scholarly journals Age and geochemistry of Late Neoproterozoic and Early Cambrian igneous rocks in southern New Brunswick: similarities and contrasts

10.4138/1050 ◽  
2003 ◽  
Vol 39 (1) ◽  
Author(s):  
Sandra M. Barr ◽  
Chris E. White ◽  
Brent V. Miller
Keyword(s):  
New Brunswick ◽  
Igneous Rocks ◽  
Early Cambrian ◽  
Late Neoproterozoic

Neoproterozoic and Cambrian U–Pb (zircon) ages from Grand Manan Island, New Brunswick: implications for stratigraphy and northern Appalachian terrane correlations

2007 ◽  
Vol 44 (7) ◽  
pp. 911-923 ◽  
Author(s):  
B V Miller ◽  
S M Barr ◽  
R S Black
Keyword(s):  
New Brunswick ◽  
Long Island ◽  
Fault System ◽  
Bay Of Fundy ◽  
Early Cambrian ◽  
Island Formation ◽  
Rock Types ◽  
Head Formation ◽  
Minimum Age ◽  
Late Neoproterozoic

Pre-Mesozoic rocks are exposed on the southeastern third of Grand Manan Island and adjacent offshore islands in the Bay of Fundy. U–Pb (zircon) ages reported here demonstrate that most of these rocks are late Neoproterozoic to Early Cambrian. The oldest dated unit is the Ingalls Head Formation, from which two felsic tuff samples yielded ages of 617.6 ± 3.2 and 618.3 ± 2.8 Ma. The Three Islands granite, exposed only on offshore islands, is younger than the Ingalls Head Formation at 611.1 ± 2.4 Ma. It provides a minimum age for marble of the Kent Island Formation, which occurs as large xenoliths in the granite. The High Duck Island granite yielded an age of 547.3 ± 1.1 Ma, providing a minimum late Neoproterozoic age for the host Long Island Bay Formation. An age of 539.0 ± 3.3 Ma from a dacitic lithic-crystal tuff demonstrates that the Priest Cove Formation is earliest Cambrian; this supersedes a Silurian age previously suggested on the basis of poorly documented fossil evidence. The Long Pond Bay Formation is considered to be the youngest pre-Mesozoic unit on Grand Manan Island, based on petrological features, but a felsic intrusive sample from the unit yielded ca. 588 Ma xenocrystic zircon grains that provide only a maximum age for the unit. Although lack of exposed contacts or U–Pb ages from a few units precludes a complete stratigraphic picture, the ages reported here deomonstrate that most pre-Mesozoic units on Grand Manan Island are not Paleozoic as previously assumed. Some units on Grand Manan Island show similarities in rock types and ages to components in the Islesboro block in Penobscot Bay in coastal Maine. Overall, the range of ages and rock types suggests that they correlate with the New River and Mascarene terranes of southern New Brunswick, requiring an offset of at least 40 km between southern New Brunswick and adjacent Maine along the Grand Manan – Oak Bay fault system. Hence, both the Ganderia–Avalonia and Avalonia–Meguma boundaries lie farther offshore than Grand Manan Island.

Early Ordovician alkali-ultramafic Zhilandy complex (Central Kazakhstan): structure and age of formation

2019 ◽  
Vol 484 (1) ◽  
pp. 61-65
Author(s):  
R. M. Antonuk ◽  
A. A. Tretyakov ◽  
K. E. Degtyarev ◽  
A. B. Kotov
Keyword(s):  
Complex Formation ◽  
Central Asian Orogenic Belt ◽  
Early Cambrian ◽  
Early Ordovician ◽  
Late Cambrian ◽  
Central Asian ◽  
Geochronological Study ◽  
Three Stages ◽  
Late Neoproterozoic ◽  
Quartz Monzodiorites

U–Pb geochronological study of amphibole-bearing quartz monzodiorites of the alkali-ultramafic Zhilandy complex in Central Kazakhstan, whose formation is deduced at the Early Ordovician era (479 ± 3 Ma). The obtained data indicate three stages of intra-plate magmatism in the western part of the Central Asian Orogenic Belt: Late Neoproterozoic stage of alkali syenites of the Karsakpay complex intrusion, Early Cambrian stage of ultramafic-gabbroid plutons of the Ulutau complex formation, and Late Cambrian–Early Ordovician stage of formation of the Zhilandy complex and Krasnomay complex intrusions.

