Silurian trace fossils in carbonate turbidites from the Alexander arc of southeastern Alaska

Early to Late Silurian (Llandovery‐Ludlow) body and trace fossils from the Heceta Formation of southeastern Alaska are preserved in the oldest widespread carbonates in the Alexander terrane. These fossils represent the earliest benthos to inhabit diverse shallow and deep subtidal environments in the region and are important indicators of early stages in benthic community development within the evolving Alexander arc. The ichnofossils are particularly significant because they add to a small but growing body of knowledge about trace fossils in deep‐water carbonates of Paleozoic age.

Carbonate turbidites that originated along a deep marine slope within the arc yield a low‐diversity suite of trace fossils consisting of five distinct biogenic forms. Simple burrows (Planolites, two forms), ramifying tunnels (Chondrites), and tiny cylindrical burrows (?Chondrites) represent the feeding activities (fodinichnia) of pre‐turbidite animals that burrowed in the lime mud before the influx of coarser sediment deposited by turbidity currents. These trace fossils are associated locally with cross‐cutting burrows created as domichnia (Palaeophycus). Rarer hypichnial burrows and endichnial traces were created by post‐turbidite animals that fed soon after the deposition of coarse detritus from turbidity flows.

Trace fossils in these deposits reflect much lower diversity levels than in Paleozoic siliciclastic turbidites. This difference may represent unfavorable environmental conditions for infaunas, differential preservation, or significant paleogeographic isolation of the Alexander terrane during the Silurian. Greater utilization of trace fossils in terrane analysis may help to resolve this issue and provide new data for reconstructing the paleogeography of circum‐Pacific terranes.     

A Curious Rusophycus (Arthropod Ichnofossil) Assemblage from the Upper Ordovician of Ontario,Canada

The ichnogenus Rusophycus includes a wide range of short bilobate excavations generally attributed to variable feeding behaviors of arthropods, especially trilobites. An unusual Rusophycus assemblage from Upper Ordovician Georgian Bay Formation in Ontario departs radically from previously described examples and presents new challenges for understanding the behavior represented by these traces. This specimen is unique in the arrangement of multiple Rusophycus burrows in a circular, lens-shaped array (as opposed to a linear or random arrangement typical of other Rusophycus assemblages). The size and shape of the individual Rusophycus components are consistent with traces attributed to the coeval trilobite Flexicalymene. Multiple Rusophycus assemblages likely reflect aggregations of trilobites in response to a local concentration of food. The topology of this particular Rusophycus assemblage suggests that the trilobites opportunistically exploited a rich and narrowly restricted food source, perhaps the decaying remains of a buried organism.     

Aligned trace fossils from the Utica Shale: implications for mode of life and feeding in the trilobite Triarthrus beckii

The olenid trilobite Triarthrus commonly occurs in nearly monospecific assemblages within otherwise relatively barren black shales. As such, it has been proposed that these trilobites preferred dysoxic or even anoxic habitats and suggested feeding habits range from predation and particle feeding to chemoautotrophism. A unique bedding‐plane assemblage of aligned traces that grade from Rusophycus to Cruziana, with associated Triarthrus beckii carcasses, are described from three localities in the Indian Castle Formation (upper Utica Shale) just below a K‐bentonite bed. Although few body fossils are preserved, it is clear that the 15‐cm‐thick, laterally extensive Thruway K‐bentonite created a unique taphonomic window that preserved the activities of numerous olenid trilobites. Rusophycus and Cruziana, consistently observed in densities above 100 trackways/m², were excavated by the trilobites into the upper surface of a micro‐graded bed, likely a distal turbidite deposit. Sedimentological and trace metal data (Mo, Mn, V and U) support dysoxic but not persistently anoxic conditions through this interval. Measurements from over 500 individual trackways have mean orientations of 259.1° (WSW) at the Myers Rd. locality and 224.59° (SW) at the Dolgeville Dam locality. These orientations are closely similar to independent sedimentological indicators of current transport direction at these sites, which indicates that the trilobites preferentially faced into the prevailing current. The trackways provide compelling evidence that Triarthrus beckii individuals were engaged in feeding, probably assisted by current transport of particles. These results do not support previous suggestions that Triarthrus may have relied upon a chemoautotrophic life habit, but are consistent with suggestions of predation or scavenging from the sediment.     

