High-precision U-Pb zircon ages on SE Newfoundland tuffs now bracket the Avalonian Lower–Middle Cambrian boundary. Upper Lower Cambrian Brigus Formation tuffs yield depositional ages of 507.91 ± 0.07 Ma (Callavia broeggeri Zone) and 507.67 ± 0.08 Ma and 507.21 ± 0.13 Ma (Morocconus-Condylopyge eli Assemblage interval). Lower Middle Cambrian Chamberlain’s Brook Formation tuffs have depositional ages of 506.34 ± 0.21 Ma (Kiskinella cristata Zone) and 506.25 ± 0.07 Ma (Eccaparadoxides bennetti Zone). The composite unconformity separating the Brigus and Chamberlain’s Brook formations is constrained between these ages. An Avalonian Lower–Middle Cambrian boundary between 507.2 ± 0.1 and 506.3 ± 0.2 Ma is consistent with maximum depositional age constraints from southwest Laurentia, which indicate an age for the base of the Miaolingian Series, as locally interpreted, of ≤ 506.6 ± 0.3 Ma. The Miaolingian Series’ base is interpreted as correlative within ≤ 0.3 ± 0.3 Ma between Cambrian palaeocontinents, although its exact synchrony is questionable due to taxonomic problems with a possible Oryctocephalus indicus-plexus, invariable dysoxic lithofacies control of O. indicus and diachronous occurrence of O. indicus in temporally distinct δ 13C chemozones in South China and SW Laurentia. The lowest occurrence of O. indicus assemblages is linked to onlap (epeirogenic or eustatic) of dysoxic facies. A united Avalonia is shown by late Early Cambrian volcanics in SW New Brunswick; Cape Breton Island; SE Newfoundland; and the Wrekin area, England. The new U-Pb ages revise Avalonian geological evolution as they show rapid epeirogenic changes through depositional sequences 4a–6.

Fossils within early Cambrian phosphorites worldwide are often well preserved due to early diagenetic permineralization. Here, we examine the fossil record contained within phosphorites of the Lower Cambrian Pusa Formation (late Fortunian to Cambrian Stage 2) in Fontanarejo, central Spain. The sedimentology and age of these phosphorites have been controversial and are here reviewed and discussed, providing also an updated geological map. The Pusa Formation is composed of fine clastic sediments that are partly turbiditic, with channels of quartz-rich conglomerates and abundant phosphorites in the upper part of the succession. The microfacies and mineralogy of these channel deposits are studied here for the first time in detail, showing that they are mainly composed of subspherical apatite clasts, with minor mudstone intraclasts, quartzite and mica grains. Numerous sponge spicules, as well as entirely preserved hexactinellid sponges and demosponges, were collected within these phosphorites and likely represent stem groups. In addition to sponges, other fossils, such as small shelly fossils (SSF) of the mollusc Anabarella sp., were found. The phosphorites exhibit multiple evidence of intense microbial activity, including diverse fabrics (phosphatic oncoidal-like microbialites, thrombolites, stromatolites and cements) and abundant fossils of filamentous microbes that strongly resemble extant sulphur-oxidizing bacteria. Our findings strongly suggest that microbial processes mediated the rapid formation of most of the Fontanarejo apatite, probably accounting for the exceptional preservation of fragile fossils such as sponge skeletons. The apparent presence of taxonomically diverse hexactinellid and demosponge communities at the lowermost Cambrian further corroborates a Precambrian origin of the phylum Porifera.

New U–Pb radioisotopic ages on early Cambrian volcanic zircons condition a high-resolution Bayesian age model that constrains the first occurrences and zonations of West Gondwanan archaeocyaths and trilobites in southern Morocco. The oldest archaeocyaths in the Tiout Member of the Igoudine Formation (519.71 + 0.26/− 0.35 Ma) are c. 6 Ma younger than the oldest Siberian archaeocyaths. The oldest Moroccan trilobite fragments, from the lower member of the Igoudine, are constrained to 519.95 + 0.43/− 0.40 Ma. The succeeding Issendalenian Stage (i.e. Hupetina antique – Eofallotaspis tioutensis – Fallotaspis plana – Choubertella – Daguinaspis trilobite zones) spans c. 1.5 Ma (519.78 + 0.26/− 0.37 Ma to 518.43 + 0.25/− 0.69 Ma). Identifiable Moroccan fallotaspidids and bigotinids, among Earth’s oldest trilobites, occur above a positive δ13C excursion dated with our age model at 520.27 + 0.59/− 0.57 Ma, and correlated with the IV excursion peak within the lower range of Siberian Atdabanian Stage trilobites (Repinaella Zone). This excursion is the best standard for a Cambrian Series 2 base. The oldest West Gondwana trilobite fragments are c. 1 Ma younger than those in Siberia and c. 0.5 Ma older than the oldest Avalonian trilobites (Callavia Zone). This diachrony means a trilobite first appearance datum is an inappropriate chronostratigraphic base for Cambrian Series 2. Taxonomic differences in the oldest trilobites between Cambrian palaeocontinents are in accordance with trace fossil evidence for the group’s appearance possibly as late as c. 530 Ma in the Cambrian Evolutionary Radiation. Coeval 519–517 Ma dates from Avalonia (cool-water siliciclastic shelf) and West Gondwana (tropical carbonate platform) sections with distinct macrofaunas emphasize these successions were latitudinally separate by the late Ediacaran Period.

