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1.
Recent field work in Lower Cretaceous successions of the Agadir-Essaouira region, western High Atlas, Morocco, have resulted in 489 belemnite guards collected bed-by-bed from the lower Valanginian – upper Hauterivian interval. These findings are described and discussed in their biostratigraphic, taxonomic, palaeoecologic and palaeobiogeographic context. The most common belemnite genera, Hibolithes, Vaunagites?, and Duvalia, are of Meditteranean affinities and closely related to Spanish, French, and Bulgarian faunas. Less common taxa include Pseudoduvalia and Berriasibelus. The genus Pseudobelus, however, common in southeastern France and southern Spain, is rare in the Moroccan sections. The palaeoecological interpretation of these observations result in the recognition of three belemnite assemblages, characterizing different marine settings: 1) A Hibolithes - Duvalia assemblage which is typical for inner to middle shelf settings. These are relatively shallow marine environments with a high input of siliciclastics. 2) A Duvalia - Hibolithes assemblage of the outer shelf setting. Duvalia spp. is the most common genus, Hibolithes spp. is less common, while Berriasibelus spp. and Pseudobelus spp. are rare. 3) A Duvalia - Pseudobelus assemblage of hemi-pelagic preference. Duvalia is most common, next is Pseudobelus. 相似文献
2.
Eleanor Nye Susanne Feist-Burkhardt David J. Horne Andrew J. Ross John E. Whittaker 《Cretaceous Research》2008,29(3):417-444
In 2001 a partial skeleton of an Iguanodon was discovered in the Upper Weald Clay (Barremian, Early Cretaceous) at Smokejacks Brickworks near Ockley, Surrey, UK. When the dinosaur was excavated, a detailed stratigraphic section was logged and 25 samples taken for palynological and micropalaeontological (ostracod and megaspore) analysis, including a detailed sample set of the dinosaur bed itself. Qualitative and quantitative analysis of the palynoflora revealed rich and well-preserved non-marine assemblages of pollen and spores, including early angiosperms, and freshwater green algae. Four types of angiosperm pollen are described and assigned to the genus Retimonocolpites Pierce, 1961, but left in open nomenclature. Some marine elements such as dinoflagellate cysts are identified as the result of reworking of Middle and Upper Jurassic sediments. The pollen/spore assemblages depict a vegetational change from principally gymnosperm-dominated assemblages at the base to principally pteridophyte-dominated assemblages at the top of the section. The dinosaur bed shows a pteridophyte-dominated assemblage, with a significantly high amount of the freshwater green alga Scenedesmus novilunaris He Cheng-quan et al., 1992. Samples close to the dinosaur bed yielded the first useful ostracod finds from Smokejacks Brickworks: well-preserved assemblages containing Cypridea clavata (Anderson, 1939), Damonella cf. pygmaea (Anderson, 1941), Stenestroemia cf. cressida Anderson, 1971 and Stenestroemia sp. A, and fragments and damaged valves of a thin-shelled ostracod, possibly belonging to Mantelliana Anderson, 1966. Those identified as Cypridea clavata show a wide range of morphological variety and in opposition to Anderson's (1967, 1985) taxonomic scheme, which would assign them to up to five different taxa, they are considered to be intraspecific variants of a single species. The possibilities and limitations of age determination of the Wealden sediments using palynomorphs and ostracods are discussed; distinct forms of early angiosperm pollen, together with the ostracod fauna, are consistent with an early Barremian age. Pollen and spores are discussed in terms of their parent plants and the reconstruction of vegetation and palaeoclimate. Palynology and ostracods give evidence for temporary freshwater conditions at the time when the Iguanodon died and the carcase was buried. 相似文献
3.
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
4.
