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Tytuł:
Lithostratigraphy of the Jurassic San Rafael Group from Bluff to the Abajo Mountains, southeastern Utah: Stratigraphic relationships of the Bluff Sandstone
Autorzy:
Lucas, S.
Powiązania:
https://bibliotekanauki.pl/articles/2077336.pdf
Data publikacji:
2014
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Jurassic
Utah
Morrison Formation
Summerville Formation
Carmel Formation
jura
Formacja Morrisona
Formacja Summerville
Formacja Carmel
Opis:
Measured sections of Jurassic San Rafael Group strata correlated by lithostratigraphy along an ~60 km transect between Bluff and the Abajo Mountains in southeastern Utah indicate that: (1) the Carmel Formation is continuous and disconformable on the Navajo Sandstone (J-2 unconformity); (2) the Entrada Sandstone (Slick Rock Member) is continuous and conformable on the Carmel; (3) the Summerville Formation is continuous and does not intertongue with the Entrada (its base is the J-2 unconformity); (4) the Bluff Sandstone grades northward into the upper Summerville south of the Abajo Mountains; (5) the Recapture Member of the Bluff is physically continuous with at least part of the Tidwell Member of the Summerville; and (5) the base of the Salt Wash Member of the Morrison Fm. is a pervasive unconformity (J-5) with demonstrable local stratigraphic relief of up to 14 m. These observations counter previous claims of extensive Entrada-Summerville intertonguing in southeastern Utah and do not support recognition of depositional sequence boundaries in the Entrada and Summerville lithosomes. Though Entrada deposition may have been by a wet eolian system, its southeastern Utah outcrops are well to the south/ southeast of any marine and paralic facies with which the Entrada intertongues.
Źródło:
Volumina Jurassica; 2014, 12, 2; 55--68
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dinosaur assemblages from the Middle Jurassic Shaximiao Formation and Chuanjie Formation in the Sichuan-Yunnan Basin, China
Autorzy:
Li, K.
Yang, Ch.
Hu, F.
Powiązania:
https://bibliotekanauki.pl/articles/2061002.pdf
Data publikacji:
2011
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
dinosaurs
Shaximiao Formation
Chuanjie Formation
Sichuan Basin
Yunnan Basin
Middle Jurassic
Opis:
The Shaximiao Formation (Sichuan Basin, China), and the corresponding Chuanjie Formation of the neighboring Yunnan Basin (Sichuan-Yunnan Basin), representing continental Mesozoic strata, are distinguished from other Chinese Mesozoic units because of the large area over which they are distributed, their lithological characteristics and their abundant vertebrate fossils. This paper analyses and summarizes the dinosaur fossils from the Shaximiao Formation and compares them to other vertebrate groups of the same or similar ages, both in China and abroad. For the first time, this paper presents the viewpoint that the upper member of the Shaximiao Formation is of Middle Jurassic age (Bathonian–Callovian). Furthermore, we claim that the entire Shaximiao Formation is of Bajocian–Callovian age (middle-late part of Middle Jurassic). This conclusion is supported by the age inferred from invertebrate fossils and radiometric dating (165–178 Ma). The composition, evolution and geological age of the vertebrate fauna (particularly dinosaur fossils), as well as their comparison to the dinosaur fauna from the other parts of the Sichuan-Yunnan Basin (Chuanjie Fm.) is discussed. Middle Jurassic dinosaur assemblages from China show marked differences compared with other dinosaur assemblages in the world, and this is explained by geographical isolation.
Źródło:
Volumina Jurassica; 2011, 9, 1; 21-42
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Jurassic vertebrate bromalites of the western United States in the context of the global record
Autorzy:
Hunt, A.
Lucas, S.
