Calcareous Microfossils Research Articles

Organic walled dinoflagellate cyst biostratigraphy of the Bartonian/Priabonian GSSP Alano di Piave section, NE Italy

The present paper augments the multidisciplinary stratigraphic analysis of the Global Stratotype Section and Point (GSSP) Bartonian-Priabonian boundary Alano di Piave section (NE Italy). Twenty-seven stratigraphically signficant organic walled dinoflagellate cyst events, calibrated against the magnetostratigraphic polarity timescale, and earlier established zonations based on calcareous microfossils are recognized. Among these events the first occurrence (FO) of Oligokolpoma agniniae sp. nov. (~8 m below the GSSP boundary), and the FO of Reticulatosphaera actinocoronata (~8 m above the GSSP boundary) may be considered as additional stratigraphic indicators for the Bartonian-Priabonian boundary. Six new potentially stratigraphically significant species Heteraulacacysta alanoensis sp. nov., Heteraulacacysta reticulata sp. nov., Impagidinium bellunoensis sp. nov., Impagidinium veneziaense sp. nov., Lophocysta domenicorioi sp. nov., and Oligokolpoma agniniae sp. nov. are formally described.

NEW NON-MARINE OSTRACOD GENERA AND SPECIES OF APTIAN AGE FROM ARARIPE BASIN, NORTHEAST BRAZIL

The Ostracoda Subclass comprises the most expressive group of calcareous microfossils in the deposits of the Araripe Basin, especially in its post-rift sequence, which is represented by the Santana Group, of Late Aptian age (= Alagoas Local Stage). Due to the abundance, ostracod species are of great importance for understanding the evolution of the Araripe Basin, with direct application in biostratigraphic and paleoecological analyses. Improving these important applications involves refining the taxonomy of these ostracods, which also contributes to understanding the diversity of this fauna. Increasing knowledge about the ostracod group, this paper describes new and rare taxa recovered from outcrop and well core samples from the Araripe Basin. Two new genera are proposed, Batecypris gen. nov. and Macunhaella gen. nov., and five new species Batecypris reticularis sp. nov., Macunhaella posteroaltis sp. nov., Timiriasevia aratra sp. nov., Theriosynoecum favus sp. nov. and Wolburgiopsis magnafossa sp. nov.. These five taxa were assigned to the families Cyprididae Baird, 1845 and Limnocytheridae Klie, 1938, which comprise other important and known genera for the Araripe Basin. This study shows that in the Araripe Basin the mentioned families can be more diverse than already known, adding value to the understanding of the pre-salt section deposition.

In search of lost time: Recovering missing stratigraphical data from fossil marine reptile specimens using micropalaeontological analyses

Many museum and university collections contain fossil marine reptile specimens that have no provenance data associated with them, particularly those collected in the 19th and early 20th centuries. This may be because the information was never known to the museum or because the data have since been lost. Moreover, data that are associated with a specimen may have been assumed historically rather than verified and it is known that collectors, donors or sellers of specimens have sometimes been deliberately secretive or even misleading about the actual provenance of the fossils. If invertebrate macrofossils can be identified in the host matrix of the marine reptile specimen these can sometimes offer clues as to the stratigraphical origin of the specimen, but these instances are rare. Micropalaeontological analyses, however, can be undertaken on relatively small amounts of matrix associated with a specimen to attempt the recovery of lost data or confirm or reject assumed provenance details. Permission has been obtained to take small samples (as little as five grams) of host matrix from the rear of several ichthyosaur specimens during recent conservation projects where the provenance of the specimen was either totally unknown or was in doubt. These samples were analysed for their calcareous microfossil content, including ostracods and foraminifera. It was found that well-cemented limestones contained little or no recoverable material but softer mudstones have sometimes yielded very useful assemblages allowing specific biozones to be attributed to the host specimens, successfully recovering lost data and making the specimens much more useful scientifically. Even when the assemblage of microfauna is found to be poor or absent, some information about the sedimentary conditions of the preservational environment can often be ascertained from the micropalaeontological residues.

