%0 Journal Article %J Geological Magazine %D 2012 %T First Discovery of Early Palaeozoic Bathysiphon (Foraminifera) - Test Structure and Habitat of a 'Living Fossil' %A E. Landing %A Reyes, S. P. %A Andreas, A. L. %A Bowser, S. S. %K Avalon %K Bathysiphon %K Cape Breton Island %K Foraminifera %K Lower Ordovician %K Nova Scotia %K stercomata %K Tremadocian %B Geological Magazine %V 149 %P 1013-1022 %G eng %U http://dx.doi.org/10.1017/S0016756812000155 %R 10.1017/S0016756812000155 %0 Journal Article %J Geological Magazine %D 2012 %T Tribes Hill-Rochdale Formations in East Laurentia: Proxies for Early Ordovician (Tremadocian) Eustasy on a Tropical Passive Margin (New York and West Vermont) %A E. Landing %A Adrian, J. M. %A Westrop, S. R. %A Kroger, B. %K conodonts %K eustasy %K Laurentia %K Lower Ordovician %K New York %K trilobites %K Vermont %X

Slow subsidence and tectonic quiescence along the New York Promontory margin of Laurentia mean that the carbonate-dominated Tribes Hill and overlying Rochdale formations serve as proxies for the magnitude and timing of Tremadocian eustatic changes. Both formations are unconformity-bound, deepening–shoaling, depositional sequences that double in thickness from the craton into the parautochthonous, western Appalachian Mountains. A consistent, ‘layer cake’ succession of member-level units of the formations persists through this region. The Tribes Hill Formation (late early Tremadocian, late Skullrockian, late Fauna B–Rossodus manitouensis Chron) unconformably overlies the terminal Cambrian Little Falls Formation as the lowest Ordovician unit on the New York Promontory. It was deposited during the strong early Tremadocian, or Stonehenge, transgression that inundated Laurentia, brought dysoxic/anoxic (d/a) slope water onto the shelf and led to deposition of the Schaghticoke d/a interval (black mudstone and ‘ribbon limestone’) on the Laurentian continental slope. The uniform lithofacies succession of the Tribes Hill includes a lower sand-rich member; a middle, dark grey to black mudstone that records d/a in eastern exposures; and an upper, shoaling-up carbonate highstand facies. A widespread (12000+ km2) thrombolitic interval in the highstand carbonate suggests the New York Promontory was rimmed by thrombolites during deposition of the Tribes Hill. Offlap and erosion of the Tribes Hill was followed by the relatively feeble sea-level rise of the Rochdale transgression (new) in Laurentia, and deposition of the Rochdale Formation. The Rochdale transgression, correlated with the Kierograptus Drowning Interval in Baltica, marks a eustatic rise. The Rochdale Formation represents a short Early Ordovician interval (early late Tremadocian, middle–late Stairsian, Macerodus dianae Chron). It correlates with a depositional sequence that forms the middle Boat Harbour Formation in west Newfoundland and with the Rte 299 d/a interval on the east Laurentian slope. The Rochdale has a lower carbonate with abundant quartz silt (Comstock Member, new) and an upper, thrombolitic (Hawk Member, new) high-stand facies. Tribes Hill and Rochdale faunas are mollusc-rich, generally trilobite-poor, and have low diversity, Laurentian faunal province conodonts. Ulrichodina rutnika Landing n. sp. is rare in Rochdale conodont assemblages. Trilobites are also low in diversity, but locally form coquinas in the middle Tribes Hill. The poorly preserved Rochdale trilobites include the bathyurid Randaynia, at least two hystricurid species and Leiostegium.

%B Geological Magazine %V 149 %P 93-123 %G eng %U http://dx.doi.org/10.1017/S0016756811000598 %R 10.1017/S0016756811000598 %0 Journal Article %J Geological Magazine %D 2011 %T Left Behind--Delayed Extinction and a Relict Trilobite Fauna in the Cambrian--Ordovician Boundary Succession (East Laurentian Platform, New York) %A E. Landing %A Westrop, S. R. %A Kroger, B. %A A. M. English %K conodonts %K extinction %K Lower Ordovician %K New York %K North America %K trilobites %K upper Cambrian %X