Microbially induced sedimentary structures (MISS) are microbial traces in sandy deposits. They have been formed by various modes of microbial behaviour in response to the prevailing physical dynamics in shallow-marine environments since early Archaean time. An association of fossils, phosphatic structures and grains, stromatolites and microbial laminated levelling structures is documented from the Zhongyicun Member of Lower Cambrian strata in the Baideng section dated close to 535 Ma. SEM examination demonstrates that microbial laminated levelling structures are the result of the development of microbial mats composed of filamentous structures. We propose that there was a short hiatus after the dolomite layer deposited when the dolomite layer was weathered to form centimetre-scale valleys firstly, and then microbes accumulated in these valleys and formed the microbial laminated levelling structures.

Facies and stratigraphic analysis of the Port Lazo and Roche Jagu formations, together the lower part of the Plourivo-Plouézec Group, suggests deposition in three distinct depositional systems. The lower part of the Port Lazo Formation comprises red conglomerate, sandstone and shale of alluvial fan to alluvial plain origin. A conformable interval of grey sandstone and shale succeeds the lower Port Lazo red beds and records a period of subtidal sedimentation dominated by river-fed, shallow-water turbidity currents (hyperpycnites). The succeeding Roche Jagu Formation comprises red sandstones and shales of braided fluvial origin. It is intercalated with, and succeeded by, andesites. The andesites succeeding the fluvial strata overlie a prominent erosion surface and are lava flows, whereas those intercalated with the fluvial strata are intrusions. Rb–Sr radiometric dating of the andesites at 472+/−5 Ma is commonly used as evidence for the whole Plourivo-Plouézec Group being Early Ordovician in age. However, the stratigraphic relationships and patterns of sedimentation in the Port Lazo and Roche Jagu formations, together with the localized presence of Arumberia, suggest they are most likely of early Cambrian age and related to a phase of post-Cadomian rifting. The facies deposited show both similarities to and differences from neighbouring strata of equivalent age, and highlight the control exerted by sediment load on alluvial and nearshore processes on early Palaeozoic environments.

The earliest known macroborings (Trypanites) from Baltica occur in early Cambrian phosphatized siltstone pebbles from Kopli quarry in Tallinn, Estonia. Trypanites borings also occur in Furongian phosphatized siltstone pebbles in northern Estonia. The intensity of bioerosion on these Cambrian pebbles is low compared to analogue substrates from Ordovician deposits of Baltica. These bored phosphatized siltstone pebbles show that bioerosion of hard substrates occurred in relatively cold climate epicontinental seas during Cambrian time.

