Stratigraphic framework for the Cambrian–Ordovician rift and passive margin successions from southern Quebec to western Newfoundland

2003 ◽  
Vol 40 (2) ◽  
pp. 177-205 ◽  
Author(s):  
Denis Lavoie ◽  
Elliott Burden ◽  
Daniel Lebel
Keyword(s):  
Sea Level ◽  
Continental Margin ◽  
Passive Margin ◽  
Early Cambrian ◽  
Sea Level Fluctuations ◽  
Late Cambrian ◽  
Head Groups ◽  
Stratigraphic Framework ◽  
Lower Ordovician ◽  
First Time

The Taconian Humber Zone stretches from western Newfoundland to southern Quebec. The Early Cambrian slope succession in Newfoundland is found in the Curling Group, whereas in Quebec, various units were deposited during that first time slice. Biostratigraphic data allow correlation of the Curling Group with the Labrador Group in Newfoundland and with the newly time-constrained slope succession in Quebec. The end of the rift–drift transition is marked by a sea-level lowstand at the end of the Early Cambrian. The Middle Cambrian to latest Early Ordovician passive margin history recorded five cyclic sea-level fluctuations. Three of these cycles are recorded in the shallow-marine Middle to Late Cambrian platform (Port au Port Group) and slope sediments preserved in the Cow Head and Northern Head groups in Newfoundland. The biostratigraphic information assists correlation with Cambrian passive margin units in Quebec. Major sea-level lowstands are recognized along the continental margin in early–middle Late Cambrian (Steptoan) and in late Late Cambrian (Sunwaptan). Even if the Quebec succession can be tied with its Newfoundland correlative, some significant differences in the nature of Upper Cambrian slope conglomerates argue for a tectonic control on the depth of erosion of the Cambrian continental margin. The Lower Ordovician record of the passive margin consists of two depositional cycles (Tremadocian–Arenigian) separated by a sea-level lowstand. This last event is well expressed in platform succession and is also recognized in conglomerate units found in the slope succession.

scholarly journals Impact of sea-level fluctuations on the sedimentation patterns of the SE African margin: implications for slope instability

2019 ◽  
Vol 500 (1) ◽  
pp. 267-276 ◽  
Author(s):  
Aaron Micallef ◽  
Aggeliki Georgiopoulou ◽  
Andrew Green ◽  
Vittorio Maselli
Keyword(s):  
South Africa ◽  
Sea Level ◽  
Coastal Region ◽  
Passive Margin ◽  
Slope Instability ◽  
Bottom Current ◽  
The South ◽  
Sea Level Fluctuations ◽  
International Ocean Discovery Program ◽  
Seismic Reflection Profiles

AbstractThe sheared-passive margin offshore Durban (South Africa) is characterized by a narrow continental shelf and steep slope hosting numerous submarine canyons. Supply of sediment to the margin is predominantly terrigenous, dominated by discharge from several short but fast-flowing rivers. International Ocean Discovery Program Expedition 361 provides a unique opportunity to investigate the role of sea-level fluctuations on the sedimentation patterns and slope instability along the South African margin. We analysed >300 sediment samples and downcore variations in P-wave, magnetic susceptibility, bioturbation intensity and bulk density from site U1474, as well as regional seismic reflection profiles to: (1) document an increase in sand input since the Mid-Pliocene; (2) associate this change to a drop in sea-level and extension of subaerial drainage systems towards the shelf-edge; (3) demonstrate that slope instability has played a key role in the evolution of the South Africa margin facing the Natal Valley. Furthermore, we highlight how the widespread occurrence of failure events reflects the tectonic control on the morphology of the shelf and slope, as well as bottom-current scour and instability of fan complexes. This information is important to improve hazard assessment in a populated coastal region with growing offshore hydrocarbon activities.

Neotectonic evolution of the Brazilian northeastern continental margin based on sedimentary facies and ichnology,

2014 ◽  
Vol 82 (2) ◽  
pp. 462-472 ◽  
Author(s):  
Rosana Gandini ◽  
Dilce de Fátima Rossetti ◽  
Renata Guimarães Netto ◽  
Francisco Hilário Rego Bezerra ◽  
Ana Maria Góes
Keyword(s):  
Sea Level ◽  
Continental Margin ◽  
Sedimentary Facies ◽  
Passive Margin ◽  
South American ◽  
Soft Sediment ◽  
Rift Basins ◽  
Deformation Structures ◽  
Last Glaciation ◽  
Sediment Deformation

