Bonnia-Olenellus Zone Research Articles

A NEW GENUS OF EARLY CAMBRIAN CORAL IN ESMERALDA COUNTY, SOUTHWESTERN NEVADA

Numerous Early Cambrian corals or “coralomorphs,” as they are often classified, are recorded from North America, Australia, and Siberia. A new Early Cambrian coral, Harklessia yuenglingensis n. gen. and sp., is found in conjunction with archaeocyathan-microbial reefs in Esmeralda County, southwestern Nevada. The coral-bearing reefs are within quartzic, trilobite-rich packstone beds in the upper portion of the Harkless Formation (Bonnia–Olenellus Zone). Coralla are constructed by subpolygonal to polygonal, cerioid, close-packed corallite tubes. Coralla average 12 cm in height by 18 cm in diameter with individual corallite tubes ranging from 1.2 to 3.2 mm in diameter. Corallites are greater than 25 mm in length. Septa and tabulae are not present.Many of the Early Cambrian corals previously described have attributes of the class Anthozoa and subclass Zoantharia, with some specific similarities to tabulate corals. Harklessia yuenglingensis is placed confidently within the class Anthozoa, subclass Zoantharia because its morphological characteristics indicate an affinity to true corals, but whether H. yuenglingensis is a tabulate coral remains uncertain.

Early Cambrian Appalachian Archaeocyaths: Further age constraints from the fauna of New Jersey and Virginia, U.S.A.

Abstract New data allow us to correlate the Early Cambrian archaeocyathan faunas of the Appalachian (eastern)and Cordilleran (western) faunal provinces of Laurentia. The precise relationships of fossil assemblages between these provinces have hitherto been controversial, with the correlation of the Elliptocephala asaphoides Fauna posing particular problems. New and revised data (including the new taxa Sekwicyathus tillmani nov. sp. Debrenne & A. Zhuravlev and Archaeosycon balsami nov. sp. Debrenne & A. Zhuravlev on archaeocyathan assemblages from the Appalachians New Jersey and Virginia allow correlation of these assemblages to the middle Bonnia-Olenellus Zone of the Pacific Laurentia (Late Botoman) and the Elliptocephala asaphoides Fauna with the middle-upper Bonnia-Olenellus Zone (Late Botoman-Early Toyonian). The Appalachian archaeocyathan assemblages are not endemic but originated from archaeocyaths of the Pacific Region in or near the Middle Botoman; then, during the Middle Botoman-Late Botoman, they migrated northward along the Appalachian margin of Laurentia (in term of modern coordinates). We discuss here the development and the extent of influence of the Hawke Bay regressive event, and the pattern of archaeocyathan migration as the Appalachian margin of Laurentia drifted northward into equatorial latitudes.

A revised chronostratigraphy for the lower Durness Group

Synopsis The significant breaks proposed by previous researchers in the Cambro-Ordovician succession of north-western Scotland to explain the absence of Mid- and Late Cambrian faunas cannot be justified by field evidence. Moreover, comparison with the once contiguous succession of western Newfoundland suggests that the Scottish succession contains both Middle and Upper Cambrian strata. Age-diagnostic faunas from the Early Cambrian Bonnia–Olenellus Zone in both sequences allow the upper Forteau Formation and the lower Hawke Bay Formation of western Newfoundland to be biostratigraphically correlated with the lithologically similar Fucoid Beds and Salterella Grit, and with the basal dolostones of the Ghrudaidh Formation, in north-western Scotland. Similarly, Early Canadian cephalopods and matching lithostratigraphy allow the correlation of the Scottish Lower Ordovician Sailmhor Formation with the Watts Bight Formation in western Newfoundland. These benchmarks, together with the close similarities of lithostratigraphy, facies, faunal trends and patterns of cyclicity, allow the Eilean Dubh Formation of north-western Scotland to be correlated with the dolostones of the Upper Cambrian Petit Jardin and Berry Head formations of the interior shelf of western Newfoundland. The middle and upper Ghrudaidh Formation can also be correlated with the Middle Cambrian Bridge Cove Member of the upper part of the Hawke Bay Formation and the overlying Upper Middle Cambrian March Point Formation, suggesting that the Cambrian succession in north-western Scotland is largely continuous.

