04145nas a2200265 4500008004100000022001300041245020300054210007300257260001600330300001100346490000800357520322900365653001303594653003003607653001303637653001403650653001503664653001803679100001603697700001903713700001903732700001603751700002503767856008703792 2022 eng d a0012825200aGreater Avalonia—latest Ediacaran–Ordovician “peribaltic” terrane bounded by continental margin prisms (“Gander,” Harlech Dome, Meguma): Review, tectonic implications, and paleogeography0 aGreater Avalonia—latest Ediacaran–Ordovician peribaltic terrane cJan-11-2021 a1038630 v2243 a
Distinctive uppermost Ediacaran–Ordovician rocks (Avalonian overstep sequence) were key in definition of Avalonia, which comprises large areas of the NE Appalachians and the Caledonian and Variscan mountains (Britain and western Europe). This siliciclastic-dominated cover succession unconformably overlies a Neoproterozoic pre-Avalonian basement collage (arc, continental, oceanic fragments; Gwna-type melanges [now Rhode Island–Maritime Canada–North Wales]). Rather than an arc–transform transition, our new model proposes that the Avalonian basement was amalgamated after inferred late Ediacaran ridge-trench collision that initiated the northerly–southerly trending Avalonian transform fault (Atf, new). Avalonia is commonly regarded as originating as an arc marginal to Gondwana in the early Paleozoic and detached only in the Ordovician. We review multiple lines of evidence that show it was an insular microcontinent; this require revisions of Ediacaran–early Paleozoic paleogeography and plate tectonics models. Detrital zircon isotopic data show an Avalonia–Baltica link to the Neoproterozoic Timanian orogen, with Avalonia a peribaltic, not perigondwanan, terrane. The Avalonian basement detached from Baltica and rotated parallel to the Atf, with its origin similar to the modern Scotia Sea plate (i.e., North Scotia Ridge and transform) by accumulation of Neoproterozoic arc and continental fragments on the transform. Deposition of the cover sequence beginning ca. 552 Ma in pull-apart basins on the basement marked origin of the Avalonia ribbon-microcontinent. The cover succession, with ten unconformity-bounded depositional sequences, extends for ca. 5000 km (eastern Massachusetts–Silesia). Avalonia is bounded on its NW and SE by siliciclastic rocks (i.e., Gander and Meguma belts with an Ordovician arc in Gander) that were continental margin prisms coeval with the overstep sequence. Endemic Avalonian lower Lower Cambrian (Terraneuvian–lower Series 2, ca. 538–510 Ma) faunas, dropstones, absence of archaeocyaths, and minor shallow-water carbonates suggest an isolated location at ≥50° S. Only in the latest Early Cambrian (ca. 506 Ma) do Avalonian faunas show NW African, “Gondwanan” affinities with Avalonia-Gondwana convergence on the Atf. A longer (ca. 28 Ma, Middle Cambrian–Tremadocian) faunal similarity links temperate Avalonia and Baltica as terranes on the same plate. An insular Avalonia is consistent with a Middle Cambrian, ca. 49° S latitude (Cape Breton Island) location—its only reliable Cambrian paleomagnetic datum. Meso- and Paleoproterozoic zircons do not record nearby West Gondwana margins, but were eroded from Avalonian basement. Purported “Ganderian” plutonic zircons and whole rock signatures in SW New Brunswick indicate heterogeneity between Avalonian basement blocks, not a “Ganderia” affinity before a purported transfer of parts of Avalonia to “Ganderia.” Coeval extensional and collisional igneous rocks along the Atf is seen in regions of transform faulting and do not allow reference of Avalonian areas to “Ganderia.” Avalonia should not be shown as part of West Gondwana or separating from it in the Ordovician.
10aAvalonia10aAvalonian transform fault10aCambrian10aEdiacaran10aOrdovician10aWest Gondwana1 aLanding, E.1 aKeppie, Duncan1 aKeppie, Fraser1 aGeyer, Gerd1 aWestrop, Stephen, R. uhttps://www.sciencedirect.com/science/article/abs/pii/S0012825221003640?via%3Dihub02612nas a2200301 4500008004100000022001400041245025200055210006900307260001200376300001300388490000700401520158200408653001301990653001302003653003002016653001802046653001002064653001102074653002002085653001902105653002602124653001402150653001802164653002502182100001602207700001602223856007102239 2021 eng d a1042-094000aTrace fossils, depositional context, and paleogeography of the upper Tal Group (upper lower Cambrian), Lesser Himalaya, India: a Gondwanan succession with no affinities to the Avalonia microcontinent – discussion of paper by Singh et al. (2019)0 aTrace fossils depositional context and paleogeography of the upp c11/2020 a143-156 0 v283 aTerminal Ediacaran–late early Cambrian deposition, faunas and passive margin evolution of the north Indian margin are recorded in the Nigali Dhar syncline succession. Restudy of the upper Tal Group (upper lower Cambrian Koti Dhaman Formation, KDF) ichnofauna from the Khud-Drabil section reduces it to 18 confidently named forms. The lower KDF (Lower Quartzite Member) Cruziana-Rusophycus assemblage is in subtidal (not intertidal) sandsheet facies. The overlying black Shale Member (SM) records trans-East Gondwanan deepening, not intertidal facies, in the Palaeolenus Zone. The SM, with low diversity Planolites-Palaeophycus assemblage, is overlain by subtidal (not intertidal) sandsheet facies of the middle KDF (Arkosic Sandstone Member, ASM) with shallow burrowers and furrowers (Gordia marina assemblage, new; Cruziana ichnofacies). KDF faunas with Cruziana and Rusophycus are similar to coeval, shallow marine associations elsewhere in Gondwana and NW Laurentia. Interpretation of a second KDF section 20 km from Khud-Drabil has confused an understanding of Lesser Himalaya geologic evolution as it claims Ordovician Cruziana species in the ASM and an angular SM–ASM unconformity caused by the Cambrian–Ordovician boundary Kurgiakh orogeny. However, upper lower Cambrian microfaunas occur in and above the ASM, while the angular SM–ASM unconformity is consistent with submarine sliding. KDF-type ichnofaunas do not show a tropical location of Avalonia, which has the distinctive lithofacies and biotas of a high-latitude continent unrelated to Gondwana.
