|Titre||The Great American Carbonate Bank in eastern Canada - A Synthesis|
|Auteur||Lavoie, D; Desrochers, A; Dix, G; Knight, I; Salad Hersi, O|
|Source||American Association of Petroleum Geologists, Annual Meeting Abstracts 2013, 2013 p. 1|
|Liens||Online - En ligne |
|Séries alt.||Secteur des sciences de la Terre, Contribution externe 20120257|
|Éditeur||American Association of Petroleum Geologists|
|Réunion||AAPG 2013 Annual Convention and Exhibition; Pittsburgh; US; mai 19-22, 2013|
|Document||publication en série|
|Province||Région extracotière de l'est|
|Programme||Bassins sédimentaires d'Hudson / Foxe Bay, GEM : La géocartographie de l'énergie et des minéraux|
|Résumé||(disponible en anglais seulement)|
The rifted margin of Laurentia in eastern Canada had a rugged morphology with major salients and recesses formed during the Ediacaran to late Early Cambrian
break-up of Rodinia. After short-lived carbonate production during the Early Cambrian, the Great American Carbonate Bank was firmly established in the earliest Middle Cambrian as the last rift-related event (Hawke Bay Event; late Early Cambrian) was
followed by passive thermal subsidence of eastern Laurentia.
Middle to Upper Cambrian carbonates are preserved in the Port au Port Group in Newfoundland (St. Lawrence Promontory). Late Middle to Upper Cambrian carbonates are found in southern and
eastern Québec (Québec Reentrant) although most of the preserved Upper Cambrian facies in the Reentrant consist of nearshore to fluvial clastics unconformably over the Grenvillian basement. The Cambrian carbonates are dominated by high-energy facies
with significant thrombolite reefs at the platform margin. The succession consists in large-scale transgressive-regressive cycles known as Cambrian Grand Cycles. The Cambrian¿Ordovician transition occurred at a time of a major sea level lowstand that
resulted in a major unconformity in southern Québec and Ontario. In Newfoundland, this sea level fall is recorded in the regressive facies of the last Cambrian Grand Cycle, but did not culminate in sub-aerial exposure.
The duration of the
depositional hiatus at the Cambrian¿Ordovician transition increases towards the west, from an early Skullrockian gap in the Philipsburg Thrust Slice in southeastern Québec, the hiatus covered entire Skullrockian in eastern Ontario. Major sea level
rise at or near the base of the Ordovician led to sedimentation on an extensive peritidal mud-dominated, low-energy carbonate platform. This platform is known as the St. George Group (Newfoundland), the Beekmantown Group (southwestern Québec and
Ontario), the School House Hill Group (southeastern Québec) and the Romaine Formation (Anticosti Island). Two 3rd order cycles are documented in Newfoundland. The presence of such cycles is also proposed further south, although their character still
has to be precise. Multiple 5th order, metre-scale peritidal dominated cycles have been documented.
A diachronous change in depositional style occurred along the margin of Laurentia near the base of the Middle Ordovician. Facies patterns became
controlled by faulting and accumulation rates increased significantly. These changes occurred first in late Ibexian in southeastern Québec and in early Whiterockian elsewhere. At most localities, this transition is also expressed in a significant
sub-aerial unconformity that is recognized along the entire paleosouthern margin of Laurentia. The west-directed migration of a tectonic peripheral bulge resulted in the final destruction of the Great American Carbonate Bank as sedimentation resumed
in tectonically active foreland basins.