Detailed analysis of the distribution of archaeocyaths in five lower Cambrian sections in South China has resulted in the erection of four new archaeocyathan zones and one new archaeocyathan bed. Listed in order of ascending age, these are: the Dailycyathus xiuqiensis Zone; the Dictyocyathus shaanxiensis Zone; the Spirillicyathus duplex Range Zone; the Sibirecyathus meitanensis Range Zone; and the Archaeocyathus yanjiaoensis beds. These new subdivisions permit a correlation of lower Cambrian strata both within the area of the Yangtze Platform (South China) as well as between this region and Siberia, Australia, Western Europe and North America. Within the Yangtze Platform area, archaeocyaths of the Dailycyathus xiuqiensis and Dictyocyathus shaanxiensis zones co-occur with trilobites of the middle and upper Eoredlichia Trilobite Zone of the Qiongzhusian Stage. The Spirillicyathus duplex and the Sibirecyathus meitanensis Range Zone correspond to the Malungia, Yiliangella–Yunnanaspis and Drepanuroides Trilobite zones of the basal and middle Canglangpuan Stage, respectively. Finally, the Archaeocyathus yanjiaoensis beds belong to the Palaeolenus fengyangensis Trilobite Zone of the upper Canglangpuan Stage. Global correlations based on archaeocyath assemblage zones suggest that: (1) the middle–upper Qiongzhusian of South China correlates with the middle Atdabanian Stage of the Siberian Platform, the Warriootacyathus wilkawillinensis Archaeocyath Zone in South Australia, the middle Issendalenian Stage of Morocco and the lower Ovetian Stage in Spain; (2) the lowermost Canglangpuan Stage of South China correlates with the uppermost Atdabanian of the Siberian Platform, the Spirillicyathus tenuis – Jugalicyathus tardus archaeocyath zones in South Australia, the uppermost Issendalenian – lower Banian stages of Morocco, the middle Ovetian Stage of Spain and the middle Montezuman Stage of North America; (3) the middle Canglangpuan Stage approximates the lowermost Botoman Stage of the Siberian Platform, middle Banian Stage of Morocco, the uppermost Ovetian – lowermost Marianian stages of Spain and the upper Montezuman Stage of North America; (4) the uppermost Canglangpuan Stage is equivalent of the middle Toyonian Stage of the Siberian Platform, Archaeocyathus abacus beds in Australia, the middle Bilbilian Stage in Spain and the middle Dyeran Stage (Bolbolenellus euryparia Trilobite Zone) in North America.

Trilobites from the upper unit of the Lower Cambrian Pusa Formation (south-central Spain) substantially antedate other Iberian trilobites, according to widely published correlation schemes, and arguably would be among the earliest trilobites globally. These trilobites, previously only briefly mentioned in texts, are here described and illustrated, and their biochronological context examined. The Pusa Formation trilobites are treated in open nomenclature but with suggested affinity to the genus Abadiella. They are associated with small shelly fossils, including Pelagiella sp., chancellorid spicules and Cupitheca sp., and unidentfied archaeocyathans. Trace fossils from the upper unit of the Pusa Formation, down-section of the trilobites, include Dactyloidites isp. and Rusophycus isp., the latter representing the lowest occurrence of this ichnogenus in the region. This biostratigraphical context demonstrates that the Pusa Formation trilobites are substantially younger than had traditionally been thought. In terms of Iberian regional stages they are Ovetian, not Corduban as previously thought. As a consequence of the data presented here, the definitions of Iberian Lower Cambrian regional stages are discussed and a substantially revised correlation between key Lower Cambrian strata of the Central Iberian and Ossa Morena zones is proposed.

Phosphatized articulated palaeoscolecid scleritome fragments with attached Hadimopanella Gedik, 1977 plates are described from the lower Cambrian Mernmerna Formation of South Australia. Hadimopanella is principally known from single, isolated, button-shaped, phosphatic sclerites. The new articulated material from South Australia reveals for the first time the configuration of plates referable to Hadimopanella within the scleritome. The scleritome fragments represent the main trunk sections of the cuticle with anterior and posterior terminations lacking. Each annulus on the trunk is ornamented by rows of irregularly alternating Hadimopanella plates. The large majority of plates display a single, centrally located, conical node referable to the form species H. apicata Wrona, 1982. However, individual plates display considerable morphological variation with plates situated along the flattened trunk margin identical to the form species H. antarctica Wrona, 1987. The South Australian material displays the detailed scleritome configuration of cuticular plates and platelets and demonstrates irrefutably that plates of the form species H. apicata and H. antarctica occur as mineralized cuticular elements on the same palaeoscolecid scleritome.

The early Cambrian Chengjiang biota in Yunnan, southern China has yielded many articulated exoskeletons of the spiny redlichiid trilobite Eoredlichia intermedia, of which some have their appendages exceptionally well preserved. Both of the paired uniramous antennae of a medium-sized holaspis consist of 46–50 short segments (articles), each of which bears a fine spine near its inner edge. Behind the antennae there are twenty-one pairs of biramous limbs: three pairs are situated underneath the cephalon, one pair underneath each of the fifteen thoracic segments, and probably three pairs underneath the small pygidium. The endopod consists of a broad basis and seven podomeres, of which the last is divided into three terminal spines. The exopod is blade-like, and according to one interpretation, is dorsally hinged to the basis of the endopod; an alternative suggestion being that both the endopod and exopod are split from the basis, the latter being independent and not forming part of the endopod. The exopod has a prominent anterior rim, and possesses about forty long filaments along the posterior margin, and short setae along the rounded distal lobe. The basic appendage features of the redlichiid trilobites, and likewise the gut, are comparable to those of other known Cambrian polymerid trilobites that belong to more distantly related clades.