10aAvalonia10aCambrian10adepositional environments10aEast Gondwana10aIndia10aIsrael10aLesser Himalaya10apaleogeography10asequence stratigraphy10aTal Group10atrace fossils10aupper Lower Cambrian1 aLanding, E.1 aGeyer, Gerd uhttps://www.tandfonline.com/doi/full/10.1080/10420940.2020.184345703029nas a2200241 4500008004100000022001300041245014900054210006900203260001200272300001100284490000800295520225200303653002102555653002002576653001302596653002502609653002202634653001402656653001802670100001602688700001602704856006702720 2020 eng d a1464343X00aCambrian deposition in northwestern Africa: Relationship of Tamlelt massif (Moroccan‒Algerian border region) succession to the Moroccan Meseta0 aCambrian deposition in northwestern Africa Relationship of Tamle c03/2020 a1037720 v1653 aThe Tamlelt massif is physiographically grouped as a continuation of the easternmost High Atlas. However, re-examination of the Tamlelt's Cambrian litho- and biostratigraphy shows a depositional history that differs from that of the Souss Basin to the southwest (i.e., west-central High Atlas and eastern Anti-Atlas of Morocco). Our re-examination leads to recommendations on the local stratigraphic succession and nomenclature. Trilobites from the Al Hamrat Formation in the Tamlelt massif indicate late early Cambrian (upper Epoch 2) siliciclastics overlying shallow marine, carbonate-rich deposits (Jbel Menhouhou Formation) similar to and coeval with those of the distant western Anti-Atlas region but older than and lithologically distinct from fluviatile siliciclastics (Epoch 3) in the nearby eastern Anti-Atlas. The Jbel Menhouhou carbonates unconformably overlie probable terminal Proterozoic volcanics and clastics of the Bou Kaïs Formation (new) and are overlain by shales and arenites of the upper Kheneg El Kahal Group, which features a Cambrian Stage 4 regressive half-cycle. Regional differences in lithofacies disappear in the early Miaolingian with relatively monotonous, mudstone-rich facies in the Tamlelt massif area (Batene El Jdari Formation) comparable to those of the Jbel Wawrmast Formation of the west-central High Atlas and central‒eastern Anti-Atlas. Probable early late Cambrian brachiopods from siliciclastic rocks of the Tamlelt area indicate a later Cambrian depositional history similar to that of the Anti-Atlas and perhaps Moroccan Meseta. The distinctiveness of the upper lower Cambrian deposits of the Souss Basin from those of the Tamlelt massif apparently reflects a depositional framework independent from other regions of the Atlas ranges, and suggests the Tamlelt region was confluent with the Meseta basin to the northwest. Known trilobites permit precise age assignments through the Tamlelt succession and include species (or forms) which contribute to a refined correlation within West Gondwana and improve West Gondwana‒Baltica correlation. The new trilobite species Saukianda? (Saukianda?) dresnayi is proposed.
New investigations of the Cambrian in the Franconian Forest region lead to a revision of the lithostratigraphic succession into seven units: Rauschbach Unit, Tiefenbach Formation, Tannenknock Formation (with Galgenberg and Wildenstein members), Triebenreuth Formation, Lippertsgrün Formation and Bergleshof Formation, with partly revised stratigraphical ranges and lithological characteristics. The succession indicates a fairly complete succession from Cambrian Series 2 (late early Cambrian) through the end of the Miaolingian, with gaps being a result of incomplete exposure and structural complexity rather than distinct hiatuses. New finds expand the known fossil record and provide additional data for reconstructing biogeographical relationships and depositional environments. These features indicate shallow marine conditions throughout the Cambrian with characteristics typical for West Gondwanan shelf areas. In particular, strong similarities to the Moroccan Atlas regions are indicated. Additional information on volcanic activity from middle Cambrian through Tremadocian times provides clues for crustal extension that affected the depositional setting in this region. Stratigraphy, depositional environments and facies distribution all suggest reinterpretation of earlier geotectonical models used to interpret the history of the Franconian Forest area in the Saxothuringian Belt.