Powiązania:
https://bibliotekanauki.pl/articles/2077333.pdf
Data publikacji:
2014
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
bromalite
consumulite
evisceralite
Jurassic
Morrison Formation
Sundance Formation
western USA
jura
Formacja Morrisona
Formacja Sundance
USA
Opis:
The bromalite record of the western United States is quite limited, especially in contrast to the Triassic and Cretaceous records of the same region. Indeed, there are only a handful of well documented vertebrate bromalites from the Jurassic strata of the western USA, including: (1) coprolites from the nonmarine Early Jurassic Glen Canyon Group; (2) consumulites and evisceralites from the Middle Jurassic Todilto and Sundance formations; and (3) consumulites, putative coprolites and pseudobromalites from the nonmarine Upper Jurassic Morrison Formation. Early Jurassic red beds are notably less fossiliferous than those of the Triassic (e.g., contrast the fossil record of the Chinle and Glen Canyon groups). The Middle Jurassic of the region includes several eolianites and sabkha-like deposits representing environments that preserve few bromalites. The Upper Jurassic Morrison Formation contains abundant vertebrate body fossils and many tracks but very few bromalites in contrast to many broadly similar fluvial deposits of Triassic and Cretaceous age in the same region. The global bromalite record also appears to be depauperate in the Jurassic, with a few exceptions such as marine shales and lithographic limestones in Europe (e.g., Lower Jurassic of England, Upper Jurassic Solnhofen Limestone of Bavaria). This relative lack of a global Jurassic bromalite record may in part be more a result of a lack of collection and study. However, the relative lack of nonmarine bromalites is clearly influenced by high sea levels in the Early Jurassic, a paucity of Middle Jurassic nonmarine vertebrate-bearing units and a lack, or lack of recognition of, bromalites in major Upper Jurassic nonmarine vertebrate faunas (e.g., China, Tanzania, Portugal, etc.). In the Western United States there is clearly a need for more detailed examination of known specimens (e.g., putative Morrison coprolites) and a focus on collecting more examples.
Źródło:
Volumina Jurassica; 2014, 12, 2; 151--158
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sedimentary cycles in the Callovian-Oxfordian of the Jaisalmer Basin, Rajasthan, western India
Autorzy:
Pandey, E.
Sha, J.
Choudhary, S.
Powiązania:
https://bibliotekanauki.pl/articles/2061377.pdf
Data publikacji:
2010
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
cylicity
Jalsalmer Basin
Jalsalmer Formation
Callovian-Oxfordian
Opis:
The Callovian and Oxfordian marine sediments of the Jaisalmer Basin constitute the uppermost part of the Jaisalmer Formation, which comprises the Kuldhar and Jajiya members. In the present paper the authors illustrate retrogradational-progradational, more or less symmetrical cycles representing low- to high-energy marine environments. Despite an incomplete sedimentary record in a profile disrupted by a number of omission surfaces, it is possible to distinguish seven such sedimentary cycles in less than 24 m of sedimentary succession. The cycles, often bearing in their upper parts a thick-bedded well-cemented calcareous sandstone/pack- to rudstone, or hummocky cross-stratified beds indicative of storm events, are occasionally topped by hardgrounds. Hardgrounds provide well-defined boundaries useful for delineating correlative/bounding surfaces, identified here with sequence boundaries (3rd order cycles). Maximum flooding surfaces characterized by richly fossiliferous marly wackestones provide additional correlative horizons. Within these sequences, subordinate cycles can be tentatively distinguished, some of them may represent parasequences. The stratigraphical significance of correlative surfaces and sequences is tested by their fossil content, and these surfaces can be used for regional correlations with neighbouring basin.
Źródło:
Volumina Jurassica; 2010, 8, 1; 131-162
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Oxfordian biofacies and palaeoenvironments of Saudi Arabia
Autorzy:
Hughes, G.
Al-Khaled, M.
Varol, O.
