Planktonic Biostratigraphy Research Articles

THE MIDDLE EOCENE CLIMATIC OPTIMUM (MECO) IMPACT ON THE BENTHIC AND PLANKTIC FORAMINIFERAL RESILIENCE FROM A SHALLOW-WATER SEDIMENTARY RECORD

We present here new quantitative analyses of planktic and benthic foraminifera to assess the impact of the Middle Eocene Climatic Optimum (MECO, ~40 Ma) on these biotic groups studied along a shallow-water succession rich in larger benthic foraminifera (Sealza, Liguria, NW Italy). The MECO is one of the major Eocene global warming events, characterized by ~4–6°C warming, shifts in the global carbon cycle, and rise in atmospheric pCO2. The Sealza succession is interpreted as the product of a drowning ramp influenced by tectonic activity and provides an exceptional chance to compare biotic variations in shallow-water assemblages with deep-water communities across the MECO. In the section, the MECO interval is tentatively constrained by stable isotope oxygen data and calcareous plankton biostratigraphy. The marked decline in abundance of the epifaunal benthic Cibicidoides across the lower-middle part of the MECO suggests a decrease in oxygenation at the seafloor. Further evidence of oxygen depletion is the increase in organic matter content (TOC) of the sediment and the presence of infaunal genera Uvigerina and Bolivina. The planktic foraminiferal assemblages record the MECO warming in the upper water column as the mixed-layer warm index genera Acarinina and Morozovelloides markedly increase in abundance. In the post-MECO interval, here poorly exposed, cooler conditions are indicated by the dominance of the cold-water index genus Subbotina. Remarkably, Acarinina decline in abundance in the upper MECO interval and never recover. The MECO perturbance permanently impacted the benthic and planktic communities at Sealza that exceeded the tipping point to move to a new regime, thus proving the fauna to be not resilient, but also not recording any extinctions.

Improved Planktonic, Benthic Foraminiferal and Nannofossil Biostratigraphy Aids the Interpretation of the Evolution at Hole U1468A: IODP Expedition 359, the Maldives

Extended shallow carbonate platform, pelagic, and drift deposits were drilled during International Ocean Discovery Program (IODP) Expedition 359 in the Inner Sea of the Maldives. These sediments yield rich and well-diversified benthic, planktonic foraminiferal and nannofossil assemblages spanning from the early Oligocene to the Recent. We present here the shore-based revised integrated biostratigraphy of these microfossil groups at IODP Hole 359-U1468A together with the paleobathymetric reconstruction. Our data suggests the presence of a late Oligocene carbonate platform, marked by the shallowest water depths of the entire sequence of around 80 m. This carbonate platform sequence occurred from around 29 Ma, the extrapolated minimum age estimate, at least up to 27.5 Ma and possibly up to 25.4 Ma. Up the sequence, similar carbonate production conditions occurred until 22.5 Ma across the Oligocene–Miocene transition, equated at 23.04 Ma, with increased water depths >120 m. Notably, in the time interval approximately from 24 to 21.5 Ma, orbitally induced sapropel layers indicate a change of open to restricted circulation. However, at around 22.5 Ma, pelagic deposition at a distal slope occurred with sedimentation rates of 3 cm/years. This initially occurred in water depths of >350 m but gradually reached deposition in water depths of >500 m, which persisted from 21.12 Ma until approximately the extrapolated age of 12.8 Ma. Sedimentation rates gradually increased to 10.5 cm/1000 years at around 450 m below sea floor, marking the initiation of the drift sequence as identified in seismic lines with an age estimate of 12.8 Ma. The initiation of the drift sequence is also marked by a drastic decrease in the preservation of benthic and planktonic foraminifera from good to very poor at around 12.8 Ma. The drift sequence essentially continued to the present day but was interrupted by two events: the deposition of distinct shallow water benthic shoals and a large hiatus. From 12.8 Ma, a shallowing upward bathymetry is suggested by the occurrence of shallow benthic foraminiferal assemblages that close to around 11.93 Ma reached a maximum water depth of 80 m. This shoal then prograded into the basin and persisted at least until 9.89 Ma. Basin conditions with water depths exceeding 500 m were re-established in the upper part of the sedimentary succession after a hiatus spanning approximately from 9.83 Ma to 2.39 Ma, implying that renewed open ocean conditions occurred in the Pliocene–Pleistocene part of the sedimentary record.

