Middle and Late Ordovician conodont faunas and biostratigraphy of graptolitic strata of the Road River Group, northern Yukon Territory

1987 ◽  
Vol 24 (4) ◽  
pp. 643-653 ◽  
Author(s):  
Alexander D. McCracken ◽  
Alfred C. Lenz
Keyword(s):  
Northwest Territories ◽  
Cold Water ◽  
Late Ordovician ◽  
Yukon Territory ◽  
Warm Water ◽  
Rare Occurrence ◽  
Carbonate Facies ◽  
The Road ◽  
Fine Grained ◽  
Blackstone River

Ordovician conodont faunas from the fine-grained clastic Road River Group in northern Yukon Territory contain a mixture of species from both warm- and cold-water regions. This group in southwestern Northwest Territories also has mixed faunas, whereas conodonts from the carbonate facies are more characteristic of the warm-water regions.Six conodont associations and biozones are identified from the Yukon. Some, such as the early Llanvirn "Cordylodus" horridus – Spinodus spinatus association, contain reworked elements. The Pygodus serra Zone (middle–late Llanvirn) is within the upper P. tentaculatus Zone and well below the G. euglyphus Zone. Genera include Ansella, Periodon, Protopanderodus, Pygodus, and Walliserodus.At Peel River, conodonts are within the P. pacificus Zone. The Blackstone River conodonts occur above the P. pacificus Zone and below the G. persculptus Zone (?) and include Oulodus rohneri, Plectodina florida, and Noixodontus. Amorphognathus ordovicicus, Gamachignathus ensifer, O. ulrichi, and Plectodina tenuis occur in both faunas. These represent Fauna 12, found in late Richmondian strata, rather than the Gamachian Fauna 13 and are assigned to the G. ensifer Zone; both occurrences of G. ensifer are biohorizons. The C.? extraordinarius and G. persculptus zones are not recognized at Peel and Rock rivers and Tetlit Creek.The Ozarkodina n. sp. A – Icriodella sp. B association occurs at Pat Lake between the G. persculptus Zone (?) and the underlying P. pacificus Zone. The Ozarkodina have a Silurian aspect but must be regarded as Ordovician.The Ordovician–Silurian boundary in the Road River Group of the Yukon is best defined using graptolites because of the rare occurrence of conodonts.

Description and correlation of Late Ordovician conodonts from the D. ornatus and P. pacificus graptolite zones, Road River Group, northern Yukon Territory

1987 ◽  
Vol 24 (7) ◽  
pp. 1450-1464 ◽  
Author(s):  
Alexander D. McCracken
Keyword(s):  
New Species ◽  
New Genus ◽  
Late Ordovician ◽  
Yukon Territory ◽  
Upper Ordovician ◽  
The Road ◽  
Anticosti Island ◽  
Blackstone River ◽  
A New Species

Upper Ordovician carbonate beds within clastic strata of the Road River Group, northern Yukon Territory, have yielded 403 conodont elements representing 25 species; 19 of these are illustrated. Genera present are Amorphognathus, Belodina, Besselodus, Drepanoistodus, Eocarniodus?, Gamachignathus, Icriodella, Noixodontus, Oulodus, Panderodus s.l., Paroistodus?, Plectodina, Protopanderodus, Pseudobelodina s.l., Scabbardella, Strachanognathus, and Walliserodus. The apparatus of new genus A new species A includes a symmetrical and bifurrowed rastrate element.Sparse conodont faunas from Rock River occur in strata below a level bearing graptolites of the D. ornatus Zone and between this zone and the succeeding P. pacificus Zone. These conodonts have a range of "Trentonian" –Gamachian (upper Caradoc –Hirnantian).The fauna from Blackstone River is from a single bed that is 3 m below the G. persculptus Zone? and 13.7 m above the P. pacificus Zone. Although stratigraphically closer to the former, this fauna may be equivalent to a level within the P. pacificus Zone; the conodonts suggest correlation with the late Richmondian Fauna 12 and the lower G. ensifer Zone of Anticosti Island, Quebec. A similar fauna (G. ensifer Zone) occurs in one horizon within the P. pacificus Zone at upper Peel River. One metre above this is the informal D. cf. D. mirus graptolite biohorizon (P. pacificus Zone).The Blackstone and Peel faunas equate to a level within the Ordovician Anceps bands C and D of the Ordovician–Silurian boundary stratotype at Dob's Linn, Scotland. The interval of Fauna 13 and the Gamachian Stage may correspond to Anceps Band E and the C.? extraordinarius Band (and contiguous strata) at Dob's Linn. The base of the G. ensifer Zone and the higher base of the Gamachian are probably late Rawtheyan.

