Hasil untuk "Paleontology"

M. Balini, M. Horacek, I. Lazăr et al.

Muhammad Tayyab Naseer, Sultan Alshehery, Ilyas Khan et al.

Abstract Incised valley sandfills are globally renowned for forming excellent stratigraphic traps. These incised valleys are developed during the extensively falling stage of the sea, followed by a negligible rise, which fills the incised valleys with coarse-grained reservoir facies. However, sea-level fluctuations cause fluctuations in the lateral distribution of the reservoir. Hence, it becomes very difficult to simulate the exact thickness, impedances, and lateral phase changes. Hence, these might act as direct hydrocarbon indicators (DHI). Therefore, this study applies the state-of-the-art spectral decomposition and static acoustic impedance reservoir simulations tool to determine the thin-bedded reservoirs within a stratigraphically complex unit for implicating the future well drilling strategies for the known gas field of Indus Onshore, Pakistan. The key emphasis was given to the selection and optimizations of the spectral waveform-based simulations. The outcomes of these simulations were to develop strategies for horizontal well drillings. The stratigraphic traps are NNW-SSE oriented with localized transpressional fault-controlled components. These fault-controlled components have played a vital role in the upward migration of hydrocarbon-bearing reservoir facies. The 21-Hz, 29-Hz, and 41-Hz tuning blocks outline the hydrocarbon-bearing sand-filled reservoir facies inside the Lowstands system tract (LST). The 57-Hz tuning block recognizes the transgressive seal facies at the top of the LST. The bandlimited static reservoir model (SRM) shows some noise events within the sedimentary reflections. The 21-Hz spectral wavelet-based developed SRM has enhanced the signal-to-noise (S/N) ratio for imaging a 34 m thick sand-filled lens. Consequently, this study serves as an analog for global shallow-marine incised valley systems.

Xiao-Kang Lu, Xiao-Kang Lu, Tao Deng et al.

This study presents the first phylogenetic analysis focused on the subfamily Aceratheriinae to date, with 392 characters (361 parsimony-informative characters) coded from 50 taxa at the species level. We added 80 newly defined and 33 revised characteristics to an existing matrix, covering features of the skull, teeth, and postcranial bones. Based on the results of ordered and unordered analyses, combined with a diagnosis in accordance with traditional morphological taxonomy, we revised the diagnosis of Aceratheriinae and reconstructed the phylogeny of Aceratheriinae. The tribe Teleoceratini, as well as the tribe Aceratheriini, was reclassified within Aceratheriinae; however, the traditionally established contents of each tribe were changed somewhat. Aceratheriinae underwent evolutionary adaptation several times during the early stages of its evolution, and several genera are herein reconstructed as early-diverging taxa, such as Floridaceras, Chilotheridium, and Plesiaceratherium. Turkanatherium and Protaceratherium are excluded from Aceratheriinae in this study. We suggest another two subclades of Aceratheriinae, containing Hoploaceratherium and Aprotodon, respectively. Aceratheriini and Teleoceratini are redefined as two highly specialized groups of Aceratheriinae.

Zulma Gasparini, Leonardo Salgado, Julia B. Desojo

Los inicios de la paleoherpetología argentina se remontan a los orígenes de la ciencia en el país. En sus primeras décadas fueron clave el Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” en la Ciudad Autónoma de Buenos Aires y el Museo de La Plata en la misma provincia. A estos dos, se sumaron un importante número de instituciones científicas en diferentes provincias, como museos municipales y provinciales, universidades nacionales o nuevos institutos de investigación del CONICET, que se desarrollaron a partir del incremento de nuevas líneas de estudio y la formación de colecciones. Asimismo, las instituciones se fortalecieron con la incorporación de jóvenes paleoherpetólogos de esas mismas provincias o de otras partes del país y del extranjero. En la actualidad, un número importante de investigadores y técnicos, entre ellos ilustradores y paleoartistas, se dedican al desarrollo de la disciplina, contribuyendo no solo al incremento del conocimiento paleoherpetológico, tanto científico como divulgativo, sino también al mantenimiento de los parques naturales y la promoción de turismo.