The Tommotian phase of the Early Cambrian Agronomic Revolution in the carbonate mud environment of central Siberia

The profound ecological change of the marine benthos that eventually led to the almost complete destruction of the Precambrian matgrounds by benthic grazers and bioturbators (the agronomic revolution) was largely completed in the Tommotian. At that time, burrows produced by bottom‐dwelling animals as shelters against predators were supplemented by burrowing for food by predators and sediment feeders. The limy mud ichnofauna of that age in Siberia was very different from the roughly coeval sand bottom faunas of Baltica. Although the exact zoological identity of the animals forming the infaunal Tommotian traces remains unknown, they probably mostly represent various kinds of early nemathelminthes. No apparent locomotion traces of mollusc origin have been encountered in the Early Cambrian, despite the abundant occurrence of skeletal fossils attributed to molluscs. Possibly the standard muscular foot, typical of modern molluscs, had not yet developed. Ichnotaxa represented are Teichichnus isp., Rhizocorallium isp., Chondrites isp., possibly the Buren ichnocomplex and others.     

Multiple-Rusophycus (Arthropod Ichnofossil) Assemblages and Their Significance

Rusophycus is an ichnogenus comprising shallow burrows generally attributed to trilobites and other arthropods. The paleoethological interpretation of these structures is not conclusively known; workers variously have attributed the ichnogenus to feeding, resting, hiding/escape, hunting or nesting behaviors. Rusophycus morphology varies from unornamented, bilobed forms to forms that preserve details of ventral anatomy of the trace maker. Rusophycus occurs as single or multiple impressions. Some examples of multiple-Rusophycus assemblages are clearly the result of the activity of a single animal (e.g., serially arranged impressions of the same size), but others represent the activity of several individuals. Associated traces representing multiple individuals are especially interesting, for they may give evidence of complex behavior, for example, interactions between the trace makers. Some of the multiple-trace assemblages show alignment (congruent anterior-posterior orientation of the individuals) suggesting rheotactic behavior; other assemblages comprise randomly oriented traces. The difference between the aligned and randomly oriented assemblages may reflect differences in the current energy and amount of available food, and may also suggest the following feeding modes for these benthic-feeding arthropods: (1) alignment with head into the current in resource-poor environments, (2) orientation with head at an oblique angle to the current in high-energy, resource-poor environments, and (3) random orientation in low-energy, resource-rich environments.     

Triassic trace fossils from lacustrine shoreline deposits of the Passaic formation,douglassville, pennsylvania

Lake‐margin deposits of the Late Triassic Passaic Formation, Douglassville, Pennsylvania, have yielded a moderate variety of trace fossils. The greatest diversity and abundance of trace fossils occurs on the sole of a thin gray claystone overlain and underlain by gray siltstones. Specimens of Cochlichnus anguineus, Helminthoidichnites tenuis, Helminthopsis hieroglyphica, Treptichnus pollardi, and paired trails reflect simple, unspecialized, horizontal grazing as well as feeding traces under very shallow water lacustrine conditions. The lack of commonly associated Scoyenia burrows in these deposits may possibly be related to the degree of maturation of the organic debris available. The traces, as well as a lack of meniscate burrows, compare favorably to the Mermia ichnofacies, except Passaic deposits exhibit evidence of subaerial exposure. This unit most likely records a lacustrine expansion whereby grazing trails were emplaced under fully subaqueous conditions. Subsequent shallowing and desiccation, followed by sediment influx during rainstorms, favored preservation of these traces.

In contrast, the Scoyenia ichnofacies consists of feeding burrows of Scoyenia gracilis and Spongeliomorpha milfordensis within reddish brown siltstones and mud‐stones (redbed sequence). The Scoyenia ichnofacies records limited exploitation, by opportunistic infaunal deposit feeders, of lake‐margin nutrients carried in during occasional rainstorms that punctuated otherwise extended periods of aridity.     

Trace fossils in middle to late triassic fluvial redbeds,pranhita‐godavari valley,south India

Several morphological varieties of trace fossils abound in Middle and Late Triassic fluvial redbeds in the Pranhita‐Godavari Valley, south India, including Skolithos, Palaeophycus, Taenidium, escape burrows, and a type of trace very similar to ‘small stuffed burrows’ from the Triassic of Greenland. Burrow morphology was influenced by local hydrodynamic conditions. The distribution of burrows was facies controlled; some forms are restricted to channel deposits whereas others occur only in floodplains. Vertical dwelling burrows (Skolithos) occur in both channel and floodplain deposits. Horizontal structures representing deposit feeding (Taenidium) are confined to nondepositional surfaces within parallel‐laminated sandstones having parting lineations that represent catastrophically emplaced sand‐sheets in channels and proximal floodplains. Vertical escape burrows are confined to what were slowly but continually accreting parallel‐laminated sands of channel bars. Horizontal dwelling burrows (Palaeophycus) and ‘small stuffed burrows’ are virtually restricted to the smaller sandsheets of floodplain drainage systems.

