scholarly journals Bone microstructure and diagenesis of saurischian dinosaurs from the Upper Cretaceous (Neuquén Group), Argentina

2017 ◽  
Vol 44 (1) ◽  
pp. 39 ◽  
Author(s):  
Elena Previtera
Keyword(s):  
Upper Cretaceous ◽  
Bone Microstructure ◽  
Depositional Environments ◽  
Integral Approach ◽  
Burial History ◽  
Thin Sections ◽  
Diagenetic Processes ◽  
History Of ◽  
Diagenetic History ◽  
Fluvial Environments

The Neuquén Basin in northwestern Patagonia, Argentina, holds the most important record of Cretaceous dinosaurs in South America.The Neuquén Group (Upper Cretaceous) is the richest dinosaur-bearing unit of the basin. It comprises the Río Limay, the Río Neuquén and the Río Colorado subgroups. In this study, dinosaur remains from the Río Neuquén and the Río Colorado subgroups outcropping in Mendoza are examined. In this group, isolated, disarticulated or partially articulated sauropods and theropods are abundant. However, little is known about the diagenetic history of fossil assemblages. In southern Mendoza, three fossiliferous sites were found in the areas of Paso de las Bardas (Quebrada Norte) and Cerro Guillermo (CG1, CG2). This study aims to add to the knowledge of diagenetic processes involving dinosaur remains from the Neuquén Group, as well as their relation to the depositional environment. Histologic features and diagenetic processes of dinosaur bones were analyzed through thin sections in order to interpret the degree of taphonomic alteration. The fossil-diagenetic processes inferred include substitution, fracturing, plastic deformation and different permineralization events. Combined analyses through X-ray diffractometry (XRD) and petrographic studies reveal the substitution of hydroxyapatite by francolite. The presence of fluorine -in one of the cases- suggests a link between the elemental composition and depositional environments: floodplain and fluvial channel. Permineralization stages include infilling of vascular canals, trabeculae and fractures with iron oxides and iron carbonate minerals during the burial history. This contribution represents an integral approach to the study of Cretaceous dinosaurs for assessing the diagenetic changes in the bone microstructure and the differential preservation of fossil remains in fluvial environments.

scholarly journals Petrography And Diagenetic History Of The Kometan Formation (Upper Cretaceous) In The Imbricated Zone, Iraqi Kurdistan Region

2020 ◽  
Vol 70 (1) ◽  
pp. 195-208
Author(s):  
Irfan Sh. Asaad ◽  
◽  
Sardar M. Balaky ◽  
Keyword(s):  
Upper Cretaceous ◽  
Planktonic Foraminifera ◽  
Kurdistan Region ◽  
Thin Sections ◽  
Iraqi Kurdistan ◽  
Diagenetic Processes ◽  
History Of ◽  
Diagenetic History ◽  
Petrographic Study ◽  
Late Stages

The petrography and diagenetic history of Upper Cretaceous Kometan Formation is investigated from its type locality in Kometan Village, Imbricated Zone, Kurdistan Region, Northeastern Iraq. The formation comprised 44 m of white weathered, light grey, thin to medium bedded fractured limestones with chert nodules and lenses in the upper part. The petrographic study of the formation is based on 50 thin sections and showed that the majority of limestones microfacies are carbonate mud (micrite). The skeletal grains include planktonic foraminifera, oligostegina, calcisphers, ostracods, pelecypods, larvae ammonoids and echinoderms. Non-skeletal grains include peloids only. The Kometan Formation has been subjected to several diagenetic processes such as: micritization, dolomitization, cementation, neomorphism, compaction, silicification, solution, phosphatization, glauconitization and fracturing. All these occurred during marine phreatic shallow burial stage and activated during intermediate to deep burial and uplifting in the late stages. The paragenetic history of the Kometan Formation has passed through four diagenetic environments including; marine, meteoric, burial and uplifting.

scholarly journals Taphonomic analysis of saurischian dinosaurs from the Plottier Formation (Upper Cretaceous), Mendoza, Argentina

