منابع مشابه
Division Rhyniophyta - Upper Silurian to Middle Devonian
Among the oldest convincing fossils of early vascular land plants are those of the Division Rhyniophyta. The members of this division consist of: (1) simple axes with cuticle, stomates, epidermis, cortex and a terete (circular) centrarch xylem (xylem development occurs from the center of the stem to the periphery), without well-developed appendages or roots; (2) simple, isotomous branching syst...
متن کاملPopulation structure of graptolite assemblages
Graptolite rhabdosomes display a diverse suite of morphologies. The range of morphotypes present within most moderate to high diversity assemblages from the Ordovician and Silurian is similar, despite the different taxonomic composition of the faunas at different times. Survivorship analyses of graptolite faunas from the Ordovician and Silurian demonstrate strong similarities in the mortality r...
متن کاملThe State of Silurian
The geological sciences demand close international cooperation as wel as a rigorous and clearly understood language of words. Nowhere is this more keenly felt than in stratigraphy where, despite the luxury of long philosophical discussions on rocks versus time, many feel a sense of urgency about attempts to achieve a standard global chronostratigraphy. The now wel-known pioneer work of the inte...
متن کاملA Silurian 'marrellomorph' arthropod.
Xylokorys chledophilia, a new arthropod with three-dimensionally preserved soft tissues, is described from the Herefordshire (Silurian) Lagerstätte of England. The head and trunk are covered by a relatively featureless ovoid carapace, which comprises a domed central part and a flange-like border. The head bears five pairs of appendages. The first is uniramous, with dorsal and ventral projection...
متن کامل28 Investigating Upper Mantle Discontinuities Beneath Subduction Zones
Subduction zones can be regarded as natural laboratories because of the wide variety of processes involved. Macquarie Island is an exposed portion of the Macquarie Ridge, and is located where the Australian plate meets the Pacific plate. To its north is the Tonga trench, where the old Pacific floor subducts at a rapid rate below the Indo-Australia plate, producing a deep slab of former oceanic ...
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ژورنال
عنوان ژورنال: Geological Magazine
سال: 1945
ISSN: 0016-7568,1469-5081
DOI: 10.1017/s001675680007802x