Two completely dissimilar faunal changes occur between the Sunwaptan and Skullrockian Stages (Ptychaspid and Symphysurid ‘Biomeres’) in the uppermost Cambrian on the east Laurentian craton. An undolomitized section in the Little Falls Formation in Washington County, New York, shows a typical ‘biomere’ extinction, with highest Sunwaptan trilobites followed by the abrupt appearance of Cordylodus proavus Zone conodonts and the lowest post-extinction trilobites (Parakoldinioidia Endo) 5.0 m higher. This stage boundary interval is very condensed by comparison with coeval Great Basin and Texas sections. Approximately 70 km southwest, typical pre-extinction taxa (the catillicephalid Acheilops Ulrich and several dikelocephalid species) are shown for the first time to persist well beyond the extinction as they occur with middle C. proavus Zone conodonts (Clavohamulus elongatus or, more likely, Hirsutodontus simplex Subzone). The Ritchie Limestone member of the uppermost Little Falls Formation yields a succession of conodont faunas that spans the C. elongatusH. simplexClavohamulus hintzei Subzones (middle–upper C. proavus Zone). These data prove that the trilobites are a relict fauna that persisted into the Symphysurina Zone of the Skullrockian Stage. The massive (burrow-churned), mollusc-dominated Ritchie Limestone, with the second Upper Cambrian cephalopod locality in east Laurentia, represents an inner-shelf refugium for Sunwaptan trilobites that has not been previously encountered. Final extinction of typical Sunwaptan clades is at least locally diachronous, and a simple, genus-based approach to trilobite biostratigraphy in the Cambrian–Ordovician boundary interval is untenable. The relict fauna appears to be distinct at the species level, so it is likely that a viable, species-based biostratigraphy can be developed. Teridontus gallicus Serpagli et al. 2008 is a synonym of T. nakamurai (Nogami, 1967), and T.? francisi Landing sp. nov., with a large base and tiny cusp, is a lower C. proavus Zone form. New trilobites are Acheilops olbermanni Westrop sp. nov. and Parakoldinioidia maddowae Westrop sp. nov. The lowest Ordovician ‘Gailor Dolomite’ is a junior synonym of the Tribes Hill Formation, and the Ritchie Limestone is assigned to the top of the terminal Cambrian Little Falls Formation.

%B Geological Magazine %V 148 %P 529-557 %G eng %U http://dx.doi.org/10.1017/S0016756810000919 %R 10.1017/S0016756810000919 %0 Journal Article %J Journal of Paleontology %D 2011 %T Tremadocian (Lower Ordovician) Biotas and Sea-level Changes on the Avalon Microcontinent %A E. Landing %A Fortey, R. A. %K Avalon %K Bathysiphon %K brachiopods %K Cape Breton Island %K chitinozoans %K conodonts %K Lower Ordovician %K sea-levels %K Tremadocian %K trilobites %X

The Chesley Drive Group, an Upper Cambrian–Lower Ordovician mudstone-dominated unit, is part of the Ediacaran–Ordovician cover sequence on the North American part of the Avalon microcontinent. The upper Chesley Drive Group on McLeod Brook, Cape Breton Island (previously “McLeod Brook Formation”), has two lithofacies-specific Tremadocian biotas. An older low-diversity benthic assemblage (shallow burrowers, Bathysiphon, phosphatic brachiopods, asaphid trilobites) is in lower upper Tremadocian green-gray mudstone. This wave-influenced, slightly dysoxic facies has Bathysiphon–brachiopod shell lags in ripple troughs. The upper fauna (ca. 483 +/− 1 Ma) is in dysoxic-anoxic (d-a), unburrowed, dark gray-black, upper upper (but not uppermost) Tremadocian mudstone with a “mass kill” of the olenid Peltocare rotundifrons (Matthew)—a provincial trilobite in Avalonian North America that likely tolerated low oxygen bottom waters. Scandodus avalonensis Landing n. sp. and Lagenochitina aff. conifundus (Poumot), probable nektic elements and the first upper Tremadocian conodont and chitinozoan reported from Avalon, occur in diagenetic calcareous nodules in the dark gray–black mudstone. An upper Tremadocian transition from lower greenish to upper black mudstone is not exposed on McLeod Brook, but is comparable to a coeval green-black mudstone transition in Avalonian England. The successions suggest that late late Tremadocian (probable Baltic Hunnebergian Age) sea level was higher in Avalon than is suggested from successions on other paleocontinents. The Tremadocian sea-level history of Avalon was a shoaling–deepening–shoaling sequence from d-a black mudstone (lower Tremadocian), to dysoxic green mudstone (lower upper Tremadocian), and back to black mudstone (upper upper Tremadocian).

Scandodus Lindström is emended, with the early species S. avalonensis Landing n. sp. assigned to the emended Family Protopanderodontidae. Triangulodus Van Wamel is considered a junior synonym of Scandodus. Peltocare rotundifrons is emended on the basis of complete specimens.

