A revised lithostratigraphy of the Lower–Middle Ordovician Beekmantown Group, St. Lawrence Lowlands, Quebec and Ontario

1992 ◽  
Vol 29 (12) ◽  
pp. 2677-2694 ◽  
Author(s):  
Lawrence Bernstein
Keyword(s):  
Continental Margin ◽  
Carbonate Platform ◽  
Trace Fossils ◽  
Coarse Grained ◽  
Middle Ordovician ◽  
Fine Grained ◽  
Quartz Arenite ◽  
Taconic Orogeny ◽  
Reference Section

The Lower – lower Middle Ordovician Beekmantown Group of the St. Lawrence Lowlands is a variably thick pertitidal succession of dolostone, limestone, quartzose carbonate, and subordinate siltstone and shale that is gradationally bound by the Potsdam Group below and unconformably to conformably by the Chazy Group above. It is here considered to include three regionally extensive formations, a basal Theresa, a middle Beauharnois, and an upper, redefined Carillon. A principal reference section is established in the subsurface. The Theresa Formation is a transgressive succession, above Potsdam Group siliciclastics and below Beauharnois Formation carbonates. It is dominated by quartz arenite and quartzose dolostone; skeletal fossils are rare (usually gastropods), whereas trace fossils are abundant. The Beauharnois Formation is divided into two members, a basal Ogdensburg and an upper Huntingdon. The Ogdensburg Member is sandy, especially in its lower part, and relatively more fossiliferous than the Huntingdon Member. Both members include fossiliferous and nonfossiliferous, stromatolitic and oolitic, coarse-grained dolostone and subordinate limestone and reflect the development of a relatively wide peritidal carbonate platform. The Carillon Formation is a widespread unit that marks the onset of Middle Ordovician Taconic orogeny at the continental margin. It consists mostly of cyclic packages of laminated and burrowed, fine-grained dolostone and limestone, and as well siltstone and shale. Thin fossiliferous beds are dispersed in its upper part.

Middle Ordovician agglutinated foraminifera including Reophax from the Mifflin Formation, Platteville Group of Illinois

1986 ◽  
Vol 60 (2) ◽  
pp. 233-248 ◽  
Author(s):  
Raymond C. Gutschick
Keyword(s):  
Water Chemistry ◽  
Carbonate Platform ◽  
Rapid Development ◽  
Marine Transgression ◽  
Middle Ordovician ◽  
Fine Grained ◽  
Lithographic Limestone ◽  
Ash Layer ◽  
New Form ◽  
Agglutinated Foraminifera

Agglutinated siliceous foraminifera occur in the Middle Ordovician (Blackriveran) Mifflin Formation of the Platteville Group in northern Illinois. The fauna consists of globular saccamminids and a new form Reophax blackriveranus n. sp. which records the oldest validated representative of this genus. This marks the earliest known occurrence of agglutinated foraminifera with multichambered uniserial tests of progressively expanding chambers from the proloculus to the aperture. This early innovation of test morphology was probably developed to control unfavorable changes in the water chemistry of the environment.Mifflin lithofacies consist of light gray, thin, wavy-bedded, lithographic limestone and fine-grained dolomite with green shale interbeds, thin calcarenite layers with graded bedding, a K-bentonite ash layer and hardground corrosion bedding surfaces. Mifflin biofacies include the foraminiferan fauna, brachiopods and molluscan shelly faunas, bryozoans, trilobites, ostracodes, echinoderms, solitary corals, conodonts, chitinozoans, scolecodonts, sponges and trace fossils particularly Chondrites.The Mifflin strata were deposited on an exceedingly gentle slope off the Pecatonica carbonate platform which flanked the Wisconsin Arch. Thin Mifflin clinothem limestone beds wedge out into shales in the moderately deep (<200 m) aerobic starved basin in eastern Iowa. This occurred in south tropical seas during a eustatic rise in sealevel and major marine transgression. Reophax is associated with saccamminids in the benthos of the marine upper foreslope. Apparently slope-dwelling Reophax foraminifera of the Ordovician were displaced downslope into the basin by the rapid development and expansion of hyperamminids which occupy the lower and middle foreslope in the Mississippian.

scholarly journals Hydrogeological dissimilarity of geodynamically different terranes

2021 ◽  
Vol 44 (2) ◽  
pp. 134-140
Author(s):  
V. E. Glotov
Keyword(s):  
Continental Margin ◽  
Sandy Loam ◽  
Active Continental Margin ◽  
Passive Continental Margin ◽  
Coarse Grained ◽  
Active Margin ◽  
Water Abundance ◽  
Fine Grained ◽  
Weathering Processes

