Facies and small-scale geometries of the Late Triassic Kawr Platform, Sultanate of Oman

2001 ◽  
Vol 28 (1) ◽  
pp. 155-157
Author(s):  
Elias Samankassou ◽  
M. Bernecker ◽  
Erik Flügel
Keyword(s):  
Late Triassic ◽  
Small Scale ◽  
Sultanate Of Oman

Systematics and Paleoecology of Norian (Late Triassic) Bivalves from a Tropical Island Arc: Wallowa Terrane, Oregon

1987 ◽  
Vol 61 (S22) ◽  
pp. 1-83 ◽  
Author(s):  
Cathryn R. Newton ◽  
Michael T. Whalen ◽  
Joel B. Thompson ◽  
Nienke Prins ◽  
David Delalla
Keyword(s):  
North American ◽  
Island Arc ◽  
Late Triassic ◽  
Small Scale ◽  
Long Distance ◽  
Tropical Island ◽  
North American Cordillera ◽  
The North ◽  
Wallowa Terrane ◽  
Hells Canyon

Early Norian silicified bivalves from Hells Canyon in the Wallowa terrane of northeastern Oregon are part of a rich molluscan biota associated with a tropical island arc. The Hells Canyon locality preserves lenses of silicified shells formed as tempestites in a shallow subtidal carbonate environment. These shell assemblages are parautochthonous and reflect local, rather than long-distance, transport. Silicification at this locality involved small-scale replacement of original calcareous microstructures, or small-scale replacement of neomorphosed shells, without an intervening phase of moldic porosity. This incremental replacement of carbonate by silica contrasts markedly with void-filling silicification textures reported previously from silicified Permian bivalve assemblages.The bivalve paleoecology of this site indicates a suspension feeding biota existing on and within the interstices of coral-spongiomorph thickets, and inhabiting laterally adjacent substrates of peloidal carbonate sand. The bivalve fauna is ecologically congruent with the reef-dwelling molluscs associated with Middle Triassic sponge-coral buildups in the Cassian Formation of the Dolomites (Fuersich and Wendt, 1977). Hells Canyon is a particularly important early Norian locality because of the diversity of substrate types and because the site includes many first occurrences of bivalves in the North American Cordillera. These first occurrences include the first documentation of the important epifaunal families Pectinidae and Terquemiidae in Triassic rocks of the North American Cordillera.The large number of biogeographic and geochronologic range extensions discovered in this single tropical Norian biota indicates that use of literature-based range data for Late Triassic bivalves may be very hazardous. Many bivalve taxa formerly thought to have gone extinct in Karnian time have now been documented from Norian strata in this arc terrane. These range extensions, coupled with the high bivalve species richness of the Hells Canyon site, suggest that the Karnian mass extinction in several literature-based compilations may be an artifact of incomplete sampling. Even for the Norian, present compilations of molluscan extinction may have an unacceptably large artifactual component.Thirty-five bivalve taxa from the Hells Canyon locality are discussed. Of these, seven are new: the mytilid Mysidiella cordillerana n. sp., the limacean Antiquilima vallieri n. sp., the true oyster Liostrea newelli n. sp., the pectinacean Crenamussium concentricum n. gen. and sp., the unioid Cardinioides josephus n. sp., the trigoniacean Erugonia canyonensis n. gen. and sp., and the carditacean Palaeocardita silberlingi n. sp.

scholarly journals Biological Indicators Reveal Small-Scale Sea-Level Variability During MIS 5e (Sur, Sultanate of Oman)

10.5334/oq.72 ◽  
2020 ◽  
Vol 6 ◽  
Author(s):  
M. Falkenroth ◽  
S. Adolphs ◽  
M. Cahnbley ◽  
H. Bagci ◽  
M. Kázmér ◽  
...  
Keyword(s):  
Sea Level ◽  
Biological Indicators ◽  
Small Scale ◽  
Sultanate Of Oman ◽  
Sea Level Variability ◽  
Mis 5E

scholarly journals The Alkaline Lamprophyres of the Dolomitic Area (Southern Alps, Italy): Markers of the Late Triassic Change from Orogenic-like to Anorogenic Magmatism

2019 ◽  
Vol 60 (6) ◽  
pp. 1263-1298 ◽  
Author(s):  
Federico Casetta ◽  
Ryan B Ickert ◽  
Darren F Mark ◽  
Costanza Bonadiman ◽  
Pier Paolo Giacomoni ◽  
...  
Keyword(s):  
Trace Element ◽  
Southern Alps ◽  
Late Triassic ◽  
Small Scale ◽  
Main Process ◽  
Calc Alkaline ◽  
Isotopic Signatures ◽  
Systematic Uncertainties ◽  
High K ◽  
Magmatic Event

AbstractWe present the first complete petrological, geochemical and geochronological characterization of the oldest lamprophyric rocks in Italy, which crop out around Predazzo (Dolomitic Area), with the aim of deciphering their relationship with Triassic magmatic events across the whole of the Southern Alps. Their Mg# of between 37 and 70, together with their trace element contents, suggests that fractional crystallization was the main process responsible for their differentiation, together with small-scale mixing, as evidenced by some complex amphibole textures. Moreover, the occurrence of primary carbonate ocelli suggests an intimate association between the alkaline lamprophyric magmas and a carbonatitic melt. 40Ar/39Ar data show that the lamprophyres were emplaced at 219·22 ± 0·73 Ma (2σ; full systematic uncertainties), around 20 Myr after the high-K calc-alkaline to shoshonitic, short-lived, Ladinian (237–238 Ma) magmatic event of the Dolomitic Area. Their trace element and Sr–Nd isotopic signatures (87Sr/86Sri = 0·7033–0·7040; 143Nd/144Ndi = 0·51260–0·51265) are probably related to a garnet–amphibole-bearing lithosphere interacting with an asthenospheric component, significantly more depleted than the mantle source of the high-K calc-alkaline to shoshonitic magmas. These features suggest that the Predazzo lamprophyres belong to the same alkaline–carbonatitic magmatic event that intruded the mantle beneath the Southern Alps (e.g. Finero peridotite) between 190 and 225 Ma. In this scenario, the Predazzo lamprophyres cannot be considered as a late-stage pulse of the orogenic-like Ladinian magmatism of the Dolomitic Area, but most probably represent a petrological bridge to the opening of the Alpine Tethys.

scholarly journals Facies, sequence stratigraphy and reservoir/seal potential of a Jilh Formation outcrop equivalent (Wadi Sahtan, Triassic, Upper Mahil Member, Sultanate of Oman)

GeoArabia ◽  
2012 ◽  
Vol 17 (3) ◽  
pp. 85-128 ◽  
Author(s):  
Michael Obermaier ◽  
Thomas Aigner ◽  
Holger C. Forke
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Second Order ◽  
Late Triassic ◽  
Small Scale ◽  
Third Order ◽  
Sequence Stratigraphic ◽  
Oman Mountains ◽  
Sequence Boundaries ◽  
Reservoir Potential

ABSTRACT The investigated Middle to Upper Triassic Upper Mahil Member, representing a Jilh outcrop equivalent in the Northern Oman Mountains, illustrates the proximal portion of a flat epeiric carbonate ramp. A sedimentological study of well-exposed outcrops in Wadi Sahtan may serve as a reference section for a sequence-stratigraphic framework and detailed facies description of the Upper Mahil Member. It also provides an insight into the seal and reservoir potential of carbonates in a low-accommodation inner ramp setting. Outcrop observations and thin section analyses yielded 14 different lithofacies types ranging from a supratidal marsh to high-energy subtidal shoal environment. Vertical facies stacking patterns show three basic small-scale cycle motifs (fifth-order). While mud-rich backshoal cycles with claystone intercalations and rooted/bioturbated mud-/wackestones illustrate potential baffles and seal units around the center of the Upper Mahil, potential reservoir units occur stratigraphically in the upper part of the formation. There, a few meter-thick trough cross-bedded oolitic-/peloidal-rich grainstone depicts maximum accommodation within backshoal to shoal cycle types below the erosional base-Jurassic unconformity. The investigated outcrop section in Wadi Sahtan was subdivided into nine almost complete third-order sequences. Two to four of these sequences are further stacked into three second-order super-sequences which are well reflected in the gamma-ray pattern. The highest reservoir potential occurs around second-order maximum floodings. Internal seals can be observed at third-order sequence boundaries where shales and muddy carbonates are up to 20 m thick. A regional correlation with subsurface data from Yibal and Lekhwair in Oman shows that the apparent thickness changes in the Upper Mahil (Jilh) are mainly determined by the Late Triassic/Early Jurassic erosional truncation. The occurrence of thick anhydrite units in the subsurface indicates a more proximal setting towards the southwest.