10aCambrian10achronostratigraphy10adepositional environments10alithostratigraphy10avolcanism10aWest Gondwana1 aGeyer, G.1 aLanding, E.1 aHöhn, S.1 aLinnemann, U.1 aMeier, S.1 aServais, T.1 aWotte, T.1 aHerbig, H., -G. uhttps://dx.doi.org/10.1127/nos/2019/049503100nas a2200277 4500008004100000022001300041245015600054210006900210260001200279300001200291490000800303520225000311653001302561653001302574653002002587653001402607653001402621653001502635100001602650700002202666700001402688700001902702700001902721700001602740856006602756 2018 eng d a0012825200aEarly evolution of colonial animals (Ediacaran Evolutionary Radiation–Cambrian Evolutionary Radiation–Great Ordovician Biodiversification Interval)0 aEarly evolution of colonial animals Ediacaran Evolutionary Radia c01/2018 a105-1350 v1783 aRe-evaluation of eumetazoan modular coloniality gives a new perspective to Ediacaran–Ordovician animal diversification. Highly integrated eumetazoan colonies (porpitids [“chondrophorines”], pennatulacean octocorals, anthozoans) prove to be unknown in the Ediacaran. Ediacaran Evolutionary Radiation (EER, new term) fossils include macroscopic and multicellular remains that cannot be compellingly related to any modern group. Claims of eumetazoan coloniality in the Ediacaran are questionable. The subsequent Cambrian Evolutionary Radiation (CER, terminal Ediacaran–late early Cambrian) records appearance and diversification of deep burrowers and a relatively abrupt development of biomineralization. The CER began in a transition zone that spans the Ediacaran–Cambrian boundary and includes the final few million years of the Ediacaran. The early CER has pseudocolonial(?) Corumbella that may be related to some Phanerozoic taxa (conulariids) and records appearance of the first macroscopic biomineralised organisms (Cloudina, Namacalathus, Namapoikea), which may not be eumetazoans. Modular eumetazoans dominate and define many Ordovician and younger habitats (coral, bryozoan, sabellitid reefs; pelagic larvaceans, salps, early–middle Palaeozoic graptolites), but eumetazoan coloniality largely “missed” the EER and CER. All purported Ediacaran–Ordovician porpitids (“chondophorines”) and pennatulaceans are not colonial eumetazoans. Only in the late early Cambrian (late CER) or early middle Cambrian do a few modular colonial eumetazoans first occur as fossils. These include Sphenothallus (available evidence precludes Torellella coloniality), some corals (colonial “coralomorphs”), and lower middle Cambrian graptolithoids. Modular eumetazoan colonies (corals, graptolithoids) in the late early and early middle Cambrian (late Epoch 2–early Epoch 3) and appearance of mid-water predators (cephalopods, euconodonts) and bryozoans in the late Cambrian–earliest Ordovician (late Furongian–early Tremadocian) are the root for the Great Ordovician Biodiversification Interval (GOBI, new term) and diverse later Phanerozoic communities.
10aCambrian10aColonies10aEarly evolution10aEdiacaran10aEumetazoa10aOrdovician1 aLanding, E.1 aAntcliffe, J., B.1 aGeyer, G.1 aKouchinsky, A.1 aBowser, S., S.1 aAndreas, A. uhttp://linkinghub.elsevier.com/retrieve/pii/S001282521730523803014nas a2200301 4500008004100000022001300041245007300054210006900127260001600196300001200212490000700224520218800231653001102419653001302430653002002443653001302463653001102476653001202487653001702499653001702516100002202533700002102555700001602576700002102592700002302613700001902636856005702655 2017 eng d a0567792000aTerreneuvian Stratigraphy and Faunas from the Anabar Uplift, Siberia0 aTerreneuvian Stratigraphy and Faunas from the Anabar Uplift Sibe cMay-31-2017 a311-4400 v623 aAssemblages of mineralized skeletal fossils are described from limestone rocks of the lower Cambrian Nemakit-Daldyn, Medvezhya, Kugda-Yuryakh, Manykay, and lower Emyaksin formations exposed on the western and eastern flanks of the Anabar Uplift of the northern Siberian Platform. The skeletal fossil assemblages consist mainly of anabaritids, molluscs, and hyoliths, and also contain other taxa such as Blastulospongia, Chancelloria, Fomitchella, Hyolithellus, Platysolenites, Protohertzina, and Tianzhushanella. The first tianzhushanellids from Siberia, including Tianzhushanella tolli sp. nov., are described. The morphological variation of Protohertzina anabarica and Anabarites trisulcatus from their type locality is documented. Prominent longitudinal keels in the anabaritid Selindeochrea tripartita are demonstrated. Among the earliest molluscs from the Nemakit-Daldyn Formation, Purella and Yunnanopleura are interpreted as shelly parts of the same species. Fibrous microstructure of the outer layer and a wrinkled inner layer of mineralised cuticle in the organophosphatic sclerites of Fomitchella are reported. A siliceous composition of the globular fossil Blastulospongia is reported herein and a possible protistan affinity similar to Platysolenites is discussed. New carbon isotope data facilitate correlation both across the Anabar Uplift and with the Terreneuvian Series of the IUGS chronostratigraphical scheme for the Cambrian System. The base of Cambrian Stage 2 is provisionally placed herein within the Fortunian‒Cambrian Stage 2 transitional interval bracketed by the lowest appearance of Watsonella crosbyi and by a slightly higher horizon at the peak of carbon isotope excursion Iʹ from western flank of the Anabar Uplift. Correlation across the Siberian Platform of the fossiliferous Medvezhya and lower Emyaksin formations showing δ13Ccarb excursion Iʹ with the upper Sukharikha Formation containing excursion 5p and upper Ust’-Yudoma Formation containing excursion I is supported herein.
