Revision of the position of the Ordovician–Silurian boundary in southern Ontario: regional chronostratigraphic implications of δ13C chemostratigraphy of the Manitoulin Formation and associated strata

2011 ◽  
Vol 48 (11) ◽  
pp. 1447-1470 ◽  
Author(s):  
Stig M. Bergström ◽  
Mark Kleffner ◽  
Birger Schmitz ◽  
Bradley D. Cramer
Keyword(s):  
Middle Part ◽  
Adjacent Region ◽  
Geologic History ◽  
Southern Ontario ◽  
Georgian Bay ◽  
The North ◽  
Head Formation ◽  
Depositional Patterns ◽  
Baseline Values ◽  
Anticosti Island

δ13C values of 142 samples from the Manitoulin Formation and subjacent strata collected from 14 exposures and two drill-cores on Manitoulin Island, Bruce Peninsula, and the region south of Georgian Bay suggest that the Manitoulin Formation is latest Ordovician (Hirnantian) rather than earliest Silurian in age. A δ13C excursion identified as the Hirnantian isotope carbon excursion (HICE), which has a magnitude of nearly 2.5‰ above baseline values, is present in an interval from the upper Queenston Formation to the lower to middle part of the Manitoulin Formation in most of Bruce Peninsula and in the area south of Georgian Bay, whereas on Manitoulin Island the HICE appears to be absent. This indicates that a significant part of the Manitoulin Formation is older on the Bruce Peninsula and in its adjacent region than on Manitoulin Island. The chemostratigraphically based conclusions are consistent with biostratigraphic data from conodonts and brachiopods. The Hirnantian δ13C curve from Anticosti Island, Quebec is closely similar to those of southern Ontario. Traditionally, the Ordovician–Silurian boundary has been placed at the base of the Manitoulin Formation, but the new results suggest that it is more likely to be at, or near, the base of the overlying Cabot Head Formation. These new results have major implications for the interpretation of the geologic history and marine depositional patterns of the latest Ordovician of a large part of the North American Midcontinent.

Storm-deposited sandstones (tempestites) and related ichnofossils of the Late Ordovician Georgian Bay Formation, southern Ontario, Canada

1991 ◽  
Vol 28 (2) ◽  
pp. 266-282 ◽  
Author(s):  
Michael Kerr ◽  
Nicholas Eyles
Keyword(s):  
Foreland Basin ◽  
Detailed Examination ◽  
Middle Part ◽  
Late Ordovician ◽  
Southern Ontario ◽  
Georgian Bay ◽  
Fine Grained ◽  
Delta Plain ◽  
Niagara Escarpment ◽  
Taconic Orogeny

The Late Ordovician Geogian Bay Formation of southern Ontario, Canada, comprises up to 250 m of grey to blue–grey shales interbedded with highly fossiliferous calcareous sandstones. These strata were deposited in equatorial paleolatitudes after 448 Ma in a shallow foreland basin created by overthrusting along the eastern margin of North America (the Taconic orogeny). The Georgian Bay Formation comprises the middle part of an upward-shallowing progradational sequence from deep-water transgressive shales of the underlying Whitby Formation to muddy tidal-flat sequences of the overlying Queenston Formation. Exposures in brickyard and river cuts near Toronto, and northwards along a narrow outcrop belt along the foot of the Niagara Escarpment, show laterally extensive (100 m+), sharp-based sheets of sandstone up to 1 m thick, with gutter casts and washed-out (hypichnial) trace fossils (dominantly Planolites and Paleophycus) on their lower bedding surfaces. Detailed examination of sandstone beds in outcrop and in three boreholes that penetrate the formation shows that the beds are composed internally of a basal fossil hash layer overlain by flat, hummocky, and wave-rippled divisions. Bed tops show a variety of wave-ripple forms and are heavily bioturbated (dominantly Bifungites, Conostichus, Diplocraterion, Didymaulichnus, Teichichnus). Sandstone sheets are interpreted as storm deposits (tempestites) resulting from tropical storms (hurricanes) transporting fine-grained suspended sediment from a delta plain onto a muddy shelf to the west.

