Ordovician intracratonic sediments from the Lac-St-Jean and Chicoutimi areas, Quebec, eastern Canada

Harland, T. L.; Pickerill, Ron K.; Fillion, D.

doi:10.1139/e85-021

Cited by 14 publications

(17 citation statements)

References 25 publications

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“…The Pointe-Bleue Shales (Desbiens and Lespérance 1989) are a calcareous mudstone located at the head of the Saguenay River (Fig. 2) that is a correlative to the lower flysch of the FRA (Harland et al 1985). However, it is conformably overlain by a coralbearing limestone (Île-aux-Couleuvres formation) rather than by coarser flysch or molasse deposits.…”

Section: Influence On the Distribution Of Ordovician Rocks In Adjacenmentioning

confidence: 99%

Lower Paleozoic configuration of the Quebec reentrant based on improved along-strike paleogeography

Cousineau¹,

Longuépée²

2003

Can. J. Earth Sci.

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An improved paleogeography of the Quebec reentrant has been achieved by examining the nature and distribution of major sediment buildups within this reentrant. The Quebec reentrant has one side produced by rift faults and one side by a major transform fault. The Oak Hill Group was deposited near a triple-rift zone. Clastic sediments of this group formed a large delta that was fed by a major river flowing in the rift valley of the Ottawa graben. The delta must have prograded on a gentle slope platform. No other thick deltaic deposits are known towards the northeast. Instead, facies analyses favor the existence of a promontory near Québec. Still farther to the northeast, the Saguenay graben was not the product of a triple-rift junction. However, it served to funnel sediments to a deep-sea fan, and the adjacent platform was narrow with a steep slope. The lateral distribution of sediments from the Ordovician Taconic orogeny can be explained by this improved paleogeographic reconstruction. The configuration of the Quebec reentrant required the arc to move into the reentrant. The Taconian tectonic wedge progressively accreted the thick sediment buildups that were the Oak Hill delta and the Bas-du-Fleuve deep-sea fan. This allowed them to act as new barriers to orogenic sediment dispersal as the orogeny proceeded.Résumé : La paléogéographie du rentrant de Québec a été améliorée par l'examen de la nature et la distribution d'accumulations majeures de sédiments dans ce rentrant. Un côté du rentrant de Québec a été formé par des failles d'effondrement et un autre côté a été formé par une faille transformante majeure. Le Groupe de Oak Hill a été déposé près d'une zone à effondrement triple. Les sédiments clastiques de ce groupe ont formé un large delta qui était nourri par une grande rivière s'écoulant dans la vallée d'effondrement du graben d'Ottawa. Le delta devait avancer sur une plate-forme à faible pente. Aucun autre dépôt deltaïque épais n'est connu vers le nord-est. Au lieu, les analyses de faciès favorisent l'existence d'un promontoire à proximité de la Ville de Québec. Situé encore plus vers le nord-est, le graben du Saguenay ne résulte pas d'une jonction d'effondrement triple. Toutefois, il servait à canaliser des sédiments vers un éventail marin profond et la plate-forme adjacente était étroite avec une pente abrupte. La distribution latérale des sédiments de l'orogenèse taconienne (Ordovicien) peut être expliquée par cette reconstruction paléogéographique améliorée. La configuration du rentrant de Québec exige que l'arc ait bougé pour se déplacer dans le rentrant. Le coin tectonique taconien a progressivement accrété les accumulations épaisses de sédiments qui formaient le delta de Oak Hill et l'éventail marin profond de Bas-du-Fleuve. Cela leur a permis d'agir comme de nouvelles barrières à la dispersion des sédiments orogéniques alors que l'orogenèse était en cours.[Traduit par la Rédaction] Cousineau and Longuépée 219

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Section: Influence On the Distribution Of Ordovician Rocks In Adjacenmentioning

confidence: 99%

Lower Paleozoic configuration of the Quebec reentrant based on improved along-strike paleogeography

Cousineau¹,

Longuépée²

2003

Can. J. Earth Sci.