Neogene carbonate platform development in the southern South China Sea: Evidence from calcareous microfossils

Biogenic reefs are unique geologic bodies that are the products of biological activity in tropical and subtropical oceans and critical to global carbon cycling. The South China Sea (SCS) has developed largest carbonate platforms in the Western Pacific. The fully-cored Well NK-1, which is drilled through the reef complex on the Meiji Atoll, Nansha Islands, offers good opportunity for assessing the long-term evolutions of biogenic reefs in the SCS. The stratigraphic ages based on palaeomagnetic and Sr isotopic data are controversial in some intervals of core NK-1. To reveal the evolution history of Nansha Islands and their controlling factors, more credible age constraints on core NK-1 are needed. This research presents new records of calcareous microfossils (calcareous nannofossil and foraminifer) abundances and diversities in the biogenic reef carbonates of core NK-1. Based on the assemblages of the calcareous microfossils, seven biostratigraphic datums are recognized from the sequence of core NK-1, revealing a general continuous succession of the earliest Miocene to Pleistocene age. By combining with the magnetostratigraphic data, the development and evolution of carbonate platform in Nansha Islands are reconstructed. The bottom age of the biogenic reef sequence of NK-1 is estimated for 23.03 ± 1.06 Ma, close to the Oligocene/Miocene boundary. The new chronology highlights three short hiatuses of 3.6–2.4 Ma, 11.1–10.0 Ma, and 13.5–11.9 Ma, which are well correlated with the prominent exposed surfaces at 210.3 m, 464.6 m and 561.6 m, respectively. It reveals remarkably similar evolution history of carbonate platforms in the SCS since Neogene by comparing with records of stratigraphy and growth rate from deep drilling cores on isolated coral reefs in Nansha and Xisha Islands. The results showed that the SCS carbonate platform developments, which go through Late Oligocene / Early Miocene initiation phase, Early-Middle Miocene rapid growth phase, Middle-Late Miocene erosion phase, Miocene-Pliocene stable development phase and Quaternary growth phase, are mainly influenced by global sea level changes, environmental factors and regional tectonism such as the SCS basin spreading, Sabah Orogeny Movement and Dongsha Movement.

Chronology and Sedimentary Processes in the Western Ross Sea, Antarctica since the Last Glacial Period

The stability of contemporary ice shelves is under threat due to global warming, and the geological records in the Ross Sea offer such an opportunity to test the linkage between them. However, the absence of calcareous microfossils in the sediments of the Ross Sea results in uncertainties in establishing a precise chronology for studies. Hence, three sediment cores were collected and studied in terms of radiocarbon dating, magnetic susceptibility, and sediment grain size to reconstruct the environmental processes in the Ross Sea since the last glacial period. The main results are as follows: (1) two grain-size components were identified for the studied cores, which can be correlated to ice-shelf and sea-ice transport, respectively; (2) due to old-carbon contamination and an inconsistent carbon reservoir, the radiocarbon dates were generally underestimated, and as an alternative, changes in magnetic susceptibility of the studied cores can be tuned to the ice-core records to establish a reliable age–depth model and; (3) integrating sediment grain-size changes and comparisons with other paleoenvironmental proxies in the Antarctic, a process from a sub-ice sheet in the last glacial period to a sub-ice shelf in the glacial maximum, and, finally, to a glaciomarine state since the last deglacial period was identified in the western Ross Sea. Integrating these findings, the warming processes in the Antarctic were highlighted in the retreat processes of the Ross Ice Shelf in the past.

Depositional ages of sedimentary rocks obtained from the sea floor around the northern Tokara Islands during GB21-3 cruise, based on calcareous microfossil assemblages, and their geological significance

Depositional ages of sedimentary rocks obtained from the sea floor around the northern Tokara Islands during GB21-3 cruise, based on calcareous microfossil assemblages, and their geological significance

Microfossils and biostratigraphy of the Upper Cretaceous Coon Creek Formation Lagerstätte, Mississippi Embayment, USA

Abstract The Upper Cretaceous Coon Creek Formation type-locality in McNairy County, Tennessee, is an exceptional marine invertebrate Lagerstätte that was deposited in a nearshore reentrant into the ancestral continent of Appalachia. Extensive taxonomic analysis of the macrofauna has been done for over 100 years. However, documentation of the microfossil component at the type-locality has largely been ignored. This paper provides analysis of calcareous microfossils (benthic and planktonic foraminifera, calcareous nannofossils and ostracods) and palynomorphs (pollen, spores, algal remains and dinoflagellates) for detailed age control and information regarding environment of deposition. The Coon Creek type-locality is late Campanian (76.8–76.0 Ma) in age and was deposited in 35–60 m water depths. Calcareous nannofossil assemblages suggest that there was an influence of colder water through time, possibly by a connection to the northern Western Interior Seaway. The complex interplay between currents of the Gulf of Mexico and the Western Interior Seaway, upwelling and runoff influenced the palaeoenvironment. Increased influx of freshwater palynomorphs near the top of the section suggests placement proximal to the palaeoshoreline and that weathering increased through time. Changes in the dinoflagellate assemblage may be linked to a mosasaur mass mortality event and the presence of a harmful algal bloom.