The sequence and correlation of Early Ordovician (Arenig) graptolite faunas in the Richardson Trough and Misty Creek Embayment, Yukon Territory and District of Mackenzie, Canada

2006 ◽  
Vol 43 (12) ◽  
pp. 1791-1820 ◽  
Author(s):  
D E Jackson ◽  
A C Lenz
Keyword(s):  
Northwest Territories ◽  
Deep Water ◽  
Yukon Territory ◽  
Early Ordovician ◽  
The Road ◽  
Bedded Chert ◽  
First Occurrence ◽  
Mackenzie Mountains ◽  
First Time

Four graptolite biozones are recorded from the Arenig portion of the Road River Group in the Richardson and Mackenzie mountains in the Yukon and Northwest Territories. In ascending order, these zones are Tetragraptus approximatus, Pendeograptus fruticosus, Didymograptus bifidus, and Parisograptus caduceus australis (new). The Castlemainian stage may be represented by nongraptolitic massive bedded chert. The Arenig–Llanvirn boundary is drawn below the first occurrence of Undulograptus austrodentatus. Fifty-four graptolite taxa are present, and 16 of these species and subspecies are recorded for the first time in this deep-water biotope, namely, Didymograptus? cf. adamantinus, D. asperus, D. dilatans, D. cf. kurcki, D. validus communis, Holmograptus aff. leptograptoides, H. sp. A, Isograptus? sp. nov. A, I. ? dilemma, Keblograptus geminus, Pseudisograptus manubriatus harrisi, Ps. m. koi, Ps. m. janus, Ps. cf. tau, Xiphograptus lofuensis, and Zygograptus cf. abnormis.

Stratiform sulfide and barite–fluorite mineralization of the Vulcan prospect, Northwest Territories: exhalation of basinal brines along a faulted continental margin

1984 ◽  
Vol 21 (1) ◽  
pp. 78-91 ◽  
Author(s):  
David A. Mako ◽  
Wayne C. Shanks III
Keyword(s):  
Northwest Territories ◽  
Hydrothermal Vents ◽  
Thickness Distribution ◽  
Massive Sulfide ◽  
Hydrothermal Activity ◽  
High Potassium ◽  
The Road ◽  
Fine Grained ◽  
Bottom Waters ◽  
Brine Pools

Laminated and massive sulfide (pyrite, sphalerite, galena) mineralization and massive barite – fluorite–galena lenses occur in Upper Silurian – Lower Devonian Road River Formation shales of the Vulcan property along the eastern flank of the Selwyn Basin, Northwest Territories, Canada. The 5 km thick stratigraphic section, ranging in age from Hadrynian through Mississippian, offers insight into the nature of the Mackenzie Platform – Selwyn Basin transition. Abrupt facies changes, synsedimentary faults, debris flows, local unconformities, and the presence of high-potassium mafic flows indicate extensional tectonics during deposition of the Road River Formation. Mineralization resulted from heated, metal-rich basinal brines that vented on the sea floor up normal faults.Sulfur-isotope studies indicate that both sulfate and sulfide were derived from the exhaling metalliferous brine. Sulfur-isotope data also suggest that reduction of sulfate in the brine occurred as a result of organic decomposition, possibly during thermal maturation of hydrocarbons at temperatures greater than 80 °C. Fluid inclusion observations indicate that the brine salinity reached 26 wt.% NaCl for at least a portion of the evolution of the hydrothermal system.Cooling of the brine during venting into bottom waters caused initial rapid precipitation of fine-grained barite, resulting in a baritic buildup above vent areas. Continued percolation of the brine through the baritic mound caused recrystallization of the barite and then the deposition of interstitial fluorite and galena. In other areas the dense ore fluid collected in topographic depressions, or brine pools, in which sulfide minerals accumulated under anoxic conditions. Location of hydrothermal vents, paleotopography, and intensity of hydrothermal activity were the main controls on the thickness, distribution, and grade of Vulcan mineralization.

Late Early Devonian Dacryoconarid Tentaculites, Northern Yukon Territory

1972 ◽  
Vol 9 (3) ◽  
pp. 297-318 ◽  
Author(s):  
Rolf Ludvigsen
Keyword(s):  
New Species ◽  
Environmental Factors ◽  
Yukon Territory ◽  
Early Devonian ◽  
The Road ◽  
Blackstone River

The late Early Devonian succession in northern Yukon Territory contains a well-preserved dacryoconarid tentaculite fauna dominated by Turkestanella acuaria (Richter) in the upper part of the Road River Formation and T. acuaria and Nowakia parabarrandei Churkin and Carter in the overlying Michelle Formation. Based on the dacryoconarid tentaculite fauna the bulk of the Michelle Formation in the Ogilvie to Hart Rivers area is dated as late Pragian (early Emsian), and based on the graptolite and dacryoconarid tentaculite fauna the uppermost Road River Formation in the Blackstone River area is dated as Pragian (early Emsian or late Siegenian or both). The appearance of species of Nowakia in northern Yukon considerably earlier than in Bohemia is documented. It is concluded that some genera of the Dacryoconarida were influenced in their occurrence by environmental factors. New species described are Turkestanella minuta, Viriatellina michellensis, Guerichina lenini, Styliolina blackstonensis, and Metastyliolina conica.