10aAnabar10aCambrian10aCarbon isotopes10aMollusca10aRussia10aSiberia10astratigraphy10aTerreneuvian1 aKouchinsky, Artem1 aBengtson, Stefan1 aLanding, E.1 aSteiner, Michael1 aVendrasco, Michael1 aZiegler, Karen uhttp://www.app.pan.pl/article/item/app002892016.html02755nas a2200217 4500008004100000022001400041245019900055210006900254260001200323300001400335490000800349520200400357653001402361653002002375653001302395653001402408653001602422100001802438700001602456856006502472 2017 eng d a0016-756800aThe agnostoid arthropod Lotagnostus Whitehouse, 1936 (late Cambrian; Furongian) from Avalonian Cape Breton Island (Nova Scotia, Canada) and its significance for international correlationAbstract0 aagnostoid arthropod Lotagnostus Whitehouse 1936 late Cambrian Fu c07/2016 a1001-10210 v1543 aNew and archival collections from the Chelsey Drive Group of the Avalon terrane of Cape Breton Island, Nova Scotia, Canada, yield late Cambrian trilobites and agnostoid arthropods with full convexity that contrast with compacted, often deformed material from shale and slate typical of Avalonian Britain. Four species of the agnostoid Lotagnostus form a stratigraphic succession in the upper Furongian (Ctenopyge tumida–Parabolina lobata zones). Two species, L. ponepunctus (Matthew, 1901) and L. germanus (Matthew, 1901) are previously named; L. salteri and L. matthewi are new. Lotagnostus trisectus (Salter, 1864), the type species of the genus, is restricted to compacted material from its type area in Malvern, England. Lotagnostus americanus (Billings, 1860) has been proposed as a globally appropriate index for the base of ‘Stage 10’ of the Cambrian. All four species from Avalonian Canada are differentiated clearly from L. americanus in its type area in Laurentian North America (i.e., from debris flow blocks in Taconian Quebec). In our view, putative occurrences of L. americanus from other Cambrian continents record very different species. Lotagnostus americanus cannot be recognized worldwide, and other taxa should be sought to define the base of Stage 10, such as the conodont Eoconodontus notchhpeakensis.
10aAgnostida10aBiostratigraphy10aCambrian10aFurongian10aLotagnostus1 aWestrop, S.R.1 aLanding, E. uhttp://www.journals.cambridge.org/abstract_S001675681600057100702nas a2200205 4500008004100000245017300041210006900214300001200283490000800295653001300303653001300316653001300329653002300342653001200365653001900377653001900396100001600415700002000431856004500451 2015 eng d00aLate Cambrian (middle Furongian) Shallow-Marine Dysoxic Mudstone with Calcrete and Brachiopod–Olenid–Lotagnostus Faunas in Avalonian Cape Breton Island, Nova Scotia0 aLate Cambrian middle Furongian ShallowMarine Dysoxic Mudstone wi a973-9920 v15210aAvalonia10acalcrete10aCambrian10aCape Breton Island10aeustasy10amarine dysoxia10aupper Cambrian1 aLanding, E.1 aWestrop, S., R. uhttp://doi.org/10.1017/S001675681400079X02593nas a2200229 4500008004100000245011500041210006900156300001000225490001200235520190900247653001502156653001102171653001302182653001602195653002202211653001402233653001702247653001702264100001602281700001502297856005102312 2012 eng d00aCephalopod Ancestry and Ecology of the Hyolith 'Allatheca' degeeri s.l. in the Cambrian Evolutionary Radiation0 aCephalopod Ancestry and Ecology of the Hyolith Allatheca degeeri a21-300 v353-3553 aPyritized, elongate, conical conchs of “Allatheca” degeeri s.l. are common in dysoxic, dark gray mudstone intervals in the Early Cambrian (upper Terreneuvian–Series 2 boundary interval) Cuslett Formation at Keels, eastern Newfoundland. Wave-oriented, horizontal specimens are most abundant in this cool-water, high latitude, off-shore shelf facies of the Early Palaeozoic Avalon microcontinent. Based on conch morphology, shell microstructure, and the operculum, the species is an orthothecid hyolith. Comparison with the sizes of the early shells of planktic gastropods indicates a non-planktic life mode of “A.” degeeri s.l. hatchlings, although buoyancy calculations show that small juveniles with septate conchs to ca. 17 mm long could have been nektic/planktic. If smaller “A.” degeeri s.l. individuals had a non-benthic mode of life, they and pseudoconodonts were the oldest skeletalized pelagic/nektic animals in the Cambrian Evolutionary Radiation. Most “A.” degeeri s.l. conchs at Keels are horizontally embedded and show a bimodal, wave-determined orientation, but about 10% of the large conchs are vertically embedded with their aperture down. As larger shells were not neutrally buoyant, the vertical orientations of about 10% of the conchs suggests an infaunal, likely detritivore, life mode suggestive of a scaphopod. Available morphologic and taphonomic evidence suggests that the vertically embedded conchs are in situ remains of dead benthic animals that colonized the bottom in better oxygenated intervals. Based on the current knowledge of Early Palaeozoic hyolith and cephalopod larval and adult morphologies, existing hypotheses of a planktic origin of cephalopods from hyolith ancestors are evaluated, and no evidence for such an evolutionary relationship is concluded to exist.
