A Late Ordovician to middle Wenlockian graptolite sequence from a borehole within the Rathkenny Tract, eastern Ireland, and its relation to the paleogeography of the Iapetus Ocean

1994 ◽  
Vol 31 (3) ◽  
pp. 608-616 ◽  
Author(s):  
Alfred C. Lenz ◽  
Alan P. M. Vaughan
Keyword(s):  
Deep Water ◽  
Late Ordovician ◽  
Iapetus Ocean ◽  
Biostratigraphic Units

A borehole drilled within the Rathkenny Tract, southwest of Navan, eastern Ireland, yielded a rich graptolite fauna, including three excellent basal Silurian graptolite assemblages, from a deep-water, pelagic and hemipelagic sequence, ranging in age from uppermost Caradocian to middle Wenlockian, from immediately below Carboniferous strata. Biostratigraphic analysis of the graptolites shows that there are eight, discrete faunal (biostratigraphic) units, and these, together with the lithology, indicate the graptolite-bearing sequence is mostly inverted and faulted at several levels.Biogeographic affinities of several of the Llandoverian and of the Wenlockian graptolite species, as well as some lithological data, suggest that the Rathkenny Tract lay on the southeast side of the Iapetus Ocean. The presence of the youngest graptolites further suggests that some element, at least, of the Iapetus Ocean, though probably narrow by this time, was clearly still in existence until at least middle Wenlockian.

Tectonic and paleogeographic significance of Late Ordovician conodonts in the Canadian Appalachians

1997 ◽  
Vol 34 (11) ◽  
pp. 1521-1537 ◽  
Author(s):  
Godfrey S. Nowlan ◽  
Alexander D. McCracken ◽  
Malcolm J. McLeod
Keyword(s):  
New Brunswick ◽  
Deep Water ◽  
Late Ordovician ◽  
Orogenic Belt ◽  
Eastern Canada ◽  
Global Pattern ◽  
Iapetus Ocean ◽  
Group A ◽  
Sedimentary Succession ◽  
Canadian Appalachians

Conodonts of Late Ordovician age are well represented in Laurentian parts of eastern Canada, but are rare in the Appalachian orogenic belt. They are known from the Anticosti Basin, the Matapedia Belt, and the Exploits Subzone of the Dunnage Zone. Two new discoveries are described: one from unnamed strata on Markey Brook, west-central New Brunswick, and one from the Goss Point Formation (Avalon Zone, southwestern New Brunswick). Faunas from the Anticosti Basin are of undoubted Midcontinent Faunal Region affinity. Those from the Matapedia Belt are highly mixed both paleoecologically and provincially, containing elements of shallow- and deep-water Midcontinent affinity and elements typical of the Atlantic Faunal Region. Faunas from the Exploits Subzone and Markey Brook are also mixed, suggesting endemic faunas of Atlantic affinity with local influx of Midcontinent faunas from Laurentia. The Goss Point Formation, previously believed to belong to the Mascarene Group (a Silurian cover sequence on the Avalon Zone), also yields mixed faunas. Provincial mixing of all faunas east of the Anticosti Basin suggests that Late Ordovician faunas around Iapetus Ocean may have been more homogeneous than earlier Ordovician faunas. Therefore, the Iapetus Ocean may have been smaller or current patterns may have changed to permit trans-Iapetan migration. A strong global pattern of provincialism for Late Ordovician conodonts is recognized and a new Australasian Province is proposed. Conodonts permit identification of a previously unrecognized Ordovician volcano-sedimentary succession that has economic and tectonic implications for the region.

