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.

Early Paleozoic Hyolitha from North America: reexamination of Walcott's and Resser's type specimens

1988 ◽  
Vol 62 (2) ◽  
pp. 218-233 ◽  
Author(s):  
John Mark Malinky
Keyword(s):  
North America ◽  
Lower Cambrian ◽  
Type Species ◽  
New Genus ◽  
Early Paleozoic ◽  
Type Specimens ◽  
Middle Cambrian ◽  
Upper Cambrian ◽  
New Family ◽  
The Family

Concepts of the family Hyolithidae Nicholson fide Fisher and the genera Hyolithes Eichwald and Orthotheca Novak have been expanded through time to encompass a variety of morphologically dissimilar shells. The Hyolithidae is here considered to include only those hyolithid species which have a rounded (convex) dorsum; slopes on the dorsum are inflated, and the venter may be flat or slightly inflated. Hyolithes encompasses species which possess a low dorsum and a prominent longitudinal sulcus along each edge of the dorsum; the ligula is short and the apertural rim is flared. The emended concept of Orthotheca includes only those species of orthothecid hyoliths which have a subtriangular transverse outline and longitudinal lirae covering the shell on both dorsum and venter.Eighteen species of Hyolithes and one species of Orthotheca from the Appalachian region and Western Interior were reexamined in light of more modern taxonomic concepts and standards of quality for type material. Reexamination of type specimens of H. similis Walcott from the Lower Cambrian of Newfoundland, H. whitei Resser from the Lower Cambrian of Nevada, H. billingsi Walcott from the Lower Cambrian of Nevada, H. gallatinensis Resser from the Upper Cambrian of Wyoming, and H. partitus Resser from the Middle Cambrian of Alabama indicates that none of these species represents Hyolithes. Hyolithes similis is here included under the new genus Similotheca, in the new family Similothecidae. Hyolithes whitei is designated as the type species of the new genus Nevadotheca, to which H. billingsi may also belong. Hyolithes gallatinensis is referred to Burithes Missarzhevsky with question, and H. partitus may represent Joachimilites Marek. The type or types of H. attenuatus Walcott, H. cecrops Walcott, H. comptus Howell, H. cowanensis Resser, H. curticei Resser, H. idahoensis Resser, H. prolixus Resser, H. resseri Howell, H. shaleri Walcott, H. terranovicus Walcott, and H. wanneri Resser and Howell lack shells and/or other taxonomically important features such as a complete aperture, rendering the diagnoses of these species incomplete. Their names should only be used for the type specimens until better preserved topotypes become available for study. Morphology of the types of H.? corrugatus Walcott and “Orthotheca” sola Resser does not support placement in the Hyolitha; the affinities of these species are uncertain.

scholarly journals Dolomitization of the Lower Ordovician Aguathuna Formation carbonates, Port au Port Peninsula, western Newfoundland, Canada: implications for a hydrocarbon reservoir

2008 ◽  
Vol 45 (7) ◽  
pp. 795-813 ◽  
Author(s):  
Karem Azmy ◽  
Denis Lavoie ◽  
Ian Knight ◽  
Guoxiang Chi
Keyword(s):  
Crystal Size ◽  
Early Stage ◽  
Pore System ◽  
Shallow Marine ◽  
Molar Ratios ◽  
Hydrocarbon Reservoir ◽  
Subaerial Exposure ◽  
Lower Ordovician ◽  
Pee Dee ◽  
Marine Carbonates

The Lower Ordovician Aguathuna Formation (∼100 m thick) is formed of shallow-marine carbonates, which constitute the uppermost part of the St. George Group of western Newfoundland. Sedimentation was paused by a major subaerial exposure (St. George Unconformity), which likely developed a significant pore system in the underlying carbonates by meteoric dissolution. The sequence has been affected by multiphase dolomitization that caused complex changes in the rock porosity. The Aguathuna dolomites are classified into three main generations ranging in crystal size between ∼4 µm and 2 mm. The occurrence of fabric-retentive dolomicrites implies that dolomitization likely started during the early stages of diagenesis. Although dolomitization is pervasive in the upper part of the formation and significantly occludes the pores, some intervals in the lower part have higher porosity. The development of lower permeable layers overlain by an impermeable (seal) cap suggests a possible potential diagenetic trap. Unlike sabkha deposits, the Aguathuna carbonates do not have evaporite interlayers. Furthermore, the low Sr contents (∼96 ppm) and the δ18O values of earlier dolomites (–3.3‰ to –6.9‰ VPDB (Vienna Pee Dee Belemnite)) are also difficult to reconcile with a brine origin. The Sr/Ca molar ratios (0.0067–0.0009), calculated for the earliest dolomitizing fluid, suggest a modified seawater origin, likely mixed sea and meteoric waters. The least radiogenic 87Sr/86Sr values of the earliest dolomite are consistent with those of early Ordovician seawater, which supports an early-stage diagenesis. Petrography, geochemistry, and fluid inclusions of the late dolomites suggest precipitation at higher temperatures (∼73–95 °C) in deeper burial environments from hydrothermal solutions.