Upper Cretaceous sediments of the Kanguk Formation exposed in Eidsbotn and Viks Fiord grabens on Devon Island, Nunavut, Canadian High Arctic, yielded 91 fossil marine diatom species and varieties (including indeterminate taxa), representing 41 genera. Excellent preservation of the assemblages was aided by shallow burial, protection in downfaulted linear grabens, and the presence of abundant volcanic material. Planktonic species and resting spores comprise nearly 70% of the diatom assemblage, and provided abundant food resources for the Late Cretaceous Arctic ecosystem. Deposition of the approximately 225 m-thick stratigraphic sequence was predominantly in a shallow marine neritic setting, with an upward progression to interbedded terrestrial deposits of the Expedition Fiord Formation, reflecting a regression and eventual persistence of terrestrial facies into the Early Cenozoic. The Kanguk Formation is widespread across the Canadian Arctic, and diatom biostratigraphy indicates a Santonian–Campanian age for the sequences reported herein, based on the presence of Gladius antiquus in the lowermost strata and occurrence of Costopyxis antiqua throughout the succession. However, Amblypyrgus sp. A and Archepyrgus sp. aff. A. melosiroides, encountered in the lower part of the succession, are known exclusively from the Lower Cretaceous. This may suggest a slightly older age. New information on shallow shelf diatom assemblages from this study is compared to reports on two other Late Cretacous Arctic diatom assemblages. These three sites represent an environmental transect from shallow to distal shelf settings and into the oceanic realm. 相似文献
5.
Marcela Cichowolski Beatriz G. Waisfeld Norberto E. Vaccari Larisa Marengo 《Geological Journal》2015,50(6):764-782
A single confidently dated species of cephalopod is so far known in the Tremadocian of the southern Central Andean Basin (NW Argentina and southern Bolivia). This species belongs to the Eothinoceratidae and has a strong affinity mainly with Avalonia. During the Floian, a notable increase in diversity took place, with the appearance of a variety of families represented by several genera, in particular, within the Family Eothinoceratidae. In addition to the previously described species from southern Bolivia, we evaluate the other records of that family from the Central Andean Basin, and propose the following new taxa: Saloceras sikus sp. nov., Saloceras quena sp. nov., Mutveiceras gen. nov., and Mutveiceras cienagaensis sp. nov. We also describe Margaritoceras diploide, Margaritoceras sp., and Mutveiceras sp. From a palaeogeographic perspective, the cephalopod fauna shows affinities mainly with those of England, Wales, and the Montagne Noire (cold water Gondwana and peri‐Gondwana). As with other cephalopod faunas of mid to high palaeolatitudes, eothinoceratids occur along with other cephalopods forming assemblages of low morphological diversity. We interpret the forms described here as demersal with a subvertical poise, but capable of making rapid buoyancy changes, living in a wide spectrum of shallow offshore to shoreface settings. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
6.
In this study we report similar biotic response patterns in planktic foraminiferal assemblages, whether in association with volcanism, impacts or climate change at the end of the Cretaceous and early Tertiary. During and after each type of catastrophe two groups dominate high stress assemblages: (1) the small Guembelitria species, which are interpreted as having thrived in eutrophic surface waters where other species rarely survived; and (2) the low oxygen tolerant small Heterohelix species, which thrived at times of an expanding oxygen minimum zone associated with high nutrients and a stratified water column. The ecosystem collapse appears to be primarily the result of high macro- and micronutrient influx (from impacts, volcanism and erosion) leading to eutrophication and phytoplankton blooms (i.e., primary producers) that result in toxic conditions for foraminifera. Once nutrients decrease due to consumption by phytoplankton, the first opportunistic foraminifera, the Guembelitria, appear and graze on phytoplankton, rapidly reproduce (heterochronic acceleration) and increase populations exponentially. With nutrient depletion Guembelitria populations rapidly decrease leading to ecologic niches for other generalists and ecosystem recovery. Small low O2 tolerant heterohelicid populations mark this second stage, followed by small trochospiral and planispiral species. With further environmental recovery, increasing competition, niche development, and restoration of a well-stratified watermass, oligotrophic conditions are restored opening habitats for large, highly specialized species and a return to normal diverse assemblages. Such highly stressed ecological successions are observed in association with mantle plume volcanism in the Indian Ocean, Andean volcanism in Argentina and shallow inland seas in Egypt and Madagascar during the late Maastrichtian, the K-T impact, volcanism during the early Danian, and intense upwelling and climate extremes. We present a simple model to explain the ecological succession and recovery phases that follow major biotic perturbations. 相似文献
7.