Morphological evolution of menardiform globorotalids at Western Pacific Warm Pool ODP Hole 806C (Ontong-Java Plateau) Evolution morphologique du groupe de Globorotalia menardii au Site ODP 806C (Ontong-Java Plateau, Pacifique tropical occidental)

The morphological evolution was investigated in the tropical Neogene planktonic foraminiferal lineage Globorotalia menardii, G. limbata and G. multicamerata during the past 8 million years at ODP Hole 806C (Ontong-Java Plateau, western equatorial Pacific). This research is an extension of several similar studies since 2007 from the Caribbean Sea, the tropical Atlantic and the Eastern Equatorial Pacific. The goal is to find empirical and quantitative confirmation for morphological speciation – splitting or phyletic gradualism or accelerated evolution – in planktonic foraminifera with the above lineage as model objects. The present study from ODP Hole 806C serves as a test to discriminate between these evolutionary scenarios.In the western equatorial Pacific warm and stable environments prevailed back to Pliocene times, and potential influences of Northern Hemisphere Glaciation are thought to bear less severely on shell size evolution than in the Atlantic Ocean. A slow and gradual pattern of shell size increase is therefore expected in the western tropical Pacific, in contrast to the intermittent rapid menardiform shell size increase during periods of intensified formation of warm water eddies in the southern to tropical Atlantic.For this study a total of 11,101 specimens from 37 stratigraphic levels extending over the past 8 million years were morphometrically investigated thanks to the AMOR robot for imaging and microfossil orientation. Of those, 6080 specimens comprise the G. menardii–limbata-multicamerata plexus. Special attention was given to trends of spiral height (δX) versus axial length (δY) in keel view, for which bivariate contour- and volume-density diagrams were constructed to visualize speciation and evolutionary trends.The investigation at Hole 806C showed, that G. menardii evolved in a more gradual manner than in the Atlantic. Contour plots of δX versus δY reveal modest bimodality between 3.18 Ma – 2.55 Ma with a dominant branch consisting of smaller G. menardii (δX<∼300 μm) persisting until the Late Quaternary, and a less dominant branch of larger G. menardii (δX>∼300 μm) until 2.63 Ma. There is evidence for cladogenesis – splitting with subsequent morphological divergence in the Late Pliocene G. menardii-limbata-multicamerata lineage, and which may be linked to changes in the thermocline. Due to the general scarcity of G. multicamerata at Site 806, the divergence was less clearly expressed than originally expected. Up-section, bimodality vanished but G. menardii populations shifted towards extra large shells between 2.19-1.95 Ma.The morphological evolution of Pacific menardiform globorotalids contrasts the one observed in the Atlantic. This inter-oceanic asymmetry may indicate possible long-distance dispersal of G. menardii, at least during intermittent phases. For plankton biostratigraphy this implies, that correlating events represent more often than previously thought large scale environmental perturbations with local morphological ecophenotypic adaptations and nuances.

Exploring the paleoceanographic changes registered by planktonic foraminifera across the Cenomanian-Turonian boundary interval and Oceanic Anoxic Event 2 at southern high latitudes in the Mentelle Basin (SE Indian Ocean)

