Micula Prinsii Research Articles

Calcareous Nannofossils Biostratigraphy of Late Cretaceous–Paleocene Successions from Northern Jordan and Their Implications for Basin Analysis

Local geological and tectonic processes have been pivotal in shaping the diverse sedimentation patterns observed in Jordan, forming sub-basins characterized by elevated organic matter content (TOC). This study aims to characterize the Maastrichtian basin, focusing on sedimentation rates using calcareous nannofossils and understanding paleoecological and paleo-oceanic conditions. It offers insights into the paleoenvironmental factors impacting oil shale deposition in the late Maastrichtian–Paleocene period. It employs classical biostratigraphical, semi-quantitative, and statistical methodologies to achieve its objectives of age determination and paleoecological insights. A total of 116 smear slides from two sites were obtained: the first, consisting of WA-1 (23 samples), WA-2 (18 samples), and WA-3 (11 samples), and the second, with 60 samples. Notably, the sites exhibit varying topography. WA-1 and WA-2, situated at lower elevations, have the highest Total Organic Carbon (TOC) levels, while areas with higher elevations in section four are visually identified by a light color. The study revealed varying patterns of calcareous nannofossil richness in the two investigated sites. These patterns were instrumental in defining biozones, with the utilization of marker species such as Lithraphidites quadratus, Micula murus, Micula prinsii, and Cruciplacolithus tenuis. Chronologically, these sections were classified as Maastrichtian–Paleogene, encompassing the following biozones in sequential order: UC-20a, UC-20b, UC-20c, UC-20d, and NP-2. Furthermore, the study identified two hiatus intervals, observed in sections WA-1 and KAS-1. The absence of certain biozones in the analyzed sections suggests that these sections correspond to distinct geological blocks within the basin, underscoring the role of tectonic forces during the deposition period. The sedimentation rate initially commenced at low levels but gradually increased due to topographic alterations. Notably, the biozone UC-20c demonstrated a clear trend toward warming and enhanced nutrient availability. In this context, the abundance and diversity of species were associated with increased continental influx into the sub-basin, resulting in rising nutrient levels and the number of calcareous nannofossils. This study enhances the understanding of the local and global effects such as tectonic and climates of the continuity of basins by deciphering calcareous nannofossil patterns and their correlation with sedimentation factors.

A new elasmosaurid (Sauropterygia, Plesiosauria) from the upper levels of the La Colonia Formation (upper Maastrichtian), Chubut Province, Argentina

A new elasmosaurid, Chubutinectes carmeloi gen. et sp. nov., from the Chubut Province, Argentina, is described. The holotype and only specimen of this species (MPEF-PV 5232) was collected from the La Colonia Formation. Chubutinectes carmeloi gen. et sp. nov. is among the few upper Maastrichtian elasmosaurids from the Southern Hemisphere whose postcranial anatomy is well known. It can be distinguished from other elasmosaurids by the following combination of characters: middle cervical centra longer than high with lateral keel and bilobate articular faces; pectoral and anterior dorsal centra with bilobate articular faces; coracoids with closed cordiform fenestra and long anterior coracoids process; high ratio coracoids/scapular length; ilium with angled shaft; pubis with small lateral cornua; humerus with posterior expansion ending in accessory facet and epipodial facets of humerus almost aligned; accessory ossification between tibia and tibial, and radius and radial. Preliminary phylogenetic analysis recovered Chubutinectes carmeloi gen. et sp. nov. within the Weddellonectia clade, including the Late Cretaceous Wedellian aristonectine elasmosaurids. The study of the associated microfossiliferous assemblages (micro- and nanofossils) suggests a marine inner neritic paleoenvironment, with restricted circulation and warm waters. The presence of Micula prinsii and Micula murus at this latitude indicates a latest Maastrichtian age, upper part of the UC20d sub-biozone and younger than ∼67,3 Ma.