Powiązania:
https://bibliotekanauki.pl/articles/2061341.pdf
Data publikacji:
2008
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Saudi Arabia
Oxfordian
Hanifa Formation
micropalaeontology
nannopalaeontology
stromatoporoids
Opis:
The Hanifa Formation in Saudi Arabia consists of a succession of carbonates, over 100 m thick, that were deposited during the Late Jurassic. It consists of two depositional sequences represented by the lower Hawtah Member and an upper Ulayyah Member, respectively. The Hawtah Member is assigned an Early (?) to Middle Oxfordian age, based on brachiopod, nautiloid and coccolith evidence. The Ulayyah Member is assigned a Late Oxfordian age based on ammonite, nautiloid, coccolith and foraminiferal evidence. Detailed study of the microbiofacies and lithology of the late highstand succession of the Ulayyah sequence in 41 cored wells distributed across the Kingdom was aimed at determining the most suitable locations for porous and permeable grainstone accumulation as lithofacies hosts the Hanifa Reservoir elsewhere in the region. A range of palaeoenvironments has been determined, based on integrated biofacies and lithofacies, that include shallow lagoon packstones and foraminiferal dominated grainstones and deep lagoon wackestones and packstones with Clypeina/Pseudoclypeina dasyclad algae. In addition, a series of basin-margin, shoal-associated biofacies are present that include stromatoporoid back-bank packstones and grainstones with the branched stromatoporoid Cladocoropsis mirabilis, bank-crest grainstones with encrusting and domed stromatoporoids. A few wells also proved the presence of intrashelf basin-flank mudstones and wackestones containing sponge spicules, deep marine foraminifera and coccoliths. This study provided control to delimit an intrashelf basin with an irregular margin situated in the east-central part of the Saudi Arabian portion of the Arabian Plate carbonate platform during Late Oxfordian. The basin is flanked by a belt of stromatoporoid banks that pass laterally into a back-bank facies before developing into a lagoon facies. There is no evidence for the shoreline of this basin, although the presence of rare charophytes in the northwest testifies to possible proximity of fluviatile input. The grainstone dominated basin margin facies presents good hydrocarbon reservoir facies and its juxtaposition to intrashelf basinal sediments with potential source rock character provides exciting new prospects in areas hitherto uninvestigated for hydrocarbon reservoirs.
Źródło:
Volumina Jurassica; 2008, 6, 1; 47-60
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new specimen of the basal macronarian Camarasaurus (Dinosauria: Sauropoda) highlights variability and cranial allometry within the genus
Autorzy:
Woodruff, D. Cary
Wilhite, D. Ray
Larson, Peter L.
Eads, Matthew
Powiązania:
https://bibliotekanauki.pl/articles/2060921.pdf
Data publikacji:
2021
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Camarasaurus
cranial allometry
Morrison Formation
allometria czaszki
formacja Morrisona
Opis:
Camarasaurus represents one of the most common dinosaurs from North America, and certainly a contender for one of the most abundantly represented dinosaur taxa worldwide. With numerous specimens ranging the gamut of completeness and maturity, Camarasaurus would theoretically represent a neosauropodian exemplar towards better understanding intra- and interspecific variation, dimorphism, and life history development and strategies. And yet, counterintuitively, its abundance is seemingly a deterrent for active research. Herein we describe a new specimen of Camarasaurus sp. which is most notably known from a nearly complete and articulated skull. While Camarasaurus cranial material is unquestionably the most common sauropod cranial material from North America, our understanding of the total cranial morphology is limited, and largely relies on more limited and historic specimens. In addition to further illuminating the morphology and variation present in Camarasaurus crania, associated post-crania also allow for the first recognition of possible cranial allometry. The identification of this perplexing cranial allometry in several specimens indicates that it is not a singular variation. Though this analysis was not able to source the causal mechanism, factors such as taxonomy, dimorphism, or extreme intra-/intraspecific variation are all possible considerations for future analyses. The recognition of this undocumented cranial allometry further emphasizes that despite being so numerous, there is still vast gaps in our knowledge about Camarasaurus; and this analysis further echoes that the genus is in desperate need of revision.
Źródło:
Volumina Jurassica; 2021, 19, 1; 109--130
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Whitmore Point Member of the Moenave Formation: Early Jurassic Dryland Lakes on the Colorado Plateau, Southwestern USA
Autorzy:
Tanner, L.
Lucas, S.
Powiązania:
https://bibliotekanauki.pl/articles/2061348.pdf
Data publikacji:
2008
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Utah
Arizona
Hettangian
Moenave Formation
meromictic
dryland
perennia
ephemeral
lacustrine
Opis:
The Lower Jurassic Whitmore Point Member of the Moenave Formation in Arizona-Utah, USA, comprises fish- and coprolite-bearing shales, siltstones, sandstones, and minor limestones. These facies were deposited in ephemeral and perennial lakes subject to episodic desiccation and incursions of coarse clastics during floods. Meromictic conditions developed during perennial episodes, probably due to salinity stratification, which enhanced preservation of organic matter in gray to black shales. These lakes formed on the floodout of a north-northwest oriented (relative to modern geography) system of mainly ephemeral streams on a broad and open floodplain. The Whitmore Point Member both overlies and interfingers laterally with alluvial red-bed facies of the Dinosaur Canyon Member of the Moenave Formation. The vertical transition from alluvial to lacustrine sedimentation recorded by the Dinosaur Canyon and Whitmore Point members of the Moenave Formation most probably resulted from a eustatically-controlled rise in base level during the Early Jurassic (Hettangian). The Dinosaur Canyon Member also interfingers laterally with eolian dune deposits of the Wingate Sandstone, which was deposited by winds that reworked coastal plain sediments to the north of the study area. Thus, on this part of the Colorado Plateau, fluvial, lacustrine and eolian sedimentary facies were deposited contemporaneously in laterally adjacent paleoenvironments.
Źródło:
Volumina Jurassica; 2008, 6, 1; 11-21
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fluvial architecture element analysis of the Brushy Basin Member, Morrison Formation, western Colorado, USA
Autorzy:
Galli, K.
Powiązania:
https://bibliotekanauki.pl/articles/2077338.pdf
Data publikacji:
2014
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
meandering
anastomosing
Morrison Formation
Kimmeridgian
Colorado
meandryzacja
anastomizacja
Formacja Morrisona
Opis:
The 85-m Brushy Basin Member of the Morrison Formation in western Colorado, USA, comprises dinosaur-bearing sandstones (architectural element CHR and CH), crevasse-splay deposits and minor levee deposits (architectural element CS), mudstones, marlstones, altered ash beds and minor limestones as well as caliche paleosols and noncalcareous paleosols (architectural element FF). Channel sandstones occur at five stratigraphic levels at Trail Through Time (TT), eleven levels at Fruita Paleontological Research Area (FP), and at five levels at Echo Canyon (EC). River-channel sandstones hosted by floodplain mudstones tend to have cut down to resistant caliche paleosols. Depositional facies and architectural element analysis show that the rivers were low gradient, mainly anastomosing, with perennial flow, but seasonal with “flashy” peaks in discharge. Dinosaur bone accumulations are found in some floodplain ponds. Isolated bones are present in anastomosing channel sandstones at TT and in channel sandstone 2 at EC. At FP, major accumulations of bones were rapidly buried in the deep pools at three bends in the meandering river resulting in the formation of channel sandstone 2. There is no evidence for a large lacustrine or playa system at the three localities.
Źródło:
Volumina Jurassica; 2014, 12, 2; 69--106
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Haplocanthosaurus (Saurischia: Sauropoda) from the lower Morrison Formation (Upper Jurassic) near Snowmass, Colorado
Autorzy:
Foster, J.
