretaceous radiolarians from the Crimean and West Sakhalin mountains. The Cenomanian-lower Coniacian stratigraphic interval of the Crimean Mountains yields 215 radiolarian species, and 80 concurrent species are known from the West Sakhalin Maintains. According to results of comparative analysis, there are 62 species in common from two regions, i.e., most of the species occurring in the West Sakhalin Mountains are also known from southerly regions, which is a good premise for correlation. 相似文献
10.
Palaeoenvironmental change following deglaciation of the last British–Irish Ice Sheet on the continental shelf west of Ireland was investigated using multiproxy analyses of sediment and foraminifera data from nine sediment cores. Lithofacies associations record various depositional regimes across the shelf, which evolve from subglacial to postglacial conditions. Census data provide the first characterisation of benthic foraminifera populations across the continental shelf and multivariate analyses reveal three distinct biotopes. Biomineralization within these biotopes is restricted to ≤21 200 cal a bp by four radiocarbon ages. The transition from glacial to postglacial benthic foraminifera populations near the shelf break marks the establishment of productive, nutrient-rich, ice-distal conditions at ~20 900 cal a bp ; these conditions may also mark the start of favourable conditions for postglacial cold-water coral growth. Postglacial conditions on the inner shelf were not established until <14 500 cal a bp , suggesting glacial conditions west of Ireland may have persisted into the Bølling–Allerød Interstadial. 相似文献
11.
Based on rock and fossil data from the Upper Cretaceous of the El Hassana Dome (Abu Roash, Egypt), factors controlling facies architecture and the nature of biotopes are highlighted. The succession formed on a non-rimmed shelf, the architecture of which varied from an inner to an outer shelf setting upsection. Macrobenthic biotopes are reconstructed and their palaeoecological significance assessed using a novel ternary plot. Based on diversity and community structure (770 specimens assigned to 28 bivalve and gastropod taxa), four paucispecific associations are identified. These are: 1. the ‘Cucullaea’ Assemblage, a low-energy, soft-substrate, oligotrophic outer shelf environment with reduced terrigenous input dominated by infaunal bivalves and hexactinellid sponges; 2. the ‘Plicatula’ Assemblage, a low-energy, restricted inner shelf lagoonal setting with soupy substrates and dysoxia below the sediment-water interface dominated by plicatulid and ostreid bivalves, 3. the ‘Durania’ Assemblage, a high-energy, high-temperature, shoal environment dominated by elevator rudists with minor numbers of echinoids, corals and bryozoans, which together form several biostromes. and 4. The ‘Trochactaeon’ Assemblage, which share the same characteristics of the ‘Durania’ Assemblage. The paucispecific nature of these biotopes is indicative of different stress factors. Consequently, the predominant taxa exhibit different degrees of adaptive strategies. In addition to global sea level, local tectonics have significantly affected facies distribution and biotope structure. The shallower facies during the early Turonian and the dysoxia spanning the Coniacian–Santonian were linked to synsedimentary tectonics, which formed many barriers and led to circulation restrictions. 相似文献
12.
Highly resolved pollen spectra analysed from a 47 cm peat monolith recovered from a mire in northern Sweden exhibit climatic sensitivity in the pollen accumulation rates (PAR) of boreal treeline species. Robust temporal control, afforded through multiple AMS radiocarbon dating of the post‐atomic‐bomb‐test period (AD 1961–2002), provides a unique opportunity to compare pollen accumulation rates with the instrumental meteorological record. Strong correlations are observed between summer temperature and PAR for Pinus sylvestris, Picea abies and Betula spp. (excluding B. nana). Despite well constrained, contiguous (‘annual’) sampling, the temporal resolution of the pollen signal preserved within each sample appears to be degraded to ca. 3–5 year resolution. This is likely to reflect processes occurring during peat accumulation and pollen deposition, as well as dating uncertainties and the effects of subsampling. These findings identify limitations to the maximum resolution that may realistically be recovered from the peat archive using high‐resolution sampling protocols and AMS 14C dating. We also identify the need for additional work to quantify the role of climate on peat accumulation and the resultant impact on assemblage‐based palaeoenvironmental reconstructions within mire sequences. The strongest climate association observed for Picea abies (r = 0.53; n = 36) was extended through the monolith beyond the 42 year period of ‘annual’ sampling and the response successfully correlated with the Bottenviken historical instrumental record to AD 1860. Although only presenting data from a single site, and requiring wider replication, we conclude that for sites close to the ecological limits of tree species, where levels of anthropogenic/non‐climatic forcing on pollen production are low, well‐dated records of PAR may potentially provide a proxy for reconstructing past summer temperature variability. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
13.