The burrow assemblages do not occur as recurrent associations throughout the redbed sequence, and variations in different stratigraphic levels seem to be controlled by minor differences within a broadly similar environment. The entire assemblage has components of both the Scoyenia and Rusophycus ichnocoenoses reported from East Greenland but may be considered as the Scoyenia ichnofacies characteristic of redbeds deposited in extensive floodplains dissected by small streams, even though no Scoyenia individuals are present.     

An integrative ichnological and taphonomic approach in a transgressive–regressive cycle: a case study from Devonian of Paraná Basin,Brazil

The palaeoenvironmental context of a section of the Devonian Ponta Grossa Formation (Paraná Basin) was examined using an integrated ichnological and taphonomic approach. Three taphofacies (T‐A, T‐B and T‐C) and six ichnofabrics are recognized. T‐A is mainly composed of disarticulated organisms and is associated with Chondrites, Planolites‐Palaeophycus, Asterosoma‐Zoophycos and Asterosoma‐Chondrites ichnofabrics, representing the Cruziana ichnofacies. The upward increase in diversity and abundance of body fossils for Taphofacies A can be explained by changes in sedimentation rates during aggradational to progradational phases. T‐B beds, represented by articulated brachiopods, occur in distal tempestites associated with the Skolithos ichnofabric (Skolithos ichnofacies) and represent higher hydrodynamic energy and oxygenation than in T‐A. Taphofacies C, characterized by a mix of articulated and disarticulated organisms, generally lacks bioturbation except for Chondrites ichnofabrics occurring only at the bed tops, suggesting low substrate oxygenation and low‐energy conditions. T‐C indicates the maximum transgression in the T‐R cycle, characterizing it as a good indicator of maximum flooding surfaces. The composite Asterosoma‐Teichichnus ichnofabric (bioturbation degree 5) occurs in layers without body fossils and represents suites of the Cruziana ichnofacies. This likely reflects intense intrastratal activity at all substrate levels, which facilitated the oxygenation of the substrate disallowing the preservation of organism remains. This observation indicates that the bioturbation is an important factor controlling the loss of taphonomic information within the TAZ, mainly when associated with detritus‐feeding trace fossils.     

Trace fossils formed by heart urchins - a study of Scolicia and related traces

Cretaceous and Tertiary traces belonging to the ichnogenera Scolicia, Subphyllochorda and Taphrhelminthopsis are described and analysed functionally. Resting traces continuous with Subphyllochorda are described for the first time and interpreted as the work of heart urchins. The new ichnogenus Cardioichnus is erected for them. The preservation and complexity of some specimens of these ichnogenera allows for a detailed comparison with heart urchin morphology. Subphyllochorda is interpreted as a burrow produced by heart urchins and Scolicia as either burrows or sea floor furrows. The traces here assigned to Taphrhelminthopsis are probably casts of washed-out Subphyllochorda burrows. Palaeozoic traces previously referred to 'Scolicia' sensu lato are, in the main, much simpler than the Mesozoic and Tertiary traces and should be transferred to other ichnogenera.     

Devonian Trace Fossils of the Horlick Formation,Ohio Range,Antarctica: Systematic Description and Palaeoenvironmental Interpretation

The clastic Horlick Formation contains an ichnofauna of 28 ichnotaxa dominated by burrowers. These are a mixture of simple vertical forms (Skolithos linearis, S. magnus, Bergaueria cf. langi, Rosselia socialis, Monocraterion isp.), U or arc-like forms (Diplocraterion parallelum, Arenicolites types A and B, Catenarichnus antarcticus, C. isp., aff. Lanicoidichna isp.), and complex, vertical spiral structures (Asterosoma isp., Spirophyton isp.). Horizontal burrows include Ancorichnus cf. capronus, Palaeophycus tubularis, and Psammichnites devonicus isp. nov. Surface traces comprise Haplotichnus isp., Cruziana problematica, C. rhenana, Rusophycus aff. carbonarius, R. isp., Protovirgularia rugosa, Lockeia ornata and cubichnia indet., while trackways include Diplichnites gouldi, D. isp., Maculichna? isp. and large imprints. The Horlick Formation (maximum 56 m) records an early Devonian transgression onto a deeply weathered land area that lay in the direction of Marie Byrd Land, spreading from the South Africa sector of Gondwana. Analysis of the trace fossils confirms their formation in near-shore to intertidal environments, with some ichnotaxa living close to the marine/fluvial boundary (e.g., Spirophyton, aff. Lanicoidichna, Cruziana problematica, Rusophycus aff. carbonarius, Maculichna?). The ichnofauna probably comprised a variety of marine suspension and deposit-feeding worms, shallow burrowing molluscs (bivalves and possibly bellerophontids) and several different types of arthropods, including trilobites.     

