Geochemical discrimination between ocean-floor and island-arc tholeiites—application to some ophiolites

1979 ◽  
Vol 16 (9) ◽  
pp. 1874-1882 ◽  
Author(s):  
L. Beccaluva ◽  
D. Ohnenstetter ◽  
M. Ohnenstetter
Keyword(s):  
North America ◽  
Oceanic Crust ◽  
Island Arc ◽  
The Other ◽  
Ocean Floor ◽  
Oceanic Ridge ◽  
Marginal Basin ◽  
Discrimination Diagram ◽  
The Mediterranean ◽  
Arc Setting

Two discriminative diagrams are proposed to separate island-arc tholeiites (1AT) and ocean-floor tholeiites (OFT). The first diagram, Ti/Cr vs. Ni, has been drawn using 84 island-arc (IAT) and 178 ocean-floor (OFT) samples with silica contents between 40 and 56%. About 97% of OFT and 93% of IAT samples fall, respectively, on opposite sides of the empirical boundary. In the second diagram, where the Ba/Y is less than 4.4 for the OFT and more than 3.9 for the IAT, the overlap between the two groups is about 6%.Owing to alteration effects, only the discrimination diagram Ti/Cr vs. Ni has been applied to ophiolitic basalts from the Mediterranean belts, Newfoundland, Central and North America, and Mongolia. The effusive and hypabyssal formations plotting either in one group or in the other lead to the suggestion that they have been formed in several possible geotectonical environments. It appears that ophiolites generated in a mid-oceanic ridge are scarce in opposition to those formed in an island-arc setting. In this latter case, ophiolite associations may correspond to the juxtaposition of either island-arc – marginal basin or island-arc – offshore oceanic crust formations.

scholarly journals XX. Discovery of the metamorphosis in the second type of the cirripedes, viz. the lepades, completing the natural history of these singular animals, and confirming their affinity with the crustacea

1835 ◽  
Vol 125 ◽  
pp. 355-358 ◽  
Keyword(s):  
North America ◽  
Natural History ◽  
Sea Water ◽  
The Other ◽  
External Appearance ◽  
The Real ◽  
Real Nature ◽  
History Of ◽  
The Mediterranean ◽  
The Waves

The Fourth Memoir, published in my Zoological Researches and Illustrations, No. III. page 69, &c., having first made known the real nature of the Cirripedes , the key of which remained concealed in their metamorphosis, it might have been expected that some naturalist favourably situated to investigate the oceanic tribe of these animals, would have been the first to make the same discovery in regard to these, and thereby complete their natural history. It was scarcely to be expected that the honour of this discovery also should be reserved for the author, fixed to one spot, where none of them naturally exist, and are but casually thrown upon our shores by the waves of the Atlantic, attached to pieces of wreck, or brought into port fixed to the bottoms of ships returning from distant voyages. Fortunately, however, two ships of this description came into this harbour (Cork), one from the Mediterranean, the other from North America, which, not being sheathed with copper, had their bot­toms literally covered with Barnacles of the three genera of Lepas , Cineras , and Otion ; and having persons employed expressly for the purpose, numbers of these were brought alive in sea water, amongst which were many with the ova in various stages of their progress, and some ready to hatch, which they eventually did in prodigious numbers, so as to enable him to add the proof of their being, like the Balani, natatory Crusta­cea in their first stage , but of a totally different facies and structure; a circumstance which determines the propriety of the separation of the Cirripedes into two tribes, and evinces the sagacity of Mr. MacLeay in being the first to indicate that these two tribes, the Balani and Lepades , were not so closely related as generally supposed. The larvæ of the Balani , described in Memoir IV. under the external appearance of the bivalve Monoculi ( Astracoda ), have a pair of pedunculated eyes, more numerous and more completely developed members, approximating to those of Cyclops , and of the perfect Triton ; while, in the present type, or Lepades , the larva resembles some­what that of the Cyclops , which Müller, mistaking for a perfect animal, named Amymone , and which can be shown to he common to a great many of the Entomostraca ; or the resemblance is still more striking to that of the Argulus Armiger of Latreille, which, in fact, is but an Amymone furnished with a tricuspidate shield at the back.

