Biostratigraphic Zones Research Articles

A palynological zonation for the Neogene of the Solimões/Amazon Basin, northwestern Amazonia

The tropical rainforests of northwestern Amazonia possess the highest plant diversity of any biome in the world. Understanding their origin, development, maintenance, and future in the face of ongoing global warming requires study of the plant fossil record and a predictive time framework. In this region, palynology is the best biostratigraphic tool because palynomorphs are the most abundant fossils. To construct a biostratigraphic zonation for the Neogene of the Solimões/Amazon basin in northwestern Amazonia, we analyzed palynological information from 25 sections, a total of 143,411 palynomorph grains from 622 samples. Using graphic correlation, we propose seven palynological zones that comprise the Miocene and a portion of the Pleistocene—the Pliocene is absent in the region. We then calibrated these zones against the geological timescale through correlation with a previously calibrated zonation and U/Pb geochronology.

The Frasnian stage of the Upper Devonian in Nakhichevan Autonomous Republic (Southern Transcaucasia)

Marine carbonate-terrigenous deposits of the Lower (partially), Middle, and Upper Devonian, rich in coral-brachiopod and other fauna, are widespread across the territory of the Nakhichevan Autonomous Republic. Various ore and non-metallic minerals are associated with these deposits: the Gyumushlug and Yaydzhinsky polymetallic deposits, etc. Further ex-pansion of the mineral resources of the study area, as well as the challenges associated with the establishment of large-scale geological mapping in this region, make the development of a detailed stratigraphic scheme crucial. An indispensable condition for the creation of such a scheme is the study of the most characteristic groups of ancient organisms, among which brachiopods play a dominant role in the organic world. Devonian deposits in the Southern Transcaucasus are distributed over a limited area – in the western part of the Na- khchivan Autonomous Republic – but they are widespread here and are represented by all three well-characterized faunal divisions. For the first time, a diagram has been compiled, reflecting the sequence of appearance and distribution over time of Devonian brachiopods. On this basis, a scheme for the zonal division of the Devonian deposits in the region has been developed, identifying 20 biostratigraphic zones and 16 stratigraphic units (formations). This study summarizes the scattered information contained in various sources on the paleontology and stratigraphy of the Devonian period in the region. The identified brachiopod zones are linked to standard conodont zones. The great importance of brachiopods is determined by the fact that they are one of the most effective groups of fauna not only for dating sediments in natural outcrops, but they also provide good results for broad interregional correlations. Based on the macrofaunal complex, the Frasnian age of the sediments within the formation in question is firmly established. A detailed biostratigraphic scheme with zonal division of the Devonian deposits of Transcaucasia was developed, based on the most important stages in the development of the brachiopod fauna. Biostratigraphic zones, formations, and subformations identified in the Devonian deposits of the Nakhchivan Autonomous Republic and adjacent areas, based on the study of the entire complex of organic remains, mainly brachiopods and cono- donts, can be compared with corresponding deposits of typical sections of Western Europe (Ardennes and Eifel Mountains) and many regions of Eurasia. The obtained data are of practical importance for theoretical geologists, prospectors and developers.

Rapid evolution in Turonian microcrinoids (Crinoidea, Roveacrinidae) and its significance for Late Cretaceous stratigraphy

Pelagic microcrinoids from the lower and middle Turonian chalks of the Anglo-Paris Basin (southern England, northern France) have distinctive morphologies that demonstrate rapid evolution among three genera, Dentatocrinus Gale, 2019a, Drepanocrinus Jækel, 1918 and Striacrinus gen. nov., and their constituent species and subspecific formae. These form the basis for a refined biostratigraphic zonation that can be applied across the basin. The genus Striacrinus is described as new (type species Drepanocrinus striatulus Gale, 2019a), with a new species S. ornatus described from the middle Turonian. A succession of stratigraphically restricted formae are recognised within Dentatocrinus dentatus Gale, 2019a, described herein as D. dentatus forma inflatus nov., D. dentatus forma subspinosus nov., D. dentatus forma spinosus nov., and D. dentatus forma conicus nov. These formae had ranges with a mean duration of 100–200 kyr as determined from orbital precession cycles.