Although much effort has been put into attempts to unravel the Mesozoic ophiuroid fossil record, surprisingly little attention has been paid to the geological history of family-level compositions of brittle star assemblages. Here, we describe new ophiuroid material from the Late Oxfordian Bure Member as exposed in a construction site along the federal Highway A16 (Transjurane Highway) near Boncourt–Queue au Loup (Swiss Jura Mountains). The remains are exceptionally well preserved and partially articulated, enabling detailed morphological observations at a level comparable to Recent material. Three species are identified; they are here shown to display unequivocal affinities with extant ophiuroid lineages. The assemblage comprises a new ophiacanthid genus and species, Juracantha hottingeri, which is closely related to extant Ophientrema, an ophiolepidid close to extant Ophiozonella described here as a new genus and species, Eozonella bergeri, and a species previously described as Ophiacantha? francojurassica, which is here reassigned to the extant ophionereidid genus Ophiodoris. The assemblage was found in association with Nanogyra oyster buildups encrusted by serpulids and associated with partially-articulated crinoids, deposited in a shallow subtidal setting. Its family level composition is highly unusual with respect to modern equivalents, and instead is reminiscent of modern bathyal assemblages. 相似文献
8.
P.F. Riches 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(3):293-300
The first occurrence and presence of the bivalve Macoma balthica in the Pleistocene shallow marine sediments (Crags) of East Anglia has long been used to characterise the youngest “Weybourne” or “Wroxham” Crag Formation of Early to early Middle Pleistocene age. A review of recent work on the morphological variation and genetic lineages of living populations of the species and of work on fossil discoveries in East Greenland suggests that the current palaeontological species definition is too narrow, that the species arrived in the Atlantic about 2.4 Ma and much earlier than is envisaged from the studies of the North Sea Basin, and that there were several trans-Arctic migrations of the species during the Pleistocene. This paper reviews these findings and concludes that: (i) detailed morphometric analyses of fossil Macoma species from the Crag need to be undertaken and the species definitions comprehensively reviewed to take account of the morphological and genetic variation seen in modern populations; (ii) detailed morphometric analysis of modern M. balthica should be undertaken and tied to the different genetic lineages, and (iii) the current palaeontological definition of Macoma balthica should not be relied on as the basis for a First Appearance Datum (FAD) in the Southern North Sea basin. 相似文献
9.
Simon K. Haslett 《Geological Journal》1992,27(4):339-347
Three previously described species and two new species of rhaxellid microscleres, Rhaxella winspitensis sp. nov. and R. elongata sp. nov., are described from cherts collected from the Cherty Series of the Portlandian of Dorset. The classification of Rhaxella is reviewed, retaining the genus within the family Geodiidae Gray. The results of this study suggest that three time-dependent rhaxellid assemblages can be recognized which, despite being restricted to certain depositional environments, may have biostratigraphic applications. A Portlandian assemblage described here is species-rich in comparison with known Oxfordian-Kimmeridgian assemblages. Bajocian-Callovian assemblages contain only R. sorbyana. The increased faunal diversity with time is speculatively described by an evolving Rhaxella lineage. 相似文献
10.
龙凤山藻属(Longfengshania)由叶状体、柄和固着器三部分组成,类似高等植物根、茎、叶的器官分化,分别营光合作用、支撑藻体和固着功能,营海底固着生活。关于其形态学特征,特别是关于它的系统分类一直存在不同看法。根据形态学特征、个体发育中的生物重演律,以及古生态、古气候特征等认为,该属更接近于褐藻门海带目海带科的一些分子,似为海带目的早期原始类型。由于该属藻体较小,叶状体(叶片)全缘无褶皱或刻裂,固着器不分枝足状,与海带科也有较大区别,加之时代久远,在海带目中另立一科也是适宜的,经过适当修订后,进一步确认了龙凤山藻科的存在。对龙凤山藻属与龙凤山藻科的定义进行了重新修订,初步解决了它们的系统分类问题,为古藻类的早期演化提供了化石证据,具有生物学上的重要意义。概述了海藻类各门、纲、目及科级藻类的一般形态学特征,以供对比研究时参考,从而为确定龙凤山藻属的系统分类提供依据。 相似文献
11.