The article presents and analyzes the data on ground waters of active (suprapermafrost) and hindered (subpermafrost) water exchange of geodynamically different terrains in order to prove the hydrogeological importance of their historical and tectonic characteristics. On the example of Trans-Polar Chukotka it is shown that, under suprapermafrost conditions, the ubiquitous eluvial-deluvial nappes are the most water-abundant on the terrane – a fragment of the passive continental margin, whereas they are the least water-abundant on the terrains of the active margin. Hydrogeological situation changes under subpermafrost conditions: more permeable and water-retaining rocks compose the terranes of the active margin. These differences are associated with the level of rock tectonic decompaction and, accordingly, with different intensity of weathering processes in the terrane rocks of different geodynamic origin in suprapermafrost and subpermafrost conditions. The hypergenesis zone on the terranes of the passive continental margin features coarse-grained rock weathering products accumulated in relatively calm geological and historical environments, the aggregate is sandy. The terranes of the active margin, which underwent long-term subvertical and subhorizontal displacements contain more fine-grained weathering products; the aggregate includes sandy loam and clay sand. Since the permafrost strata in both Trans-Polar Chukotka and Eastern Siberia is greater than the depth of hypergene transformations, the terranes of the active continental margin, the rocks of which were impacted by tectonic decompaction processes, mainly of a strike-slip and thrust nature, feature greater water abundance in subpermafrost conditions.

Allochthonous slope sequence at Lobster Cove Head: evidence for a complex Middle Ordovician platform margin in western Newfoundland

1987 ◽  
Vol 24 (6) ◽  
pp. 1199-1211 ◽  
Author(s):  
Noel P. James ◽  
Jack W. Botsford ◽  
S. Henry Williams
Keyword(s):  
Deep Water ◽  
Carbonate Platform ◽  
Head Group ◽  
Middle Ordovician ◽  
The North ◽  
Platform Margin ◽  
Taconic Orogeny ◽  
Group Contact ◽  
Carbonate Platform Margin ◽  
Shallow Bay

The upper part of an intact sequence of Lower to Middle Ordovician deep-water sediments, which now form a large, disrupted raft within the Rocky Harbour Mélange at Lobster Cove Head, is interpreted as having been deposited downslope from a drowned carbonate platform margin. The entire 50 m thick section is Arenig (late Canadian or Ibexian to early Whiterock) in age; graptolite biostratigraphy demonstrates a correlation with upper parts of the Cow Head Group to the north. The basal part of the section is a proximal facies of the Cow Head Group (Shallow Bay Formation, Factory Cove Member, Beds 9, 10, and part of Bed 11). The upper part of the section consists of interbedded dolostone and shale and is unlike any other sequence in the Cow Head Group. This upper sedimentary sequence is defined as the Lobster Cove Head Member of the Shallow Bay Formation, Cow Head Group. Contact between the two sedimentary packages is also marked by a faunal break and coincides with emplacement of megaconglomerate Bed 12 at Cow Head.This break marks the change from a uniform to complex carbonate platform margin configuration and is here interpreted as the result of synsedimentary faulting. The margin upslope from Cow Head remained in shallow water during the final stages of Cow Head Group deposition, whereas that upslope from Lobster Cove Head was drowned and shed little sediment into deep water. The synsedimentary faulting, which led to rapid subsidence and platform-margin drowning upslope from Lobster Cove Head and possibly the deposition of megaconglomerate Bed 12 at Cow Head, coincides with the onset of the Taconic Orogeny in western Newfoundland.

Petrology of alkali wehrlite sills in the Oman Mountains

1984 ◽  
Vol 48 (346) ◽  
pp. 13-20 ◽  
Author(s):  
S. J. Lippard
Keyword(s):  
Continental Margin ◽  
Tectonic Setting ◽  
Light Element ◽  
Parent Magma ◽  
Coarse Grained ◽  
Thrust Belt ◽  
Fine Grained ◽  
Oman Mountains ◽  
Incompatible Elements ◽  
Rich Liquid

