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.

Kennedy Channel Formation: key to the early history of the Franklinian continental margin, central eastern Ellesmere Island, Arctic Canada

1989 ◽  
Vol 26 (6) ◽  
pp. 1147-1159 ◽  
Author(s):  
D. G. F. Long
Keyword(s):  
Canadian Arctic ◽  
Basin Evolution ◽  
Early Cambrian ◽  
Channel Formation ◽  
Late Precambrian ◽  
The Third ◽  
History Of ◽  
Diagenetic Facies ◽  
Shelf Margin ◽  
Water Facies

The Franklinian sequence in the Canadian Arctic Islands may have been initiated by rifting in Late Proterozoic or Early Cambrian times. Unfortunately, no record of this early phase of basin evolution is exposed; the oldest known strata are weakly metamorphosed mudstones, limestones, and sandstones of the Kennedy Channel Formation. Although these have previously been considered late Precambrian in age, the presence of minor trilobite and brachiopod debris indicates an Early Cambrian age, possibly corresponding to a pre-Olenellus trilobite zone. Strata of the Kennedy Channel Formation reflect repeated progradation of shallow-water facies into a slowly subsiding basin that developed in response to subsidence at a late stage of rift development along the Franklinian shelf margin. The first two cycles involve storm- and tide-influenced clastics derived from the Precambrian Shield to the southeast, whereas the third and fourth cycles involve progradation of carbonate ramp and rimmed platform facies. The contact with overlying dolostones of the Ella Bay Formation represents a depositional and diagenetic facies boundary and not an unconformity.

Lower Cambrian (Series 2) small shelly fossils from along Nares Strait (Nunavut and Greenland; Laurentia)

2021 ◽  
pp. 495-504
Author(s):  
John S. Peel ◽  
Christian B. Skovsted
Keyword(s):  
Lower Cambrian ◽  
Ellesmere Island ◽  
Channel Formation ◽  
Inner Shelf ◽  
Nares Strait ◽  
Small Shelly Fossils ◽  
Stage 4 ◽  
Shelf Sediments ◽  
Basin Formation ◽  
North Greenland

Three small assemblages of lower Cambrian (Cambrian Series 2, Stage 4) small shelly fossils are described from Laurentian strata astride Nares Strait. The fauna from the Humboldt Formation of Daugaard-Jensen Land, North Greenland, is derived from inner shelf sediments deposited on the stable craton of the Inglefield Land High. Fossils from Judge Daly Promontory, eastern Ellesmere Island, Nunavut, occur in strata of the Cambrian Ellesmere Group (Kane Basin Formation) that have been structurally juxtaposed against older strata; they were originally assigned to the Kennedy Channel Formation, which is now considered to be of Neoproterozoic age. A similar fauna from offshore environments of the Aftenstjernesø Formation in northern Nyeboe Land, North Greenland, reflects the regional structural and sedimentological continuity with the Canadian Cambrian succession. Pojetaia robsonae sp. nov. is described from Judge Daly Promontory.

The Placentian Series: appearance of the oldest skeletalized faunas in southeastern Newfoundland

1989 ◽  
Vol 63 (6) ◽  
pp. 739-769 ◽  
Author(s):  
Ed Landing ◽  
Paul Myrow ◽  
Alison P. Benus ◽  
Guy M. Narbonne
Keyword(s):  
Lower Cambrian ◽  
Early Cambrian ◽  
Island Formation ◽  
Left Handed ◽  
Small Shelly Fossils ◽  
Body Fossil ◽  
Offshore Muds ◽  
Block Faulting ◽  
Phosphate Deposits ◽  
High Diversity

