scholarly journals Systematic ichnology of the Middle Ordovician Trenton Group, St Lawrence Lowland, eastern Canada

10.4138/1572 ◽  
1984 ◽  
Vol 20 (1) ◽  
Author(s):  
D. Fillion ◽  
R. K. Pickerill
Keyword(s):  
Eastern Canada ◽  
Middle Ordovician ◽  
Trenton Group

Diachronous tectonic collapse of the Ordovician continental margin, eastern Canada: comparison between the Quebec Reentrant and St. Lawrence Promontory

1994 ◽  
Vol 31 (8) ◽  
pp. 1309-1319 ◽  
Author(s):  
Denis Lavoie
Keyword(s):  
Continental Margin ◽  
Foreland Basin ◽  
Head Group ◽  
Upper Ordovician ◽  
Eastern Canada ◽  
Middle Ordovician ◽  
Carbonate Sedimentation ◽  
Shallow Subtidal ◽  
Thickness Variations ◽  
Trenton Group

The Upper Ordovician Trenton Group of southern Quebec represents the last Taconian foreland basin carbonate unit in the Quebec Reentrant, prior to final collapse of Laurentia's continental margin and its burial under synorogenic flysch. The Trenton Group, either conformably or unconformably, overlies the Black River Group and is in turn conformably overlain by the Utica Shales. The tripartite Trenton carbonate unit records progressive deepening: (1) very shallow to shallow subtidal, (2) shallow to deep carbonate ramp, and (3) shallow to deep outer shelf. Regional facies distribution, lithotectonic elements, and thickness variations indicate that the Trenton shelf was dissected by extensional faults delineating blocks subsiding at various rates. This scenario compares favourably with Taconian foreland basin development in the Middle Ordovician Table Head Group at the St. Lawrence Promontory, Newfoundland. A similar stratigraphic succession and tectono-sedimentary history occurring 10–15 Ma earlier at the St. Lawrence Promontory than in the Quebec Reentrant argues for a primary tectonic control for the demise of carbonate sedimentation at the margin. The diachroneity in the foreland evolution can be related to the irregular morphology of the Laurentia continental margin.

Nucularcidae: a new family of palaeotaxodont Ordovician pelecypods (Mollusca) from North America and Australia

2007 ◽  
Vol 44 (10) ◽  
pp. 1479-1501 ◽  
Author(s):  
John Pojeta Jr. ◽  
Christopher A Stott
Keyword(s):  
New Species ◽  
Type Species ◽  
New Genus ◽  
Late Ordovician ◽  
Eastern Canada ◽  
Middle Ordovician ◽  
New Family ◽  
Central Australia ◽  
Northeastern Usa ◽  
Subjective Synonym

The new Ordovician palaeotaxodont family Nucularcidae and the new genus Nucularca are described. Included in Nucularca are four previously described species that have taxodont dentition: N. cingulata (Ulrich) (the type species), N. pectunculoides (Hall), N. lorrainensis (Foerste), and N. gorensis (Foerste). All four species are of Late Ordovician (Cincinnatian Katian) age and occur in eastern Canada and the northeastern USA. Ctenodonta borealis Foerste is regarded as a subjective synonym of Nucularca lorrainensis. No new species names are proposed. The Nucularcidae includes the genera Nucularca and Sthenodonta Pojeta and Gilbert-Tomlinson (1977). Sthenodonta occurs in central Australia in rocks of Middle Ordovician (Darriwilian) age. The 12 family group names previously proposed for Ordovician palaeotaxodonts having taxodont dentition are reviewed and evaluated in the Appendix.

