Graptolites from the Lower–Middle Ordovician St. George and Table Head groups, western Newfoundland, and their correlation with trilobite, brachiopod, and conodont zones

1987 ◽  
Vol 24 (3) ◽  
pp. 456-470 ◽  
Author(s):  
S. Henry Williams ◽  
W. Douglas Boyce ◽  
Noel P. James
Keyword(s):  
Head Group ◽  
Middle Ordovician ◽  
Faunal Assemblages ◽  
Head Groups ◽  
Brachiopod Fauna ◽  
Lower Slope

Faunal assemblages of the autochthonous, shelf carbonate sequences belonging to the St. George and Table Head groups are dominated by shelly macrofossils and conodonts. Rare, usually monotypic graptolitic horizons enable correlation with the allochthonous Cow Head Group, which was deposited on the middle to lower slope, and the shelly, conodont, and graptolitic zonal schemes elsewhere in North America.The Catoche Formation of the St. George Group is of Ibexian (Canadian) age and yields graptolites indicative of the Tetragraptus approximatus and Tetragraptus akzharensis zones (early Arenig). The basal Aguathuna Formation belongs to the Pendeograptus fruticosus Zone, whereas higher parts span the Ibexian–Whiterock boundary. Graptolites suggest that the Table Head Group entirely postdates the Cow Head Group. This is supported by a Whiterock (early Llanvirn) trilobite, conodont, and brachiopod fauna.

Cambrian and Ordovician linguliform brachiopods from the Shallow Bay Formation (Cow Head Group), western Newfoundland

2001 ◽  
Vol 75 (2) ◽  
pp. 241-260 ◽  
Author(s):  
Sean P. Robson ◽  
Brian R. Pratt
Keyword(s):  
New Species ◽  
Continental Slope ◽  
Head Group ◽  
Lower Paleozoic ◽  
Middle Cambrian ◽  
Middle Ordovician ◽  
Upper Cambrian ◽  
Three New Species ◽  
Brachiopod Fauna ◽  
Shallow Bay

Linguliform brachiopods were recovered from the Upper Cambrian Downes Point Member (lower Sunwaptan) and from the Middle Ordovician Factory Cove Member (Arenig) of the Shallow Bay Formation, Cow Head Group, of western Newfoundland. These rocks are a series of Middle Cambrian to Middle Ordovician conglomerates, lime mudstones, and shales that formed a sediment apron at the base of the lower Paleozoic continental slope of Laurentia. The linguliform brachiopod fauna consists of sixteen species assigned to twelve genera. Three new species are described: Picnotreta lophocracenta, Neotreta humberensis, and Siphonotretella parvaducta.

Integrated chitinozoan, conodont, and graptolite biostratigraphy from the upper part of the Cape Cormorant Formation (Middle Ordovician), western Newfoundland

2001 ◽  
Vol 38 (3) ◽  
pp. 387-409 ◽  
Author(s):  
Roberto Albani ◽  
Gabriella Bagnoli ◽  
Jörg Maletz ◽  
Svend Stouge
Keyword(s):  
Early Stage ◽  
Foreland Basin ◽  
Black Shales ◽  
Head Group ◽  
Middle Ordovician ◽  
Head Groups ◽  
Taconic Orogeny ◽  
Low Diversity ◽  
Conodont Fauna ◽  
Abundance And Diversity

The Cape Cormorant Formation of the Table Head Group exposed on the Port au Port Peninsula, western Newfoundland, is composed of dark-brown to black shales with interbeds of thin calcareous silty and sandy distal turbidites. Distinctive carbonate conglomerates and breccias derived from the foundering shelf are occasionally found in the formation. The sediments accumulated in the foreland basin formed during the early stage of the Taconic orogeny. The faunas from the upper part of the Cape Cormorant Formation include graptolites, conodonts, and chitinozoans. The graptolites are well preserved, but are of low diversity and are referred to the Darriwil Pterograptus elegans Zone. Conodonts recorded from the distal turbidites are rare and fragmented. The faunas include taxa that are known from the St. George and Table Head groups. The conodont fauna is tentatively assigned to the Histiodella kristinae Phylozone and to the younger, unzoned interval. The chitinozoans are well preserved and the yield is high. The fauna is assigned to the Cyathochitina jenkinsi Zone and to an undefined interval. The abundance and diversity of the chitinozoan assemblages display a cyclic pattern, which is related to changes of the oceanic watermass in the foreland basin. The new chitinozoan species Belonechitina nevillensis n. sp., Belonechitina uniformipunctata n. sp., and Cyathochitina cormorani n. sp. are described.