Nina Creek Group and Lay Range Assemblage, north-central British Columbia: remnants of late Paleozoic oceanic and arc terranes

1997 ◽  
Vol 34 (6) ◽  
pp. 854-874 ◽  
Author(s):  
Filippo Ferri
Keyword(s):  
British Columbia ◽  
North America ◽  
Volcanic Rocks ◽  
Tholeiitic Basalt ◽  
Ocean Floor ◽  
North Central ◽  
Marginal Basin ◽  
The North ◽  
Lower Division ◽  
Ocean Ridge

In north-central British Columbia, a belt of upper Paleozoic volcanic and sedimentary rocks lies between Mesozoic arc rocks of Quesnellia and Ancestral North America. These rocks belong to two distinct terranes: the Nina Creek Group of the Slide Mountain terrane and the Lay Range Assemblage of the Quesnel terrane. The Nina Creek Group is composed of Mississippian to Late Permian argillite, chert, and mid-ocean-ridge tholeiitic basalt, formed in an ocean-floor setting. The sedimentary and volcanic rocks, the Mount Howell and Pillow Ridge successions, respectively, form discrete, generally coeval sequences interpreted as facies equivalents that have been interleaved by thrusting. The entire assemblage has been faulted against the Cassiar terrane of the North American miogeocline. West of the Nina Creek Group is the Lay Range Assemblage, correlated with the Harper Ranch subterrane of Quesnellia. It includes a lower division of Mississippian to Early Pennsylvanian sedimentary and volcanic rocks, some with continental affinity, and an upper division of Permian island-arc, basaltic tuffs and lavas containing detrital quartz and zircons of Proterozoic age. Tuffaceous horizons in the Nina Creek Group imply stratigraphic links to a volcanic-arc terrane, which is inferred to be the Lay Range Assemblage. Similarly, gritty horizons in the lower part of the Nina Creek Group suggest links to the paleocontinental margin to the east. It is assumed that the Lay Range Assemblage accumulated on a piece of continental crust that rifted away from ancestral North America in the Late Devonian to Early Mississippian by the westward migration of a west-facing arc. The back-arc extension produced the Slide Mountain marginal basin in which the Nina Creek Group was deposited. Arc volcanism in the Lay Range Assemblage and other members of the Harper Ranch subterrane was episodic rather than continuous, as was ocean-floor volcanism in the marginal basin. The basin probably grew to a width of hundreds rather than thousands of kilometres.

The Sylvester Allochthon: upper Paleozoic marginal-basin and island-arc terranes in northern British Columbia

1993 ◽  
Vol 30 (3) ◽  
pp. 631-643 ◽  
Author(s):  
JoAnne L. Nelson
Keyword(s):  
North America ◽  
Deep Water ◽  
Island Arc ◽  
Upper Permian ◽  
Structural Level ◽  
Division Iii ◽  
Crust And Upper Mantle ◽  
Marginal Basin ◽  
Upper Paleozoic ◽  
Division Ii

The Sylvester Allochthon is a composite klippe of upper Paleozoic ophiolitic, island-arc, and pericratonic assemblages, which rests directly on the Cassiar terrane, a displaced sliver of Ancestral North America. Each tectonic assemblage occurs at a distinct and consistent structural level within the allochthon. They are assigned, respectively, to the Slide Mountain, Harper Ranch, and Yukon–Tanana terranes. The Sylvester Allochthon provides a view of the structural relationships between these terranes prior to Early Cretaceous – early Tertiary strike-slip dismemberment, as well as possible sedimentological links to late Paleozoic North America. Slide Mountain Terrane assemblages, designated divisions I and II, form the lowest structural panels. Chert – quartz sandstones are interbedded with Lower Mississippian deep-water sediments in division I and ocean-floor basalts and deep-water sediments in division II. They are similar in age and character to sandstones in the autochthonous Earn Group. Division II assemblages represent atypical oceanic crust and upper mantle assemblages. Continuous basalt–sedimentary sequences, well dated by conodont faunas, span Early Mississippian to mid-Permian time. Feeders for the basalts are sills rather than sheeted dyke swarms, suggesting very slow spreading and high(?) sedimentation rates in a marginal-basin setting. These supracrustal sequences are thrust-imbricated with ultramafite–gabbro panels. Division II is in part overlain by a Triassic siliciclastic and limy sedimentary sequence, which resembles the basal Takla Group, Slocan Group, and autochthonous Triassic units. Division III occupies the highest structural levels in the allochthon. With one exception, thrust sheets within it consist of Pennsylvanian to Upper Permian mixed calc-alkaline volcanic and plutonic rocks, chert, tuff, and limestone, assigned to the Harper Ranch Terrane. One panel, assigned to the Yukon–Tanana Terrane, consists of an Early Mississippian quartz diorite pluton with Precambrian inheritance that intrudes older volcanogenic sediments, pyroclastics, limestone, and siliciclastic sediments. Preferred pre-Mesozoic restoration of these terrane elements shows a Harper Ranch arc, built partly on pericratonic Yukon–Tanana and partly on primitive oceanic basement (division III), which is separated from North America by the Slide Mountain marginal basin (divisions I and II).