A rock volume accumulation curve for the late Ordovician-Silurian Welsh Basin

1994 ◽  
Vol 131 (4) ◽  
pp. 539-544 ◽  
Author(s):  
Chris J. Clayton
Keyword(s):  
Climate Change ◽  
Large Scale ◽  
Late Ordovician ◽  
Tectonic Uplift ◽  
Sudden Increase ◽  
Submarine Fan ◽  
Accumulation Curve ◽  
River Capture ◽  
Iapetus Ocean ◽  
Rate Of Sedimentation

AbstractA rock accumulation curve is presented for the Ordovician-Silurian Welsh Basin, based on the volume of sediment entering the basin during each graptolite biozone. Even allowing for its inherent uncertainties, the curve still illustrates a significant and sudden increase in the rate of sedimentation in early Silurian time. This may be explained by submarine fan migration, large scale climate change, or river capture in the hinterland, but is most likely caused by tectonic uplift at source. This would support models for either an early Silurian, or late Ordovician closure of the Iapetus Ocean

Deepwater occurrence of a new Glyptocrinus (Crinoidea, Camerata) from the Late Ordovician of southwestern Ohio and northern Kentucky: revision of crinoid paleocommunity composition

2015 ◽  
Vol 89 (6) ◽  
pp. 1068-1075 ◽  
Author(s):  
Jack W. Kallmeyer ◽  
William I. Ausich
Keyword(s):  
New Species ◽  
Deep Water ◽  
Late Ordovician ◽  
Suspension Feeding ◽  
Depth Gradient ◽  
Facies Distribution ◽  
Deposit Feeders ◽  
Kope Formation ◽  
A New Species ◽  
Water Facies

AbstractA new crinoid association reported from the Kope Formation (Katian, Ordovician) of northern Kentucky and southwestern Ohio changes the model for facies distribution of crinoids along an Ordovician onshore-offshore depth gradient. Glyptocrinus nodosus n. sp., Plicodendrocrinus casei (Meek, 1871), Cincinnaticrinus varibrachialis (Warn and Strimple, 1977), and Ectenocrinus simplex (Hall, 1847) are reported from a suspension-feeding assemblage with 26 taxa. This assemblage developed above an argillaceous packstone with most of the fossils preserved in shale. The fauna was comprised principally of secondary epifaunally tiered suspension feeders, deposit feeders, and predators. This is the first reported occurrence of Glyptocrinus Hall, 1847 and Plicodendrocrinus Brower, 1995 from the Kope Formation (lower Cincinnatian), and Glyptocrinus is represented by a new species, G. nodosus. Also, this is the first report of pinnulate camerate crinoids from the deep-water facies of the Kope Formation. Thus, deep-water Cincinnatian crinoid assemblages were comprised of disparids, cladids, and camerates; and the assemblage was characterized by a variety of filtration fan types for acquisition of resources.

scholarly journals <i>Kinnekullea comma</i> (Jones, 1879), a trans-Iapetus ostracod locum for the late Ordovician <i>Dicellograptus anceps</i> graptolite Biozone

2000 ◽  
Vol 19 (2) ◽  
pp. 163-164 ◽  
Author(s):  
M. Williams ◽  
J. D. Floyd ◽  
C. G. Miller ◽  
D. J. Siveter ◽  
P. Stone
Keyword(s):  
Late Ordovician ◽  
Iapetus Ocean ◽  
Marine Facies ◽  
Ostracod Species

Abstract. The ostracod Kinnekullea comma occurs in the upper part of the Cautley Mudstone Formation (Ashgill Series) in the Cautley district of northern England, thus geographically extending the stratigraphical value of K. comma as a locum for the Dicellograptus anceps graptolite Biozone in Ordovician shelly marine facies of Britain and Ireland. Its occurrence, in Scotland and England, confirms it as one of the earliest trans-Iapetus Ocean ostracod species.

