Peritidal origin of the Lower Ordovician Upton Group, southern Quebec Appalachians

1992 ◽  
Vol 29 (5) ◽  
pp. 1106-1118 ◽  
Author(s):  
Denis Lavoie
Keyword(s):  
Continental Margin ◽  
Lower Cambrian ◽  
Outer Shelf ◽  
Lower Ordovician ◽  
External Domain ◽  
Appalachian Orogen ◽  
Shallow Subtidal ◽  
Volcanic Succession ◽  
Mixed Carbonate

The Lower Ordovician Upton Group is part of the Cambrian–Ordovician external domain of the Appalachian Orogen of southern Quebec. It is a mixed carbonate–siliciclastic–volcanic succession occurring within flyschoid sediment of the Lower Cambrian Granby Nappe. The bulk of the Upton Group is a grey, massive, recrystallized limestone of probable peritidal and shallow subtidal origin. Associated siliciclastic lithofacies are typical of peritidal and outer-shelf settings. The proposed peritidal paleoenvironmental model differs from previous interpretations and indicates that it is unlikely that the Upton Group is a slab derived from the Ordovician continental margin which has slid into the Granby Nappe.

The stratigraphy of the Lower Ordovician St. George Group, western Newfoundland: the interaction between eustasy and tectonics

1987 ◽  
Vol 24 (10) ◽  
pp. 1927-1951 ◽  
Author(s):  
Ian Knight ◽  
Noel P. James
Keyword(s):  
Sea Level ◽  
Continental Margin ◽  
Carbonate Rock ◽  
Outer Edge ◽  
Low Latitude ◽  
Middle Ordovician ◽  
Lower Ordovician ◽  
Shallow Subtidal ◽  
Eustatic Fluctuations ◽  
Equal Thickness

The St. George Group is a ~500 m thick sequence of carbonate rock that accumulated during Early and early Middle Ordovician time in a series of shallow subtidal and peritidal environments near the outer edge of a low-latitude continental margin. Lithological variations, in the form of two megacycles, reflect deposition in response to eustatic fluctuations in sea level preceding and during the early stages of Taconic orogenesis.Strata are grouped into four formations of roughly equal thickness. The newly named basal Watts Bight Formation is a lower sequence of peritidal limestones and dolostones and an upper thicker, commonly dolomitized succession of burrowed carbonates distinguished by large digitate thrombolite mounds. The overlying Boat Harbour Formation (new) is a series of muddy, peritidal, shallowing-upward sequences of limestone and dolostone. A widespread subaerial disconformity near the top of the formation, reflecting eustaic sea-level fall and the end of the first megacycle, is marked by breccia, quartz-pebble conglomerate, paleokarst, and (or) extensive dolomitization and is succeeded by higher energy peritidal limestones called the Barbace Cove Member (new). The succeeding, thick, monotonous Catoche Formation (revised) is a succession of fossiliferous subtidal limestones with scattered thrombolite mounds whose upper part is locally affected by extensive, multigeneration dolomitization and Pb–Zn mineralization. The St. George Group is capped by the newly defined Aguathuna Formation, a stack of peritidal dolostones and minor limestones and shales deposited during a period of repeated exposure and synsedimentary faulting. An erosional disconformity, resulting from regional compressional tectonics and eustatic sea-level fall, locally marks the top of the St. George and the second megacycle.

Appalachian Orogen in Canada

1979 ◽  
Vol 16 (3) ◽  
pp. 792-807 ◽  
Author(s):  
Harold Williams
Keyword(s):  
Continental Margin ◽  
Eastern North America ◽  
Early Paleozoic ◽  
The West ◽  
Late Precambrian ◽  
Northwest Africa ◽  
Iapetus Ocean ◽  
History Of ◽  
Appalachian Orogen ◽  
Andean Type

The Appalachian Orogen is divided into five broad zones based on stratigraphic and structural contrasts between Cambrian–Ordovician and older rocks. From west to east, these are the Humber, Dunnage, Gander, Avalon, and Meguma Zones.The westerly three zones fit present models for the development of the orogen through the generation and destruction of a late Precambrian – Early Paleozoic Iapetus Ocean. Thus, the Humber Zone records the development and destruction on an Atlantic-type continental margin, i.e., the ancient continental margin of Eastern North America that lay to the west of Iapetus; the Dunnage Zone represents vestiges of Iapetus with island arc sequences and mélanges built upon oceanic crust; and the Gander Zone records the development and destruction of a continental margin, at least in places of Andean type, that lay to the east of Iapetus.The Precambrian development of the Avalon Zone relates either to rifting and the initiation of Iapetus or to subduction and a cycle that preceded the opening of Iapetus. During the Cambrian Period, the Avalon Zone was a stable platform or marine shelf.Cambrian–Ordovician rocks of the Meguma Zone represent either a remnant of the continental embankment of ancient Northwest Africa or the marine fill of a graben developed within the Avalon Zone.Silurian and younger rocks of the Appalachian Orogen are mixed marine and terrestrial deposits that are unrelated to the earlier Paleozoic zonation of the system. Silurian and later development of the orogen is viewed as the history of deposition and deformation in successor basins that formed across the already destroyed margins and oceanic tract of Iapetus.

