New camerate crinoids from the Ordovician of Scotland and Wales

2002 ◽  
Vol 93 (2) ◽  
pp. 155-161 ◽  
Author(s):  
Stephen K. Donovan ◽  
Neil Gilmour
Keyword(s):  
Morphological Features ◽  
British Isles ◽  
Insufficient Information ◽  
Upper Ordovician ◽  
Filter Feeder ◽  
Middle Ordovician ◽  
Significant Addition

ABSTRACTTwo new broad-cupped camerate crinoids are reported from the Upper Ordovician (Ashgill, Rawtheyan) Lady Burn Starfish Beds of the Girvan district, Strathclyde, SW Scotland. These represent a significant addition to the limited crinoid diversity known from the Ordovician of the British Isles. The 20-armed diplobathrid Eodimerocrinites littlewoodi gen. et sp. nov. is similar to Silurian Dimerocrinites Phillips, but lacks median ray ridges and has a distinct calyx sculpture. Camerate sp. indet. differs from E. littlewoodi in the sculpture of the dorsal cup and the arrangement of the interbrachial plates, but it preserves insufficient information for it to be further classified with confidence.New specimens of the diplobathrid gen. et sp. nov. cf Botting from the Middle Ordovician (Llanvirn, Abereiddian) of central Wales, that illustrate hitherto unknown morphological features, including a distal rhizoidal holdfast and a geniculate proximal column, suggest that this species was a rheophilic filter feeder. One specimen is one of the most complete fossil crinoids known from the Ordovician of the British Isles.

Oxygen isotope (δ18O) trends measured from Ordovician conodont apatite using secondary ion mass spectrometry (SIMS): Implications for paleo-thermometry studies

2021 ◽  
Author(s):  
Cole T. Edwards ◽  
Clive M. Jones ◽  
Page C. Quinton ◽  
David A. Fike
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Matrix Effects ◽  
Analytical Techniques ◽  
Upper Ordovician ◽  
Bulk Analysis ◽  
Middle Ordovician ◽  
Ion Mass Spectrometry ◽  
Oxygen Isotopic ◽  
Secondary Ion

The oxygen isotopic compositions (δ18O) of minimally altered phosphate minerals and fossils, such as conodont elements, are used as a proxy for past ocean temperature. Phosphate is thermally stable under low to moderate burial conditions and is ideal for reconstructing seawater temperatures because the P-O bonds are highly resistant to isotopic exchange during diagenesis. Traditional bulk methods used to measure conodont δ18O include multiple conodont elements, which can reflect different environments and potentially yield an aggregate δ18O value derived from a mixture of different water masses. In situ spot analyses of individual elements using micro-analytical techniques, such as secondary ion mass spectrometry (SIMS), can address these issues. Here we present 108 new δ18O values using SIMS from conodont apatite collected from four Lower to Upper Ordovician stratigraphic successions from North America (Nevada, Oklahoma, and the Cincinnati Arch region of Kentucky and Indiana, USA). The available elements measured had a range of thermal alteration regimes that are categorized based on their conodont alteration index (CAI) as either low (CAI = 1−2) or high (CAI = 3−4). Though individual spot analyses of the same element yield δ18O values that vary by several per mil (‰), most form a normal distribution around a mean value. Isotopic variability of individual spots can be minimized by avoiding surficial heterogeneities like cracks, pits, or near the edge of the element and the precision can be improved with multiple (≥4) spot analyses of the same element. Mean δ18O values from multiple conodonts from the same bed range between 0.0 and 4.3‰ (median 1.0‰), regardless of low or high CAI values. Oxygen isotopic values measured using SIMS in this study reproduce values similar to published trends, namely, δ18O values increase during the Early−Middle Ordovician and plateau by the mid Darriwilian (late Middle Ordovician). Twenty-two of the measured conodonts were from ten sampled beds that had been previously measured using bulk analysis. SIMS-based δ18O values from these samples are more positive by an average of 1.7‰ compared to bulk values, consistent with observations by others who attribute the shift to carbonate- and hydroxyl-related SIMS matrix effects. This offset has implications for paleo-temperature model estimates, which indicate that a 4 °C temperature change corresponds to a 1‰ shift in δ18O (‰). Although this uncertainty precludes precise paleo-temperature reconstructions by SIMS, it is valuable for identifying spatial and stratigraphic trends in temperature that might not have been previously possible with bulk approaches.