%B Journal of Paleontology %V 85 %P 680-696 %G eng %U http://dx.doi.org/10.1666/10-076.1 %R 10.1666/10-076.1 %0 Journal Article %J Journal of Paleontology %D 2009 %T Cephalopods and Paleoenvironments of the Fort Cassin Formation (upper Lower Ordovician), Eastern New York and Adjacent Vermont %A Kroger, B. %A E. Landing %K Cephalopoda %K Fort Cassin Formation %K Lower Ordovician %K New York %K Ordovician Radiation %K Vermont %X

The dramatic late Early Ordovician radiation of cephalopods on tropical paleocontinents is illustrated by the diverse fauna (21 genera, 30 species) of the Fort Cassin Formation (Floian and lower Blackhillsian Stage) in northeast Laurentia. Cephalopods occur through the thin (ca. 30–65 m) depositional sequence of the Fort Cassin but are most common and diverse in mollusk-rich, trilobite-poor parts of the formation that characterize the thrombolite-bearing intervals in the shoaling part of the highstand systems tract. This lithofacies-biofacies linkage persists from the Tribes Hill and Rochdale Formations (lower and lower upper Tremadocian, and upper Skullrockian and Stairsian Stages, respectively), and suggests that the Early Ordovician radiations of cephalopods took place in shallow-marine, thrombolite reef facies of tropical carbonate platforms. These habitats differed strongly from the near-shore, peritidal habitats of the older Cambrian evolutionary radiation. Genus-level diversity and absolute abundance changed little through the Skullrockian–Blackhillsian, but morphologic diversity and body size increased dramatically by the late Early Ordovician. The morphological diversification suggests cephalopods diversified into a wider variety of macropredators and more complex late Early Ordovician ecosystems. Anrangeroceras whitehallense n. gen. and n. sp. is proposed. The following are emended: the Protocycloceratidae, Centrotarphyceras and C. seelyi, Protocycloceras and P. lamarcki, and Rudolfoceras cornuoryx. The following are indeterminate and abandoned: Baltoceras? pusillum Ruedemann, 1906; Cameroceras annuliferum Flower, 1941; Cyptendoceras whitfieldi Ulrich et al., 1944; Endoceras? champlainense Ruedemann, 1906; Wolungoceras valcourense Flower, 1964. Beekmanoceras Ulrich and Foerste, 1936 is a gastropod.

%B Journal of Paleontology %V 83 %P 664-693 %G eng %U http://www.jstor.org/stable/20627655 %R 10.1666/08-181.1 %0 Journal Article %J Journal of Paleontology %D 2006 %T Lower Ordovician Faunas, Stratigraphy, and Sea-level History of the Middle Beekmantown Group, Northeastern New York %A E. Landing %A Westrop, S. R. %K Lower Ordovician %K middle Beekmantown Group %K Tribes Hill Formation %X

The Lower Ordovician middle Beekmantown Group is a very thin carbonate platform succession on the northern New York Promontory that thickens north into the Ottawa aulacogen near Montréal. The Tribes Hill Formation (Rossodus manitouensis Zone) records the earliest Ordovician (late Skullrockian, late early Tremadocian) eustatic high that submerged Laurentia, and produced the lowest Ordovician sequence along the New York Promontory. These dolostones are succeeded in the Beekmantown, New York, area by late Tulean?–Blackhillsian transgressive systems tract quartz arenites of the lower Fort Cassin Formation (Ward Member). The “Fort Ann Formation” (middle Stairsian, upper Tremadocian) of the southern Lake Champlain lowlands (=Theresa Formation sandstones in the Ottawa graben) is absent at Beekmantown, and moderate Stairsian (late Tremadocian) eustatic rise apparently did not inundate the Beekmantown area after Skullrockian–Stairsian boundary interval offlap. Highstand carbonates of the upper Fort Cassin Formation [Sciota Member = “Spellman Formation” and “Ogdensburg Member” of the “Beauharnois Formation” in the Montréal area; designations abandoned] at Beekmantown yield diverse conodonts seemingly characteristic of the Oepikodus communisFahraeusodus marathonensis Zone (new). However, associated trilobites, particularly Carolinites tasmanensis (Etheridge, 1919), show a correlation with the upper Trigonocerca typica (trilobite) Zone of the Utah and the overlying Reutterodus andinus (conodont) Zone. This abrupt early Blackhillsian lithofacies change features the appearance of chitinozoans and conodonts known from marginal successions, and records the Laignet Point highstand (new). This highstand is recognized across Laurentia on the west Newfoundland and southern Midcontinent platforms. It is recorded on the east Laurentian continental slope by lower Oepikodus evae Zone dysoxic black mudstone in the Taconian allochthons. Taxonomic re-evaluations include Ulrichodina Branson and Mehl, 1933, with its genotype species U. abnormalis (Branson and Mehl, 1933) emend., as the senior synonym of Colaptoconus Kennedy, 1994; Eucharodus Kennedy, 1980; and Glyptoconus Kennedy, 1980. Paraserratognathus An in An et al., 1983, emend. is the senior synonym of Wandelia Smith, 1991 and Stultodontus Ji and Barnes, 1994. Tropodus Kennedy, 1980 is the senior synonym of Chionoconus Smith, 1991. The trilobite fauna of the Sciota Member includes species of Isoteloides, Benthamaspis, Acidiphorus and Carolinites, of which I. fisheri is new.