10aAutecology10aAvalon10aCambrian10aCephalopoda10aCuslett Formation10aEvolution10aNewfoundland10aOrthothecids1 aLanding, E.1 aKroger, B. uhttp://dx.doi.org/10.1016/j.palaeo.2012.06.02302670nas a2200181 4500008004100000245013400041210006900175300001200244490001200256520206300268653001602331653001302347653002402360653002202384653001502406100001602421856005102437 2012 eng d00aTime-specific Black Mudstones and Global Hyperwarming on the Cambrian-Ordovician Slope and Shelf of the Laurentia Palaeocontinent0 aTimespecific Black Mudstones and Global Hyperwarming on the Camb a256-2720 v367-3683 aThe Early Paleozoic featured nine intervals of strong expansion of an upper slope, dysoxic/anoxic (d/a) water mass with eustatic rise or epeirogenic transgression. Strong expansion of this d/a water mass led to deposition of time-specific, macroscale alternations of dark grey-black mudstone within oxic, green to red mudstone on the middle–lower slope. This d/a facies even onlapped warm- (carbonate) and cool-water (siliciclastic) shelves. As in the Mesozoic, d/a muds were deposited in shallow water, perhaps tens of metres deep, with sea-level rise. These nine d/a macroscale alternations correspond to intervals of “global hyperwarming”—times of very intense greenhouse conditions that resulted from a feedback initiated by higher insolation and heat storage as shallow seas onlap tropical palaeocontinents. Warm epeiric seas heated the ocean, and thermal expansion accelerated eustatic rise. Ever more extensive epeiric seas heightened oceanic and global temperature as heat storage capacity increased. Deep ocean circulation intensity fell below that of a greenhouse interval and lead to d/a deposition low on the slope and on the platforms to provide the signature of global hyperwarming. Global hyperwarming differs from a hothouse interval as it does not require CO2 input from large igneous provinces to produce high temperatures and never shows deep-sea anoxia. Late Ordovician and Late Devonian black mudstones that cover much of Laurentia record epeirogenic transgressions that led to global hyperwarming, and suggest that cold water upwelling or plant terrestrialisation had nothing to do with epeiric sea anoxia. Global hyperwarming reduced oxygen solubility in these seas, and erosion of orogens produced muddy water that limited light penetration and promoted shallow-water anoxia. The global hyperwarming hypothesis means that relative eustatic and epeirogenic sea levels complement the effect of global pCO2 on climate, and sea level must also be regarded as a primary driver of Phanerozoic climate.
10aBlack shale10aCambrian10aGlobal hyperwarming10aOcean oxygenation10aOrdovician1 aLanding, E. uhttp://dx.doi.org/10.1016/j.palaeo.2011.09.00502511nas a2200229 4500008004100000245015100041210006900192300001200261490000700273520179100280653001502071653001302086653001402099653001902113653002002132653001802152653000902170100001602179700002002195700001902215856004702234 2011 eng d00aThe Lawsonian Stage - the Eoconodontus Notchpeakensis FAD and HERB Carbon Isotope Excursion Define a Globally Correlatable Terminal Cambrian Stage0 aLawsonian Stage the Eoconodontus Notchpeakensis FAD and HERB Car a621-6400 v863 aThe best definition for the base of the terminal Cambrian (Stage 10) is the conodont Eoconodontus notchpeakensis FAD ± onset of the HERB carbon isotope excursion. These horizons allow precise intercontinental correlations in deep marine to peritidal facies. The agnostoid Lotagnostus americanus (Billings, 1860) FAD has been suggested as a Stage 10 base, but restudy of types and typotypes shows that the species occurs only in Late Cambrian (Sunwaptan) debris flow boulders in Quebec (Westrop et al., this volume). Non-Quebec reports of "L. americanus" are an amalgum of small samples of often poorly documented specimens with effaced–highly furrowed cephala and pygidia and with or without a highly trisected pygidial posteroaxis. Many of these occurrences have local species names, but no evidence suggests that they record intraspecific variation of a globally distributed taxon. They are not synonyms of L. americanus. Lotagnostus, largely a dysoxic form, does not allow precise correlation into oxygenated platform facies. Another proposal used the conodont Cordylodus andresi FAD as a Stage 10 base, but other work shows this FAD is diachronous. An unrealistic approach to L. americanus’ systematics and the correlation uncertainty of C. andresi are overcome by defining a Stage 10 base at the globally recognizable E. notchpeakensis FAD, with the C. andresi FAD a useful proxy on cool-water continents. The "Lawsonian Stage", named for Lawson Cove in western Utah, has a basal GSSP at the E. notchpeakensis FAD and replaces informal Stage 10. The Lawsonian, ~150 m-thick in western Utah, underlies the basal Ordovician Iapetognathus Zone.
10aagnostoids10aCambrian10aconodonts10aHERB excursion10aLawsonian Stage10aUnited States10aUtah1 aLanding, E.1 aWestrop, S., R.1 aAdrian, J., M. uhttp://dx.doi.org/10.3140/bull.geosci.125102609nas a2200241 4500008004100000245017800041210006900219300001200288490000800300520179300308653002502101653001302126653002802139653001502167653001502182653001202197653002402209653001802233653002602251100001602277700002302293856005102316 2010 eng d00aFirst Evidence for Cambrian Glaciation Provided by Sections in Avalonian New Brunswick and Ireland--Additional Data for Avalon-Gondwana Separation by the Earliest Palaeozoic0 aFirst Evidence for Cambrian Glaciation Provided by Sections in A a174-1850 v2853 aThe first evidence for Cambrian glaciation is provided by two successions on the Avalon microcontinent. The middle lowest Cambrian (middle Terreneuvian Series and Fortunian Stage–Stage 2 boundary interval) has an incised sequence boundary overlain by a fluvial lowstand facies and higher, olive green, marine mudstone on Hanford Brook, southern New Brunswick. This succession in the lower Mystery Lake Member of the Chapel Island Formation may be related to melting of an ice sheet in Avalon. The evidence for this interpretation is a muddy diamictite with outsized (up to 10 cm in diameter), Proterozoic marble and basalt clasts that penetrated overlying laminae in the marine mudstone. That eustatic rise was associated with the mudstone deposition is suggested by an approximately coeval rise that deposited sediments with Watsonella crosbyi Zone fossils 650 km away in Avalonian eastern Newfoundland. A sea-level rise within the Watsonella crosbyi Chron, at ca. 535 Ma, may correspond to a unnamed negative 13C excursion younger than the basal Cambrian excursion (BACE) and the ZHUCE excursion in Stage 2 of the upper Terreneuvian Series. Cambrian dropstones are now also recognized on the northern (Gander) margin of Avalon in continental slope–rise sedimentary rocks in southeast Ireland. Although their age (Early–Middle Cambrian) is poorly constrained, dropstones in the Booley Bay Formation provide additional evidence for Cambrian glaciation on the Avalon microcontinent. Besides providing the first evidence of Cambrian glaciation, these dropstone deposits emphasize that Avalon was not part of or even latitudinally close to the terminal Ediacaran–Cambrian, tropical carbonate platform successions of West Gondwana.