Burrow construction and behavior of tilefish,Lopholatilus chamaeleonticeps,in Hudson Submarine Canyon

Synopsis During 22 daylight submersible dives in August 1979 numerous juvenile and adult tilefish, Lopholatilus chamaeleonticeps, were observed in and around vertical burrows in the clay substrate of portions of Hudson submarine canyon in depths from 110–230 m. The size and shape of the burrows varied considerably with the smallest juveniles occupying simple vertical shafts in the substrate. Larger fish were found in much larger burrows (up to 4–5 m in diameter and at least 2–3 m deep) that were funnel shaped in cross-section with the upper conical portions containing numerous smaller burrows of associated crabs. The range of burrow sizes observed suggests a regular sequence of burrow construction by tilefish and the associated crabs. Both juvenile and adult tilefish swam into the burrows head first and exited tail first. This behavior, which would preclude the possibility of ambushing prey, and evidence of predation by sharks and other tilefish, suggests that the burrow is a refuge from predators.Tilefish burrows appear to serve as a focus for biological activity. Species associated with the burrows included galatheid crabs, Cancer sp., Acanthocarpus alexandri, Homarus americanus, Heliocolenus dactylopterus and Conger oceanicus. Tilefish may play an important role in structuring outer continental shelf communities. They physically shape their environment and probably have significant biological interactions with the species that associate with their burrows.     

<Emphasis Type="Italic">Teichichnus zigzag</Emphasis> Frey and Bromley, 1985: a probable echiuran or holothurian burrow from the Jurassic offshore Norway

Arcuate to V-shaped spreiten burrows are common in marginal-marine Jurassic deposits from offshore Norway and are described in detail from well-core material. Well-preserved specimens show a tripartite architecture with convex-down stacked laminae (retrusive) in the lower part, convex-up stacked laminae (protrusive) in the upper part of the burrow, and a passively filled terminal causative burrow in between. A large funnel-shaped structure and/or a homogeneous area can also occur in the upper part of the burrow. Based on their morphology and features, these burrows can be assigned to the ichnogenus Teichichnus Seilacher, 1955, although they appear to be more developed and complete than hitherto described Teichichnus ichnospecies. Similar burrows were described as Teichichnus zigzag Frey and Bromley, 1985. The overall morphology and details of the burrows, in comparison with modern analogues and neoichnological experiments, suggest echiurans (spoon worms) or holothurians (sea cucumbers) with a combined suspension- and deposit-feeding behaviour as potential producers.     

Remarkably preserved benthic organisms and their traces from a Middle Triassic (Muschelkalk) mud flat

Knaust, D. 2010: Remarkably preserved benthic organisms and their traces from a Middle Triassic (Muschelkalk) mud flat. Lethaia, Vol. 43, pp. 344–356. A new Fossil‐Lagerstätte is reported from the Middle Triassic of Germany, preserving Foraminifera, Nematoda, Platyhelminthes, Nemertea, Annelida and a range of Arthropoda together with their traces. This is the oldest fossil record of free‐living nematodes and turbellarians, and the first occurrence of nemerteans in the Mesozoic. The rare preservation of the benthic associations together with their traces is unique; especially the abundant occurrence of different phyla as meiofauna (organisms with shortest dimension between 0.06 and 1 mm) provides an insight into the palaeoecological conditions of a 240‐Ma‐old muddy tidal flat. The preservation of benthic animals at the termination of their traces offers the exclusive opportunity to assign producers to the trace fossils. The results show that the discussed phyla were already established in the early Mesozoic in a similar diversity and composition as in modern analogues. The new Fossil‐Lagerstätte has the potential to prove a number of soft‐bodied taxa immediately after the end‐Permian mass extinction, which has wide‐ranging implications for phylogenetic interpretations. □Benthos, soft‐bodied organisms, Fossil‐Lagerstätte, Muschelkalk, trace fossils, Triassic.     