2019 ◽  
Vol 46 (2) ◽  
pp. 345 ◽  
Author(s):  
Elena Previtera
Keyword(s):  
Upper Cretaceous ◽  
Holistic Approach ◽  
Depositional Environments ◽  
Continental Deposits ◽  
Wide Range ◽  
History Of ◽  
Fossil Assemblages ◽  
Vertebrate Assemblage ◽  
Taphonomic Analysis ◽  
Fluvial Environments

The uppermost Cretaceous continental deposits of the Neuquén Basin (west-central Argentina) have yielded a high diversity vertebrate assemblage, including numerous dinosaur species. The Neuquén Group is the richest unit in remains of dinosaur of the basin and comprises the Río Limay, the Río Neuquén and the Río Colorado subgroups. In this group, there is abundance of isolated, disarticulated or partially articulated sauropods and theropods. However, little is known about the taphonomic history of fossil assemblages. In this study, dinosaur remains from the Plottier Formation (late Coniacian-early Santonian) found in the Cerro Guillermo area in southern Mendoza are examined. The investigation of fossil occurrences within the study area revealed the existence of different taphonomic modes, from isolated bones until partially articulated skeletons preserved in deposits of floodplain and fluvial channel settings. SEM-EDS analysis showed the substitution of hydroxyapatite by francolite in the bone microstructure. The presence of fluorine-in one of the cases-suggested a link between the elemental composition and depositional environments: floodplain and fluvial channel. The survey of the vertebrate accumulation types and their sedimentary context allowed documenting a wide range of processes responsible for their genesis, operating within a meandering fluvial environment. This contribution represents a holistic approach about taphonomic history of Cretaceous dinosaurs for assessing the differential preservation of fossil assemblages in fluvial environments.

scholarly journals Linking Depositional Environments and Diagenetic Processes to Porosity Evolution and destruction in the Arab Formation reservoirs, Offshore oilfields of Qatar

2020 ◽  
Author(s):  
Fadhil N. Sadooni ◽  
Hamad Al-Saad Al-Kuwari ◽  
Ahmad Sakhaee-Pour ◽  
Wael S. Matter
Keyword(s):  
Depositional Environments ◽  
Oil Reservoir ◽  
Secondary Porosity ◽  
Future Directions ◽  
Thin Sections ◽  
Intergranular Porosity ◽  
Porosity Evolution ◽  
Diagenetic Processes ◽  
Exploration And Production ◽  
The Impact

Introduction: The Jurassic Arab Formation is the main oil reservoir in Qatar. The Formation consists of a succession of limestone, dolomite, and anhydrite. Materials and methods: A multi-proxy approach has been used to study the Formation. This approach is based on core analysis, thin sections, and log data in selected wells in Qatar. Results: The reservoir has been divided into a set of distinctive petrophysical units. The Arab Formation consists of cyclic sediments of oolitic grainstone/packstone, foraminifera-bearing packstone-wackestone, lagoonal mudstone and dolomite, alternating with anhydrite. The sediments underwent a series of diagenetic processes such as leaching, micritization, cementation, dolomitization and fracturing. The impact of these diagenetic processes on the different depositional fabrics created a complex porosity system. So, in some cases there is preserved depositional porosity such as the intergranular porosity in the oolitic grainstone, but in other cases, diagenetic cementation blocked the same pores and eventually destroyed them. In other cases, diagenesis improved the texture of non-porous depositional texture such as mudstone through incipient dolomitization creating inter-crystalline porosity. Dissolution created vugs and void secondary porosity in otherwise non-porous foraminiferal wackestone and packstone. Therefore, creating a matrix of depositional fabrics versus diagenetic processes enabled the identification of different situations in which porosity was either created or destroyed. Future Directions: By correlating the collected petrographic data with logs, it will become possible to identify certain “facio-diagenetic” signatures on logs which will be very useful in both exploration and production. Studying the micro and nano-porosity will provide a better understanding of the evolution and destruction of its porosity system.