Maturation thermique et histoire de l'enfouissement et de la génération des hydrocarbures du bassin de l'archipel de Mingan et de l'île d'Anticosti, Canada

1990 ◽  
Vol 27 (6) ◽  
pp. 731-741 ◽  
Author(s):  
Rudolf Bertrand
Keyword(s):  
Carbonate Platform ◽  
Burial History ◽  
Upper Ordovician ◽  
Southeastern Part ◽  
Middle Ordovician ◽  
Oil Generation ◽  
Wide Range ◽  
History Of ◽  
Anticosti Island ◽  
Depth Of Burial

Carbonate platform sequences of Anticosti Island and the Mingan Archipelago are Early Ordovician to Early Silurian in age. With the exception of the Macasty Formation, the sequences are impoverished in dispersed organic matter, which is chiefly composed of zooclasts. Zooclast reflectances suggest that the Upper Ordovician and Silurian sequences outcropping on Anticosti Island are entirely in the oil window but that the Lower to Middle Ordovician beds of the Mingan Archipelago and their stratigraphic equivalents in the subsurface of most of Anticosti Island belong to the condensate zone. Only the deeper sequences of the southwestern sector of Anticosti Island are in the diagenetic dry-gas zone. The maximum depth of burial of sequences below now-eroded Silurian to Devonian strata increases from 2.3 km on southwestern Anticosti Island to 4.5 km in the Mingan Archipelago. A late upwarp of the Precambrian basement likely allowed deeper erosion of the Paleozoic strata in the vicinity of the Mingan Archipelago than on Anticosti Island. Differential erosion resulted in a southwestern tilting of equal maturation surfaces. The Macasty Formation, the only source rock of the basin (total organic carbon generally > 3.5%, shows a wide range of thermal maturation levels (potential oil window to diagenetic dry gas). It can be inferred from the burial history of Anticosti Island sequences that oil generation began later but continued for a longer period of geologic time in the northeastern part than in the southeastern part of the island. Oil generation was entirely pre-Acadian in the southern and western parts of Anticosti Island, but pre- and post-Acadian in the northern and eastern parts.

Flexible crinoids from the Upper Ordovician Maquoketa Formation of the northern midcontinent and the evolution of early flexible crinoids

2001 ◽  
Vol 75 (2) ◽  
pp. 370-382 ◽  
Author(s):  
James C. Brower
Keyword(s):  
New Species ◽  
North America ◽  
Late Ordovician ◽  
Upper Ordovician ◽  
Middle Ordovician

Three flexible crinoids occur in the Upper Ordovician Maquoketa Formation of Illinois, Iowa, and Minnesota:Protaxocrinus girvanensisRamsbottom, 1961,Clidochirus anebosnew species, andProanisocrinus oswegoensis(Miller and Gurley, 1894).Protaxocrinus girvanensisis also found in the Upper Ordovician of Scotland which indicates that the ocean was narrow enough to allow at least one crinoid species to cross the barrier. The Upper Ordovician of North America and Scotland also share many common crinoid genera. Both phenetic and cladistic methods result in similar phylogenies of flexible crinoids.Protaxocrinuswas derived from a cupulocrinid ancestor during the Middle Ordovician.Clidochirusevolved fromProtaxocrinusor its ancestral stock prior to the Richmondian of the Late Ordovician. The RichmondianProanisocrinusand later anisocrinids are most closely related toClidochirusor its immediate predecessor. Thus, three major lineages of flexible crinoids,Protaxocrinus(taxocrinid group),Clidochirus(icthyocrinid), andProanisocrinus(anisocrinids and homalocrinids), appeared during the Ordovician. Despite their rarity during the Ordovician, all three flexible lineages survived the Latest Ordovician extinction, whereas their more abundant and successful cupulocrinid ancestors were eliminated.

