Fauna of the lower Beauharnois Formation (Beekmantown Group, Lower Ordovician), Grande-Île, Quebec

1996 ◽  
Vol 33 (8) ◽  
pp. 1132-1153 ◽  
Author(s):  
Sylvain Desbiens ◽  
Thomas E. Bolton ◽  
Alexander D. McCracken
Keyword(s):  
New York ◽  
Head Group ◽  
Faunal Assemblage ◽  
Lower Ordovician ◽  
Assemblage Zone

Lenses of bioclastic packstone and grainstone within the lower dolomite sequence of the Ogdensburg Member, Beauharnois Formation (Beekmantown Group, Lower Ordovician), in the Valleyfield region, Quebec, bear a distinct diverse faunal assemblage. This Isoteloides–Goniotelina–Ribeiria assemblage is characterized by brachiopods Finkelnburgia armanda (Billings) and Finkelnburgia cullisoni Ulrich and Cooper, molluscs Ribeiria calcifera Billings, "Maclurites" affinis (Billings), and Ceratopea canadensis (Billings), and trilobites Isoteloides canalis (Whitfield), Isoteloides peri Fortey, Bolbocephalus convexus (Billings), Goniotelina subrectus (Bradley), Strigigenalis caudata (Billings), and Hystricurus conicus (Billings). Precise correlation of this lower Beauharnois megafauna is with the Strigigenalis caudata Zone of the Catoche Formation, Cassinian Stage, of western Newfoundland, the Oxford Formation of southeastern Ontario, the Fort Cassin Formation, Cassinian Stage, Canadian Series of New York–Vermont, and the Ross–Hintze trilobite Zone G2 of Utah, Upper Ibexian Series (Tulean Stage). Conodonts include Acodus comptus (Branson and Mehl), Acodus delicatus (Branson and Mehl), Colaptoconus emarginatus (Barnes and Tuke), Colaptoconus quadraplicatus (Branson and Mehl), Scolopodus subrex Ji and Barnes, Drepanoistodus angulensis (Harris), and Oepikodus communis (Ethington and Clark). This fauna corresponds to the Oepikodus communis–"Microzarkodina" marathonensis Zone, which has its lowest limit above the middle of Zone G2 in the Ibex area of Utah. In western Newfoundland, the fauna correlates with the Oepikodus communis – Protoprioniodus simplicissimus Assemblage Zone of the Catoche Formation, and the Prioniodus elegans and Oepikodus evae zones in the Cow Head Group.

The earliest Ordovician nematophorid graptolites: taxonomy and correlation

1988 ◽  
Vol 125 (4) ◽  
pp. 327-348 ◽  
Author(s):  
B.-D. Erdtmann
Keyword(s):  
Continental Slope ◽  
Global Scale ◽  
Junior Synonym ◽  
Head Group ◽  
Informal Group ◽  
Green Point ◽  
Assemblage Zone

AbstractThe earliest nematophorid (planktic) dendroid graptolites (Family Anisograptidae) are described and revised from several heterofacial facies sections of the Broom Point Formation, Cow Head Group, western Newfoundland (Broom Point North and St Paul's represent medial to upper continental slope, Martin Point and Green Point distal slope environments). Noting potential conodont recycling in the palaeoslope environments of the proximal Cow Head Group sections, graptolites are the only group of fossils that could not have been subject to post-burial transport. The graptolites belong to an informal group of quadriradiate form-species principally representing two originally related but then diverging phyletic groups: pendent Rhabdinopora Eichwald, 1855 and horizontal to sub-horizontal Staurograptus Emmons, 1855; both being stratigraphically within Assemblage Zone I (emended after Cooper, 1979) of earliest Tremadoc or early Ibexian age (top of Cordylodus intermedius to base of C. lindstromi conodont zones). Assemblage I graptolites offer a higher resolution than coeval conodonts and are a better tool for inter-facies correlations both within the Broom Point Formation and with other graptolitic sequences on a global scale. Form-species of quadriradiate Rhabdinopora rustica (such as ?R. praeparabola and R. parabola) and of Staurograptus dichotomus (e.g. ‘Radiograptus’ or ‘Heterograptus’ flexibilis or ‘Aletograptus’) are interpreted as astogenetic morphs, or as phylogenetically descendant variants of these forms. Upon evidence of late astogenetic insertion of dissepiments in Staurograptus and Anisograptus the names ‘Heterograptus’ and ‘Radiograptus’ are placed into junior synonymy, and ‘Aletograptus’ is regarded a junior synonym of Staurograptus because its post-primary dichotomies are merely delayed distally (or omitted) to be observed exclusively in very mature specimens. The Cow Head Group fauna is compared with earliest nematophorids from Oslo, Norway (Naersnes) and Dayangcha, Jilin, China (Xiaoyangqiao), and a new comprehensive ecostratigraphic zonation for early Tremadoc graptolites is proposed.