AbstractAlkaline mafic sills of Jurassic to Cretaceous age in the Oman Mountains have coarse-grained wehrlite centres composed of olivine and zoned diopside-titanaugite with large interstitial poikilitic titanian hornblendes and titanian barian phlogopites and biotites which appear to have crystallized from a trapped, intergranular, volatile-rich liquid. The fine-grained chilled margins of the sills are olivine-poor and composed largely of titanaugite, kaersutite, sphene, and interstitial altered plagioclase. The rocks have high contents of incompatible elements (Ti, P, Sr, Ba, Zr, Nb, and others) and steeply inclined, light element enriched, REE patterns. The parent magma is estimated to have been a hydrous alkali picrite with c. 12% MgO from which the wehrlite formed by olivine accumulation. The unusual tectonic setting of the sills, in a Mesozoic continental margin sequence emplaced in an Alpine thrust belt, is noted.

scholarly journals Source and depositional processes of coarse-grained limestone event beds in Frasnian slope deposits (Kostomłoty-Mogiłki quarry, Holy Cross Mountains, Poland)

Geologos ◽  
2010 ◽  
Vol 16 (3) ◽  
pp. 153-168 ◽  
Author(s):  
Aleksandra Vierek
Keyword(s):  
Carbonate Platform ◽  
Transitional Zone ◽  
High Energy ◽  
Coarse Grained ◽  
Tectonic Activity ◽  
Fine Grained ◽  
Holy Cross Mountains ◽  
Depositional Processes ◽  
Platform Margin ◽  
Slope Deposits

Source and depositional processes of coarse-grained limestone event beds in Frasnian slope deposits (Kostomłoty-Mogiłki quarry, Holy Cross Mountains, Poland)The Kostomłoty-Mogiłki succession is situated in the Kostomłoty transitional zone between the shallow-water Kielce stromatoporoid-coral platform and the deeper Łysogóry basin. In the Kostomłoty-Mogiłki quarry, the upper part of the Szydłówek Beds and Kostomłoty Beds are exposed. The Middle-Upper Frasnian Kostomłoty Beds are composed of shales, micritic and nodular limestones with abundant intercalations of detrital limestones. The dark shales and the micritic and nodular limestones record background sedimentation. The interbedded laminated and detrital limestones reflect high-energy deposition (= event beds). These event beds comprise laminated calcisiltites, fine-grained calcarenites, coarse-grained grain-supported calcirudites fabrics, and matrix-supported calcirudites. The material of these event beds was supplied by both erosion of the carbonate-platform margin and cannibalistic erosion of penecontemporaneous detrital limestones building the slope of this platform. Storms and the tectonic activity were likely the main causes of erosion. Combined and gravity flows were the transporting mechanisms involved in the reworking and redeposition.

Paleogeography of Northwestern New Brunswick during the Llandovery: a Study of the Provenance of the Siegas Formation

1971 ◽  
Vol 8 (2) ◽  
pp. 196-203 ◽  
Author(s):  
Terence Hamilton-Smith
Keyword(s):  
New Brunswick ◽  
Volcanic Rocks ◽  
Source Area ◽  
Potassium Feldspar ◽  
Source Rocks ◽  
Middle Ordovician ◽  
Quartz Arenite ◽  
Taconic Orogeny ◽  
Continuous Sedimentation ◽  
Mafic Volcanism

The Siegas Formation of northwestern New Brunswick and northeastern Maine is composed mainly of sandstone and slate and has yielded fossils of early Llandovery age. It conformably overlies older rocks, indicating that there was continuous sedimentation in the Siegas area during the time of the Taconic orogeny. The formation consists of the three laterally equivalent facies, the lithic wacke, the quartz arenite, and the arkosic facies. Sandstones of the lithic wacke facies are made up mainly of mafic volcanic grains and their decomposition products: sodic plagioclase, angular quartz, and pyroxene. Sandstones of the quartz arenite facies consist mainly of medium-grained rounded quartz. Sandstones of the arkosic facies are composed mainly of potassium feldspar, quartz, and felsic plutonic fragments. The source rocks of the Siegas Formation included mafic volcanic rocks (probably andesite), felsic plutonic rocks (possibly granitic), and quartzose sandstones.Facies, paleocurrents, and regional paleogeographic evidence indicate that the source area of the Siegas Formation was in northwestern New Brunswick, a region now covered by Devonian sedimentary rocks. The source area was probably an isolated, relatively discrete uplift similar to others previously described in northeastern Maine. It probably consisted of Cambrian or Ordovician quartzose sandstones like those of the Quebec Group of the Temiscouata area, overlain by middle Ordovician andesites like those of northeastern Maine, and intruded by a "granitic" body like the Rockabema Quartz Diorite of the Weeksboro – Lunksoos Lake anticlinorium in eastern Maine. The site of active erosion of this uplift probably was shifted to the northwest in the late Llandovery, possibly accompanied by the development of local mafic volcanism.