Cupulocrinid crinoids from the Middle Ordovician (Galena Group, Dunleith Formation) of northern Iowa and southern Minnesota

1992 ◽  
Vol 66 (1) ◽  
pp. 99-128 ◽  
Author(s):  
James C. Brower
Keyword(s):  
Niche Differentiation ◽  
Upper Ordovician ◽  
Average Width ◽  
Positive Allometry ◽  
Middle Ordovician ◽  
Surrogate Variable ◽  
Crown Volume ◽  
Food Particles ◽  
Anal Sac ◽  
Food Groove

Two cupulocrinids,Cupulocrinus crossmanin. sp. andPraecupulocrinus conjugans(Billings) n. gen., are known from the Middle Ordovician (Galena Group, Dunleith Formation) of northern Iowa and southern Minnesota. Various morphologic and ontogenetic features demonstrate thatPraecupulocrinusis more primitive thanCupulocrinus. The two species commonly occur together. In addition, both taxa coexisted at similar levels with stem lengths ranging from about 1.5 cm in juveniles to 15 cm in adults. Relatively complete growth sequences illustrate growth and variation and show how two related crinoids subdivided feeding niches. The crown volume provides a satisfactory surrogate variable for the size of the animal. The food-gathering system of the cupulocrinids is mainly augmented by the addition of new plates at the ends of the arms. The number of plates in the arms and the arm length exhibit positive allometry relative to crown volume, largely due to development of new branches at the arm tips. The food-gathering capacity equals the number of food-catching tube-feet multiplied by the average width of the food grooves. Food-gathering capacity is also positively allometric with respect to crown volume and the amount of tissue that must be supplied with food. Consequently, the ratio of food-gathering capacity:crown volume is either constant or declines slightly with increasing size and age. The food groove width increases throughout ontogeny so adult crinoids ate larger food particles than juveniles.Praecupulocrinus conjugans(Billings) n. gen. has more narrow food grooves thanCupulocrinus crossmanin. sp. of comparable size and age, which suggests niche differentiation based on food-particle size. The arm and tube-foot geometry indicates that both cupulocrinids utilized the same type of suspension feeding.The morphology of the anal sac and the lack of “patelloid” processes in the arms indicate thatCupulocrinus sepulchrumRamsbottom from the Upper Ordovician of Scotland belongs toDendrocrinus.

Biostratigraphy and paleobiogeography of Middle and Late Ordovician conodonts from the Langkawi Islands, northwestern peninsular Malaysia

2008 ◽  
Vol 82 (5) ◽  
pp. 957-973 ◽  
Author(s):  
Sachiko Agematsu ◽  
Katsuo Sashida ◽  
Amnan B. Ibrahim
Keyword(s):  
North Atlantic ◽  
Peninsular Malaysia ◽  
Late Ordovician ◽  
Upper Ordovician ◽  
Low Latitude ◽  
Cool Water ◽  
Middle Ordovician ◽  
Water Conditions ◽  
Unidentified Species ◽  
Assemblage Zone

The Middle and Upper Ordovician sequence of the Langkawi Islands, northwestern peninsular Malaysia, contains 20 species of conodonts belonging to 15 genera and four unidentified species, which are described and illustrated. The following four biostratigraphic zones are established for the study area: the Scolopodus striatus assemblage zone, the Periodon sp. A range zone, the Baltoniodus alobatus range zone, and the Hamarodus europaeus range zone, in ascending order. The Middle Ordovician fauna belongs to the low-latitude, warm-water Australian Province. Conodonts of the H. europaeus zone represent the HDS (Hamarodus europaeus-Dapsilodus mutatus-Scabbardella altipes) biofacies, which has been reported from the cool-water North Atlantic Faunal Region. The middle Arenigian limestones in the study area were deposited on a shallow-water shelf, whereas the late Arenigian to middle Darriwilian limestones formed in hemipelagic deeper-water conditions on an outer shelf or slope.

