Resurge deposits associated with the shallow marine early Cambrian Vakkejokk impact, north Sweden

2019 ◽  
Vol 54 (6) ◽  
pp. 1246-1261
Author(s):  
J. Ormö ◽  
P. Minde ◽  
A. T. Nielsen ◽  
C. Alwmark
Keyword(s):  
Early Cambrian ◽  
Shallow Marine ◽  
North Sweden

Arumberiamorph structure in modern microbial mats: implications for Ediacaran palaeobiology

2017 ◽  
Vol 188 (1-2) ◽  
pp. 5 ◽  
Author(s):  
Anton V. Kolesnikov ◽  
Taniel Danelian ◽  
Maxime Gommeaux ◽  
Andrey V. Maslov ◽  
Dmitriy V. Grazhdankin
Keyword(s):  
Microbial Mats ◽  
Biological Response ◽  
Early Cambrian ◽  
Shallow Marine ◽  
Delta Plain ◽  
Microbial Biofilms ◽  
Environmental Perturbations ◽  
The Village ◽  
Globally Distributed ◽  
Marine Basins

In the course of studying modern halotolerant microbial mats in salterns near the village of Kervalet, western France, we observed fanning-out and curved series of macroscopic ridges on the surface of a newly formed biofilm. The structure resembles the late Ediacaran fossil Arumberia which is globally distributed in Australia, Avalonia, Baltica, Siberia and India, always confined to intertidal and delta-plain settings subject to periodic desiccation or fluctuating salinity. Although the origin of the structure observed in modern microbial mats remains enigmatic, wrinkled and rugose variants of microbial biofilms in general exhibit increased levels of resistance to several environmental stresses. By analogy, the fossil Arumberia could be interpreted as a microbial mat morphotype (the “Arumberia” morph) developed in response to environmental perturbations in terminal Ediacaran shallow marine basins. If environmental conditions are likely to be responsible for the formation of Arumberia, it is not that a specific biological community has survived since the Ediacaran – it is that the biological response of microbial communities that manifested itself quite commonly in certain terminal Ediacaran and early Cambrian environments can still be found (seemingly in much more restricted settings) today.

scholarly journals Cambrian stratigraphy of Jordan

GeoArabia ◽  
2014 ◽  
Vol 19 (3) ◽  
pp. 81-134 ◽  
Author(s):  
John H. Powell ◽  
Abdulkader M. Abed ◽  
Yves-Michel Le Nindre
Keyword(s):  
Alluvial Plain ◽  
Early Cambrian ◽  
Shallow Marine ◽  
Braided Rivers ◽  
The North ◽  
Nubian Shield ◽  
Marine Influence ◽  
Uplift And Erosion ◽  
Arabian Nubian Shield ◽  
Arabian Platform