AbstractQuaternary post-Barreiras sediments are widespread along Brazil's passive margin. These deposits are well exposed in the onshore Paraíba Basin, which is one of the rift basins formed during the Pangean continental breakup. In this area, the post-Barreiras sediments consist of sandstones with abundant soft-sediment deformation structures related to seismicity contemporaneous with deposition. The trace fossilsThalassinoidesandPsilonichnusare found up to 38 m above modern sea level in sandstones dated between 60.0 (± 1.4) and 15.1 (± 1.8) ka. The integration of ichnological and sedimentary facies suggests nearshore paleoenvironments. Such deposits could not be related to eustatic sea-level rise, as this time coincides with the last glaciation. Hence, an uplift of 0.63 mm/yr, or 1.97 mm/yr if sea level was 80 m lower in the last glaciation, would have been required to ascend the post-Barreiras sediments several meters above the present-day sea level during the last 60 ka. This would suggest that the post-rift stage of the South American eastern passive margin may have experienced tectonic reactivation more intense than generally recognized. Although more complete data are still needed, the information presented herein may play an important role in studies aiming to decipher the Quaternary evolution of this passive margin.

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.

Upper Proterozoic 'Limestone Unit', Northern Dogtooth Mountains, British Columbia

1973 ◽  
Vol 10 (2) ◽  
pp. 292-305 ◽  
Author(s):  
T. P. Poulton
Keyword(s):  
British Columbia ◽  
Sea Level ◽  
Continental Margin ◽  
Sea Level Fluctuations ◽  
Metasedimentary Rocks ◽  
Upper Proterozoic ◽  
Clastic Sediments ◽  
Carbonate Deposition ◽  
Stratigraphic Position

The Upper Proterozoic 'Limestone Unit' of the Horsethief Creek Group in the northern Dogtooth Mountains consists of deformed sedimentary and metasedimentary rocks with complex depositional and erosional relationships. They are interpreted to represent a westwardly prograding terrigenous and carbonate wedge in a continental margin situation. Shoaling resulted in differential carbonate deposition on top of a largely pelitic succession. Sea level fluctuations produced a complex unit characterized by alternating erosion and sedimentation, in different fades from east to west. This was succeeded by terrigenous clastic sediments with easterly or southeasterly provenance. The last recognizable events produced a widespread carbonate and sandstone blanket.A carbonate unit of similar stratigraphic position occurs in several locations north–northwest of the Dogtooth Mountains, approximately along a line paralleling the trend of Phanerozoic fades belts.

scholarly journals Depositional environment of the Branch Sandstone and correlative sequences: Late Cretaceous changes in relative sea level in the East Coast Basin of New Zealand

2021 ◽  
Author(s):  
◽  
Lisa McCarthy
Keyword(s):  
Sea Level ◽  
East Coast ◽  
Depositional Environments ◽  
Passive Margin ◽  
Sea Level Changes ◽  
Relative Sea Level ◽  
Sea Level Fluctuations ◽  
The North ◽  
Tasman Sea ◽  
History Of

<p>The Branch Sandstone is located within an overall transgressive, marine sedimentary succession in Marlborough, on the East Coast of New Zealand’s South Island. It has previously been interpreted as an anomalous sedimentary unit that was inferred to indicate abrupt and dramatic shallowing. The development of a presumed short-lived regressive deposit was thought to reflect a change in relative sea level, which had significant implications for the geological history of the Marlborough region, and regionally for the East Coast Basin.  The distribution and lithology of Branch Sandstone is described in detail from outcrop studies at Branch Stream, and through the compilation of existing regional data. Two approximately correlative sections from the East Coast of the North Island (Tangaruhe Stream and Angora Stream) are also examined to provide regional context. Depositional environments were interpreted using sedimentology and palynology, and age control was developed from dinoflagellate biostratigraphy. Data derived from these methods were combined with the work of previous authors to establish depositional models for each section which were then interpreted in the context of relative sea level fluctuations.  At Branch Stream, Branch Sandstone is interpreted as a shelfal marine sandstone, that disconformably overlies Herring Formation. The Branch Sandstone is interpreted as a more distal deposit than uppermost Herring Formation, whilst the disconformity is suggested to have developed during a fall in relative sea level. At Branch Stream, higher frequency tectonic or eustatic sea-level changes can therefore be distinguished within a passive margin sedimentary sequence, where sedimentation broadly reflects subsidence following rifting of the Tasman Sea. Development of a long-lived disconformity at Tangaruhe Stream and deposition of sediment gravity flow deposits at Angora Stream occurred at similar times to the fall in relative sea level documented at the top of the Herring Formation at Branch Stream. These features may reflect a basin-wide relative sea-level event, that coincides with global records of eustatic sea level fall.</p>