DEBRA L. HANNEMAN , DONALD LOFGREN , STEPHEN T. HASIOTIS et al.

Sanidine 40Ar/39Ar ages of lapilli tuffs and the mammalian fauna of Pipestone Springs strata provide a high-resolution chronostratigraphy for upper Eocene (Priabonian) rock units in southwestern Montana. Two felsic lapilli tuffs with weighted-mean 40Ar/39Ar single crystal sanidine ages of 37.50±0.02 Ma and 36.00±0.20 Ma both fall within the Priabonian, late Eocene. These tuffs occur within the basal to upper part of the 55 m of exposed Pipestone Springs strata. The uppermost 15 m yield a diverse and abundant assemblage of mostly small-bodied middle Chadronian (Priabonian, late Eocene) mammals. The older lapilli tuff is an ashfall tuff, whereas the younger lapilli tuff exhibits minor aeolian reworking. The new 40Ar/39Ar age constraints significantly increase the age range of Pipestone Springs strata to include uppermost Duchesnean–lowermost Chadronian (Priabonian, upper Eocene) deposits in addition to its well-known middle Chadronian vertebrate assemblage. These new 40Ar/39Ar ages combined with its mammalian fauna further support Pipestone Springs strata as age-correlative to the Flagstaff Rim section in central Wyoming, and provide a basis for better determining late Eocene mammalian paleogeography and regional paleolandscapes in the United States Rocky Mountain to Great Plains areas. Loessites intercalated with paleosols dominate Pipestone Springs deposits. The recognition of loessites comprising these strata is a new depositional interpretation of Pipestone Springs strata, making these loessites some of the oldest known aeolian Eocene strata in the Great Plains–Rocky Mountains region. Pipestone Springs paleosols developed on lapilli tuffs are vertisols. Alfisols and inceptisols, developed from a parent material of volcanic glass mixed with non-volcanic grains, are the remaining paleosols within the loessite strata. Additionally, a new and important discovery in this project is the recognition that all paleosols are extensively bioturbated, containing trace fossils similar to Rebuffoichnus and newly identified trace fossils resembling Feoichnus, Eatonichnus, Fictovichnus, and Coprinisphaera.

Reza Omidi, Abbas Sadeghi, Mahboobeh Hosseini-Barzi et al.