Planktonic foraminiferal population dynamics and benthic foraminiferal and radiolaria distributions combined with δ13C and δ18O measurements of both bulk carbonate and foraminifera provide clues concerning the paleoceanographic changes across the Cenomanian-Turonian boundary interval and the Oceanic Anoxic Event 2 (OAE 2) at southern high latitudes. Samples analyzed are from Integrated Ocean Discovery Program (IODP) Expedition 369 Site U1516 in the Mentelle Basin (eastern flank of the Naturaliste Plateau, Indian Ocean, SW Australia). Site U1516 was located at 60°–62°S paleolatitude during the mid-Cretaceous, and it is the first high latitude locality in the Southern Hemisphere where planktonic foraminifera are consistently recorded across the OAE 2 interval and its associated positive δ13C excursion. The sedimentary record at Site U1516 consists of a sequence of alternating black, dark greenish gray, and light greenish gray claystone in the Cenomanian that grade to white and light gray calcareous chalk interbedded with chert in the Turonian. The correlation between the δ13C and δ18O profiles at Site U1516 and the European reference section at Eastbourne (England) coupled with the integrated calcareous plankton biostratigraphy and stable isotopic data at Site U1516, indicate that a complete record of OAE 2 at Site U1516 was recovered. Below and in the lower part of OAE 2, the planktonic foraminiferal assemblages are dominated by small-sized (125–38 μm) opportunistic species of Microhedbergella and radiolaria indicating a dominantly eutrophic regime. Above the onset of OAE 2, a trough in the δ13C profile (Plenus Carbon Isotope Event: P-CIE) coinciding with a δ18O increase may correspond to the Plenus Cold Event as observed at low latitudes, although no evidence of cooling is registered in the microfossil assemblages. At Site U1516, the middle part of OAE 2 at the initiation of the plateau phase of the δ13C profile is masked by absence of carbonate, by the highest TOC values, and high biogenic silica (dominance of radiolaria) indicating this interval corresponded to a time of highly stressed eutrophic conditions with possible shoaling of the Carbonate Compensation Depth (CCD). Above this interval, bulk isotopic results yield lower δ13C values, and the CaCO3 increases are associated with the presence of even smaller-sized Microhedbergella showing cyclic fluctuations in absolute abundances with benthic foraminifera indicating dominantly eutrophic conditions likely affected by upwelling of nutrient-rich and δ13C-depleted intermediate water masses. Toward the top of OAE 2 and across the Cenomanian-Turonian boundary interval, the planktonic foraminiferal assemblages show changes in composition (e.g., Microhedbergella is replaced by Muricohedbergella), species occupying relatively deep ecological niches appear and an overall increase in diversity is observed. These features coupled with the foraminiferal species-specific δ13C and δ18O patterns reveal that Site U1516 occupied a paleoceanographic setting still affected by eutrophy likely related to enhanced input of nutrients but with episodes of stability with ecological/thermal separation in the surface waters. This interval also records the highest sea surface water paleotemperatures values estimated as 20°–23°C based on δ18O values of foraminiferal test and assuming seawater δ18O values of −1‰V-SMOW. Mesotrophic to oligotrophic conditions persisted after the OAE 2 and throughout the Turonian as evidenced by a diverse planktonic foraminiferal assemblage with different species occupying separate ecological niches in the mixed layer and thermocline.

Larger benthic and planktonic biostratigraphy and facies of Albian sediments in Coastal Fars Zone (Zagros area, south‐west Iran)

A total of 64 samples were collected from the Kazhdumi Formation (Albian) of south Zagros Basin (Coastal Fars Zone) in order to study the biostratigraphy and analyse the lithofacies. Stratigraphic distribution of identified larger benthic and planktonic foraminifers has confirmed the presence of three successive biozones: Mesorbitolina subconcava‐Orbitolina discoidea Zone, Favusella washitensis Zone followed by an upper Conicorbitolina conica‐Mesorbitolina parva Zone. Generally, orbitolinids are well developed in the Albian succession in the studied section, whereas the stratigraphic distribution of planktonic foraminifers is more restricted, dominating the Favusella washitensis Zone. Nevertheless, microscopic investigation recognizes five microfacies consisting of extraclast‐foraminifer packstone, peloid‐intraclast Orbitolina wackestone, foraminiferal plankton wackestone, intraclast‐Orbitolina grainstone, and coral‐rudist wackestone, which indicated a shallow water carbonates palaeoenvironment (intertidal, lagoon, bar) and open marine. The alternation of both planktic and benthic foraminifera through the Kazhdumi Formation confirms a rapid transgression and regression in the studied section during Albian time, which is attributed to Kazerun basement fault behaviour in the mentioned time interval.