The lowest Cambrian of Avalon, or Placentian Series, is a relatively thick sequence (1,400 m) in southeastern Newfoundland. A newly proposed body fossil zonation supplements an existing trace fossil zonation of the lower part of the Placentian Series and includes strata to the top of the sub-trilobitic Lower Cambrian.The Sabellidites cambriensis Zone brackets the Precambrian–Cambrian boundary and comprises peritidal and wave-influenced subtidal facies deposited during deepening through the lower part of the Chapel Island Formation. Younger “Ladatheca” cylindrica Zone strata include the deepest facies of the Chapel Island Formation. The base of the overlying Watsonella crosbyi Zone (a post-Nemakit Daldyn and pre-Tommotian equivalent) is significantly diachronous because the diagnostic mollusks were preferentially preserved in pyritiferous offshore muds rather than in coeval nearshore muds. High diversity, upper Watsonella crosbyi Zone faunas (18 species) are limited to peritidal limestones of member 4 and are dominated by calcareous small shelly fossils. A thick interval (ca. 430 m) without body fossils and an important episode of block faulting that led to 750 m of differential erosion preceded deposition of the lower part of the Bonavista Group (=Sunnaginia imbricata Zone, an interval considered to be largely older than the Tommotian). Although much Early Cambrian time may be lost as a result of erosion at Random Formation–Bonavista Group unconformities, many Watsonella crosbyi Zone species reappear in the Sunnaginia imbricata Zone. Shoaling accompanied the immigration event defining the base of the Camenella baltica Zone, and an unconformity following regional offlap marks the top of the Placentian Series.Calcareous, and not phosphatic, composition is most common in earliest Cambrian shelly remains. Little evidence suggests that a global, Precambrian–Cambrian boundary interval “phosphogenic” event either resulted in deposition of local phosphate deposits in the Tethyan region or had a role in the appearance of mineralized skeletons.Twenty metazoans and problematica and an alga are illustrated from the Chapel Island Formation. Bemella? vonbitteri Landing n. sp. and Halkieria stonei Landing n. sp. are described. The monoplacophoran Archaeospira? avalonensis Landing n. sp. has right-and left-handed conchs comparable to those of Archaeospira (=Yangtzespira) from China. Anabarites is the senior generic synonym of Tiksitheca.

Testing the Darwinian legacy of the Cambrian radiation using trilobite phylogeny and biogeography

1999 ◽  
Vol 73 (2) ◽  
pp. 176-181 ◽  
Author(s):  
Bruce S. Lieberman
Keyword(s):  
Early Cambrian ◽  
Evolutionary Patterns ◽  
Earth History ◽  
Tectonic Events ◽  
Biological Meaning ◽  
History Of ◽  
Cambrian Radiation ◽  
Special Rules ◽  
Late Neoproterozoic ◽  
Patterns And Processes

Since the publication of Darwin (1859), the biological meaning of the Cambrian radiation has been debated. Most commentators agree, however, that the Cambrian radiation is fundamentally a time of major metazoan cladogenesis. In and of itself this does not necessarily mean that unique evolutionary processes operated during the Cambrian radiation. Phylogenetic analysis has been used to study the tempo of speciation during the radiation, and thus far there is no need to invoke special rules relating to the tempo of evolution. Instead, what seems unique about the Cambrian radiation is its place as an important episode in the history of life—that is, as the first major radiation of the Metazoa. Although the tempo of evolution during the Cambrian radiation may not have been uniquely high, there were largely unique tectonic events that transpired during the late Neoproterozoic and Early Cambrian, such as extensive cratonic fragmentation. Biogeographic analysis of Early Cambrian olenelloid trilobites reveals that these tectonic events powerfully influenced evolutionary and distributional patterns in this diverse and abundant trilobite group. This emphasizes the importance of physical earth history in generating evolutionary patterns. In the general study of macroevolutionary patterns and processes, earth history phenomena emerge as powerful forces influencing the history of life and provide insights into evolution that can best be inferred by paleontological data.

Cambrian detrital zircon signatures of the northern Cordilleran passive margin, Liard area, Canada: evidence of sediment recycling, non-Laurentian ultimate sources, and basement denudation

2017 ◽  
Vol 54 (6) ◽  
pp. 609-621
Author(s):  
Margot McMechan ◽  
Lisel Currie ◽  
Filippo Ferri ◽  
William Matthews ◽  
Paul O’Sullivan
Keyword(s):  
North American ◽  
Detrital Zircon ◽  
Lower Cambrian ◽  
Probability Distributions ◽  
Detrital Zircons ◽  
Passive Margin ◽  
Early Cambrian ◽  
Middle Cambrian ◽  
Middle Member