High-resolution biostratigraphic zonation across the Cretaceous/Paleogene (K/Pg) boundary from the Sulaymaniyah area, Kurdistan Region, Northeastern Iraq

High-resolution biostratigraphic zonation across the Cretaceous/Paleogene (K/Pg) boundary from the Sulaymaniyah area, Kurdistan Region, Northeastern Iraq

Calcareous nannofossils biostratigraphy of well Uche 1, Offshore Lagos, Eastern Dahomey Basin, South Western Nigeria

Well Uche 1 drilled in the offshore of Dahomey Basin was biostratigraphically analyzed, based on its calcareous nannofossils content. Thirty analyzed samples were collected from the Well at an interval range of 20m at a depth of 1284m- 1860m. The microscopic examination of the processed samples was carried out (using simple smear method) and this was found useful in the identification of the different biostratigraphic zones present. Moreover, it is equally found useful in age determination. In all, fifteen (15) calcareous nannofossil species (Braarudosphaera bigelowii, Calcidiscus leptoporus, Coccolithus nitescens, Coccolithus pelagicus, Coronocyclus nitescens, Discoaster deflandrei, Discoaster druggii, Discoaster sp (6rays), Helicosphaera cateri,Pontosphaera multipora, Reticulofenestra haqii (3-5 microns), Reticulofenestra pseudoumbilicus (5-7 microns), Reticulofenestra pseudoumbilicus (>7 µ), Sphenolithus moriformis, Triquetrorhabdulus carinatus) were identified and used for biozonation and identification of significant time surfaces. The distribution of the calcareous nanofossil species in the well enabled the establishment of zones belonging to the Early Miocene; NN2 zone. The most abundant calcareous nannofossils identified are Triquetrorhabdulus carinatus, Cyclicargolithus abisectus and Discoaster druggi. Two biozones of calcareous nannofossils were identified from the well as well as three significant surfaces.

Biostratigraphy and Paleoecology of the Sinjar Formation (Late Paleocene-Early Eocene) in the Dokan and Sinjar Areas, Iraq

Biostratigraphy of the Sinjar Formation is investigated in two sections (Dokan and Sinjar) from northeastern and northwestern Iraq, respectively. Two hundred samples from all the limestones and marl that form the main lithological components of the studied sections were collected. The studied limestones and marl are rich in microfossils. Through thin sections, we were able to identify thirty species of benthic foraminifera and fifteen species of other microfossils (coral, algae, mollusca, bryozoa, and echinoids) at Dokan section, and fifty-one species of benthic foraminifera and thirty species of other microfossils at Sinjar section. 3 biozones were distinguished from both sections 1-Biozone A: Kathina sp.- Lockhartia hunti Assemblage zone (SBZ 5) (Dokan section); (Kathina pemavuti - Lockhartia hunti Assemblage zone (Sinjar section), 2- Biozone B: Idalina sinjarica Total Range zone (SBZ 6-7) and 3-Biozone C: Alveolina globosa- Alveolina pasitisilata Concurrent Range Zone (SBZ8-10). These zones indicate the Late Paleocene –Early Eocene age of the Sinjar formation. The biostratigraphic correlations in the studied sections are based on benthic foraminiferal zonations. Showed the correlation comparison between the biostratigraphic zones of the commonly used benthic zonal scheme around the Late Paleocene -Early Eocene in and outside of Iraq. paleoecological studies suggest that the carbonate sedimentation of the Sinjar Formation thrived in 18-25oC, with mesophotic to oligophobic light, under an oligotrophic to mesotrophic middle ramp environment with normal marine to slightly saline and at water depths from 40 - 80 m. Stable isotopic carbon (δ13C) and oxygen (δ18O) data revealed generally hot conditions with high productivity during the deposition of the Sinjar Formation accompanied by an abrupt change in paleoenvironmental conditions across the Paleocene-Eocene contact.

