Reconstructing the Avalon continent: marginal to inner platform transition in the Cambrian of southern New Brunswick

1996 ◽  
Vol 33 (8) ◽  
pp. 1185-1192 ◽  
Author(s):  
Ed Landing
Keyword(s):  
North America ◽  
New Brunswick ◽  
Lower Cambrian ◽  
Saint John ◽  
Eastern Massachusetts

A west to east, marginal to inner Avalonian platform transition, comparable to that in southeast Newfoundland and southern Britain, is present in the Cambrian of southern New Brunswick. The Saint John–Caton's Island–Hanford Brook area lay on the marginal platform, and its thick, uppermost Precambrian–lower Lower Cambrian is unconformably overlain by trilobite-bearing, upper Lower Cambrian. An inner platform remnant is preserved in the Cradle Brook outlier 60 km northeast of Saint John. In contrast to the marginal platform sequences, the Cradle Brook outlier has a very thin lower Lower Cambrian and has middle Lower Cambrian strata (Bonavista Group) not present on the marginal platform. The Cradle Brook Lower Cambrian closely resembles inner platform successions in eastern Massachusetts and Trinity and Placentia bays, southeast Newfoundland. A limestone with Camenella baltica Zone fossils on Cradle Brook seems to be the peritidal limestone cap of the subtrilobitic Lower Cambrian known in Avalonian North America (Fosters Point Formation) and England (Home Farm Member).

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.

Radiometric dating of the Coldbrook Group of southern New Brunswick, Canada

1969 ◽  
Vol 6 (3) ◽  
pp. 393-398 ◽  
Author(s):  
R. F. Cormier
Keyword(s):  
New Brunswick ◽  
Lower Cambrian ◽  
Volcanic Rocks ◽  
The Other ◽  
Radiometric Dating ◽  
Late Devonian ◽  
Initial Ratio ◽  
Initial Value ◽  
Saint John ◽  
Probable Presence

The Coldbrook Group of southern New Brunswick is composed almost entirely of volcanic rocks and has been assigned a Precambrian age on the basis of field relationships. Rocks of the group are overlain by fossiliferous Lower Cambrian beds of the Saint John Group.Rubidium-strontium total-rock analyses of 46 samples of Coldbrook Group volcanic rocks have been carried out. Analysis of the data indicates the probable presence of two different isochron ages. One of these is apparently defined by those rocks in which the ratio 87Rb/86Sr is low, with values less than about 1.0. This isochron yields an age of 750 ± 80 million years, with an initial ratio 87Sr/86Sr of 0.7054 ± 0.0010. The other isochron is defined by rocks in which the value of the ratio 87Rb/86Sr is higher, with values greater than about 1.0. The age calculated from the second isochron is 370 ± 38 million years, with an indicated initial value for the ratio 87Sr/86Sr of 0.7135 ± 0.0010.The 750 million year age is interpreted to represent the time of extrusion of the Coldbrook volcanics. The 370 million year age appears to be secondary and related to metamorphism of the Coldbrook Group. This age is correlated with the Acadian orogeny, which strongly deformed this part of the northern Appalachians in Middle to Late Devonian time.

Upper Lower Cambrian depositional sequence in Avalonian New Brunswick

1996 ◽  
Vol 33 (3) ◽  
pp. 404-417 ◽  
Author(s):  
Ed Landing ◽  
Stephen R. Westrop
Keyword(s):  
New Brunswick ◽  
Lower Cambrian ◽  
Long Island ◽  
High Energy ◽  
Depositional Sequence ◽  
Middle Cambrian ◽  
Fine Grained ◽  
Volcanic Ashes ◽  
Saint John

The Hanford Brook Formation (emended) is a thin (up to 42+ m), upper Lower Cambrian depositional sequence that is unconformably bounded by the lower Lower Cambrian (Random Formation) and the middle Middle Cambrian (Fossil Brook Member of the Chamberlain's Brook Formation). These stratigraphic relationships of the trilobite-bearing Hanford Brook Formation indicate deposition on the Avalonian marginal platform in the Saint John, New Brunswick, region and provide more evidence for a uniform, latest Precambrian–Cambrian epeirogenic history and cover sequence in Avalon. The Hanford Brook Formation is a deepening–shoaling sequence with (i) lower, transgressive sandstone deposited in episodically high-energy environments (St. Martins Member, new); (ii) highstand–regressive, dysaerobic mudstone – fine-grained sandstone with volcanic ashes (Somerset Street Member, new); and (iii) upper, regressive, planar and hummocky cross-stratified sandstone (Long Island Member, new). Trilobites are common in the distal Somerset Street Member, and ostracodes and brachiopods dominate the St. Martins and Long Island members. Condensation of the St. Martins Member and absence of the Long Island Member where the Random Formation and Fossil Brook Member are thinnest suggest onlap of the Hanford Brook and pronounced, sub-Middle Cambrian erosion across epeirogenically active blocks in southern New Brunswick.

A newly recognized sequence of possible Early Cambrian age in southern New Brunswick: evidence for major southward-directed thrusting

1981 ◽  
Vol 18 (6) ◽  
pp. 1012-1017 ◽  
Author(s):  
M. J. McLeod ◽  
S. R. McCutcheon
Keyword(s):  
New Brunswick ◽  
Lower Cambrian ◽  
Volcanic Belt ◽  
Basal Part ◽  
Early Cambrian ◽  
Iapetus Ocean ◽  
Saint John

Several previously unidentified occurrences of possible Lower Cambrian strata have been discovered recently in the Eastern Volcanic Belt (Avalon zone) of southern New Brunswick. The basal part of the sequence is lithologically similar to the Lower Cambrian parastratotype on Hanford Brook near Saint John, New Brunswick. Some of the newly recognized Cambrian rocks crop out beneath major northeast-trending and north-dipping thrusts, and rest unconformably on subaqueous Upper Precambrian equivalents of the Coldbrook Group. The presence of these Cambrian rocks in the Eastern Volcanic Belt indicates that the Cambrian–Ordovician Iapetus Ocean transgressed across the entire Avalon zone of southern New Brunswick.

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.

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.

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