Abstract Biostratigraphic studies of the Sarvak and Ilam formations in wells No. 1 and 14 of the Abteymour Oil Field led to the recognition of six species of foraminifers from the two mentioned formations for the first time. In this research, the species of Fischerina carinata and Spiroloculina cenomana in the Sarvak Formation and the species of Palaeosigmoilopsis apenninica and Sigmomassilina ottadunensis in the Sarvak and Ilam formations belonging to the suborder of MILIOLINA Delage and Herouard (1896) and the species Rotorbinella sp. nov. in the Sarvak and Ilam formation and Pararotalia boixae in the Sarvak and Ilam formations belonging to the suborder of ROTALIINA Delage and Herouard (1896) were identified and described. These species are not yet reported from the Sarvak and Ilam formations. Based on the identified fauna, the Sarvak Formation with a thickness of 812.98 and 238 meters in wells No. 1 and 14 respectively is Cenomanian–Turonian in age, and the Ilam Formation with a thickness of 151.7 and 136 meters in wells No. 1 and 14 respectively is Santonian–Campanian? in age. Keywords: Abeteymour Oil Field, Ilam Formation, Foraminifera, Rotaliidae, Sarvak Formation   Introduction The Sarvak and Ilam formations, as one of the most important carbonate hydrocarbon reservoirs after the Asmari reservoir in the Zagros Basin, have special importance in petroleum studies. So far, several studies have been conducted on the two mentioned formations from different aspects especially biostratigraphic studies (James and Wynd 1965; Wynd 1965; Wood and Lacassagne 1956; Wells 1966, 1967, 1968; Stoneley et al. 1975; Speers 1967; Rahimpour-Bonab et al. 2012; Omidvar et al. 2014; Amiri Bakhtiar 1991; Khosroo Tehrani and Fonooni 1994; Allahbakhsh Ghiyasvand 2003; Teimourian 2004; Akbari Bas Kelayeh and Taheri 2005, 2006; Kamyabi Shadan 2005; Agh 2005; Sadeghi et al. 2006; Ghalavand 2009; Soleimani 2010; Ghobeyshavi et al. 2010; Sajjadi and Omidvar 2011; Omidvar 2011). However, these biostratigraphic studies of the Sarvak and Ilam formations in different areas of the Zagros Basin, introducing several biozones, some coexistence of foraminifera in these zones have been introduced   . In the Dezful Embayment, due to the tectonic phases that occurred after Cenomanian and after Turonian (sub Hercynian tectonic phases), there is some absence of stratum or hiatus. The shallowing trend of the Late Albian to Cenomanian basin produced large amounts of shallow carbonate sediments of the Sarvak Formation in the Zagros Basin. However, during the Late Turonian, a regional uplift has taken place causing partial or complete erosion of the Turonian sediments, which create an erosional unconformitiy after Turonian, characterized by the development of iron-bearing sediments and sedimentary discontinuities in the Dezful Embayment and Fars areas. Omidi et al. 2018, in order to identify the fossil content with an emphasis on recognizing foraminifera of the Sarvak and Ilam formations in the south of Dezful embayment, studied two subsurface sections of wells 1 and 14 of the Abteymour oil field. They introduced four biozones based on the identification of 71 species belonging to 57 genera of foraminifera: one biozone in the Ilam Formation, called Biozone No. 1: Rotorbinella-Pararotalia Assemblage Zone, and three biozones in the Sarvak Formation called biozone No. 2: Nezzazatinella picardi-Dicyclina Schlumbergeri Assemblage Zone; biozone No. 3: Rotorbinella mesogeensis Total Range Zone and biozone No. 4: Nezzazata-alveolinid Assemblage Zone. Based on these identified biozones, the ages of the Sarvak and the Ilam formations are Cenomanian–Turonian and Santonian–Campanian, respectively. The identified benthic foraminifera in the Abteymour Oil Field is somehow similar to the other parts of the Zagros, but in addition to the benthic foraminifera reported in previous studies of these two formations; six other foraminifera species are identified and introduced from this oil field for the first time in this research. Since the Ilam and Sarvak formations face several high-pressure zones during drilling in the Abteymour oil field, identification of high-pressure oil and gas zones in strata is one of the issues that are of great importance. As a result, fossil studies, especially foraminifera can be helpful in finding the relative and sometimes exact location of high-pressure zones. The Ilam Formation in drilled wells in parts of the south of Dezful Embayment (Abteymour Oil Field) has low interest in terms of