The Atlas-Meseta Red Beds basin (Morocco) and the Lower Ordovician rifting of NW-Gondwana

2016 ◽  
Vol 187 (3) ◽  
pp. 155-168 ◽  
Author(s):  
Hassan Ouanaimi ◽  
Abderrahmane Soulaimani ◽  
Christian Hoepffner ◽  
André Michard ◽  
Lahssen Baidder
Keyword(s):  
Debris Flows ◽  
The South ◽  
Red Beds ◽  
The West ◽  
Middle Cambrian ◽  
Shallow Marine ◽  
Marine Deposits ◽  
Magmatic Rocks ◽  
Lower Ordovician ◽  
Nw Gondwana

AbstractThe transition from the Cambrian to Ordovician in Morocco is known to be characterized by a frequent Furongian hiatus, restricted extension of the Tremadocian marine deposits, and frequent unconformities at the base of the transgressive upper Floian deposits. In the present work, we first highlight the occurrence of Fe- and mica-rich, red silty/sandy formations in the Central and Eastern High Atlas between the Middle Cambrian and Upper Floian sequences. In the Tislyt type-locality, a synsedimentary hemigraben structure is defined, within which the red beds show frequent slump folds, debris flows and internal unconformities. The correlation with several coeval series of the Meseta domain allows us to define a shallow marine, ferruginous clastic Atlas-Meseta Red Beds (AMRB) basin during the Tremadocian-early Floian. The AMRB basin extended between the Meseta coastal block and the Anti-Atlas domain, being limited by the fault zones that became the West Meseta shear zone and the South Meseta fault, respectively, in the Variscan orogen. The AMRB basin compares with the coeval rifted basins of the central Iberian and Armorican massifs. The red beds were likely sourced from the east, from both the Precambrian basement and Early Ordovician magmatic rocks, contrary to the Ordovician deposits of the Sahara platform sourced from the south. Subsidence of the AMRB and central Iberian-Armorican basins of the NW-Gondwana border aborted during the Floian, whereas the opening of the Rheic ocean went on more to the west.

Linguliform brachiopods from the terminal Cambrian and lowest Ordovician of the Oaxaquia microcontinent (Southern Mexico)

2011 ◽  
Vol 85 (1) ◽  
pp. 122-155 ◽  
Author(s):  
Michael Streng ◽  
Barbro B. Mellbin ◽  
Ed Landing ◽  
J. Duncan Keppie
Keyword(s):  
Marine Environment ◽  
Early Paleozoic ◽  
Southern Mexico ◽  
Upper Cambrian ◽  
Lower Ordovician ◽  
Emended Diagnosis

Eighteen taxa of linguliform brachiopods, mainly represented by acrotretoids, are reported from the Upper Cambrian (Furongian, Stage 10) and Lower Ordovician (Tremadocian) Tiñu Formation of Oaxaca State, Mexico. At the time of deposition, this area was part of Oaxaquia, which was either a microcontinent or an integral part of the Gondwanan margin. Whereas certain trilobites seem to indicate a Gondwanan affinity, the Tiñu brachiopod faunas show a less definite paleogeographic relationship. Some taxa have previously only been reported from Laurentia (Eurytreta cf. fillmorensis, Eurytreta cf. campaniformis), and one taxon is best known from the Avalon microcontinent (Eurytreta cf. sabrinae). However, the relatively high percentage of new and potentially endemic taxa (Oaxaquiatreta labrifera n. gen. n. sp., Tapuritreta reclinata n. sp., Oaxaquiatreta sp., Eurytreta? n. sp., Acrotretidae n. gen. n. sp., Obolinae gen. and sp. indet.) and the lack of other typical Laurentian, Gondwanan, or Avalonian taxa suggest either a certain degree of insularity of Oaxaquia or reflects a more temperate, unrestricted marine environment during the Early Paleozoic. Other taxa reported from the Tiñu Formation include Semitreta sp., Lingulella? spp., Obolinae gen. and sp. indet., Eoscaphelasma? sp., Ottenbyella? sp. A and sp. B, and Acrotretidae gen. and sp. indet. A, B, and C. Eurytreta and Semitreta are critically reviewed and several taxa previously assigned to them have been excluded. An emended diagnosis for the genus Eurytreta is presented. The presence of delthyrium and notothyrium-like structures in the siphonotretid Oaxaquiatreta n. gen. further strengthens the previously proposed relationship between the Siphonotretida and Paterinida.