THE BARREMIAN-TURONIAN EROSIONAL UNCONFORMITY IN THE M. MISMA AREA (LOMBARDY BASIN, SOUTHERN ALPS)

An erosional unconformity has been recognized by means of lithostratigraphy and calcareous plankton biostratigraphy in the Cretaceous succession of the M. Misma area (Southern Alps, Lombardy Basin). Due to synsedimentary tectonism, after a Cenomanian sliding and slumping phase, channelized sandstones and conglomerates, of Late Turonian age, have been scoured in the Barremian-Albian succession.

Upper Cretaceous volcaniclastic complexes and calcareous plankton biostratigraphy in the Western Pontides, NW Turkey

This study describes and interprets Upper Cretaceous volcaniclastics interbedded with hemipelagic to pelagic limestones, marls, and turbidites from the Western Pontides, northwestern Turkey. The Derekoy Formation, the Unaz Formation (red pelagic limestone unit), and the Cambu Formation can be distinguished, overlain by the turbiditic Akveren Formation. Biostratigraphic ages from the predominantly volcaniclastic Derekoy Formation indicate Turonian (Dicarinella concavata planktonic foraminifera zone, CC13/UC8-9 nannofossil zones) to middle/late Santonian ages up to CC17/UC13. The Unaz Formation, deposited during the late Santonian (UC13, Dicarinella asymetrica Zone), is overlain by the volcaniclastic Cambu Formation of latest Santonian (CC17b/UC13) to early/middle Campanian (CC20/UC15a) age. However, turbidite intercalations are already present diachronously from CC19/UC14d onwards, and the turbiditic Akveren Formation ranges up into the late Maastrichtian (Abathomphalus mayaroensis Zone). Geochemistry of the volcaniclastic units reveals information about the volcanic series and tectonic setting, although element mobility has to be considered. An overall trend of calc-alkaline to high-K calc-alkaline series and basaltic to basalt-andesitic rock types was identified. A negative Nb anomaly with respect to Th and Ce in all samples confirms the existence of a volcanic arc, also indicated by a negative Ti anomaly. Biostratigraphic age constraints give evidence for volcanic arc activity mainly between Turonian and early Campanian, ca. 91 - 79 Ma. Various geochemical data, especially element variations normalized to N-MORB, show two types of volcanic arc basalts (VAB): (1) Calc-alkaline to high-K calc-alkaline VAB have increased Nb and Zr values, (2) more tholeiitic VABs are depleted in Nb, Zr, Ti, V. The volcaniclastics successions were deposited in an arc setting triggered by different stages of subduction of the Neotethys Ocean to the south and contemporaneous spreading in the Western Black Sea Basin to the north. An extensional regime caused formation of small but deeper-water sedimentary basins along the southern shore of the Black Sea where volcaniclastic complexes interfingered within short lateral distances with pelagic and mass-flow deposits.

Large deadfalls of the ʻginsuʼ shark Cretoxyrhina mantelli (Agassiz, 1835) (Neoselachii, Lamniformes) from the Upper Cretaceous of northeastern Italy

Cretoxyrhina mantelli was a large pelagic lamniform shark geographically widespread during the Late Cretaceous, and well known because of several nearly complete skeletons from the Western Interior Seaway of North America. Here we report 15 partial skeletons belonging to lamniform sharks from the ‘lastame’ lithozone of the Upper Cretaceous Scaglia Rossa Formation of the Lessini Mountains (northeastern Italy). Seven partial but articulated skeletons include tooth sets that allow a confident attribution to Cretoxyrhina mantelli based on dental morphologies. We review the taxonomic history of C. mantelli, evidencing that the taxon was erected by Agassiz (1835) and tracing back four of the original syntypes. Based on calcareous plankton biostratigraphy, the rock in which the Italian skeletal remains are embedded is constrained to the middle-upper Turonian. Total length estimates of the specimens suggest that the sample includes the largest specimen of Cretoxyrhina mantelli (615–650 cm estimated total length) known to date. The placoid scale morphology indicates that C. mantelli most likely was a fast swimmer with a similar ecology as the extant white shark, Carcharodon carcharias. The associated skeletal elements of the specimens represent large chondrichthyan deadfalls and the cadavers decayed on the seafloor where they remained exposed for several months, as indicated by bioerosional traces, some of which are interpreted as a product of bone-eating worm activities and other bioerosional traces with Gastrochaenolites-like structure. The Cretoxyrhina mantelli remains described herein provide new information about the ʻlastameʼ vertebrate assemblage, which seemingly was strongly dominated by chondrichthyans, especially lamniform sharks.