The Developmental Biology of Brachiopods

2001 ◽  
Vol 7 ◽  
pp. 69-88
Author(s):  
Gary Freeman
Keyword(s):  
Developmental Biology ◽  
Life History ◽  
Fossil Record ◽  
Lower Cambrian ◽  
Comprehensive Treatment ◽  
Next Generation ◽  
Lower Paleozoic ◽  
Short Course ◽  
Invertebrate Paleontology ◽  
Lower Ordovician

The chapter on anatomy in the Treatise on Invertebrate Paleontology (Part H, Brachiopoda, revised) (Williams et al., 1997) is the most current and comprehensive treatment that we have of reproduction and development in these animals. My contribution to this short course is a commentary on and addendum to this review. The study of the developmental biology of extant brachiopods describes a large part of their life history and defines several of the parameters that have to be taken into account when thinking about how a given set of genes will make it to the next generation (Havenhand, 1995). Some extant brachiopod genera like Discinisca and Crania (Neocrania) belong to families that first appeared in the fossil record during the Lower Ordovician or, as in the case of Glottidia, to a superfamily that first appeared during the Lower Cambrian. Studies on the development of these extant animals provide a picture of what the development of their Lower Paleozoic ancestors might have been like.

scholarly journals Lithostratigraphic and allostratigraphic framework of the Cambrian–Ordovician Potsdam Group and correlations across Early Paleozoic southern Laurentia

2017 ◽  
Vol 54 (5) ◽  
pp. 550-585 ◽  
Author(s):  
David G. Lowe ◽  
R.W.C. Arnott ◽  
Godfrey S. Nowlan ◽  
A.D. McCracken
Keyword(s):  
Climate Change ◽  
Early Paleozoic ◽  
Middle Cambrian ◽  
Shallow Marine ◽  
Upper Cambrian ◽  
Subaerial Exposure ◽  
Marine Sedimentation ◽  
Lower Ordovician ◽  
Fluvial Sedimentation ◽  
Mixed Carbonate

The Potsdam Group is a Cambrian to Lower Ordovician siliciclastic unit that crops out along the southeastern margins of the Ottawa graben. From its base upward, the Potsdam consists of the Ausable, Hannawa Falls, and Keeseville formations. In addition, the Potsdam is subdivided into three allounits: allounit 1 comprises the Ausable and Hannawa Falls, and allounits 2 and 3, respectively, the lower and upper parts of the Keeseville. Allounit 1 records Early to Middle Cambrian syn-rift arkosic fluvial sedimentation (Ausable Formation) with interfingering mudstone, arkose, and dolostone of the marine Altona Member recording transgression of the easternmost part of the Ottawa graben. Rift sedimentation was followed by a Middle Cambrian climate change resulting in local quartzose aeolian sedimentation (Hannawa Falls Formation). Allounit 1 sedimentation termination coincided with latest(?) Middle Cambrian tectonic reactivation of parts of the Ottawa graben. Allounit 2 (lower Keeseville) records mainly Upper Cambrian quartzose fluvial sedimentation, with transgression of the northern Ottawa graben resulting in deposition of mixed carbonate–siliciclastic strata of the marine Rivière Aux Outardes Member. Sedimentation was then terminated by an earliest Ordovician regression and unconformity development. Allounit 3 (upper Keeseville) records diachronous transgression across the Ottawa graben that by the Arenigian culminated in mixed carbonate–siliciclastic, shallow marine sedimentation (Theresa Formation). The contact separating the Potsdam Group and Theresa Formation is conformable, except locally in parts of the northern Ottawa graben where the presence of localized islands and (or) coastal salients resulted in subaerial exposure and erosion of the uppermost Potsdam strata, and accordingly unconformity development.

Non-trilobite arthropods from the Silver Peak Range, Nevada

2003 ◽  
Vol 77 (4) ◽  
pp. 706-720 ◽  
Author(s):  
Ben Waggoner
Keyword(s):  
Great Basin ◽  
Lower Cambrian ◽  
Upper Cambrian ◽  
Extant Taxon ◽  
Lower Ordovician

Two non-trilobite arthropods are described from the Emigrant Formation (Lower Cambrian-Lower Ordovician) in the Silver Peak Range, Esmeralda County, Nevada. A Middle or Upper Cambrian “arachnomorph” arthropod with a phosphatic exoskeleton has been noted in previous faunal lists, but has not been previously described. This fossil is here named Quasimodaspis brentsae gen. et sp. nov. Q. brentsae belongs in the Aglaspidida, a close outgroup to the true chelicerates; this is the second report of an aglaspidid from the Great Basin. Esmeraldacaris richardsonae gen. et sp. nov. is a newly discovered arthropod from the lower Ordovician, from beds transitional between the Emigrant Formation and the overlying Palmetto Formation. It is a survivor of an early arthropod lineage that does not belong in any extant taxon, but which may also include the Ordovician Corcorania and the Cambrian Mollisonia.

Age et position des calcaires de Saint-Jean-de-la-Riviere dans le Cambrien des Moitiers d'Allonne (Manche)

1963 ◽  
Vol S7-V (5) ◽  
pp. 722-729
Author(s):  
Francis Dore
Keyword(s):  
Lower Cambrian ◽  
Early Precambrian ◽  
Red Sandstone ◽  
Type Section ◽  
Lower Ordovician ◽  
Sandy Shale ◽  
Sandstone Facies

Abstract The type section for the Saint-Jean-de-la-Riviere limestone outcrops on the Moitiers d'Allonne anticline in the Douits valley north of Carteret and east of Moitiers (France). The limestones are younger than the sandy shale of the Cap Carteret series and between Moitiers and Bosquet the sequence is overlain by shales and red sandstones separating it from the Armorican sandstones. The lower Cambrian of the area presents a complete sedimentary section ending with a red sandstone facies of a regressing sea. A significant hiatus is evident before lower Ordovician transgression and continued deposition. Hyolothides and sponges, believed to be Azoic (early Precambrian) and older than Archaeocyathidae and Bigotina, are found in calcareous sandstone nodules on the beach at Carteret.

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