Biostratigraphy and Depositional Environment of the Upper Disang Formation, Indo-Myanmar Ranges, Northeast India

This paper presents the results of Eocene molluscan fauna and benthic foraminifera from the Upper Disang Formation of Indo-Myanmar Ranges (IMR) and discussed here the biostratigraphic zone and depositional environment. These fauna and foraminifera are composed of Bivalvia viz. Noetia magnifica, Pitar (Calpitaria) carteri, Corbula (Bicorbula) rakhiensis, Gastropoda viz. Turritella sp., Turbinella premekranica, Lyria samanaensis and foraminifera Nummulites sp. On the basis of molluscan fauna Noetia magnifica, the biostratigraphic zone (Zone-I) is established and assigned middle-late Eocene age to Upper Disang Formation of IMR, Nagaland. The presence of invertebrate fossils and benthic foraminifers indicate a warm tropical-subtropical climate and shallow marine (neritic) depositional environment during the sedimentation of the Upper Disang Formation. Keywords: IMR, Inner Paleogene Fold Belt, Molluscan Fauna, Nummulites, Phesama, Upper Disang Formation

Nannobiostratigraphy of Jaddala Formation in (K- 152) well, Kirkuk oilfield, Northern Iraq

From the Jaddala Formation in northern Iraq in the (K152) well, there are (12 species) of calcareous nannofossils described (belonging to 8 genera), (6 families) following a detailed analysis of calcareous nannofossils. The Jaddala Formation comprises one biostratigraphic zones that have been discovered, Coccolithus staurion Partial Taxon range biozone (CP13c) and its age has been assessed to be in the middle Eocene. Therefore, we proposed a middle Eocene (Lutetian to Bartonian) date for the Jaddala Formation.

Upper Triassic (middle Norian) conodont biostratigraphy succession from Qamdo, eastern Tibet

The Late Triassic is a critical period that witnessed major biological and environmental events. The geographic range and taxonomic diversity of conodonts were significantly changed during the Late Triassic, with the geographic range contracting prior to complete extinction of the group near the end of the Triassic. In the present study, we recognize for the first time a continuous middle Norian (Upper Triassic) conodont succession from the Qamdo (Changdu) area, eastern Tibet (Xizang), which was part of the North Qiangtang and Qamdo-Simao Block (NQ-QSB) located in the northeastern Tethys Ocean during the Late Triassic. Four conodont zones are established from the middle Norian (Alaunian) of the Chaiwei section in Qamdo, and in ascending order these are: the Epigondolella spiculata Zone, the Orchardella elongata Zone, the Mockina postera Zone, and the E. serrulata Zone; the neighboring Tuoba section also records these four zones, in addition to the upper lower Norian (upper Lacian) Ancyrogondolella uniformis Zone. All of these zones (except for the M. postera Zone) have been recognized for the first time in eastern Tibet. The Lacian-Alaunian boundary is tentatively placed at the level of sample CW-3 at the Chaiwei section and at the level of sample TBL-36 at the Tuoba section by the first occurrence (FO) of E. spiculata in each section. The position of the Alaunian-Sevatian boundary (ASB) is uncertain since the conodont assemblage from the top of the Bolila Formation at the study sections lacks age-diagnostic elements. The conodonts recovered from the Qamdo area have not only dated the Bolila Formation but also refined the conodont biostratigraphic zonation of the Alaunian in the study area. This allows improved correlation between the faunas of Qamdo and their counterparts elsewhere in Tibet and Europe, although the conodont zonations from these regions display lower precision than those established from North America. The Alaunian conodont faunas at Chaiwei and Tuoba appear to be dominated by juvenile specimens; this often appears to be the case in the Alaunian of the Tethyan Realm, but seems not occur in North America. This may suggest that the conodonts living in these two realms may have inhabited different ecological environments. The faunal turnover around the Lacian-Alaunian transition, with the evolution of Epigondolella, Orchardella, and Mockina from Ancyrogondolella, can be recognized in both study sections, although it is more remarkable in the Tuoba section. Although the lack of previous detailed studies of Norian conodont biostratigraphy from Tibet hampers correlation in this region and beyond, this study demonstrates the possibility of establishing high-resolution conodont biostratigraphic successions from Tibet in the future, since the conodont faunas recognized from Tibet and adjacent areas (e.g., Baoshan) suggest that relatively complete Norian strata exist in these regions. Overall, this study also provides new data to improve our understanding of conodont evolution during the Alaunian, and is significant in providing palaeontological data for studying the palaeogeographic evolution of eastern Tethyan ocean basins in the Late Triassic.