Early Maastrichtian-Early Eocene Biostratigraphy of El Hasana Area, Central Sinai, Egypt

ABSTRACT Ten calcareous nannofossils and ten planktic foraminiferal biozones were recognized from two sections measured in El Hasana area, in Central Sinai, Egypt. In the West El Hasana section, an early Maastrichtian/early Paleocene (K/Pg) unconformity was recorded due to the absence of the planktic foraminiferal Gansserina gansseri, Abathomphalus mayaroensis, and Globigerina eugubina Zones and the calcareous nannoplankton Micula prinsii and Markalius inversus Zones. The early Paleocene is represented by two biozones, Morozovella pseudobulloides (P1b) and Morozovella trinidadensis (P1c) that correlate with the Cruciplacolithus tenuis Zone (NP2), Chiasmolithus danicus Zone (NP3), and Ellipsolithus macellus Zone (NP4). In both sections, during the middle Paleocene three biozones were recorded: Morozovella uncinata (P2), the lower part of P3 Morozovella angulata, and Planorotalites pusilla pusilla (upper part of P3). The first and second biozones are equated with the upper two thirds of Ellipsolithus macellus (NP4), while the third one is correlated with Fasciculithus tympaniformis Zone (NP5). In the West El Hasana section, the Planorotalites pseudomenardii Zone (P4) ends the measured section. A small hiatus was observed across the late Paleocene/early Eocene (P/E) boundary in the East El Hasana section. This hiatus is due to the absence of the Planorotalites pseudomenardii Zone (P4), Morozovella velascoensis Zone (P5), M. edgari Zone (lower part of P6) and Heliolithus kleinpellii Zone (NP6), Discoaster molheri Zone (NP7), Heliolithus riedelli/Discoaster nobilis Zone (NP8), and Discoaster spp. (e.g., D. araneus) Subzone NP9a. The P/E boundary in East El Hasana section is delineated with the appearance of Rhomboaster spp. (e.g., Rhomboaster bitrifida) NP9b Subzone that coincides with the appearance of the planktic foraminiferal Morozovella subbotinae Zone (upper part of P6).

Maastrichtian climate changes – the calcareous nannofossil record from flysch deposits of the Outer Carpathians

The Outer Carpathians are known for a few sections, where transitions from the Upper Cretaceous to the Palaeogene, including the K-Pg boundary interval, were described. One of them, the Bąkowiec section in the Skole Nappe, was examined with reference to the record of biostratigraphy and palaeoenvironmental changes, mainly based on the analysis of calcareous nannofossil assemblages. This study shows no evidence for the K-Pg boundary; however, the presence of the nannofossil species Micula prinsii , marking the topmost Maastrichtian UC20dTP Zone, was noted. The appearance of this low-latitude taxon and relevant changes in the composition of nannofossil assemblages indicate an influx of Tethyan warm water into the northern Carpathian basins during the latest Maastrichtian, shortly before the K-Pg boundary event. Therefore, the authors infer that the upper part of the Bąkowiec section recorded the latest Maastrichtian warming of climate, probably triggered by Deccan volcanic activity.

Latest Maastrichtian palaeoclimatic and depositional environmental perturbations, a record from Micula prinsii Zone of Meghalaya, northeastern India

A significant latest Maastrichtian calcareous nannofossil assemblage is recorded from the exposed section near Syndai Village, Meghalaya. A total of twenty two samples from sedimentary succession consisting of shales and sandy shales, calcareous at places, were studied; out of which ten samples were found productive in terms of calcareous nannofossils recovery. The presence of Micula prinsii in all the productive samples along with the other latest Maastrichtian nanno taxa suggests that the assemblage belongs to Micula prinsii Zone and well correlates with the CC26b Zone of Perch Nielsen and UC20dTP Zone of Burnett which are an amalgamation of old and new biozonation schemes from a range of palaeolatitudes and biogeographic provinces from both oceanic and shelf palaeoenvironments. Micula prinsii Perch–Nielsen, the latest Maastrichtian marker all over the globe, is recorded from both deep–sea sections and shelf areas. It is most evolved form of the genus Micula and got extinct just before K– Pg boundary. The Micula prinsii Zone is marked by the first occurrence of Micula prinsii to the last occurrence of unreworked, non–survivor Cretaceous taxa. In the present study, cluster analysis envisaged the palaeodepositional environmental changes within the Micula prinsii Zone in northeastern India. In the lower part of the section, the abundance of Micula concava and Micula staurophora with the increased numbers of Watznaueria barnesiae indicates environmentally stressful conditions with low productivity in surface water. However, in the upper part the increased numbers of Calculites obscurus with the decrease in Micula concava and Micula staurophora abundance indicates relatively increased productivity in surface water in marginal marine depositional environment.

