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1
Anderson, T. F., B. N. Popp, L. Z. HO e A. C. Williams. "The carbon and oxygen isotopic records of fossils from the Lower Oxford Clay". Paleontological Society Special Publications 6 (1992): 7. http://dx.doi.org/10.1017/s2475262200005670.
Testo completoAbstract (sommario):
The excellent preservation of calcareous invertebrates and phosphatic vertebrates in the Lower Oxford Clay provides a good opportunity for paleooceanographic reconstruction based on stable isotopic abundances. We present here our initial results and interpretations on carbon and oxygen isotopic analyses on fossils of different depth habitats. Benthic fossils include epifaunal oysters and infaunal nuculacean bivalves. We also analyzed “pendant” bivalves whose depth habitat is uncertain. Fossil nekton are represented by ammonites and belemnites. Organisms that inhabited the uppermost part of the water column are represented by marine reptiles, such as icthyosaurs and plesiosaurs, and probable pelagic fish.The oxygen isotopic compositions of calcareous benthos and nekton overlap substantially (δ180 = −2 to +1 permil vs. PDB). The wide scatter in δ180 values probably reflects physiological (non-equilibrium) effects in calcification rather than paleoenvironmental variations. Mean δ180 values for oysters, pendant bivalves, and belemnites (all calcitic) and nuculacean bivalves (aragonitic) correspond to precipitation at isotopic equilibrium with non-glacial seawater at temperatures of 15°-18°. The mean isotopic paleotemperature for ammonites (aragonitic) is slightly higher (20°) but is probably not significantly different from those for other calcareous macro-invertebrates. Preliminary oxygen isotopic results on phosphate extracted from bones, teeth, and gill rays correspond to paleotemperatures of 20°–25°.Carbon isotopic results are limited to data from calcareous benthos and nekton. δ 13C values for individual taxa are quite variable (+2 to +5 permil for aragonitic fossils, 0 to +3 permil for calcitic fossils), suggesting physiological isotope effects. Nonetheless, mean δ 13C values are consistent with calcification in seawater having a carbon isotopic composition similar to that of modern average seawater. The presumably high flux of 13C-depleted CO2 into bottom waters from the diagenesis of sedimentary organic matter is not recorded in the carbon isotopic composition of benthic fossils.Thermal stratification implied by the oxygen isotopic record suggests the penetration of cool, nutrient-rich waters into the Lower Oxford Clay sea. Upward advection of deep waters together with runoff from adjacent landmasses must have provided sufficient nutrients to maintain the inferred high productivity of surface waters. The influence of productivity on the carbon isotopic composition of surface waters will be tested by the analysis of calcareous phytoplankton.
2
Bengtson, Stefan. "Early skeletal fossils". Paleontological Society Papers 10 (novembre 2004): 67–78. http://dx.doi.org/10.1017/s1089332600002345.
Testo completoAbstract (sommario):
The Precambrian-Cambrian transition saw the burgeoning of diverse skeletal organisms (“small shelly fossils”), represented in the fossil record by spicules, tubes, tests, conchs, shells, and a variety of sclerites and ossicles. Whereas calcareous biomineralization as such may have been facilitated by changes in ocean chemistry at this time, the utilization of biominerals in mineralized skeletons is a different process. The massive appearance of skeletons is most likely an epiphenomenon of the general radiation of body plans and tissues. The “choice” of biominerals (mainly calcium carbonates, calcium phosphates, and silica) may reflect the environmental conditions under which the particular skeleton first evolved.
3
Wilson, J. "Approaches to the preparation and development of calcareous fossils from calcareous matrices". Geological Curator 4, n. 7 (febbraio 1987): 447–50. http://dx.doi.org/10.55468/gc12.
Testo completo
4
Miller, Kelly B., e Sara H. Lubkin. "Calicovatellus petrodytes, a new genus and species of primitive vatelline diving beetle (Coleoptera: Dytiscidae: Hydroporinae: Vatellini) from the Miocene Barstow Formation, southern California, USA". Journal of Paleontology 75, n. 4 (luglio 2001): 890–94. http://dx.doi.org/10.1017/s0022336000016991.
Testo completoAbstract (sommario):
Relatively few fossil dytiscids have been described. This is unfortunate since fossils can provide useful phylogenetic and evolutionary information including unique character combinations not present in extant taxa and minimum ages for divergences. However, even when fossils are found, important characters are often not visible since they may be poorly preserved or obscured. The fossil insects present in calcareous nodules from the Miocene Barstow Formation of the Calico Mountains in Southern California are exceptionally well preserved (Palmer, 1957). The original organisms are replaced by silica or other minerals and when the nodules are dissolved in formic acid, the three-dimensional fossil can be retrieved from the resulting residue. These nodules have yielded a wide variety of fossils, including larvae of the dytiscid species Schistomerus californense Palmer, 1957 and numerous other terrestrial and fresh-water arthropods (Palmer, 1957). The purposes of this paper are to describe a new dytiscid genus and species from an exceptionally well-preserved specimen from the Barstow Formation and to present a hypothesis of the phylogenetic placement of the new taxon.
5
Turner, Judith. "Sponge Gemmules from Lake Sediments in the Puget Lowland, Washington". Quaternary Research 24, n. 2 (luglio 1985): 240–43. http://dx.doi.org/10.1016/0033-5894(85)90010-9.
Testo completoAbstract (sommario):
Gemmules of five species of freshwater sponge found in deposits at Cedar Mountain bog in the southeastern Puget Lowland were used to infer that during the late-glacial period the water was calcareous, was not deficient in SiO2, was aerobic, and had a pH in the range 6.6–8.5. This is consistent with plant fossil data. In view of their paleoenvironmental potential it is worth looking for gemmules when extracting other fossils from lake sediments.
6
Lorcher, Fritz, e Thomas Keller. "Preparation Techniques for Material From The Posidonienschiefer (Lias Epsilon, Upper Liassic) of Germany". Geological Curator 4, n. 3 (luglio 1985): 164–68. http://dx.doi.org/10.55468/gc749.
Testo completoAbstract (sommario):
The authors describe methods of mechanical and chemical treatment of fossils from the Posidonienschiefer (Lias epsilon, Upper Liassic, Lower Jurassic, south-western Germany). Special tools and techniques are discussed. The use of acids in the preparation of vertebrate fossils from calcareous layers gives very good results, better than any mechanical method of preparation.
7
R. Nimnu, J., G. O Aigbadon e F. Ogbikaya. "Foraminiferal biostratigrpahy of oshi-13 field, coastal and central swamp depobelt, Niger delta basin, Nigeria". International Journal of Advanced Geosciences 6, n. 1 (30 maggio 2018): 127. http://dx.doi.org/10.14419/ijag.v6i1.10907.
Testo completoAbstract (sommario):
A high resolution Foraminiferal biostratigrpahic study has been carried out using data from three wells located in the Coastal and Central Swamp depobelts of Niger Delta.The study defined six (N6-N15) Foraminiferal zones for the early to middle Miocene Niger Delta on the basis of index Foraminiferal and this was correlated to Blow, 1969 and Bergreen et al., 1995. Foraminiferal analysis shows that Oshi-13Field is very rich in calcareous and araneceous benthics, calcareous and planktic foraminiferal. The abudance of fossils and index fossils are responsible for constructing the biostratigraphic chart and hydrocarbon saturation in the field. The biostratigraphy chart constructed act as a basis in establishing the ages of sediments/ sequence in the studied field.
8
Nhung, Nguyen Thi Hong, Nguyen Thi Thuy, Nguyen Viet Hien e Nguyen Huu Manh. "Quy trình gia công và phân tích hóa thạch Tảo vôi, áp dụng cho các trầm tích ven biển tỉnh Sóc Trăng". Tạp chí Khoa học và Công nghệ biển 19, n. 4 (27 marzo 2020): 537–44. http://dx.doi.org/10.15625/1859-3097/19/4/12676.
Testo completoAbstract (sommario):
Calcareous nannofossils are very small microfossils composed of calcium carbonate. They are very good biostratigraphic markers within marine sediments by covering the Jurassic to present. The standard preparation of a sample for nannofossil analysis requires the collection of the largest quantity and the best fossils. Sample preparation accords to the following steps: i. Pounding sample; ii. Eliminating organic matter; iii. Washing sample; iv. Filter sample through the sieve; v. Eliminating clay; vi. Drying sample in an incubator; vii. Packing sample. Sample analysis accords to the following steps: i. Preparation of smear - slide; ii. Observation of morphology; iii. Determination; iv. Taking photo; v. Evaluating overall preservation and abundance of fossils; vi. Making analysis result sheet. This process is applied to study calcareous nannofossils within marine sediments in Soc Trang province. It makes much clear to understand middle Pleistocene-early Holocene ecosystem of calcareous nannofossil. In conclusion, this assemblage belongs to NN21 zone by the present of Emiliania huxleyi and Gephyrocapsa oceanica.
