Synchronology

1985 ◽  
Vol 309 (1138) ◽  
pp. 11-27 ◽  
Keyword(s):  
Sea Level ◽  
Quantitative Methods ◽  
Lower Devonian ◽  
Practical Interest ◽  
Radiometric Dating ◽  
Vertebrate Evolution ◽  
Significant Evidence ◽  
Red Sandstone ◽  
Level Curves ◽  
Upper Silurian

Radiometric dating cannot as yet approach the resolution obtainable in Silurian and Devonian biostratigraphy. Progress towards achievement of a global standard for the Wenlock and Emsian interval (against which evolution and environment must be seen) is reviewed. In biostratigraphical correlation with this standard certain groups are especially useful. Correlation between marine Upper Silurian and Lower Devonian rocks and their equivalents in the Old Red Sandstone magnafacies presents particular problems and yet the latter provides significant evidence of plant and vertebrate evolution at this time. The recognition of widespread physical events such as volcanic episodes may sometimes prove useful. Sea level curves seldom provide a precise synchronology not achievable through biostratigraphy. Quantitative methods of correlation are so far of theoretical rather than practical interest.

scholarly journals II - The Acanthodian fishes

1937 ◽  
Vol 228 (549) ◽  
pp. 49-146 ◽  
Keyword(s):  
Lower Devonian ◽  
Good Evidence ◽  
Caudal Fin ◽  
Red Sandstone ◽  
The World ◽  
Upper Silurian ◽  
Devonian Age ◽  
Fin Spines

The Acanthodian fishes form one of the most sharply demarcated and recognizable groups of vertebrate fossils. Their characteristic squamation of square, exceedingly minute ganoid scales, and the fact that all the fins except the caudal fin are supported by large anterior spines, distinguish them sharply from all other fishes, and enable even fragmentary specimens to be recognized without doubt. They are worldwide in distribution, and their range in tim e is thus known with considerable certainty. The first fragments, attributed on very good evidence to the group, are isolated fin spines, found in Upper Silurian rocks perhaps not earlier than the Downtonian, which seem to be identical with those found in complete fishes of Lower Devonian age. The group was more varied in structure and played a larger part in the world in Lower Devonian times than at any other period. Even in the Middle Old Red Sandstone the range in structure had been reduced, and by Carboniferous times very few forms remained.

scholarly journals The Cosheston Group (Lower Old Red Sandstone) in southwest Wales: age, correlation and palaeobotanical significance

1998 ◽  
Vol 135 (3) ◽  
pp. 397-412 ◽  
Author(s):  
C. H. WELLMAN ◽  
R. G. THOMAS ◽  
D. EDWARDS ◽  
P. KENRICK
Keyword(s):  
Lower Devonian ◽  
New Age ◽  
Early Devonian ◽  
Red Sandstone ◽  
South Wales ◽  
Upper Silurian ◽  
Devonian Age ◽  
Sandstone Facies

Upper Silurian–Lower Devonian ‘Lower Old Red Sandstone’ facies deposits cropping out in southwest Wales are poorly age-constrained and difficult to correlate. Spore assemblages have been recovered from sequences of these deposits belonging to the lower part of the Cosheston Group. The spore assemblages are equated with the breconensis–zavallatus and polygonalis–emsiensis Spore Assemblage Biozones and indicate an early Devonian age (late Gedinnian (late Lochkovian)–Siegenian (Pragian)). The new biostratigraphical data enable correlation of the lower part of the Cosheston Group with the Senni Beds from the main outcrop of the Lower Devonian in South Wales and the Welsh Borderland. In addition, the new age data and stratigraphical correlation place important plant megafossil assemblages from the Cosheston Group and Senni Beds in a more secure stratigraphical framework, thus facilitating comparisons with other Lower Devonian plant megafossil assemblages and enhancing palaeobotanical understanding. Evidence from palynofacies analysis supports sedimentological interpretations which suggest that the ‘Lower Old Red Sandstone’ facies deposits belonging to the Cosheston Group accumulated in a continental fluviatile environment.