Arthrophycus as a mimic of crinoid column impressions in the lower Silurian of central Kentucky,USA

Unusual specimens of an ichnofossil, herein ascribed to Arthrophycus, are described from siltstone tempestites in the lower Silurian (Llandovery, Telychian) Estill Shale near Irvine, Estill County, central Kentucky, USA. The specimens display closely spaced, uncurved transverse annulations, but lack the medial ridge, rectangular cross‐sectional shape and dense branching typical of common Silurian Arthrophycus ichnospecies. This combination of features, coupled with the straightness of burrows and alignment parallel to inorganic tool marks, closely approximates the appearance of moulds of partially articulated crinoid columns (= pluricolumnals) that were impressed into firm mud and cast by storm‐deposited sediment. That these structures do not represent the external moulds of body fossils is suggested by minor width variations along the long axis of specimens, possible bioglyphs and the total absence of skeletal material, including isolated crinoid columnals, in this and other tempestites from this interval. More convincingly, the presence of very sparse branching indicates a trace fossil origin for these structures. These fossils are best interpreted as the products of preferential mining of inorganically generated tool marks by deposit feeders, owing to exposure of more organic‐rich muds by erosional scouring. Thus, this occurrence represents a rare instance in which trace fossils display a strong alignment parallel to inorganic sedimentary structures.     

The hydroid fossil record and analytical techniques for assessing the affinities of putative hydrozoans and possible hemichordates

Hydrozoan cnidarians are widespread in modern environments, but their polyps or hydroids, when not biomineralized, are generally rare in the fossil record. To assess the affinities of four hydrozoan taxa previously described on the basis of supposed fossils of non‐biomineralized hydroids, we re‐analysed the type specimens of these taxa using a combination of light and electron microscopic tools, including backscattered electron (BSE) scanning electron microscopy (SEM) and energy‐dispersive X‐ray spectroscopy (EDS). New morphological, ultrastructural and taphonomic data were generated for Archaeoantennularia byersi from the Devonian of Michigan, Archaeocryptolaria compacta from the Ordovician of Virginia, and Mazohydra megabertha and Drevotella proteana from the Carboniferous Mazon Creek Lagerstätte of Illinois, which are preserved as carbonaceous fossils, aluminosilicate films and iron carbonate minerals in siderite concretions, respectively. In the context of these results, we provide a review of the fossil record of non‐biomineralized hydroids, describe possible biases and changes through time in their occurrence and preservation, and evaluate the criteria commonly used to identify and interpret their fossils. Although hydroids have been reported from Phanerozoic (particularly lower Palaeozoic) rocks around the world, many putative hydroids from the Palaeozoic are poorly substantiated and may actually be hemichordates. Indeed, none of the type specimens in this study represent unequivocal hydrozoans. As shown in BSE images, metatype specimens of A. byersi possess autothecae, fusellae, stolons, stolothecae and bithecae, which decisively indicate that they are dendroid graptolites rather than hydroids. The analyses yielded no evidence that A. compacta, Mazohydra and Drevotella are hydrozoans, as their holotypes lack the diagnostic morphological, taphonomic and ecological features characteristic of purported hydroid analogues. Consequently, our results suggest that many Palaeozoic hydroids may be hemichordates and that interpretations of hydroid fossils should be tested and refined using data collected via in situ analytical techniques like BSE‐SEM and EDS.     

Macromolecular composition of Palaeozoic scolecodonts: insights into the molecular taphonomy of zoomorphs

