Upper Ordovician (Richmondian) cavity-dwelling (coelobiontic) organisms from southern Ontario

1980 ◽  
Vol 17 (12) ◽  
pp. 1616-1627 ◽  
Author(s):  
David R. Kobluk
Keyword(s):  
Lower Cambrian ◽  
Upper Ordovician ◽  
Southern Ontario ◽  
First Report ◽  
Middle Ordovician ◽  
Patch Reefs ◽  
Modern Reef

Upper Ordovician (Richmondian) patch reefs in exposures of the Meaford Formation (Streetsville Member) in Mullett Creek, Mississauga, Ontario contain a preserved coelobiontic (cavity-dwelling) biota. This is the first report of Upper Ordovician reef coelobionts.The cavity biota is dominated by algae that grew attached to the roof and walls of cavities. The fauna and flora consist of: (1) algae (including Girvanella, mammillary and laminated algae, micrite pendants, and a Renalcis-like alga); (2) calcareous vermiform tubes; (3) endolithic metazoa (Trypanites); (4) bryozoans; and (5) hemispherical worm tubes. In addition, thin micrite sheets, of possible organic origin, also line the roofs of some cavities.An infauna of burrowing worms, and coelobiontic sponges, which are common in Lower Cambrian and Middle Ordovician reef cavities, is absent from these Upper Ordovician cavities. In comparison, therefore, with older and also modern reef cavity biotas this Upper Ordovician coelobiontic biota is unusual.

Lower Cambrian cavity-dwelling endolithic (boring) sponges

1981 ◽  
Vol 18 (5) ◽  
pp. 972-980 ◽  
Author(s):  
David R. Kobluk
Keyword(s):  
Lower Cambrian ◽  
Middle Ordovician ◽  
Early Ordovician ◽  
Patch Reefs ◽  
Sponge Body ◽  
Boring Sponges

In the Lower Cambrian Forteau Formation (middle Bonnia–Olenellus zone) of southern Labrador, cavities in archaeocyath patch reefs contain preserved coelobiontic endolithic sponges. Scallops and carbonate chips produced by sponge boring, spicules, and preserved endolithic sponge body fossils all point to the presence of endolithic sponges in Lower Cambrian reef cavities.The oldest previously described endolithic sponges are Early Ordovician in age and the oldest previously known reef interior bioerosion is Middle Ordovician in age. The presence of endolithic sponges in reef cavities of the Forteau Formation therefore extends both the record of endolithic sponges and of reef interior bioerosion from the Ordovician to the upper Lower Cambrian.

Oxygen isotope (δ18O) trends measured from Ordovician conodont apatite using secondary ion mass spectrometry (SIMS): Implications for paleo-thermometry studies

2021 ◽  
Author(s):  
Cole T. Edwards ◽  
Clive M. Jones ◽  
Page C. Quinton ◽  
David A. Fike
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Matrix Effects ◽  
Analytical Techniques ◽  
Upper Ordovician ◽  
Bulk Analysis ◽  
Middle Ordovician ◽  
Ion Mass Spectrometry ◽  
Oxygen Isotopic ◽  
Secondary Ion

The oxygen isotopic compositions (δ18O) of minimally altered phosphate minerals and fossils, such as conodont elements, are used as a proxy for past ocean temperature. Phosphate is thermally stable under low to moderate burial conditions and is ideal for reconstructing seawater temperatures because the P-O bonds are highly resistant to isotopic exchange during diagenesis. Traditional bulk methods used to measure conodont δ18O include multiple conodont elements, which can reflect different environments and potentially yield an aggregate δ18O value derived from a mixture of different water masses. In situ spot analyses of individual elements using micro-analytical techniques, such as secondary ion mass spectrometry (SIMS), can address these issues. Here we present 108 new δ18O values using SIMS from conodont apatite collected from four Lower to Upper Ordovician stratigraphic successions from North America (Nevada, Oklahoma, and the Cincinnati Arch region of Kentucky and Indiana, USA). The available elements measured had a range of thermal alteration regimes that are categorized based on their conodont alteration index (CAI) as either low (CAI = 1−2) or high (CAI = 3−4). Though individual spot analyses of the same element yield δ18O values that vary by several per mil (‰), most form a normal distribution around a mean value. Isotopic variability of individual spots can be minimized by avoiding surficial heterogeneities like cracks, pits, or near the edge of the element and the precision can be improved with multiple (≥4) spot analyses of the same element. Mean δ18O values from multiple conodonts from the same bed range between 0.0 and 4.3‰ (median 1.0‰), regardless of low or high CAI values. Oxygen isotopic values measured using SIMS in this study reproduce values similar to published trends, namely, δ18O values increase during the Early−Middle Ordovician and plateau by the mid Darriwilian (late Middle Ordovician). Twenty-two of the measured conodonts were from ten sampled beds that had been previously measured using bulk analysis. SIMS-based δ18O values from these samples are more positive by an average of 1.7‰ compared to bulk values, consistent with observations by others who attribute the shift to carbonate- and hydroxyl-related SIMS matrix effects. This offset has implications for paleo-temperature model estimates, which indicate that a 4 °C temperature change corresponds to a 1‰ shift in δ18O (‰). Although this uncertainty precludes precise paleo-temperature reconstructions by SIMS, it is valuable for identifying spatial and stratigraphic trends in temperature that might not have been previously possible with bulk approaches.