Geochemistry of the upper Snooks Arm Group basalts, Burlington Peninsula, Newfoundland: evidence against formation in an island arc

1980 ◽  
Vol 17 (7) ◽  
pp. 888-900 ◽  
Author(s):  
G. A. Jenner ◽  
B. J. Fryer
Keyword(s):  
Subduction Zone ◽  
Oceanic Crust ◽  
Sedimentary Rocks ◽  
Oceanic Islands ◽  
Oceanic Island ◽  
Island Arc ◽  
Geochemical Data ◽  
Basaltic Rocks ◽  
Arc Setting ◽  
Back Arc

The Snooks Arm Group of the Newfoundland Appalachians, which includes the Betts Cove ophiolite at its base, has been interpreted as oceanic crust overlain by island arc volcanic and sedimentary rocks. The limited geochemical data available on the upper Snooks Arm Group basalts have been used as evidence for and against their formation in an island arc environment.Reinvestigation of the chemistry of the basaltic rocks of the upper Snooks Arm Group establishes them as large ion lithophile enriched tholeiites. Similar basalts have been found in oceanic islands, on aseismic ridges, and possibly in back-arc basins. Chemically analogous rocks are notably lacking from island arc settings.The geochemistry and geology of the upper Snooks Arm Group suggest that these rocks may have formed in either an oceanic island setting or, as recently suggested by Upadhyay and Neale, as part of a marginal basin. It is not possible to distinguish between these alternate models, although the most similar basaltic rocks occur in the former environment. It is most unlikely that these rocks formed in an early island arc setting and indeed there may be no need for them to be associated with a major subduction zone.

The Cenomanian-Turonian (late Cretaceous) radiation of marine squamates (Reptilia): the role of the Mediterranean Tethys

2008 ◽  
Vol 179 (6) ◽  
pp. 605-622 ◽  
Author(s):  
Nathalie Bardet ◽  
Alexandra Houssaye ◽  
Jean-Claude Rage ◽  
Xabier Pereda Suberbiola
Keyword(s):  
North America ◽  
Sea Level ◽  
Bone Microstructure ◽  
The Other ◽  
Sea Surface ◽  
Western Interior Seaway ◽  
Wide Range ◽  
The Mediterranean ◽  
Large Predators

AbstractDuring the Cenomanian-Turonian interval, marine squamates display a spectacular radiation in particular on the margins of the Mediterranean Tethys and, to a lesser extent, in the Interior Seaway of North America. In this span of time, three major groups diversified: the “hind-limbed” snakes (“pachyophiids”), the “dolichosaurids”, and the mosasauroids. “Hind-limbed” snakes, exhibiting all a pachyostotic bony structure, were small tropical inhabitants, known exclusively from the Cenomanian of the Mediterranean Tethys. “Dolichosaurids” and mosasauroids were rather mid latitude distributed groups, found in a wide range of palaeoenvironments of both the Mediterranean Tethys and the Western Interior Seaway. Whereas “dolichosaurids” remain of small size and become rare after the Cenomanian/Turonian (C/T) boundary, mosasauroids exhibit a notable size-increase and develop since the mid Turonian to become highly diversified and cosmopolitan large predators of the end of the Cretaceous. This important radiation of marine squamates is thus, except for derived mosasauroids (mosasaurids), restricted in time (Cenomanian-Turonian) and space (mostly the northern and southern margins of the Mediterranean Tethys). It is probable that: 1) the Mediterranean Tethys played an important role in both the radiation and the dispersion of these marine squamates during the Cenomanian-Turonian interval; 2) certain major geological and biological events that characterize this pivotal period (i.e., global high sea-level stand and warm sea-surface temperatures allowing the development of large carbonated platforms) could have permitted this radiation; and 3) conversely, other factors occurring at or just after the C/T boundary (OAE2, sea-level and sea-surface temperature drops, marine extinctions including the demise of carbonated platforms) as well as factors inherent to each of the groups (mainly the size and bone microstructure) could have had an effect on and insured the success of the mosasaurids with respect to the other groups, whereas thereafter the radiation of snakes succeeded only in continental environments.