%B Journal of Paleontology %V 80 %P 958-980 %G eng %U http://dx.doi.org/10.1666/0022-3360(2006)80[958:LOFSAS]2.0.CO;2 %R 10.1666/0022-3360(2006)80[958:LOFSAS]2.0.CO;2 %0 Journal Article %J Journal of Paleontology %D 2001 %T Systematics of the Ordovician Trilobites Ischyrotoma and Dimeropygiella, With Species from the Type Ibexian Area, Western USA %A Adrain, J. M. %A Westrop, S. R. %A E. Landing %A Fortey, R. A. %K Ibexian area %K Lower Ordovician %K trilobites %K western Utah %X

Lower Ordovician sections in the type Ibexian area of western Utah contain a considerably more diverse trilobite fauna than has previously been reported. Reinvestigation of these faunas, based on new field sampling, allows a reassessment of the dimeropygid genera Ischyrotoma Raymond, 1925, and Dimeropygiella Ross, 1951. These taxa have been considered synonyms, but parsimony analysis indicates each is a well supported clade, and they are best recognized as sister genera. The number of species known from Ibex has been doubled, from four to eight, and morphological information is now available for most parts of the exoskeleton. New species include Ischyrotoma juabensis (Juab Formation), I. wahwahensis (Wah Wah Formation), Dimeropygiella fillmorensis (Fillmore Formation), and D. mccormicki (Fillmore Formation). The previously named species Dimeropygiella caudanodosa, D. blanda, and D. ovata are fully revised on the basis of abundant new material. Pseudohystricurus is a paraphyletic group, with species distributed as a basal grade of the Ischyrotoma/Dimeropygiella group.

%B Journal of Paleontology %V 75 %P 947-971 %G eng %U http://www.jstor.org/stable/1307060 %R 10.1666/0022-3360(2001)075<0947:SOTOTI>2.0.CO;2 %0 Journal Article %J Journal of Paleontology %D 1996 %T Conodonts, Stratigraphy, and Relative Sea-Level Changes of the Tribes Hill Formation (Lower Ordovician, East-Central New York) %A E. Landing %A Westrop, S. R. %A Knox, L. A. %K conodonts %K Lower Ordovician %K Tribes Hill Formation %X

Tremadocian onlap is recorded by the Tribes Hill Formation. The formation is a lower Lower Ordovician (upper conodont Fauna B Interval(?)- Rossodus manitouensis Zone) depositional sequence that unconformably overlies the Upper Cambrian Little Falls Formation. Depositional environments and stratigraphy indicate that the Tribes Hill was deposited on a wave-, not tide-, dominated shelf and that a uniform, 'layer-cake' stratigraphy is present. The deepening-shoaling sequence of the Tribes Hill includes the: 1) Sprakers Member (new; peritidal carbonate and overlying tempestite limestone and shale); 2) Van Wie Member (new; subtidal shale and limestone); 3) Wolf Hollow Member (revised; massive carbonates with thrombolitic cap); and 4) Canyon Road Member (new; glauconitic limestone and overlying evaporitic dolostone). The shoaling half-cycle of the Tribes Hill is older than a shoaling event in western Newfoundland, and suggests epeirogenic factors in earliest Ordovician sea-level change in east Laurentia. Conodont and trilobite biofacies track lithofacies, and Rossodus manitouensis Zone conodonts and Bellefontia Biofacies trilobites appear in the distal, middle Tribes Hill Formation. Twenty-four conodont species are illustrated. Ansella? protoserrata new species, lapetognathus sprakersi new species, Leukorhinion ambonodes new genus and species, and Laurentoscandodus new genus are described.

%B Journal of Paleontology %V 70 %P 656-680 %G eng %U http://www.jstor.org/stable/1306528