scholarly journals Geochemical features, sources and geodynamic settings of accumulation of the cambrian sedimentary rocks of the Mel’gin trough (Bureya continental massif)

2019 ◽  
Vol 64 (5) ◽  
pp. 503-519
Author(s):  
R. O. Ovchinnikov ◽  
A. A. Sorokin ◽  
V. P. Kovach ◽  
A. B. Kotov
Keyword(s):  
Continental Margin ◽  
Active Continental Margin ◽  
Sedimentary Rocks ◽  
Detrital Zircons ◽  
Igneous Rocks ◽  
Early Cambrian ◽  
Relative Probability ◽  
Early Proterozoic ◽  
Geodynamic Settings ◽  
Probability Plots

The first data about geochemical features of the Cambrian sedimentary rocks of the Mel’gin trough of the Bureya continental Massif, as well as ages of detrital zircons of them are obtained. It is established, that among the detrital zircons from the sandstones of the Chergilen and Allin formations of the Mel’gin trough zircons with Late Riphean (peaks on relative probability plots – 0.78, 0.82, 0.94, 1.04 Ga) and Early Riphean (peaks on relative probability plots – 1.38, 1.45, 1.64 Ga) ages predominate. The single grains have a Middle Riphean, Early Proterozoic and Late Archean ages. We can suppose, that the sources of Late Riphean detrital zircons from sandstones of the Chergilen and Allin formations are igneous rocks of gabbro-granitoids (940–933 Ma) and granite- leucogranites (804–789 Ma) association, identified in the Bureya continental Massif. We can`t assume, what kind of rocks were the source for Middle Riphean and older detrital zircons from the Cambrian sedimentary rocks of the Bureya continental Massif, because in this massif still do not identified complexes older Late Riphean age. The most probable geodynamic conditions of accumulation of the Cambrian deposits of the Mel’gin trough is the conditions of active continental margin, which is corresponding to of Early Cambrian granitoids magmatism.

Lower Cambrian (Branchian) trilobites and biostratigraphy of the Hanford Brook Formation, southern New Brunswick

2000 ◽  
Vol 74 (5) ◽  
pp. 858-878 ◽  
Author(s):  
Stephen R. Westrop ◽  
Ed Landing
Keyword(s):  
New Species ◽  
Nova Scotia ◽  
North America ◽  
New Brunswick ◽  
Lower Cambrian ◽  
Early Cambrian ◽  
The West ◽  
Middle Cambrian ◽  
Sequence Stratigraphic ◽  
Two New Species

The Hanford Brook Formation, one of the classic Cambrian units of Avalonian North America, contains at least eight species of endemic trilobites, including Berabichia milleri Westrop n. sp., that are assigned to seven genera. The vertical succession of faunas is far more complex than has been recognized previously, with each member containing a lithofacies-specific assemblage. These are, in ascending order: a bradoriid-linguloid Association without trilobites in the nearshore St. Martin's Member, a Protolenus Association in dysaerobic siltstones and sandstones of the Somerset Street Member, and a Kingaspidoides-Berabichia Association in hummocky cross-stratified sandstones of the Long Island Member that overlie a parasequence boundary at Hanford Brook. Due to the breakdown of biogeographic barriers in the late Early Cambrian, two new species-based zones, the Protolenus elegans and Kingaspidoides cf. obliquoculatus zones, share trilobite genera with the Tissafinian Stage of Morocco. This generic similarity has been the basis for correlation of this upper Lower Cambrian interval on the Avalon continent with the West Gondwanan lowest Middle Cambrian. However, the clear facies control on the occurrence of genera in the Hanford Brook Formation and the presence of an abrupt faunal break and unconformity at the base of the Tissafinian in Morocco makes this correlation questionable. The Hanford Brook Formation may represent a late Early Cambrian interval unknown in Gondwana. Sequence-stratigraphic criteria even raise the possibility that the Protolenus Association is the biofacies equivalent of Callavia broeggeri Zone faunas of the Brigus Formation of Newfoundland, Nova Scotia and Massachusetts.