Climatic and oceanographic isotopic signals from the carbonate rock record and their preservation

1992 ◽  
Vol 129 (2) ◽  
pp. 143-160 ◽  
Author(s):  
James D. Marshall
Keyword(s):  
Ocean Circulation ◽  
Global Climate ◽  
Burial History ◽  
Vegetative Cover ◽  
Isotopic Data ◽  
Rock Interaction ◽  
Diagenetic Alteration ◽  
Wide Range ◽  
History Of ◽  
Diagenetic History

AbstractStable isotopic data from marine limestones and their constituent fossils and marine cements can provide quantitative evidence for changes in global climate and ocean circulation. Oxygen isotopic data can indicate changes in temperature and ocean composition whereas stratigraphic variation in carbon isotope ratios may reflect changes in the carbon cycle that can be linked to changes in oceanic productivity and atmospheric greenhouse gases. Terrestrial carbonates–meteoric cements, calcretes and speleothems–similarly offer significant potential for understanding the evolution of terrestrial climates by providing evidence for the composition of rainwater and the nature of vegetative cover.Primary environmental isotopic signals may be obscured by the effects of post-depositional diagenetic alteration. Cementation and replacement reactions can take place in a wide range of diagenetic environments; the diagenetic history of an individual limestone is determined by a combination of its mineralogical diagenetic potential and depositional setting, together with subsequent changes in relative sea-level and burial history. Carbon isotopic values are less prone to alteration during diagenesis than oxygen values but shifts can be significant where organogenic carbon is incorporated. Linear covariation of carbon and oxygen values is not a reliable indicator of diagenetic alteration: water-rock interaction and fluid mixing may produce non-linear distributions.Attempts to determine long-term changes in climatic and oceanographie conditions through isotope stratigraphy of shallow-water limestones must include an assessment of the diagenetic history of the materials analysed. Pétrographic examination using conventional microscopy backed up, where appropriate, by cathodoluminescence and scanning electron microscopy together with elemental and strontium isotopic analysis can help to identify the effects of diagenetic alteration. Where material with a range of different degrees of alteration is preserved in the same sediment it may be possible to compare patterns of isotopic and elemental variation and to attempt to unravel the effects of diagenesis in order to determine primary, environmental, isotopic signals. Recent research has shown that these techniques can be successfully employed in both Phanerozoic and Precambrian sediments.

Depositional Environment and Diagenesis processes impact on the carbonate rock quality: a case study, southeastern of Iraq

2019 ◽  
Vol 60 (5) ◽  
pp. 1104-1114
Author(s):  
Afrah Hassan Saleh
Keyword(s):  
High Energy ◽  
Negative Influence ◽  
Depositional Environments ◽  
Carbonate Reservoir ◽  
Reservoir Properties ◽  
Thin Sections ◽  
Diagenetic Processes ◽  
Marine Lagoon ◽  
Lagoon Environment ◽  
Low Porosity

Deposition environment and diagenesis processes are very important factors which affect and control the reservoir properties.  The carbonate Mishrif Formation has been selected as a carbonate reservoir in selected wells from southeastern Iraq to understand the influence of the Deposition environment and diagenesis processes on the carbonate reservoir. A core examination of thin sections, shows that Mishrif Formation comprises of six depositional environments, these are: deep marine, lagoon, rudist biostrome, back shoal, and shallow open marine.  These environments have effect by many diagenetic processes, including dolomitization, dissolution, micritization, cementation, recrystallization and Stylolite, some of these processes have improved the reservoir properties of the Mishrif reservoir, these are: dissolution, dolomitization and the stylolization.  The others diagenetic processes have negative influence on the Petrophysical properties, such as cementation, compaction, and recrystallization processes, which damage the porosity and decrease the pore size. The reservoir properties are controlled by deposition environment, where lagoon environment is mostly compact with low porosity, shoal environment reflects a high energy and grain-supported environment and has good reservoir potential, deep-marine environments consist of mudstone to wackestone, which represents low energy level with low porosity and represents the non-reservoir environment.