Powiązania:
https://bibliotekanauki.pl/articles/2077342.pdf
Data publikacji:
2014
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
haplocanthosaurus
sauropod
Late Jurassic
Morrison Formation
haplokantozaur
jura późna
Formacja Morrisona
Opis:
A small sauropod dinosaur collected from the Rocky Mountains of central Colorado (north of the Elk Range, Pitkin County) is assigned to the rare genus Haplocanthosaurus. The specimen, MWC 8028, consists of four dorsal centra, five partial ribs, the sacrum, five caudal vertebrae, three chevrons, five partial neural spines and many fragments and is from the lower third of the Upper Jurassic Morrison Formation. The dorsal vertebrae are procamerate, and on the sacral vertebrae the neural arch peduncles are vertically elongate and the neural spines are strongly reclined. The only sauropod from the Morrison Formation that shares these characters is Haplocanthosaurus and based on those characters MWC 8028 is referred to Haplocanthosaurus. This is at most the tenth specimen and the seventh locality for this sauropod, all within the Morrison Formation.
Źródło:
Volumina Jurassica; 2014, 12, 2; 197--210
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Palaeofloras from the Kota Formation, India: palaeodiversity and ecological implications
Autorzy:
Chinnappa, Chopparapu
Rajanikanth, Annamraju
Kavali, Pauline Sabina
Powiązania:
https://bibliotekanauki.pl/articles/2060952.pdf
Data publikacji:
2019
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Agathoxylon
floral diversity
palaeoecology
Kota Formation
India
różnorodność florystyczna
paleoekologia
Formacja Kota
Indie
Opis:
The Kota Formation of the Pranhita-Godavari Basin is well known for its fossil fauna and flora especially for its silicified woods. However, the palaeoflora and its palaeoclimatic significance within the formation are poorly known. In spite of the fact that the formation yields a rich fauna and flora chronostratigraphic problems still exist. The present study aims to analyze the palaeofloras from the Kota Formation to understand their diversity and palaeoecological significance. We also describe a new species Agathoxylon kotaense belonging to the conifer family Araucariaceae. Our study shows that the flora was dominated by conifers and that it is comparable to that of the ?Late Jurassic – Lower Cretaceous Gangapur Formation, Pranhita-Godavari Basin and that of the Rajmahal Formation of the Rajmahal hills. The growth ring pattern and leaf fossil assemblage suggest that the growth conditions were seasonal, but mostly stressed.
Źródło:
Volumina Jurassica; 2019, 17, 1; 1--16
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Folding in the Middle Jurassic Todilto Formation, New Mexico-Colorado, USA
Autorzy:
Lucas, S.
Krainer, K.
Berglof, W.
Powiązania:
https://bibliotekanauki.pl/articles/2077339.pdf
Data publikacji:
2014
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Jurassic
todilto formation
salina
microfolding
stromatolites
tepee-structures
kopalnie soli
tepee-konstrukcje
jura
Opis:
The Middle Jurassic (Callovian) Todilto Formation of northwestern New Mexico–southwestern Colorado, USA, is a carbonate/evaporite lithostratigraphic unit that was deposited in a large paralic salina culminated by a gypsiferous evaporitic lake. Intraformational folds of the limestone-dominated lower part of the Todilto Formation (Luciano Mesa Member) range in scale from millimeters to meters, and many of the large folds are the loci of uranium mineralization. A diverse literature has attributed the formation of intraformational folds of the Todilto Formation to several causes, including syndepositional or postdepositional tectonics, soft-sediment deformation due to sediment loading or gravity sliding, diagenetic alteration (primarily the hydration/crystallization of gypsum/anhydrite), the growth of stromatolitic bioherms or the formation of tepee-like structures. We examine in detail two characteristic outcrops of intraformational folds in the Todilto Formation, in west-central New Mexico, to conclude that folds and domal structures present in the Todilto limestone facies at different stratigraphic levels and at different scales have resulted from varied processes that produced dome-like stromatolitic mounds, tepee-like structures, small-scale enterolithic folds and large-scale folds of likely diagenetic origin.
Źródło:
Volumina Jurassica; 2014, 12, 2; 39--54
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pseudosonninia, a new genus of oppeliid ammonite (Haploceratoidea) from the Callovian (Middle Jurassic) of the Neuquén Basin, Argentina
Autorzy:
Parent, Horacio
Garrido, Alberto C.