scholarly journals Exceptionally preserved conodont apparatuses with giant elements from the Middle Ordovician Winneshiek Konservat-Lagerstätte, Iowa, USA

2017 ◽  
Vol 91 (3) ◽  
pp. 493-511 ◽  
Author(s):  
Huaibao P. Liu ◽  
Stig M. Bergström ◽  
Brian J. Witzke ◽  
Derek E. G. Briggs ◽  
Robert M. McKay ◽  
...  
Keyword(s):  
New Genus ◽  
Impact Crater ◽  
Soft Part ◽  
Basal Bodies ◽  
Upper Ordovician ◽  
Middle Ordovician ◽  
Fine Grained ◽  
New Family ◽  
Clastic Sediments ◽  
The Common

AbstractConsiderable numbers of exceptionally preserved conodont apparatuses with hyaline elements are present in the middle-upper Darriwilian (Middle Ordovician, Whiterockian) Winneshiek Konservat-Lagerstätte in northeastern Iowa. These fossils, which are associated with a restricted biota including other conodonts, occur in fine-grained clastic sediments deposited in a meteorite impact crater. Among these conodont apparatuses, the common ones are identified asArcheognathus primusCullison, 1938 andIowagnathus grandisnew genus new species. The 6-element apparatus ofA.primuscomprises two pairs of archeognathiform (P) and one pair of coleodiform (S) elements. The 15-element apparatus ofI.grandisn. gen. n. sp. is somewhat reminiscent of the prioniodinid type and contains ramiform elements of alate (one element) and digyrate, bipennate, or tertiopedate types (7 pairs). Both conodont taxa are characterized by giant elements and the preservation of both crowns and basal bodies, the latter not previously reported in Ordovician conodont apparatuses. Comparison of the apparatus size in the Winneshiek specimens with that of the Scottish Carboniferous soft-part-preserved conodont animals suggests that the Iowa animals were significantly larger than the latter. The apparatus ofA.primusdiffers conspicuously from the apparatuses of the prioniodontidPromissumfrom the Upper Ordovician Soom Shale of South Africa although the apparatus architecture ofI.grandisn. gen. n. sp. shows some similarity to it. Based on the Winneshiek collections, a new family Iowagnathidae in Conodonta is proposed.

scholarly journals Monoceratella (Ostracoda) from the Silurian of Washington Land, North Greenland

1980 ◽  
Vol 101 ◽  
pp. 37-43
Author(s):  
P.D Lane
Keyword(s):  
Upper Ordovician ◽  
Middle Ordovician ◽  
Lower Silurian ◽  
North Greenland

Monoceratella mazos n. sp. is described from the Lower Silurian of Washington Land, western North Greenland. The occurrence, together with others from the Upper Ordovician and Devonian, emphasises the possibility of homeomorphy within the otherwise typically Middle Ordovician genus Monoceratella.

scholarly journals Early-Middle Ordovician cephalopods from Ny Friesland, Spitsbergen – a pelagic fauna with Laurentian affinities

2021 ◽  
Vol 783 ◽  
Author(s):  
Björn Kröger ◽  
Alexander Pohle
Keyword(s):  
Cladistic Analysis ◽  
Niche Differentiation ◽  
Early Growth ◽  
Morphological Features ◽  
Growth Stages ◽  
Independent Evidence ◽  
Middle Ordovician ◽  
Cosmopolitan Species ◽  
Higher Taxa ◽  
Sampling Intervals