10aBooley Bay Formation10aCambrian10aChapel Island Formation10aDiamictite10aGlaciation10aIreland10aMystery Lake Member10aNew Brunswick10asequence stratigraphy1 aLanding, E.1 aMacGabhann, B., A. uhttp://dx.doi.org/10.1016/j.palaeo.2009.11.00902509nas a2200229 4500008004100000245014100041210006900182300001200251490000800263520178500271653002102056653001302077653001502090653001402105653002202119653002602141653001502167100001602182700001402198700001902212856004802231 2009 eng d00aEpeirogenic Transgression Near a Triple Junction: The Oldest (latest early-middle Cambrian) Marine Onlap of Cratonic New York and Quebec0 aEpeirogenic Transgression Near a Triple Junction The Oldest late a552-5660 v1463 aThe discovery of a fossiliferous interval (Altona Formation, new unit) under the Potsdam Formation requires a new geological synthesis of a large part of the northeast Laurentian craton. Potsdam sandstones can no longer be regarded as the oldest sedimentary unit on the middle Proterozoic Grenville orogen in northern New York and adjacent Quebec and Ontario. The thickest Potsdam sections (to 750 m) in the east Ottawa–Bonnechere aulocogen have been explained by deposition with normal faulting possibly associated with Ediacaran rifting (c. 570 Ma) that led to formation of the Iapetus Ocean. However, sparse trilobite faunas show a terminal early Cambrian–middle middle Cambrian age of the Altona, and indicate much later marine transgression (c. 510 Ma) of the northeast Laurentian craton. Altona deposition was followed by rapid accumulation of lower Potsdam (Ausable Member) sandstone in the middle–late middle Cambrian. The Altona–Ausable succession is probably conformable. The Altona is a lower transgressive systems tract unit deposited on the inner shelf (sandstone, reddish mudstone, and carbonates) followed by aggradation and the deposition of highstand systems tract, current cross-bedded, in part terrestrial(?), feldspathic Ausable sandstone. Unexpectedly late Altona transgression and rapid Ausable deposition may reflect renewed subsidence in the Ottawa–Bonnechere aulocogen with coeval (terminal early Cambrian) faulting that formed the anoxic Franklin Basin on the Vermont platform. Thus, the oldest cover units on the northeast New York–Quebec craton record late stages in a cooling history near an Ediacaran triple junction defined by the Quebec Reentrant and New York Promontory and the Ottawa–Bonnechere aulocogen.
10aAltona Formation10aCambrian10aepeirogeny10aLaurentia10aPotsdam Formation10asequence stratigraphy10atrilobites1 aLanding, E.1 aAmati, L.1 aFranzi, D., A. uhttp://dx.doi.org/10.1017/S001675680900601302173nas a2200169 4500008004100000245009300041210006900134300001200203490000700215520165300222653002601875653001301901100001601914700002001930700001401950856003901964 2008 eng d00aFaunas and Cambrian Volcanism on the Avalonian Marginal Platform, Southern New Brunswick0 aFaunas and Cambrian Volcanism on the Avalonian Marginal Platform a884-9050 v823 aThe 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 the Paradoxides eteminicus Chron, 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. davidis Zone) is the youngest Cambrian unit in the Beaver Harbour inlier. Lapworthella cornu (Wiman, 1903) emend., a senior synonym of the genotype L. nigra (Cobbold, 1921), Hyolithellus sinuosus Cobbold, 1921, and probably Acrothyra sera Matthew, 1902a, range through the ca. 8 m.y. of the trilobite-bearing upper Lower Cambrian, and H. sinuosus and A. sera persist into the middle Middle Cambrian. Lapworthella cornu and H. sinuosus replaced the tropical taxa L. schodackensis (Lochman, 1956) and H. micans Billings, 1872, in cool-water Avalon.