ABSTRACT The lower and middle Cambrian succession (Ram Group) in Jordan is described in lexicon-style format to document an important phase of Earth history following the uplift and erosion of the Arabian-Nubian Shield (Aqaba Complex) during the late Neoproterozoic, and younger, but more localised, intrusive and volcanic/volcaniclastic activity that formed the Araba Complex. The early Cambrian Ram Unconformity (ca. 530 Ma) marks the base of a predominantly fluvial siliciclastic succession derived from rapidly eroding Neoproterozoic (including Ediacaran) basement rocks, but includes a brief, but biostratigraphically significant, sequence of marine siliciclastics and carbonates, the early mid-Cambrian Burj Formation. Rapid uplift and erosion of the granitoid basement (Arabian-Nubian Shield or ANS) resulted in a peneplanation of the Aqaba Complex over millions of years duration (latest Neoproterozoic to Cambrian) in the Southern Desert of Jordan. Early Cambrian pebbly sandstones and locally derived conglomerates (Salib Formation) were deposited on an alluvial plain by high velocity-high discharge, northward flowing (NNE to NNW) braided rivers, characterised by trough cross-bedding and erosive tabular sets. Brief, and rare, marine influence is represented, locally, by thin Skolithos-burrowed sandstones. A regional sea-level rise in the early mid-Cambrian marks a major marine transgressive-regressive cycle and southward thinning carbonate-siliciclastic wedge (Burj Formation) widely present in the subsurface across the Arabian Platform. During deposition of this transgressive marine sequence the palaeoshoreline was oriented WNW-ESE in southern Jordan. The transgressive phase (TST) is represented by tidal-dominated siltstones and fine-grained sandstones (Tayan Member) containing a diverse Cruziana/Rusophycus ichnofaunal assemblage. The overlying carbonate unit (Numayri Member) represents the highstand (HST) and maximum marine flooding surface (MFS), and comprises a carbonate ramp sequence of shelly wackestone, packstone and grainstone with ooids and oncolites, and a diverse shelly fauna including trilobites, brachiopods and hyolithids. A return to regressive tidal-influenced sandstone and siltstone (along with thin carbonates in central Jordan) (Hanneh Member) represents a regressive wedge (RST) deposited in response to renewed uplift of the ANS. Trilobites, represented by the Kingaspis campbelli and Redlichops faunules, suggest a biostratigraphical age of early mid-Cambrian for the carbonate MFS, which equates approximately to the base of the Cambrian Series 3 (Stage 5). This event probably represents the Cambrian marine flooding surface Cm20 (approximate geochronological age of 509 to 505 Ma). South of Feinan, in the Wadi Araba, the carbonates pass laterally to marine sandstone (Abu Khusheiba Sandstone) with extensive Skolithos burrows and Cruziana/Rusophycus traces. Traced southwards (palaeohinterland) the marine influence diminishes, so that the Burj/Abu Khusheiba units are absent in the Southern Desert. Ediacaran intrusives, together with extrusive volcanic and volcaniclastic rocks (Araba Complex) are associated with rifting and half-graben formation in the Feinan-Petra area. This later tectonic activity produced a younger (Ediacaran to early Cambrian), immature palaeotopography, in marked contrast to the Neoproterozoic Aqaba Complex peneplain in the Southern Desert. Consequently, early and mid-Cambrian fluvial and shallow-marine siliciclastics (Salib and Abu Khusheiba formations) onlap progressively onto this immature palaeotopography that was subsequently buried by mid-Cambrian time. Increased basinal subsidence to the north of the Araba Complex ‘high’ provided increased accommodation space that resulted in the deposition of a thick sandstone succession in north Jordan. The Feinan-Petra region seems to have acted as an east-west hinge-line with greater subsidence of the Arabian Platform to the north; similar thickness trends are seen in the Burj and Umm Ishrin formations. Renewed uplift and erosion of the ANS to the south led to deposition of a thick succession of fluvial-dominated sands, again deposited by large-scale braided rivers (Umm Ishrin Formation). Fluvial sedimentation continued through mid to late Cambrian times and also the Ordovician (Disi and Umm Sahm formations), but episodic shallow-marine or estuarine flooding of the low-gradient alluvial plain resulted in colonisation, locally, by arthropods and annelid worms that produced a diverse and abundant Cruziana/Rusophycus/Planolites assemblage of tentative Floian (Arenig) age (upper Disi Formation). Overall the Cambrian to Ordovician Ram Group siliciclastics (Salib-Umm Ishrin-Disi-Umm Sahm formations) show an upward increase in sand maturity from arkose (Salib) to orthoquartzite (Disi); heavy-mineral signatures (ZTR), specifically datable zircons, indicate provenance from a predominantly distant Neoproterozoic granitoid source rock area located to the south (ANS) that was undergoing intensive weathering. However, a small zircon component was derived from older pre-Neoproterozoic rocks, consistent with the general trend in the Levant. The highly permeable Cambrian siliciclastics of Jordan and surrounding countries provide an important regional aquifer, the Ram (formerly Disi) Aquifer. In a suitable setting these reservoir rocks might have potential for hydrocarbon exploration where source rocks of Neoproterozoic, Silurian or Permian age are faulted and in proximity, at depth, in the central Arabian Platform.