The collection of cephalopods from eight sampling horizons within the Olenidsletta Member, Valhallfonna Formation, Floian–Dapingian, from Profilstranda and nearby Profilbekken, Ny Friesland, Spitsbergen, resulted in the detection of 31 species, 20 genera, and 12 families from the Ellesmerocerida, Endocerida, Riocerida, Dissidocerida, Orthocerida, Tarphycerida, and Oncocerida. Of these, five genera (Ethanoceras gen. nov., Hinlopoceras gen. nov., Nyfrieslandoceras gen. nov., Olenidslettoceras gen. nov., Svalbardoceras gen. nov.) and 19 species (Bactroceras fluvii sp. nov., Buttsoceras buldrebreenense sp. nov., Cycloplectoceras hinlopense sp. nov., Cyclostomiceras profilstrandense sp. nov., Deltoceras beluga sp. nov., Eosomichelinoceras borealis sp. nov., Ethanoceras solitudines gen. et sp. nov., Hemichoanella occulta sp. nov., Hinlopoceras tempestatis gen. et sp. nov., H. venti gen. et sp. nov., Lawrenceoceras ebenus sp. nov., L. larus sp. nov., Litoceras profilbekkenense sp. nov., Nyfrieslandoceras bassleroceroides gen. et sp. nov., Olenidslettoceras farmi gen. et sp. nov., Protocycloceras minor sp. nov., Proterocameroceras valhallfonnense sp. nov., Svalbardoceras sterna gen. et sp. nov., S. skua gen. et sp. nov.) are new. The diagnoses of the Cyptendoceratidae, Bactroceratidae and of Deltoceras Hyatt, 1894 are emended. Well preserved early growth stages in several species are remarkable. Turnover between the sampling horizons and between sampling intervals is high. The differences in composition, diversity and evenness of the assemblages are interpreted as reflecting changing depth and oxygenation depositional bottom conditions. The co-occurrence of endemic and cosmopolitan species is interpreted as resulting from a high vertical niche differentiation and from eustatically generated lateral shifts of facies zones. Based on calculations of phragmocone implosion depths, depositional depths of 50–130 m are plausible for the Olenidsletta Member, supporting independent evidence from biomarker signatures. Several cephalopod species of the Olenidsletta Member represent odd mosaics of morphological features of previously known cephalopods which cannot be unambiguously assigned to one of the existing cephalopod higher taxa. Results from a cladistic analysis shed new light on the early evolution of the Oncocerida and Orthocerida.

scholarly journals Five buried crater structures imaged on reflection seismic data in Saudi Arabia

GeoArabia ◽  
2014 ◽  
Vol 19 (1) ◽  
pp. 17-44
Author(s):  
Allen S. Neville ◽  
Douglas J. Cook ◽  
Abdulkader M. Afifi ◽  
Simon A. Stewart
Keyword(s):  
Saudi Arabia ◽  
Seismic Data ◽  
Surface Expression ◽  
Hydrocarbon Exploration ◽  
Magnetic Data ◽  
Recent Sediment ◽  
Upper Ordovician ◽  
Middle Ordovician ◽  
Reflection Seismic ◽  
Future Work

ABSTRACT Reflection seismic data acquired for hydrocarbon exploration in Saudi Arabia have revealed five buried crater structures ranging in diameter from 5 km to 34 km. These structures have little or no present-day surface expression and span a range of ages from Ordovician to Cenozoic. The Saqqar structure (29°35′N, 38°42″E) is 34 km in diameter and is formed in Devonian siliciclastics. The structure is partially eroded and is unconformably overlain by Upper Cretaceous and Paleogene strata up to 400 m thick. The Jalamid structure (31°27′N, 39°35″E) is 19 km in diameter at Lower Ordovician level and is infilled by Middle Ordovician sediments, at a present-day depth of 4,500 m. The Banat Baqar structure (29°07′N, 37°36″E) is 12 km in diameter at Middle Ordovician level and infilled by Upper Ordovician sediments, at a depth of 2,000 m. The Hamidan structure (20°36′N, 54°44″E) is 16 km in diameter at Paleogene level and is overlain by a thin veneer of Recent sediment. The Zaynan structure (20°23′N, 50°08″E) is 5 km in diameter and affects Triassic sediments at depth of 3,800 m, and is infilled by Jurassic strata. In addition to reflection seismic imaging, various amounts of gravity and magnetic data and drilled wells are available in or near these structures. Various models including impact cratering are discussed here for each structure. One structure (Saqqar) has yielded quartz grains with possible shock metamorphic features that, contingent on future work, may support a meteorite impact crater interpretation.

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