Calcaires à Archéocyathes du Cambrien inférieur du Nord de la Colombie britannique (Canada). Implications paléogéographiques et précisions sur l'extension du continent Américano-Koryakien

Upper Precambrian and Cambrian sections of the northern British Columbia (Cassiar, Omineca and RockyMountains) yield a rich material suitable for regional paleogeography and Lower Cambrian archaeocyath studies. Research on archaeocyath and coralomorphs assemblages distributed on both sides of the Rocky Mountain Trench (RMT) result in defining a dextral movement of 400–450 km along the Trench, from Cretaceous to Eocene. Within the limits of each block, succesive facies are observed, on which paleogeographic reconstructions of Northern British Columbia and adjacent areas at the end of the Precambrian are based. Red beds with proximal characteristics prevailed; they were replaced by a beach facies of ubiquitous orthoquartzites. At, or near, the base of the orthoquartzites is apparently situated the transition between Precambrian and Cambrian. At the very beginning of the Cambrian, environmental conditions were generaly similar, but changed toward the South and the West being replaced by deeper water characterized by the formation of pelitic dark shales and sandstones. Close to the RMT, an emersive tendancy is observed. Hematitic red beds and coarse conglomerates appearing along the mountains from the Cassiars to the Cariboos indicating a marine regression. The end of the Fallotaspis zone and the beginning of the Nevadella zone (or, in term of archaeocyaths, the interval between the Ethmophyllum whitneyi/Sekwicyathus nahanniensis zones and the Claruscoscinus fritzi/Metacyathellus caribouensis zone), partly correspond to the initial formation of the three distinctive facies belts (outer and inner detrital, middle carbonate). A rapid small scale transgression occured at the beginning of the Bonnia-Olenellus zone (the Upper Claruscoscinus fritzi/Metacyathellus caribouensis and Pycnoidocoscinus? serratus/Tabulaconus kordeae-archaeocyath zones) and was accompanied by a considerable terrigenous input. During the second half of the Bonnia-Olenellus zone (i.e. Archaeocyathus atlanticus and Tegerocyathus greenlandensis/Pycnoidocyathus pearylandicus archaeocyath zones), a migration of the different facies to the West is observed. The coeval archaeocyath assemblages could have been slightly modified perpendicularly to the middle carbonate belt, but this problem needs further investigations. Presently, it is noteworthy that the biohermal archaeocyath assemblages from the proximal part of the outer detrital belt (Gataga River) resembles the eastern Alaska and the Mackenzie Mts assemblages while the coeval assemblage from the middle carbonate belt (Kechika Mts) contains elements recorded in South British Columbia and Washington State. On the whole, the North American archaeocyath assemblages are remarkable for their uniformity over the whole craton periphery, from Alaska and the Mackenzie Mountains to the Great Basin and Sonora (Mexico); later throughout Appalachians they reach western Newfoundland and Labrador. The whole region, as well as some terranes of Koryakia (North sibirian Far East), appears to be a single American-Koryakian archaeocyath Province, characterized by a common zonal scale as defined above from the oldest to the more recent one.

New archaeocyathan occurrences in the upper Harkless Formation (Lower Cambrian of western Nevada)