Middle Ordovician Table Head Group of western Newfoundland: a revised stratigraphy

1980 ◽  
Vol 17 (8) ◽  
pp. 1007-1019 ◽  
Author(s):  
Colin F. Klappa ◽  
Paul R. Opalinski ◽  
Noel P. James
Keyword(s):  
Carbonate Platform ◽  
Head Group ◽  
Group Status ◽  
Middle Ordovician ◽  
Iapetus Ocean ◽  
Lower Ordovician ◽  
Head Formation ◽  
New Formation

Lithostratigraphic nomenclature of early Middle Ordovician strata from western Newfound land is formally revised. The present Table Head Formation is raised to group status and extended to include overlying interbedded terrigenoclastic-rich calcarenites and shales with lime megabreccias. Four new formation names are proposed: Table Point Formation (previously lower Table Head); Table Cove Formation (previously middle Table Head); Black Cove Formation (previously upper Table Head); and Cape Cormorant Formation (previously Caribou Brook formation). The Table Point Formation comprises bioturbated, fossiliferous grey, hackly limestones and minor dolostones; the Table Cove Formation comprises interbedded lime mudstones and grey–black calcareous shales; the Black Cove Formation comprises black graptolitic shales; and the Cape Cormorant Formation comprises interbedded terrigenoclastic and calcareous sandstones, siltstones, and shales, punctuated by massive or thick-bedded lime megabreccias. The newly defined Table Head Group rests conformably or disconformably on dolostones of the Lower Ordovician St. George Group (an upward-migrating diagenetic dolomitization front commonly obscures the contact) and is overlain concordantly by easterly-derived flysch deposits. Upward-varying lithologic characteristics within the Table Head Group result from fragmentation and subsidence of the Cambro-Ordovician carbonate platform and margin during closure of a proto-Atlantic (Iapetus) Ocean.

Timing- and origin of dedolomite in upper Wappinger Group (Lower Ordovician) strata, southeastern New York

1996 ◽  
Vol 11 (1) ◽  
pp. 113-133 ◽  
Author(s):  
Baiying Guo ◽  
John E. Sanders ◽  
Gerald M. Friedman
Keyword(s):  
New York ◽  
Lower Ordovician

scholarly journals Summary account of the Lower Ordovician (Arenig) graptolite biostratigraphy of the Cow Head Group, western Newfoundland

1987 ◽  
Vol 35 ◽  
pp. 259-270
Author(s):  
S. Henry Williams ◽  
Robert K. Stevens
Keyword(s):  
Continental Margin ◽  
North American ◽  
Repeated Exposure ◽  
Head Group ◽  
Middle Cambrian ◽  
Lower Ordovician ◽  
Evolutionary Step ◽  
American Standard ◽  
Lower Slope

The Cow Head Group is an allochthonous sequence of Middle Cambrian to late Arenig sedimentary brec­cias, limestones and shales deposited in a deep lower slope environment close to a continental margin. Im­bricate thrusting has resulted in repeated exposure of laterally equivalent "proximal" to "distal" facies which may be correlated using graptolitic control in the interbeds. "Proximal" sections are characterised by massive, coarse breccias with interbedded limestones and green/dark grey shales. More distal ex­posures have fewer and thinner breccias and limestones, while the green/grey shales are replaced pro­gressively by red, non-graptolitic ones. Although the succession is by no mean unbroken or complete, it furnishes one of the best and most con­tinuously graptolitic sections through the Arenig. A new zonal scheme is erected for the Cow Head Group, which could prove suitable as a new North American standard. Furthermore, several limestones and siliceous shales have yielded exquisitely preserved isolated material, permitting integration of fine growth detail with complete flattened specimens. With the exception of the uppermost Arenig U. austrodentatus Zone, Arenig graptoloids possess a pro­sicular origin for thl1• The earliest graptoloids with a metasicular origin for the first theca appear in this zone, including Undulograptus, Cryptograptus and Paraglossograptus. This interval, equivalent to Dai of the Australasian scheme, therefore represents a hitherto unrecorded major evolutionary step in graptolite evolution.

Cambrian–Lower Ordovician of SW Quebec–NE New York

2021 ◽  
pp. 1-32
Author(s):  
Osman Salad Hersi ◽  
Ed Landing ◽  
David Franzi ◽  
James Hagadorn
Keyword(s):  
New York ◽  
Sediment Accumulation ◽  
Early Cambrian ◽  
Geological History ◽  
Middle Cambrian ◽  
Early Ordovician ◽  
Lower Ordovician ◽  
History Of ◽  
Rodinia Supercontinent ◽  
Stratigraphic Nomenclature

ABSTRACT The Ottawa aulacogen/graben on the NE US—Canadian (SW Quebec and eastern Ontario) border is a long ENE-trending structure formed with initial late Neo proterozoic rifting of the Rodinia supercontinent. This rifting formed the active spreading arms (New York Promontory and Quebec Reentrant) along the (presently) NE margin of the new Laurentia paleocontinent, with the Ottawa aulacogen commonly regarded as a failed arm of the rifting. However, no sediment accumulation in the aulacogen is recorded until the late early Cambrian subsidence of a SE- trending belt that includes the aulacogen and its extension, the Franklin Basin, in NW Vermont. Late early Cambrian marine onlap (Altona Formation) followed by more rapid late middle Cambrian subsidence and deposition of fluviatile arkoses (Covey Hill Formation of SW Quebec and Ausable Formation/Member of eastern New York) record rapid foundering of this “failed arm.” Subsequent deposition (latest middle Cambrian–Early Ordovician) in the Ottawa aulacogen produced a vertical succession of lithofacies that are fully comparable with those of the shelf of the New York Promontory. One of the greatest challenges in summarizing the geological history of the Ottawa aulacogen is the presence of a duplicate stratigraphic nomenclature with lithostratigraphic names changing as state and provincial borders are crossed.

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