diversity of fossil genera and species (foraminifera); however, some foraminiferal members have been less studied, for example, the genus and species of the Rotaliidae family. In addition to the introduction of the Rotalia sp. 22-algae assemblage zone (due to the high diversity of Rotaliidae family members, sometimes up to 60 species, sp. 60) in the James and Wynd (1965) studies, and the high focus of systematic studies by Hottinger et al. (2014) on this family confirms the complexity and importance of the study in identifying and distinguishing the genus and species of this family; therefore, geologists on oil wells in Iran know the Ilam Formation as the "Rotalia Formation". Thus, the importance of the systematic study of the Rotaliidae family for separation of genera and species is more important. In this study, the foraminifera of the Ilam Formation have been systematically studied (to separate and distinguish several genera and species of Rotaliidae from each other), and this can be used to complete the chain of biostratigraphic studies in identifying high-pressure oil zones. In the Sarvak Formation, the study and knowledge of benthic foraminifera fossil assemblages could have great importance in the enrichment of fauna associations  and recognizing biostratigraphic zones, determining the exact age of strata, knowing more local biozones, and identifying oil zones. Also, the rate of change in the diversity and abundance of foraminifera and their morphological characteristics increases in anoxic periods, for example, OAE1a (Leckie et al. 2002; Erba 2004). However, one of the biological characteristics of this incident is the presence of planktonic foraminifera with elongated chambers (Coccioni et al. 2006). However, here it is enough to describe the species that have been reported for the first time from the Sarvak and Ilam formations to identify more foraminifera and the fauna associations in the enrichment of the biozonations related to these two formation..   Material & Method In order to do biostratigraphy and identifying foraminifera in the Sarvak and Ilam formations in Abteymour Oil Field, the two wells of No.1 and 14, with the most suitable sample, were selected.A total of 1347 thin sections of the two wells (716 thin sections from well No. 1, mainly prepared from drilling cuttings and 631 thin sections from well No. 14, mostly prepared from drilling cores) were studied. These thin sections were studied microscopically to identify the microfossil contents, and after identification, they were photographed. Identification and description of the foraminifera were performed based on Loeblich and Tappan (1988), Boix (2007), Chiocchini et al. (2012), and Hottinger (2014).   Discussion of Results & Conclusions The Sarvak and Ilam formations (Bangestan oil reservoir) are considered the second largest oil reservoir in Iran after the Asmari reservoir. Therefore, a careful study of the fossil content of these two oil formations is of particular importance in biostratigraphic studies. For this reason, in this study, a detailed study of the fossil content (especially foraminifera) of these two formations has been considered. The Ilam Formation in wells No. 1 and 14 has a thickness of 152 and 136 meters, respectively, and its lithology is mainly limestones and limestone with shale interbeds. The Sarvak Formation in well No. 1 is 813 meters thick, and in well No. 14, 238 meters of the Sarvak Formation has been drilled. The lithology of the Sarvak Formation is mainly limestones and dolomitic limestones. The biostratigraphy of the Sarvak and Ilam formations in wells No. 1 and 14 of Abteymour Oil Field, in addition to benthic foraminifera, which has been reported in previous studies of the Sarvak and Ilam formations, the following six benthic foraminifera are identified and introduced for the first time from these two formations:1-  Fischerina carinata Peybernès, 1984 (Cenomanian, Sarvak Formation); 2-  Spiroloculina cenomana Chiocchini, 2008 (Cenomanian, Sarvak Formation); 3-  Sigmomassilina ottaduenesis Chiocchini, 2008 (Turonian, Sarvak Formation and Santonian–Campanian?, Ilam formations); 4-  Paleosigmoilopsis apenninica Chiocchini, 2008 (Cenomanian–Turonian, Sarvak Formation); 5-  Pararotalia boixae Piuz and Meister, 2013 (Cenomanian, Sarvak Formation and Santonian, Ilam Formation); 6- Rotorbinella sp. nov. (Turonian for Sarvak Formation and Santonian-Campanian? for Ilam Formation). These species have never been reported before from the Sarvak and Ilam formations.