Preliminary results of the study on the reasons of the Hai Hau erosion phenomenon

2007 ◽  
Vol 29 (3) ◽  
pp. 415-426
Author(s):  
Pham Van Ninh ◽  
Phan Ngoc Vinh ◽  
Nguyen Manh Hung ◽  
Dinh Van Manh
Keyword(s):  
Mathematical Modeling ◽  
Historical Data ◽  
Middle Part ◽  
Red River ◽  
Erosion Process ◽  
Red River Delta ◽  
The North ◽  
Severe Erosion ◽  
North And South ◽  
Very High

Overall the evolution process of the Red River Delta based on the maps and historical data resulted in a fact that before the 20th century all the Nam Dinh coastline was attributed to accumulation. Then started the erosion process at Xuan Thuydistrict and from the period of 1935 - 1965 the most severe erosion was contributed in the stretch from Ha Lan to Hai Trieu, 1965 - 1990 in Hai Chinh - Hai Hoa, 1990 - 2005 in the middle part of Hai Chinh - Hai Thinh (Hai Hau district). The adjoining stretches were suffered from not severe erosion. At the same time, the Ba Lat mouth is advanced to the sea and to the North and South direction by the time with a very high rate.The first task of the mathematical modeling of coastal line evolution of Hai Hau is to evaluate this important historical marked periods e. g. to model the coastal line at the periods before 1900, 1935 - 1965; 1965 - 1990; 1990 - 2005. The tasks is very complicated and time and working labors consuming.In the paper, the primarily results of the above mentioned simulations (as waves, currents, sediments transports and bottom - coastal lines evolution) has been shown. Based on the obtained results, there is a strong correlation between the protrusion magnitude and the southward moving of the erosion areas.

Preliminary detrital zircon U-Pb Geochronology of the Wasatch Formation, Powder River Basin, Wyoming

2019 ◽  
Vol 56 (3) ◽  
pp. 247-266
Author(s):  
Ian Anderson ◽  
David H. Malone ◽  
John Craddock
Keyword(s):  
River Basin ◽  
Detrital Zircon ◽  
Middle Part ◽  
Detrital Zircons ◽  
Powder River Basin ◽  
Zircon Age ◽  
Lower Eocene ◽  
The North ◽  
Mountain Front ◽  
Fluvial Sandstone

The lower Eocene Wasatch Formation is more than 1500 m thick in the Powder River Basin of Wyoming. The Wasatch is a Laramide synorgenic deposit that consists of paludal and lacustrine mudstone, fluvial sandstone, and coal. U-Pb geochronologic data on detrital zircons were gathered for a sandstone unit in the middle part of the succession. The Wasatch was collected along Interstate 90 just west of the Powder River, which is about 50 km east of the Bighorn Mountain front. The sandstone is lenticular in geometry and consists of arkosic arenite and wacke. The detrital zircon age spectrum ranged (n=99) from 1433-2957 Ma in age, and consisted of more than 95% Archean age grains, with an age peak of about 2900 Ma. Three populations of Archean ages are evident: 2886.6±10 Ma (24%), 2906.6±8.4 Ma (56%) and 2934.1±6.6 Ma (20%; all results 2 sigma). These ages are consistent with the age of Archean rocks exposed in the northern part of the range. The sparse Proterozoic grains were likely derived from the recycling of Cambrian and Carboniferous strata. These sands were transported to the Powder River Basin through the alluvial fans adjacent to the Piney Creek thrust. Drainage continued to the north through the basin and eventually into the Ancestral Missouri River and Gulf of Mexico. The provenance of the Wasatch is distinct from coeval Tatman and Willwood strata in the Bighorn and Absaroka basins, which were derived from distal source (>500 km) areas in the Sevier Highlands of Idaho and the Laramide Beartooth and Tobacco Root uplifts. Why the Bighorn Mountains shed abundant Eocene strata only to the east and not to the west remains enigmatic, and merits further study.