Conodont fauna and biostratigraphy of the Outram, Skoki, and Owen Creek Formations (Lower to Middle Ordovician), Wilcox Pass, Alberta, Canada

2003 ◽  
Vol 77 (5) ◽  
pp. 958-976 ◽  
Author(s):  
Leanne J. Pyle ◽  
Christopher R. Barnes ◽  
Zailiang Ji
Keyword(s):  
New Species ◽  
National Park ◽  
New Genus ◽  
Carbonate Platform ◽  
Canadian Cordillera ◽  
Middle Ordovician ◽  
Conodont Fauna ◽  
One New Species ◽  
A New Species ◽  
Reference Section

A collection of 60,886 conodonts was recovered from 141 samples of the Outram, Skoki and Owen Creek Formations (Lower to Middle Ordovician) that outcrop through the Wilcox Pass section, Jasper National Park, Alberta, Canada. This section representσ the standard reference section for the Lower-Middle Ordovician of the Southern Canadian Cordillera. The well preserved fauna is assigned to 75 species representing 48 genera. The species are representative of both the Midcontinent and Atlantic faunal realms, but dominantly the former. Nine Midcontinent Realm zones are recognized in the upwards shallowing carbonate platform succession including the Scolopodus subrex, Acodus kechikaensis, Oepikodus communis, Jumudontus gananda, Tripodus laevis, Histiodella altifrons, Histiodella sinuosa, Histiodella holodentata, and Phragmodus “pre-flexuosus” zones. Zones recognized that are characteristic of the Atlantic Realm include Paroistodus proteus, Paracordylodus gracilis, Oepikodus evae, Paroistodus originalis, and Microzarkodina flabellum. A new genus, Filodontus, is proposed for elements assigned previously to the form genus “Scolopodus” filosus. A new species, Leptochirognathus wilcoxi, is described and one new species, left in open nomenclature, is assigned to Rossodus?.

Structural history of continental margin sediments beneath the Bay of Islands Ophiolite, Newfoundland

1985 ◽  
Vol 22 (11) ◽  
pp. 1618-1632 ◽  
Author(s):  
John W. F. Waldron
Keyword(s):  
Continental Margin ◽  
Shear Fracture ◽  
Axial Plane ◽  
Middle Ordovician ◽  
Crenulation Cleavage ◽  
Taconic Orogeny ◽  
History Of ◽  
Sediment Deformation ◽  
Extension Fracture ◽  
Extensional Structures

Deformed continental margin sediments of the Curling Group underlie the Bay of Islands Ophiolite in the Humber Arm allochthon of western Newfoundland. Within the allochthon, tectonic slices of sediments are separated by zones of mélange. The earliest structures in the slices are synsedimentary features produced by soft-sediment deformation on the continental slope or rise. Later, west-facing asymmetrical F1 folds without penetrative axial plane cleavage were probably produced during the emplacement of the allochthon in the Middle Ordovician Taconic Orogeny. Associated extensional structures include shear-fracture and extension-fracture boudins. Pervasive cataclastic shearing of shale and boudinage of competent beds produced mélange between slices. Shear surfaces and the original bed-parallel fissility of the shale both contribute to the anastomosing fabric of the mélange matrix.A subsequent folding event of probable Acadian age produced upright to moderately inclined F2 folds with axial-plane cleavage increasing in intensity eastwards across the allochthon. This event refolded the folds, thrust slices, and mélange zones produced during emplacement. Later, gentle cross folds, associated with sporadic development of crenulation cleavage, produced culminations and depressions on the F2 fold hinges.

Spatial variability of surface sediments on the eastern continental margin of Korea

2020 ◽  
Author(s):  
Inkwon Um
Keyword(s):  
Spatial Variability ◽  
Last Glacial Maximum ◽  
Continental Margin ◽  
Surface Sediments ◽  
Glacial Maximum ◽  
Outer Shelf ◽  
Coarse Grained ◽  
Type I ◽  
Last Glacial ◽  
Fine Grained