Calcareous Nannofossil Biostratigraphy of the Paleocene-Lower Eocene Successions in the Farafra Oasis, Western Desert, Egypt

This work deals with a high-resolution analysis of calcareous nannofossil in four exposed Paleocene-Lower Eocene successions in the Farafra Oasis, Western Desert, Egypt in order to detect the different types of stage boundaries and hiatuses. The studied four sections were collected from five localities (Gebel North Gunna, Gebel South Gunna, Ain Ramla, El-Quss Abu Said and Bir Karawin). In the study area, the Paleocene-Lower Eocene succession is made up of four formations, namely Dakhla (at base), Tarawan, Esna and Farafra (at top) that unconformably overlie the Maastrichtian Khoman Formation. The oldest Paleocene calcareous nannofossil Zone (NP 4) is recorded in the Dakhla Formation. It unconformably overlies the latest Maastrichtian Micula prinsii (CC 26b) subzone that is recognized in the uppermost part of the Khoman Formation at North Gunna section. Although Zone NP 4 is successively overlain by the Paleocene-Lower Eocene calcareous nannofossil zones NP 5, NP 6, NP 7/8, NP 9a, NP 9b, NP 10a. These zones are not sequentially recorded in all the studied sections.The Danian/Selandian boundary is traced in the uppermost part of Zone NP 4 at North Gunna and South Gunna sections. At this boundary, a minor hiatus is observed. This is in consistence with the global drop in relative sea level during the Late Danian. A pronounced hiatus is founded slightly after the base of Selandian to the base of the Thanetian at North Gunna and South Gunna sections. In contrast, in the western part of the studied area at Ain Ramla-ElQuss Abu Said section, a conformable relation is recorded at the Selandian/Thanetian boundary where the uppermost part of Zone NP 4 is directly followed by Zones NP 5, NP 6 and NP 7/8. A hiatus between the Paleocene and the Eocene (Thanetian/Ypresian boundary) is observed in the lower part of the Esna Formation at North Gunna section. The nature of the Paleocene/Eocene boundary is not recognized in Ain Ramla-ElQuss Abu Said and South Gunna sections because they are described as composite sections. However, the Ypresian NP 9b subzone is recorded at the base of South Gunna section. Subzone NP 10a is recorded in all the studied sections, which may a response to a relative sea level rise during the Early Eocene time.

Comment on “Extinction, dissolution, and possible ocean acidification prior to the Cretaceous/Paleogene (K/Pg) boundary in the tropical Pacific”

Criticism of the age-model used by Dameron et al. (in press) is commented hereby. This criticism essentially concerns the age of the first occurrence of calcareous nannofossil Micula prinsii at Shatsky Rise, central Pacific, which should not be considered older than 66.6Ma, rather than 67.3Ma as considered by the authors. Although this criticism does not fundamentally change the environmental and paleoceanographic interpretations of Dameron et al. (in press), the age of this bioevent influences quite a lot the time scale used for the latest Maastrichtian and thus the actual age of the termination of their main dissolution interval and the duration of the partial recovery in carbonate preservation. We recommend the authors to modify their age-model and to provide alternative durations and ages for the sequence of events in the end-Maastrichtian interval as such revised ages constitute an important base for comparison with the timescale of Deccan volcanism and other end-Cretaceous perturbations.

Calcareous nannofossil biostratigraphy of the uppermost Maastrichtian–lower Paleocene at the Misheiti section, East Central Sinai, Egypt

Calcareous nannofossil data, δ13C and δ18O values, and carbonate contents of the uppermost Maastrichtian–lower Paleocene succession cropping out at the Misheiti section (East Central Sinai, Egypt) have been used to denote and reveal the changes across the Cretaceous/Paleogene (K/Pg) boundary. The study interval belongs to the uppermost Sudr Formation and the Dakhla Formation. Four calcareous nannofossil zones (Micula prinsii, NP1, NP2/3, and NP4) were recognized. The δ13C profile and the carbonate content show significant decreases across the K/Pg boundary. A hiatus at the K/Pg boundary is indicated by the absence of the basal part of Zone NP1. Geochemical results and calcareous nannofossil assemblages reflect fluctuations of the paleotemperature during the latest Maastrichtian–early Paleocene.