Maturation thermique et histoire de l'enfouissement et de la génération des hydrocarbures du bassin de l'archipel de Mingan et de l'île d'Anticosti, Canada

1990 ◽  
Vol 27 (6) ◽  
pp. 731-741 ◽  
Author(s):  
Rudolf Bertrand
Keyword(s):  
Carbonate Platform ◽  
Burial History ◽  
Upper Ordovician ◽  
Southeastern Part ◽  
Middle Ordovician ◽  
Oil Generation ◽  
Wide Range ◽  
History Of ◽  
Anticosti Island ◽  
Depth Of Burial

Carbonate platform sequences of Anticosti Island and the Mingan Archipelago are Early Ordovician to Early Silurian in age. With the exception of the Macasty Formation, the sequences are impoverished in dispersed organic matter, which is chiefly composed of zooclasts. Zooclast reflectances suggest that the Upper Ordovician and Silurian sequences outcropping on Anticosti Island are entirely in the oil window but that the Lower to Middle Ordovician beds of the Mingan Archipelago and their stratigraphic equivalents in the subsurface of most of Anticosti Island belong to the condensate zone. Only the deeper sequences of the southwestern sector of Anticosti Island are in the diagenetic dry-gas zone. The maximum depth of burial of sequences below now-eroded Silurian to Devonian strata increases from 2.3 km on southwestern Anticosti Island to 4.5 km in the Mingan Archipelago. A late upwarp of the Precambrian basement likely allowed deeper erosion of the Paleozoic strata in the vicinity of the Mingan Archipelago than on Anticosti Island. Differential erosion resulted in a southwestern tilting of equal maturation surfaces. The Macasty Formation, the only source rock of the basin (total organic carbon generally > 3.5%, shows a wide range of thermal maturation levels (potential oil window to diagenetic dry gas). It can be inferred from the burial history of Anticosti Island sequences that oil generation began later but continued for a longer period of geologic time in the northeastern part than in the southeastern part of the island. Oil generation was entirely pre-Acadian in the southern and western parts of Anticosti Island, but pre- and post-Acadian in the northern and eastern parts.

Coral microatolls and a probable Middle Ordovician example

1990 ◽  
Vol 64 (1) ◽  
pp. 39-43 ◽  
Author(s):  
David R. Kobluk ◽  
Iqbal Noor
Keyword(s):  
Coral Reefs ◽  
Fossil Record ◽  
Scleractinian Coral ◽  
Regional Scale ◽  
Southern Ontario ◽  
Middle Ordovician ◽  
Reef Environments ◽  
Maximum Water ◽  
Water Depths ◽  
Tabulate Corals

A disk-shaped massive colony of Tetradium, from the Middle Ordovician Bobcaygeon Formation in southern Ontario, displays features of a coral microatoll. This is the first pre-Holocene coral microatoll yet described, indicating that some tabulate corals in level-bottom communities were growing as microatolls as do many modern colonial skeleton-secreting organisms.The microatoll therefore is not strictly a Quaternary or even Cenozoic phenomenon, but has a fossil record that may span most of the Phanerozoic. This indicates that the special conditions necessary for microatoll growth have existed outside of reef environments, and were present before the advent of scleractinian coral reefs. It may be possible to use ancient microatolls to estimate absolute water depths at low tide, thereby providing a means for estimating maximum water depths on a local and regional scale.

scholarly journals First report of sphaeronitid blastozoans (Echinodermata) in the Middle Ordovician of the Taurides, Turkey

2014 ◽  
Vol 23 ◽  
pp. 444-451 ◽  
Author(s):  
Elise NARDIN ◽  
Mehmet Cemal GÖNCÜOĞLU ◽  
Bertrand LEFEBVRE
Keyword(s):  
First Report ◽  
Middle Ordovician

Flexible crinoids from the Upper Ordovician Maquoketa Formation of the northern midcontinent and the evolution of early flexible crinoids

2001 ◽  
Vol 75 (2) ◽  
pp. 370-382 ◽  
Author(s):  
James C. Brower
Keyword(s):  
New Species ◽  
North America ◽  
Late Ordovician ◽  
Upper Ordovician ◽  
Middle Ordovician