Aptian–Albian sequence stratigraphy, biostratigraphy, chemostratigraphy, and chronostratigraphy: Sonoran shelf and Tamaulipas Basin, Mexico

The Late Jurassic extensional Bisbee Basin in northwestern Mexico and southwestern United States lay between the Pacific magmatic arc and subduction zone and the cratonic Comanche shelf. Aptian to late Albian fluvial, deltaic, and shallow marine sediments and patch reefs of the Bisbee Group filled the basin. The upper Barremian(?)–lower Aptian Cerro de Oro Formation and its equivalent Rancho La Colgada Formation are overlain by the Morita, Mural, Cintura, and La Juana formations. The paralic Morita Formation and the marine Mural Limestone grade southeast into the marine Agua Salada and Lampazos formations, which correlate with deep-water facies in the Chihuahua trough and Tamaulipas Basin. Three late Aptian to middle Albian long-term depositional cycles were approximately 2.5 myr in duration.Foraminifers, calcareous algae, bivalves, rudists, corals, dinoflagellates and scarce ammonites compose the Mural Limestone biostratigraphy. First-occurrence datums of Aptian–Albian benthic Foraminifera are integrated with planktonic Foraminifera and rudists and define biostratigraphic zones that correlate with the Comanche shelf. In the Chihuahua trough and Tamaulipas Basin planktonic Foraminifera and nannofossils identify global zones. Stage boundaries on the Sonora shelf are correlated by a comprehensive biostratigraphic database.Carbon isotope chemozones correlate with Tethyan chemostratigraphy. The lower Aptian OAE 1a and uppermost Aptian–lowest Albian OAE1b chemozone are in the Lampazos section. The negative δ13C excursions and fossil evidence correlate with global Jacob, Kilian, Paquier, and Leenhardt levels. Low-oxygen water masses flooded the shallow shelf and even affected coral-rudist buildups.

Sedimentation Rate During Miocene to Pleistocene Related with Nannofossil Biostratigraphy, in Banyuurip, Kedewan, Rembang Zone, East Java Basin, Indonesia

The researched area is located in Rembang Zone, North East Java Basin. The Rembang Zone is one of the largest basins in Indonesia. In this area, there are many oil wells that today are still actively producing. The research concerning the content of microfossils in marine sedimentary outcrops is needed to determine the rate of sedimentation in a basin. The method is basically based on the result of stratigraphic measurements of two sections with a distance of 2,743.7 m. Sedimentation rate is the average thickness ratio to the average time interval. The sections have a good outcrop and a continuous stratigraphic sequence from Miocene (Wonocolo, Ledok, and Mundu Formations) to Pleistocene (Lidah Formation). Samples taken in the section consisted of fourty-one samples of marls and shales. The results of the analysis show eighteen genera with fifty-seven species of nannoplankton. While the resulting biostratigraphic zone can be arranged into eleven zones consisted of two partial, one range and eight interval zones. The development of sedimentation rate (RoS) of studied area consists of ten periods, those are (1) CNM15 Zone/ Late Miocene of Ledok Formation at a depth of 427.8 - 322.4 m, and has a sedimentation rate (RoS) of 11.46 cm/ ky, (2) CNM16-CNM20 Zone/Late Miocene to Early Pliocene, Ledok Formation at a depth of 322.4 - 279.3 m and has a RoS of 1.54 cm/ky, (3) Mundu Formation is CNPL2 Zone/Early Pliocene at a depth of 279.3 - 223 m and has a RoS of 5.41 cm/ky, (4) CNPL3 (Early Pliocene) Zone at a depth of 223 - 148.4 m and has a RoS of 33.91 cm/ky, (5) CNPL4 Zone (Middle Pliocene) at a depth of 148.4 - 82.7 m and has a RoS of 5.09 cm/ky. (6) Zone of CNPL5 (Middle-Late Pliocene) at a depth of 82.70 - 53.1 m and has a RoS of 21.14 cm/ky, (7) CNPL6 Zone/Late Pliocene at a depth of 53.1 - 52.0 m and has a RoS of 0.24 cm/ky, 8). CNPL7 Zone/Late Pliocene to Early Pleistocene at a depth of 52.0 - 33.8 m and has a RoS 8.27 cm/ky, (9). CNPL8 Zone (Early Pleistocene) at a depth of 33.8 - 26.4 m and has a RoS of 1.14 cm/ky, (10) CNPL9 Zone? (Early Pleistocene) at a depth of 26.4 - 12.5 m and has a RoS of 1.7 cm/ky. The relatively faster sedimentation rate of the CNPL3 is due to the faster subsidence and maximum sediment supply. During the development of sedimentation rate, there are two unconformities, namely (1) after the CNM20 Zone resulting in a sedimentation interval during CNPL1 and (2) after CNPL6 (Late Pliocene). Keywords: sedimentation rate, biostratigraphy, Rembang Zone, Banyuurip

