Goniatite

About: Goniatite is a research topic. Over the lifetime, 115 publications have been published within this topic receiving 3012 citations. The topic is also known as: Goniatite.

Devonian eustatic fluctuations in Euramerica

Abstract: The Devonian System of Euramerica contains at least 14 transgressive-regressive (T-R) cycles of eustatic origin. These are separated into three groups (or depophases) and from Carboniferous cycles by three prominent regressions. Twelve post-Lochkovian T-R cycles are recognized, and they commonly appear to result from abrupt deepening events followed by prolonged upward shallowing. Deepening events in the western United States (especially Nevada), western Canada, New York, Belgium, and Germany have been dated in the standard conodont zonation and are demonstrably simultaneous in several or all five regions. This synchroneity indicates control by eustatic sea-level fluctuations rather than by local or regional epeirogeny. Facies shifts in shelf sedimentary successions are more reliable indicators of the timing of sea-level fluctuations than are strandline shifts in the cratonic interior, because the latter are more influenced by local epeirogeny. Strandline shifts are most useful in estimating the relative magnitude for sea-level fluctuations. Devonian facies progressions and the three prominent regressions are of a duration and an order of magnitude that could have been caused by episodes of growth and decay of Devonian oceanic ridge systems. The described T-R cycles could have formed in response to mid-plate thermal uplift and submarine volcanism. The latter process may have been a control on small-scale (1–5 m thick), upward-shallowing cycles within the major T-R cycles. Continental glaciation could have been a factor in sea-level fluctuations only in the Famennian and could not have been responsible for the Devonian facies progressions or the numerous T-R cycles. The Frasnian extinctions were apparently cumulative rather than due to a single calamity. Two rapid sea-level rises occurred just before, and one at, the Frasnian-Famennian boundary. It is probable that this series of deepening events reduced the size of shallow-shelf habitats, caused repeated anoxic conditions in basinal areas, and drowned the reef ecosystems that had sustained the immensely diverse Devonian benthos.

Recent developments in Carboniferous geology: a critical review with implications for the British Isles and N.W. Europe

Abstract: Significant increases in our understanding of Carboniferous geological and geographical processes, including plate tectonics, palaeomagnetism, climatology and sea level changes have occurred in recent years. Further advances will increasingly depend on the accurate determination of radiometric ages for the boundaries of the major Carboniferous stratigraphie subdivisions. The recent 39 Ar/ 40 Ar dating of sanidines from European Silesian tonsteins holds out great hopes that structural, igneous and metamorphic events dated by radiometric methods can be better correlated with stratigraphie events defined by goniatite zonation. Palaeomagnetic and tectonic studies in the European Hercynides have established that the Upper Palaeozoic geological evolution of the British Isles took place to the north (present coordinates) of an active micro-plate collision zone along the Galician-Brittany-Massif Central line. Lithospheric stretching of the British/Irish Hercynian ‘foreland’ in the Lower Carboniferous was followed by a belt of north-migrating crustal shortening which disrupted the thermal sag phase of extensional subsidence in northern Britain from Westphalian C times onwards. Backstripped subsidence curves for north British Carboniferous basins indicate that subsidence may have occurred in response to lithospheric thinning of up to 50%. The proposal that there was crustal extension and limited seafloor spreading between Greenland and Scotto-Scandinavia along the Rockall/Faroes line during Carboniferous times is discussed and it is suggested that strike-slip tectonics, known to have been active in Maritime Canada may have played a more important role. Radiometric studies of detrital zircons reveal that the nature of the sourcelands for the huge amounts of Carboniferous detritus in the northern British Isles changed little during the course of the period. They were dominated by outcrops of post-Archaean sediments, minor Archaean basement and abundant Caledonian granitoids with little evidence for Proterozoic crustal growth in the hinterlands. A combination of Mid-Carboniferous climatic change, to a more humid regime, and granite/gneiss terrane unroofing, substantially explains the flushing-out of huge amounts of feldspathic detritus in the Namurian. This Carboniferous climatic change itself must have been influenced by the growth of the E-W Hercynian mountain chain and the accompanying fusion of Gondwanaland with Pangea. Some palaeomagnetic evidence also exists for latitudinal shift at this time. Perhaps the most important influence was the early Namurian expansion of the great Gondwanan ice centre. Waxing and waning of this on a Milankovich time scale dominated Silesian sea level changes and facies evolution. Many late Dinantian and Silesian ‘minor’ sedimentary cycles are probably of glacio-eustatic origins, but there seems little evidence that supposed Dinantian and Namurian mesothemic cycles have such an origin. There are, in fact, increasing doubts as to the actual existence of these particular cycles.

The carboniferous goniatites of the north of england and their zones

Abstract: Stratigraphy. The Carboniferous strata consist, except near the shore lines of that age, of two clearly marked divisions: a lower division, consisting mainly of clear water deposits (Mountain Limestone) and an upper division (Millstone Grit and Coal Measures), almost entirely composed of beds of detrital origin. When, however, the sequence is examined more closely it is seen that the details of the lithological succession vary greatly in different areas, and hence arises doubt and hesitation in correlating widely separated areas. The work of zoning the lower (Mountain Limestone) division by means of its contained fossils made great strides in Britain in the opening decade of the century, mainly through the researches of the late Dr. A. Vaughan. The main zonal divisions of the Lower Carboniferous propounded by him and based on the coral sequence, are now generally accepted as a basis for the correlation of widely separated deposits in North West Europe. His views on the succession exposed in the North of England formed Dr. Vaughan’s last paper, published in the Proceedings of this Society for 1916 (Vol. XIX, Part II, p. 41 et seq .). In Britain and Western Europe generally, the oncoming of the coarse detrital deposits of Upper Carboniferous time drove out the coral fauna, and this group is, therefore, not available as a time-index for the Upper Carboniferous rocks. We are, therefore, compelled to turn to other groups more or less abundantly preserved in these beds, namely the lamellibranchs and goniatites. The researches of the late Dr. …

Sedimentary and faunal changes across the frasnian/famennian boundary in the canning basin of Western Australia

Abstract: The Canning Basin of northwestern Australia is a key area for understanding global changes at the “Kellwasser Events” and the Frasnian‐Famennian boundary. Frasnian stromatoporoid‐coral‐cyanobacterial reef platforms stretched out for enormous distances along the palaeoshelf but in the early Famennian they were completely replaced by cyanobacterial reef platforms. An iridium anomaly in the sequence was formerly believed to be at or close to the boundary and was interpreted as possible evidence for an asteroid impact. Recent field work and detailed biostratigraphy in the area east and southeast of Fitzroy Crossing has given dating relevant to the timing and extent of sea level changes, hypoxic incursions and reef backstepping. Goniatites and conodonts provide correlations with the international biostratigraphy. In the Horse Spring area the stage boundary falls within the Virgin Hills Formation which normally has a rich pelagic goniatite, nautiloid and conodont fauna. In the latest Frasnian (Zone 13 of Klappe...