Three flexible crinoids occur in the Upper Ordovician Maquoketa Formation of Illinois, Iowa, and Minnesota:Protaxocrinus girvanensisRamsbottom, 1961,Clidochirus anebosnew species, andProanisocrinus oswegoensis(Miller and Gurley, 1894).Protaxocrinus girvanensisis also found in the Upper Ordovician of Scotland which indicates that the ocean was narrow enough to allow at least one crinoid species to cross the barrier. The Upper Ordovician of North America and Scotland also share many common crinoid genera. Both phenetic and cladistic methods result in similar phylogenies of flexible crinoids.Protaxocrinuswas derived from a cupulocrinid ancestor during the Middle Ordovician.Clidochirusevolved fromProtaxocrinusor its ancestral stock prior to the Richmondian of the Late Ordovician. The RichmondianProanisocrinusand later anisocrinids are most closely related toClidochirusor its immediate predecessor. Thus, three major lineages of flexible crinoids,Protaxocrinus(taxocrinid group),Clidochirus(icthyocrinid), andProanisocrinus(anisocrinids and homalocrinids), appeared during the Ordovician. Despite their rarity during the Ordovician, all three flexible lineages survived the Latest Ordovician extinction, whereas their more abundant and successful cupulocrinid ancestors were eliminated.

Ordovician echinoderms from the Tabas and Damghan regions, Iran: palaeobiogeographical implications

2005 ◽  
Vol 176 (3) ◽  
pp. 231-242 ◽  
Author(s):  
Bertrand Lefebvre ◽  
Mansooreh Ghobadipour ◽  
Elise Nardin
Keyword(s):  
South China ◽  
Central Iran ◽  
East Central ◽  
First Report ◽  
Middle Ordovician ◽  
Alborz Range ◽  
First Time

Abstract Two echinoderm assemblages are described in the Middle Ordovician of Iran (Darriwilian). The Simeh Kuh section (Damghan area, eastern Alborz range) has yielded a rich and diverse blastozoan fauna consisting of fistuliporite (Echinosphaerites, Heliocrinites) and dichoporite rhombiferans (cheirocrinids indet., hemicosmitids indet.), as well as aristocystitid (Sinocystis) and sphaeronitid diploporites (Glyptosphaerites, Tholocystis). Heliocrinites, cheirocrinids, hemicosmitids, Glyptosphaerites, and Tholocystis are reported for the first time in the Ordovician of Iran. A less diverse assemblage was collected in the Shirgesht section (Tabas area, Derenjal Mountains), and represents the first report of Ordovician echinoderms in east-central Iran. The Shirgesht fauna includes fistuliporite rhombiferans (Heliocrinites), aristocystitid and sphaeronitid diploporites. The new Iranian material documents some of the earliest known assemblages of diploporites and rhombiferans, and thus, brings important information on the radiation of these two major blastozoan classes. The two Iranian echinoderm faunas show relatively strong affinities with contemporary faunas from Baltica, the northern Gondwanan margin (e.g. Bohemia, Morocco), Sibumasu, and South China terranes. Aristocystitids suggest stronger links between Iran, and regions from the “Province à Amphorides” (northern Gondwanan margin, Sibumasu, South China). These observations support a palaeogeographical position of Iran at intermediate palaeolatitudes during the early Middle Ordovician, in the periphery of the northeastern Gondwanan margin.

Revised stratigraphy of the middle Simcoe Group (Ordovician, upper Sandbian–Katian) in its type area: an integrated approach

2020 ◽  
Vol 57 (1) ◽  
pp. 184-198 ◽  
Author(s):  
Timothy R. Paton ◽  
Carlton E. Brett
Keyword(s):  
New York ◽  
Integrated Approach ◽  
Early 20Th Century ◽  
Upper Ordovician ◽  
Southern Ontario ◽  
Lower Member ◽  
Type Area ◽  
Central United States ◽  
The Status ◽  
Uppermost Portion

The Upper Ordovician Bobcaygeon Formation of southern Ontario is a widespread unit that spans the Sandbian–Katian stage boundary and contains exceptionally preserved invertebrate fossil assemblages, including the famed ‘Kirkfield echinoderm fauna.’ However, the precise correlation of this interval remains poorly understood. This paper presents new data on high-resolution sequence and carbon isotope chemostratigraphy of the Bobcaygeon interval based on new quarry exposures and introduces refined definitions of unit boundaries based on allostratigraphic criteria. Sequence, chemo-, and biostratigraphic evidence indicate that the Bobcaygeon Formation represents a composite unit as it encompasses a major erosional unconformity. The Coboconk and Kirkfield formations, described in the early 20th century, were merged into a single unit, the Bobcaygeon, out of concern that the original lithostratigraphic divisions would be conflated with biostratigraphic zones of the same names. However, these biostratigraphic zones are no longer favoured, and the lower member of the Bobcaygeon is here elevated again to the status of formation (Coboconk Formation) and represents the uppermost portion of the Sandbian M4 sequence. The middle and upper members of the Bobcaygeon, herein reassigned to the Kirkfield Formation, represent the upper Sandbian to lower Katian M5A and M5B sequences recognized widely in the eastern and central United States. The term Bobcaygeon is retained and elevated to the rank of subgroup. The Kirkfield Formation is divided into three members and contacts are refined, placing a 1–2 m transgressive grainstone at the base of each sequence. These units are correlated with equivalent strata of New York and the Cincinnati Arch.

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.

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