Integrated study of the microfossils of the upper Aptian (Lower Cretaceous) of the Sobradinho and Serra do Mãozinha sections (Araripe Basin, northeastern Brazil): Biostratigraphic and paleoenvironmental inferences

The present study reports the results of an integrated analysis of the microfossil assemblages from the Sobradinho and Serra do Mãozinha sections of the upper Aptian Romualdo Formation in the Araripe Basin, northeastern Brazil. The analysis of the distribution pattern of palynomorphs (terrestrial and marine), foraminifera, and ostracods revealed the presence of the palynomorph Sergipea variverrucata and the ostracod Damonella grandiensis, which supported the allocation of the principal portion of the sections to the Sergipea variverrucata Palynozone (P-270) and Ostracod Biozone O11, which are both indicators of the Aptian (= Alagoas local Stage). The frequent occurrence of both marine and continental palynomorphs, as well as calcareous microfossils, provide evidence of a coastal marine to restricted transitional environments, under a semi-arid to arid climate, with two well-defined marine incursions. The highlight of the data from the Serra do Mãozinha section is a new record of the Subtilisphaera Ecozone. In this section, the monospecific Subtilisphaera microflora represents the interval of weak marine influence. By contrast, the Sobradinho section is characterized by the occurrence of calcareous microfossils, foraminiferal linings, and a previously undocumented association of dinocysts, including 13 genera with four taxa being identified to species. Of these, Atopodinium cf. Iuvene, Apteodinium maculatum, Batiacasphaera sp., Circulodinium sp., Impagidinium sp., Gonyaulacysta sp., and Pervosphaeridium sp. Were recorded in the Araripe Basin for the first time.

Eocene to Miocene palynology of the Amagá Basin (Cauca Valley, Colombia) compared to the Caribbean Region

The Cenozoic sedimentary basins of northwestern Colombia contain clues to understanding the evolution of past ecosystems and their possible relationship to regional events, such as the uplift of the northern Andes and the collision of the Panama-Chocó Block with the South American continent. However, these basins have not been thoroughly investigated. This work aims to fill this knowledge gap by performing a comprehensive palynological analysis of the Amagá Basin (Valle del Cauca). Three outcrops were studied to determine their depositional ages, paleoenvironments, and overall floral composition over time. To contextualize our analyses, a comparison was made with two drill holes (ANH-SSJ-Nueva Esperanza-1X and ANH-San Jacinto-1) in the Sinú-San Jacinto Basin in the Colombian Caribbean. The application of the palynological zonation from the Llanos Basin in eastern Colombia was also used to evaluate its suitability in the Amagá Basin. The age of deposition was determined by using several traditional palynostratigraphic markers, including Perisyncolporites pokornyi, Foveotriporites hammeni, Retibrevitricolporites speciosus, Magnastriatites grandiosus, Concavissimisporites fossulatus, Clavainaperturites microclavatus, and Polypodiaceoisporites pseudopsilatus. This assemblage indicates a Middle to Late Eocene, Oligocene, and Miocene age spanning from ~40 to 18 Ma (~22 Myr). However, there are also some differences with respect to the Llanos zonation, such as the absence of Cicatricosisporites dorogensis. Based on this age model, we question whether it is correct to include all these deposits in a single lithostratigraphic unit under the rank of a formation. In the Caribbean, stratigraphic units of similar age exhibit a greater number of key taxa than in the Llanos zonation. In addition, the presence of calcareous microfossils allows for a more detailed determination of the sedimentation age. Furthermore, the discovery of new pollen and spore species could improve the resolution of the biostratigraphy in western Colombia. In the Amagá Basin, only terrestrial palynomorphs were found, which, together with the sedimentary facies, suggest a humid lowland tropical vegetation in fluvial and lacustrine environments.

