scholarly journals Logan Medallist 1. Seeking the Suture: The Coast-Cascade Conundrum

2014 ◽  
Vol 41 (4) ◽  
pp. 379 ◽  
Author(s):  
Jim W.H. Monger
Keyword(s):  
North America ◽  
Middle Jurassic ◽  
Lower Mantle ◽  
Average Velocity ◽  
Late Jurassic ◽  
Canadian Cordillera ◽  
Coast Mountains ◽  
The Core ◽  
Seismic Anomaly ◽  
Eastern Seaboard

The boundary between rocks assigned to the Intermontane superterrane in the interior of the Canadian Cordillera and those of the Insular superterrane in the westernmost Cordillera of British Columbia and southeastern Alaska lies within/along the Coast Mountains, in which is exposed the core of an orogen that emerged as a discrete tectonic entity between 105 and 45 million years ago. Evidence from the Coast Mountains and flanking areas indicates that parts of the Intermontane superterrane (in Stikinia and Yukon-Tanana terranes) were near those of the Insular superterrane (Wrangellia and Alexander terranes) by the Early Jurassic (~180 Ma). This timing, as well as paleobiogeographic and paleomagnetic considerations, appears to discount a recent hypothesis that proposes westward-dipping subduction beneath an intra-oceanic arc on Insular superterrane resulted in arc-continent collision and inaugurated Cordilleran orogenesis in the Late Jurassic (~146 Ma). The hypothesis also relates the subducted ocean that had separated the superterranes to a massive, faster-than-average-velocity seismic anomaly in the lower mantle below the eastern seaboard of North America. To create such an anomaly, subduction of the floor of a large ocean was needed. The only surface record of such an ocean in the interior of the Canadian Cordillera is the Cache Creek terrane, which lies within the Intermontane superterrane but is no younger than Middle Jurassic (~174 Ma). This terrane, together with the probably related Bridge River terrane in the southeastern Coast Mountains, which is as young as latest Middle Jurassic (164 Ma) and possibly as young as earliest Cretaceous (≥ 130 Ma), appear to be the only candidates in Canada for the possible surface record of the seismic anomaly.  SOMMAIRELa limite entre les roches assignées au Superterrane d’intermont de l’intérieur des Cordillères canadiennes et celles du Superterrane insulaire dans la portion la plus à l’ouest de la Cordillère de Colombie-Britannique et du sud-est de l’Alaska se trouvent dans et au long de la Chaîne côtière, au sein de laquelle affleure le noyau d’un orogène qui est apparu comme entité tectonique distincte entre 105 et 45 millions d’années.  Des indices de la Chaîne côtière et des régions environnantes montrent que des portions du Superterrane d’intermont (dans les terranes de Stikinia et de Yukon-Tanana) se trouvaient alors près de celles du Superterrane insulaire (terranes de Wrangellia et d’Alexander) au début du Jurassique (~180 Ma).  Cette chronologie, ajoutée à certains facteurs paléobiogéographiques et paléomagnétiques semblent discréditer une hypothèse récente voulant qu’une subduction à pendage ouest sous un arc intra-océanique sur le Superterrane insulaire résultait d’une collision entre un arc et le continent, initiant ainsi l’orogénèse de la Cordillère à la fin du Jurassique (~146 Ma).  Cette hypothèse relie aussi l’océan subduit qui séparait les superterranes à une anomalie de vitesse sismique plus rapide que la normale dans le manteau inférieur sous le littoral maritime oriental de l’Amérique du Nord.  Pour créer une telle anomalie, la subduction du plancher d’un grand océan était nécessaire.  La seule indication de surface de l’existence d’un tel océan à l’intérieur de la Cordillère canadienne est le terrane de Cache Creek qui, bien qu’il se trouve dans le Superterrane d’intermont, est plus ancien que le Jurassique moyen (~174 Ma).  Ce terrane, avec son équivalent probable de Bridge River dans le sud-est de la Chaîne côtière, qui est aussi jeune que la fin du Jurassique (164 Ma) et peut-être aussi jeune que le début du Crétacé (≥ 130 Ma), semblent être les seuls candidats au Canada offrant des vestiges en surface de cette anomalie sismique. 

scholarly journals A review of the fossil record of non-baenid turtles of the clade Paracryptodira

2019 ◽  
Author(s):  
Walter G. Joyce ◽  
Jérémy Anquetin
Keyword(s):  
North America ◽  
Middle Jurassic ◽  
Fossil Record ◽  
Late Jurassic ◽  
Feeding Strategies ◽  
Aquatic Environments ◽  
Taxonomic Review ◽  
Nomina Invalida ◽  
Nomina Dubia