9
Hochuli, Peter A. "‘Organic nannofossils’: a new type of palynomorph from the Palaeogene of the North Sea". Journal of Micropalaeontology 19, n. 2 (1 dicembre 2000): 153–58. http://dx.doi.org/10.1144/jm.19.2.153.
Testo completoAbstract (sommario):
Abstract. Organic microfossils of regular dodecahedral shape are found in the Palaeogene (Lower Oligocene) of the central and northern parts of the Norwegian North Sea. The shape and structure of these fossils are very similar to coccospheres of the calcareous nannoplankton genus Braarudosphaera. The individual pentagonal plates show the same morphological features as replicas of the inner surface of pentaliths forming calcareous coccospheres. It is the first evidence that a representative of calcareous nannoplankton (Haptophyta, Coccolithophorales) is found to produce acid-resistant organic microfossils. The organic remains might have been produced by an undescribed species of the genus Braarudosphaera or represent an unknown stage in the life cycle of species which normally produce calcareous plates.
10
Onken, Beth R., e Philip W. Signor. "Lidaconus palmettoensis n. gen. and sp.: an enigmatic Early Cambrian fossil from western Nevada". Journal of Paleontology 62, n. 2 (marzo 1988): 172–80. http://dx.doi.org/10.1017/s0022336000029826.
Testo completoAbstract (sommario):
Lidaconus palmettoensis n. gen. and sp. is a recently discovered fossil from the Lower Cambrian Harkless Formation (Bonnia–Olenellus Zone) in Esmeralda County, Nevada. The conoidal fossils were originally calcareous and have been replaced by silica. The cones are distinctive in their consistent morphology, the presence of weak annulations, and the lack of any internal structures such as septa, tabulae, or dissepiments. Because of the paucity of diagnostic characters due to the simple morphology and the lack of original microstructure, taxonomic affinities are uncertain.
11
Bromley, R. G., e J. Martinell. "Centrichnus, new ichnogenus for centrically pattemed attachment scars on skeletal substrates". Bulletin of the Geological Society of Denmark 38 (19 febbraio 1991): 243–52. http://dx.doi.org/10.37570/bgsd-1990-38-21.
Testo completoAbstract (sommario):
Two characteristic and common trace fossils, lightly etched into the surfaces of skeletal substrates in marine environments, are named Centrichnus eccentricus igen. et isp. nov., and C. concentricus isp. nov. respectively. Tue first is new, not having been described in recent or fossil material before. It corresponds to the attachment scars produced by anomiid bivalves where they anchor their unique calcified byssus to the substrate. C. concentricus, on the other hand, is well known but hitherto has not been named. It corresponds to the etching scars produced beneath verrucid cirripedes on calcareous substrates.
12
Barros, Olga Alcântara, João Hermínio Silva, Gilberto Dantas Saraiva, Bartolomeu Cruz Viana, Alexandre Rocha Paschoal, Paulo Tarso Cavalcante Freire, Naiara Cipriano Oliveira, Amauri Jardim Paula e Maria Somália Viana. "Physicochemical investigation of shrimp fossils from the Romualdo and Ipubi formations (Araripe Basin)". PeerJ 7 (14 febbraio 2019): e6323. http://dx.doi.org/10.7717/peerj.6323.
Testo completoAbstract (sommario):
The Ipubi and Romualdo Formations are Cretaceous units of the Araripe Basin (Santana Group). The first and most ancient was deposited in a lake environment, and some fossils were preserved in shales deposited under blackish conditions. The second was deposited in a marine environment, preserving a rich paleontological content in calcareous concretions. Considering that these two environments preserved their fossils under different processes, in this work we investigated the chemical composition of two fossilized specimens, one from each of the studied stratigraphic units, and compared them using vibrational spectroscopy techniques (Raman and IR), X-ray diffraction and large-field energy-dispersive X-ray spectroscopy (EDS) mappings. Calcite was observed as the dominant phase and carbon was observed in the fossils as a byproduct of the decomposition. The preservation of hydroxide calcium phosphate (Ca10(PO4)6(OH)2, hydroxyapatite) was observed in both fossils. In addition, it was observed that there was a smaller amount of pyrite (pyritization) in the Romualdo Formation sample than in the Ipubi one. Large-field EDS measurements showed the major presence of the chemical elements calcium, oxygen, iron, aluminum and fluoride in the Ipubi fossil, indicating a greater influence of inorganic processes in its fossilization. Our results also suggest that the Romualdo Formation fossilization process involved the substitution of the hydroxyl group by fluorine, providing durability to the fossils.
13
Padilla, C. B., M. E. Páramo, L. F. Noè, M. Gómez Pérez e M. Luz Parra. "Acid Preparation of Large Vertebrate Specimens". Geological Curator 9, n. 3 (settembre 2010): 213–20. http://dx.doi.org/10.55468/gc231.
Testo completoAbstract (sommario):
Acid preparation of large vertebrate fossils poses special problems for the preparator. The Fundaci�n Colombiana de Geobiolog�a has prepared a number of large vertebrates (marine reptiles from the Cretaceous of Colombia, South America) using acid to remove calcareous matrix. A combination of factors, including: specimen size: choice of acid; number and length of acid baths; ventilation needs; area of matrix and fossil exposed; matrix homogeneity; number of acid resistant protective coats applied; management of voids; and acid consumption are shown to be important. By varying these parameters, exceptional preparation of specimens ready for detailed research and study can result.
14
Jud, Nathan A., e Jeremy I. Dunham. "Fossil woods from the Cenozoic of Panama (Azuero Peninsula) reveal an ancient neotropical rainforest". IAWA Journal 38, n. 3 (7 novembre 2017): 366—S2. http://dx.doi.org/10.1163/22941932-20170176.
Testo completoAbstract (sommario):
Silicified woods from near the town of Ocú on the Azuero Peninsula, Panama were first reported by Stern and Eyde in 1963; however, the significance of these fossils has been largely overlooked. Well-characterized fossil floras from Central America can be used to test hypotheses related to the historical biogeography and paleoclimate of the Neotropics. We describe 10 new wood types and one palm based on 22 samples from Oligo-Miocene deposits. Affinities at the family/order level include Fabaceae, Lauraceae, Moraceae, Sapotaceae, Euphorbiaceae, Arecaceae, Sapindales, Ericales, and Humiriaceae. The fossil woods are fragmentary and have not been found in-place, but the size and angularity of the specimens suggests minimal transport from the site of growth. We compared these woods with calcareous woods from the Lower Miocene Cucaracha Formation and silicified woods from the upper Miocene Alajuela Formation using Rare Earth Element (REE) analysis to test the hypothesis that the Ocú woods were preserved under uniform conditions and not reworked. Although the results were ambiguous with respect to the original hypothesis, we note that the REE concentrations in silicified woods are much lower than in calcareous woods. We used comparative analysis of wood anatomical features to draw conclusions about the paleoclimate from the fossil flora. All the dicot woods are diffuse porous and none have distinct growth rings; some have very wide vessels at low frequencies. These features are typical of canopy trees in tropical lowland forests. Nonmetric multidimensional scaling of wood anatomical characters from a variety of communities and ecological categories showed that the anatomy of the Ocú woods is most similar to that found in tropical rainforests. Based on the combination of taxonomic identity and functional anatomy, we interpret these fossils as evidence for humid to perhumid megathermal climate in Panama during the late Paleogene-early Neogene.
15
Noè, L. F., M. Gómez-Pérez e S. Padilla-Bernal. "Comparing sulphamic acid to acetic and formic acids for the preparation of large mesozoic marine reptile fossils, and a method for monitoring residual acid and salt removal following acid preparation". Geological Curator 11, n. 1 (giugno 2019): 81–92. http://dx.doi.org/10.55468/gc411.
Testo completoAbstract (sommario):
Chemical preparation is an important technique in palaeontology that uses a dilute aqueous acid solution to remove calcareous matrix from fossils, but which leads to the evolution of salts as a by-product. Acid preparation is usually undertaken using formic and acetic acids, whereas sulphamic acid has only rarely been considered. Sulphamic acid is a strong acid, with many industrial uses, but which has fewer health and safety concerns, and produces fewer irritant fumes, than formic or acetic acids. Three comparative procedures were undertaken to understand the action of sulphamic acid in relation to formic and acetic acids, using calcareous matrix from Colombian (South American) large Mesozoic marine reptiles. The results of these procedures indicate sulphamic acid acts in a comparable manner to formic acid, and more rapidly than acetic acid, in terms of rate of matrix removal. Afourth procedure investigated the removal of acid and salt residues following sulphamic acid preparation of a Colombian large Mesozoic marine reptile fossil, a process essential for the long-term survival of any acid prepared specimen. The fossil was immersed in type 1 deionized water, and increasing electrical conductivity was used as a proxy for ionic leaching. The results imply the preparators 'rule of thumb' of soaking a specimen in water for three times the length of time spent in the acid solution, is inadequate to ensure satisfactory removal of acid and salt residues. Although tested on a specimen prepared using sulphamic acid, the technique for post-preparation ion removal is equally be applicable to all fossils prepared using sulphamic, formic or acetic acids in aqueous solution.