A newly discovered assemblage of archaeocyathans, dominated by the unusual genus Retilamina, occurs in outcrops of the upper Harkless Formation in Esmeralda County, Nevada. These rock units have been correlated with the Saline Valley Formation in the Bonnia–Olenellus Zone (late Early Cambrian) of eastern California, making this the youngest known occurrence of archaeocyathans in the White–Inyo region.Although the assemblage contains a variety of different organisms (including the alga Renalcis, trilobite and echinoderm debris, bivalves?, and Chancelloria spines), it is dominated by archaeocyathans. Diplocyathellus, a conical form with a complex inner wall, is the only genus of regular archaeocyathan in the assemblage. The irregular archaeocyathans Arrythmocricus and Metaldetes exhibit dendroid branching and cylindroconical morphologies, respectively. A third irregular, Retilamina debrennei n. sp., is an atypical archaeocyathan with a sheetlike or shallow convex dome morphology. Retilamina formed natural cavities that sheltered cryptobionts. Unlike coelobiont communities reported from other Lower Cambrian cavities where the diversity of the supported biota is relatively high, the Harkless cavities contain only the alga Renalcis. While the undersurfaces of Retilamina are consistently encrusted by Renalcis, the upper, exposed surfaces typically lack epibionts. Similar morphologies and associations for Retilamina have been reported from bioherms and biostromes from southern Labrador and western Newfoundland. Unlike most archaeocyathans, Retilamina had a solitary, free-lying life habit. Retilamina's broad base and low profile provided stability in episodically turbulent conditions or on biologically disturbed substrates.This occurrence demonstrates that the disappearance of archaeocyathans from the stratigraphic record of the southern Great Basin in the late Early Cambrian is a paleoecological artifact. Archaeocyathans were extant in the region in the late Early Cambrian but the habitats conducive to archaeocyathan growth or preservation are, for the most part, not represented in the preserved strata.

The small shelly fossil Mongolitubulus from the Lower Cambrian of central North Greenland

The problematic small shelly fossil Mongolitubulus Missarzhevsky, 1977 is reported from the Henson Gletscher Formation of late Early Cambrian age (Bonnia-Olenellus Zone) in southem Freuchen Land, central North Greenland. Mongolitubulus is described from strata of similar Early Cambrian age (Botomian) in Mongolia and Kazakhstan, and is also reported from Antarctica. The Greenland Mongolitubulus is the first record of the genus from the North American continent.

The status of Salterella as a Lower Cambrian index fossil

In the North American Cordillera there is strong evidence that Salterella is restricted to the medial part of the Bonnia–Olenellus Zone. Reported younger and older occurrences are attributed to either stratigraphic error or misidentification. An unnamed genus with a superficial resemblance immediately postdates Salterella, but it lacks an inner laminar cone. In the Cordillera Salterella occurs in inner detrital and middle carbonate belt strata that were deposited in the upper half of Grand Cycle B and the lower half of Grand Cycle C.In and near the Appalachian Mountains of North America and in Greenland, Spitsbergen, and Scotland, occurrences of Salterella are consistent with a medial Bonnia–Olenellus Zone age; however, this cannot be as rigorously tested as in the Cordillera, because of fewer taxa associated with the genus and in super- and subjacent strata. Outer detrital (basinal) strata of the Taconic Allochthon contain Salterella, but it is uncertain whether the fossils are of local or derived origin.Speculations that Campitius titanius Firby and Durham of California belongs in the genus Salterella are doubtful, and C. titanius is clearly older. The relationship between Salterella and Volborthella and their relative ages within the Early Cambrian are still unclear.

Lidaconus palmettoensisn. gen. and sp.: an enigmatic Early Cambrian fossil from western Nevada

Lidaconus palmettoensisn. gen. and sp. is a recently discovered fossil from the Lower Cambrian Harkless Formation (Bonnia–OlenellusZone) in Esmeralda County, Nevada. The conoidal fossils were originally calcareous and have been replaced by silica. The cones are distinctive in their consistent morphology, the presence of weak annulations, and the lack of any internal structures such as septa, tabulae, or dissepiments. Because of the paucity of diagnostic characters due to the simple morphology and the lack of original microstructure, taxonomic affinities are uncertain.

