A tale of both sides of Iapetus – upper Darriwilian (Ordovician) graptolite faunal dynamics on the edges of two continents

2011 ◽  
Vol 48 (5) ◽  
pp. 841-859 ◽  
Author(s):  
Jörg Maletz ◽  
Sven Egenhoff ◽  
Martina Böhme ◽  
Robert Asch ◽  
Katarina Borowski ◽  
...  
Keyword(s):  
North America ◽  
Shallow Water ◽  
Cold Water ◽  
Warm Water ◽  
Middle Ordovician ◽  
Iapetus Ocean ◽  
Biostratigraphic Correlation

Ordovician graptolite faunal compositions between the Laurentia and Baltica margins of the Iapetus Ocean differ considerably in the upper Darriwilian (Da 3 – Da 4; upper Middle Ordovician). Detailed investigation of a number of sections in the Table Head and Goose Tickle groups in western Newfoundland and the Elnes Formation of Norway provides important new faunal data for the interval from the Holmograptus lentus Biozone to the Dicellograptus vagus Biozone. The Nicholsonograptus fasciculatus and Pterograptus elegans biozones are introduced for the Table Head and Goose Tickle groups and can be recognized widely in North America. The characteristic, but poorly correlatable, shallow-water endemic faunas of the platform regions (Atlantic and Pacific faunal realms) grade into the cosmopolitan oceanic graptolite faunas (isograptid biofacies) and provide a means to precisely correlate cold-water and warm-water endemic graptolite faunas through transitional zones. The faunal differences between western Newfoundland and Scandinavia are less pronounced than hitherto assumed, and many faunal elements can now be recognized in both regions, allowing for a more precise biostratigraphic correlation. The paleobiogeographic differentiation of both regions has been based on few, but usually extremely common faunal elements, masking the presence of important biostratigraphic marker species.

Palynology of the Ordovician Kanosh Shale at Fossil Mountain, Utah

2015 ◽  
Vol 89 (3) ◽  
pp. 424-447 ◽  
Author(s):  
Marco Vecoli ◽  
John H. Beck ◽  
Paul K. Strother
Keyword(s):  
North America ◽  
Shallow Water ◽  
New Taxa ◽  
Middle Ordovician ◽  
Incomplete Knowledge ◽  
Late Cambrian ◽  
Freshwater Influence ◽  
Depositional Setting ◽  
Biological Differences

AbstractPalynomorph assemblages recovered from the Kanosh Shale at Fossil Mountain, Utah, are dominated by operculate acritarchs and cryptospores with minor smaller acritarchs. The present findings add new data to the largely incomplete knowledge of Ordovician acritarch assemblages from Laurentia, up to now known only from very few localities in North America. These populations contain some species in common with acritarchs from the Canning and Georgina basins in Australia and with assemblages from China; they indicate a Middle Ordovician (Dapingian-Darriwilian) age. The assemblage is lacking many typical marine acritarchs of this age, which, in combination with some cryptospores, is probably reflecting the likelihood of freshwater influence in the Kanosh Basin. This observation is congruent with previous interpretations of the depositional setting of the Kanosh Shale as a shallow water lagoon that supported the deposition of carbonate hardgrounds.Four new taxa are described: Busphaeridium vermiculatum n. gen., n. sp.; Digitoglomus minutum n. gen., n. sp.; Turpisphaera heteromorpha n. gen., n. sp.; and Vermimarginata barbata n. gen., n. sp. In addition, the abundance of operculate forms has enabled the revision and a new emendation of the genus Dicommopalla and clarification of the “opalla” complex. We also propose new and revised suprageneric taxa that emphasize inferred biological differences among acritarch genera. The Sphaeromorphitae subgroup is emended to include forms lacking sculptural elements. Two new informal subgroups are proposed: the Superornamenti and the Operculate Acritarchs. Cryptospores are abundant throughout the sections studied and they appear to be more closely related to the late Cambrian Agamachates Taylor and Strother than to Darriwilian and younger Ordovician cryptospores from Gondwana.

