Geochronology of the Cambrian: a precise Middle Cambrian U–Pb zircon date from the German margin of West Gondwana

2014 ◽  
Vol 152 (1) ◽  
pp. 28-40 ◽  
Author(s):  
ED LANDING ◽  
GERD GEYER ◽  
ROBERT BUCHWALDT ◽  
SAMUEL A. BOWRING
Keyword(s):  
Isotope Dilution Mass Spectrometry ◽  
Weighted Mean ◽  
Reasonable Estimate ◽  
Middle Cambrian ◽  
East Central ◽  
Volcanic Tuff ◽  
Central Germany ◽  
Upper Cambrian ◽  
New West ◽  
West Gondwana

AbstractA volcanic tuff 1.0 m above the base of the Triebenreuth Formation in the Franconian Forest provides the first precise and biostratigraphically bracketed date within the traditional Middle Cambrian. The first illustration of fossils from the Triebenreuth Formation in this report and their discussion allow a more highly refined correlation within the Middle Cambrian. A weighted mean 206Pb–238U date of 503.14±0.13/0.25/0.59 Ma on zircons from this subaerial pyroclastic tuff was determined by U–Pb chemical abrasion isotope dilution mass spectrometry (CA-TIMS) techniques. At c. 6.0–7.0 Ma younger than the base of the traditional Middle Cambrian in Avalonia, the new West Gondwanan date from east-central Germany suggests that estimates of 500 Ma for the base of the traditional Upper Cambrian and 497 Ma on the base of the Furongian Series may prove to be too ‘old’. Biostratigraphically well-bracketed dates through most of the Middle Cambrian/Series 3 and below the upper Upper Cambrian/upper Furongian Series do not exist. An earlier determined 494.4±3.8 Ma date from the Southwell Group of Tasmania may actually prove to be a reasonable estimate for the age of the base of the traditional Upper Cambrian. Until high precision dates are determined on the base of the traditional Upper Cambrian and base of the Furongian Series, the rates of biotic replacements and geological developments and the durations of biotic zones in the Middle/Series 3 and Upper Cambrian/Furongian Series remain as ‘best guesses’.

scholarly journals Comparison of Tidalites in Siliciclastic, Carbonate, and Mixed Siliciclastic-Carbonate Systems: Examples from Cambrian and Devonian Deposits of East-Central Iran

ISRN Geology ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-21 ◽  
Author(s):  
Hamed Zand-Moghadam ◽  
Reza Moussavi-Harami ◽  
Asadollah Mahboubi ◽  
Hoda Bavi
Keyword(s):  
Central Iran ◽  
Lateral Extension ◽  
Diagnostic Features ◽  
Middle Cambrian ◽  
East Central ◽  
Upper Cambrian ◽  
Architectural Elements ◽  
The North ◽  
Vertical Thickness ◽  
Lithofacies Association

For the comparison of lithofacies in siliciclastic, carbonate, and mixed siliciclastic-carbonate tidal systems, three successions including Top Quartzite (Lower-Middle Cambrian), Deranjal Formation (Upper Cambrian), and Padeha Formation (Lower-Middle Devonian) in the north of Kerman and Tabas regions (SE and E central Iran) were selected and described, respectively. Lithofacies analysis led to identification of 14 lithofacies (Gcm, Gms, Gt, Sp, St, Sh, Sl, Sr, Sm, Se, Sr(Fl), Sr/Fl, Fl(Sr), and Fl) and 4 architectural elements (CH, LA, SB, and FF) in the Top Quartzite, 7 lithofacies (Dim, Dp, Dr, Ds, Dl, Dr/Dl, and Fcl) and 2 architectural elements (CH, CB) in the Deranjal Formation, and 17 lithofacies (Sp, St, Sh, Sl, Sr, Se, Sr(Fl), Sr/Fl, Fl(Sr), Fl, Dr, Ds, Sr/Dl, El, Efm, Efl, and Edl) and 5 architectural elements (CH, LA, SB, FF, and EF) in the Padeha Formation that have been deposited under the influence of tides. The most diagnostic features for comparison of the three tidalite systems are sedimentary structures, textures, and fabrics as well as architectural elements (lithofacies association). The CH element in siliciclastics has the highest vertical thickness and the least lateral extension, while in the carbonate tidalites, it has the least vertical thickness and the most lateral extension compared to in other systems.

scholarly journals The Souss lagerstätte of the Anti-Atlas, Morocco: discovery of the first Cambrian fossil lagerstätte from Africa

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Gerd Geyer ◽  
Ed Landing
Keyword(s):  
South China ◽  
Lower Cambrian ◽  
Northern Slope ◽  
Sea Floor ◽  
Upper Cambrian ◽  
Exceptional Preservation ◽  
West Gondwana ◽  
Regional Correlation ◽  
Animal Remains ◽  
Stratigraphic Interval

AbstractEpisodic low oxygenated conditions on the sea-floor are likely responsible for exceptional preservation of animal remains in the upper Amouslek Formation (lower Cambrian, Stage 3) on the northern slope of the western Anti-Atlas, Morocco. This stratigraphic interval has yielded trilobite, brachiopod, and hyolith fossils with preserved soft parts, including some of the oldest known trilobite guts. The “Souss fossil lagerstätte” (newly proposed designation) represents the first Cambrian fossil lagerstätte in Cambrian strata known from Africa and is one of the oldest trilobite-bearing fossil lagerstätten on Earth. Inter-regional correlation of the Souss fossil lagerstätte in West Gondwana suggests its development during an interval of high eustatic levels recorded by dark shales that occur in informal upper Cambrian Series 2 in Siberia, South China, and East Gondwana.