16
Zorn, Marilyn E., Michael W. Caldwell e Mark VH Wilson. "Lithological analysis of the Lower Devonian vertebrate-bearing beds at the MOTH locality, N.W.T., Canada: insights to taphonomy and depositional setting". Canadian Journal of Earth Sciences 42, n. 5 (1 maggio 2005): 763–75. http://dx.doi.org/10.1139/e05-015.
Testo completoAbstract (sommario):
Sedimentary and faunal characteristics of the Lower Devonian Man On The Hill (MOTH) vertebrate-bearing succession, Mackenzie Mountains, Northwest Territories, Canada provide insights to the paleoenvironmental conditions. Based on sedimentological and petrographic analyses of a 6-m vertical section of the vertebrate-bearing strata, three depositional scenarios for the MOTH locality are proposed, the favoured interpretation being that the vertebrate-bearing interval was deposited on the outer margin of a carbonate platform within an intra-shelf topographic low below storm-wave base. This interpretation is supported by the presence of fine, alternating laminae of light grey argillaceous limestone, or calcareous shale, and dark grey silt to sand-rich calcareous shale, as observed in thin section, and the characterization of the lithology for the vertebrate-bearing strata as an interlaminated argillaceous limestone and calcareous shale. An abundant, low-diversity association of cryptic trace fossils, previously unrecognized at MOTH, is described. These trace fossils and the presence of pyrite suggest that the intra-shelf topographic sag at MOTH had restricted circulation and was generally hypoxic. Based on the instability of such a restricted environment, a cause of death for the cyathaspids Dinaspidella and Nahanniaspis is unclear. However, turbidite deposition and seasonal turnover can be eliminated as possible causes of death, as vertebrates were not located frequently enough within light or dark grey layers and minimal signs of skeletal abrasion or fracturing were observed in Dinaspidella and Nahanniaspis. The high preservation potential of the fossils at MOTH likely was enhanced by the hypoxic nature of the bottom waters within the intra-shelf topographic low below storm-wave base.
17
Smelror, Morten, e Dirk Knaust. "Trace fossils and palynomorphs in Holocene calcareous concretions from Lake Selbusjøen, Mid-Norway: Post-glacial environmental records". Holocene 31, n. 5 (17 gennaio 2021): 732–45. http://dx.doi.org/10.1177/0959683620988046.
Testo completoAbstract (sommario):
Trace fossils and palynomorphs are recorded for the first time in Holocene calcareous concretions from Lake Selbusjøen, Central Norway. The described trace fossils can be assigned to the Mermia ichnofacies, characterizing lake deposits with good oxygenation and low depositional energy. The predominance of simple grazing trails and shallow burrows (e.g. Cochlichnus, Helminthoidichnites and Treptichnus) in silty and sandy concretions possibly represent relatively low-energy sublittoral parts of the lake, while the occurrence of Vagorichnus and Arenicolites in sandy substrate points to littoral and shallow sublittoral areas with moderate depositional energy. The trace fossils and palynomorph assemblages from Lake Selbusjøen appear to relate to periods of climatic warming during Pre-Boreal times, and possibly also Atlantic times.
18
Dawson, William C. "Phylloid algal microstructures enhanced by epifluorescence petrography". Journal of Paleontology 66, n. 3 (maggio 1992): 523–25. http://dx.doi.org/10.1017/s0022336000034053.
Testo completoAbstract (sommario):
“Phylloid algae” (Pray and Wray, 1963, p. 209) are problematical fossils that occur profusely in Pennsylvanian carbonate microfacies in the United States (Wray, 1968) and many other parts of the world (Mamet, 1991). Taxonomic affinities of most phylloid alga are uncertain. The questionable affinities of phylloid algae and related paleoecologic problems have been summarized by Riding (1977), Wray (1979), and James et al. (1988) and will not, therefore, be repeated here. Our ability to establish probable taxonomic affinities of fossil calcareous algae is dependent largely upon the recognition of their internal microstructures. Because phylloid algae are very susceptible to dissolution and neomorphism, their original internal microstructures are rarely well preserved.
19
Al-Zubaidi, Alaa, e Omar Al-Badrani. "The Calcareous Nannofossils Biostratigraphy of the Cretaceous Red Bed the in Shiranish Formation, Hiran in Erbil Governorate and Smaqoli Area in Sulaimaniya Governorate, Northern Iraq". Iraqi Geological Journal 56, n. 2A (31 luglio 2023): 198–210. http://dx.doi.org/10.46717/igj.56.2a.15ms-2023-7-24.
Testo completoAbstract (sommario):
On the basis of the stratigraphic ranges of the reported calcareous nannfossils for several species, two sections of the Shiranish Formation from the Hiran in the Erbil Governorate and the Smaqoli area in Sulaimaniya Governorate, Northern Iraq, are analyzed. Four biozones are visible in the examined region, grouped as follows from oldest to youngest: Uniplanarius gothicus Interval zone; Tranolithus phacelosus Interval zone; Rienhardtites lives Interval zone; Micula murus Interval zone. The relationship between these biozones and those of other calcareous nannofossil biozones from local and regional sections allows scientists to determine that these fossils are from the Late Campanian to Early Maastrichtian period.
20
Chesnut, Donald R., e Ernie R. Slucher. "Color-banded gastropods from the Kendrick Shale Member (Middle Pennsylvanian, Westphalian B) of eastern Kentucky". Journal of Paleontology 64, n. 3 (maggio 1990): 475–77. http://dx.doi.org/10.1017/s0022336000018722.
Testo completoAbstract (sommario):
Very well preserved gastropods, with preserved color banding, are common in a newly discovered site in the Eastern Kentucky Coal Field. The fossils occur in calcareous silty shales of the Middle Pennsylvanian Kendrick Shale Member of the Breathitt Formation. Three genera of gastropods, Bellerophon, Straparollus, and Ianthanopsis, have been found with preserved color patterns.
21
Lukeneder, Petra, e Alexander Lukeneder. "Mineralized belemnoid cephalic cartilage from the late Triassic Polzberg Konservat-Lagerstätte (Austria)". PLOS ONE 17, n. 4 (20 aprile 2022): e0264595. http://dx.doi.org/10.1371/journal.pone.0264595.
Testo completoAbstract (sommario):
Although hyaline cartilage is widely distributed in various invertebrate groups such as sabellid polychaetes, molluscs (cephalopods, gastropods) and a chelicerate arthropod group (horseshoe crabs), the enigmatic relationship and distribution of cartilage in taxonomic groups remains to be explained. It can be interpreted as a convergent trait in animal evolution and thus does not seem to be a vertebrate invention. Due to the poor fossil record of cartilaginous structures, occurrences of mineralized fossil cartilages are important for evolutionary biology and paleontology. Although the biochemical composition of recent cephalopod cartilage differs from vertebrate cartilage, histologically the cartilages of these animal groups resemble one another remarkably. In this study we present fossil material from the late Triassic Polzberg Konservat-Lagerstätte near Lunz am See (Lower Austria, Northern Calcareous Alps). A rich Carnian fauna is preserved here, whereby a morphogroup (often associated with belemnoid remains) of black, amorphous appearing fossils still remained undetermined. These multi-elemental, symmetrical fossils show remarkable similarities to recent cartilage. We examined the conspicuous micro- and ultrastructure of these enigmatic fossils by thin-sectioning and Scanning Electron Microscopy (SEM). The geochemical composition analyzed by Microprobe and Energy Dispersive X-ray Spectroscopy (SEM-EDX) revealed carbonization as the taphonomic pathway for this fossil group. Mineralization of soft tissues permits the 3D preservation of otherwise degraded soft tissues such as cartilage. We examined eighty-one specimens from the Polzberg locality and seven specimens from Cave del Predil (formerly Raibl, Julian Alps, Italy). The study included morphological examinations of these multi-elemental fossils and a focus on noticeable structures like grooves and ridges. The detected grooves are interpreted to be muscular attachment areas, and the preserved branched system of canaliculi is comparable to a channel system that is also present in recent coleoid cartilage. The new findings on these long-known enigmatic structures strongly point to the preservation of cephalic cartilage belonging to the belemnoid Phragmoteuthis bisinuata and its homologization to the cephalic cartilage of modern coleoids.
22
Haq, Izhar Ul, Eswaran Padmanabhan e Omer Iqbal. "Depositional Heterogeneities and Brittleness of Mudstone Lithofacies in the Marcellus Subgroup, Appalachian Basin, New York, U.S.A." Energies 14, n. 20 (14 ottobre 2021): 6620. http://dx.doi.org/10.3390/en14206620.