The aulacopleurid trilobiteMaurotarionAlberti, 1969, in the Silurian-Devonian of Argentina: systematic, phylogenetic and paleobiogeographic significance

2010 ◽  
Vol 84 (6) ◽  
pp. 1082-1098 ◽  
Author(s):  
Juan J. Rustán ◽  
N. Emilio Vaccari
Keyword(s):  
South Africa ◽  
New Species ◽  
Sea Level ◽  
South African ◽  
Lower Devonian ◽  
Relative Sea Level ◽  
African Species ◽  
Level Curves ◽  
New Subgenus ◽  
The Family

Five new species ofMaurotarionAlberti, 1969 from the Silurian Lipeón Formation and Lower Devonian Talacasto Formation of Argentina are recognized. The comparisons with Bolivian and South African species support a Malvinokaffric clade based on librigenal synapomorphies, here erected asMaurotarion(Malvinotarion) new subgenus. The Malvinokaffric origin of the family would not be a migration from lower paleolatitudes but an Early Silurian stock of rare cosmopolitan ancestors which underwent a great Devonian radiation. Two lineages can be recognized within MalvinokaffricMaurotarion.The Silurian-Pragiandereimsilineage is a plesiomorphic one resembling Silurian representatives and involvesM.(Malvinotarion)dereimsi, M.(Malvinotarion)talacastoensenew species,M.(Malvinotarion?) new species A,M.(Malvinotarion?) new species B,M.(Malvinotarion) sp., and eventuallyM. (Malvinotarion?)cf.dereimsi.Theisaacsonilineage ranges from the Lower Pragian to Eifelian exhibiting a defined morphologic trend in the librigena. This lineage comprisesM.(Malvinotarion)isaacsoni, M.(Malvinotarion) sp. A from South Africa,M.(Malvinotarion)gauchonew species,M.(Malvinotarion)haudeinew species andM.(Malvinotarion)legrandi.A Lochkovian diversification probably took place yet an adequate assessment remains difficult. In contrast, a great evolutionary burst is recognized during the Emsian and is related to Pragian-Emsian global relative sea level curves which are coincident with those proposed from Bolivian and Argentinian basins.

Sea level change in the Holocene on the northern Great Barrier Reef

1978 ◽  
Vol 291 (1378) ◽  
pp. 167-186 ◽  
Keyword(s):  
Great Barrier Reef ◽  
Sea Level ◽  
Radiometric Dating ◽  
Barrier Reef ◽  
Sea Levels ◽  
Level Curves ◽  
Level Change ◽  
Fossil Corals ◽  
History Of ◽  
Degree Of Confidence

Detailed studies, utilizing a range of both well controlled sea level criteria and dates, are required if Holocene time-sea level curves are to be established with any degree of confidence. This paper is restricted to an interpretation of Expedition results from the northern Great Barrier Reef, excluding those from the drill core. Extensive colonies of emergent fossil corals in growth position indicate that present sea level was first reached about 6000 a b. p. Elevations of cay surfaces, cemented rubble platforms, microatolls, coral shingle ridges, reef flats and mangrove swamps, referenced to present sea level show an array of heights. However, levels of particular features are accordant on many reefs: it is believed that these can be related to particular sea levels. Radiometric dating provides the time framework. Ages of samples from similar deposits on different reefs are surprisingly consistent. Oscillations in sea level since 6000 a b.p ., relative to present sea level, are identified with varying degrees of confidence. This history of relative sea level does not separate eustatic from noneustatic components.

Notes of a Geologist in Ireland During August and September, 1857

The Geologist ◽  
1858 ◽  
Vol 1 (8) ◽  
pp. 330-335
Author(s):  
W. S. Symonds
Keyword(s):  
Lower Cambrian ◽  
Red Sandstone ◽  
Upper Silurian ◽  
Cover Up

On leaving Dublin, we travelled northwards, for the purpose of examining the carboniferous rocks, and visiting the magnificent collection of fossil-fishes in the museum of the Earl of Enniskillen; we then journeyed south for Killarney and the Dingle district, but as it may be more convenient to the reader to travel geologically, we will reverse the order of our journey, and visit the Upper Silurian and Old Red Sandstone districts before we examine the carboniferous deposits.The lower Cambrian rocks of Wales, of which the Oldhamia-schists of Ireland are believed to be the equivalents, pass upwards by insensible gradations into the Lingula-flags, to which they are altogether conformable. The Lingula-flags are reckoned to be four or five thousand feet thick, and the Llandeilo or Builth-beds, which cover up these, are probably as thick; but geologists are, as yet, uncertain whether they possess in Ireland any true equivalents either of the Lingula-flags or of the Llandeilo and Builth deposits. There are, however, fossiliferous rocks of the Bala and Caradoc age in Ireland similar to those which, in Wales, succeed conformably to the Llandeilo and Builth beds, and they may be examined at Courtown, in the county of Wicklow, and again at Tramore, south of Waterford. They are unconformable to the rocks below, which are undoubtedly Cambrian, and thence, we imagine, has arisen the suspicion that the Lingula-beds and Llandeilo-flags have never been deposited in Ireland, or that if they were, they have been denuded and swept away before the deposition of the Bala or Caradoc strata.

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