OLE BENNIKE KAREN LUISE KNUDSEN NIELS ABRAHAMSEN JENS BÖCHER HOLGER CREMER BERND WAGNER 《Boreas: An International Journal of Quaternary Research》2010,39(3):603-619
Bennike, O., Knudsen, K. L., Abrahamsen, N., Böcher, J., Cremer, H. & Wagner, B. 2010: Early Pleistocene sediments on Store Koldewey, northeast Greenland. Boreas, Vol. 39, pp. 603–619. 10.1111/j.1502‐3885.2010.00147.x. ISSN 0300‐9483. Marine Quaternary deposits, here named the Store Koldewey Formation, are found at ～120 m above sea level in northeast Greenland (76°N). The sequence is referred to the Olduvai normal polarity subchron at 1.95–1.78 Ma BP based on palaeomagnetic studies (palaeomagnetically reversed), amino acid epimerization ratios and evidence from marine and non‐marine fossils. The sediments and the fauna show that the sequence was deposited on a mid or inner shelf, and some elements of the marine mollusc and foraminiferal assemblages indicate water temperatures between ?1 and +1 °C and seasonal sea ice cover during deposition. Mean summer air temperatures were around 6 °C higher than at present, as demonstrated by the occurrence of southern extralimital terrestrial species. Well‐preserved remains of land plants indicate that the adjacent land area was dominated by sub‐arctic forest‐tundra with the trees Larix and Betula, shrubs, herbs and mosses. Most of the species represented as fossils have recent circumpolar geographical ranges. An extinct brachiopod species and an extinct gastropod species have been found, but the other macrofossils are referred to extant species. The brachiopod is erected as a new genus and species, Laugekochiana groenlandica. Correlation of the Koldewey Formation with the Île de France Formation farther to the north is suggested. Member A of the Kap København Formation in North Greenland is referred to the Late Pliocene, whereas Member B of the Kap København Formation is suggested to be slightly older than the Store Koldewey Formation. 相似文献
12.
A New Species Group in the Genus Tanytarsus van der Wulp(Diptera:Chironomidae)Based on a Fossil Record from Baltic Amber 总被引：1，自引：1，他引：0
Wojciech GI?KA 《《地质学报》英文版》2010,84(4):714-719
<正>A new fossil chironomid,Tanytarsus serafini,found in Baltic amber is described and illustrated based on adult males.The new species and similar extant species of the genus Tanytarsus van der Wulp are compared. Due to several distinct characters of wing,legs and hypopygium,a new species group for Tanytarsus serafini is proposed,and its diagnostic features are evaluated. 相似文献
13.
云南现代真蕨类植物资源丰富,蕨类植物多样性的地史起源,必须从化石记录入手。在云南临沧上中新统邦卖组植物化石采集中发现了槲蕨属1块不育叶和2块腐殖叶的新材料,这些标本为修订Drynaria propinqua Wen et al.,2013,以及揭示该种不育叶和腐殖叶的特征提供了新的材料。通过与槲蕨属国内外报道的化石种和现生种的详细比较,将其重新定名为Drynaria cf.propinqua。Drynaria cf.propinqua的发现,表明云南临沧晚中新世的气候与现今中国西南地区温暖湿润的气候类似,这些附生植物的生活习性表明,临沧地区复杂分层的森林生态系统至少在晚中新世已经确立。 相似文献
14.
The diagnosis of Estherites corrugatus from the basal part of the Coniacian Second Member of the Nenjiang Formation in Nenjiang County, north-east China is revised following the application of a new preparation technique to some of the carapaces and an examination of specimens under a scanning electron microscope, both of which revealed morphological features on the carapace that had not been recognized previously. Restudy of the type species of the two subgenera Estherites (Euestherites) and Estherites (Parestherites) also revealed details of carapace features not seen hitherto. These indicate that they should be separated from Estherites. As a result, Euestherites is upgraded to genus level and Parestherites is placed in synonymy. The importance of Estherites and Euestherites is considered in the context of Late Cretaceous assemblages of these crustaceans and the three conchostracan provinces (South-West, South-East and North China) that are recognized to have been present in China during the Turonian–Santonian period. 相似文献
15.
16.
Two species of fossil Catenicellid Bryozoa are described from Holocene sediments of the west coast of Maharashtra. Catenicella nagaonensis is reported as new species and the other Catenicella conteii (Audouin) has a cosmopolitan distribution. Catenicellid bryozoans withstand high current action and they are reported elsewhere
from current-dominated settings. Along the West coast in certain localities such as Akshi, Nagaon, Chikhla, Sion and Revdanda
these species occur in moderate percentage. Their occurrence suggests prevalence of fairly high current speed in the past.