Sarah R. Stinnesbeck, Wolfgang Stinnesbeck, Eberhard Frey et al.

Schubert and colleagues have recently criticized our assessment of the mandibular ramus of a small peccary from Muknal cave in Quintana Roo, Mexico, to a new genus and species, 'Muknalia minima' Stinnesbeck et al. 2017. They considered this assignation as invalid and the unique morphologies of the taxon to be the result of breakage and human modification. We strongly disagree with this interpretation and maintain our original view of a new genus and species.

EVANGELINA E. PALÓPOLO, SOLEDAD S. BREZINA, SILVIO CASADIO et al.

C. Weismüller, J. L. Urai, M. Kettermann et al.

<p>Normal faults in basalts develop massive dilatancy in the upper few hundred meters below the Earth's surface with corresponding interactions with groundwater and lava flow. These massively dilatant faults (MDFs) are widespread in Iceland and the East African Rift, but the details of their geometry are not well documented, despite their importance for fluid flow in the subsurface, geohazard assessment and geothermal energy. We present a large set of digital elevation models (DEMs) of the surface geometries of MDFs with 5–15&thinsp;<span class="inline-formula">cm</span> resolution, acquired along the Icelandic rift zone using unmanned aerial vehicles (UAVs). Our data present a representative set of outcrops of MDFs in Iceland, formed in basaltic sequences linked to the mid-ocean ridge.</p> <p>UAVs provide a much higher resolution than aerial/satellite imagery and a much better overview than ground-based fieldwork, bridging the gap between outcrop-scale observations and remote sensing. We acquired photosets of overlapping images along about 20&thinsp;<span class="inline-formula">km</span> of MDFs and processed these using photogrammetry to create high-resolution DEMs and orthorectified images. We use this dataset to map the faults and their damage zones to measure length, opening width and vertical offset of the faults and identify surface tilt in the damage zones. Ground truthing of the data was done by field observations.</p> <p>Mapped vertical offsets show typical trends of normal fault growth by segment coalescence. However, opening widths in map view show variations at much higher frequency, caused by segmentation, collapsed relays and tilted blocks. These effects commonly cause a higher-than-expected ratio of vertical offset and opening width for a steep normal fault at depth.</p> <p>Based on field observations and the relationships of opening width and vertical offset, we define three endmember morphologies of MDFs: (i) dilatant faults with opening width and vertical offset, (ii) tilted blocks (TBs) and (iii) opening-mode (mode I) fissures. Field observation of normal faults without visible opening invariably shows that these have an opening filled with recent sediment. TB-dominated normal faults tend to have the largest ratio of opening width and vertical offset. Fissures have opening widths up to 15&thinsp;<span class="inline-formula">m</span> with throw below a 2&thinsp;<span class="inline-formula">m</span> threshold. Plotting opening width versus vertical offset shows that there is a continuous transition between the endmembers. We conclude that for these endmembers, the ratio between opening width and vertical offset <span class="inline-formula"><i>R</i></span> can be reliably used to predict fault structures at depth. However, fractures associated with MDFs belong to one larger continuum and, consequently, where different endmembers coexist, a clear identification of structures solely via the determination of <span class="inline-formula"><i>R</i></span> is impossible.</p>

R. Larson, T. Hilde

Mee-mann Chang, Desui Miao

Lucio M. Ibiricu , Matthew C. Lamanna, Rubén D.F. Martínez et al.

In dinosaurs and other archosaurs, the presence of foramina connected with internal chambers in axial and appendicular bones is regarded as a robust indicator of postcranial skeletal pneumaticity (PSP). Here we analyze PSP and its paleobiological implications in rebbachisaurid diplodocoid sauropod dinosaurs based primarily on the dorsal vertebrae of Katepensaurus goicoecheai, a rebbachisaurid from the Cenomanian–Turonian (Upper Cretaceous) Bajo Barreal Formation of Patagonia, Argentina. We document a complex of interconnected pneumatic foramina and internal chambers within the dorsal vertebral transverse processes of Katepensaurus. Collectively, these structures constitute a form of PSP that has not previously been observed in sauropods, though it is closely comparable to morphologies seen in selected birds and non-avian theropods. Parts of the skeletons of Katepensaurus and other rebbachisaurid taxa such as Amazonsaurus maranhensis and Tataouinea hannibalis exhibit an elevated degree of pneumaticity relative to the conditions in many other sauropods. We interpret this extensive PSP as an adaptation for lowering the density of the skeleton, and tentatively propose that this reduced skeletal density may also have decreased the muscle energy required to move the body and the heat generated in so doing. Given that several rebbachisaurids inhabited tropical to subtropical paleolatitudes during the extreme warmth of the mid-Cretaceous, increased PSP may have better enabled these sauropods to cope with extraordinarily high temperatures. Extensive skeletal pneumaticity may have been an important innovation in Rebbachisauridae, and perhaps also in saltasaurine titanosaurs, which evolved an even greater degree of PSP. This may in turn have contributed to the evolutionary success of rebbachisaurids, which were the only diplodocoids to survive into the Late Cretaceous.