Early Cambrian biogeography in the North Atlantic region

A model of Early Cambrian trilobite biogeography in the North Atlantic region (Theokritoff 1979. Lethaia 12, 281–295) is reviewed and modified in the light of new data. The presence of Wanneria in conglomerates bearing the Elliptocephala asaphoides fauna strengthens correlation of the E. asaphoides fauna as well as, by implication, the upper part of the Calluvia Zone with the middle part of the Bonnia-Olenellus Zone. The faunas of the Bastion Formation of East Greenland and of the Devil's Cove Limestone of northern Newfoundland are reinterpreted as shelf faunas. Additional occurrences of Archaeocyatha are noted in Spain and northwest Scotland but reports of Archaeocyatha in northern Norway and East Germany are not authenticated. Neither Salterella nor ‘Volborthella’ are now recognized as characteristic of any trilobite province. Although Ordovician acritarch provinces show congruence with trilobite provinces, available data on Early Cambrian plankton are not sufficient to support algal provincialism. Interpretation of the geological record suggests that the Early Cambrian lapetus Ocean was stratified with a well-mixed oxygenated zone overlying a phosphate-rich oxygen minimum zone and that the Elliptocephala asaphoides fauna should be reinterpreted as a warm-water fauna.

Evolution of a Mixed Carbonate/Terrigenous Platform: Lower Cambrian Continental Terrace Wedge of Mackenzie Mountains, Northwest Territories, Canada: ABSTRACT

Rocks of the Sekwi Formation and underlying siltstones of G.S.C. units 10A and 13 exposed in the western Mackenzie Mountains define a continental terrace wedge that evolved during the Early Cambrian on the northwestern flanks of the North American continent. Growth of the continental terrace wedge can be categorized by three phases of platform up-, out- and in-building. Phase 1--Continuous out- and up-building, and evolution from a ramp to a platform configuration. Growth culminated in middle and upper Nevadella zone rocks with prominent karst surfaces, abundant intraclast pebbles in oolite shoal deposits and a switch in composition of slope and fan deposits from carbonates to terrigenous clastics. Phase 2--Coincided with transgression of the shelf near the Nevadella and onnia-Olenellus zone boundary. Maximum platform out-building occurred at this time and climaxed with subaerial exposure of mid-Bonnia-Olenellus zone rock. Slope deposits changed from carbonate to terrigenous sedimentation. Phase 3--Renewed slow up- and in-building that led to eventual drowning of the platform by latest Bonnia-Olenellus zone time. Sedimentation patterns on this platform are reciprocal. Periods of sea-level highstand are characterized by abundant limestones, whereas periods of sea-level lowstand are marked by terrigenous influxes. These two stages of sea-level stand are highlighted in compositional differences of carbonate breccia deposits. During sea-level highstands, breccias contain predominantly ribbon and nodular limestone clasts. They reflect conditions of early lith fication of the sea floor and non-equilibrium compaction of these deposits with subsequent sliding and downslope transport. In contrast during sea-level lowstands breccias consist preferentially of shelf and shelf-margin derived clasts. End_of_Article - Last_Page 590------------

Lower Cambrian cavity-dwelling endolithic (boring) sponges

In the Lower Cambrian Forteau Formation (middle Bonnia–Olenellus zone) of southern Labrador, cavities in archaeocyath patch reefs contain preserved coelobiontic endolithic sponges. Scallops and carbonate chips produced by sponge boring, spicules, and preserved endolithic sponge body fossils all point to the presence of endolithic sponges in Lower Cambrian reef cavities.The oldest previously described endolithic sponges are Early Ordovician in age and the oldest previously known reef interior bioerosion is Middle Ordovician in age. The presence of endolithic sponges in reef cavities of the Forteau Formation therefore extends both the record of endolithic sponges and of reef interior bioerosion from the Ordovician to the upper Lower Cambrian.