Lithostratigraphy of the Cambrian – Lower Ordovician Saint John Group, southern New Brunswick

1988 ◽  
Vol 25 (5) ◽  
pp. 669-690 ◽  
Author(s):  
Saifullah K. Tanoli ◽  
Ron K. Pickerill
Keyword(s):  
New Brunswick ◽  
Black Shale ◽  
Lower Cambrian ◽  
Suspension Bridge ◽  
Stratigraphic Correlation ◽  
Middle Cambrian ◽  
Upper Cambrian ◽  
Early Ordovician ◽  
Lower Ordovician ◽  
Saint John

The Cambrian – Lower Ordovician Saint John Group of the Saint John area, southern New Brunswick, has historically been subdivided into 11 formations. The existing scheme is inappropriate, however, as many of the supposed formations, particularly those of Middle Cambrian–Early Ordovician age, were distinguished on a biostratigraphic rather than lithostratigraphic basis. We suggest the sequence can be more appropriately subdivided into seven formations, each of which can be clearly and easily identified by the field geologist. Lower Cambrian formations comprise, from base to top, the Ratcliffe Brook, Glen Falls, and Hanford Brook formations, all of which are retained from the previous nomenclature. Middle Cambrian strata comprise the Forest Hills Formation (to replace the Fossil Brook and Porter Road formations) and Upper Cambrian strata the King Square Formation (to replace the Hastings Cove and Agnostus Cove formations) and Silver Falls Formation (to replace the Black Shale Brook and Narrows formations). Lower Ordovician strata are referred to as the Reversing Falls Formation (to replace the Navy Island and Suspension Bridge formations). Descriptions of each formation are given, major sections of each are included, and stratigraphic correlation of the sequence in different geographic areas is demonstrated.

Provenance of the Meguma terrane, Nova Scotia: rifted margin of early Paleozoic Gondwana

2009 ◽  
Vol 46 (1) ◽  
pp. 1-8 ◽  
Author(s):  
John W.F. Waldron ◽  
Chris E. White ◽  
Sandra M. Barr ◽  
Antonio Simonetti ◽  
Larry M. Heaman
Keyword(s):  
Nova Scotia ◽  
Early Paleozoic ◽  
Middle Cambrian ◽  
Pan African ◽  
Lower Ordovician ◽  
Form Part ◽  
Meguma Terrane ◽  
Detrital Zircon Ages ◽  
Rifted Margin ◽  
Thermal Subsidence

Detrital zircon ages from the lower part of the Late Proterozoic(?) to Middle Cambrian Goldenville Group in the Meguma terrane of Nova Scotia suggest derivation from local sources in the Avalonian and Pan-African orogens on the margins of Early Cambrian Gondwana. Samples from near the top of the group show a broader distribution, including ages back to Archean. The εNd data show a corresponding trend, from slightly positive in the lower Goldenville Group to highly negative in the upper Goldenville Group and overlying Upper Cambrian to Lower Ordovician Halifax Group. The trends are consistent with deposition of the lower part of the Meguma succession in a rift, in which uplifted rift-flanks were the main source of the early basin fill, whereas subsequent thermal subsidence of rift margins allowed for more widespread sediment sourcing in younger units. The rift was possibly located between Gondwana and Avalonia, and may have been the locus for separation of Avalonia from Gondwana to form part of the Rheic Ocean.

The Middle–Upper Cambrian Transition in Southeastern Newfoundland, Canada

1975 ◽  
Vol 12 (12) ◽  
pp. 2065-2079 ◽  
Author(s):  
Valdemar Poulsen ◽  
Michael M. Anderson
Keyword(s):  
Basal Part ◽  
Eastern Canada ◽  
Middle Cambrian ◽  
Upper Cambrian ◽  
First Time

The Middle-Upper Cambrian transition in southeastern Newfoundland is shown to be very similar to the transition in Scandinavia and in the English Midlands. The late Middle Cambrian Lejopyge laevigata Zone, which is recorded for the first time from eastern Canada, is contained in the basal part of the Elliott Cove Formation and is conformably overlain by the Upper Cambrian Agnostus pisiformis Zone. The following trilobite species from the Lejopyge laevigata Zone at Manuels River and on Random Island are described: Andrarina costata (Angelin), Paradoxides sp., Lejopyge laevigata (Dalman), and Peronopsis insignis (Wallerius).

A new Late Cambrian pentastomid and a review of the relationships of this parasitic group

2005 ◽  
Vol 96 (2) ◽  
pp. 163-176 ◽  
Author(s):  
Dieter Waloszek ◽  
John E. Repetski ◽  
Andreas Maas
Keyword(s):  
Systematic Position ◽  
Host Group ◽  
Upper Cambrian ◽  
Late Cambrian ◽  
Lower Ordovician ◽  
Stem Lineage ◽  
New Form ◽  
Available Information ◽  
High Degree ◽  
Derivatives Of

ABSTRACTPentastomida, tongue worms, are a taxon of about 130 species of parasites, living exclusively in the respiratory tracts of vertebrates. Three-dimensionally preserved Upper Cambrian larvae already demonstrate a high degree of adaptation to parasitism, striking morphological conservatism, and a high diversification by the Late Cambrian, thereby suggesting a likewise diversified host group. Not least due to their highly modified morphology, the systematic affinities of pentastomids remain controversial. The two major alternatives place the group as either close to branchiuran crustaceans or as stem-lineage derivatives of the Euarthropoda. To this set of Cambrian fossil representatives of the pentastomids we can add a new form from Lower Ordovician boundary beds from Sweden, most likely reworked from Upper Cambrian horizons. Based on this new species, named Aengapentastomum andresi gen. et sp. nov., and the available information about fossil and Recent pentastomids, we review the diverging ideas on the systematic position of this fully parasitic taxon.

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