10aAvalon microcontinent10aCambrian1 aLanding, E.1 aJohnson, S., C.1 aGeyer, G. uhttp://dx.doi.org/10.1666/07-007.102469nas a2200193 4500008004100000245006400041210006400105300000900169520185900178653001302037653002102050653002202071653001902093100001402112700001602126700001402142700001602156856010302172 2006 eng d00aLatest Ediacaran and Cambrian of the Moroccan Atlas Regions0 aLatest Ediacaran and Cambrian of the Moroccan Atlas Regions a7-463 aThe characteristics of the latest Ediacaran through Cambrian of the Moroccan Atlas regions are described and illustrated. Such major depositional controls as tectonic environments (a transtensional regime in this time interval) and eustatic changes that defined sequence boundaries and „Grand cycles,“ as well as a progressive southerly movement of the West Gondwanan margin that led to the loss of tropical carbonate platform facies and their replacement by siliciclastic-dominated successions in the Lower–Middle Cambrian boundary interval, are discussed briefly. The lithostratigraphic units for the uppermost Proterozoic(?) to the Upper Cambrian of the Moroccan Anti-Atlas and High Atlas mountains are reviewed and partly revised. The descriptions of lithostratigraphic units include lithology, depositional environments, fossil content, and synonymy. The Jbel Wawrmast Formation is divided into a lower Brèche à Micmacca Member and an upper Tarhoucht Member (new) that comprises the majority of the formation. The bio- and chronostratigraphy of the Atlas regions are summarized, and recently proposed, formal and informal biostratigraphical units of the Lower–Middle Cambrian are reviewed. Detailed stratigraphy allows recognition of diachroneity for several formational contacts. Controversial data and problems of the Moroccan Precambrian–Cambrian boundary are discussed in detail. The available evidence does not permit highly resolved certainty in correlations even at the stage-level with Lower Cambrian sections on other Cambrian continents. However, close similarities exist in the litho- and biostratigraphic developments of southern Morocco and Iberia, and demonstrate that both regions were coterminous on the West Gondwanan margin and geographically separated from the Avalon microcontinent by the latest Proterozoic.
10aCambrian10alatest Ediacaran10alithostratigraphy10aMoroccan Atlas1 aGeyer, G.1 aLanding, E.1 aGeyer, G.1 aLanding, E. uhttps://www.nysm.nysed.gov/staff-publications/latest-ediacaran-and-cambrian-moroccan-atlas-regions02606nas a2200253 4500008004100000245012500041210006900166300001100235520172700246653002001973653001301993653001402006653003302020653002202053653002702075653002202102653002402124653002902148100001402177700001602191700001402207700001602221856011502237 2006 eng d00aMorocco Field Excursion 2006. Ediacaran-Cambrian Depositional Environments and Stratigraphy of the Western Atlas Regions0 aMorocco Field Excursion 2006 EdiacaranCambrian Depositional Envi a47-1123 aThis field excursion emphasizes paleoenvironments, litho- and biostratigraphy, sequence boundaries, volcanic ash occurrences, and potential for intercontinental correlation of a number of important Ediacaran and Cambrian sections of the Moroccan Atlas regions. The arrangement of the sections visited during the field excursion from December 2 to 5, 2006, begins on the northern slope of the western Anti-Atlas with the lowest Cambrian at Tiout and the lower part of the trilobite-bearing Cambrian at Tazemmourt. Complete sections through the trilobite-bearing Cambrian in the Lemdad syncline feature the Cambrian in the western High Atlas range. The subsequent drive across the western Anti-Atlas shows aspects of post-Pan-African Proterozoic, siliciclastic facies with archaeocyathan bioherms in the Issafen Syncline, and spectacular slump-folding of the Lie de vin Formation as well as a siliciclastical-dominated Lower and fossiliferous Middle Cambrian in the Tata region. The final day in the field features the Devonian and the siliciclastic Middle Cambrian along the southern flank of the western Anti-Atlas and carbonate-dominated Lower Cambrian at the western rim of the Anti-Atlas.
Information on the stops includes a summary of the lithologic sequence and, if available, a complete list of faunas found at successive levels. The sample numbers with the prefix F refer either to the faunal levels of HUPÉ (1953, 1959) or SDZUY (1978); sample numbers with a comma indicate a precisely measured level above the base of the section or unit; other samples refer to horizons reported by G. GEYER (e.g., 1986, 1988b, 1990c, 1998) or to subsequent collections by the authors and W. HELDMAIER (1997).
10aBiostratigraphy10aCambrian10aEdiacaran10aintercontinental correlation10alithostratigraphy10aMoroccan Atlas regions10apaleoenvironments10asequence boundaries10avolcanic ash occurrences1 aGeyer, G.1 aLanding, E.1 aGeyer, G.1 aLanding, E. uhttps://www.nysm.nysed.gov/staff-publications/morocco-field-excursion-2006-ediacarancambrian-depositional-envi05097nas a2200313 4500008004100000245007300041210006900114300001200183490000700195520426400202653001804466653002004484653001404504653001304518653002304531653002304554653002104577653001104598653001104609653001204620653001104632653001204643653001604655653001004671653001404681100001404695700001604709856005804725 2004 eng d00aA Unified Lower-Middle Cambrian Chronostratigraphy for West Gondwana0 aUnified LowerMiddle Cambrian Chronostratigraphy for West Gondwan a233-2730 v543 aSimilarities in biotic successions support a unified, composite chronostratigraphy for the Lower-Middle Cambrian of the Iberian and Moroccan margins of West Gondwana. The Cordubian Series (emended from an Iberian stage-level unit) comprises the sub-trilobitic Lower Cambrian of West Gondwana. This series represents ca. half of the Cambrian (ca. 25 m.y.), has a base defined at the lowest occurrence of diagnostic Cambrian ichnogenera in central Spain, and is comparable to the Placentian Series of Avalon. The overlying trilobite-bearing Lower Cambrian (ca. 9 m.y. duration), or Atlasian Series (new), of West Gondwana consists of two stages originally defined in highly fossiliferous (trilobites and archaeocyaths) Moroccan sections where they have great potential for precise U-Pb geochronology. The penultimate Lower Cambrian stage, the Issendalenian, with the near-joint lowest occurrence of trilobites and archaeocyaths, is approximately comparable with the sparsely fossiliferous, Iberian "Ovetian Stage" (designation abandoned). The "Ovetian" as currently revised is invalid because it is an objective homonym of SDZUY’s original “Ovetian.” The "Ovetian" is not a practically applicable unit as its basal stratotype horizon lacks any identified fossils, and its trilobites are so rare that it cannot serve as a standard for interregional correlation. By contrast, the Banian Stage as defined in Morocco is suitable as the terminal Lower Cambrian stage of West Gondwana. It is based on very fossiliferous successions that allow recognition of three successive trilobite zones and is similar in concept to the Iberian “Marianian Stage” (designation abandoned). The “Marianian” lacks a designated lower boundary stratotype locality, lacks a biostratigraphically defined base at a stratotype, and is so sparsely fossiliferous that no biostratigraphic zonation exists.