The fossil record of non-baenid paracryptodires ranges from the Late Jurassic (Kimmeridgian) tothe Paleocene of North America and Europe only. Earlier remains may be present as early as the Middle Jurassic (Bathonian). Only a single dispersal event is documented between the two continents following their breakup during the Cretaceous in the form of the appearance of the Compsemys lineage in the Paleocene of France. Non-baenid paracryptodires were restricted to freshwater aquatic environments, but display adaptations to diverse feeding strategies consistent with generalist, gape-and-suction, and hypercarnivorous feeding. Current phylogenies recognize two species rich subclades within Paracryptodira, Baenidae and Pleurosternidae, which jointly form the clade Baenoidea. A taxonomic review of non-baenid paracryptodires concludes that of 34 named taxa, 11 are nomina valida, 15 nomina invalida, and 8 nomina dubia.

The role of Central Asia in dinosaurian biogeography

1993 ◽  
Vol 30 (10) ◽  
pp. 2002-2012 ◽  
Author(s):  
Dale A. Russell
Keyword(s):  
North America ◽  
Central Asia ◽  
Early Cretaceous ◽  
Late Cretaceous ◽  
Middle Jurassic ◽  
Late Jurassic ◽  
Late Triassic ◽  
Globally Distributed ◽  
Northern And Southern Hemispheres

Dinosaurian biogeography may have been largely controlled by the Mesozoic fragmentation of Pangea and the reassembly of its fragments into a new, boreal supercontinent (Laurasia). Although Late Triassic and Early Jurassic dinosaurs were globally distributed, Chinese assemblages were dominated by endemic forms from Middle Jurassic into Early Cretaceous time. The affinities of Aptian – Albian immigrants to Asia were strongest with North America and Europe rather than Gondwana, indicating that the northern and southern hemispheres had by then attained their biogeographic identity. This distinctiveness was maintained through Cretaceous time. Europe seems to have been a buffer area between Paleolaurasia and Gondwana; of the northern continents it was the most strongly influenced by Gondwana dispersants. Late Jurassic dinosaur assemblages in North America exhibited Gondwana affinities, but by Late Cretaceous time they were dominated by forms of Asian ancestry.

scholarly journals Origin and evolution of turiasaur dinosaurs set by means of a new ‘rosetta’ specimen from Spain

2020 ◽  
Vol 191 (1) ◽  
pp. 201-227
Author(s):  
Rafael Royo-Torres ◽  
Alberto Cobos ◽  
Pedro Mocho ◽  
Luis Alcalá
Keyword(s):  
North America ◽  
19Th Century ◽  
Early Cretaceous ◽  
Middle Jurassic ◽  
Late Jurassic ◽  
Postcranial Skeleton ◽  
Early 19Th Century ◽  
Origin And Evolution ◽  
Character Variation ◽  
The Usa

Abstract Turiasauria is a non-neosauropod eusauropod clade of dinosaurs known since 2006, when the description of Turiasaurus was published. This group, including Losillasaurus, was originally thought to have been restricted to the Late Jurassic of Spain. However, over the last decade, our knowledge of this group has improved with the discovery of new taxa such as Zby from the Portuguese Late Jurassic, Tendaguria from the Tanzanian Late Jurassic and Mierasaurus and Moabosaurus from the Early Cretaceous of the USA. Here, we describe a new specimen of Losillasaurus from Spain, which allows us to better understand the character variation in the cranial and postcranial skeleton. The review of some sauropod fauna of Madagascar, and inclusion of some specimens of Turiasauria, suggest that this clade might have arisen in the Middle Jurassic. According to our phylogenetic results, a specimen found in the early 19th century in Madagascar is shown to be the oldest and only member of Turiasauria represented in the Middle Jurassic thus far. This is named Narindasaurus thevenini gen. & sp. nov.. Turiasauria is thus known from the Middle Jurassic in Pangaea, diversified in the Late Jurassic in Gondwana and Laurasia, and dispersed during the Early Cretaceous to North America.

scholarly journals China and the lost worlds of the dinosaurian era

1992 ◽  
Vol 6 ◽  
pp. 257-257
Author(s):  
Dale A. Russell
Keyword(s):  
North America ◽  
South America ◽  
Middle Jurassic ◽  
Late Jurassic ◽  
Southern Europe ◽  
Eastern Asia ◽  
Low Latitude ◽  
East Indies ◽  
European North ◽  
Low Diversity