Chemistry and origin of the Eocene Metchosin Volcanics, Vancouver Island, British Columbia

1980 ◽  
Vol 17 (2) ◽  
pp. 199-209 ◽  
Author(s):  
J. E. Muller
Keyword(s):  
Major Element ◽  
Vancouver Island ◽  
Oceanic Island ◽  
Island Arc ◽  
Olympic Peninsula ◽  
Oceanic Ridge ◽  
Late Tertiary ◽  
Juan De Fuca ◽  
Intrusive Rocks ◽  
Arc Setting

The Metchosin Volcanics of southern Vancouver Island consist of submarine pillow lavas, tuffs, and breccias, overlain by subaerial flows of mainly tholeiitic composition. They overlie basaltic dyke complexes and gabbro and are interpreted as Eocene (and older?) oceanic floor and oceanic island tholeiites. They are separated by the fundamental Leech River Fault from the Paleozoic and Mesozoic rocks underlying Vancouver Island. Major and trace element chemical analyses of the volcanics and a few related intrusive rocks are compared with those of recent to late Tertiary tholeiites from known oceanic settings and with the coeval Crescent Volcanics of the Olympic Peninsula. Possible settings are: (1) oceanic ridge (e.g., mid-Atlantic, Juan de Fuca); (2) oceanic ridge-island (e.g., Iceland); (3) oceanic intra-plate island (e.g., Hawaii); and (4) oceanic island arc (e.g., Tonga–Kermadec). Alkali–silica and AFM diagrams clearly define the subalkaline and tholeiitic character but do not allow distinction of these four oceanic settings. Major element factor analysis yields doubtful results but could perhaps be improved by increased data base. Several orthogonal plots of abundances of Ti, Fe, Mg, Zr, and Cr seem to permit distinction of the four types of tholeiites.On geological and chemical bases Metchosin and Crescent formations correspond most closely to the Icelandic ridge-island setting; the Hawaiian intra-plate island setting is less probable in view of several chemical distinctions. The ocean floor setting, though chemically similar in several plots, is precluded at least for the upper, nonmarine parts of the formations. Lastly, an island arc setting is not indicated by either general lithology or chemistry.

Sr, Y, Zr, Nb, Ti, and REE in Grenville amphibolites at Montauban-les-Mines, Quebec

1982 ◽  
Vol 19 (4) ◽  
pp. 633-644 ◽  
Author(s):  
W. H. MacLean ◽  
K. St. Seymour ◽  
M. K. Prabhu
Keyword(s):  
Tectonic Setting ◽  
Island Arc ◽  
The Other ◽  
Ocean Floor ◽  
Grenville Province ◽  
Ree Distribution ◽  
Back Arc ◽  
Ore Deposition

Distribution of Ti, Sr, Y, Zr, Nb, and REE in Proterozoic amphibolites and a rarely preserved pillowed metabasalt in the vicinity of Pb–Zn mineralization at Montauban-les-Mines in the Grenville Province of Quebec are used to assess the tectonic setting of the volcanism and, hence, the environment of ore deposition. Absolute abundances of Ti, Sr, Y, Zr, and Nb are close to those reported for modem island-arc and back-arc basalts. The flat patterns of the chondrite-normalized REE distribution and the discrimination plots of the other elements indicate a tholeiitic affinity for the volcanism. Specifically, plots of Ti against Zr and Ti–Zr–Y are mostly in the fields reported for ocean-floor (MOR and back-arc) basalts, but overlap with arc tholeiites. Cr and Ni are, however, higher than for most arc tholeiites. Overall, the data are most compatible with tholeiitic volcanism in an island-arc (including back-arc) environment.