The brachiopod Ptychopleurella lapworthi (Davidson) from the Ordovician of Girvan, S.W. Scotland

1986 ◽  
Vol 60 (4) ◽  
pp. 845-850 ◽  
Author(s):  
D. A. T. Harper
Keyword(s):  
North America ◽  
Sedimentary Facies ◽  
Upper Ordovician ◽  
Middle Ordovician ◽  
Identity Recognition ◽  
Early Ordovician ◽  
Iapetus Ocean ◽  
Northwestern Margin

The small, distinctive, glyptorthinine brachiopod Ptychopleurella Schuchert and Cooper is widely distributed in rocks of early Ordovician to late Silurian age. Several species are known from the Barr and Ardmillan successions (middle-upper Ordovician) of the Girvan district, S.W. Scotland, one of which, ‘Orthis Lapworthi’ Davidson, has not been described in modern terms as there has been some confusion concerning its true identity. Recognition of this species of Ptychopleurella permits comparison with congeners elsewhere, strengthens the correlation of this part of the Girvan Succession with the middle Ordovician of North America, and provides a more complete record of this genus in the slope sedimentary facies of the northwestern margin of the Iapetus Ocean.

Recognition of the Trans-European Suture Zone (TESZ) by the palaeobiogeographical distribution pattern of early to middle Ordovician acritarchs

1997 ◽  
Vol 134 (5) ◽  
pp. 617-625 ◽  
Author(s):  
THOMAS SERVAIS ◽  
OLDA FATKA
Keyword(s):  
Distribution Pattern ◽  
Cold Water ◽  
Northern China ◽  
The United States ◽  
Suture Zone ◽  
Warm Water ◽  
Time Interval ◽  
Low Latitude ◽  
Middle Ordovician ◽  
Northern Border

The Tremadoc to early Llanvirn is the time interval in the Ordovician for which a global acritarch distribution pattern can be proposed. It is possible to differentiate a high latitude, cold- to temperate-water realm and a low latitude, warm-water realm. The cold-water assemblages, recorded from numerous localities at the northern border of Gondwana in the southern hemisphere, include some diagnostic morphotypes, such as Arbusculidium filamentosum, Arkonia, Aureotesta, Coryphidium-Vavrdovella, Dicrodiacrodium, Frankea and Striatotheca. Assemblages related to warm-water areas are described from Canada, the United States, northern China, Australia, and Baltica. Although a distinction of separate provinces within the cold-water and warm-water realms is difficult, the differentiation between these two units appears evident and a distinction of the assemblages from peri-Gondwana and the microfloras from Baltica is possible. This enables a recognition of the Trans-European Suture Zone in the early to middle Ordovician.

scholarly journals Graptolite and conodont faunas in Ordovician Vinini Formation, Roberts Mountains, central Nevada, demonstrate that the Roberts Mountains allochthon is not an exotic terrane

1992 ◽  
Vol 6 ◽  
pp. 97-97
Author(s):  
Stanley C. Finney ◽  
Raymond L. Ethington
Keyword(s):  
North America ◽  
Shallow Water ◽  
North American ◽  
Cold Water ◽  
Turbidity Currents ◽  
Plate Tectonic ◽  
Continental Rise ◽  
The North ◽  
North American Craton ◽  
Back Arc

Two very different plate-tectonic models have been proposed to explain the development and emplacement of the Robert Mountains allochthon (RMA) onto the North America craton during the Late Devonian-Early Mississippian Antler Orogeny. In one model, the RMA represents a far-traveled accretionary prism that migrated eastwards over a west-dipping subduction zone. In the other, the eugeoclinal strata of the RMA were deposited on the continental rise of western North America within a closed back-arc basin. Siliciclastic sediments, especially quartz sandstones, compose much of the RMA, yet knowledge of their provenance is poor even though such knowledge is essential for evaluating the two plate-tectonic models.We have recently obtained large collections of graptolites and conodonts from turbiditic quartz sandstones in the Lower Member of the Vinini Formation in the Roberts Mountains. These sandstones of lower Whiterockian age are correlative with the lower Antelope Valley Limestone that deposited on the western shelf of North America. The diverse graptolite fauna represents the oceanic isograptid fauna. However, it also includes pendent didymograptids and rooted dendroids that were restricted to shallow shelf seas. The dendroids (Cactograptus, Dendrograptus, Desmograptus, and Dictyonema) were benthic organisms, could not have lived in a deep marine setting, and are also common in shallow-water carbonate strata of western Utah. All specimens within the turbiditic quartz sandstones of the Vinini were broken before final deposition and burial, but specimens from Utah are generally complete. The diverse conodont fauna is virtually identical to that found in the lower Antelope Valley Limestone, as well as in coeval strata in western Utah. Although it includes a few deep (cold) water, cosmopolitan species, it is dominated by species that are otherwise known only from shallow water strata deposited on the North American craton.We conclude that turbidity currents transported these exotic graptolites and conodonts down from the shelf and onto the rise along with the quartz sands in which they occur. Thus, the Whiterockian quartz sandstones in the Vinini Formation must have a North American provenance just as the fossils do. This is strong evidence that 1) the RMA is not exotic to North America, 2) the eugeoclinal strata of the RMA were deposited on the western continental rise of North America and on the eastern side of a back-arc basin, and 3) the RMA was thrust onto the western shelf of North America by closure of this back-arc basin.

scholarly journals Ordovician acritarchs of China and their utility for global palaeobiogeography

2002 ◽  
Vol 173 (5) ◽  
pp. 399-406 ◽  
Author(s):  
Jun Li ◽  
Thomas Servais
Keyword(s):  
Cold Water ◽  
Southern China ◽  
Warm Water ◽  
High Latitudes ◽  
Latitudinal Distribution ◽  
Low Latitude ◽  
Middle Ordovician ◽  
Tentative Model ◽  
Latitudinal Position ◽  
Oceanic Currents

Abstract Since the 1970s, acritarch workers have recognized two distinct geographic acritarch assemblages in the Ordovician. The first assemblage occurs in the late Tremadoc in low latitude areas. This assemblage, recently redefined by Volkova [1997], has been attributed to warm-water environments. A second “Mediterranean” or “peri-Gondwanan” province, attributed to high latitudes in the southern hemisphere, can easily be recognized in late Tremadoc to Arenig acritarch assemblages. This second palaeogeographic “province”, defined by Li [1989] is distributed around the border of Gondwana in a zone reaching from Argentina through northern Africa and peri-Gondwana up to Iran, Pakistan and southern China. In the present work we propose an initial simplified, tentative model of the latitudinal distribution of selected early to middle Ordovician acritarchs. Both “provinces” are plotted on the recent palaeogeographical reconstruction of the early Ordovician of Li and Powell [2001]. It appears that the first “province” is limited to low and intermediate latitudes, i.e., to warmer water environments. However, the generally adopted interpretation that the so called “Mediterranean” or “peri-Gondwanan” geographical assemblage is principally controlled by palaeolatitudes and is considered to be typically “cold-water” has to be revised, because the distribution of this “province” appears related more to the continental arrangement along the Gondwana border than to latitudes. This distribution shows some similarities with recent investigations in Silurian acritarch palaeogeography [Le Hérissé and Gourvennec, 1995] that provides evidence that the global distribution of Silurian acritarchs is under the interdependence of continental arrangement, latitudinal position, environmental conditions and oceanic currents, and that it is not simply latitudinally controlled as previous interpretations have suggested. The Yangtze Plaform of southern China presents elements of both early to middle Ordovician “provinces”, i.e., from both the “warm-water” and the “peri-Gondwanan” geographic assemblages. The South China Plate is therefore one of the areas that shows typically mixed assemblages. Although it remains difficult to define clearly a “Baltic” province, it is important to note that between the latest Tremadoc and the early Llanvirn a clear distinction of the acritarch assemblages between peri-Gondwana and Baltica is possible.

Silurian (Llandovery) graptolites from the Bay of Exploits, north-central Newfoundland, and their geological significance

1991 ◽  
Vol 28 (10) ◽  
pp. 1534-1540 ◽  
Author(s):  
S. Henry Williams ◽  
Brian H. O'Brien
Keyword(s):  
United Kingdom ◽  
North America ◽  
Generic Level ◽  
North Central ◽  
Geological Significance ◽  
Middle Ordovician ◽  
The United Kingdom ◽  
Iapetus Ocean

Only one specimen of a Silurian graptolite has ever been recorded from Newfoundland, and it was not identifiable below generic level. The graptolite assemblage discussed and figured here, from a sequence of turbidites on Upper Black Island, north-central Newfoundland, includes the first positively identified Silurian taxa from the province, and provides the first unequivocal evidence of Silurian oceanic sedimentation in the Dunnage Zone. The graptolite taxa include Rastrites peregrinus (Barrande), Coronograptus? sp. cf. C. gregarius (Lapworth), Monograptus austerus sequens Hutt?, Orthograptus insectiformis (Nicholson), Monograptus spp. indet., "Climacograptus"? sp., and Glyptograptus? sp. This assemblage demonstrates that the strata, previously assigned to the Middle Ordovician Lawrence Harbour Formation, are actually Aeronian (middle Llandovery) in age and that the turbidites considerably postdate both the Lawrence Harbour and Point Leamington formations of the Exploits Subzone. Furthermore, the graptolite fauna is similar to that found in coeval sediments in the United Kingdom and Scandinavia but unlike any assemblages known from elsewhere in North America. This suggests the presence of open oceanic conditions, or deep marginal basins during the Llandovery hosting graptolites with European affinities, and raises the possibility that at least part of the Iapetus Ocean was still open in central Newfoundland during Early Silurian times.