The Nature of Opal Burial in the Equatorial Atlantic During the Deglaciation

AbstractRelatively high opal concentrations are measured in equatorial Atlantic sediments from the most recent deglaciation. To shed light on their causes, seven cores were analyzed for their content of siliceous (diatom, silicoflagellates, radiolarians, phytoliths, and sponge spicules) and calcareous (coccolithophores) microfossils. An early deglacial signal is detected at the time of rising boreal summer insolation ca. 18 ka by the coccolithophores. The surface freshening is likely due to the rain belt associated with the intertropical convergence zone (ITCZ), implying its southward shift relatively to its present‐day average positioning. The diatom assemblages corresponding to the following increase in diatom abundances ca. 15.5 ka suggest the formation of a cold tongue of upwelled water associated with tropical instability waves propagating westward. Such conditions occur at present during boreal summer, when southerly trade winds are intensified, and the ITCZ shifts northward. The presence of the diatom Ethmodiscus rex (Wallich) Hendey and the coccolithophore Florisphera profunda indicates a deep thermocline and nutrient enrichment of the lower photic zone, revealing that Si‐rich southern sourced water (SSW) likely contributed to enhanced primary productivity during this time interval. The discrepancies between the maximum opal concentrations and siliceous marine microfossils records evidence the contribution of freshwater diatoms and phytoliths, indicative of other processes. The definition of the nature of the opal record suggests successive productivity conditions associated with specific atmospheric settings determining the latitudinal ITCZ positioning and the development of oceanic processes; and major oceanic circulation changes permitting the contribution of SSW to marine productivity at this latitude.

In situ Strontium isotope stratigraphy of fish teeth in deep-sea sediments from the western Clarion-Clipperton Fracture Zone, eastern Pacific Ocean

The geochronology of deep-sea sediments beneath the carbonate compensation depth (CCD) presents a challenge due to the calcareous microfossils dissolution, low sedimentation rates, sedimentary hiatus, and redeposition. Fish teeth, commonly found in deep-sea sediments, have been utilized for Sr isotope stratigraphic dating. However, continuous Sr isotope exchange with pore water limits the utility of fish teeth in this context.In this study, we employed laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICPMS), scanning electron microscopy (SEM), and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) to obtain accurate stratigraphic chronology results from rare earth element and yttrium (REY)-rich sediments in the Clarion-Clipperton Fracture Zone (CCFZ) of the Pacific Ocean.Our analysis indicated that a fish tooth characterized by a dense structure and low La content exhibited a relatively initial 87Sr/86Sr ratio. Additionally, La contents at the same depth displayed a strong positive correlation with 87Sr/86Sr ratios, suggesting that Sr isotopes exchange with pore water during early diagenesis when La and other elements entered the fish teeth. However, certain fish teeth were able to resist early diagenesis alteration due to their dense structure.Based on in situ Sr-isotope stratigraphy results, we estimated the REY-rich layer age in core GC1901 to be 24–32 Ma, consistent with the REY-rich layers of DSDP/ODP in the CCFZ. Our study thus provides a new method for in situ Sr isotope analysis of fish teeth, which improves the accuracy of Sr isotope stratigraphy of pelagic sediments and could be widely used in deep-sea exploration.

Calcareous microfossil biostratigraphy of Upper Miocene to Pliocene deposits of the Sinú-San Jacinto Belt, Caribbean region of Colombia

A compilation of previous biostratigraphic studies conducted in Upper Miocene to Pliocene deposits from the Caribbean region of Colombia reveals a predominant reliance on mollusks and benthic foraminifera for age determinations, with planktonic microfossils being less explored. To contribute to this biostratigraphic background, we have performed biostratigraphic analyses of calcareous nannoplankton, an oceanic planktonic micropaleontological group, on 71 mudrock samples from two stratigraphic sections located in the Sinú-San Jacinto Belt (SSJB). The Canalete stratigraphic section, outcropping in the southwestern portion of the belt, yielded the biostratigraphic markers Discoaster bergenii, Discoaster berggrenii, Discoaster surculus, and Reticulofenestra pseudoumbilicus. This assemblage, typical of the Zone NN11, indicates that the 50-m-thick section was accumulated during the Late Miocene, sometime between the late Tortonian and late Messinian. The ANH-Conuco-1 well, a cored stratigraphic section drilled in the northeastern area of the belt, also contained the above-mentioned biostratigraphic markers as well as Amaurolithus primus-delicatus, Ceratolithus acutus, Discoaster quinqueramus, Helicosphaera sellii, and Reticulofenestra rotaria. These taxa suggest that the stratigraphic interval between 754.1 m and 58.4 m in this cored section is enclosed within the zones NN11 and NN12, ranging in age from Late Miocene to Early Pliocene (late Tortonian to earliest Zanclean). Reworked nannofossils Cyclicargolithus floridanus, Discoaster deflandrei, Sphenolithus disbelemnos, and Sphenolithus heteromorphus were observed in both localities, implying the redeposition of Lower to Middle Miocene and, possibly, Paleogene marine sediments. This is supported by previous documentation of reworked planktonic foraminifera in Upper Miocene to Pliocene deposits from the Caribbean region of Colombia. The identified calcareous nannoplankton assemblages not only provide additional constraints on the existing biostratigraphic data of planktonic foraminifera in this region, but also aid in the correlation of both analyzed stratigraphic sections with other Upper Miocene deposits in northwestern South America.