C. conteii is a typical tropical to warm water species occurring in the depth range of 18–25 m, indicating a shallow water origin for
the shell limestones and black plastic muds. 相似文献
17.
The history of investigation of the common Jurassic and Cretaceous genus Pseudotorellia Florin (Ginkgoales) represented by needle-shaped, narrow linear or lanceolate leaves bearing several veins and characterized
by a single type of epidermis, is considered. An extended diagnosis of the genus and its taxonomic composition with regard
to the epidermal characters are reported; the stratigraphic and geographical range of its species and the genus evolution
are refined. Three new species Pseudotorellia asiatica N. Nosova et Kiritchkova, sp. nov., P. ketoviana N. Nosova et Kiritchkova, sp. nov., and P. samylinae N. Nosova et Kiritchkova, sp. nov. described from the Lower Jurassic (Toarcian) sediments, are proposed as the correlative
taxa within the Caspian oil and gas province. The stratotype and reference sections of the Lower Jurassic sediments in the
Mangyshlak Mountains are reported for the first time. 相似文献
18.
Victor Zochhuana Ralte R. P. Tiwari Lalchawimawii J. Malsawma 《Journal of the Geological Society of India》2011,77(4):328-348
An interesting selachian fish assemblage having stratigraphic and palaeoecological significance is being described from the
two intraformational calcareous conglomeratic horizons within the Upper Bhuban unit of Bhuban Formation, Surma Group (Lower
to Middle Miocene). The assemblage consists of eighteen species of selachian fishes including two new ones (Carcharhinus bhubanicus and Hemipristis unidenticulata) belonging to thirteen genera and another thirteen forms have been identified up to generic level. It is dominated by the
families Carcharhinidae and Lamnidae, and is one of the most diversified Miocene assemblages from the Indian subcontinent.
The fish fauna and the associated mega-invertebrates suggest Lower Miocene (Aquitanian - Burdigalian) age for the Upper Bhuban
unit of Bhuban Formation. These further suggest that the fish yielding horizons were deposited under a warm shallow marine
set-up near to the shoreline in a high-energy environment. 相似文献
19.
Three new species within the stigmaphronid genus TagsmiphronEngel and Grimaldi, 2009, and one new species within the megaspilid genus ConostigmusDahlbom, 1858 are described from Upper Cretaceous (Campanian) amber originating at the Grassy Lake locality in Alberta, Canada. New taxa include Tagsmiphron spiculum sp. nov., Tagsmiphron leucki sp. nov., Tagsmiphron exitorum sp. nov., and Conostigmus cavannus sp. nov. The new Conostigmus species is a rare discovery. It is the third megaspilid species to be found in Cretaceous amber, with the two specimens described herein effectively doubling the number of known Mesozoic exemplars for the family. We provide the first comprehensive report of known Ceraphronoidea within Canadian amber, and contrast this against other Cretaceous amber assemblages, discussing the potential palaeobiogeographic and palaeoenvironmental implications of the Canadian amber assemblage. 相似文献
20.
The taphonomic features and paleoecology of this species were investigated focused on vertically embedded individuals of articulated Inoceramus amakusensis Nagao et Matsumoto. In the Hinoshima Formation, Himenoura Group of Kyushu, Japan, this Santonian (Late Cretaceous) inoceramid bivalve characteristically occurs in incised-valley fill siliciclastic marine deposits. Modes of I. amakusensis occurrence and preservation, from in situ (= occurrence in life position) to allochthonous shell fragments, are strongly affected by its paleoecology and depositional environments. Several I. amakusensis (up to 25 cm in shell height) were recovered from bioturbated sandstones associated with storm-influenced deposits. Their commissural planes are almost perpendicular to the bedding plane, with the anterior face oriented downward and the posteroventral portion extending upward. Furthermore, I. amakusensis is morphologically comparable to endobyssate mytilid bivalves today. These results suggest that this Cretaceous species was an orthothetic sand sticker at least during mid-ontogeny that preferentially inhabited a well-oxygenated, nearshore seafloor. I. amakusensis was distributed in various depositional environments and has been regarded as a recliner in offshore muddy substrate. However, the present discovery suggests that it was also well adapted, with an upright life position, to high-energy shallow clastic environments characterized by high sediment supply. 相似文献