Testo completoAbstract (sommario):
Organic-rich rocks of the Marcellus subgroup in the study area consist of a diverse suite of mudstone lithofacies that were deposited in distinct facies belts. Lithofacies in the succession range in composition from argillaceous to siliceous, calcareous, and carbonaceous mudstone. Heterogeneities in the succession occurs in the form of varying mineralogical composition, slightly bioturbated to highly bioturbated chaotic matrix, organic-rich and organic-lean laminae, scattered fossil shells in the matrix, and fossils acting as lamination planes. Lithofacies were deposited in three facies belts from the proximal to the distal zone of the depositional system. Bedded siliceous mudstone (BSM) facies occur in the proximal facies belt and consists of a high quartz content in addition to clay minerals and pyrite. In the medial part of the facies belt lies the laminated argillaceous mudstone (LAM), bedded calcareous mudstone (BCaM), and bedded carbonaceous mudstone (BCM). The size of detrital mineral grains in the lithofacies of the medial facies belt is larger than bedded argillaceous mudstone (BAM) of the distal facies belt, characterized by clay-rich matrix with occasional fossil shells and horizontally aligned fossils. Two types of horizontal traces and one type of fecal string characterize the proximal mud-stone facies, whereas only single horizontal trace fossil is found in the mudstones of the medial and distal facies belt. Parallel alignment of fossil shells and fossil lags in lithofacies indicate that bed-load transport was active periodically from the proximal source of the depositional system. Bioturbation has heavily affected all of the lithofacies and presence of mottled burrows as well as Devonian fauna indicate that oxic to dysoxic conditions prevailed during deposition. The deposition of this organic-rich mudstone succession through dynamic processes in an overall oxic to dysoxic environment is different from conventional anoxic depositional models interpreted for most of the organic rich black shales worldwide. Total organic content (TOC) varies from top to bottom in the succession and is highest in BCM facies. The brittleness index, calculated on the basis of mineralogy, allowed classification of the lithofacies into three distinct zones, i.e., a brittle zone, a less brittle zone, and a ductile zone with a general proximal to distal decrease in the brittle behavior due to a decrease in the size of the sediments.
23
Scourse, J. "Trace fossils of talitrid sandhoppers in interglacial littoral calcareous sandstones, Cornwall, U.K." Quaternary Science Reviews 15, n. 5-6 (1996): 607–15. http://dx.doi.org/10.1016/0277-3791(96)00018-2.
Testo completo
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Narbonne, Guy M., Paul M. Myrow, Ed Landing e Michael M. Anderson. "A candidate stratotype for the Precambrian–Cambrian boundary, Fortune Head, Burin Peninsula, southeastern Newfoundland". Canadian Journal of Earth Sciences 24, n. 7 (1 luglio 1987): 1277–93. http://dx.doi.org/10.1139/e87-124.
Testo completoAbstract (sommario):
The Burin Peninsula exhibits an exceptionally thick and essentially continuous succession of marine strata through the Precambrian–Cambrian transition. Fossils are abundant and include trace fossils, small shelly fossils, vendotaenid algae, soft-bodied megafossils, and microfossils. The Burin Peninsula is readily accessible and has long been considered a potential area for a Precambrian–Cambrian boundary stratotype.A continuous section through the upper part of member 1 and all of member 2 of the Chapel Island Formation is exposed at Fortune Head, and this section is herein proposed as a global stratotype for the Precambrian–Cambrian boundary. The boundary horizon is located 2.4 m above the base of member 2 of the Chapel Island Formation. This horizon marks the base of the basal Cambrian Phycodes pedum (ichnofossil) Zone and immediately overlies the top of the Late Precambrian Harlaniella podolica (ichnofossil) Zone. Shelly fossils (sabelliditids) first appear a few metres below the proposed boundary. Soft-bodied megafossils, carbonaceous impressions of vendotaenid algae, and organic-walled microfossils occur both below and above this boundary and enhance global correlation with this section.Fossils of the Rusophycus avalonensis (ichnofossil) Zone first appear midway through member 2 (approximately 135 m above the proposed boundary) and occur commonly throughout the upper part of the Chapel Island Formation and the overlying Random Formation. Calcareous small shelly fossils (?Circotheca sp.) appear near the top of member 2 (approximately 400 m above the proposed boundary), and a more diverse Aldanella attleborensis small shelly fossil assemblage characterizes the uppermost strata of member 3 and all of member 4 of the Chapel Island Formation (approximately 550–650 m above the proposed boundary). The lowest trilobites, representatives of the Callavia broeggeri Zone, first appear more than 1000 m above the proposed Precambrian–Cambrian boundary.
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Lemoine, Marcel. "Schistes lustrés from Corsica to Hungary : back to the original sediments and tentative dating of partly azoic metasediments". Bulletin de la Société Géologique de France 174, n. 3 (1 maggio 2003): 197–209. http://dx.doi.org/10.2113/174.3.197.
Testo completoAbstract (sommario):
Abstract The Alpine and Corsican Schistes lustrés (SL) are nearly azoic Jurassic-Cretaceous metasediments often associated with ophiolites. They are derived from both the vanished Valais (N-Penninic) and Piemont-Ligurian (S-Penninic) oceans and from their continental margins. Their age is generally poorly known. Because of fossils discovered by Alb. Heim and by S. Franchi at the beginning of the 20th century, they were believed for a long time to be mostly Liassic in age. We know now that the major part of the SL is Cretaceous. Deep-sea sediments, and particularly the SL, are made up of a hemipelagic-pelagic background (HPB) associated with detrital components of local or distant origin. The nature of the HPB, mostly conditioned by Tethyan and worldwide events, is of great help as an at least rough stratigraphic marker ; in contrast, detrital material is not a reliable marker because it may occur at different times in different places. The HPB exhibits several successive, 10 to 40 m.y. long episodes which are either predominantly argillaceous (A) or calcareous (C). During the deposition of the Juras-sic-Cretaceous SL, seven episodes can be distinguished : C1, calcareous Liassic ; A1, marly Upper Liassic ; C2, calcareous latest Liassic and early Dogger ; A2, shaly or radiolaritic late Dogger-early Malm ; C3, calcareous late Malm ; A3 shaly or marly early Cretaceous ; C4 calcareous late Cretaceous. They can be recognized, each one by its prevailing lithology, and all together by their succession in order from C1 to C4. Nearly all of these subdivisions are here and there dated by rare fossils, which allow for a rough dating of the numerous azoic SL series. As they exhibit very different lithologies, from pelagic calcareous oozes to Black Shales and various kinds of flysch and other mass flow deposits, the SL cannot be considered as a specific, well-defined facies : they are not characteristic for a particular stage of the geodynamic evolution of the Alps. Finally, a possible influence of worldwide events is suggested. First, the role of the depth of the CCD, governed by early late Jurassic and early late Cretaceous biotic recoveries. Secondly, the correlation with first order eustatic events : transgressions on platforms seem to be roughly coeval with A episodes in the deep sea, regressions with C episodes.
26
Vaziri, Seyed Hamid, e Marc Laflamme. "Lithostratigraphy and sedimentary environment of the Precambrian Kushk Series of central Iran". Canadian Journal of Earth Sciences 55, n. 11 (novembre 2018): 1284–96. http://dx.doi.org/10.1139/cjes-2017-0234.
Testo completoAbstract (sommario):
The Kushk Series is a distinctive late Ediacaran succession occurring in the Bafq and Behabad regions of central Iran that has yielded an extensive community of diverse Ediacara biota, including several Precambrian (Chuaria) and Ediacaran (Cloudina, Corumbella) index fossils. The Kushk Series reaches a thickness of up to 518 m and consists of shallow to deep subtidal deposits along a homoclinal carbonate ramp during a transgression–regression cycle. These deposits accumulated as part of an extensional rift basin complex resulting from the opening of the Proto–Paleotethys Ocean in northeastern Gondwana. Latest Ediacaran fossils occur in the deep-water calcareous marine shales and represent a thriving community at the dawn of animal life.
27
Mustoe, George E., e Graham Beard. "Calcite-Mineralized Fossil Wood from Vancouver Island, British Columbia, Canada". Geosciences 11, n. 2 (20 gennaio 2021): 38. http://dx.doi.org/10.3390/geosciences11020038.
Testo completoAbstract (sommario):
Calcite-mineralized wood occurs in marine sedimentary rocks on Vancouver Island, British Columbia at sites that range in age from Early Cretaceous to Paleocene. These fossil woods commonly have excellent anatomical preservation that resulted from a permineralization process where calcite infiltrated buried wood under relatively gentle geochemical conditions. Wood specimens typically occur in calcareous concretions in feldspathic clastic sediment. Other concretions in the same outcrops that contain abundant mollusk and crustacea fossils are evidence that plant remains were fluvially transported into a marine basin. Fossiliferous concretions commonly show zoning, comprising an inner region of progressive precipitation where calcite cement developed as a concentric halo around the organic nucleus. An outer zone was produced by pervasive cementation, which was produced when calcite was simultaneously precipitated in pore spaces over the entire zone.