Age and origin of the Boil Mountain ophiolite and Chain Lakes massif, Maine: implications for the Penobscottian orogeny

1997 ◽  
Vol 34 (5) ◽  
pp. 646-654 ◽  
Author(s):  
T. M. Kusky ◽  
J. S. Chow ◽  
S. A. Bowring
Keyword(s):  
North America ◽  
Late Ordovician ◽  
Ophiolite Complex ◽  
Middle Ordovician ◽  
Iapetus Ocean ◽  
Lower Ordovician ◽  
Mid Ocean Ridge ◽  
Back Arc ◽  
Ocean Ridge ◽  
Age Constraints

The Boil Mountain ophiolite complex of west-central Maine is widely interpreted to mark the Lower Ordovician Penobscottian suture between the Dunnage, Chain Lakes, and Gander terranes. The ophiolite consists of two distinct volcanic groups, including a lower island-arc tholeiite sequence and an upper mid-ocean-ridge basalt sequence. A new Middle Ordovician 477 ± 1 Ma U–Pb age on a tonalite sill that intrudes the lower volcanic–gabbroic sequence is younger than other ca. 500 Ma age constraints for the ophiolite and represents a maximum age for the ophiolite prior to final emplacement over gneissic rocks of the Chain Lakes massif. A comparison of ages and paleogeography of the Boil Mountain ophiolite with ophiolitic sequences in Quebec and Newfoundland indicates that the Taconian and Penobscottian orogenies and ophiolite obduction occurred simultaneously, although on different margins of the Iapetus Ocean. The Taconian ophiolite sequences were obducted onto the Appalachian margin of Laurentia during its collision with the Notre Dame – Bronson Hill belt in the Middle Ordovician, whereas the Boil Mountain ophiolite was obducted onto the Gander margin of Gondwana during its collision with the Exploits subzone – Penobscot arc of the Dunnage terrane in the Lower – Middle Ordovician. We suggest that the lower volcanic–gabbroic sequence of the Boil Mountain ophiolite represents the fore-arc ophiolitic basement to the Penobscot arc. Middle Ordovician rifting of the Penobscottian orogenic collage on the Gander margin formed a new volcanic sequence (Popelogan arc) in front of a growing back-arc basin, and erupted the upper tholeiitic sequence of the Boil Mountain ophiolite in a back-arc-basin setting. The tonalité sill formed during this event by partial melting of the lower volcanic–gabbroic sequence. Spreading in this back-arc basin (Tetagouche basin) brought a fragment of the Gander margin (Chain Lakes massif), along with an allochthonous ophiolitic cover (Boil Mountain complex) across Iapetus, where it collided with the Taconic modified margin of North America in the Late Ordovician and was then intruded by the Ashgillian Attean pluton.

A paleogeographical review of the peri-Gondwanan realm of the Appalachian orogen1This article is one of a series of papers published in this CJES Special Issue: In honour of Ward Neale on the theme of Appalachian and Grenvillian geology.

2012 ◽  
Vol 49 (1) ◽  
pp. 259-288 ◽  
Author(s):  
Jeffrey C. Pollock ◽  
James P. Hibbard ◽  
Cees R. van Staal
Keyword(s):  
North America ◽  
Large Scale ◽  
Early Carboniferous ◽  
Early Paleozoic ◽  
Middle Ordovician ◽  
Rheic Ocean ◽  
Iapetus Ocean ◽  
Appalachian Orogen ◽  
Eastern Edge ◽  
Dextral Strike Slip

