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%3Dihub03100nas 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 a

Re-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/S001282521730523802606nas 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 a

This 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-envi