Upper Maastrichtian ammonite biostratigraphy of the Gulf Coastal Plain (Mississippi Embayment, southern USA)

The Cretaceous outcrop belt of the Mississippi Embayment in the Gulf Coastal Plain (GCP) spans the Cretaceous/Paleogene (K/Pg) boundary. A detailed reconstruction of this time interval is critical for understanding the nature of biotic and environmental changes preceding the end-Cretaceous Mass Extinction event and for deciphering the likely extinction mechanism (i.e., bolide impact versus volcanism). Eight sections encompassing the K/Pg succession across the Mississippi Embayment were analyzed using biostratigraphic sampling of ammonites, dinoflagellates, and nannofossils. An upper Maastrichtian ammonite zonation is proposed as follows, from oldest to youngest: Discoscaphites conradi Zone, D. minardi Zone, and D. iris Zone. Our study documents that the ammonite zonation established in the Atlantic Coastal Plain (ACP) extends to the GCP. This zonation is integrated with nannofossil and dinoflagellate biostratigraphy to provide a framework to more accurately determine the age relationships in this region. We demonstrate that ammonites and dinoflagellates are more reliable stratigraphic indicators in this area than nannofossils because age-diagnostic nannofossils are not consistently present within the upper Maastrichtian in the GCP. This biostratigraphic framework has the potential to become a useful tool for correlation of strata both within the GCP and between the GCP, Western Interior, and ACP. The presence of the uppermost Maastrichtian ammonite D. iris, calcareous nannofossil Micula prinsii, and dinoflagellates Palynodinium grallator and Disphaerogena carposphaeropsis suggests that the K/Pg succession in the GCP is nearly complete. Consequently, the GCP is an excellent setting for investigating fine scale temporal changes across the K/Pg boundary and ultimately elucidating the mechanisms causing extinction.

Calcareous nannofossil biostratigraphy and paleoecology of the Maastrichtian in the western coast of the Gulf of Suez, Egypt

Calcareous nannofossil content of the Maastrichtian succession at the western coast of the Gulf of Suez in Egypt has been studied. This study aims to contribute in the understanding of high-resolution biostratigraphy and paleoecologic interpretations. Five biozones (Reinhardtites levis, Arkhangelskiella cymbiformis, Lithraphidites quadratus, Micula murus, and Micula prinsii) were distinguished. According to the paleoecologic parameters (cool-water, warm-water, productivity, preservation, and the ratio of Micula decussata/Watznaueria barnesae), the studied succession is subdivided into five ecozones. The environment of each ecozone is deduced; M. Prinsii, M. murus, and L. quadratus ecozones are characterized by a cooler climate, but R. levis and A. cymbiformis ecozones are characterized by a warmer climate.

Study of nannoliths from upper Cretaceous Shiranish Formation, Higran area, Northern Iraq

Sixteen exposed samples from the upper Cretaceous Shiranish Formation have been studied from the southern limb of Safin anticline (36° 21′ 22″ N, 44° 15′ 24″ E), SW Shaqlawa City (near Higran Village), northern Iraq; the studied section consists of well-bedded blue marly limestone. A detailed investigation was carried out to identify nannoliths belonging to calcareous nannofossils in which 11 species were described from other regions; these were Lithraphidites grossopectinatus Butkry (1969), Microrhabdulus attenuatus (Deflandre, 1959) Deflandre (1963), Microrhabdulus decoratus Deflandre (1959), Micula decussata Vekshina (1959), Micula murus (Martini, 1961) Bukry (1973), Micula prinsii Perch-Nielsen (1979), Micula staurophora (Gardet, 1955) Stradner (1963), Micula swastica Stradner and Steinmetz (1984), Ceratolithoides aculeus Stradner (1961), Ceratolithoides arcuatus Prins and Sissingh in Sissingh (1977), and Ceratolithoides verbeeki Perch-Nielsen (1979). The name of the index species indicates that the top of Shiranish Formation in the studied section is of Latest Maastrichtian, and the range of C. arcuatus is used for the definition of subbiozone CC21b in the Campanian, but here, we found it from the Late Maastrichtian.