Occurrence of the siliceous sponge spicule Konyrium (Hexactinellida) in the upper Cambrian of the Mackenzie Mountains, northwestern Canada

2002 ◽  
Vol 76 (3) ◽  
pp. 565-569 ◽  
Author(s):  
Brian R. Pratt
Keyword(s):  
Fossil Record ◽  
Southern China ◽  
South Australia ◽  
Early Cambrian ◽  
Siliceous Sponge ◽  
Sponge Spicule ◽  
Animal Phyla ◽  
Sponge Diversity ◽  
Siliceous Sponges ◽  
Late Neoproterozoic

The fossil record of siliceous sponges—Hexactinellida and demosponge “Lithistida”—hinges upon both body fossils plus isolated spicules mostly recovered from limestones by acid digestion. The earliest record of siliceous sponge spicules extends back to the late Neoproterozoic of Hubei, southern China (Steiner et al., 1993) and Mongolia (Brasier et al., 1997), and body fossils attributed to the hexactinellids have been described from the Ediacaran of South Australia (Gehling and Rigby, 1996); thus they are the oldest-known definite representatives of extant animal phyla. The Early Cambrian saw a remarkable diversification in spicule morphology, with the appearance of an essentially “modern” array of forms (Zhang and Pratt, 1994). While a diversity decline may have occurred with the late Early Cambrian extinction(s), the subsequent Paleozoic and Mesozoic fossil record of spicules shows a relatively consistent range of morphologies (e.g., Mostler, 1986; Bengtson et al., 1990; Webby and Trotter, 1993; Kozur et al., 1996; Zhang and Pratt, 2000). However, because spicule form is not restricted to individual taxa and many sponge species secrete a variety of spicule shapes, it is difficult to gauge true siliceous sponge diversity and to explore their biostratigraphic utility using only isolated spicules.

Cambrian biostratigraphy of the Tal Group, Lesser Himalaya, India, and early Tsanglangpuan (late early Cambrian) trilobites from the Nigali Dhar syncline

2005 ◽  
Vol 142 (1) ◽  
pp. 57-80 ◽  
Author(s):  
NIGEL C. HUGHES ◽  
SHANCHI PENG ◽  
O. N. BHARGAVA ◽  
A. D. AHLUWALIA ◽  
SANDEEP WALIA ◽  
...  
Keyword(s):  
Southwest China ◽  
Early Cambrian ◽  
Lesser Himalaya ◽  
Geographic Proximity ◽  
Late Cambrian ◽  
Assemblage Zone ◽  
Late Neoproterozoic ◽  
Spiti Region ◽  
The Himalaya ◽  
Tethyan Himalaya

Precise biostratigraphic constraints on the age of the Tal Group are restricted to (1) a basal level correlative with the Anabarites trisulcatus–Protohertzina anabarica Assemblage Zone of southwest China, (2) a level near the boundary of the lower and upper parts of the Tal Group correlative with the early Tsanglangpuan Stage (Drepanuroides Zone), and (3) an interval low in the upper part of the Tal Group correlative with later in the Tsanglangpuan Stage (Palaeolenus Zone). These correlations are based on small shelly fossil and trilobite taxa. Other chronostratigraphic constraints include the marked negative δ13C isotopic excursion coincident with the transition from the Krol Group to the Tal Group. This excursion is used as a proxy for the Precambrian–Cambrian boundary in several sections worldwide and, if applied to the Lesser Himalaya, indicates that the boundary is at or just above the base of the Tal Group. The upper parts of the Tal Group may be of middle or late Cambrian age and might form proximal equivalents of sections in the Zanskar–Spiti region of the Tethyan Himalaya. Both faunal content and lithological succession are comparable to southwest China, furthering recent arguments for close geographic proximity between the Himalaya and the Yangtze block during late Neoproterozoic and early Cambrian time. Trilobites from the uppermost parts of the Sankholi Formation from the Nigali Dhar syncline are described and referred to three taxa, one of which, Drepanopyge gopeni, is a new species. They are the oldest trilobites yet described from the Himalaya.