Taphonomy, age, and paleoecological implication of a new Pachyrhinosaurus (Dinosauria: Ceratopsidae) bonebed from the Upper Cretaceous (Campanian) Wapiti Formation of Alberta, Canada

2015 ◽  
Vol 52 (4) ◽  
pp. 250-260 ◽  
Author(s):  
Federico Fanti ◽  
Philip J. Currie ◽  
Michael E. Burns
Keyword(s):  
North America ◽  
Upper Cretaceous ◽  
Oxbow Lakes ◽  
Burial History ◽  
Western Interior Seaway ◽  
History Of ◽  
Depositional Setting ◽  
Horseshoe Canyon Formation ◽  
Average Bone ◽  
Upper Campanian

The Grande Prairie region (Alberta, Canada) includes some of the richest Cretaceous fossil sites in North America, including the recently described bonebed of Pachyrhinosaurus lakustai at the Pipestone Creek locality. Here we describe a new multi-taxa, ceratopsian-dominated bonebed from the region, integrating taphonomic, radioisotopic, and paleoecological data. The bonebed can be traced for 107 m and has been excavated over an area of 40 m2 with an average bone density of 30–50 elements/m2. The new bonebed occurs within Unit 4 of the upper Campanian Wapiti Formation, and 40Ar/39Ar dating provides an age of 71.89 ± 0.14 Ma, thus making the site equivalent in age to the upper Drumheller Member of the lower Horseshoe Canyon Formation of central Alberta. About 88% of vertebrate remains are ceratopsian, and dromaeosaurid, hadrosaurid, troodontid, and tyrannosaurid remains have also been identified. Juvenile material, although scarce, indicates an assemblage of individuals of different ages. Specimens showed no strong preferred two-dimensional orientation but are clearly sorted vertically. Taphonomic and sedimentological interpretation support a complex pre-burial history of preserved elements as well as a depositional setting characterized by persistent waterlogged conditions as those typical of large oxbow lakes or marshy/swampy areas, as well as lacustrine settings within an alluvial plain. Being located more than 450 km inland from the paleo-coastline, the new bonebed represents one of the farthest-known inland occurrence of centrosaurines in North America, further supporting the presence of large aggregations of ceratopsian far from the coastal lowlands of the Western Interior Seaway.

Rock-physics modeling guided by depositional and burial history in low-to-intermediate-porosity sandstones

Geophysics ◽  
2014 ◽  
Vol 79 (2) ◽  
pp. D115-D121 ◽  
Author(s):  
Per Avseth ◽  
Tor Arne Johansen ◽  
Aiman Bakhorji ◽  
Husam M. Mustafa
Keyword(s):  
Rock Physics ◽  
Contact Theory ◽  
Well Log ◽  
Tight Gas ◽  
Burial History ◽  
Reservoir Properties ◽  
Rock Physics Modeling ◽  
History Of ◽  
Physics Modeling ◽  
Diagenetic History

We present a new rock-physics modeling approach to describe the elastic properties of low-to-intermediate-porosity sandstones that incorporates the depositional and burial history of the rock. The studied rocks have been exposed to complex burial and diagenetic history and show great variability in rock texture and reservoir properties. Our approach combines granular medium contact theory with inclusion-based models to build rock-physics templates that take into account the complex burial history of the rock. These models are used to describe well log data from tight gas sandstone reservoirs in Saudi Arabia, and successfully explain the pore fluid, rock porosity, and pore shape trends in these complex reservoirs.

scholarly journals Diagenetic history of the upper Tanglewood Member (upper Ordovician) of the Lexington Limestone, central Kentucky, U.S.A. with special emphasis on petrographic differences between deformed and undeformed beds

2017 ◽  
Vol 53 ◽  
pp. 9-16
Author(s):  
Dibya Raj Koirala ◽  
Frank R. Ettensohn
Keyword(s):  
Upper Ordovician ◽  
Diagenetic Processes ◽  
Lexington Limestone ◽  
History Of ◽  
Sediment Deformation ◽  
Diagenetic History ◽  
Petrographic Study

Petrographic study was carried out for the upper Tanglewood Member (upper Ordovician) of the Lexington Limestone in order to understand its diagenetic history and predict whether the cementation is pre-deformational or post-deformational by comparing the deformed and undeformed beds of the same horizon. This study shows that the diagenetic processes, which have modified the sequence of the upper Tanglewood Member of the Lexington Limestone, consist of micritization, cementation, compaction, dolomitization and internal filling. Moreover, it indicates that the main episode of cementation took place after the sediment deformation.

Sign in / Sign up

Export Citation Format

Share Document