Chemical limnology of Georgian Bay and the North Channel between 1974 and 1980

Hydrobiologia ◽  
1988 ◽  
Vol 163 (1) ◽  
pp. 77-83 ◽  
Author(s):  
R. R. Weiler
Keyword(s):  
Georgian Bay ◽  
The North

Contemporary deformation and earthquake hazard of the Capital Circle of China inferred from GPS Measurements

2021 ◽  
Author(s):  
Shaogang Wei ◽  
Xiwei Xu ◽  
Tuo Shen ◽  
Xiaoqiong Lei
Keyword(s):  
High Risk ◽  
Earthquake Hazard ◽  
Historical Earthquakes ◽  
Tectonic Stress ◽  
Middle Part ◽  
Earthquake Hazards ◽  
Seismic Belt ◽  
Fault Plane Solutions ◽  
The North ◽  
Recent Earthquakes

<p>The Capital Circle (CC) is a region with high risk of great damaging earthquake hazards. In our present study, by using a subset of rigorously GPS data around the North China Plain (NCP), med-small recent earthquakes data and focal mechanism of high earthquakes data covering its surrounding regions, the following major conclusions have been reached: (a) Driven by the deformation force associated with both eastward and westward motion, with respect to the NCP, of the rigid South China and the rigid Amurian block, widespread sinistral shear appear over the NCP, which results in clusters of parallel NNE-trending faults with predominant right-lateral strike-slips via bookshelf faulting within the interior of the NCP. (b) Fault plane solutions of recent earthquakes show that tectonic stress field in the NCP demonstrate overwhelming NE-ENE direction of the maximum horizontal principal stress, and that almost all great historical earthquakes in the NCP occurred along the NWW-trending Zhangjiakou-Bohai seismic belt and the NNE-trending Tangshan-Hejian-Cixian seismic belt. Additionally, We propose a simple conceptual model for inter-seismic deformation associated with the Capital Circle, which might suggest that two seismic gaps are located on the middle part of Tangshan-Hejian-Cixian fault seismic belt (Tianjin-Hejian segment) and the northeast part of Tanlu seismic belt (Anqiu segment), and constitute as, in our opinion, high risk areas prone to great earthquakes.</p>

The benthic macro-algae of Georgian Bay, the North Channel and their drainage basin

1988 ◽  
pp. 141-148 ◽  
Author(s):  
Robert G. Sheath ◽  
Julie A. Hambrook ◽  
Christopher A. Nerone
Keyword(s):  
Drainage Basin ◽  
Georgian Bay ◽  
The North ◽  
Macro Algae

Great Lake Manitoulin: Georgian Bay and the North Channel

Hydrobiologia ◽  
1988 ◽  
Vol 163 (1) ◽  
pp. 1-19 ◽  
Author(s):  
P. G. Sly ◽  
M. Munawar
Keyword(s):  
Great Lake ◽  
Georgian Bay ◽  
The North

Middle Ordovician (Darriwilian) conodonts from southern Tibet, the Indian passive margin: implications for the age and correlation of the roof of the world

2020 ◽  
pp. 1-25
Author(s):  
Svend Stouge ◽  
David A. T. Harper ◽  
Renbin Zhan ◽  
Jianbo Liu ◽  
Lars Stemmerik
Keyword(s):  
Middle Part ◽  
Passive Margin ◽  
Continental Margins ◽  
Oceanic Circulation ◽  
Mount Everest ◽  
Southern Tibet ◽  
Middle Ordovician ◽  
The North ◽  
Carbon Isotope Excursion ◽  
Central Tibet

Abstract New occurrences of middle–late Darriwilian (Middle Ordovician) conodonts are reported from the Nyalam region, southern Tibet. The conodont-yielding strata, referred to the Chiatsun Group, accumulated on the north Indian continental margin of northern Gondwana. These Middle Ordovician conodonts include the informal species Histiodella sp. A in the middle part of the Lower Formation of the Chiatsun Group succeeded by a fauna of the Pygodus serra Zone in the upper part of that formation. Pygodus anserinus is recorded from the base of the Upper Formation of the Chiatsun Group. The Nyalam succession and its conodont taxa allow for precise correlation of the strata preserved on top of Mount Qomolangma (Mount Everest), eastern Tibet and the Peri-Gondwana Lhasa (north central Tibet), South China, North China, Tarim Basin and Thailand-Malaysia (Sibumasu Terrane) terranes and/or microcontinents. The middle Darriwilian positive increase in δ13Ccarb values (carbon isotope excursion, or MDICE) is recorded from most terranes, and can be related to a late middle Darriwilian global short-term cooling and sea-level drop. The cooling event prompted temperate- to warm-water taxa to migrate towards the palaeoequator and constrained the Australasian Province to locations near and at the palaeoequator. The intensified oceanic circulation and upwelling on continental margins probably caused some characteristic taxa to become extinct. The incoming fauna was mainly of cool-water taxa. The conodont specimens from southern Tibet are black to pale grey, corresponding to conodont colour index (CAI) values of 5 to 6, which demonstrates that the host sedimentary rocks were once heated to more than 360°C.