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Hornung, Thomas, Ilja Kogan, Gero Moosleitner, Gerhard Wolf e Joop van der Wielen. "The Norian fish deposits of Wiestal („Seefeld Member“, Northern Calcareous Alps, Salzburg, Austria) – taxonomy and palaeoenvironmental implications". Austrian Journal of Earth Sciences 112, n. 2 (1 gennaio 2019): 125–65. http://dx.doi.org/10.17738/ajes.2019.0008.
Testo completoAbstract (sommario):
AbstractThe Alaunian Seefeld Member of the Upper Triassic, a dark grey laminated and bituminous dolomitic limestone succession outcropping near the Wiestal-reservoir lake northeast of Hallein (Salzburg, Austria) is known for its extremely rich ‘ganoid’ fish fauna since more than a century. A privately initiated excavation that took place from 2012 to 2014 yielded far more than a thousand well-preserved fish fossils recovered largely from five mm-thin fossil horizons. The actinopterygian assemblage is dominated by several growth stages of the highly variable ginglymodian Paralepidotus ornatus, allowing for a documentation of ontogenetic transformations in cranial and postcranial morphology, dentition and squamation patterns, associated with habitat and dietary shifts. Small-sized swarm-fishes such as the macrosemiid Legnonotus and the teleost Pholidophorus are rather common members of the assemblage, while the occurrence of the ginglymodian Semiolepis, the dapediid Dandya, the dwarfish pycnodont Eomesodon and the large predatory ‘palaeopterygian’ Saurichthys is restricted to rare individuals. A single scale of a large-sized coelacanth, a well-preserved, small lobster-like decapod, plant remains and coaly gagate derived from disarticulated driftwood belong to rare associated finds. Both the perfect preservation of all fossils and the bituminous laminated dolomitic limestones barren of microfossils argue for a deposition under anoxic conditions, most probably due to salinity stratification. The occurrence of complete swarms, partly showing isoorientation of fish carcasses in distinct layers, speaks in favour of recurrent and rapid mortality events triggered by upwelling anoxic bottom water, most likely released by severe tropical storms.
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Sebe, Krisztina, Gyula Konrád e Orsolya Sztanó. "An exceptional surface occurrence: the middle to upper Miocene succession of Pécs-Danitzpuszta (SW Hungary)". Földtani Közlöny 151, n. 3 (4 dicembre 2021): 235–52. http://dx.doi.org/10.23928/foldt.kozl.2021.151.3.235.
Testo completoAbstract (sommario):
The Pécs-Danitzpuszta sand pit is the most important outcrop of the oldest Pannonian (upper Miocene, Tortonian) deposits in southern Hungary. A trench excavated in 2018 exposed Lake Pannon deposits and underlying Paratethys strata down to the upper Badenian (Serravallian), and together with the sand pit they make up a continuous sedimentary succession with a true thickness of ~220 metres. Due to tectonic deformation, middle Miocene deposits and carbonates in the lowermost Pannonian are overturned. Layers become vertical close to the marl-sand boundary, then the dip changes to normal, with continuously decreasing dip angles. The exposed succession starts with 5 m of upper Badenian (13.8-12.6 Ma old) calcareous marls and sandy limestones with sublittoral, then littoral molluscs, which were deposited in the normal salinity seawaters of the Central Paratethys. The overlying 8 m of sand, silt, sandy breccia and conglomerate are fossil-free,; only the lowermost silt layer contains reworked Badenian microfauna. This unit probably accumulated from gravity-driven flows in a fan-like, probably terrestrial depositional setting. The next 7.5 m of frequently alternating thin-bedded limestones, marls and clays with sublittoral biota represent rapid transgression. Foraminifers, ostracods, molluscs and calcareous nannoplankton indicate late Sarmatian, then Pannonian age for this interval. However, the locations of the boundaries indicated by the various groups are not are not consistent, making the position of the Sarmatian/Pannonian boundary uncertain. The Sarmatian beds with marine fossils still accumulated in the Paratethys, between ~12.1–11.6 Ma, under varying salinities due among others to temporary freshwater input. The Pannonian strata already represent sediments of the brackish Lake Pannon. Above these beds, uniform calcareous marl becomes dominant with some clay layers and graded or structureless conglomerate to sandstone interbeds. The deposition of the overall 64- m- thick Pannonian calcareous marl section took place in the open, probably few -hundred -metres -deep water of the lake between ~11.62 and 10.5–10.2 Ma. It may represent a rare, well-exposed surface occurrence of the Endrőd Formation which is known from thousands of wells in the Pannonian Basin. Above this section, a 6-7 -m- thick transitional interval of silty marls and sands is followed by ~140 m of limonitic, pebbly sands. They have poor to moderate sorting and rounding, metre -thick beds with transitional boundaries and abundant fossils and clasts reworked from older Miocene units. Their accumulation took place between 10.2-10.5 and 9.6 Ma by gravity flows connected to deep-water portions of fan deltas.
30
Tweet, Justin, Karen Chin e A. A. Ekdale. "Trace fossils of possible parasites inside the gut contents of a hadrosaurid dinosaur, Upper Cretaceous Judith River Formation, Montana". Journal of Paleontology 90, n. 2 (marzo 2016): 279–87. http://dx.doi.org/10.1017/jpa.2016.43.
Testo completoAbstract (sommario):
AbstractTiny sinuous trace fossils have been found within probable gut contents of an exceptionally preserved specimen of a hadrosaurid dinosaur,Brachylophosaurus canadensis, from the Judith River Formation of Montana. Approximately 280 examples of the trace fossils were observed in 19 samples of gut region material. The tubular structures typically are about 0.3 mm across. Many have thin calcareous linings or layers, and some exhibit fine surficial striae. At least two dozen of these trace fossils share walls with adjacent tubular traces, and this association can extend for several millimeters. While the trace fossils share some characteristics with fine rhizoliths, these features are most consistent with tiny burrows, or possibly body impressions, of worms (vermiform organisms) of uncertain biologic affinity. Such trace fossils have not been reported previously, and herein described asParvitubulites striatusn. gen. n. sp. Either autochthonous (parasites) or allochthonous (scavengers) worms may have created the trace fossils, but taphonomic factors suggest that autochthonous burrowers are more likely. Several lines of evidence, such as constant diameters and matching directional changes, suggest that the paired trace fossils were made by two individuals moving at the same time, which implies sustained intraspecific contact.Parvitubulites striatusprovides a rare record of interactions between terrestrial, meiofaunal-sized, soft-bodied invertebrates and a dinosaur carcass. The evidence that the worms may have parasitized a living hadrosaur and subsequently left traces of intraspecific behavior between individual worms adds unique information to our understanding of Mesozoic trophic interactions.
31
Shrestha, Amit, Govind Joshi, Lalu Prasad Paudel, Soma Nath Sapkota e Rafael Almeida. "Geology of the area between Bardibas and Sindhuli Madi, Sub-Himalaya, Central Nepal". Journal of Nepal Geological Society 58 (25 giugno 2019): 131–38. http://dx.doi.org/10.3126/jngs.v58i0.24597.
Testo completoAbstract (sommario):
The Siwalik Group (Sub-Himalaya) is the east-west extending youngest mountain belt formed by the sediments derived from the rising Himalaya on the north. The Siwalik Group is separated from the Lesser Himalaya to the north by the Main Boundary Thrust (MBT), and the Indo-Gangetic Plain to the south by the Main Frontal Thrust (MFT). The study was carried out mainly along the Ratu Nadi, Kamala Nadi river sections and was lithostratigraphically divided into the Lower Siwalik, Middle Siwalik, and Upper Siwalik, from the bottom to the top section, respectively. The Lower Siwalik is composed of fine-grained greenish grey calcareous sandstone (subarkose and lithic arenite), variegated mudstone, and calcareous siltstone. The Lower Siwalik is exposed due to the Marine Khola Thrust in the Gadyauli Khola, and sandstone there is more indurated and non-calcareous. The Middle Siwalik is mainly comprised of the medium- to coarse-grained salt-and-pepper sandstone (arkose and subarkose) with large cross lamination, calcareous sand lenses, convolute bedding, dark grey siltstone and mudstone. Plant fossils are also present in the finely laminated clay bed of the Middle Siwalik along the Ratu Nadi section. The Upper Siwalik comprises of mud- to sand-supported pebble to cobble conglomerates.
32
Ruebsam, Wolfgang, Emanuela Mattioli e Lorenz Schwark. "Molecular fossils and calcareous nannofossils reveal recurrent phytoplanktonic events in the early Toarcian". Global and Planetary Change 212 (maggio 2022): 103812. http://dx.doi.org/10.1016/j.gloplacha.2022.103812.
Testo completo
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Upadhyay, Rajeev, Rakesh Chandra, Hakim Rai, Neerja Jha, Shaila Chandra, R. K. Kar e Anshu K. Sinha. "First find of the Early Permian Lower Gondwana plant remains and palynomorphs from the Chhongtash Formation (Upper Shyok valley), eastern Karakoram, India". Journal of Palaeosciences 48, n. (1-3) (31 dicembre 1999): 7–18. http://dx.doi.org/10.54991/jop.1999.1286.
