Shallow water mud-mounds of the Early Devonian Buchan Group, East Gippsland, Australia

2012 ◽  
Vol 281 ◽  
pp. 208-221 ◽  
Author(s):  
A.-M.P. Tosolini ◽  
M.W. Wallace ◽  
S.J. Gallagher
1964 ◽  
Vol S7-VI (1) ◽  
pp. 121-126 ◽  
Author(s):  
Marie Jose Pavillon

Abstract Marine clastic formations of Cambrian, Ordovician, and Silurian age in the Flamanville area of northwestern France were folded during the Caledonian orogeny into a series of broad anticlinal and synclinal folds with the tops of the anticlines emergent and undergoing erosion by early Devonian time. The earlier Devonian formations were formed by deposition of the detritus in the adjacent synclinal troughs. Later deposits formed after renewed subsidence show facies differences between the marine shallow-water areas of the anticlinal crests, the deeper water of the flanks, and the deepest water of the synclinal troughs. Ferruginous oolite beds occur in marine sandy shales in the northern part of the area, and veinlets of lead-zinc mineralization occur in the southern part. The minerals probably were deposited in the original sediments, and later metamorphosed by intrusion of the Flamanville granite whose contact-metamorphic effects are prominent. The iron mineralization probably was deposited in marine shallows, and the lead-zinc minerals in adjoining belts.


Author(s):  
Victor Voichyshyn

The formation of the Early Devonian ichthyofauna occurred under the combined influence of historical, paleogeographic and paleoecological factors. A consequence of evolutionary development at the beginning of the Devonian period arose a number of high-ranking taxa of sea vertebrates, which actively colonized the shallow water basins of new continent Laurussia. For representatives of local endemic faunas there was an opportunity to expand their habitats. There were exchanges of migrants between neighboring regional faunas. All this was accompanied by the evolution of ecosystems, the formation and development of new ecological niches. Early Devonian for most groups of vertebrates was marked by a sharp increase in the number of taxonomic units. The formation of Podillya regional ichthyofauna illustrates these trends of global biotic changes in that time.


1995 ◽  
Vol 69 (6) ◽  
pp. 1112-1122
Author(s):  
James E. Barrick ◽  
Paula J. Noble

Early Devonian (Lochkovian; eurekaensis Zone) conodonts occur in discontinuous limestone beds in the Caballos Novaculite at five localities in the northwestern half of the Marathon uplift, west Texas. Similar conodont faunas at all five localities indicate that the limestone beds lie at one biostratigraphic horizon within the Caballos. The upper novaculite member directly overlies the limestone horizon at one locality, giving the upper novaculite a maximum age of Lochkovian. The limestone beds are dominantly skeletal calcarenites that represent shallow-water carbonate material transported into a deeper water setting by gravity processes. Restriction of the limestones to the northwestern margin of the uplift and provenance of reworked clasts and redeposited Ordovician and Silurian conodonts suggest a North American shelf source and are evidence of the close proximity of some strata exposed in the Marathon uplift to North America in the Early Devonian. Icriodus gravesi n. sp. is described from the limestone fauna.


Author(s):  
N. H. Trewin ◽  
S. R. Fayers

ABSTRACTMaterial excavated from a trench dug to expose the Rhynie Cherts Unit of the Dryden Flags Formation included blocks of Rhynie chert up to 50 cm thick and comprising the full thickness of plant-bearing chert beds. These blocks, and others collected as float, display a variety of macro-textures typical of silicification at the terrestrial surface and in shallow water. On sandy terrestrial surfaces, autochthonous and allochthonous plant debris and plant rhizomes are well preserved, but aerial axes generally decayed prior to silicification. In shallow water, clonal plants, particularly Rhynia, are preserved with aerial axes in growth position, supported by microbial mats and meshworks. Preservation of such delicate fabrics required the creation of a load-bearing framework early in the silicification process, to prevent crushing during early burial.On the microscale, plant taphonomy reveals characteristic features due to plant decay prior to silicification in both wet and dry conditions, and also during the silicification process. Silicification of plants was frequently very rapid, preserving delicate transient features such as spore germination and ejection of sperm cells from antheridia. In situations where plant tissue continued to decay during silicification, the process was slower.


Sedimentology ◽  
2003 ◽  
Vol 50 (4) ◽  
pp. 743-770 ◽  
Author(s):  
S. J. Mazzullo ◽  
Chellie S. Teal ◽  
William D. Bischoff ◽  
Kimberly Dimmick-Wells ◽  
Brian W. Wilhite

1974 ◽  
Vol 11 (8) ◽  
pp. 1055-1097 ◽  
Author(s):  
D. G. Perry ◽  
Gilbert Klapper ◽  
A. C. Lenz

The Ogilvie Formation, formerly dated as Eifelian and Givetian, is locally confined to the Early Devonian, Emsian. Regionally the top of the Ogilvie is markedly diachronous ranging in age from Emsian to Givetian. The Ogilvie Formation conformably overlies the Late Silurian to Early Devonian Gossage and/or early Emsian Michelle and Cranswick Formations. The stratigraphic thickness of the Ogilvie varies from 200–3500 ft (61–1068 m) over relatively short geographic distances. The ages of the lower and upper beds of the Ogilvie are based on brachiopods, conodonts, corals, and trilobites. Locally, the lower part of the overlying unnamed shale unit is regarded as a lateral equivalent to parts of the younger Ogilvie carbonate sections. The Eifelian age of the basal beds of the unnamed shale unit is derived from a few strategically located dacryoconarid tentaculite collections. The Ogilvie Formation is a shallow water carbonate shelf deposit, locally reefal, which had its most extensive development in the later part of the Emsian. From the later part of the Emsian through Givetian, the carbonate shelf was gradually inundated by shales until in the late Givetian only a very small area of carbonate deposition remained in the western Yukon (Mount Burgess).The brachiopod affinities lie with the Cordilleran Subprovince of the Old World Province and with forms of similar age described from central Nevada. The conodonts and trilobites are correlative with forms from Arctic Islands, eastern Alaska, and Nevada. The Emsian tetracoral fauna is similar to that of the Emsian of eastern Australia whereas the Eifelian fauna is similar to that of other parts of northwestern Canada.Five informal conodont faunal units, ranging in age from Emsian through Eifelian, are proposed for the Michelle–Ogilvie sequence. In addition, the P. varcus Zone (Givetian) is recognized at the top of the Ogilvie at one section.


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