Late Ordovician trilobites from the Mayatas Formation, Atansor area, north-central Kazakhstan

2016 ◽  
Vol 107 (1) ◽  
pp. 33-52
Author(s):  
L. M. E. McCobb ◽  
L. E. Popov
Keyword(s):  
South China ◽  
Deep Water ◽  
New Genus ◽  
Late Ordovician ◽  
Active Margin ◽  
North Central ◽  
Area North

ABSTRACTTwo trilobite faunas of Late Ordovician (Katian) age are described from the Mayatas Formation in the Stepnyak region of north-central Kazakhstan. The older, oligotaxic fauna derives from flanks of a carbonate build-up, and is dominated by numerous Sphaerexochus specimens. Amphilichas is also relatively common, with Pliomerina and indeterminate asaphids present as rare components. The overlying unit of siliceous argillites contains a different assemblage, representing the raphiophorid biofacies and comprising seven genera. The poorly preserved fauna is dominated by blind trilobites (a new genus of trinucleid, the three-segmented raphiophorid Pseudampyxina, Malongullia?, Lonchodomas and Arthrorhachis) and at least two species of large-eyed Telephina, suggesting that they occupied the disphotic zone in deep water offshore. A single cranidium of the odontopleurid Primaspis is also present. The trinucleid, Iputaspis stepnyakensis gen. et sp. nov., has an unusual pit arrangement, with E1 and E2 aligned in sulci and all I arcs irregularly arranged. The Atansor area is located within the Stepnyak tectonostratigraphical unit, which probably represented an Ordovician active margin of the Kalmykkol–Kokchetav Microplate. Some of the genera represented in the faunas have affinities with Australia and South China and, also, there is a possible link to European peri-Gondwana.

scholarly journals Identifying the most surprising victims of mass extinction events: an example using Late Ordovician brachiopods

2017 ◽  
Vol 13 (9) ◽  
pp. 20170400 ◽  
Author(s):  
Seth Finnegan ◽  
Christian M. Ø. Rasmussen ◽  
David A. T. Harper
Keyword(s):  
Deep Water ◽  
Mass Extinction ◽  
Late Ordovician ◽  
Extinction Rate ◽  
Simple Method ◽  
Training Models ◽  
Extinction Event ◽  
Extinction Events ◽  
Mass Extinction Events

Mass extinction events are recognized by increases in extinction rate and magnitude and, often, by changes in the selectivity of extinction. When considering the selective fingerprint of a particular event, not all taxon extinctions are equally informative: some would be expected even under a ‘background’ selectivity regime, whereas others would not and thus require special explanation. When evaluating possible drivers for the extinction event, the latter group is of particular interest. Here, we introduce a simple method for identifying these most surprising victims of extinction events by training models on background extinction intervals and using these models to make per-taxon assessments of ‘expected’ risk during the extinction interval. As an example, we examine brachiopod genus extinctions during the Late Ordovician Mass Extinction and show that extinction of genera in the deep-water ‘ Foliomena fauna’ was particularly unexpected given preceding Late Ordovician extinction patterns.

Late Ordovician brachiopod biofacies of the Girvan district, SW Scotland

2000 ◽  
Vol 91 (3-4) ◽  
pp. 471-477 ◽  
Author(s):  
David A. T. Harper
Keyword(s):  
South China ◽  
Deep Water ◽  
Late Ordovician ◽  
Outer Shelf ◽  
Tectonic Events ◽  
Environmental Fluctuations ◽  
Laurentian Margin

ABSTRACTDiverse and abundant brachiopod faunas, associated with unstable outer shelf and slope environments, occur through the Upper Ardmillan Group (upper Caradoc–upper Ashgill) in the Girvan district of SW Scotland. Representatives of the deep-water Foliomena fauna occur intermittently throughout the group, appearing in both the Whitehouse and Drummuck subgroups. This distinctive assemblage of small, thin-shelled brachiopods, including Dedzetina, Christiania, Cyclospira and Foliomena itself, first appeared in South China during the early Caradoc but had colonised the Laurentian margins by the late Caradoc. Within the upper Caradoc–lower Ashgill Whitehouse Subgroup, the Foliomena fauna is interbedded with a variety of other less cosmopolitan deep-water assemblages including the Onniella–Skenidioides and Lingulella–Trimurellina associations. Shallower-water environments in the middle Ashgill Lower Drummuck Subgroup hosted the Fardenia–Eopholidostrophia association in sands, and the Christiania-Leptaena association in muds and silts. The remarkable Lady Burn Starfish Beds in the upper part of the group contain a variety of brachiopod-dominated assemblages including the Eochonetes and Plaesiomys-Schizophorella associations, transported from various shelf locations, within a very diverse mid-Ashgill biota. Nevertheless, elements of the Foliomena fauna persisted to near the top of the Drummuck Subgroup, occurring as rare assemblages in more muddy and silty facies. The upper Ashgill High Mains Formation contains abundant elements of the terminal Ordovician Hirnantia fauna including Eostropheodonta, Hindella and Hirnantia itself, but also some taxa more typical of the Laurentian Edgewood Province. As a whole, the changing brachiopod biofacies monitor environmental fluctuations, on part of the Laurentian margin, driven by mainly eustatic and tectonic events.