Brachiopods from the Lower Permian of the Khospokhchon Section in the Southern Verkhoyanie (Northeast Russia)

A biostratigraphic division of the Lower Permian into brachiopod zones of Jakutoproductus verkhoyanicus, Jakutoproductus insignis, Jakutoproductus terechovi, and Jakutoproductus rugosus is observed within the Northern and Western Verkhoyanie. According to the literature, only the complex of the lower biostratigraphic unit (Verkhoyanicus Zone) was previously confidently established in the Southern Verkhoyanie. Meanwhile, representatives of the two middle zones were not observed, and the presence of the index species of the Rugosus zone was only indicated in the southern part of the region (Yudoma River Basin). A monographic study of the brachiopod collection from the Upper Olchan Subformation of the stratotype of the Olchan Formation (Khospohchon section) allowed us to rethink the biostratigraphic division of the Asselian-Sakmarian deposits in the Southern Verkhoyanie. The brachiopods of the Upper Olchan Subformation of the Khospohchon Creek (Menkule River Basin) belong to three successive biostratigraphic zones: Verkhoyanicus, Insignis, and Terechovi. Information on the presence of representatives of the species Jakutoproductus rugosus Ganelin in the Southern Verkhoyanie leads to the assumption that all four biostratigraphic zones of the Asselian-Sakmarian deposits of Verkhoyanie are present in this region. Three upper zones (Insignis, Terechovi, and Rugosus) demonstrated a direct correlation with the Ogonerian Regional Stage of the Omolon massif by their common zonal species. The new results indicate the need for a comprehensive study of the key sections of the Olchan Formation to substantiate the Carboniferous-Permian and Asselian-Sakmarian boundaries in Verkhoyanie using both biostratigraphic and chemostratigraphic methods.

Semantic Mapping of the Geologic Time Scale: A temporal reference

The Geologic Time Scale is an ordered hierarchical set of terms representing specific time intervals in Earth's history. The hierarchical structure is correlated to the geologic record and major geologic events in Earth’s history (Gradstein et al. 2020). In the absence of quantitative numeric age values from absolute dating methods, the relative time intervals in the geologic time scale provide us with the vocabulary needed for deciphering Earth’s history and chronological reconstruction. This temporal frame of reference is critical to establishing correlations between specimens and how they fit within the Earth’s 4.567 Ga (giga annum) history. Due to spatial and temporal variations in the stratigraphic record, the terminology used in conjunction with geologic time scales is largely inconsistent. For a detailed discussion regarding term use in geologic timescales, see Cohen et al. (2013). As a result, published values for geologic timescale terms are often ambiguous and highly variable, limiting interoperability and hindering temporal correlations among specimens. A solution is to map verbatim geologic timescale values to a controlled vocabulary, constructing a single temporal frame of reference. The harmonization process is governed by an established set of business rules that can ultimately become fully or partially automated. In this study, we examined the Global Biodiversity Information Facility’s (GBIF) published distinct verbatim values for Darwin Core terms in the GeologicalContext Class of Darwin Core to assess the the use of chronostratiphic terms, a process highlighted in Sahdev et al. (2017). Preservation of these verbatim values, the initial unmapped set of published values, is important. Many are derived directly from primary source material and possess special historical and regional significance. These include land mammal ages (e.g., Lindsay (2003)), biostratigraphic zones, regional terms, and terms with higher granularity than the International Commission of Stratigraphy’s (ICS) timescale allows (e.g., subages/substages). For the purposes of this study, we selected the 2023/6 version of the ICS chronostratigraphic timescale as the controlled vocabulary (Cohen et al. 2023). The ICS is the most widely adopted timescale, comprising the most generalized and universally applicable intervals of geologic time. After semantic analysis of the verbatim values (see Table 1 for comparative statistics), we established a comprehensive set of business rules to map to the ICS timescale controlled vocabulary. This process yielded a collection of documented procedures to transform the heterogeneous collection of published terms into a semantically consistent dataset. The end result is a single temporal frame of reference for published geologic and paleontological specimens through semantic mapping to improve the temporal correlations between geologic specimens globally through data interoperability. This talk will highlight the process of harmonizing a heterogeneous collection of published verbatim Geologic Time Scale values with an established controlled vocabulary through semantic mapping.