What is known of dinosaurian biogeography suggests a centre of evolution first on a fragmenting Pangea-Gondwana and then on a consolidating Laurasia. By Cretaceous time members of Gondwanan low-latitude abelisaur-titanosaur assemblages often bore “back-fans,” while those in polar latitudes were relictual and/or highly derived. The time of last contact between South America and Africa is not well constrained, but links to Antarctica continued beyond the end of the Cretaceous. Many Gondwanan tetrapods appear to have waif-dispersed to Laurasia across southern Europe; few crossed in the opposite direction until the end of the period. Laurasian assemblages were then typically dominated by tyrannosaurids and hadrosaurids.Land masses (“lost worlds”) periodically became isolated from Gondwana-Laurasia. (1) Eastern Asia was isolated between middle Jurassic through Neocomian time, although related temnospondyls and carnosaurs may have co-existed in Austral regions. Mamenchisaurs were the dominant giant terrestrial herbivores, while whip-tailed diplodocids filled the same role in Pangea. Groups of European-North American affinity then replaced many Asian endemics in a manner reminiscent of the Neogene mammalian turnover in South America. (2) In North America. Late Jurassic dinosaur assemblages exhibited Gondwana affinities, but by Late Cretaceous time they were dominated by forms of Asian ancestry. The apparent low diversity of Aptian-Albian dinosaur assemblages and absence of well-marked endemism may have been the result of a brief period of isolation. (3) European archipelagos were a filter bridge between northern lands and Gondwana analogous to the East Indies, which separate comparably different modern biotas in southeast Asia and Australia. (4) During Barremian time India probably hosted an polar dinosaurian assemblage, but low-latitude Gondwana forms (abelisaurids, titanosaurids) were present during at least part of this interval. Isolation ended with the immigration of northern taxa in Maestrichtian time.Underexplored Mesozoic horizons of great biogeographic interest include (1) the Middle Jurassic-Neocomian of China for microvertebrate materials, (2) the pre-Maestrichtian Cretaceous of India, and (3) the post-Cenomanian of Africa, Australia and Antarctica. Paradoxically, the two recently discovered dinosaurian specimens of the latter age in Antarctica, which represent about as much biogeographic information as all described materials of similar age from Africa combined (none are known from Australia), are presently referred to families with Laurasian distributions.

The Canadian Cordillera, the Hellenides, and the Sea-Floor Spreading Theory

1972 ◽  
Vol 9 (6) ◽  
pp. 709-743 ◽  
Author(s):  
Jean Dercourt
Keyword(s):  
Pacific Ocean ◽  
Oceanic Crust ◽  
Continental Margin ◽  
Middle Jurassic ◽  
Late Jurassic ◽  
Late Triassic ◽  
Canadian Cordillera ◽  
Transform Faults ◽  
Sea Floor ◽  
Sea Floor Spreading

The theory of plate tectonics is applied to the tectonic evolution of the Hellenides and the Canadian Cordillera. In the Hellenides a Tethyan zone of sea-floor spreading developed within the continental crust during Triassic time and functioned until the end of the Middle Jurassic. It led to the formation of two plates, each with continental and oceanic segments, that were separated in some places by accreting plate margins and in others by transform faults. In Late Jurassic time the mid-Tethyan ridge became inactive as new ridges developed in the Atlantic Ocean. From Late Jurassic to Recent time, Tethyan oceanic crust largely disappeared under one of the cratons. The chronology of tectonic events in the Hellenides corresponds well with that of sea-floor spreading in the Atlantic.Four periods of sea-floor spreading were involved in the formation of the Canadian Cordillera: (1) a Silurian? to Early Devonian period when an Archeo-Pacific Ocean separated the Canadian craton with a stable sedimentary margin from a volcanic archipelago; (2) a Middle Devonian to Permian period when the extinct volcanic archipelago was bounded to the west by a spreading Paleo-Pacific Ocean, and to the east by a tectonic contact which was consuming Archeo-Pacific oceanic crust; part of this crust was obducted over the continental margin; (3) a Late Triassic to Middle Jurassic period when a second volcanic archipelago separated a spreading Neo-Pacific Ocean from the continental margin; and (4) a Late Jurassic to Recent period where spreading occurred in both the Atlantic and Pacific Oceans, subjecting the second volcanic archipelago and the continental margin to major tectonism; since the Paleocene, the Cordillera has slid towards the NNW along transform faults.

