摘要:

Rate of sedimentation of theGastrioceras cancellatummarine band (Namurian) is deduced from evidence of shell size, population density, and features of the enclosing sediment. Slowest sedimentation apparently coincided with stagnant water conditions. But in a non‐marine succession (Coal Measures) containing trees fossilised upright and rooted in position of growth, the rate of sedimentation (on the evidence of sediments and fossils) is found to be unrelated to degree of water turbulence (sediments and geochemistry). The upright trees were apparently overwhelmed rapidly by sediments deposited from a succession of floods characterised by a wide range of water turbulenc

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1970.tb01260.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Hudson, J. D.: Algal limestones with pseudomorphs after gypsum from the Middle Jurassic of Scotland.Lethaia, Vol. 3, pp. 11–40. Oslo, January 15th, 1970.Algal limestones from two horizons within the Great Estuarine Series of the Hebrides are described. That from the Mytilus Shales is a typically stromatolitic limestone formed by algal trapping and binding of micrite pellets. Calcite pseudomorphs after gypsum occur along some of the laminae. The limestones from the Lower Ostrea Beds include less regularly‐stromatolitic types, and nodular algal limestones that contain tubes of calcified algae, notablyCayeuxia nodosaAnderson. The algal nodules also yield uncalcified tubes composed of organic material, that are comparable to recentSchizothrix.These algae form inter‐growths similar to those recorded from the recent supratidal deposits of the Bahamas. The algal nodules are often coated with microtufa. Pellet‐ and spheru‐lite‐limestones are associated with the algae, and pseudomorphs after gypsum are again found. Isotopic data on the carbonate‐carbon, and the palaeoecological implications of the algae and the pseudomorphs

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1970.tb01261.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The closely related conodont speciesIdiognathoides noduliferusandIdiognathoides sulcatusunderwent morphologic diversification in the lower Morrowan (Lower Pennsylvanian). The expanding range of variation of the two progenitor species overlapped, producing a completely intergraded morphologic‐continuum. Non‐intergradation and taxonomic differentiation at stratigraphically higher levels in the Morrowan demonstrate that certain morphotypes within the continuum bore the potential of becoming descendant species. The descendant species includeIdiognathoides sinuatus, Idiognathoides macer,andGnathodus bassleri symmetricus,Conventional systematic techniques are inadequate to depict the morphologic complexity and evolution shown by this exam

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1970.tb01262.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Living foraminifers were found associated with seaweed, seagrass, dead coral, crust, and sediment substrates in the hypersaline Abu Dhabi lagoon.Peneroplis planatusis the most abundant living species and it is the most conspicuous dead form in the carbonate sediments. In common with other lagoons of this type, diversity is low and there is a dominance of Miliolina and Rotaliina. The Abu Dhabi lagoon is a modern analogue of fossil lagoonal sediments from the Meso‐zoic and Tertiary of Arabi

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1970.tb01263.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Opportunistic species are not resource‐limited. With favorable events they can increase rapidly in numbers. Such species populations are typically very unstable and may become extinct very quickly. In contrast, equilibrium species populations are resource‐limited and maintain stable population levels. The identification of explosive opportunists in the fossil record is an important means of recognizing animal communities which were primarily controlled by the physical, and not the biotic, environment. In young environments of high physiological stress where animal communities are physically controlled, most species are opportunistic. In old and biologically accommodated communities opportunists are relatively rare. Explosive opportunists can be recognized by means of distributional, relative abundance and fossil occurrence d

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1970.tb01264.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Seven trace‐fossil species are described from the upper part of the Torrowangee Group (Upper Proterozoic) of western New South Wales, and a variety of other traces are illustrated. A few forms occur in the Fowlers Gap Beds, and a more diverse and abundant fauna is recorded from the stratigraphically higher Lintiss Vale Beds. Virtually all the traces are preserved in the plane of bedding, as semi‐reliefs. The named trace fossils all come from the Lintiss Vale Beds, and are as follows:Planolites ballandussp. nov.,Planolites?sp.,Cochlichnus serpenssp. nov.,Gordia?sp.,Torrowangea roseigen. et sp. nov.,Phycodes? antecedent sp.nov., andCurvolithus? davidissp. nov. Three of these species are regarded as feeding burrows (endogene), and are thought to represent the activity of infaunal, worm‐like deposit feeders. Others may be either feeding burrows or crawling trails. There are also a few impressions which seem to be rest marks. A discussion of the significance of the trace‐fossil occurrences is pr

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1970.tb01265.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY