Tidal deposits of the Lower Cambrian Random Formation, eastern Newfoundland: facies and paleoenvironments

1982 ◽  
Vol 19 (10) ◽  
pp. 2028-2042 ◽  
Author(s):  
Richard N. Hiscott
Keyword(s):  
Lower Cambrian ◽  
Density Currents ◽  
Intertidal Environment ◽  
Storm Activity ◽  
Late Precambrian ◽  
Appalachian Orogen ◽  
Lenticular Bedding ◽  
Global Sea Level ◽  
Shallow Marine Sediments ◽  
Open Shelf

The Avalon tectonostratigraphic zone occupies about 25% of the area of insular Newfoundland. Late Precambrian development of the Avalon terrane is distinctly different than that of other parts of the Appalachian orogen and cratonic North America. Late Precambrian volcanism and tectonic instability gave way to deposition of about 2 km of Cambrian and Lower Ordovician dominantly epiclastic sediments on a slowly subsiding, relatively stable shelf platform.The Lower Cambrian Random Formation is part of the platformal sequence and is bounded by regional disconformities over much of the Newfoundland Avalon Zone, except around Fortune Bay where it is underlain by older terrestrial and shallow-marine sediments. The Random Formation was deposited during a time of global sea-level rise, and consists of up to 250 m of shoreline, nearshore, and open-shelf deposits that record macrotidal conditions and periodic storm activity. Cross-bedded quartzarenites occur in units to about 50 m thick (one exceptional unit is 110 m thick) that tend to have gradational bases and abrupt tops. Bimodal–bipolar paleocurrent data are best explained by reversing tidal currents. These sandstone units show no evidence of intertidal (beach) processes and are therefore interpreted as subtidal ridges or shoals. The intertidal environment is represented by a shaly unit, with thin sandstone beds, that is characterized by flaser and lenticular bedding, oscillation (wave) ripples, some flat-topped ripples, and abundant synaeresis (dehydration) cracks. A muddy shoreline and subtidal sands suggest a macrotidal setting.Storm deposits range from: (1) fine, micaceous, red sandstones with fiat, gently dipping lamination, low-angle truncation surfaces, rare hummocks, shale-clast horizons, granule lags, and steep-sided erosional gulleys believed to represent lower shoreface rip-current channels; to (2) mudstones with graded, sole-marked, glauconitic sandstone beds deposited on an open shelf by storm-generated density currents.

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 Precambrian–Cambrian boundary problem and its prospects, Northwest Himalaya, India

1984 ◽  
Vol 121 (3) ◽  
pp. 211-219 ◽  
Author(s):  
G. Kumar ◽  
B. K. Raina ◽  
O. N. Bhargava ◽  
P. K. Maithy ◽  
R. Babu
Keyword(s):  
Boundary Problem ◽  
Lower Cambrian ◽  
Trace Fossils ◽  
Northwest Himalaya ◽  
Late Precambrian

AbstractThe Precambrian–Cambrian boundary problem is being studied in an areno-argillaceous sequence in the Kashmir and Spiti Valley, Northwest Himalaya, India. In Kashmir, a rich and diversified microbiota – cryptarchs and algae of the Late Precambrian, and low Lower Cambrian trace fossils are recorded. In the Spiti Valley, the yield of microbiota is poor and the trace fossils are late Lower Cambrian.

The oldest sequence of skeletal fossils in the Lower Cambrian of southeastern Newfoundland

1983 ◽  
Vol 20 (4) ◽  
pp. 525-536 ◽  
Author(s):  
Stefan Bengtson ◽  
Terence P. Fletcher
Keyword(s):  
Siberian Platform ◽  
Lower Cambrian ◽  
Short Interval ◽  
Time Span ◽  
Early Cambrian ◽  
Late Precambrian ◽  
Complete Sequences ◽  
Continuous Sedimentation

Sections on the Burin Peninsula in southeastern Newfoundland show a record of continuous sedimentation during the Late Precambrian–Early Cambrian transition. These may be correlated lithologically and biostratigraphically with less complete sequences on the Avalon and Bonavista Peninsulas. Below the oldest known trilobites in southeastern Newfoundland (of the Callavia Zone) two consecutive assemblages of skeletal fossils are recognizable: an Aldanella attleborensis assemblage and the succeeding Coleoloides typicalis assemblage. The shift between the two assemblages takes place within the Bonavista Formation in the Avalon–Bonavista region and in a similar succession of mudstones near St. Lawrence on the Burin Peninsula. The quartzitic Random Formation appears to have been deposited during a short interval within the time span represented by the A. attleborensis assemblage, and there is no conclusive biostratigraphical evidence of any major diachronism of this unit. The A. attleborensis assemblage contains taxa known from the lower part of the Tommotian Stage on the Siberian Platform. It is interpreted to be of Tommotian age, and the subsequent shift to the C. typicalis assemblage is tentatively correlated with the Tommotian–Atdabanian boundary as recognized in Siberia.

Depositional controls on Early Cambrian microbial carbonates from the Montagne Noire, southern France

1998 ◽  
Vol 89 (3) ◽  
pp. 135-143 ◽  
Author(s):  
J. Javier Álvaro ◽  
Emmanuelle Vennin ◽  
Daniel Vizcaïno
Keyword(s):  
Lower Cambrian ◽  
Southern France ◽  
Microbial Structures ◽  
Subaerial Exposure ◽  
Open Sea ◽  
Montagne Noire ◽  
Constructed Self ◽  
Depositional Controls ◽  
First Time ◽  
Open Shelf

AbstractLower Cambrian shallow-water carbonates enclosing microbial structures are documented for the first time from the upper Lastours Member of the Montagne Noire (southern France). Microbial organisms constructed self-supported boundstones resulting in the formation of exclusively microbial-accreted buildups, which exhibit three main types of non-skeletal microbialites: planar stratiform stromatolites, dome-shaped stromatolites and nonlaminated (thrombolitic) biostromes. In addition, thrombolitic boundstones display four distinct microbial microstructures: clotted andRenalcis-like forms, branching bushy forms, clusters of unbranching straight filaments and crustose forms.The upper member of the Lastours Formation records an upward transition from a shalydominant open shelf to a protected shelf environment bounded by a surface representing a major subaerial exposure. Initially, at the inception of the highstand systems tract, flat stratiform stromatolites formed on open sea subtidal shaly substrates, while stacked domal stromatolites developed in peritidal areas which record subaerial exposure. In contrast, prograding shoal barriers of the transgressive systems tract favoured the establishment of thrombolitic boundstones in protected (back-shoal) environments.

scholarly journals Ordovician mafic magmatism in an Ediacaran arc complex, Sibak, northeastern Iran: the eastern tip of the Rheic Ocean

2018 ◽  
Vol 55 (10) ◽  
pp. 1173-1182 ◽  
Author(s):  
Fereshteh Ranjbar Moghadam ◽  
Fariborz Masoudi ◽  
Fernando Corfu ◽  
Seyed Massoud Homam
Keyword(s):  
Indirect Evidence ◽  
Arc Magmatism ◽  
Early Paleozoic ◽  
Northern Margin ◽  
Rheic Ocean ◽  
Late Precambrian ◽  
Sedimentary Sequences ◽  
Appalachian Orogen ◽  
Laurentian Margin ◽  
Clastic Sedimentary

The assembly of Gondwana in the Ediacaran was concluded by extensive arc magmatism along its northern margin. Extensional events in the early Paleozoic led to rifting and the eventual separation of terranes, which were later assimilated in different continents and orogens. The Sibak area of northeastern Iran records these events, including late Precambrian volcanic-sedimentary processes, metamorphism, and magmatism. A granite at Chahak in the Sibak Complex yields a zircon U–Pb age of 548.3 ± 1.1 Ma, whereas a spatially associated gabbro has an age of 471.1 ± 0.9 Ma. The latter corresponds to the earliest stages of rifting in the nearby Alborz domain, with the deposition of clastic sedimentary sequences, basaltic volcanism, and, as indicated by indirect evidence, coeval granitic plutonism. The Chahak gabbro is thus one of the earliest witnesses of the rifting processes that eventually led to the development of the Rheic Ocean and were indirectly linked to subduction of Iapetus at the Laurentian margin and the early development of the Appalachian orogen.

Sm–Nd isotopic geochemistry of Precambrian to Paleozoic granitoid suites and the deep-crustal structure of the southeast margin of the Newfoundland Appalachians

1995 ◽  
Vol 32 (2) ◽  
pp. 224-245 ◽  
Author(s):  
Andrew Kerr ◽  
George A. Jenner ◽  
Brian J. Fryer
Keyword(s):  
Fault System ◽  
Mobile Belt ◽  
Simple Extension ◽  
Precambrian Basement ◽  
Zone Boundary ◽  
First Order ◽  
Metasedimentary Rocks ◽  
Late Precambrian ◽  
Deep Crustal Structure ◽  
Appalachian Orogen

In the Eastern Central Mobile Belt of the Newfoundland Appalachians, late Precambrian basement inliers have εNd from −3 to +2, but Cambro-Ordovician metasedimentary rocks have initial εNd below −7. This region is inferred to have an "inverted" crustal residence structure, which influenced subsequent Appalachian-cycle magmatism. Ordovician and Silurian granitoid suites have εNd of −8 to −2, bracketing both basement and cover, but peraluminous, "S-type" granites have the lowest εNd. Devonian granites have initial εNd values from −5 to +1, and low εNd is associated with peraluminous character. These Paleozoic granites show geographic trends, with lowest εNd values in areas where metasedimentary rocks are abundant. They are suggested to contain anatectic material from both Precambrian basement and metasedimentary cover, but some "I-type" suites probably also include a mantle-derived component. In the adjacent Avalon Zone, Precambrian plutonic suites mostly have εNd from +1 to +6, but there are negative εNd values (−8 to −4) in the westernmost Avalon Zone. Devonian plutonic suites mostly have εNd from +2 to +5. Thus, the Precambrian crust of the Avalon Zone is largely "juvenile," except at its westernmost edge. Contrasts across the Eastern Central Mobile Belt–Avalon Zone boundary, defined by the Dover–Hermitage Bay fault system, indicate a major, crustal-scale structure, and suggest an isotopically distinct "central block" beneath the central Appalachian Orogen, rather than a simple extension of "Avalonian" crust. Similar geographic–isotopic patterns have been reported in Nova Scotia and New Brunswick, suggesting that this pattern represents a first-order deep-crustal subdivision of the northern Appalachian Orogen.

The Cambrian Fauna of the Leny Limestone, Perthshire, Scotland

2007 ◽  
Vol 98 (02) ◽  
pp. 199-218 ◽  
Author(s):  
Terence P. Fletcher ◽  
Adrian W. A. Rushton
Keyword(s):  
New York ◽  
North American ◽  
Lower Cambrian ◽  
Outer Edge ◽  
Open Ocean ◽  
Middle Cambrian ◽  
Middle Ordovician ◽  
The North ◽  
Appalachian Orogen ◽  
Selection Of

ABSTRACTDark limestones in the old quarries at Leny, Perthshire contain sparse beds with tiny fossils. They are poorly preserved and, though barely affected by the Ordovician Grampian Event tectonism, there is some taphonomic distortion and many are corroded along stylolitised horizons. The fauna mainly comprises trilobites of two types, open-ocean miomerids and polymerid shelf dwellers. MiomeridsCondylopygecf.eliandKiskinella cristataindicate a stratigraphical position equivalent to the base of the paradoxidid Amgan Stage of Siberia; traditionally regarded as ‘Middle Cambrian’. However, the bulk of the Leny miomerids, notably species ofPagetides, are forms described from the outer edge of Laurentia, within theBonnia–OlenellusZone, where it is considered to be ‘Lower Cambrian’. The Leny polymerids were likely transported off-shelf and some are conspecific with taxa in the Laurentian allochthonous Quebec and New York successions of the Early–Middle Ordovician (Taconic) Appalachian Orogen. The Leny Limestone and Shale Member of the Keltie Water Grit Formation is part of the Dalradian Supergroup deposited in an off-shelf Caledonide Grampian Terrane of the Humber Tectonostratigraphical Zone, midway between the North American successions and the Greenland Caledonides.Additional to the trilobites, brachiopods, sponges, hyoliths, bradoriids and a selection of indeterminable organic fragments occur; none of which has any particular age significance.

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.

Hydrocarbon biomarkers and diamondoid hydrocarbons from late Precambrian and lower Cambrian rocks of the Katanga saddle (Siberian Platform)

2017 ◽  
Vol 55 (4) ◽  
pp. 360-366 ◽  
Author(s):  
G. N. Gordadze ◽  
V. Yu. Kerimov ◽  
A. V. Gaiduk ◽  
M. V. Giruts ◽  
M. A. Lobusev ◽  
...  
Keyword(s):  
Siberian Platform ◽  
Lower Cambrian ◽  
Late Precambrian ◽  
Hydrocarbon Biomarkers

On the Late Precambrian–Early Cambrian Hartshill Formation of Warwickshire

1978 ◽  
Vol 115 (1) ◽  
pp. 21-36 ◽  
Author(s):  
M. D. Brasier ◽  
R. A. Hewitt ◽  
C. J. Brasier
Keyword(s):  
Shallow Water ◽  
Lower Cambrian ◽  
Volcanic Rocks ◽  
Trace Fossils ◽  
Early Cambrian ◽  
Late Precambrian

SummaryThe Hartshill Formation (c. 270 m) consists largely of shallow-water feldspathic sandstones and greywackes lying unconformably on Precambrian (Vendian?) volcanic rocks and below shales with the first olenellid trilobites. Five members are recognized. The Park Hill Member is conglomeratic and arkosic near the base, passing up into green-grey megarippled quartzites with some thick shale bands. The Tuttle Hill Member is more shaly and glauconitic with conspicuous bioturbation. The Jee's Member is of distinctly cross-laminated glauconitic, feldspathic greywackes and shales with numerous trace fossils. Conglomerates, shales, sandstones, phosphorites and limestones comprise the Home Farm Member, withadiverse Tommotiantype shelly fauna and stromatolites near the top. Massive arkoses and greywackes of the Woodlands Member yield similar shelly fossils in calcareous beds at the base and top while the overlying Purley Shale yields the first Lower Cambrian trilobites.

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