Nannostratigraphy, nannofossil events, and paleoclimate fluctuations in the lower boundary of Kalat formation in East Kopet Dagh (NE Iran)

The biostratigraphy and the response of calcareous nannofossils to the End Cretaceous warming are investigated in the lower boundary of Kalat formation through the record of species richness, diversity, distribution patterns, and statistical treatments. The Kalat formation comprised of coarse-grained detritus limestone with subordinate sandstone intercalations. In the studied sections, the number of ten samples were taken and prepared with smear slide. In Dobaradar, section 22 species; in Kalat, section 25 species; and in Chahchaheh, section 32 species have been determined. Based on nannoplanktons and as a result of biostratigraphic studies, the nannofossil standard zones (CC25–CC26) were identified in all of sections. According to these zones in all of sections, the age of the studied thickness is Late Maastrichtian–Late Late Maastrichtian. In these sections, the presence of Micula murus at the end of Neyzar formation and the presence of this species at the lower part of Kalat formation indicate that the investigated boundary is Late Maastrichtian in age. The paleoecological results point to warm climate. The presence of warm water indicators (M. murus and Micula prinsii) and the absence of cool water indicators (Ahmuellerella octoradiata, Kamptnerius magnificus, and Nephrolithus frequens) suggest warm surface water conditions in these areas. In the lower boundary of Kalat formation, base on Lithraphidites spp. and Watznaueria barnesae, lowered fertility condition with low productivity at the end of the Maastrichtian were suggested, and the studied area was deposited in shallow marine environment in relatively low latitude.

Calcareous Nannoplankton Biostratigraphy of the Bartin Province, Western Black Sea, Turkey

Abstract:Calcareous nannoplankton biostratigraphy has been performed on five sedimentary sections through the marine Akveren Formation from the Bartin region of northern Turkey, on the southern Black Sea coast. This new biostratigraphy provides an age for the formation of the Early Campanian (nannofossil zone UC15aTP) to Early Selandian (nannofossil zone NP5), and highlights the presence of the Campanian/Maastrichtian, Cretaceous/Tertiary (K/T), and Danian/Selandian boundaries in this intermediate palaeolatitude location. Micula murus was identified below the K/T boundary, but Micula prinsii and Nephrolithus frequens were not, which implies that the K/T boundary interval is not complete in the study area. These dates are in agreement with previous micropaleontological studies.

Upper Cretaceous to Lower Eocene calcareous nannofossil biostratigraphy from Malaqet and Mundassah sections western flank of the Northern Oman Mountains

This work is the first attempt to undertake a biostratigraphic study on calcareous nannofossil assemblages of the exposed Upper Cretaceous to Lower Eocene rocks at the Malaqet and Mundassah sections, NW Oman. The Upper Cretaceous to Lower Eocene rocks belong to the Simsima Formation and the Muthaymimah Formation. Specimens of calcareous nannofossils identified during this study have been ascribed to 67 different species. The Cretaceous/Palaeocene boundary can be placed in correspondence with the unconformity between the mentioned formations. The presence of a big hiatus in this area is suggested by the absence of the latest Maastrichtian Micula prinsii nannofossil Zone, and the Palaeocene NP1 and NP2 nannofossil Zones. In the two study sections, the Danian/Selandian boundary is placed at the level of the first occurrence (FO) of Fasciculithus tympaniformis (base of NP5 Zone).At Jabal Mundassah, the Selandian/Thanetian boundary is positioned at the FO of Discoaster mohleri, which is used to define the base of NP7/8 Zone. Unfortunately, a major hiatus is detected at the Selandian/Thanetian boundary at the Jabal Malaqet section as indicated by the absence of NP6 and NP7/8 Zones. The Paleocene/Eocene boundary is placed at the base of Subzone NP9b at Jabal Mundassah, whereas at Jabal Malaqet the Paleocene/Eocene boundary interval is missing and a major hiatus is testified by the absence of the NP9b Subzone and NP10 Zone. This work is the first attempt to undertake a biostratigraphic study on calcareous nannofossil assemblages of the exposed Upper Cretaceous to Lower Eocene rocks at the Malaqet and Mundassah sections, NW Oman. The Upper Cretaceous to Lower Eocene rocks belong to the Simsima Formation and the Muthaymimah Formation. Specimens of calcareous nannofossils identified during this study have been ascribed to 67 different species. The Cretaceous/Palaeocene boundary can be placed in correspondence with the unconformity between the mentioned formations. The presence of a big hiatus in this area is suggested by the absence of the latest Maastrichtian Micula prinsii nannofossil Zone, and the Palaeocene NP1 and NP2 nannofossil Zones. In the two study sections, the Danian/Selandian boundary is placed at the level of the first occurrence (FO) of Fasciculithus tympaniformis (base of NP5 Zone).At Jabal Mundassah, the Selandian/Thanetian boundary is positioned at the FO of Discoaster mohleri, which is used to define the base of NP7/8 Zone. Unfortunately, a major hiatus is detected at the Selandian/Thanetian boundary at the Jabal Malaqet section as indicated by the absence of NP6 and NP7/8 Zones. The Paleocene/Eocene boundary is placed at the base of Subzone NP9b at Jabal Mundassah, whereas at Jabal Malaqet the Paleocene/Eocene boundary interval is missing and a major hiatus is testified by the absence of the NP9b Subzone and NP10 Zone.