Schweigert, Günter
Brambilla, Luciano
Powiązania:
https://bibliotekanauki.pl/articles/2060951.pdf
Data publikacji:
2019
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
ammonites
Callovian
Los Molles Formation
Chacay Melehué
Argentina
amonity
Kelowej
Formacja Los Molles
Argentyna
Opis:
From the uppermost part of the Los Molles Formation (upper Lower and lower Middle Callovian) in Chacay Melehué (Neuquén Province, Argentina), a group of hecticoceratine ammonites with a conspicuous morphology not assimilable to any known genus of this subfamily has been recently discovered. These forms are inflated oxycones with a prominent, sharp keel developed from the juvenile phragmocone up to the adult peristome. The new genus Pseudosonninia is established on the basis of these ammonites, with Pseudosonninia chacaymelehuensis n. gen. n. sp. as its type species. The new genus seems to be endemic to the Neuquén Basin and is recorded here from the upper Lower and lower Middle Callovian of Chacay Melehué and Río de Los Patos.
Źródło:
Volumina Jurassica; 2019, 17, 1; 39--48
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A U/Pb age for the Mygatt-Moore Quarry, Upper Jurassic Morrison Formation, Mesa County, Colorado
Autorzy:
Trujillo, K.
Foster, J.
Hunt-Foster, R.
Chamberlain, K.
Powiązania:
https://bibliotekanauki.pl/articles/2077340.pdf
Data publikacji:
2014
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Morrison Formation
U-Pb dating
CA-TIMS
dinosaurs
North American Jurassic
Formacja Morrisona
dinozaury
Opis:
Mygatt-Moore Quarry in the Brushy Basin Member of the Upper Jurassic Morrison Formation is one of the more important large dinosaur quarries in the formation, yielding fossils of sauropod dinosaurs including Apatosaurus, Camarasaurus, and an indeterminate diplodocine (cf. Diplodocus or Barosaurus), the theropod dinosaurs Allosaurus and Ceratosaurus, and the ornithischians Othnielosaurus and Mymoorapelta. Fossil wood and carbonized plants are known from the deposit, and carbonized dinosaur skin has also been discovered. We report here on a new U/Pb radiometric age for the Mygatt-Moore Quarry, from a smectitic mudstone collected at the quarry horizon. We isolated zircons using an ultrasonic separation technique and standard heavy liquid and magnetic methods, analyzed single zircons using a chemical abrasion method (CA-TIMS). The age determined for this dinosaur quarry, 152.18 ±0.29 Ma, places the quarry at the boundary between the Kimmeridgian and Tithonian stages of the Late Jurassic Period. This age can now be used to place the quarry into stratigraphic position with respect to other dated horizons in the Morrison Formation and other rock units worldwide. We will also use this age along with other ages to create a radiometrically based stratigraphic framework for the Morrison Formation.
Źródło:
Volumina Jurassica; 2014, 12, 2; 107--114
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Osteology of a large allosauroid theropod from the Upper Jurassic (Tithonian) Morrison Formation of Colorado, USA
Autorzy:
Dalman, S.
Powiązania:
https://bibliotekanauki.pl/articles/2077330.pdf
Data publikacji:
2014
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
dinosaur
theropoda
allosauridae
Morrison Formation
Upper Jurassic
Colorado
dinozaury
teropody
allozaury
Formacja Morrisona
górna jura
Opis:
Two partial skeletons of allosaurid theropods belonging to an adult and a juvenile from the Upper Jurassic (Tithonian) Morrison Formation of McElmo Canyon in Montezuma County, southwestern Colorado, were discovered in 1953 by the late Joseph T. Gregory and David Techter. The adult specimen consists of several isolated cranial and postcranial skeletal elements that are exceptionally well-preserved and include the left premaxilla, maxilla, dentary, teeth, quadratojugal, two caudal vertebrae, pubic peduncle, ischium, proximal tibia, a nearly complete left foot, and several isolated teeth, whereas the juvenile specimen is represented by the distal portion of the right dentary and a fragmentary splenial. The specimens represent a new species of Allosaurus, here named Allosaurus lucasi, which differs from Allosaurus fragilis by having a relatively short premaxilla and robust quadratojugal with short jugal process and a short quadrate process of the quadratojugal that is at the same level as the rostral quadratojugal ramus. The presence of a new species of Allosaurus in the Tithonian of North America provides further evidence of the taxonomic and morphological diversity of the Allosauridae clade and their continuous evolutionary success, which extended to the Cretaceous.