A new dasycladacean alga associated with the 'Arctic Ordovician' fauna on Cornwallis Island

1977 ◽  
Vol 55 (1) ◽  
pp. 52-60 ◽  
Author(s):  
D. G. Lee ◽  
W. G. E. Caldwell
Keyword(s):  
New Species ◽  
Northwest Territories ◽  
Late Ordovician ◽  
The Arctic ◽  
Carbonate Sediment ◽  
Tropical Waters ◽  
Fine Grained ◽  
Early Late ◽  
A New Species ◽  
Cornwallis Island

A new species of dasycladacean alga is present in the upper Thumb Mountain and in the overlying Irene Bay Formations of the Cornwallis Group on Cornwallis Island, Northwest Territories. The alga is associated with the 'Arctic Ordovician' fauna, which is of considerable biogeographical and biostratigraphical importance. This fauna is believed to be of early Late Ordovician (Caradocian) age.The new alga is a member of the cyclocrinitid tribe and clearly is to be referred to the genus Cyclocrinites. It is distinguished from all other cyclocrinitid species by the exceptionally small size, the unusual bilobate form, and the mode of calcification of its thallus. It is believed to have lived in tropical waters which were quiet and shallow, to have been anchored to the seabed by means of rhizoids. and to have grown only in areas in which fine-grained carbonate sediment was accumulating.

Frost mounds at Bear Rock, near Fort Norman, Northwest Territories, 1975–1976

1978 ◽  
Vol 15 (2) ◽  
pp. 263-276 ◽  
Author(s):  
Robert O. van Everdingen
Keyword(s):  
Northwest Territories ◽  
Soil Cover ◽  
Yukon Territory ◽  
East Side ◽  
Frozen Ground ◽  
North Fork ◽  
Spring Area ◽  
Empty Cavity ◽  
Blackstone River ◽  
Large Flow

A number of frost mounds of the frost blister type were observed at the site of a group of cold springs on the east side of Bear Rock, about 4 km west-northwest of Fort Norman, Northwest Territories, Canada. The mounds ranged in height from 2.0 to 3.0 m, with horizontal dimensions between 26 and 48 m. They contained a domed layer of ice, up to 85 cm thick, over an empty cavity up to 70 cm high, which was in turn underlain by frozen ground. Soil cover over the ice layer was 30–65 cm thick. The ice presumably formed from springwater injected under considerable hydraulic potential. New frost blisters are formed annually. Three recent frost blisters observed in June 1975 were partially destroyed by melting, slumping of the soil cover, and collapse of the ice dome by mid-September 1975. A portion of the ice lasted into summer 1976. Three new frost blisters, formed during the 1975–1976 winter, were observed in March 1976; two of these had completely collapsed by mid-June. An icing blister associated with one of them ruptured on March 21, 1976, producing a large flow of water, which lasted for several hours. A section of the icing blister subsequently subsided. Remnants of frost blisters have been observed in a spring area northeast of Turton Lake, Northwest Territories, and along the Dempster Highway in North Fork Pass and near the crossing of Blackstone River, Yukon Territory.

Predicting cold-water bleaching in corals: role of temperature, and potential integration of light exposure

2020 ◽  
Vol 642 ◽  
pp. 133-146
Author(s):  
PC González-Espinosa ◽  
SD Donner
Keyword(s):  
Coral Bleaching ◽  
Cold Water ◽  
Light Exposure ◽  
Light Attenuation ◽  
Florida Keys ◽  
Cold Temperature ◽  
Warm Water ◽  
Coral Tissue ◽  
Effect Of Temperature ◽  
Type I

Warm-water growth and survival of corals are constrained by a set of environmental conditions such as temperature, light, nutrient levels and salinity. Water temperatures of 1 to 2°C above the usual summer maximum can trigger a phenomenon known as coral bleaching, whereby disruption of the symbiosis between coral and dinoflagellate micro-algae, living within the coral tissue, reveals the white skeleton of coral. Anomalously cold water can also lead to coral bleaching but has been the subject of limited research. Although cold-water bleaching events are less common, they can produce similar impacts on coral reefs as warm-water events. In this study, we explored the effect of temperature and light on the likelihood of cold-water coral bleaching from 1998-2017 using available bleaching observations from the Eastern Tropical Pacific and the Florida Keys. Using satellite-derived sea surface temperature, photosynthetically available radiation and light attenuation data, cold temperature and light exposure metrics were developed and then tested against the bleaching observations using logistic regression. The results show that cold-water bleaching can be best predicted with an accumulated cold-temperature metric, i.e. ‘degree cooling weeks’, analogous to the heat stress metric ‘degree heating weeks’, with high accuracy (90%) and fewer Type I and Type II errors in comparison with other models. Although light, when also considered, improved prediction accuracy, we found that the most reliable framework for cold-water bleaching prediction may be based solely on cold-temperature exposure.

Different Ways of Hydrogen Bonding in Water - Why Does Warm Water Freeze Faster than Cold Water?

2016 ◽  
Vol 13 (1) ◽  
pp. 55-76 ◽  
Author(s):  
Yunwen Tao ◽  
Wenli Zou ◽  
Junteng Jia ◽  
Wei Li ◽  
Dieter Cremer
Keyword(s):  
Hydrogen Bonding ◽  
Cold Water ◽  
Warm Water
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