Lower Ordovician calcareous microfossils from the San Juan Formation, Argentina: a new type of calcitarch and its paleoenvironmental implications

The calcareous microfossils present in the Ordovician and Silurian carbonate successions around the world are limited to few studies and their biological affinities and environmental preferences remain indefinite. In the carbonate Ordovician San Juan Formation from the Cerro La Chilca section, a group of calcareous microfossils was recognized and, based on their size, they are included in the calcitarch classification. Two types of calcitarchs have been recognized, Type-III calcitarch: large spheres with a thin to medium wall (diameter ~250 μm), and Type-0 calcitarch: small spheres with a thin wall (diameter ~80 μm). The carbonate microfacies analysis of the lower part of the San Juan Formation allowed defining five successive microfacies: burrowed bioclastic wackestone (M1), peloidal intraclastic packstone-grainstone (M2), intraclastic floatstone (M3), intraclastic wackestone-packstone (M4) and bioclastic boundstone (M5). These microfacies are interpreted to range from shallow subtidal facies below wave action to shoal and reef facies. It is possible to infer that the recovered calcitarchs show variations in size in relation to the facies that contain them. The calcitarchs recognized in wackestone-type facies are the Type-0 calcitarch and those recovered from the packstone-grainstone facies are the Type-III calcitarch. The calcitarch sizes variation probably is related to a gradual increase of energy within a shallow subtidal environment. Occurrences of calcitarchs within the Floian Oepikodus evae-O. intermedius conodont zone extends their fossil record into the Early Ordovician.

Extraction of calcareous dacryoconarid microfossils from limestones and mudrocks by surfactants paired with freeze-thaw processing

Microfossils offer a wealth of paleoenvironmental information, but their extraction from consolidated material, especially ancient rocks, is time-consuming and often lacks systematic methodological development. This study examined the efficacy of repeated freeze-thaw processing paired with different surfactants (anionic, cationic, and detergent) on the extraction of fossils from the order Dacryoconarida, conically shaped calcareous microfossils that occur in diverse marine facies of the Devonian Period. A stepwise technique was developed involving saturation of rocks in either 18 Ω water or 25% NaCl, followed by freezing and then boiling in surfactant (Pinequat, Decon 90, or Calgon in Na2CO3 solution). In comparison with saturation in NaCl solution, saturation in water generally had higher yields of disaggregated material and more intact fossils. All surfactants performed better at extraction compared to boiling in pure water. Across all lithologies examined, Na2CO3-buffered Calgon (sodium hexametaphosphate) disaggregated rock most efficiently, but Na2CO3 solution alone generally had the highest yield of total and intact fossil specimens. Pinequat, a cationic surfactant, yielded more disaggregate for siliclastic samples compared to calcareous samples, but had lower fossil yield. Decon 90, an anionic surfactant, performed better at disaggregating limestones and had higher fossil extraction efficiency than Pinequat across all lithologies. Freeze-thaw processing pairing water saturation and 5% Na2CO3 simmering is an effective treatment for the disaggregation of rocks to extract analytically viable amounts of dacryoconarids from fossiliferous samples. This pairing had greater fossil extraction potential than surfactants at the concentrations tested in this study and is recommended if the elemental composition of the target rocks is unconstrained.