Geochronology and geochemistry of the Cuihongshan Fe-polymetallic deposit, northeastern China: implications for ore genesis and tectonic setting

2018 ◽  
Vol 55 (5) ◽  
pp. 475-489 ◽  
Author(s):  
Yong Zhang ◽  
Jing-Gui Sun ◽  
Shu-Wen Xing ◽  
Zeng-Jie Zhang
Keyword(s):  
Tectonic Setting ◽  
Alkali Feldspar ◽  
Northeastern China ◽  
Late Triassic ◽  
Small Scale ◽  
Polymetallic Deposit ◽  
Central Asian ◽  
Metallogenic Belt ◽  
High K ◽  
Final Closure

The Lesser Xing’an Range is located in the eastern segment of the Central Asian Orogenic Belt. It hosts an important polymetallic metallogenic belt that contains more than 20 large- to small-scale porphyry Mo, epithermal Au, and skarn Fe-polymetallic deposits. The Cuihongshan Fe-polymetallic deposit is one of the largest polymetallic deposits in northeastern China. To better understand the formation of the Cuihongshan Fe-polymetallic deposit, we investigated the geological characteristics of the Cuihongshan deposit and applied geochemistry and geochronology to constrain the timing of the mineralization, and characteristics of the magmas. Zircon U–Pb dating of the alkali-feldspar granite and monzogranite yielded weighted mean 206Pb/238U ages of 495 ± 1.6 and 203 ± 1 Ma, respectively. Re–Os dating on molybdenite yielded an isochron age of 203.2 ± 1.4 Ma, and 40Ar/39Ar dating on phlogopite yielded an age of 203.4 ± 1.3 Ma. These data suggest that mineralization occurred during the Late Triassic, and is closely related with the monzogranite emplacement. These rocks belong to the high-K calc-alkaline and subalkaline series, are enriched in Rb, U, and Th, are depleted in Nb, Ta, and Ti, and show strong Eu anomalies, implying that they are A-type post-orogenic rocks. The Cuihongshan Fe-polymetallic formation is possibly related to an extensional environment resulting from the final closure of the Paleo-Asian Ocean.

Petrology of the Turnagain ultramafic complex, northwestern British Columbia

1980 ◽  
Vol 17 (6) ◽  
pp. 744-757 ◽  
Author(s):  
Thomas Clark
Keyword(s):  
Volcanic Rocks ◽  
Central Zone ◽  
Minor Element ◽  
Outer Zone ◽  
Late Triassic ◽  
Small Scale ◽  
Chrome Spinel ◽  
Low Oxygen ◽  
Nickel Copper ◽  
Ultramafic Complex

The Turnagain ultramafic complex is an Alaskan-type complex of possible Late Triassic age. It has a central zone of dunite and an outer zone of wehrlite, olivine clinopyroxenite, clinopyroxenite, dunite, hornblendite (rare), and basic hornblende and plagioclase-bearing rock (rare). The complex is largely fault-bounded. The central dunite intrudes the pyroxene-bearing rocks in one area; elsewhere the two zones are gradational. Small-scale layering occurs locally, and is most common in the outer zone. Layering dips steeply due to folding during regional deformation. The ultramafic rocks are generally only partly serpentinized, and consist largely of olivine, clinopyroxene, pargasite, phlogopite, and chrome spinel. The outer zone contains sporadic concentrations of iron–nickel–copper sulfides. Olivine is most magnesian (Fo94.9) in the central dunite, and most iron-rich (Fo80.2) in olivine clinopyroxenite. Clinopyroxene is diopside and follows an iron-enrichment trend. Minor-element contents of minerals indicate that crystallization caused magmatic impoverishment in Ni and Cr, and enrichment in Ti and Al. The primitive Turnagain magma was probably ultrabasic, extremely magnesian, and poor in Al and Ti. Differentiation followed an alkalic trend, possibly at relatively low oxygen fugacity compared to other Alaskan-type complexes. The complex may have formed in a subvolcanic magma chamber, and thus be related to nearby Upper Triassic volcanic rocks.

scholarly journals Modelling Compliance in Small-scale Fisheries: A Case Study from the Sultanate of Oman

2020 ◽  
Vol 33 (2) ◽  
Author(s):  
IBRAHIM ABDULLAH AL-QARTOUBI ◽  
◽  
HUSSEIN AL-MASROORI ◽  
SHEKAR BOSE
Keyword(s):  
Small Scale ◽  
Sultanate Of Oman ◽  
Small Scale Fisheries

Reasons to strike first

2019 ◽  
Vol 42 ◽  
Author(s):  
William Buckner ◽  
Luke Glowacki
Keyword(s):  
Intergroup Conflict ◽  
Small Scale

Abstract De Dreu and Gross predict that attackers will have more difficulty winning conflicts than defenders. As their analysis is presumed to capture the dynamics of decentralized conflict, we consider how their framework compares with ethnographic evidence from small-scale societies, as well as chimpanzee patterns of intergroup conflict. In these contexts, attackers have significantly more success in conflict than predicted by De Dreu and Gross's model. We discuss the possible reasons for this disparity.

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