Testo completoAbstract (sommario):
A sedimentary sequence mainly consists of black shale, siltstone, calcareous sandstone and dark argillaceous limestone overlying pillow lava and thinly bedded limestone of the Chhongtash Formation near Chhongtash locality (Upper Shyok valley, eastern Karakoram, India) contains abundant, but poorly preserved plant fossils and palynomorphs probably referable to the Early Permian or Late Asselian (~275 Ma) interval. The plant fossils and associated palynological assemblages of eastern Karakoram show a marked similarity to the marine Lower Gondwana assemblages of the Salt Range and Talchir-Karharbari assemblages of Central India. Based on the present discovery it is suggested that, before the accretion of Cimmerian microplates to the Eurasian continent, the Karakoram microplate in its incipient state was not far from the Salt Range and located along the northern margin of the Indian subcontinent as Peri-Gondwanan microplate.
34
Tanabe, Kazushige, Pat Trask, Rick Ross e Yoshinori Hikida. "Late Cretaceous octobrachiate coleoid lower jaws from the north Pacific regions". Journal of Paleontology 82, n. 2 (marzo 2008): 398–408. http://dx.doi.org/10.1666/07-029.1.
Testo completoAbstract (sommario):
Eight well-preserved cephalopod jaw fossils were discovered from the Upper Cretaceous (Santonian and Campanian) deposits of Vancouver Island, Canada, and Hokkaido, Japan. They occur individually in calcareous concretions and retain their three-dimensional architecture. Seven of them consist of a widely open outer lamella and a posteriorly projected inner lamella with a pointed rostrum. Both lamellae are made of fluorapatite, which may represent diagenetically altered chitin, and lack a calcareous element. Based on these diagnostic features, the seven jaw fossils are identified as lower jaws of the Coleoidea. Comparison with the lower jaws of modern coleoids allows us to distinguish the following new genera and species among them;Nanaimoteuthis jeletzkyiof the Order Vampyromorphida, andPaleocirroteuthis haggartiandP. pacificaof the Order Cirroctopodida. The lower jaws of these new taxa are clearly distinguished by having a much less projected inner lamella from those of modern and extinct species of the Superorder Decabrachia and the Order Octopodida. The maximum lengths of their outer lamellae (35.0-67.1 mm) are much larger than those of most modern vampyromorph and cirroctopodid species, indicating the large body size and weight of their owners. One of the other three lower jaws examined, characterized by a posteriorly extended outer lamella, may be assigned to the Octopodida. This study clearly demonstrates that large octobrachiate coleoids existed in the Late Cretaceous North Pacific.
35
Mindell, Randal A., Ruth A. Stockey e Graham Beard. "Cascadiacarpa exilis sp. nov.: new fruits of Fagaceae from the Eocene of British Columbia". Botany 92, n. 5 (maggio 2014): 377–87. http://dx.doi.org/10.1139/cjb-2013-0247.
Testo completoAbstract (sommario):
More than 800 permineralized fagaceous fruits have been studied from the Eocene Appian Way locality of Vancouver Island, British Columbia. These cupulate nuts are the most common fruits preserved at the locality. They occur in calcareous concretions and were studied using the cellulose acetate peel technique. Cupules are borne on a spiny stalk and are broadly ovate in both longitudinal and transverse section. Cupules are evalvate and have both branching and simple spines. A single, ovoid, sclerotic nut is enclosed entirely by the cupule, except at the apex, where a stylar protrusion is free from any surrounding tissues. The nut is bilocular with a glabrous endocarp lining. At maturity, a single seed occupies the locular cavity. The embryo is straight and no endosperm is evident. The single-fruited, spiny cupule is most similar to fruits of Fagaceae subfamily Castaneoideae. Bicarpellate fruits and a glabrous endocarp place them within the fossil genus Cascadiacarpa; however, they differ from Cascadiacarpa spinosa in nut wall anatomy, cupule ornamentation, shape, and size. Fruits of Cascadiacarpa exilis sp. nov. are compared with spiny, small compression and impression fossil fruits from the Eocene Taneum Creek locality of Washington State. The characters of the Washington State fossils overlap with those observed in the anatomically preserved Appian Way cupulate fruits and, as such, may represent compression and impression fossils of the same genus. The permineralized fruits document that evalvate, spiny, cupulate nuts of Fagaceae were present and common in the Eocene of western North America.
36
Bronson, Allison W., e John G. Maisey. "Resolving the identity of Platylithophycus, an enigmatic fossil from the Niobrara Chalk (Upper Cretaceous, Coniacian–Campanian)". Journal of Paleontology 92, n. 4 (15 aprile 2018): 743–50. http://dx.doi.org/10.1017/jpa.2018.14.
Testo completoAbstract (sommario):
AbstractMisidentified fossils are common in paleontology, but Platylithophycus has undergone a particularly problematic series of descriptions. The holotype of P. cretaceus comes from the Upper Cretaceous Niobrara Chalk of Kansas, and was first described as a calcareous green alga, based on the surface texture of the specimen. Later, Platylithophycus was re-identified as a sepiid cephalopod, based partly on a comparison of microstructure between P. cretaceus and the pen of modern squids. Platylithophycus then became part of the University of Nebraska teaching collection, where, according to paleontological legend, an undergraduate student suggested that the fossil’s tessellated surface looked a lot like shark cartilage. However, that interpretation has not been formally proposed until now. This work re-describes the holotype of Platylithophycus cretaceus as part of the branchial endoskeleton of an elasmobranch, based on both gross morphology and ultrastructure, including recognizable tessellated cartilage with intertesseral pores and joints.
37
Chrząstek, Alina. "Palaeontology of the Middle Turonian limestones of the Nysa Kłodzka Graben (Sudetes, SW Poland): biostratigraphical and palaeogeographical implications". Geologos 18, n. 2 (1 agosto 2012): 83–109. http://dx.doi.org/10.2478/v10118-012-0007-z.
Testo completoAbstract (sommario):
Palaeontology of the Middle Turonian limestones of the Nysa Kłodzka Graben (Sudetes, SW Poland): biostratigraphical and palaeogeographical implicationsThe ammonitesLewesiceras peramplumMantell and?Lewesicerassp. are reported from the Upper Cretaceous in the Nysa Kłodzka Graben; they date from the Middle Turonian and ?Coniacian, respectively. The Middle Turonian limestones of the Stara Bystrzyca quarry contain an abundant assemblage of inoceramids (Inoceramus cuvieriSowerby and I. lamarcki Parkinson) and other bivalves, including oysters, as well as brachiopods and trace fossils. Micropalaeontological data show the presence of foraminifers and siliceous sponge spiculae, bryozoans, ostracods and fragments of bivalves and gastropods. The Middle Turonian calcareous deposits belongs to the upper part of theInoceramus lamarckiZone (late Middle Turonian) and were deposited on a shallow, subtidal offshore shelf. They overlie the Middle Turonian Bystrzyca and Długopole Sandstones, which represent foreshore-shoreface delta deposits. The fossil assemblage suggests a moderate- to low-energy, normal-salinity environment with occasionally an oxygen deficit.
38
Mohsin, Shatha, Abbas Mohammed e Fahad Alnajm. "Microfossils (Foraminifera and Calcareous Algae) of the Yamama Formation, Southern Iraq". Iraqi Geological Journal 55, n. 1E (31 maggio 2022): 110–27. http://dx.doi.org/10.46717/igj.55.1e.10ms-2022-05-26.
Testo completoAbstract (sommario):
The Yamama Formation is one of the important reservoirs, in southern Iraq. This formation in all studied wells consists of limestone and dolomitic limestone. Microfacies analysis clarified that the formation represented a ramp, inner, middle and outer environments, seventy-one species are recorded, the main fossils are composed of many genera and species related to main groups such as foraminifera, calcareous algae, and stromatoporids with few occurrences of gastropods, bivalves, bryozoa, spiculites and Echinoderms. The study has recorded 6 genera of foraminifera and 11 genera (green algae), 3 species related to Salpingoporella sp., 2 genera related to red algae, 1genera related to Charophytes (nonmarine plants) for the first time in the Yamama Formation.
39
ZAPALSKI, MIKOŁAJ K., e BENOÎT L. M. HUBERT. "First fossil record of parasitism in Devonian calcareous sponges (stromatoporoids)". Parasitology 138, n. 1 (3 agosto 2010): 132–38. http://dx.doi.org/10.1017/s0031182010001071.