Age and Depositional Environment of Whale-Bearing Sedimentary Succession from the Lower Pliocene of Tuscany (Italy): Insights from Palaeomagnetism, Calcareous Microfossils and Facies Analyses

A c. 31 m thick section straddling the fossil find of an Early Pliocene baleen whale (“Brunella”, hereafter), made in 2007 in the sedimentary fill of the Middle Ombrone Basin of Tuscany, is investigated for depositional age and environment combining palaeomagnetic, micropalaeontological (Foraminifera and calcareous nannofossils) and sedimentary facies analyses. Resting unconformably onto Late Miocene continental deposits, the Early Pliocene marine deposits include, from bottom to top, a coarse-grained wave-winnowing lag, the few metres-thick fossiliferous sandstone bedset from which Brunella was unearthed, and several metres of clays. The stratigraphic organisation of these deposits indicate deposition in a deepening upward inner shelf environment. Successful isolation of characteristic remanent magnetisation and calcareous nannofossil content indicate the investigated marine section was deposited during the interval of polarity Chron C3n.2n corresponding to the basal part of the Mediterranean nannofossil zone MNN13 (between Helicosphaera sellii Base common and the Amaurolithus primus Top) and allow estimating the depositional age of Brunella to c. 4.6 Ma. Sedimentary facies, benthic Foraminifera association and anisotropy of magnetic susceptibility characterising the deposits that embedded Brunella suggest deposition above the fair-weather base level.

Lower to Middle Miocene multiproxy biostratigraphy of the P-18 core-stratigraphic well in Sinú-San Jacinto Basin, Caribbean region of Colombia

A Lower-to-Middle Miocene core-stratigraphic section, P-18 well, was drilled in the Sinú-San Jacinto Basin (SSJB) in the Caribbean region of Colombia, showing exceptionally well-preserved planktonic foraminifera, calcareous nannofossils, and palynomorphs. We use these micropaleontological groups to perform integrated biostratigraphic analyzes and estimate the stratigraphic record's continuity and sedimentation rates for the early Neogene of the region. Two lithological intervals were defined, the first between 423.9 m and 345.8 m and the second between 345.8 m to the top of the core. Only palynomorphs were identified for the first interval of this section, assigned to the Ciénaga de Oro Formation. We proposed an age no older than 19.49 Ma (Early Miocene, Burdigalian) based on the occurrence of Rugutricolpites intensus at 381.5 m. Although for the second interval, correlated with the Porquera Formation, we found three well-calibrated bioevents of calcareous microfossils, top of Sphenolithus belemnos at 213.2 m, base of Sphenolithus heteromorphus at 187.9 m, and top of Catapsydrax dissimilis at 141.9 m. In addition, we identified the top of uncalibrated planktonic foraminifera Trilobatus primordius, Globigerinoides altiaperturus, Paragloborotalia semivera, Paragloborotalia acrostoma, and Globoturborotalita pseudopraebulloides. Our age model along the P-18 well indicates a time range from ≥19.01 Ma (Early Miocene, Burdigalian) to ∼14.70 Ma (Middle Miocene, Langhian) equivalent to the calcareous nannofossils biozones NN3 to NN4, or, M3 to M5? Of planktonic foraminifera or palynological zones from T12 to T14? Even though we do not observe standard Middle Miocene bioevents with well-calibrated ages, the occurrence of nannofossils taxa Helicosphaera ampliaperta, and planktonic foraminifera Paragloborotalia semivera, Paragloborotalia acrostoma, and Globoturborotalita pseudopraebulloides show a distinctive biostratigraphic pattern, suggesting an age of ∼14.70 Ma to the top of the core section. Estimated sedimentation rates display high values (∼120 m/Myr to ∼219 m/Myr) during the Burdigallian (Early Miocene). They coincide with the regional subsidence increase during the Early Neogene in SSJB and Lower Magdalena Valley and the Early Miocene marine flooding event recorded in the Eastern Llanos Basin (ELB). From 17.60 Ma onwards, sedimentation rates decrease considerably, and a hiatus between 17.54 Ma and 16.96 Ma is interpreted as being tied to an abrupt change in sedimentology from calcareous mudrocks (marls) to very fine sandstones and sandy limestones. Finally, our data suggest that sedimentation rates in the basin were higher than marine sedimentation for ODP 999 during the same period.