A lower Cambrian eodiscoid trilobite fauna and an associated holmiid trilobite, Holmia sp., are described from a bioclastic limestone at the top of the Torneträsk Formation in the Luobákti section, south of Lake Torneträsk, northern Sweden. Other associated polymerid trilobites include Orodes? lapponica and Strenuaeva inflata. The precise age of the trilobite fauna cannot be determined, but its generic composition and stratigraphical position at the top of the lower Cambrian suggest that it was recovered from the Ornamentaspis? linnarssoni Assemblage Zone. Two species of eodiscoids are present: Neocobboldia aff. dentata and Chelediscus acifer. The latter species is known previously from England and southeastern Newfoundland, and provides a novel link between upper lower Cambrian successions in Baltica and Avalonia.

A revision of the trilobite fauna from Brzechów in the Holy Cross Mountains (Poland) shows that the assemblage consists of Palaeolenus medius (Bednarczyk), Issafeniella orlowinensis (Samsonowicz), Kingaspidoides sanctacrucensis (Czarnocki), Paradoxides (Acadoparadoxides) oelandicus Sjögren, P. (A.) cf. mureroensis Sdzuy and P. (A.) sp. It is earliest Middle Cambrian in age according to the West Gondwana standard of Geyer & Landing (2004) and can be correlated with the Cephalopyge notabilis Zone of Morocco. Moreover, the co-occurrence of the ranges of P. (A.) oelandicus with P. (A.) cf. mureroensis might suggest that P. (A.) oelandicus appears earlier in the Brzechów sandstones than in Scandinavia, thus the strata exposed here do not find their correlative in the Scandinavian succession. As a result, the Banian/Agdzian boundary (Lower–Middle Cambrian boundary according to the West Gondwana standard) probably lies within the Kamieniec Formation, and also below the Brzechów sandstones, in the upper part of the Ociesęki Formation. Close similarity of the discussed assemblage with contemporaneous assemblages from Morocco, Jordan or New Brunswick indicates that the fauna is generally of peri-Gondwanan and Gondwanan aspect.

Mudstones and shales in the Lower Cambrian Shipai Formation in the Three Gorge area, Hubei, China, are richly fossiliferous, containing common shelly fossils and some soft-bodied fossils. The latter provide important new information about the nature and variety of Cambrian soft-bodied organisms. Identifiable, non-mineralized taxa include components of the Chengjiang fauna, such as Vetulicola Hou, 1987, a palaeoscolecidan referable to Maotianshania Sun & Hou, 1987, and a brachiopod Diandongiapista with pedicle preserved (not illustrated). Cambrorhytium Conway Morris & Robison, 1988, co-occurring both in the Burgess Shale and the Chengjiang Lagerstätte, was also recovered. Additionally, a new worm is described based on two specimens. This taxon, in common with many other fossil worms, has a slender, cylindrical body with annulations, but it is characterized by each annulus bearing an elevated ridge and lacking surface ornamentation. The occurrence of exceptional preservation in the Shipai Formation has likely been overlooked due to the relatively poor resolution of soft-bodied fossils; nevertheless, this occurrence is an important extension of the Burgess Shale-type biotas in China, over 1500 km northeast of the provenance of the Chengjiang Lagerstätte.

Lower Cambrian shallow-water carbonates enclosing microbial structures are documented for the first time from the upper Lastours Member of the Montagne Noire (southern France). Microbial organisms constructed self-supported boundstones resulting in the formation of exclusively microbial-accreted buildups, which exhibit three main types of non-skeletal microbialites: planar stratiform stromatolites, dome-shaped stromatolites and nonlaminated (thrombolitic) biostromes. In addition, thrombolitic boundstones display four distinct microbial microstructures: clotted and Renalcis-like forms, branching bushy forms, clusters of unbranching straight filaments and crustose forms.

The upper member of the Lastours Formation records an upward transition from a shalydominant open shelf to a protected shelf environment bounded by a surface representing a major subaerial exposure. Initially, at the inception of the highstand systems tract, flat stratiform stromatolites formed on open sea subtidal shaly substrates, while stacked domal stromatolites developed in peritidal areas which record subaerial exposure. In contrast, prograding shoal barriers of the transgressive systems tract favoured the establishment of thrombolitic boundstones in protected (back-shoal) environments.