Radiolarian assemblages of Middle and Late Jurassic to early Late Cretaceous (Cenomanian) ages from an olistolith record pelagic deposition within the Bornova Flysch Zone in western Turkey

2012 ◽  
Vol 183 (4) ◽  
pp. 307-318 ◽  
Author(s):  
Ugur Kagan Tekin ◽  
M. Cemal Göncüoglu ◽  
Seda Uzuncimen
Keyword(s):  
Late Cretaceous ◽  
Middle Jurassic ◽  
Late Jurassic ◽  
Western Turkey ◽  
Oceanic Basin ◽  
Platform Margin ◽  
Lowermost Part ◽  
Early Late ◽  
Radiolarian Assemblages

Abstract The Bornova Flysch Zone (BFZ) in NW Anatolia comprises several olistoliths or tectonic slivers, representing various parts of the Izmir-Ankara ocean. Radiolarian assemblages extracted from one of the olistoliths of the BFZ, cropping out along the Sögütlü section, to the NE Manisa city, were studied in detail. The lowermost part of the section contains latest Bajocian – early Callovian radiolarian taxa, followed by radiolarian assemblages indicating Late Jurassic to early Late Cretaceous (Cenomanian) ages. Previous studies reveal that the Izmir-Ankara oceanic basin was initially opened during late Ladinian – early Carnian. The new radiolarian data obtained from this olistolith reveals that relatively condensed, and possibly more or less continuous, pelagic sedimentation took place during the late Middle Jurassic to early Late Cretaceous in a non-volcanic oceanic basin closer to the Tauride-Anatolide platform margin.

New multituberculate mammal from the Early Cretaceous of eastern North America

2013 ◽  
Vol 50 (3) ◽  
pp. 315-323 ◽  
Author(s):  
Richard L. Cifelli ◽  
Cynthia L. Gordon ◽  
Thomas R. Lipka
Keyword(s):  
North America ◽  
Iberian Peninsula ◽  
Early Cretaceous ◽  
North American ◽  
Lower Cretaceous ◽  
Late Jurassic ◽  
Relative Length ◽  
Central Position ◽  
Eastern North America ◽  
The North

Multituberculates, though among the most commonly encountered mammalian fossils of the Mesozoic, are poorly known from the North American Early Cretaceous, with only one taxon named to date. Herein we describe Argillomys marylandensis, gen. et sp. nov., from the Early Cretaceous of Maryland, based on an isolated M2. Argillomys represents the second mammal known from the Arundel Clay facies of the Patuxent Formation (Lower Cretaceous: Aptian). Though distinctive in its combination of characters (e.g., enamel ornamentation consisting of ribs and grooves only, cusp formula 2:4, presence of distinct cusp on anterobuccal ridge, enlargement of second cusp on buccal row, central position of ultimate cusp in lingual row, great relative length), the broader affinities of Argillomys cannot be established because of non-representation of the antemolar dentition. Based on lack of apomorphies commonly seen among Cimolodonta (e.g., three or more cusps present in buccal row, fusion of cusps in lingual row, cusps strongly pyramidal and separated by narrow grooves), we provisionally regard Argillomys as a multituberculate of “plagiaulacidan” grade. Intriguingly, it is comparable in certain respects to some unnamed Paulchoffatiidae, a family otherwise known from the Late Jurassic – Early Cretaceous of the Iberian Peninsula.

The Currently Earliest Angiosperm Fruit from the Jurassic of North America

2021 ◽  
Vol 2 (4) ◽  
Author(s):  
Xin Wang
Keyword(s):  
North America ◽  
Early Cretaceous ◽  
Middle Jurassic ◽  
Early Evolution ◽  
The North ◽  
Plant Group ◽  
Ecological Radiation ◽  
Origin Of Angiosperms ◽  
Crucial Test

Angiosperms are the single most important plant group in the current ecosystem. However, little is known about the origin and early evolution of angiosperms. Jurassic and earlier traces of angiosperms have been claimed multiple times from Europe and Asia, but reluctance to accept these records remains. To test the truthfulness of these claims, palaeobotanical records from continents other than Europe and Asia constitute a crucial test. Here I document a new angiosperm fruit, Dilcherifructus mexicana gen. et sp. nov, from the Middle Jurassic of Mexico. Its Jurassic age suggests that origin of angiosperms is much earlier than widely accepted, while its occurrence in the North America indicates that angiosperms were already widespread in the Jurassic, although they were still far away from their ecological radiation, which started in the Early Cretaceous.

scholarly journals Hacking Networks of Terror

Dialogue IO ◽  
2002 ◽  
Vol 1 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Ronald J. Deibert ◽  
Janice Gross Stein
Keyword(s):  
United States ◽  
North America ◽  
The United States ◽  
The Core ◽  
Nonstate Actor

That we in North America face a new kind of threat is beyond question. The attacks against the heartland of the United States, its corporate and military icons, and the killing of over 3,000 civilians, mark a watershed in thinking about security. It is almost two hundred years since civilians in North America have been the object of systematic attack, and even longer since the core of the hegemonic power was struck from the periphery. The important analytical and political questions are What kind of threat do we face? What is the appropriate response to that threat? In other words, what are the appropriate ways to think about dealing with a threat from a nonstate actor with no fixed location or permanently defined territorial assets?

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