Brachiopod biostratigraphy of the middle Ordovician Cow Head and Table Head groups, western Newfoundland

1987 ◽  
Vol 24 (1) ◽  
pp. 70-95 ◽  
Author(s):  
Reuben J. Ross Jr ◽  
Noel P. James
Keyword(s):  
Shallow Water ◽  
Water Table ◽  
Deep Water ◽  
Head Group ◽  
Middle Ordovician ◽  
Head Groups

Brachiopods from shallow-water limestone boulders in beds 12, 13, and 14 of the allochthonous Cow Head Group belong in the earliest Whiterockian Orthidiella Zone. Brachiopods of the autochthonous intertidal to deep-water Table Head Group are equivalent to those of the younger Whiterockian Anomalorthis Zone. The Cow Head is older than the Table Head.Integration of the brachiopod data from western Newfoundland with those from the type Whiterockian in Nevada, combined with the evidence of graptolites from both areas, indicates that the Orthidiella Zone spans the Australian Castlemainian, Yapeenian, and lower Darriwilian Dal zones.

scholarly journals Exchange Speed of Four-Component Nanorotors Correlates with Hammett Substituent Constants

Chemistry ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 116-125
Author(s):  
Yi-Fan Li ◽  
Amit Ghosh ◽  
Pronay Kumar Biswas ◽  
Suchismita Saha ◽  
Michael Schmittel
Keyword(s):  
Linear Correlation ◽  
Bond Cleavage ◽  
Head Group ◽  
Ligand Interaction ◽  
Exchange Frequency ◽  
Rate Determining Step ◽  
Head Groups ◽  
Substituent Constants ◽  
First Time ◽  
Determining Factor

Three distinct four-component supramolecular nanorotors were prepared, using, for the first time, bipyridine instead of phenanthroline stations in the stator. Following our established self-sorting protocol to multicomponent nanodevices, the nanorotors were self-assembled by mixing the stator, rotators with various pyridine head groups, copper(I) ions and 1,4-diazabicyclo[2.2.2]octane (DABCO). Whereas the exchange of a phenanthroline vs. a bipyridine station did not entail significant changes in the rotational exchange frequency, the para-substituents at the pyridine head group of the rotator had drastic consequences on the speed: 4-OMe (k298 = 35 kHz), 4-H (k298 = 77 kHz) and 4-NO2 (k298 = 843 kHz). The exchange frequency (log k) showed an excellent linear correlation with both the Hammett substituent constants and log K of the copper(I)–ligand interaction, proving that rotator–copper(I) bond cleavage is the key determining factor in the rate-determining step.

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.

An endemic brachiopod fauna from the Middle Ordovician of North Wales

1993 ◽  
Vol 28 (1) ◽  
pp. 21-36 ◽  
Author(s):  
D. A. T. Harper ◽  
P. J. Brenchley
Keyword(s):  
Middle Ordovician ◽  
North Wales ◽  
Brachiopod Fauna

Early/Middle Arenig (Late Floian) Radiolarian Faunal Assemblages from Cow Head Group, Western Newfoundland

2015 ◽  
Vol 304 (1-6) ◽  
pp. 1-63 ◽  
Author(s):  
Mun-Zu Won ◽  
William J. Iams
Keyword(s):  
Head Group ◽  
Faunal Assemblages

Ordovician paleomagnetic results from the St. George and Table Head carbonates of western Newfoundland

1987 ◽  
Vol 24 (9) ◽  
pp. 1785-1796 ◽  
Author(s):  
Ernst R. Deutsch ◽  
Jagat N. Prasad
Keyword(s):  
Thermal Treatment ◽  
Geomagnetic Field ◽  
Late Paleozoic ◽  
Middle Ordovician ◽  
Viscous Component ◽  
Head Groups ◽  
Anticlockwise Rotation