Detrital zircon U–Pb age probability distributions for the Cambrian Vizer formation (informal) and Mount Roosevelt Formation (middle member) of the northern Canadian Cordilleran passive margin indicate extensive recycling from ∼1.7 to 1.6 Ga Paleoproterozoic sandstones and Proterozoic and Lower Cambrian strata, respectively. The units have minor or no first cycle input from Laurentian basement. The lower part of the Vizer formation contains North American magmatic gap (1610–1490 Ma) detrital zircons and lacks ultimate Grenvillian sourced grains, indicating that the grains were likely sourced from a nearby Mesoproterozoic basin and have an ultimate non-Laurentian source. Detrital zircon U–Pb ages of 670–640 Ma from the middle member of the Mount Roosevelt Formation indicate associated volcanic clasts were locally sourced, and are not of syn-sedimentary Middle Cambrian age. Provenance of these units was indirectly impacted by the Liard Line basement feature. Detrital zircon U–Pb age probability distributions from the northern Canadian Cordilleran passive margin indicate sediments were sourced from the east in the Early Cambrian (Terreneuvian; Vizer formation and correlatives) and the northeast during Early Cambrian (Series 2) deposition of Sekwi Formation and correlative strata. In the early Middle Cambrian, the middle member of the Mount Roosevelt Formation was primarily locally sourced, whereas the upper member was derived from Laurentian basement to the east and southeast. The change from reworked Paleoproterozoic cover in the Terrenuvian to primary basement sources in the Middle Cambrian suggests significant denudation of the basement occurred southeast of the Liard Line.

scholarly journals Phylogenetic history of major trilobite clades in relation to paleoenvironment

1992 ◽  
Vol 6 ◽  
pp. 104-104
Author(s):  
Richard A. Fortey ◽  
Robert M. Owen
Keyword(s):  
North Africa ◽  
Deep Water ◽  
Fossil Record ◽  
Lower Cambrian ◽  
Good Evidence ◽  
Major Clade ◽  
Small Shelly Fossils ◽  
Marine Habitats ◽  
History Of

Because trilobites occupied a wide a range of Paleozoic marine habitats they are a good group to examine hypotheses concerning the sites in which new major clades first appear, and their subsequent history of diversification and decline. There are several problems in this endeavour. The first concerns classification. Until a complete phylogenetic classification is available, there is no objective way to assess the equivalence or otherwise of groups which have been claimed as orders. For example, Odontopleurida and Lichida are treated as separate orders in some classifications, but are considered as a single major clade - presumably of ordinal status - in others. Some of the most commonly accepted groups (Olenellida, Ptychopariida) are paraphyletic. The second problem is taphonomic. The first appearance of a major group often coincides with a major extrinsic change, such as a regressive-transgressive couplet. Does the event initiate the novelty, or simply permit it to be preserved? Does such an event “punctuate” the fossil record, such that earlier, ancestral taxa belonging to the same clade go unrecognised?Trilobites are already paleogeographically diversified when they make their first appearance in the Lower Cambrian. Since trilobites constitute a true clade, this implies an earlier phase of vicariance of dispersal which is not recorded in the rocks. In China, Siberia, North America, and North Africa these first occurrences are in rocks of inshore origin: still earlier trilobites may have had thin cuticles which militated against their being preserved in the highest energy environments where “small shelly” fossils occurred. The groups Olenellida, Redlichiida, Corynexochida, Ptychopariina (?Lichida) appear in the early Cambrian. The earliest polymerids with morphology corresponding to deep water, atheloptic, is latest Lower Cambrian (Atops, Australia): there are many such in the mid-Cambrian.Opinions differ on the classification of Agnostida. Our own view relates Agnostina to Eodiscina, and on this view the early representatives of the clade (Lower Cambrian, China) are inshore compared with later agnostid occurrences, which typify outer shelf to slope. Ordovician agnostids are comparatively rare; the youngest agnostids were not confined to deep water sites.There is good evidence of early occurrences of Odontopleurida, Lichida s.s., Illaenina, Proetida and Phacopida in shallow water deposits. Evidence from Asaphida is more equivocal. Colonisation of deeper water habitats from shallow is rapid, although not achieved at the same time in each group. The scenario is of repeated production of deeper water forms from shelf taxa rather than wholesale movement of clades into that environment. After the demise of other groups in the late Devonian, for example, in the youngest Devonian and Carboniferous proetides radiated into deep water habitats. But the last trilobites of all in the Permian were shallow shelf inhabitants.