Integrated biochemostratigraphy of the Permian-Triassic boundary interval and Lower Triassic succession in the eastern Cimmerian continent (Baoshan block, West Yunnan, southwest China)

The records of extreme biotic and environmental crises have been well documented worldwide from Permian-Triassic successions. However, the Cimmerian continent, a Gondwana-derived continental terrane/block strip, has received insufficient attention in terms of its eastern part including the Baoshan block. Here, we report an integrated conodont biostratigraphic zonation and carbon isotope profile from the Permian-Triassic boundary (PTB) beds and Lower Triassic succession of the Baoshan block. The conodont faunas obtained from the dolomitized Hewanjie Formation at the Dajianshan section are dominated by Hindeodus and Isarcicella species. Representatives of Eurygnathodus and the Ellisoniidae are also present. Five conodont zones are recognized in ascending order: the Hindeodus parvus Zone, the Isarcicella staeschei Zone, the Isarcicella isarcica Zone, the Hindeodus postparvus Zone, and the Eurygnathodus costatus Zone. The carbon isotope curve exhibits two pulses of negative excursion around the PTB. In general, both the conodont zones and the carbon isotope profile correlate well with those from other well-documented sections in the world. The Permian-Triassic boundary, extinction horizons and Induan-Olenekian boundary are calibrated in terms of conodont and carbon isotopic data. In addition, conodont biofacies analyses show that the depositional water-depth was shallow in general, as indicated by the lack of gondolellids and neospathodids and the presence of ellisonids and Eurygnathodus.

FIRST EVIDENCE FOR THE PRESENCE OF THE UPPER CARBONIFEROUS DEPOSITS ON THE TUORA-SIS UPLIFT OF THE LOWER REACHES OF THE LENA RIVER, NORTHEAST RUSSIA

A vertical sequence of brachiopods was revealed at the base of the Verkhoyanian terrigenous complex of the Tit-Ary section in the northern part of the Tuorasis uplift of the lower reaches of the Lena River. As a result of the study of these brachiopods, it was established that in the indicated section, the Upper Cambrian dolomites are overlain by Gzhelian and Asselian deposits, characterized by brachiopods of the Jakutoproductus protoverkhoyanicus and Jakutoproductus verkhoyanicus biostratigraphic zones. This is the first proven fact of the presence of Upper Carboniferous deposits in the area. It is concluded that within the Tuorasis uplift from south to north, the upper age limit of the unconformity between the Cambrian and the Upper Paleozoic is growing older, while the base of the Verkhoyanian terrigenous complex is built up by the Permian basal beds and the Gzhelian deposits of the Upper Pennsylvanian. The Tit-Ary section is the first of those established in the lower reaches of the Lena River, with exposed boundary Carboniferous-Permian beds.