Early Cambrian and Older Trace Fossils from the Southern Cordillera of Canada

1972 ◽  
Vol 9 (1) ◽  
pp. 1-17 ◽  
Author(s):  
F. G. Young
Keyword(s):  
British Columbia ◽  
Marine Environment ◽  
Carbonate Rocks ◽  
Trace Fossils ◽  
Trace Fossil ◽  
Older Age ◽  
Early Cambrian ◽  
Shallow Marine ◽  
Sedimentary Environments ◽  
Organic Life

Metazoan trace fossils of Early Cambrian and older age have been found in parts of the Gog, Cariboo, and Miette Groups of eastern British Columbia and western Alberta. Most of them occur in beds immediately below the zones containing the earliest Cambrian trilobites and archaeocyathids. These beds represent a variety of sedimentary environments, including the beach and littoral (Skolithos – facies), and shallow marine (Cruziana – facies) environments in the upper McNaughton Formation of the Gog Group: and a moderately deep marine environment in the Midas Formation of the Cariboo Group. Below these zones evidence of organic life is mainly restricted to stromatolites in carbonate rocks, and simple feeding-burrows in argillaceous silt-stones. A rare, but important trace fossil in this zone is a doubly furrowed trail, which is herein named Didymaulichnus miettensis (gen. et sp. nov.). This fossil indicates that metazoans existed before the Cambrian Period by a span of time represented by the net deposition of up to 2000 m of detrital sediments.

scholarly journals Malongitubus: a possible pterobranch hemichordate from the early Cambrian of South China

2017 ◽  
Vol 92 (1) ◽  
pp. 26-32 ◽  
Author(s):  
Shixue Hu ◽  
Bernd-D. Erdtmann ◽  
Michael Steiner ◽  
Yuandong Zhang ◽  
Fangchen Zhao ◽  
...  
Keyword(s):  
South China ◽  
Organic Material ◽  
Early Cambrian ◽  
Burgess Shale ◽  
Shallow Marine ◽  
Marine Communities ◽  
Mass Occurrence ◽  
Branching Points ◽  
New Material ◽  
Chengjiang Lagerstätte

AbstractMalongitubus kuangshanensis Hu, 2005 from the early Cambrian Chengjiang Lagerstätte of China is redescribed as a pterobranch and provides the best evidence to demonstrate that hemichordates were present as early as Cambrian Stage 3. Interpretation of this taxon as a hemichordate is based on the morphology of the branched colony and the presence of resistant inner threads consistent with the remains of an internal stolon system. The presence of fusellar rings in the colonial tubes cannot be unambiguously proven for Malongitubus, probably due to early decay and later diagenetic replacement of the thin organic material of the tubarium, although weak annulations are still discernible in parts of the tubes. The description of M. kuangshanensis is revised according to new observations of previously reported specimens and recently collected additional new material. Malongitubus appears similar in most features to Dalyia racemata Walcott, 1919 from the Cambrian Stage 5 Burgess Shale, but can be distinguished by the existence of disc-like thickenings at the bases of tubarium branching points in the latter species. Both species occur in rare mass-occurrence layers with preserved fragmentary individuals of different decay stages, with stolon remains preserved as the most durable structures. Benthic pterobranchs may have occurred in some early Cambrian shallow marine communities in dense accumulations and provided firm substrates and shelter for other benthic metazoans as secondary tierers.

Stratigraphy and sedimentology of the Hamill Group in the northern Selkirk Mountains, British Columbia: evidence for latest Proterozoic – Early Cambrian extensional tectonism

1989 ◽  
Vol 26 (3) ◽  
pp. 515-533 ◽  
Author(s):  
William J. Devlin
Keyword(s):  
British Columbia ◽  
Fault Scarp ◽  
Gravity Flow ◽  
Tectonic Activity ◽  
Turbidity Currents ◽  
Early Cambrian ◽  
Shallow Marine ◽  
Sedimentary Characteristics ◽  
Sediment Gravity Flow ◽  
Selkirk Mountains