Depositional ages of sediment and sedimentary rock samples obtained from the seafloor around the Tokara Islands during GB21-1 cruise, based on calcareous microfossil assemblages

Depositional ages of sediment and sedimentary rock samples obtained from the seafloor around the Tokara Islands during GB21-1 cruise, based on calcareous microfossil assemblages

Early Eocene (Ypresian) palynology of marine sediments from the colombian Caribbean

The Caribbean area is currently considered a frontier basin for hydrocarbon exploration; however, the knowledge of the Cenozoic geological evolution is controversial and requires to be reviewed as new information becomes available. This study integrates for the first-time calcareous microfossils and palynomorphs and proposes a biostratigraphic framework for the early Eocene (Ypresian), in two marine sequences obtained from the ANH Piedras Blancas 1-X and ANH San Cayetano 1-X wells drilled in the Sinu-San Jacinto basin. This information was compared with palynological publications in the Llanos, Llanos Foothills, Middle Magdalena Valley, Catatumbo, and Maracaibo basins. The new information from the Caribbean suggests that the marine palynomorph events reported in the Llanos are diachronic, but they concur with global records in low-middle latitude. Similarly, we extend the biostratigraphic range of some terrestrial palynomorphs considered traditionally of Oligocene-Miocene until Ypresian. In the studied wells lateral changes of facies (turbiditic fan to outer fan-abyssal plain) seem to control the preservation and abundance of calcareous microfossils (calcareous nannofossils and planktonic foraminifera), however, the terrestrial palynology did not show stronger variation.

Chemické složení amfibolů v polétavém prachu z vybraných lokalit Brněnska

This study aimed to characterise the morphological and chemical properties of amphiboles from airborne dust samples collected from three localities in Brno and its surroundings. We analysed approximately 3 g of airborne dust particles from each sample. The mineralogical and morphological characteristics of the dust particles were examined by polarised-light microscopy and electron microprobe analysis. All studied airborne dust inorganic particles with length ≥ 5 μm show a ratio ≤ 3 : 1 or diameter of > 3 μm and therefore do not be potentially dangerous to human health. We compared the chemical analyses of airborne needle-like dust particles (tremolite-actinolite, magnesiohornblende, pargasite; Si = 6.32–7.90 apfu; Mg/(Mg+Fe2+) = 0.34–0.84) with existing chemical composition amphiboles from possible source areas. The amphibole in airborne dust from the locality in the centre of the Brno town is completely dominated by actinolite and magnesiohornblende (Si = 6.48–7.56 apfu; Mg/(Mg+Fe2+) = 0.50–0.80) derived from basic and ultrabasic rocks of the Central Basic Belt of the Brno Massif. The granitoids of the Brno massif can be also a significant source of dust particles. Anthropogenic activity can explain a substantial proportion of amphibole from a relatively small body of amphibolites near Želešice (quarry in the Central Basic Belt of the Brno Massif) because these rocks are widely used as sanding material in the entire Brno agglomeration. The second locality of Rosice (west of Brno) is dominated by amphiboles (Si = 6.51–7.90 apfu; Mg/(Mg+Fe2+) = 0.55–0.84) from the west and northwest metamorphic units (Moravian and Moldanubicum). However, amphiboles from the rocks of the Brno massif are also presented. Amphiboles in the airborne dust from the Rajhradice (locality situated S from Brno) predominantly originated from the rocks of the Central Basic Belt of the Brno Massif (Si = 6.85–7.63 apfu; Mg/(Mg+Fe2+) = 0.50–0.78). Calcareous microfossils suggest that an essential component of the dust is also the material transported from the southeast, where dominated sediments of the Carpathian Flysch units and their foreland. Our results validate amphiboles as valuable minerals for identifying source areas from which dust has been derived and confirm dominant wind flows in the SE and NW directions.

Automated detection of microfossil fish teeth from slide images using combined deep learning models

Microfossil fish teeth, known as ichthyoliths, provide a key constraint on the depositional age and environment of deep-sea sediments, especially pelagic clays where siliceous and calcareous microfossils are rarely observed. However, traditional methods for the observation of ichthyoliths require considerable time and manual labor, which can hinder their wider application. In this study, we constructed a system to automatically detect ichthyoliths in microscopic images by combining two open source deep learning models. First, the regions for ichthyoliths within the microscopic images are predicted by the instance segmentation model Mask R–CNN. All the detected regions are then re-classified using the image classification model EfficientNet-V2 to determine the classes more accurately. Compared with only using the Mask R–CNN model, the combined system offers significantly higher performance (89.0% precision, 78.6% recall, and an F1 score of 83.5%), demonstrating the utility of the system. Our system can also predict the lengths of the teeth that have been detected, with more than 90% of the predicted lengths being within ±20% of measured length. This system provides a novel, automated, and reliable approach for the detection and length measurement of ichthyoliths from microscope images that can be applied in a range of paleoceanographic and paleoecological contexts.