To test the potential for developing sub‐decadal resolution records of ombrotrophic bog surface wetness (BSW), selected abrupt climate events were identified in cores from four sites in north‐west Europe and time‐slices over each event were investigated at 2–5‐mm resolution using peat humification, testate amoeba and plant macrofossil analyses. Age–depth models based on radiocarbon, spheroidal carbonaceous particle and tephra dates were applied and the error in these models was used to determine the effective temporal sampling resolution, which in most cases was sub‐decadal. Fine‐resolution results revealed some inconsistencies in the co‐variability of individual proxies and there was a lack of correspondence between some results from adjacent cores. However, we found evidence of abrupt shifts in BSW occurring over ca. 5–20 years, indicating a more rapid proxy response than identified in previous research. To maximize potential temporal resolution and produce reliable sub‐decadal BSW data in future research, we recommended that peat‐based studies should obtain the best possible chronological control, focus on sites with high species diversity and rapid accumulation rates and perform replicate coring, or use open peat sections where the stratigraphy can be clearly seen, to assess intra‐site differences in microtopography. Site‐specific factors should be a primary consideration in the selection of sites for future fine‐resolution research. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
14.
Adam Toma&#x;ových Ivo Gallmetzer Alexandra Haselmair Darrell S. Kaufman Borut Mavri
Martin Zuschin 《Sedimentology》2019,66(3):781-807
Carbonate sediments in non‐vegetated habitats on the north‐east Adriatic shelf are dominated by shells of molluscs. However, the rate of carbonate molluscan production prior to the 20th century eutrophication and overfishing on this and other shelves remains unknown because: (i) monitoring of ecosystems prior to the 20th century was scarce; and (ii) ecosystem history inferred from cores is masked by condensation and mixing. Here, based on geochronological dating of four bivalve species, carbonate production during the Holocene is assessed in the Gulf of Trieste, where algal and seagrass habitats underwent a major decline during the 20th century. Assemblages of sand‐dwelling Gouldia minima and opportunistic Corbula gibba are time‐averaged to >1000 years and Corbula gibba shells are older by >2000 years than shells of co‐occurring Gouldia minima. This age difference is driven by temporally disjunct production of two species coupled with decimetre‐scale mixing. Stratigraphic unmixing shows that Corbula gibba declined in abundance during the highstand phase and increased again during the 20th century. In contrast, one of the major contributors to carbonate sands – Gouldia minima – increased in abundance during the highstand phase, but declined to almost zero abundance over the past two centuries. Gouldia minima and herbivorous gastropods associated with macroalgae or seagrasses are abundant in the top‐core increments but are rarely alive. Although Gouldia minima is not limited to vegetated habitats, it is abundant in such habitats elsewhere in the Mediterranean Sea. This live–dead mismatch reflects the difference between highstand baseline communities (with soft‐bottom vegetated zones and hard‐bottom Arca beds) and present‐day oligophotic communities with organic‐loving species. Therefore, the decline in light penetration and the loss of vegetated habitats with high molluscan production traces back to the 19th century. More than 50% of the shells on the sea floor in the Gulf of Trieste reflect inactive production that was sourced by heterozoan carbonate factory in algal or seagrass habitats. 相似文献
15.
Material behaviour that exhibits characteristics of creep induced by a spontaneous mineral dissolution enhanced by material damage is studied. It is believed that the characteristic rates of the chemical processes involved determine the time‐rate dependence of the resulting strain. A basic model of a combined chemo‐plastic softening and chemically enhanced deviatoric strain hardening for saturated geomaterials is presented. Chemical softening is postulated to occur as a consequence of the net mass removal resulting from dissolution and precipitation of specific minerals occurring at the damage‐generated inter‐phase interfaces. Closed and open systems are discussed. In the former case, deformation at constant stress results entirely from a local compensation mechanism between the chemical softening and strain hardening. The classical three stages of creep are interpreted in terms of mechanisms of dissolution and precipitation, as well as the variation in the reaction surface areas involved in the mass exchange. In an open system, the above local mechanism is enhanced by the removal of mass via diffusion of species affecting the mass balance. Such a system is addressed via a boundary value problem as shown in an example. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
16.
Udo Dreiser 《GeoJournal》1994,32(1):55-60
The results of the research at the Sudan Red Sea coast, which is part of the GTZ project Integrated Biological Control of Grasshoppers and Locusts will be presented. For detecting desert locust biotopes multitemporal Landsat Thematic Mapper data and ground truth information are analyzed. The Normalized Difference Vegetation Index (NDVI) shows the areas covered with vegetation. These areas are masked and then classified with the maximum likelihood classifier. Rectification and ground truthing are carried out by means of a GPS (Global Positioning System). The results of the multitemporal classification are merged with an enhanced satellite scene. The final map shows the potential desert locust biotopes. The current desert locust breeding area can be demarcated by combining the classification results with up-to-date data from monitoring satellites, such as Meteosat and NOAA. Further research is carried out in Mali and Mauritania. 相似文献
17.