The record of cavity-dwelling (coelobiontic) organisms in the Paleozoic

1981 ◽  
Vol 18 (2) ◽  
pp. 181-190 ◽  
Author(s):  
David R. Kobluk
Keyword(s):  
Lower Cambrian ◽  
Community Organization ◽  
Patch Reef ◽  
Early Cambrian ◽  
Marine Environments ◽  
Patch Reefs ◽  
History Of

In modern marine environments coelobiontic (cavity-dwelling) organisms are ubiquitous and abundant. However, little is known of modern coelobionts and even less of their geologic history.The oldest known coelobionts are found in archaeocyathid patch reef cavities from the Lower Cambrian of Nevada and Labrador, where the cavity communities are dominated by algae; foraminifera, brachiopods, pelmatazoans, sponges, archaeocyathids, Bija, Archaeotrypa, and an infauna of burrowers in cavity sediments are accessories in upper Lower Cambrian cavities from the Forteau Formation of Labrador. Earlier cavities in patch reefs from the Poleta Formation of Nevada are much less diverse and are dominated by algae and an infauna of burrowers.From the Lower Cambrian to the present day the history of coelobionts has not been one of major innovation but rather has been conservative. Even as far back as the early Cambrian, coelobiontic communities were similar to their modern counterparts if viewed in terms of community organization and trophic structure.Dans les milieux marins modernes, les organismes coelobiontiques (habitant les cavités) se retrouvent partout et en abondance. Toutefois, on connaît peu de choses sur les coelobiontes modernes et encore moins sur leur histoire géologique.

U-Pb zircon geochronology of late Neoproterozoic–Early Cambrian granitoids in Iran: Implications for paleogeography, magmatism, and exhumation history of Iranian basement

2008 ◽  
Vol 451 (1-4) ◽  
pp. 71-96 ◽  
Author(s):  
Jamshid Hassanzadeh ◽  
Daniel F. Stockli ◽  
Brian K. Horton ◽  
Gary J. Axen ◽  
Lisa D. Stockli ◽  
...  
Keyword(s):  
Early Cambrian ◽  
Zircon Geochronology ◽  
History Of ◽  
Late Neoproterozoic ◽  
Exhumation History

Two Unusual Small Shelly Fossils from the Lower Cambrian of Southeastern Shaanxi Province, China

2014 ◽  
Vol 88 (2) ◽  
pp. 348-358 ◽  
Author(s):  
John L. Moore ◽  
Susannah M. Porter ◽  
Guoxiang Li
Keyword(s):  
Lower Cambrian ◽  
New Genus ◽  
Shaanxi Province ◽  
Early Cambrian ◽  
New Genus And Species ◽  
Small Shelly Fossils ◽  
Dengying Formation ◽  
Phylogenetic Affinities ◽  
Source Of Information ◽  
Made In

Phosphatized and phosphatic small shelly fossils are a major source of information concerning the evolution of animals during the early Cambrian. Although progress has been made in understanding some of these fossils, many remain enigmatic, both with regard to their phylogenetic affinities and the overall morphology of the animal from which isolated sclerites came. Two unusual fossils from the upper lower Cambrian (Qiongzhusian or Atdabanian) Xihaoping Member of the Dengying Formation from Xiaowan, Xixiang County, southeastern Shaanxi Province, China are described herein. The first of these is a cap-shaped fossil we describe asCambroskiadeion xiaowanensenew genus and species. On its concave surface it bears a spine, the base of which is covered with numerous hemispherical verruculae. The long spine indicates that this was a sclerite rather than a univalved shell, although it remains unclear from what sort of animal it came. Similar fossils have been hypothesized to be halkieriid valves; although the rarity of halkieriid sclerites in the present samples argues against this view, it is possible these fossils are part of a similar multi-element skeleton. The second fossil isAcidocharacus longiconusQin and Ding, 1988; it is known only from the Xihaoping Member and consists of a tall spine, often bearing barbs or bumps, attached to a rounded conical base. The base is covered with verruculae similar to those found onCambroskiadeion. The function of these elements, and whether they were internal or external, remains unknown.

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