Deccan volcanism linked to the Cretaceous-Tertiary boundary mass extinction: New evidence from ONGC wells in the Krishna-Godavari Basin

A scientific challenge is to assess the role of Deccan volcanism in the Cretaceous-Tertiary boundary (KTB) mass extinction. Here we report on the stratigraphy and biologic effects of Deccan volcanism in eleven deep wells from the Krishna-Godavari (K-G) Basin, Andhra Pradesh, India. In these wells, two phases of Deccan volcanism record the world’s largest and longest lava mega-flows interbedded in marine sediments in the K-G Basin about 1500 km from the main Deccan volcanic province. The main phase-2 eruptions (∼80% of total Deccan Traps) began in C29r and ended at or near the KTB, an interval that spans planktic foraminiferal zones CF1–CF2 and most of the nannofossil Micula prinsii zone, and is correlative with the rapid global warming and subsequent cooling near the end of the Maastrichtian. The mass extinction began in phase-2 preceding the first of four mega-flows. Planktic foraminifera suffered a 50% drop in species richness. Survivors suffered another 50% drop after the first mega-flow, leaving just 7 to 8 survivor species. No recovery occurred between the next three mega-flows and the mass extinction was complete with the last phase-2 mega-flow at the KTB. The mass extinction was likely the consequence of rapid and massive volcanic CO2 and SO2 gas emissions, leading to high continental weathering rates, global warming, cooling, acid rains, ocean acidification and a carbon crisis in the marine environment.

Cretaceous evolution of the genus Adercotryma (Foraminifera) in the deep Pacific

Adercotryma glomeratum is one of the most geographically and bathymetrically widespread species of Recent deep-sea benthic foraminifera, but the evolutionary history of this distinct agglutinated species is poorly known. In addition to one or two Recent species probably closely related to A. glomeratum, the Eocene-Oligocene species Adercotryma agterbergi has been described, but we suggest that this species be assigned to the genus Ammogloborotalia. A very rare, unnamed species has been described from the Campanian in the western Pacific Ocean, and it has been speculated that the genus originated at about that time in the western Pacific, possibly from the ancestor Ammogloborotalia gyroidinaeformis. We describe the Maastrichtian occurrence of a previously unknown species, which we named Adercotryma kuhnti. This species occurs in the Maastrichtian Abathomphalus mayaroensis planktonic foraminiferal Zone, Micula prinsii nannofossil zone CC26, in the lower bathyal to abyssal ODP Site 1210 (ODP Leg 198, Shatsky Rise, northwest Pacific Ocean), where it constitutes up to 14.7% of the benthic foraminiferal assemblages. We looked for the species in coeval material from many locations in and around the Atlantic Ocean, and DSDP Site 465 in the Pacific (Hess Rise), but did not find it. The occurrence as a geographically restricted species agrees with speculation of a Cretaceous origin of the genus in the western Pacific, and evolution as a deep-sea species rather than migration from shallow waters.

MAASTRICHTIAN TO EOCENE CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY FROM THE TABIAGO SECTION, BRIANZA AREA, NORTHERN ITALY

Calcareous nannofossil biostratigraphic investigations have been carried out on samples collected from the Tabiago section, Brianza, northern Italy. This section records early Maastrichtian (CC23b nannofossil zone) to early Eocene (NP10 nannofossil zone) calcareous nannofossil assemblages. The Cretaceous-Tertiary transition is characterized by major changes in sedimentation rates and two likely stratigraphic gaps. The Cretaceous Brenno Formation was deposited with a high sedimentation rate (~20 m/m.y.), whilst the Tabiago Formation of Paleogene age records a drastic decrease (~10 m/m.y.). The absence of the CC26 zonal marker Micula prinsii may indicate a stratigraphic hiatus or an extremely condensed level in the latest Maastrichtian. However, only two samples have been collected and analyzed in this interval due to low exposure of the outcrop, and the absence of M. prinsii could be the result of diagenetic overprint or insufficient sampling. A stratigraphic hiatus or a very condensed interval corresponds to the upper part of NP1 nannofossil zone and PƒN foraminiferal Zone and P1a Subzone in the early Paleocene. The poor exposure of the outcrop prevents to precisely locate the zonal boundaries between NP4 and NP5 and between NP9 and NP10 and impedes the documentation of possible further stratigraphic gaps or condensed intervals.