Testo completoAbstract (sommario):
SUMMARYIntroduction. Palaeozoic calcareous sponges (stromatoporoids) are common bio-constructing fossils; they are sometimes found in association with helicoidal structures of unknown biological affinities. The interaction between the tube-forming organisms has usually been classified as commensalism. Methods. About 260 stromatoporoid skeletons from the Middle Devonian (Givetian) of the Mont d'Haurs section near Givet (Champagne-Ardenne, France) were thin-sectioned and analysed under transmitted light. Results. Approximately 10% of the examined stromatoporoids (mainly belonging to the genera Actinostroma, Stromatopora and Stromatoporella) contain tubes classified as Torquaysalpinx sp. The Torquaysalpinx organisms penetrated the skeletons of stromatoporoids in vivo (as evidenced by skeletal overgrowths); around the infesting organisms, growth bands are bent down. Conclusion. Diminished growth rates around the infesting organism demonstrate a negative influence on the host, similar to that seen in the modern demosponge–polychaete association of Verongia–Haplosyllis. This is demonstrated by changes in growth bands. As in the above-mentioned association, the endosymbiont might have been feeding directly upon the tissues of the host. The Torquaysalpinx organisms were gaining habitat and possibly also food resources – for them this interaction was clearly positive. This long-term association can therefore be classified as parasitism. This is the first evidence for parasitism in Palaeozoic sponges.
40
Wastegård, Stefan, e Kristian Schoning. "Calcareous fossils and radiocarbon dating of the saline phase of the Yoldia Sea stage". GFF 119, n. 3 (settembre 1997): 245–48. http://dx.doi.org/10.1080/11035899709546482.
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Tapanila, Leif. "Direct Evidence of Ancient Symbiosis Using Trace Fossils". Paleontological Society Papers 14 (ottobre 2008): 271–87. http://dx.doi.org/10.1017/s1089332600001728.
Testo completoAbstract (sommario):
Symbiotic associations are a poorly studied aspect of the fossil record, owing largely to the taphonomic biases that inhibit direct observation that two organisms shared an intimate association in life. A symbiosis between an infesting animal and a skeleton-producing host can form a bioclaustration cavity that directly preserves the association and has a high preservation potential. Identification of ancient mutuals and parasites must reject the null hypothesis of commensalism by demonstrating that the symbiosis correlates with a positive or negative change in host fitness as compared to a non-symbiotic relative of the host taxon. Reviews of the Paleozoic record of marine symbionts show that the majority are hosted by colonial animals, especially corals and calcareous sponges. These hosts include structural forms that have moderate to high levels of integration and can support bioclaustrations between clonal units, mitigating the negative effects of symbionts, and perhaps facilitating the symbiosis.The fossil record is biased toward recording long-lasting, widespread, equilibrated associations. By contrast, parasitisms that are especially negative to the host are expected to be fossilized rarely. The symbiotic associations that form bioclaustrations may also represent an endolithic adaptive strategy in response to biological antagonisms, such as predation and spatial competition. The Late Ordovician rise in symbiotic bioclaustrations joins burrows and borings as trace fossil examples of infaunalization strategies that accompany the Ordovician faunal radiation.
42
Fox, Calum P., Jessica H. Whiteside, Paul E. Olsen, Xingqian Cui, Roger E. Summons, Erdem Idiz e Kliti Grice. "Two-pronged kill mechanism at the end-Triassic mass extinction". Geology 50, n. 4 (5 gennaio 2022): 448–53. http://dx.doi.org/10.1130/g49560.1.
Testo completoAbstract (sommario):
Abstract High-resolution biomarker and compound-specific isotope distributions coupled with the degradation of calcareous fossil remnants reveal that intensive euxinia and decalcification (acidification) driven by Central Atlantic magmatic province (CAMP) activity formed a two-pronged kill mechanism at the end-Triassic mass extinction. In a newly proposed extinction interval for the basal Blue Lias Formation (Bristol Channel Basin, UK), biomarker distributions reveal an episode of persistent photic zone euxinia (PZE) that extended further upward into the surface waters. In the same interval, shelly taxa almost completely disappear. Beginning in the basal paper shales of the Blue Lias Formation, a Lilliput assemblage is preserved consisting of only rare calcitic oysters (Liostrea) and ghost fossils of decalcified aragonitic bivalves. The stressors of PZE and decalcification parsimoniously explain the extinction event and inform possible combined causes of other biotic crises linked to emplacement of large igneous provinces, notably the end-Permian mass extinction, when PZE occurred on a broad and perhaps global scale.
43
Squires, Richard L., e Michael P. Gring. "Late Eocene chemosynthetic? bivalves from suspect cold seeps, Wagonwheel Mountain, central California". Journal of Paleontology 70, n. 1 (gennaio 1996): 63–73. http://dx.doi.org/10.1017/s0022336000023118.
Testo completoAbstract (sommario):
An anomalous pair of small, isolated calcareous sandstone bodies in the middle member of the upper Eocene Wagonwheel Formation, Wagonwheel Mountain, of the San Joaquin Valley, California, contain numerous articulated specimens of soft-bottom-dwelling bivalves. The lucinid bivalve Epilucina washingtoniana (Clark, 1925) dominates the fauna, which also sparingly contains the thyasirid bivalve Conchocele bisecta (Conrad, 1849) and the vesicomyid bivalve Vesicomya (Vesicomya) aff. V. (V.) tschudi Olsson, 1931.The fossils in the pair of calcareous sandstone bodies, which are surrounded by deep-water silty mudstone barren of megafossils, most likely represent cold-seep communities in the upper bathyal environment. These cold seeps apparently were formed by diffusive flow through coarse sand-fill material in submarine channels.Epilucina washingtoniana was previously known only from upper Eocene rocks on the Olympic Peninsula, Washington, and in Santa Barbara County, southern California. This species, along with a late Eocene species from Colombia, South America, are the earliest representatives of Epilucina. The Wagonwheel Formation contains one of the earliest records of Conchocele bisecta, which is a widespread Cenozoic fossil and is extant in the north Pacific. The species of Vesicomya in the Wagonwheel Formation is the earliest record of Vesicomya s.s. and has close affinity to Vescicomya (Vesicomya) tschudi Olsson, 1931, from the upper Oligocene of northwestern Peru, South America. As in the case of Conchocele bisecta, Vesicomya s.s. has not been reported previously from the Eocene of California.
44
Stanley, George D. "Exotic terranes, late Paleozoic to early Mesozoic fossils and circum-Pacific events". Paleontological Society Special Publications 6 (1992): 277. http://dx.doi.org/10.1017/s2475262200008376.
Testo completoAbstract (sommario):
In addition to the breakup of Pangea, other major events occurring in the ancient Pacific during late Paleozoic and early Mesozoic time were the development and dispersal of exotic terranes which now characterize large portions of the eastern and western Pacific margins. While the terrane concept made sense out of the geologic crazy quiltwork pattern of these regions, considerable uncertainties still exist concerning terrane origins and their paleogeographic histories. Did terranes of the eastern and western pacific merely border Pangea or did they once exist within far-flung reaches of the ancient Pacific Ocean? Paleontology is now exploring and seeking answers to such issues based on benthic invertebrate fossils.Like examples in the western Pacific rim of Asia, the American Cordillera contains volcanic terranes with fossil content and history quite different from coeval rocks of the adjacent craton. Some terranes may have developed close to ancient North America, but others show evidence of having existed in settings far-removed from the craton. Over time, some terranes could have experienced considerable geographic displacement via tectonic processes (faulting, rift volcanism, seafloor spreading).Many terranes experienced protracted volcanic episodes of oceanic history during Permian and Triassic time. Terrane amalgamations occurred during Triassic and Jurassic time, and later in the Mesozoic were followed by accretion to the North American Craton. Some terranes such as Quesnellia, Cache Creek, Stikine, Wallowa, Eastern Klamath, and Wrangellia yield excellent benthic marine fossils—many of tropical Tethyan derivation, but other fossil assemblages are of mixed paleogeographic affiliations. Two island arc terranes, Stikinia and Wallowa, contribute to evolutionary and biogeographic issues with Triassic and Jurassic, tropical to temperate marine fossils. These include calcareous algae, sponges and corals occurring in reef sequences which can be related to better known examples from Asia and the former Tethys region. Continuing paleontological investigations into fossils from exotic terranes of the Cordilleran region, offer promise in the resolution of late Paleozoic and early Mesozoic circum-Pacific events and in the attainment of unified views of global paleogeography.
45
Elorza, Javier, e Humberto Astibia. "Fosildiagénesis del anélido Rotularia spirulaea (Lamarck, 1818) (Polychaeta, Serpulidae) en el Eoceno del dominio pirenaico occidental". Spanish Journal of Palaeontology 33, n. 2 (13 dicembre 2018): 299. http://dx.doi.org/10.7203/sjp.33.2.13605.