A probable late Neoproterozoic age for the Kennedy Channel and Ella Bay formations, northeastern Ellesmere Island and its implications for passive margin history of the Canadian Arctic

2004 ◽  
Vol 41 (9) ◽  
pp. 1013-1025 ◽  
Author(s):  
Keith Dewing ◽  
J C Harrison ◽  
Brian R Pratt ◽  
Ulrich Mayr
Keyword(s):  
Lower Cambrian ◽  
Canadian Arctic ◽  
Passive Margin ◽  
Early Cambrian ◽  
Channel Formation ◽  
Type Section ◽  
Small Shelly Fossils ◽  
History Of ◽  
Basin Formation ◽  
Late Neoproterozoic

The Kennedy Channel and Ella Bay formations are the two oldest stratigraphic units exposed in the Franklinian margin sedimentary sequence in the Canadian Arctic Islands. An Early Cambrian age had previously been accepted by the occurrence of trilobites and small shelly fossils in the type section of the Kennedy Channel Formation. Reinvestigation of the area around the type section shows that several large strike-slip faults cut the succession and that the olenelloid trilobites are from an infaulted slice of a younger unit, the Lower Cambrian Kane Basin Formation. Thus, there is no unambiguous paleontological evidence for the age of either the Kennedy Channel or Ella Bay formations. However, the abundance of stromatolites, absence of trace fossils, and separation from overlying Lower Cambrian clastics by a regional angular unconformity indicate a probable late Neoproterozoic age for these two formations. The Ella Bay Formation likely correlates with the Portfjeld Formation in North Greenland, the Spiral Creek Formation in East Greenland, and the Risky Formation of the Mackenzie Mountains in northwestern Canada. The passive margin that existed in northern Laurentia during the early Paleozoic was, therefore, established in the late Neoproterozoic, and the onset of rifting must have preceded this, rather than occurring in the Early Cambrian as some authors have suggested.

Faunas and Cambrian volcanism on the Avalonian marginal platform, southern New Brunswick

2008 ◽  
Vol 82 (5) ◽  
pp. 884-905 ◽  
Author(s):  
Ed Landing ◽  
Susan C. Johnson ◽  
Gerd Geyer
Keyword(s):  
New Brunswick ◽  
Sea Level ◽  
Lower Cambrian ◽  
Volcanic Edifice ◽  
Early Cambrian ◽  
Early Paleozoic ◽  
Middle Cambrian ◽  
Cool Water ◽  
Senior Synonym ◽  
Lane Formation

The Cambrian inlier at Beaver Harbour, southern New Brunswick, is now confidently referred to the marginal platform of the late Proterozoic–Early Paleozoic Avalon microcontinent. The sub-trilobitic Lower Cambrian Chapel Island and Random Formations are unconformably overlain by the mafic volcanic-dominated Wade's Lane Formation (new). Late Early Cambrian trilobites and small shelly taxa in the lowest Wade's Lane demonstrate a long Random–Wade's Lane hiatus (middle Terreneuvian–early Branchian). Latest Early–middle Middle Cambrian pyroclastic volcanism produced a volcanic edifice at Beaver Harbour that is one of three known volcanic centers that extended 550 km along the northwest margin of Avalon. Middle Middle Cambrian sea-level rise, probably in theParadoxides eteminicusChron, mantled the extinct volcanics with gray-green mudstone and limestone of the Fossil Brook Member. Black, dysoxic mudstone of the upper Manuels River Formation (upper Middle Cambrian,P. davidisZone) is the youngest Cambrian unit in the Beaver Harbour inlier.Lapworthella cornu(Wiman, 1903) emend., a senior synonym of the genotypeL. nigra(Cobbold, 1921),Hyolithellus sinuosusCobbold, 1921, and probablyAcrothyra seraMatthew, 1902a, range through the ca. 8 m.y. of the trilobite-bearing upper Lower Cambrian, andH. sinuosusandA. serapersist into the middle Middle Cambrian.Lapworthella cornuandH. sinuosusreplaced the tropical taxaL. schodackensis(Lochman, 1956) andH. micansBillings, 1872, in cool-water Avalon.

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