Calcareous nannofossil biostratigraphy and paleoecology of the Cretaceous–Tertiary transition in the central eastern desert of Egypt

The Gebel Qreiya and nearby Wadi Hamama sections of the central Eastern Desert are among the most complete K/T boundary sequences known from Egypt. The two sections were analyzed spanning an interval from l.83 Myr below to about 3 Myr above the K/T boundary. A 1-cm-thick red clay layer at the K/T boundary at Gebel Qreiya contains an Ir anomaly of 5.4 ppb. The high-resolution study and well-preserved nannoflora provide good age control and the first quantitative records of calcareous nannofossil assemblages for paleoecological interpretations across the K/T transition in Egypt. Four zones ( Micula murus, Micula prinsii, NP1, and NP2) were distinguished and correlated with other nannofossil and planktonic foraminiferal zonations that are broadly applicable for the eastern Tethys region. Latest Maastrichtian assemblages are abundant and diverse, though Cretaceous species richness progressively decreased across the K/T boundary. Dominant species include Arkhangelskiella cymbiformis, Micula decussata and Watznaueria barnesae, with high abundance of dissolution-resistant M. decussata reflecting periods of high environmental stress. Thoracosphaera blooms mark the K/T boundary and are followed by an acme of the opportunistic survivor Braarudosphaera bigelowii, the first appearance of the new Tertiary species Cruciplacolithus primus, and an acme of Coccolithus cavus/ pelagicus. These successive abundance peaks provide the basis for subdivision of the Early Danian Zones NP1 and NP2 into five subzones. Correlation of selected nannofossil taxa from the Egyptian sections with those from various onshore marine and deep-sea sections provides insights into their paleoenvironmental and paleoecological affinities.

Age and paleoenvironment of the Maastrichtian to Paleocene of the Mahajanga Basin, Madagascar: a multidisciplinary approach

Lithology, geochemistry, stable isotopes and integrated high-resolution biostratigraphy of the Berivotra and Amboanio sections provide new insights into the age, faunal turnovers, climate, sea level and environmental changes of the Maastrichtian to early Paleocene of the Mahajanga Basin of Madagascar. In the Berivotra type area, the dinosaur-rich fluvial lowland sediments of the Anembalemba Member prevailed into the earliest Maastrichtian. These are overlain by marginal marine and near-shore clastics that deepen upwards to hemipelagic middle neritic marls by 69.6 Ma, accompanied by arid to seasonally cool temperate climates through the early and late Maastrichtian. An unconformity between the Berivotra Formation and Betsiboka limestone marks the K–T boundary, and juxtaposes early Danian (zone Plc? or Pld) and latest Maastrichtian (zones CF2–CF1, Micula prinsii) sediments. Seasonally humid warm climates began near the end of the Maastrichtian and prevailed into the early Danian, accompanied by increased volcanic activity. During the late Danian (zones P1d–P2), a change to seasonally arid climates was accompanied by deepening from middle to outer neritic depths.

Late Maastrichtian age of spherule deposits in northeastern Mexico: implication for Chicxulub scenario

In the La Sierrita area of Nuevo Leon, Mexico, three spherule layers are present and separated from the overlying siliciclastic deposits by up to 6 m of pelagic marls. The marls are of latest Maastrichtian age (Plummerita hantkeninoides (CF1) Zone, Micula prinsii Zone) and deposited under normal pelagic conditions with no significant evidence of reworking or slumping. Original deposition of the spherule layers occurred during the last 300 ka of the Maastrichtian and well prior to the Cretaceous-Tertiary (K–T) boundary event. Thus, if the spherules in northeastern Mexico provide critical evidence of an impact at Chicxulub, this impact predates the K–T boundary.