scholarly journals Naturalization and spread of the alien species Ozognathus cornutus (LeConte, 1859) (Coleoptera: Ptinidae: Ernobiinae) in Italy

2021 ◽  
Author(s):  
Giuliano Cerasa ◽  
Gabriella Lo Verde
Keyword(s):  
North America ◽  
Fruits And Vegetables ◽  
First Record ◽  
The Other ◽  
Ecological Role ◽  
Dried Fruits ◽  
Wood Shavings ◽  
Potential Pest ◽  
Small Wood ◽  
Natural Barrier

AbstractOzognathus cornutus (LeConte, 1859) (Coleoptera: Ptinidae: Ernobiinae), species native to North America, is a saproxylophagous species and is known to feed on decaying tissues within conspicuous galls and on vegetal decaying organic material such as dried fruits or small wood shavings and insect excrements in galleries made by other woodboring species. A few years after the first record in 2011, its naturalization in Italy is here reported. The insect was found as successor in galls of Psectrosema tamaricis (Diptera Cecidomyiidae), Plagiotrochus gallaeramulorum, Andricus multiplicatus and Synophrus politus (Hymenoptera Cynipidae). The galls seem to have played an important ecological role in speeding up the naturalization process. The lowest proportion of galls used by O. cornutus was recorded for P. tamaricis (23%), the only host belonging to Cecidomyiidae, while the percentages recorded for the other host species, all Cynipidae forming galls on oaks, were higher: 43.6%, 61.1% and 76.9% in A multiplicatus, S. politus and P. gallaeramulorum, respectively. Although O. cornutus is able to exploit other substrates like dried fruits and vegetables, for which it could represent a potential pest, it prefers to live as a successor in woody and conspicuous galls, which thus can represent a sort of natural barrier limiting the possible damages to other substrates.

scholarly journals Eurasian and North American phylogeny of Turolian hipparionine horses (Perissodactyla, Mammalia) in China

1992 ◽  
Vol 6 ◽  
pp. 305-305
Author(s):  
Mahito Watabe
Keyword(s):  
North America ◽  
North American ◽  
Northern China ◽  
Sensu Stricto ◽  
The Other ◽  
Dental Morphology ◽  
Facial Morphology ◽  
Open Land ◽  
Specialized Form ◽  
Eastern Half

The late Miocene Chinese hipparions are morphologically diversified showing similarity to both western Old World's and North American forms. Two Chinese taxa that are phylogenetically related to western Old World's forms are Hipparion fossatum (= H. forstende) from Baode (Shanxi) and H. hippidiodus from Qingyang (Gansu) and Baode. The former is related to H. mediterraneum and the latter to H. urmiense - platygenys from the Turolian localities in the western Old World. H. fossatum and H. hippidiodus are associated with the “dorcadoides” (open-land) and “mixed” faunas in northern China. Hipparion fossatum that is characterized by POF located close to the orbit co-occurs with large and morphologically specialized form, H. dermatorhinum in Baode (Loc.30). H. hippidiodus with reduced POF is discovered with smaller H. coelophyes in Loc. 43, 44 (Baode) and Loc. 115 (Gansu).The hipparions associated with the “gaudryi” (forest) fauna are characterized by well defined and small POF located far from the orbit. Those forms are: H. platyodus from Loc. 70; H. ptychodus from Loc. 73; H. tylodus from Hsi-Liang in Yushe - Wuxiang basins; and H. sefvei from Loc. 12 at Xin-an in Henan province. H. coelophyes from Baode (Loc.43 & 44) and Qingyang (Loc. 115) also show similar facial morphology to the these forms, although it has small size and shallow POF. Those forms are similar in facial and dental morphology to Hipparion sensu stricto and some species of Cormohipparion in North America.The assemblages of Chinese hipparions are composed of two groups whose members are phylogenetically similar to the forms from both western part of Eurasia and North America. The “gaudryi” fauna is considered younger than the other two on the basis of faunal analyses. The similarity in hipparionine taxonomy between northern China and North America in the latest Miocene is an evidences for possible faunal interchange(s) occurred during that period, as suggested by taxonomic analyses on carnivores and proboscideans in eastern half of Eurasia and North America.

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