Late Cambrian conulariids from Wisconsin and Minnesota

2000 ◽  
Vol 74 (5) ◽  
pp. 828-838 ◽  
Author(s):  
Nigel C. Hughes ◽  
Gerald O. Gunderson ◽  
Michael J. Weedon
Keyword(s):  
Cross Sections ◽  
Lower Cambrian ◽  
New Genus ◽  
Mississippi Valley ◽  
Upper Cambrian ◽  
Late Cambrian ◽  
Lower Ordovician ◽  
Two New Species ◽  
First Time ◽  
Taxonomic Evaluation

Several localities within the heterolithic facies of the St. Lawrence Formation (Upper Cambrian) of Wisconsin and Minnesota yield specimens with phosphatic exoskeletons, quadrate cross sections composed of four equidimensional faces each bearing a midline, and possible holdfast attachment during life. These specimens are here referred to the order Conulariida, class Scyphozoa. Their fine, tuberculate surface ornament and serially invaginated midline structure serve to define a new genus, Baccaconularia, to which two new species, B. robinsoni and B. meyeri, are assigned. Conularia cambria Walcott 1890, also from the Cambrian of the northern Mississippi Valley and long dismissed as a misidentified trilobite fragment, is illustrated photographically for the first time. This species occurs in rocks stratigraphically beneath the St. Lawrence Formation. Specimens assigned to this species by Walcott are conulariids, but lack features now considered diagnostic of either Conularia or Baccaconularia. Walcott's material is insufficient to permit detailed taxonomic evaluation, and we isolate this name to this material, pending the collection of additional, better preserved specimens. Together, Baccaconularia and Conularia cambria contain the oldest large conulariids, and these narrow a stratigraphic gap between other large conulariids known from the Lower Ordovician onwards, and smaller fossils with conulariid affinities known only from Lower Cambrian rocks.

Terminal Cambrian and lowest Ordovician succession of Mexican West Gondwana: biotas and sequence stratigraphy of the Tiñu Formation

2007 ◽  
Vol 144 (6) ◽  
pp. 909-936 ◽  
Author(s):  
ED LANDING ◽  
STEPHEN R. WESTROP ◽  
JOHN D. KEPPIE
Keyword(s):  
Passive Margin ◽  
Tropical Species ◽  
Depositional Sequence ◽  
Northwest Mexico ◽  
The North ◽  
Late Cambrian ◽  
Lower Ordovician ◽  
Andean South America ◽  
Lower Palaeozoic ◽  
Proterozoic Basement

AbstractThe Tiñu Formation of Oaxaca State is the only fossiliferous lower Palaeozoic unit between the Laurentian platform in northwest Mexico and Gondwanan successions in Andean South America. The Tiñu traditionally has been referred to the Lower Ordovician (Tremadoc) and regarded as having a provincially mixed fauna with Laurentian, Avalonian, and Gondwanan elements. Bio- and lithostratigraphic re-evaluation demonstrates that the Tiñu is a Gondwanan, passive margin succession. It includes a lower, thin (to 16 m), condensed, uppermost Cambrian Yudachica Member (new). The Yudachica nonconformably overlies middle Proterozoic basement as a result of very high late Late Cambrian eustatic levels. The Yudachica changes from storm-dominated, but slightly dysoxic, shelf facies (fossil hash limestone and shale) in the south to an upper slope facies with debris flows 50 km to the north. Three biostratigraphically distinct depositional sequences comprise the Yudachica. The Yudachica has Gondwanan-aspect trilobites with low-diversity conodonts characteristic of unrestricted marine/temperate facies. The upper Tiñu, or Río Salinas Member (new), is a Lower Ordovician (Tremadoc) depositional sequence that records strong early, but not earliest, Tremadoc eustatic rise marked by graptolite- and olenid-bearing dysoxic mudstones. Higher strata shoal upward into shell-hash limestones and proximal tempestite sandstones with upper lower Tremadocian unrestricted marine/temperate conodonts. New taxa include Orminskia rexroadae Landing gen. et sp. nov. from the Cordylodus andresi Zone; this euconodont is related to hyaline coniform genera best known from Ordovician tropical platform successions. Cornuodus? clarkei Landing sp. nov. resembles the coeval, upper lower Tremadoc tropical species Scalpellodus longipinnatus (Ji & Barnes).

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