Źródło:
Volumina Jurassica; 2014, 12, 2; 159--180
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
New magnetostratigraphy and paleopole from the Whitmore Point Member of the Moenave Formation at Kanab, Utah
Autorzy:
Steiner, M.
Powiązania:
https://bibliotekanauki.pl/articles/2077331.pdf
Data publikacji:
2014
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
hettangian magnetostratigraphy
Moenave Formation
normal polarity
paleopole
J-1 cusp
Formacja Moenave
normalna polaryzacja
szpic J-1
Opis:
The entire Whitmore Point Member of the Moenave Formation was sampled in close stratigraphic sequence (+0.3 m) from a vertical exposure in southwestern Utah. The polarity sequence in the Whitmore Point Member is essentially normal polarity, with five or more very short reversed intervals interspersed and a <1 m reversed interval at the top of the sequence. This polarity pattern dates the Whitmore Point Member as Hettangian. In the earliest Jurassic, the North American plate rotated even further westward from its Late Triassic position, and the movement appears to have been accompanied by an abrupt increase in plate motion because of the similarity in position of many Late Triassic paleopoles. The Moenave pole forms the ‘J-1 cusp’ of the North American apparent polar wander curve. The paleopole obtained by this study is somewhat further westward than those of previous studies. Within the 27 m of a mostly normal polarity sequence, the data show multiple, exceedingly short polarity intervals. The magnetization carrier is a maghemite-magnetite mineral, with the magnetization of an additional hematite carrier superposed. The lithostratigraphic sequence of the Moenave Formation is terminated by an unconformable surface, overlain by the Springdale Sandstone. Paleomagnetic directions of the Whitmore Point Member are exceedingly similar to those of the overlying Springdale Sandstone. Even though the two lithologic bodies are separated by a clear disconformity, the similarity in pole positions suggests that the two are closely related in time. It is possible that this disconformity represents the termination of the westward excursion of North America in earliest Jurassic time.The entire Whitmore Point Member of the Moenave Formation was sampled in close stratigraphic sequence (+0.3 m) from a vertical exposure in southwestern Utah. The polarity sequence in the Whitmore Point Member is essentially normal polarity, with five or more very short reversed intervals interspersed and a <1 m reversed interval at the top of the sequence. This polarity pattern dates the Whitmore Point Member as Hettangian. In the earliest Jurassic, the North American plate rotated even further westward from its Late Triassic position, and the movement appears to have been accompanied by an abrupt increase in plate motion because of the similarity in position of many Late Triassic paleopoles. The Moenave pole forms the ‘J-1 cusp’ of the North American apparent polar wander curve. The paleopole obtained by this study is somewhat further westward than those of previous studies. Within the 27 m of a mostly normal polarity sequence, the data show multiple, exceedingly short polarity intervals. The magnetization carrier is a maghemite-magnetite mineral, with the magnetization of an additional hematite carrier superposed. The lithostratigraphic sequence of the Moenave Formation is terminated by an unconformable surface, overlain by the Springdale Sandstone. Paleomagnetic directions of the Whitmore Point Member are exceedingly similar to those of the overlying Springdale Sandstone. Even though the two lithologic bodies are separated by a clear disconformity, the similarity in pole positions suggests that the two are closely related in time. It is possible that this disconformity represents the termination of the westward excursion of North America in earliest Jurassic time.
Źródło:
Volumina Jurassica; 2014, 12, 2; 13--22
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
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