&lt;p&gt;Total 99 surface sediment samples were obtained from eastern continental margin of Korea from Uljin to Busan below water depth 500 m to investigate the spatial variability of surface sediments. Mean grain size (Mz) of surface sediments ranges from 1.74 to 9.70 &amp;#934; (mean of 6.19&amp;#177;2.28 &amp;#934;), fine-grained sediments were mainly deposited along the coastal line on the Korea Strait Shelf Mud (KSSM) and Hupo Basin, whereas, coarse-grained sediments were covered on the Hupo Bank and southern continental margin. TOC content of surface sediments ranges from 0.09 to 3.27% (mean of 1.36&amp;#177;0.83%) and spatial variation is similar with that of Mz. Spatial distribution patterns of Al (1.56~10.98 %), K (0.94~3.29%), Ti (0.04~0.37%), Ni (1.97~38.18 mg/kg), Co (1.28~14.31 mg/kg), Cs (0.78~10.47 mg/kg), and total REEs (39.11~173.80 mg/kg) were also similar with that of Mz (r &gt; 0.70). Generally, contents of geochemical element were lower in coarse-grained sediments on the Hupo Bank and southern continental margin and relatively higher in fine-grained sediments on the KSSM and Hupo Basin. On the contrary, Ba (126.58~476.35 mg/kg) showed opposite pattern, high Ba contents were observed in coarse-grained sediments on the Hupo Bank and southern continental margin while, lower contents showed in fine-grained sediments. Surface sediments of the eastern continental margin of Korea could be divided into four types based on characteristics of geochemical element: Type I sediments were obtained from on the Hupo Bank and outer shelf/shelf break of the southern continental margin and might be composed with relic sediments formed during the Miocene and/or Last Glacial Maximum. Type II sediments were obtained from outer shelf of the southern continental margin especially beside of the Korea Trough and believed to be coarse-grained sediments deposited during the glacial age derived through the Korean Trough. Type III sediments which covered on the KSSM were mostly composed with fine-grained sediments. KSSM was deposited during the Last Glacial Maximum and consist of mixtures of sediments discharged from Chinese rivers and Nakdong River. Type IV sediments were mostly covered on the Hupo Basin. Sediments on the Hupo Basin were deposited during the Quaternary but sediment provenance should be differ from KSSM and it might be originated from small streams near the Hupo Basin.&lt;/p&gt;

TRACKING DINOSAURS IN COARSE-GRAINED SEDIMENTS FROM THE UPPER TRIASSIC OF ARDÈCHE (SOUTHEASTERN FRANCE)

Palaios ◽  
2020 ◽  
Vol 35 (11) ◽  
pp. 447-460
Author(s):  
LEO SZEWCZYK ◽  
EMMANUELLE VENNIN ◽  
JEAN-DAVID MOREAU ◽  
GEORGES GAND ◽  
MICHEL VEROLET ◽  
...  
Keyword(s):  
Microbial Mats ◽  
High Energy ◽  
Upper Triassic ◽  
Coarse Grained ◽  
Channel Migration ◽  
Fine Grained ◽  
Exceptional Preservation ◽  
Track Formation ◽  
Quartz Arenite ◽  
Tracking Surface

ABSTRACT Coarse-grained sediments deposited in high-energy environments are usually considered unfavorable to the preservation of fossil tracks. Here we report dinosaur footprints showing good physical preservation, despite being found in coarse-grained sandstones of alluvial origin from the Upper Triassic of Ardèche, southeastern France. The ichnoassemblage, dominated by Grallator isp., raises questions about the processes leading to the formation and preservation of tracks in coarse-grained sediments. The track-bearing surface is a medium- to coarse-grained quartz arenite that is microconglomeratic locally. The tracking surface grain size ranges from 0.2 to 2 mm and numerous pebbles are present. It is overlain by a succession of thin, intercalated layers of claystones and siltstones, themselves covered by a mix of siltstones and coarse-grained sandstones. We interpret this succession as a progressive decrease in energy due to channel migration culminating in channel abandonment, and the establishment of a lower energy setting where the tracking surface formed. Sedimentological and taphonomic observations indicate that the trackmakers walked on fine-grained layers (clay, silt) in which true tracks formed. The passage of the animals along the tracking surface deformed the older coarse-grained sand layers and resulted in the formation of the transmitted undertracks. The fine-grained layer helped record the pedal anatomy of the trackmakers and contributed to protecting the transmitted undertracks from destruction. Overall, we suggest that the fossil footprints were preserved by abiotic processes only, the main factor being the lithological contrast between successive sedimentary layers. The exceptional preservation of those relatively high quality undertracks in coarse-grained deposits contrasts sharply with the prevailing models of true track formation involving fine-grained sediments and microbial mats present in low-energy environments. This mode of undertrack formation may have been relatively frequent elsewhere but potentially overlooked in previous studies.

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