We have studied 85 limestone and dolostone samples from 21 sites of the St. George and Table Head groups (Lower and Middle Ordovician) on Port au Port Peninsula (Humber Zone). Their gentle (~15°) tilt is probably Devonian. A steep viscous component dominant in the natural remanence is removed by thermal and (less efficiently) alternating-field demagnetization. In about 60% of all samples, the thermal treatment yielded a southeasterly reverse component ("A"), which typically remained blocked to 450–500 °C and then decayed to noise. Mean A component directions calculated from Zijderveld plots and referred to bedding are D, I = 148.5°, +33.6 °for N = 9 St. George sites and D, I = 150.0°, I = +40.7 °for N = 5 Table Head sites. Corresponding antipoles are 17.5°N, 152.3°E, dp, dm = 2.8°, 4.9 °and 13.4°N, 149.2°E, dp, dm = 2.9°, 4.7°, respectively. We interpret these results as representative of the geomagnetic field in the Early and mid-Ordovician. In 14 samples, mainly from the older St. George strata, thermal treatment yielded a reverse ("B") component with mean direction D, I = 167.9°, −9.2°, corresponding to an antipole at 44.9°N, 138.2°E, dp, dm = 3.6°, 7.1°. We interpret this as a late Paleozoic overprint in diagenetic hematite. The 30° anticlockwise rotation of Newfoundland proposed by Wegener is not supported by our data.

scholarly journals Biosynthesis of Ether-Type Polar Lipids in Archaea and Evolutionary Considerations

2007 ◽  
Vol 71 (1) ◽  
pp. 97-120 ◽  
Author(s):  
Yosuke Koga ◽  
Hiroyuki Morii
Keyword(s):  
Mevalonate Pathway ◽  
Polar Lipids ◽  
In Vivo Studies ◽  
Head Group ◽  
Polar Head Group ◽  
Phospholipid Synthesis ◽  
Polar Head ◽  
Head Groups

SUMMARY This review deals with the in vitro biosynthesis of the characteristics of polar lipids in archaea along with preceding in vivo studies. Isoprenoid chains are synthesized through the classical mevalonate pathway, as in eucarya, with minor modifications in some archaeal species. Most enzymes involved in the pathway have been identified enzymatically and/or genomically. Three of the relevant enzymes are found in enzyme families different from the known enzymes. The order of reactions in the phospholipid synthesis pathway (glycerophosphate backbone formation, linking of glycerophosphate with two radyl chains, activation by CDP, and attachment of common polar head groups) is analogous to that of bacteria. sn-Glycerol-1-phosphate dehydrogenase is responsible for the formation of the sn-glycerol-1-phosphate backbone of phospholipids in all archaea. After the formation of two ether bonds, CDP-archaeol acts as a common precursor of various archaeal phospholipid syntheses. Various phospholipid-synthesizing enzymes from archaea and bacteria belong to the same large CDP-alcohol phosphatidyltransferase family. In short, the first halves of the phospholipid synthesis pathways play a role in synthesis of the characteristic structures of archaeal and bacterial phospholipids, respectively. In the second halves of the pathways, the polar head group-attaching reactions and enzymes are homologous in both domains. These are regarded as revealing the hybrid nature of phospholipid biosynthesis. Precells proposed by Wächtershäuser are differentiated into archaea and bacteria by spontaneous segregation of enantiomeric phospholipid membranes (with sn-glycerol-1-phosphate and sn-glycerol-3-phosphate backbones) and the fusion and fission of precells. Considering the nature of the phospholipid synthesis pathways, we here propose that common phospholipid polar head groups were present in precells before the differentiation into archaea and bacteria.

Reconstruction of a lower/middle ordovician carbonate shelfmargin: Cow Head Group, Western Newfoundland

Facies ◽  
1989 ◽  
Vol 21 (1) ◽  
pp. 189-261 ◽  
Author(s):  
Susanne M. L. Pohler ◽  
Noël P. James
Keyword(s):  
Head Group ◽  
Middle Ordovician
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