Long-term problems involving regional definition of the West Gondwanan Lower–Middle Cambrian boundary are resolved. The lowest occurrence of paradoxidid trilobites, the classic index for the base of the Middle Cambrian, is diachronous in West Gondwana and other regions, with the group showing a delayed appearance in Iberia, Sweden, and Bohemia, by comparison with Morocco. Taxonomic revision of Iberian trilobites and new documentation of their ranges in Morocco show that the Iberian terminal “Lower Cambrian” “Bilbilian Stage” (designation abandoned) correlates with the Moroccan upper Banian and lower and middle “Tissafinian” Stages and with the Siberian upper Toyonian (traditionally assigned to the Lower Cambrian in Siberia) and lower Amgan (assigned to the Middle Cambrian in Siberia) Stages. The “Bilbilian” thus includes Middle Cambrian strata in a traditional international concept. Faunas from the base of the Iberian “lowest” Middle Cambrian “Leonian Stage” (designation abandoned) correlate largely into the second trilobite zone of the “Tissafinian” and are now understood to appear above an intra-Middle Cambrian faunal break. This faunal break is still poorly understood and may be an artifact of collection failure immediately above the sparsely fossiliferous, problematical “Valdemiedes event” interval. The base of this “Middle Cambrian”, now termed Celtiberian Series (new designation), in West Gondwana is best defined by the base of the lower Middle Cambrian Agdzian Stage (new designation). The Agdzian includes the “Tissafinian” and overlying lower “Toushamian Stage” designations abandoned) of Morocco, and has its top defined by the base of the middle Middle Cambrian Caesaraugustian Stage, as defined in Spain at the lowest occurrence of Badulesia tenera. The Languedocian, originally defined at the lowest occurrence of Solenopleuropsis (Manublesia) thorali in the southern Montagne Noire of France comprises the third, and terminal stage of the Celtiberian Series. We suggest that the designations “Lower Cambrian” and “Middle Cambrian” be regarded as descriptive and nonchronostratigraphic terms in discussions of the Cambrian.
10aAgdzian Stage10aAtlasian Series10aAustralia10aCambrian10aCeltiberian Series10achronostratigraphy10aCordubian Series10aIsrael10aJordan10aMorocco10aPoland10aSiberia10aSouth China10aSpain10aTrilobita1 aGeyer, G.1 aLanding, E. uhttps://geojournals.pgi.gov.pl/agp/article/view/1027401358nas a2200205 4500008004100000245008300041210006900124260009100193300001100284520067000295653002400965653001300989653001101002653001101013100001401024700001601038700002201054700001601076856006001092 2000 eng d00aThe Cambrian in Israel and Jordan-The Feather Edge of the Mediterranean Region0 aCambrian in Israel and JordanThe Feather Edge of the Mediterrane bInstituto Superior de Correlacion Geologica (INSUGEO), Universidad Nacional de Tucuman a98-1013 aThe Cambrian of Israel and Jordan belongs to the relatively poorly known regions of Cambrian rocks. The outcrops cover small areas in the southernmost part of Israel, from about 50 km north of Eilat to almost the Red Sea, and areas in the southwestem part of Jordan. The best outcrops are found in the Timna area of Israel, which includes the legendary copper mines of King Solomon, at the eastern shore of the Dead Sea, in the Petra area, and in the Wadi Ram region of Jordan. They belong to a thick blanket of Cambrian through Cretaceous clastics which drapes the northern margin of the Arabo-Nubian Shield and was formerly termed the "Nubian sandstone".
10aArabo-Nubian Shield10aCambrian10aIsrael10aJordan1 aGeyer, G.1 aLanding, E.1 aAcenolaza, G., F.1 aPeralta, S. uhttp://insugeo.org.ar/publicaciones/docs/misc-06-24.pdf00621nas a2200181 4500008004100000245011700041210006900158300001200227490000700239653001300246653001300259653002800272653001800300653001500318100002000333700001600353856007000369 2000 eng d00aLower Cambrian (Branchian) Trilobites and Biostratigraphy of the Hanford Brook Formation, Southern New Brunswick0 aLower Cambrian Branchian Trilobites and Biostratigraphy of the H a858-8780 v7410aAvalonia10aCambrian10aHanford Brook Formation10aNorth America10atrilobites1 aWestrop, S., R.1 aLanding, E. uhttp://dx.doi.org/10.1666/0022-3360(2000)074<0858:LCBTAB>2.0.CO;201796nas a2200169 4500008004100000245013300041210006900174300001200243490000700255520124600262653001301508653001401521653002001535653001401555100001601569856004101585 1993 eng d00aIn Situ Earliest Cambrian Tube Worms and the Oldest Metazoan-Constructed Biostrome (Placentian Series, Southeastern Newfoundland0 aIn Situ Earliest Cambrian Tube Worms and the Oldest MetazoanCons a333-3420 v673 a