Sedimentology, Mineral Facies, and Petrofabric of the Meaford–Dundas Formation (Upper Ordovician) in Southern Ontario

1973 ◽  
Vol 10 (12) ◽  
pp. 1790-1804 ◽  
Author(s):  
K. Czurda ◽  
C. G. Winder ◽  
R. M. Quigley
Keyword(s):  
Clay Minerals ◽  
Heavy Minerals ◽  
Carbonate Content ◽  
The South ◽  
Upper Ordovician ◽  
Quartz Content ◽  
Southern Ontario ◽  
The North ◽  
Bedding Planes ◽  
Diffraction Patterns

The Meaford–Dundas Formation in southern Ontario is a medium gray shale with good fissility and resistant interbeds of gray fossiliferous limestones and siltstones. The hard layers are up to 20 cm in thickness and comprise 10 to 20% of the formation. The shale layers vary in thickness from 50 cm to 2 m.The clay minerals are principally illite, iron-chlorite, and small amounts of vermiculite and mixed-layer types. The carbonate content seems constant across the area at about 4 to 5% of the formation, except for the southwestern area where the carbonate increases to 20 or 25%. This increase is chiefly in dolomite content, a feature which reflects such factors as original conditions of deposition and possibly diagenesis subsequent to burial. The quartz content in the shale beds, and especially in the hard interbeds, increases towards the north to an average of 35 to 40% compared with 10 to 15% in the south. Framboids (aggregates of pyrite grains in spheroidal clusters) are a striking feature of the shale beds of the Meaford–Dundas Formation in the Meaford area.Fabric studies by means of X-ray diffraction patterns and scanning electron photomicrographs reveal, in most cases, high parallelism of clay platelets in the bedding planes, resulting in the good fissility of the shale.The principal source rock areas are the Appalachian orogen in the east (Taconic Mountains), which probably supplied most of the clay minerals and some quartz, and the Canadian Shield in the north, which provided the basin of sedimentation in the south with heavy minerals and additional quartz.

A stratigraphical and faunal revision of the Ordovician–Silurian strata of the Percé area, Quebec

1987 ◽  
Vol 24 (1) ◽  
pp. 117-134 ◽  
Author(s):  
Pierre J. Lespérance ◽  
Michel Malo ◽  
Peter M. Sheehan ◽  
W. B. Skidmore
Keyword(s):  
Local Development ◽  
Upper Ordovician ◽  
The North ◽  
Head Formation ◽  
Carbonate Sequence ◽  
Terrigenous Sequence

The Ordovician–Silurian strata of the Percé area are assigned to the Matapédia Group. They occur in a southwestern monoclinal sequence, unconformably overlying Cambrian strata, and are assigned to the Pabos and White Head formations. The Pabos Formation is preponderantly a terrigenous sequence, whereas the White Head is preponderantly a carbonate sequence. The Pabos strata of this area are included in the new Rouge Member, in which four brachiopod-dominated communities are recognized: the Dalmanella, Catazyga, Sowerbyella, and Epitomyonia communities, within which trilobites occur sporadically. The White Head Formation is divided into three new limestone members and a new mudstone member. The basal Burmingham Member has yielded a Catazyga Community and a Sowerbyella-like Community. The Côte de la Surprise Member is composed of mudstones with the previously described Hirnantia Community. The Rouge, Burmingham, and Côte de la Surprise members are Ashgillian (Upper Ordovician), but the uppermost two members of the White Head Formation, the L'Irlande and Des Jean members, are Llandoverian. They yield an Acernaspis Community, assigned a paleoecological position intermediate between those of the Clorinda and graptolite communities. The Matapédia Group limestones and shales in the structurally complex northeastern sequence are informally termed the Grande Coupe beds. These beds are partly or wholly time-correlative with the Rouge and Burmingham members but were deposited in deeper water. A Stenopareia Community includes the highly fossiliferous Grande Coupe beds, with a local development of the Foliomena Community. The Percé area is unique within the Quebec Appalachians because the strata of the Matapédia Group are highly fossiliferous, with distinct European affinities in the Ordovician, and because the monoclinal sequence is a deepening-upward sequence, probably to the north and west of deeper water clastics.

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