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.

The Middle–Upper Cambrian Transition in Southeastern Newfoundland, Canada

1975 ◽  
Vol 12 (12) ◽  
pp. 2065-2079 ◽  
Author(s):  
Valdemar Poulsen ◽  
Michael M. Anderson
Keyword(s):  
Basal Part ◽  
Eastern Canada ◽  
Middle Cambrian ◽  
Upper Cambrian ◽  
First Time

The Middle-Upper Cambrian transition in southeastern Newfoundland is shown to be very similar to the transition in Scandinavia and in the English Midlands. The late Middle Cambrian Lejopyge laevigata Zone, which is recorded for the first time from eastern Canada, is contained in the basal part of the Elliott Cove Formation and is conformably overlain by the Upper Cambrian Agnostus pisiformis Zone. The following trilobite species from the Lejopyge laevigata Zone at Manuels River and on Random Island are described: Andrarina costata (Angelin), Paradoxides sp., Lejopyge laevigata (Dalman), and Peronopsis insignis (Wallerius).

scholarly journals Lithostratigraphic and allostratigraphic framework of the Cambrian–Ordovician Potsdam Group and correlations across Early Paleozoic southern Laurentia

2017 ◽  
Vol 54 (5) ◽  
pp. 550-585 ◽  
Author(s):  
David G. Lowe ◽  
R.W.C. Arnott ◽  
Godfrey S. Nowlan ◽  
A.D. McCracken
Keyword(s):  
Climate Change ◽  
Early Paleozoic ◽  
Middle Cambrian ◽  
Shallow Marine ◽  
Upper Cambrian ◽  
Subaerial Exposure ◽  
Marine Sedimentation ◽  
Lower Ordovician ◽  
Fluvial Sedimentation ◽  
Mixed Carbonate

The Potsdam Group is a Cambrian to Lower Ordovician siliciclastic unit that crops out along the southeastern margins of the Ottawa graben. From its base upward, the Potsdam consists of the Ausable, Hannawa Falls, and Keeseville formations. In addition, the Potsdam is subdivided into three allounits: allounit 1 comprises the Ausable and Hannawa Falls, and allounits 2 and 3, respectively, the lower and upper parts of the Keeseville. Allounit 1 records Early to Middle Cambrian syn-rift arkosic fluvial sedimentation (Ausable Formation) with interfingering mudstone, arkose, and dolostone of the marine Altona Member recording transgression of the easternmost part of the Ottawa graben. Rift sedimentation was followed by a Middle Cambrian climate change resulting in local quartzose aeolian sedimentation (Hannawa Falls Formation). Allounit 1 sedimentation termination coincided with latest(?) Middle Cambrian tectonic reactivation of parts of the Ottawa graben. Allounit 2 (lower Keeseville) records mainly Upper Cambrian quartzose fluvial sedimentation, with transgression of the northern Ottawa graben resulting in deposition of mixed carbonate–siliciclastic strata of the marine Rivière Aux Outardes Member. Sedimentation was then terminated by an earliest Ordovician regression and unconformity development. Allounit 3 (upper Keeseville) records diachronous transgression across the Ottawa graben that by the Arenigian culminated in mixed carbonate–siliciclastic, shallow marine sedimentation (Theresa Formation). The contact separating the Potsdam Group and Theresa Formation is conformable, except locally in parts of the northern Ottawa graben where the presence of localized islands and (or) coastal salients resulted in subaerial exposure and erosion of the uppermost Potsdam strata, and accordingly unconformity development.

Archaeocyathids: Morphology and Affinity

1983 ◽  
Vol 7 ◽  
pp. 178-190
Author(s):  
Francoise Debrenne
Keyword(s):  
Calcium Carbonate ◽  
Marine Organisms ◽  
Early Cambrian ◽  
Middle Cambrian ◽  
Upper Cambrian ◽  
The Family ◽  
Reef Environments

The Archaeocyatha were marine organisms developing mineral skeletons and using calcium carbonate for this purpose. Remains of their cups are found in carbonate shelfs and reef environments of the Early Cambrian seas. Few representatives of the family Archaeocyathidae are found through the Middle Cambrian to the Upper Cambrian (Debrenne, Rozanov and Webers, in press).