Reappraisal of the Beekmantown Group sedimentology and stratigraphy, Montréal area, southwestern Quebec: implications for understanding the depositional evolution of the Lower-Middle Ordovician Laurentian passive margin of eastern Canada

2003 ◽  
Vol 40 (2) ◽  
pp. 149-176 ◽  
Author(s):  
O Salad Hersi ◽  
D Lavoie ◽  
G S Nowlan
Keyword(s):  
Temporal Evolution ◽  
High Energy ◽  
Field Application ◽  
Passive Margin ◽  
Coarse Grained ◽  
Energy Conditions ◽  
Eastern Canada ◽  
Middle Ordovician ◽  
Platform Margin ◽  
Depositional Evolution

Detailed lithostratigraphic mapping of the Beekmantown Group of southwestern Quebec has refined the field application of the previously proposed tripartite division of the group (i.e., Theresa, Beauharnois, and Carillon formations). The group is a peritidal-dominated succession that accumulated on the epicontinental Laurentian passive margin. Biostratigraphic data based on conodonts from this group indicate an Early to early Middle Ordovician age and are partially time-correlative with the Wallace Creek to Naylor Ledge strata of the Philipsburg Group, southern Quebec. This conodont biostratigraphy sheds new light on the temporal evolution and depositional framework of the Beekmantown platform. The platform evolved as a distally steepened ramp during deposition of the Theresa Formation and the Ogdensburg Member of the Beauharnois Formation (early to middle Ibexian). Correlative strata of the Philipsburg Group include the Wallace Creek and Morgan Corner formations, which represent outer platform sediments. The coarse-grained sandstone of the Theresa Formation accumulated in the innermost platform, whereas coarse-grained carbonates of the Ogdensburg Member indicate open-marine, subtidal to intertidal carbonate sand shoals. By late Ibexian, the platform developed a pronounced margin where thrombolites flourished under high-energy conditions. These are represented by the thrombolite-rich Hasting Creek and Naylor Ledge formations of the Philipsburg Group. Consequently, a broad lagoon formed on the lee side of the platform margin, where low-energy conditions prevailed and accumulation of burrow-mottled dolostones of the Huntingdon Member of the upper Beauharnois Formation took place. The lagoon became more restricted during the latest stages of the basin fill (Whiterockian), and high intertidal to supratidal sediments of the Carillon Formation were deposited.

A review of Middle Ordovician sedimentation in the St. Lawrence Lowland, eastern Canada

2007 ◽  
Vol 17 (2) ◽  
pp. 135-156 ◽  
Author(s):  
T. L. Harland ◽  
R. K. Pickerill
Keyword(s):  
Eastern Canada ◽  
Middle Ordovician

The Walcott-Rust Quarry: Middle Ordovician trilobite Konservat-Lagerstätten

1999 ◽  
Vol 73 (2) ◽  
pp. 288-305 ◽  
Author(s):  
Carlton E. Brett ◽  
Thomas E. Whiteley ◽  
Peter A. Allison ◽  
Ellis L. Yochelson
Keyword(s):  
New York ◽  
Direct Evidence ◽  
Post Mortem ◽  
Benthic Organisms ◽  
Middle Ordovician ◽  
Trenton Group ◽  
Micritic Limestones

The Walcott-Rust Quarry, at Trenton Falls, New York, has yielded a large number of well-preserved, fully articulated fossils from the lower third of the Middle Ordovician Rust Formation, Trenton Group. Along with three species of the more common trilobites from the Trenton Group, fourteen species of rare and uncommon trilobites are found within a thin package of micritic limestones and shales. The first trilobites with preserved appendages, Ceraurus pleurexanthemus Green, 1832 and Flexicalymene senaria (Conrad, 1842), were described from one layer from this quarry. Unique specimens of Isotelus walcotti UIrich in Walcott, 1918, and Sphaerocorphe robusta Walcott, 1875, were found in the next higher bed. Re-excavation of the quarry yielded information about the taphonomy of the trilobites and stratigraphy of the trilobite layers. Nearly half of the beds surveyed (n = 50) yield direct evidence of obrution (i.e., rapid post-mortem or live burial) of benthic organisms. Unusual anaerobic microenvironments in partially enrolled trilobites of the Ceraurus layer facilitated very early calcification of appendages and other soft parts.

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