Latest Oligocene to middle Miocene low-latitude calcareous nannofossil biostratigraphy and paleoenvironmental interpretations of stratigraphic well 4, Sinú-San Jacinto onshore basin, northwest Colombia

Calcareous nannofossils are one of the main fossil groups used in the petroleum industry to determine the relative age and correlation of lithofacies identified in gas and oil wells. A limited number of biostratigraphic zonation schemes based on nanoplankton and paleoceanographic reconstructions have been suggested to onshore Colombian Caribbean. Most of them are compiled in several publications for the northern Colombian units (Mejía-Molina et al., 2008, 2010). In this study, a medium to high-resolution biostratigraphy study was carried out on one of the best-known Neogene sedimentary successions in the Sinú-San Jacinto onshore Basin, where the Stratigraphic Well 4 (SW4) was drilled by Ecopetrol, the Colombian state-run oil company. The nannoplankton biostratigraphic zonation proposed here constitutes the first calcareous nanoplankton research to construct a biochronologic scheme for the Neogene of northern Colombia, which has direct applications for oil exploration, global energy matrix and the transition to clean energy in the onshore areas of the Sinú-San Jacinto domain. The section studied has a thickness of ∼269 m and comprises mainly a very thick succession of claystone and mudstone with occasional intercalations of silty sandstones corresponding to the El Carmen Formation. The studied interval is assigned to the nannofossils Zones NP25 (CP19) to NN4 (CN3) of Martini (1971) and Okada and Bukry (1980), spanning from the latest Oligocene (latest Chattian) to middle Miocene (early Langhian), approximately 24 Ma to 15 Ma. Intervals without fossil content were identified in the record and could constitute hiatuses, but the nannofloral events, which define the limits of the biozones, can be identified. Global and regional climatic changes which occurred in the Caribbean region at those times are reflected in important changes in the fossil assemblages and abundance pattern of nanoplankton. These could indicate variability in environmental conditions linked to temperature and increased nutrients within the nannofossil communities in this part of the San Jacinto folded belt (SJFB), northwest Colombia. Middle Miocene Climate Optimum (MMCO) episodes of “blooming” intervals of Sphenolithus were identified, accompanied with a drastic reduction in total nannofossil abundance and CaCO3 content. Since the Caribbean geology is framed in a very complex scenario, the data acquired and presented in this research has a potential application to improve the current stratigraphy in the area, targeted to hydrocarbon exploration and studies related to the global energy matrix and the transition to clean energy. It also strengthens the paleoceanographic reconstructions based on these organisms at low latitudes.

Nannofossil Biostratigraphy of Elat Formation, Kei Besar Island, Southeast Maluku

The first detailed mapping and recording of nannofossils was carried out on Kei Besar Island, Southeast Maluku. This area is mostly composed of the Elat Formation, which is mainly composed by intercalated calcarenite and calcareous claystone. Total 48 samples were taken on three measured sections (Hollat, Ngurdu and Mata Hollat). Samples were prepared using smear slide method, then observed under a polarized microscope at 1000 x magnification. Total 48 species of nannofossils were identified. Several index species were selected to define biostratigraphic zones based on their first and last occurrence. Three zones of nannofossils are identified, starting with the oldest those are: Reticulofenestra umbilica zone (NP16; 43.06 to 38.7 million years ago), Helicosphaera compacta zone (NP17; 38.7 to 37.9 Mya) and Helicosphaera eupratis zone (NP18-NP19; 37.9-36.8 Mya). It can be concluded that Elat Formation is deposited in Middle to Late Eocene (43.06 to 35.4 Mya). The Middle-Late Eocene boundary can be clearly defined based on nannofossils assemblages in the section of the Kei Besar Island.

A bio-chronostratigraphic study of the upper Miocene from the northern Caltanissetta Basin, Sicily (core 3AGN2S04). Implications for dating the Messinian Salinity Crisis onset