The location of the Iapetus Ocean suture in Newfoundland

1977 ◽  
Vol 14 (3) ◽  
pp. 488-495 ◽  
Author(s):  
W. S. McKerrow ◽  
L. R. M. Cocks
Keyword(s):  
Lower Devonian ◽  
New World ◽  
Late Ordovician ◽  
Calc Alkaline ◽  
The West ◽  
Early Devonian ◽  
Iapetus Ocean ◽  
Lower Palaeozoic ◽  
First Time ◽  
Avalon Peninsula

Brachiopod and trilobite faunal distributions indicate that the Iapetus Ocean was still wide enough to inhibit migration in the Middle and Late Ordovician. The presence of Silurian and Lower Devonian calc-alkaline rocks suggests that ocean crust was still being subducted long after the end of the Ordovician and that the Iapetus Ocean did not finally close in Newfoundland until the Acadian Orogeny. The Reach Fault divides successions containing different Lower Palaeozoic faunas; to the west, typical North American faunas occur in New World Island (Cobb's Arm Limestone), while to the east the rocks of the Gander region appear to have been attached to the Avalon Peninsula, with its European Lower Palaeozoic faunas, since the Early Ordovician. It is concluded that the Reach Fault marks the suture where the Iapetus Ocean closed at the end of the Early Devonian. This line probably extends across Newfoundland to the south of Buchans, and links up with the Cape Ray Fault in the southwest of the island. An Ordovician fauna from the Davidsville Group of the Gander area is illustrated for the first time; it is not clearly definitive of any faunal province.

A revised correlation of Silurian rocks in the Girvan district, SW Scotland

2002 ◽  
Vol 93 (4) ◽  
pp. 383-392 ◽  
Author(s):  
James D. Floyd ◽  
Mark Williams
Keyword(s):  
Depositional Environment ◽  
Late Ordovician ◽  
Important Research ◽  
British Geological Survey ◽  
Marine Fauna ◽  
Comprehensive Review ◽  
Iapetus Ocean ◽  
Northern Side ◽  
Lower Palaeozoic ◽  
Early Palaeozoic

ABSTRACTIn late Ordovician and early Silurian times, the Girvan district lay in a shelf marinesetting on the margin of Laurentia, on the northern side of the Iapetus Ocean. The Lower Palaeozoic rocks of the Girvan district, and their shelly and graptolitic fossil fauna, were systematically described by Lapworth in 1882 and have formed an important research resource ever since. They provide valuable evidence for the depositional environment and geological setting of Girvan during the early Palaeozoic, in both regional and wider contexts, and demonstrate the long-recognised close affinity with contemporaneous Laurentian faunas. However, by late Ordovician and into Silurian times, the earlier Iapetus oceanic barrier to faunal migration had largely gone and there is good correlation between contemporaneous marine fauna throughout the British Isles and Scandinavia. Despite much recent research in the area, including resurvey work by the British Geological Survey, no comprehensive review of Silurian lithostratigraphy at Girvan has been published since the revision by Cocks and Toghill in 1973. The present review of the Silurian rocks addresses this need and complements the recently published (Fortey et al. 2000) revision of the underlying Ordovician rocks, thus bringing the entire Girvan Lower Palaeozoic succession up to modern standards of nomenclature.

Sign in / Sign up

Export Citation Format

Share Document