Cambrian and Ordovician linguliform brachiopods from the Shallow Bay Formation (Cow Head Group), western Newfoundland

2001 ◽  
Vol 75 (2) ◽  
pp. 241-260 ◽  
Author(s):  
Sean P. Robson ◽  
Brian R. Pratt
Keyword(s):  
New Species ◽  
Continental Slope ◽  
Head Group ◽  
Lower Paleozoic ◽  
Middle Cambrian ◽  
Middle Ordovician ◽  
Upper Cambrian ◽  
Three New Species ◽  
Brachiopod Fauna ◽  
Shallow Bay

Linguliform brachiopods were recovered from the Upper Cambrian Downes Point Member (lower Sunwaptan) and from the Middle Ordovician Factory Cove Member (Arenig) of the Shallow Bay Formation, Cow Head Group, of western Newfoundland. These rocks are a series of Middle Cambrian to Middle Ordovician conglomerates, lime mudstones, and shales that formed a sediment apron at the base of the lower Paleozoic continental slope of Laurentia. The linguliform brachiopod fauna consists of sixteen species assigned to twelve genera. Three new species are described: Picnotreta lophocracenta, Neotreta humberensis, and Siphonotretella parvaducta.

Asynchronous trilobite extinctions at the early to middle Cambrian transition

Geology ◽  
2020 ◽  
Vol 48 (5) ◽  
pp. 441-445 ◽  
Author(s):  
F.A. Sundberg ◽  
K.E. Karlstrom ◽  
G. Geyer ◽  
J.R. Foster ◽  
J.W. Hagadorn ◽  
...  
Keyword(s):  
Critical Time ◽  
Data Sets ◽  
Early Cambrian ◽  
Earth System ◽  
Middle Cambrian ◽  
West Gondwana ◽  
Paleoclimatic Data ◽  
First Time ◽  
Age Constraints ◽  
Prior Models

Abstract Trilobites appeared and diversified rapidly in the Cambrian, but it is debated as to whether their radiations and extinctions were globally synchronous or geographically restricted and diachronous. The end of the early Cambrian is a classic example—it has traditionally been defined by the extinction of olenellid and redlichiid trilobites and the appearance of paradoxidid trilobites. Here we integrate the global biostratigraphy of these three trilobite groups with high-precision tuff and tandem detrital zircon U-Pb age constraints to falsify prior models for global synchronicity of these events. For the first time, we demonstrate that olenellid trilobites in Laurentia went extinct at least 3 Ma after the first appearance of paradoxidids in Avalonia and West Gondwana (ca. 509 Ma). They also disappeared before the extinction of redlichiids and prior to the base of the Miaolingian at ca. 506 Ma in South China. This indicates that these three trilobite groups (paradoxidids, olenellids, and redlichiids) and their associated biotas overlapped in time for nearly 40% of Cambrian Epoch 2, Age 4. Implications of this chronological overlap are: (1) trilobite transitions were progressive and geographically mediated rather than globally synchronous; and (2) paleontological databases underestimate the diversity of the early Cambrian. This ∼3 Ma diachroneity, at a critical time in the early evolution of animals, also impacts chemostratigraphic and paleoclimatic data sets that are tied to trilobite biostratigraphy and that collectively underpin our understanding of the Cambrian Earth system.

Morphological assessment of the earliest paradoxidid trilobites (Cambrian Series 3) from Morocco and Spain

2017 ◽  
Vol 155 (7) ◽  
pp. 1566-1595 ◽  
Author(s):  
J. JAVIER ÁLVARO ◽  
JORGE ESTEVE ◽  
SAMUEL ZAMORA
Keyword(s):  
New Species ◽  
Statistical Analysis ◽  
Iberian Peninsula ◽  
Linear Measurement ◽  
Geometric Morphometric ◽  
Middle Cambrian ◽  
West Gondwana ◽  
Regional Correlation ◽  
Definition Of ◽  
Morphological Assessment

AbstractA Cambrian immigration event of paradoxidid trilobites has traditionally marked some regional lower–middle Cambrian boundaries in the Acado-Baltic subprovince (including Baltica and the Mediterranean and Avalonian margins of West Gondwana). The earliest paradoxidine species in Morocco and the Iberian Peninsula have been used as a chronostratigraphic link to support the definition of a common base for the Cambrian Series 3, but recent studies have proposed new species without revising previously established ones. This paper offers a morphological statistical analysis based on both linear measurement and landmark-based geometric morphometric approaches performed on the earliest paradoxinine trilobites sampled in the Anti-Atlas (Morocco) and the Iberian Chains (Spain). As a result, the diagnosis of Acadoparadoxides mureroensis is emended and several species recently erected in Morocco (A. cf. mureroensis, A. levisettii, A. ovatopyge and A. pampalius) are suggested as synonyms of A. mureroensis until 3D statistical analyses are available based on material preserved on carbonate or silica nodules. The first appearance of A. mureroensis in both areas can be provisionally used for regional correlation until homotaxic tests are checked.

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