New Cambrian faunas from Peary Land, eastern North Greenland

Early, Middle and Late Cambrian faunas from Peary Land, eastern North Greenland, are briefly documented. The Early Cambrian faunas of the lower Brønlund Fjord Group are assigned to the Bonnia-Olenellus Zone, although olenellids from the underiying Buen Formation may be older. Strata from the upper Brønlund Fjord Group with Middle Cambrian faunas are seemingly separated from the Lower Cambrian by a discontinuity, without representation of early Middle Cambrian zones. Faunas from lower beds of the overlying Tavsens Iskappe Group span the Middle-Late Cambrian boundary. Upper beds ofthe Tavsens Iskappe Group are assigned to the Late Cambrian, but corroborative faunal evidence is not yet available.

Cavity‐dwelling organisms in Lower Cambrian patch reefs from southern Labrador

An intact and well-preserved biota of cavity-dwelling organisms (coelobionts) of early Cambrian age is found within growth-framework cavities in archaeocyathid patch reefs of the lower Forteau Formation (upper Bonnia-Olenellus Zone) of southern Labrador. The biota was diverse, and consisted of encrusting and vagrant organisms. Renalcis, a Renalcis-like form, Epiphyton, Girvanella, and Serligia, all lived attached to walls and roofs of the cavities; other attached forms were Bija, Archaeotrypa, and two types of Wetheredella, an agglutinated foraminifer. Other organisms, including trilobites, probable calcareous ostracodes, brachiopods, echinoderms, and worms, as well as fungi, are also found preserved within the cavities. The structure of the coelobiontic community is surprisingly modern; it indicates that as early as the Lower Cambrian coelobiontic organisms were well-established in reefs, and were an important part of the reef community as a whole.

Archaeocyatha from New Jersey: Evidence for an intra-Cambrian unconformity in the north-central Appalachians

Research Article| December 01, 1976 Archaeocyatha from New Jersey: Evidence for an intra-Cambrian unconformity in the north-central Appalachians Allison R. Palmer; Allison R. Palmer 1Department of Earth and Space Sciences, State University of New York, Stony Brook, New York 11794 Search for other works by this author on: GSW Google Scholar Alexei Yu. Rozanov Alexei Yu. Rozanov 2Geological Institute, Academy of Sciences, Moscow, USSR Search for other works by this author on: GSW Google Scholar Author and Article Information Allison R. Palmer 1Department of Earth and Space Sciences, State University of New York, Stony Brook, New York 11794 Alexei Yu. Rozanov 2Geological Institute, Academy of Sciences, Moscow, USSR Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1976) 4 (12): 773–774. https://doi.org/10.1130/0091-7613(1976)4<773:AFNJEF>2.0.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Allison R. Palmer, Alexei Yu. Rozanov; Archaeocyatha from New Jersey: Evidence for an intra-Cambrian unconformity in the north-central Appalachians. Geology 1976;; 4 (12): 773–774. doi: https://doi.org/10.1130/0091-7613(1976)4<773:AFNJEF>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Archaeocyathids from the lower few metres of the Leithsville Formation in New Jersey correlate with faunas of the Forteau Formation of early Bonnia-Olenellus zone age [ Lenian (=Botomian) or early Elankian ] in Labrador and Newfoundland. The absence of younger Lower Cambrian regressive clastics known throughout most of the Appalachian region strongly suggests the existence of a previously unsuspected major unconformity within the Leithsville and equivalent carbonates of the thin Lower Cambrian sequences from eastern Pennsylvania to northern Massachusetts. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Lower and Early Middle Cambrian Formations near Mount Robson, British Columbia and Alberta

Five formations and part of a sixth were examined in order to resolve conflicting reports as to their age and lateral relationship. The formations are redescribed at their type sections and equivalent strata are described at a control section. It is concluded that the Lower Cambrian Mural, Mahto, and Hota Formations and the Middle Cambrian Chetang Formation are valid and that the Tah (= Mural) and Adolphus (= Hota) Formations should be suppressed. The boundary between the Nevadella and Bonnia-Olenellus Zone falls within the middle unit of the Mural. The Lower – Middle Cambrian boundary is located at or very near the contact between the Hota and overlying Chetang Formation. This is a sharp lithologic contract, but no physical evidence of an unconformity was noted.