Dutta, S., Hartkopf‐Fröder, C., Mann, U., Wilkes, H., Brocke, R. & Bertram, N. 2010: Macromolecular composition of Palaeozoic scolecodonts: insights into the molecular taphonomy of zoomorphs. Lethaia, Vol. 43, pp. 334–343. Biogeochemistry and molecular taphonomy of biopolymers of marine zoomorphs are poorly known. In order to obtain insights into this issue we report on the biogeomacromolecular composition of hand‐picked, well‐preserved scolecodonts of Ordovician, Silurian and Devonian age using micro‐Fourier transform infrared (micro‐FTIR) spectroscopy, Curie point pyrolysis‐gas chromatography‐mass spectrometry (Cupy‐GC‐MS) and tetramethylammonium hydroxide (TMAH)‐assisted thermochemolysis‐GC‐MS. The present study reveals that scolecodonts are composed of both aliphatic and aromatic moieties. The micro‐FTIR spectra of scolecodonts are characterized by aliphatic CH_x (3000–2800 and 1460–1450/cm) and CH₃ (1375/cm) absorptions and aromatic C=C (1560–1610/cm) and CH (3050/cm and 700–900/cm) absorptions. The major pyrolysis products from the scolecodonts include aromatic hydrocarbons such as alkylbenzenes, alkylnaphthalenes and alkylphenols. Aliphatic hydrocarbons are represented by a homologous series of n‐alkenes and n‐alkanes. The compounds released upon thermochemolysis with TMAH are saturated and unsaturated fatty acids (as their methyl esters), n‐alkenes/alkanes and aromatic acids (as their methyl esters). No protein/amino acid‐derived compounds have been recognized in the pyrolysates or in the thermochemolysates, and it is concluded that protein/amino acid‐related compounds, which are commonly found in the jaws of extant polychaetes, were destroyed due to diagenetic processes. Obviously, excellent morphological preservation and low thermal alteration are not paralleled by a similar degree of chemical preservation. □Biogeomacromolecules, micro‐FTIR, pyrolysis‐GC‐MS, scolecodonts, thermochemolysis‐GC‐MS.     

Microscale oxygen distribution in various invertebrate burrow walls

Profiles of dissolved oxygen were measured in pore waters of unburrowed sediment and the burrow walls of seven invertebrate dwellings. Burrows studied include those of Corophium volutator, Heteromastus filiformis, Arenicola marina, Saccoglossus bromophenolosus, Clymenella sp., Hemigrapsus oregonensis and Cirriformia luxuriosa all from mudflats in Willapa Bay, Washington. These animals comprise a range of burrow architectures ranging from simple, unlined burrows to more complex, mucous lined burrows. Oxygen penetrated unburrowed sediment between depths of 0.4–2.6 mm, whereas oxygen penetrated the burrow walls from 0.3 mm to 2.3 mm. Three groups of burrows are recognized based on the oxygen diffusive properties relative to the unburrowed sediment including those that: (1) slightly impeded oxygen penetration, (2) clearly inhibited oxygen penetration, and (3) enhanced oxygen penetration. Differences in the diffusive properties of the burrow wall are related to the burrow microstructure and presumably the microbial communities living within the burrow microenvironment. The results of this study suggest that burrow shape and burrow‐wall architecture may play an important role in controlling the diffusion of oxygen, and possibly of other dissolved gases (i.e. CO₂, H₂S). The results further demonstrate that simplified assumptions (i.e. that bioturbation uniformly enhances oxygen diffusion into suboxic and anoxic sediments), while requisite for numerical modelling, are not necessarily representative of field data.     

Revised correlation of Silurian Provincial Series of North America with global and regional chronostratigraphic units and δ13Ccarb chemostratigraphy

Cramer, B.D., Brett, C.E., Melchin, M.J., Männik, P., Kleffner, M.A., McLaughlin, P.I., Loydell, D.K., Munnecke, A., Jeppsson, L., Corradini, C., Brunton, F.R. & Saltzman, M.R. 2011: Revised correlation of Silurian Provincial Series of North America with global and regional chronostratigraphic units and δ¹³C_carb chemostratigraphy. Lethaia, Vol. 44, pp. 185–202. Recent revisions to the biostratigraphic and chronostratigraphic assignment of strata from the type area of the Niagaran Provincial Series (a regional chronostratigraphic unit) have demonstrated the need to revise the chronostratigraphic correlation of the Silurian System of North America. Recently, the working group to restudy the base of the Wenlock Series has developed an extremely high‐resolution global chronostratigraphy for the Telychian and Sheinwoodian stages by integrating graptolite and conodont biostratigraphy with carbonate carbon isotope (δ¹³C_carb) chemostratigraphy. This improved global chronostratigraphy has required such significant chronostratigraphic revisions to the North American succession that much of the Silurian System in North America is currently in a state of flux and needs further refinement. This report serves as an update of the progress on recalibrating the global chronostratigraphic correlation of North American Provincial Series and Stage boundaries in their type area. The revised North American classification is correlated with global series and stages as well as regional classifications used in the United Kingdom, the East Baltic, Australia, China, the Barrandian, and Altaj. Twenty‐four potential stage slices, based primarily on graptolite and conodont zones and correlated to the global series and stages, are illustrated alongside a new composite δ¹³C_carb curve for the Silurian. Conodont, graptolite, isotope, New York, Ontario, series, Silurian, stage.