Lawrence H. Tanner, Spencer G. Lucas

The lower Permian (Wolfcampian) Sangre de Cristo Formation of northern New Mexico consists of silty mudstones and laterally discontinuous sandstones deposited on an aggrading alluvial plain. Locally, mudstones display a variety of pedogenic features. Common mudstone fabrics vary from platy to prismatic; some beds display prominent pedogenic slickensides. Drab-colored root traces are common throughout the section, as are calcareous nodules, which vary from small bodies with diffuse boundaries to vertically stacked, discrete, cm-scale nodules (rhizocretions), and less commonly form coalescing horizons. Vertisols occur only in the lower portion of the ca. 90-m measured section. Most of the mudstone beds contain calcretes that are immature (calcic Protosols to calcic Argillisols), but the lower to middle portion of the section also contains mature calcrete horizons (argillic Calcisols and Calcisols). Intercalated micritic limestone beds with sharp contacts containing root traces, are of laterally variable thickness and grade to nodular calcretes. These are interpreted as floodplain pond carbonates that have undergone pedogenic alteration (palustrine limestones), indicating long periods of exposure under strongly seasonal climatic conditions. The isotopic composition of the pedogenic carbonate displays a substantial range of values, but most of the range of variation in isotopic composition is accounted for by isotopically heavier carbonate (both carbon and oxygen) precipitated in shallow ponds subject to intense pedogenic reworking (palustrine carbonate). During the early Permian, northern New Mexico was situated in a near equatorial position (ca. 4° N). The overall character of the paleosols suggests a persistent warm, semi-humid, seasonal climate throughout most of the interval of deposition during the Wolfcampian, but with episodically increased aridity during formation of the more mature calcretes. No long-term trend of climate change is evident in the stratigraphic section examined for this study.

W. Joyce

A. Ponomarenko, A. Prokin

Miklós Kedves

From the evolutionary point of view the most important ultrastructural characteristic features of the terrestrial microfossils are presented in this contribution. During the Mesozoic Era important innovations happened in the ultrastructure of the gymnosperm pollen grains. The earliest saccate elements represent the alveolar infratectal ultrastructure, which appeared in the Carboniferous, and remains in the present day gymnosperm species (Pinus, Picea). New events during the Mesozoic: 1. Appearance of the modern ultrastructure type in several inaperturate and monosulcate pollen grains (Araucariacites Cookson, Cycadopites (Wodehouse) Wilson and Webster). 2. Exclusively Mesozoic gymnosperm types with peculiar LM morphology and exine ultrastructure. The pollen grains of the Operculati (Circulina Malyavkina, Classopollis Pflug, Classoidites Amerom) are very isolated by their LM morphology, the wall ultrastructure is very complicated, similar to some angiosperm taxa. 3. Angiosperm-like exine ultrastructure appeared at the LM morphologically gymnosperrn pollen grains of the Spheripollenites Couper fgen. 4. The gymnospermous Eucommiidites Erdtman has some angiosperm characteristics with the granular infratectal layer. Concerning the evolution of the vegetation the appearance of the angiosperms was the most important event. Regarding the ultrastructure of the pollen grains, the most important evolutionary alterations may be followed by the alterations in the ultrastructure of the infratectal layer. In the earliest Longaxones (Lower Cretaceous) the columellar infratectal layer is characteristic, this may be followed in some Brevaxones by the granular one, during the Senonian. KEY WORDS. Palynology. Mesozoic. Ultrastructure evolution.

D. Braun, N. Levin, Deano Stynder et al.

G. A. Cooper, R. E. Grant

P. Gingerich

P. Shipman