The interdisciplinary North Sea Project aims at investigating the biotic history of the Pleistocene in the Southern Bight of the North Sea. Humans were part of these biotopes too as Palaeolithic flint artefacts prove. Based on a large fossil record and radiocarbon dating, it becomes clear that reindeer was part of the Late Pleistocene Mammoth-fauna.Upper Palaeolithic hunters often are described as reindeer-hunters. Despite a large fossil reindeer record and collection of Palaeolithic flint artefacts, no evidence was found for co-existence of humans and reindeer or for reindeer-hunting. 相似文献
18.
Late Palaeozoic glaciation in Australia, discovered over a century ago, is now known to have covered a large part of the continent. In South Australia, tillite and outwash debris lie upon clearly striated pavements within glacial valleys, and show that ice sheets with valley tongues moved northward from sources now occupied by deep ocean south of the continent. These glaciers reached into the Cooper, Arckaringa, and Pedirka Basins at the end of the Carboniferous and laid down patches of till in the Early Permian, now preserved largely in the subsurface. In Tasmania, an ice sheet waxed in the latest Carboniferous from sources to the west of the island, and deposited till and “drop‐stones” into fossiliferous marine strata until well into the Late Permian. In Victoria, the ice cap laid down till on a striated floor, and here and there sequences of outwash, including boulder pavements. In New South Wales, continental glaciation expanded eastward to the sea early in the Permian, and left a record intercalated with volcanics and coal beds into the Late Permian. Bordering the Tamworth Trough of northern New South Wales, and occurring also in the highlands of New England, alpine glaciers left a record in the form of striated stones and dropstones, in very thick sequences of fluviatile, lacustrine, and marine clastic sediments. The mountains existed in Middle and early Late Carboniferous times, and were largely worn down to gentle relief when continental glaciers expanded northward in the Early Permian. A non‐glacial interval at the end of the Carboniferous therefore probably occurred in New South Wales. In Queensland, alpine glaciers occupied mountains at the western rim of the Bowen Basin at the end of the Carboniferous. Large blocks carried by icebergs from glaciers of unknown locations were dropped into Lower and Upper Permian strata of the Bowen Basin as well. In Western Australia Early Permian ice centres were located on the Yilgarn Block, east of the Perth Basin, on the Pilbara Block southwest of the Canning Basin, and on the Kimberley Block. Evidence for this glaciation consists mostly of ice‐rafted debris and fluvial‐glacial and glacial‐marine strata that reached as far north as the Bonaparte Gulf Basin. The rapid growth northward of continental glaciers in Australia near the end of the Carboniferous corresponds with a rapid shift of palaeolatitude as judged from Irving's palaeomagnetic studies. The ice sheet grew quickly upon upland areas when Gondwanaland moved to a near polar position and the unfrozen Palaeo‐Pacific lay near at hand to provide an abundant source of moisture. 相似文献
19.
豫西—皖北地区二叠纪植物地理区系性质探讨 总被引：1，自引：0，他引：1
基于对豫西－皖北地区和华北、华南二叠纪植物化石分布状况的全面对比统计,简略分析了豫西－皖北地区二叠纪植物群演替,将该区各阶期与华北及华南同期植物群进行了工对其间Simpson相似性系数作了求算。结果表明它应作为华夏植物各华北植物区内的一个次级植物地理单元对待其成因与华北、华南二叠纪时古板块的旋转、漂移、聚散等行为及其特定的古地理条件密切相关。 相似文献
20.
A buried archaeological site at Tecolote Canyon provides an ideal case study for relating past human land use patterns to changes in coastal paleogeography. Postglacial sea level transgression, erosion, and other marine and fluvial processes form the context for examining two deeply buried archaeological components excavated at CA‐SBA‐72. Archaeological shellfish assemblages provide proxy data for evaluating the evolution of local marine environments. Pismo clams dominate shellfish assemblages dated to 5800 cal yr B.P., suggesting the presence of a broad and sandy, high‐energy beach environment. At 5500 cal yr B.P., the almost exclusive use of California mussels by humans signals the development of rocky intertidal habitats. During the late Holocene, estuarine species dominate the marine mollusk assemblages at CA‐SBA‐72, reflecting the development of local estuarine conditions or trade with nearby Goleta Slough villages. The buried components at Tecolote Canyon appear to have served as temporary camps for shellfish harvesting and processing. While general changes in coastal paleogeography and human subsistence have been reconstructed for the Santa Barbara Coast, high resolution ecological data from Tecolote Canyon suggest that Native peoples also adapted to localized and shorter‐term shifts in intertidal habitats, changes not evident in most larger or more disturbed surface sites in the region. Linking these changes with shifts in human land use patterns highlights the interaction between humans and a dynamic coastal system. These data demonstrate the importance of small, buried sites in understanding the full spectrum of human subsistence and settlement choices and local environmental change. © 2004 Wiley Periodicals, Inc. 相似文献