The eastern edge of the Appalachian orogen is composed of a collection of Neoproterozoic – early Paleozoic domains, Avalonia, Carolinia, Ganderia, Meguma, and Suwannee, which are exotic to North America. Differences in the geological histories of these peri-Gondwanan domains indicate that each separated independently from Gondwana, opening the Rheic Ocean in their wake. Cambrian departure of Ganderia and Carolina was followed by the Ordovician separation of Avalonia and Silurian separation of Meguma. After separation in the early Paleozoic, these domains constituted the borderline between the expanding Rheic Ocean and contracting Iapetus Ocean. They were transferred to Laurentia by early Silurian closure of Iapetus and Devonian–Carboniferous closure of the Rheic Ocean during the assembly of Gondwana and Laurentia into Pangaea. The first domain to arrive at Laurentia was Carolinia, which accreted in the Middle Ordovician during the Cherokee orogeny. Salinic accretion of Ganderia occurred shortly thereafter and was followed by the Acadian accretion of Avalonia. The Acadian orogeny was immediately followed by Middle Devonian – Early Carboniferous accretion of Meguma and possibly Suwannee which led to the Fammenian orogeny. The episodicity of orogeny suggests that the present location of these domains parallels their order of accretion. However, each of these crustal blocks was translated along strike by large-scale Late Devonian – Carboniferous dextral strike–slip motion. The breakup of Pangaea occurred outboard of the Paleozoic collision zones that accreted Carolinia, Ganderia, Avalonia, Meguma, and Suwannee to Laurentia, leaving these terranes appended to North America during the Mesozoic opening of the Atlantic.

Predicting cold-water bleaching in corals: role of temperature, and potential integration of light exposure

2020 ◽  
Vol 642 ◽  
pp. 133-146
Author(s):  
PC González-Espinosa ◽  
SD Donner
Keyword(s):  
Coral Bleaching ◽  
Cold Water ◽  
Light Exposure ◽  
Light Attenuation ◽  
Florida Keys ◽  
Cold Temperature ◽  
Warm Water ◽  
Coral Tissue ◽  
Effect Of Temperature ◽  
Type I

Warm-water growth and survival of corals are constrained by a set of environmental conditions such as temperature, light, nutrient levels and salinity. Water temperatures of 1 to 2°C above the usual summer maximum can trigger a phenomenon known as coral bleaching, whereby disruption of the symbiosis between coral and dinoflagellate micro-algae, living within the coral tissue, reveals the white skeleton of coral. Anomalously cold water can also lead to coral bleaching but has been the subject of limited research. Although cold-water bleaching events are less common, they can produce similar impacts on coral reefs as warm-water events. In this study, we explored the effect of temperature and light on the likelihood of cold-water coral bleaching from 1998-2017 using available bleaching observations from the Eastern Tropical Pacific and the Florida Keys. Using satellite-derived sea surface temperature, photosynthetically available radiation and light attenuation data, cold temperature and light exposure metrics were developed and then tested against the bleaching observations using logistic regression. The results show that cold-water bleaching can be best predicted with an accumulated cold-temperature metric, i.e. ‘degree cooling weeks’, analogous to the heat stress metric ‘degree heating weeks’, with high accuracy (90%) and fewer Type I and Type II errors in comparison with other models. Although light, when also considered, improved prediction accuracy, we found that the most reliable framework for cold-water bleaching prediction may be based solely on cold-temperature exposure.

Middle Ordovician Table Head Group of western Newfoundland: a revised stratigraphy

1980 ◽  
Vol 17 (8) ◽  
pp. 1007-1019 ◽  
Author(s):  
Colin F. Klappa ◽  
Paul R. Opalinski ◽  
Noel P. James
Keyword(s):  
Carbonate Platform ◽  
Head Group ◽  
Group Status ◽  
Middle Ordovician ◽  
Iapetus Ocean ◽  
Lower Ordovician ◽  
Head Formation ◽  
New Formation

Lithostratigraphic nomenclature of early Middle Ordovician strata from western Newfound land is formally revised. The present Table Head Formation is raised to group status and extended to include overlying interbedded terrigenoclastic-rich calcarenites and shales with lime megabreccias. Four new formation names are proposed: Table Point Formation (previously lower Table Head); Table Cove Formation (previously middle Table Head); Black Cove Formation (previously upper Table Head); and Cape Cormorant Formation (previously Caribou Brook formation). The Table Point Formation comprises bioturbated, fossiliferous grey, hackly limestones and minor dolostones; the Table Cove Formation comprises interbedded lime mudstones and grey–black calcareous shales; the Black Cove Formation comprises black graptolitic shales; and the Cape Cormorant Formation comprises interbedded terrigenoclastic and calcareous sandstones, siltstones, and shales, punctuated by massive or thick-bedded lime megabreccias. The newly defined Table Head Group rests conformably or disconformably on dolostones of the Lower Ordovician St. George Group (an upward-migrating diagenetic dolomitization front commonly obscures the contact) and is overlain concordantly by easterly-derived flysch deposits. Upward-varying lithologic characteristics within the Table Head Group result from fragmentation and subsidence of the Cambro-Ordovician carbonate platform and margin during closure of a proto-Atlantic (Iapetus) Ocean.

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