Three informal stratigraphic divisions are recognized in the uppermost Proterozoic – Lower Cambrian Hamill Group in the northern Selkirk Mountains of British Columbia. These informal divisions include a lower sandstone unit, a greenstone–graded-sandstone unit, and an upper sandstone unit. Both the lower and upper sandstone units display sedimentary characteristics that are uniform along strike and indicate a shallow-marine environment of deposition. As is typical of other exposures of the Hamil Group in southeastern British Columbia, the lower sandstone unit is coarser grained and more poorly sorted than the mature quartz arenites of the upper sandstone unit.The greenstone–graded-sandstone unit is a complex assemblage of mafic metavolcanic rocks and associated sandstone facies. This unit is highly variable along strike but essentially consists of a thick succession of subaqueous extrusive rocks overlain by a variety of sediment gravity-flow deposits. These latter deposits include resedimented conglomerates, debris-flow deposits, and trubidites (deposited from both high- and low-density turbidity currents). Stratigraphic sections of this unit are described in detail from three different localities and are examined in terms of their transport and depositional mechanisms.The stratigraphic succession of the Hamill Group indicates that deposition of the shallow-marine sands of the lower sandstone unit was abruptly interrupted by a period of volcanism, the creation of a paleoslope, and the deposition of a large volume of sediment gravity-flow deposits of the greenstone–graded-sandstone unit. These relations are attributed to an episode of syndepositional normal faulting. The inferred fault(s) could have served as the conduit for the extrusion of the volcanics. Offset along the fault(s), the tilting of fault blocks, and the consequent formation of an unstable slope adjacent to a fault scarp created an environment favorable for deposition of the sediment gravity flows. In general, deposition of proximal, base-of-slope deposits was followed by an aggradational basin-fill phase of sedimentation. With the waning of tectonic activity and the filling of the fault-bounded basin, depositon of shallow-marine sands resumed (the upper sandstone unit). The stratigraphic relations of the Hamill Group in the northern Selkirk Mountains are considered direct evidence for an episode of latest Proterozoic – Early Cambrian extensional tectonism. The evidence for an episode of rift-related tectonism in the northern Selkirk Mountains supports inferences concerning the timing of this event as derived from tectonic subsidence analyses of post-rift strata of the Cordilleran miogeocline.

An early Cambrian shallow-marine ichnofauna from the Puncoviscana Formation of northwest Argentina: the interplay between sophisticated feeding behaviors, matgrounds and sea-level changes

2012 ◽  
Vol 86 (1) ◽  
pp. 7-18 ◽  
Author(s):  
Luis A. Buatois ◽  
María Gabriela Mángano
Keyword(s):  
Microbial Mats ◽  
Trace Fossils ◽  
Cambrian Explosion ◽  
Early Cambrian ◽  
Marine Environments ◽  
Sea Level Changes ◽  
Feeding Behaviors ◽  
Shallow Marine ◽  
Northwest Argentina ◽  
Marine Deposits

An early Cambrian ichnofauna consisting of Helminthoidichnites tenuis, Helminthopsis tenuis, Multina isp., Oldhamia alata, and Pilichnus cf. dichotomus is documented from shallow-marine deposits ranging from the upper offshore to the offshore transition in the Puncoviscana Formation of northwest Argentina. Although the ichnogenus Oldhamia is more common in Cambrian deep-marine environments, this occurrence provides further evidence that it is also present in shallow-marine environments. The burrow network Multina (senior synonym of Olenichnus) is preserved at the base of tempestites, representing the activity of post-storm colonizers. A drowning surface separating offshore-transition deposits below from upper-offshore deposits above contains widespread evidence of trace fossils in direct association with matgrounds. The undermat miners Oldhamia alata and Pilichnus cf. P. dichotomus occur on this surface, revealing exploitation of organic matter in the biomat. Low sediment rate during drowning and paucity of bioturbation by sediment bulldozers may have promoted the establishment of the matground. In comparison with the simpler animal-matground interactions characteristic of the Ediacaran, the combination of Cambrian evolutionary innovations and the presence of microbial mats promoted more sophisticated interactions. Complex feeding trace fossils revealing that systematic undermat mining, as displayed by Oldamia alata and Pilichnus cf. dichotomus, is a product of the Cambrian explosion.

scholarly journals A potential cephalopod from the early Cambrian of eastern Newfoundland, Canada

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Anne Hildenbrand ◽  
Gregor Austermann ◽  
Dirk Fuchs ◽  
Peter Bengtson ◽  
Wolfgang Stinnesbeck
Keyword(s):  
Lower Cambrian ◽  
Early Stage ◽  
Early Cambrian ◽  
Shallow Marine ◽  
Fossil Evidence ◽  
Molecular Studies ◽  
First Occurrence

AbstractAlthough an early Cambrian origin of cephalopods has been suggested by molecular studies, no unequivocal fossil evidence has yet been presented. Septate shells collected from shallow-marine limestone of the lower Cambrian (upper Terreneuvian, c. 522 Ma) Bonavista Formation of southeastern Newfoundland, Canada, are here interpreted as straight, elongate conical cephalopod phragmocones. The material documented here may push the origin of cephalopods back in time by about 30 Ma to an unexpected early stage of the Cambrian biotic radiation of metazoans, i.e. before the first occurrence of euarthropods.

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