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“…Although there are published reports of encrusting bryozoans and algae living occasionally on Tetradium (Walker 1972; Copper & Morrison 1978; Harland et al . 1985), there is no evidence from the upper Ottawa Valley of symbiotic encrusters or borers associated with Tetradium .…”

Section: Interspecific Interactionsmentioning

confidence: 99%

Biological affinity, phenotypic variation and palaeoecology ofTetradiumDana, 1846

Steele-Petrovich

2009

LET

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Comparisons of morphologies and modes of life of the Ordovician fossil Tetradium Dana, 1846, with chaetetid sponges, tabulate corals, and Recent rhodophytes show that several defining Tetradium characteristics are incompatible with its chaetetid and tabulate classifications. All Tetradium characteristics fit a rhodophyte identification, however, as a calcified uniaxial corticated florideophyte. It is argued from functional morphology that the fundamental subsquare cross‐section of the Tetradium tube is an adaptation for close packing, which implies that the basic growth form is compact and should have developed where conditions were optimal. More open forms are derived from it and probably occupied less‐favourable environments. Palaeoecological studies from the Ottawa Valley, Canada, show that the Tetradium growth form is correlated with environmental stress and became more open as salinity increased: i.e. the compact T. fibratum form lived in normal marine conditions, radiating bundles of T. cellulosum tubes in low to middle hypersalinity and single T. syringoporoides tubes in high hypersalinity. Different Tetradium growth forms from the study area are phenotypic variants of a single species, rather than different species and genera. Therefore, classifications that divide Tetradium into different species and genera based only on growth form have no biological basis. There is little evidence of interspecific interactions with Tetradium.

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“…For example, at nearby Chutes-aux-Galets (Fig. 2) very abundant Hallopora, Batostoma and others form interlocking 'mats' or clusters similar to those present in the Deschambault Formation in the St. Lawrence Lowland (Clark & Globensky 1973;Harland & Pickerill 1982;Harland et al 1985). In the St-Honor6 reef horizons there are two very distinct bryozoan assemblages.…”

Section: Reef Organismsmentioning

confidence: 99%

“…3). It seems that Tetradium preferred more restricted, lagoonal conditions (Walker 1972;Harland et al 1985). Each of these colonial corals grew as laterally extensive colonies spreading across the substrate and over the bryozoan stabilised lower parts of the reef.…”

Section: Reef Organismsmentioning

confidence: 99%

“…In low energy environments, low rates of deposition can lead to firming and hardening of all or parts of the sediment surface or the sediment just below the surface and, with removal of overlying sediment in the case of subsurface hardening, the formation of hardgrounds (Goldring & Kazmierczak 1974; Fursich 1979; Brett & Brookfield 1984). Such marine hardgrounds are very well-developed in the quarry sequence several metres below the reef horizon, where they are bored and/or have thick sulphide crusts (Harland et d. 1985). At the reef level such hardening appears to have been more incipient as all samples examined lacked convincing borings ( Fig.…”

Section: Reef Developmentmentioning

confidence: 99%

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Establishment and development of patch reefs in the intracratonic Ordovician sequence near Chicoutimi, Quebec

Harland

Pickerill

Fillion

1987

LET

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Patch reefs occur near the top of the transgressive sequence of Ordovician Trenton Group limestones in the Chicoutimi area of Quebec, eastern Canada. Despite their small sue, these reefs comprise diverse assemblages dominated by bryozoans, corals, stromatoporoids and receptaculitid algae. Pelmatozoans and gastropods are also conspicuous. The reefs were initiated and grew in a fully marine, open shelf setting. Available substrates varied from loose skeletal lenses to soft, firm or hardened bioturbated wackestones, and the earliest stages of reef growth reflect this heterogeneity. Loose or less firm substrates were colonised by bryozoans and pelmatozoans and/or by receptaculitids, which, together with accessory organisms, stabilised the sediments and provided the basis for further reef development. The resultant firmer, slightly elevated substrates provided sites for attachment of stromatoporoids and colonial corals which spread over earlier reef organisms and sediments and dominated the later stages of reef growth. On hardened areas of sediment, stromatoporoids and corals colonised the surface directly and the early stabilising stage of reef growth is absent. The compositions and developmental stages of these Trenton Group reefs are comparable with those seen in broadly contemporaneous and often larger reefs elsewhere, and are among the earliest in which corals played an important role.

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Ordovician intracratonic sediments from the Lac-St-Jean and Chicoutimi areas, Quebec, eastern Canada

Cited by 14 publications

References 25 publications

Lower Paleozoic configuration of the Quebec reentrant based on improved along-strike paleogeography

Lower Paleozoic configuration of the Quebec reentrant based on improved along-strike paleogeography

Biological affinity, phenotypic variation and palaeoecology ofTetradiumDana, 1846

Establishment and development of patch reefs in the intracratonic Ordovician sequence near Chicoutimi, Quebec

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