The late Miocene deposits from core 3AGN2S04, located in the northern Caltanissetta Basin (Sicily), display the pre-Messinian Salinity Crisis (MSC) and the MSC events. The present study describes the entire core in terms of lithology, biostratigraphy and magnetostratigraphy and aims to enlighten the relationship between MSC evaporite cyclicity and astronomical forcing. The lithological and micro−/macro-paleontological descriptions document the MSC record, with Stage 1 (onset and Calcare di Base member), Stage 2 (Messinian Erosional Surface) and part of Stage 3 (Upper Gypsum and Lago Mare). Detailed micro-fossil analyses of the pre-evaporites reveal several biostratigraphic events that permit correlations to the well-dated Mediterranean planktonic foraminiferal biostratigraphic zonation of the late Tortonian and Messinian. An integrated bio-cyclostratigraphic analysis allows bed-to-bed correlations of core 3AGN2S04 with the reference sections of Falconara/Gibliscemi (Sicily) and Sorbas (Spain), but also with various other sections from the Caltanissetta Basin. Our cyclostratigraphic correlations show a stratigraphical gap in the core between the late Tortonian Terravecchia Formation and the pre-evaporitic Messinian Tripoli Formation. This hiatus is probably related to the tectonically active geological setting of the northern Caltanissetta Basin. Finally, we show that the repercussions of the paleoenvironmental evolution towards evaporitic deposition and the MSC onset seem to have been diachronous throughout the various perched basins on Sicily characterized by different paleobathymetries. In particular, the onset of the Calcare di Base took place around 40–100 ka before the deposition of the first gypsum bed of the Primary Lower Gypsum units.

Calcareous nannofossils from the Poggio le Guaine core (Umbria-Marche Basin, central Italy): Biostratigraphy and discussions on the bioevents of the Aptian–Albian interval

The calcareous nannofossil biostratigraphy of the Aptian–Albian interval has been continuously applied and developed along the last decades. The shortage of complete and continuous outcropping marine sections and even marine subsurface sections is one of the challenges of the stratigraphic studies of this interval. Taxonomic ambiguities, diachronism and reworking are constantly pointed as challenging aspects for the calcareous nannofossil biostratigraphic studies of this interval. Amid this scenario, the Poggio le Guaine section of the Umbria-Marche Basin (central Italy) stands out by presenting a complete and undisturbed pelagic to hemipelagic marine sedimentary succession of the Aptian–Albian interval. The present work is aimed to provide a detailed biostratigraphic zonation based on calcareous nannofossils, to calibrate the results to other stratigraphic tools of previous published works and to discuss some important bioevents of the Aptian–Albian interval along the PLG core. The following biozones of the calcareous nannofossil reference zonation for the Aptian–Albian interval were recognized: the Chiastozygus litterarius Zone (NC6 Zone), the Rhagodiscus angustus Zone (NC7 Zone), the Prediscosphaera columnata Zone (NC8∗ and NC8 zones), the Axopodorhabdus albianus Zone (NC9 Zone) and the Eiffellithus turriseiffelii Zone (NC10 Zone). The PLG core encompasses the chronostratigraphic interval from the Barremian/Aptian through the Albian/Cenomanian boundaries. Finally, detailed discussions on some important calcareous nannofossil bioevents of this interval were performed, among them: the first occurrence (FO) of Hayesites irregularis, the FO of Hayesites albiensis, the last occurrence (LO) of Conusphaera rothii, the LO of Micrantholithus hoschulzii/Micrantholithus obtusus, the FO of Rhagodiscus achlyostaurion, the FO of Prediscosphaera columnata, the FO of Tranolithus orionatus and the LOs of Assipetra spp.

Middle–Late Pennsylvanian tectonosedimentary, climatic and biotic records in basins of Europe, NW Turkey and North Africa: an overview

Abstract In Europe, North Africa and Asia Minor, the remains of Pennsylvanian sedimentary basins bearing continental deposits either intimately mixed with shallow-marine strata or deposited in exclusively continental settings are preserved. Long-lasting research on these basins allowed the definition of regional stages and substages based on marine fauna and terrestrial flora, later extended by terrestrial and freshwater faunal biostratigraphies. Glacioeustatically driven marine bands provide laterally widespread correlation markers; however, where such bands are missing only biostratigraphic control exists. Resolution of biostratigraphic zonations combined with gaps in sedimentary successions and variable quality of the fossil record throughout the basin fills do not allow in all cases a precise correlation between the Pennsylvanian basins in Europe and, in turn, the timing of tectonic, climatic and biotic events, and thus an absolute complete understanding of the response of terrestrial and freshwater biota to climate changes across eastern tropical Pangaea. A helpful tool is new radioisotopic ages of intercalated volcaniclastics that reveal the partial diachroneity of some widely used biostratigraphies. We attempt to present the current state of the art to stimulate further research to mitigate gaps in our knowledge.