Testo completoAbstract (sommario):
The presence of the fossil polychaete Rotularia spirulaea (Lamarck, 1818) in Eocene deposits (middle Lutecian – upper Bartonian and (?) Priabonian) belonging to the western Pyrenean Domain is verified. In this paper, a fossildiagenetic study has been carried out. Fossils from three areas, corresponding to diff erent depositional settings, have been analysed. In area 1, sediments of the Ardanatz Sandstone and Ilundain Marls formations [Pamplona Basin and adjoining areas (Navarre)], were sampled. Here, the specimens of R. spirulaea were not substantially affected by taphonomic reworking and the original microstructure of the carbonate tube is preserved. The test consists of a thick external shell layer, composed of three zones in succession, and another extremely thin inner shell layer. The lumen of the tube is filled in by fine-grained sediment and/or calcitic cement. In area 2 , which includes the town of Anderatz and several outcrops of the Urbasa mountain range (Navarre), Urbasa-Andia Formation and overlying deposits, as well as in area 3 , located on the upper part of the calciclastic fl ysch of Punta Galea (Biscay), fossils are included in sediments deposited in high-energy environments. In this case, the microstructure of R. spirulaea tube is not completely recognized due to intense, early diagenetic silicifi cation aff ecting the tests. The lumen is filled in with fragments of foraminifera and calcareous algae, quartz-feldespathic sediment and cemented by calcite. Therefore, in zones 2 and 3 the fossildiagenetic processes are substantially different from those recognized in zone 1.
46
Albrecht, C., H. Vogel, T. Hauffe e T. Wilke. "Sediment core fossils in ancient Lake Ohrid: testing for faunal change since the Last Interglacial". Biogeosciences 7, n. 11 (5 novembre 2010): 3435–46. http://dx.doi.org/10.5194/bg-7-3435-2010.
Testo completoAbstract (sommario):
Abstract. Ancient Lake Ohrid is probably of early Pleistocene or Pliocene origin and amongst the few lakes in the world harbouring an outstanding degree of endemic biodiversity. Although there is a long history of evolutionary research in Lake Ohrid, particularly on molluscs, a mollusc fossil record has been missing up to date. For the first time, gastropod and bivalve fossils are reported from the basal, calcareous part of a 2.6 m long sediment succession (core Co1200) from the north-eastern part of Lake Ohrid. Electron spin resonance (ESR) dating of mollusc shells from the same stratigraphic level yielded an age of 130 ± 28 ka. Lithofacies III sediments, i.e. a stratigraphic subdivision comprising the basal succession of core Co1200 between 181.5–263 cm, appeared solid, greyish-white, and consisted almost entirely of silt-sized endogenic calcite (CaCO3>70%) and intact and broken mollusc shells. Here we compare the faunal composition of the thanatocoenosis with recent mollusc associations in Lake Ohrid. A total of 13 mollusc species (9 gastropod and 4 bivalve species) could be identified within Lithofacies III sediments. The value of sediment core fossils for reconstructing palaeoenvironmental settings was evaluated and the agreement between sediment and palaeontological proxies was tested. The study also aims at investigating major faunal changes since the Last Interglacial and searching for signs of extinction events. The combined findings of the ecological study and the sediment characteristics suggest deposition in a shallow water environment during the Last Interglacial. The fossil fauna exclusively included species also found in the present fauna, i.e. no extinction events are evident for this site since the Last Interglacial. The thanatocoenosis showed the highest similarity with recent Intermediate Layer (5–25 m water depth) mollusc assemblages. The demonstrated existence of a mollusc fossil record in Lake Ohrid sediment cores also has great significance for future deep drilling projects. It can be hoped that a more far reaching mollusc fossil record will then be obtained, enabling insight into the early evolutionary history of Lake Ohrid.
47
Mu, Xinan, e Robert Riding. "Silicification of Permian calcareous algae from Nanjing, China". Geological Magazine 125, n. 2 (marzo 1988): 123–39. http://dx.doi.org/10.1017/s0016756800009535.
Testo completoAbstract (sommario):
AbstractCalcareous algae in limestones of the Permian Chihsia Formation near Nanjing, China, are preferentially replaced by quartz. Replacement postdates both cementation by sparry calcite and also neomorphic alteration of the original skeletons to sparry calcite. It is thus diagenetically relatively late. The original replacement silica could have been massive opal CT, opal CT lepispheres, or quartz. Lepisphere-like bodies occur in a few specimens. Megaquartz rims represent later overgrowths on the silicified skeletons. Although the original ultrastructure of the algal skeletons is not preserved, the preferential silicification allows fine details of the skeletal morphology of the algae to be observed and the distribution of silica indicates the style of replacement which has probably occurred. In some specimens it is possible that dissolution of the skeleton was followed by void-filling by silica, including the possibility of lepisphere formation. But in other cases in situ replacement, probably by massive opal CT or quartz, is reflected by the replacement of the outer parts of calcite crystals by silica. This process produces a network of silica, and as it proceeds the calcite centres of the grains become progressively smaller until silica replacement is complete. Sponge spicules may have provided the most important silica source for replacement. It is proposed that water-insoluble organic films surrounding matrix grains, and now preserved as bituminous material, protected the matrix from replacement thus promoting selective late diagenetic silicification of these fossils.
48
Yang, Hao, Hao Liu e Yongbiao Wang. "Calcareous tube-worm fossils in microbialites after end-Permian mass extinction and their paleoenvironmental implications". Journal of Earth Science 21, S1 (giugno 2010): 174–75. http://dx.doi.org/10.1007/s12583-010-0203-0.
Testo completo
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Bland, B. H., G. Evans, R. Goldring, A. E. Mourant F.R.S, J. T. Renouf e A. D. Squire. "Supposed Precambrian trace fossils from Jersey, Channel Islands". Geological Magazine 124, n. 2 (marzo 1987): 173. http://dx.doi.org/10.1017/s0016756800016009.
Testo completoAbstract (sommario):
abstractSIR - Squire (1973) described and figured fossil burrows, ascribed to Sabellarites, from the Upper Proterozoic Brioverian Jersey Shale Formation of Jersey, Channel Islands. The meander-like structures are from calcisiltite beds within a turbiditic sequence and were collected from low intertidal reefs. Re-examination by all of us of one of Squire's specimens (Jersey Museum, La Hougue Bie, SJM C 2026; Squire, 1973, plate 1 a) and more decisive material (SJM C 1002, 5 specimens), collected later from the same reefs by Stéphane Rault, confirms that the structures are attributable to modern polychaetous annelids, almost certainly to Polydora sp., an attribution with which Dr J. D. George (Head, Polychaeta Section, British Museum (Natural History)) concurs. Polydora is associated with a wide range of substrate preference, constructing borings in hard calcareous substrates, pseudoborings on the inside of shells and true burrows in loose sediment. In the Jersey material the irregular, but quite typical, U-form tubes have been formed along open joint planes with slight dissolution of the rock, or along thin calcite-filled veins, also with dissolution of the rock. The joints occur at all angles to the bedding. Very pertinent is the attitude of the tubes, which is principally normal to the rock surface rather than to the bedding. No tubes have been seen on freshly broken surfaces and in no instance has a tube been seen to enter the rock, though there are numerous moulds of pyritic concretions which happen to be of about the same diameter as the width of the tubes. Lithothamnium sp. is patchily distributed over the rock surface and locally penetrates into the joints, showing that they were open.
50
Albrecht, C., H. Vogel, T. Hauffe e T. Wilke. "Sediment core fossils in ancient Lake Ohrid: testing for faunal change in molluscs since the Last Interglacial period". Biogeosciences Discussions 7, n. 3 (28 maggio 2010): 3969–99. http://dx.doi.org/10.5194/bgd-7-3969-2010.
Testo completoAbstract (sommario):
Abstract. Ancient Lake Ohrid is probably of early Pleistocene or Pliocene origin and amongst the few lakes in the world harboring an outstanding degree of endemic biodiversity. Although there is a long history of evolutionary research in Lake Ohrid, particularly on molluscs, a mollusc fossil record has been missing up to date. For the first time, gastropod and bivalve fossils are reported from the basal, calcareous part of a 2.6 m long sediment succession (core Co1200) from the north-eastern part of Lake Ohrid. Electron spin resonance (ESR) dating of mollusc shells from the same stratigraphic level yielded an age of 130±28 ka. Lithofacies III sediments, i.e. a subdivision of the stratigraphic unit comprising the basal succession of core Co1200 between 181.5–263 cm appeared solid, grayish-white, and consisted almost entirely of silt-sized endogenic calcite (CaCO3>70%) and intact and broken mollusc shells. Here we compare the faunal composition of the thanatocoenosis with recent mollusc associations in Lake Ohrid. A total of 13 mollusc species (9 gastropod and 4 bivalve species) could be identified within Lithofacies III sediments. The value of sediment core fossils for reconstructing palaeoenvironmental settings was evaluated. The agreement between sediment and palaeontological proxies was tested. The combined findings of the ecological study and the sediment characteristics suggest deposition in a shallow water environment during the Last Interglacial period. We tested for major faunal changes since the Last Interglacial period and searched for signs of extinction events. The fossil fauna exclusively included species also found in the present fauna, i.e. no extinction events are evident for this site since the Last Interglacial. The thanatocoenosis showed the highest similarity with recent Intermediate Layer (5–25 m) mollusc assemblages. The demonstrated existence of a mollusc fossil record in Lake Ohrid sediment cores also has great significance for future deep drilling projects. It can be hoped that a more far reaching mollusc fossil record will then be obtained, enabling insight into the early evolutionary history of Lake Ohrid.