Palaeoceanographical events from the late Miocene to Pleistocene of the Rio Grande Rise (south-western Atlantic) as indicated by Ostracoda

The present research assesses the significance of ostracods from the Rio Grande Rise for the understanding of the palaeoceanographical evolution of this important physiographical feature of the south-western Atlantic. The core MD11-L2P3, drilled in the western portion of the Rio Grande Rise, contains sediments ranging from the late Miocene (Tortonian) to the Pleistocene, according to planktonic foraminifer biostratigraphy. Thirty-one ostracod species belonging to 19 genera and nine families were identified. Cytheropteron and Krithe are the richest genera with six and four species, respectively. Bradleya ybate sp. nov., Bradleya majorani sp. nov. and Microcythere acuminata sp. nov. are described. Some species present high abundance and long stratigraphical occurrence throughout the studied section (e.g. Bradleya majorani sp. nov., Henryhowella asperrima, Poseidonamicus miocenicus Benson and Cythereis richardbensoni Yasuhara et al.), yet most have a shorter stratigraphical distribution. Cumulative diversity enabled the characterization of three assemblage groups, herein named AG I, AG II and AG III. Changes in the assemblage compositions are ascribed to hydrological variations associated with Neogene climatic events, inasmuch as the studied interval records the cooling trend established during the late mid-Miocene Climatic Optimum.http://zoobank.org/urn:lsid:zoobank.org:pub:146FF2DE-C331-4DB0-852D-EC8BC5D658AF

An integrated study of upper Campanian-lower Maastrichtian carbon isotopes and calcareous plankton biostratigraphy of the Kurdistan Region, northeastern Iraq

New carbon (δ13C) isotope records calibrated by planktonic bioevents provide general support for a late Campanian age assignment of the Shiranish Formation (Fm.) and its boundaries in the Dokan section (NE Iraq). The Shiranish Fm. is characterised at the base by a mid-Campanian unconformity as can be interpreted by absences of nannofossil zones CC20-21. The Shiranish Fm. then spans nannofossil biozones CC22-CC23a (UC15d-eTP to UC16aTP). Results obtained on carbon isotopes suggest that diagenesis affected and compromised a few carbonate samples in the uppermost 50 m of the section. However, once these samples are discarded, pristine trends suggest that the top of the section records a negative carbon isotope excursion that is interpreted as CMBa-c events that straddle the Campanian–Maastrichtian boundary. This interpretation is supported by the lowermost occurrence of planktic foraminifers Rugoglobigerina scotti and Contusotruncana contusa some 30 m above the base of the negative excursion and 10 m below a positive excursion identified as the Maastrichtian M1+ event. Discrepancies in the stratigraphic range of several planktic foraminifer bioevents are highlighted and advocate for the need of many more integrated records of planktic foraminifer and nannofossil biostratigraphy alongside carbon isotope stratigraphy in the eastern Tethys in order to improve regional and global schemes.

High‐resolution integrated calcareous plankton biostratigraphy and magnetostratigraphy at the Oligocene–Miocene transition in Southwestern Atlantic Ocean

After the formalization of the base of the Miocene in the Lemme‐Carrosio section (Italy) at the base of Subchron C6Cn.2n, the calcareous plankton biostratigraphy was refined in several open ocean Deep Sea Drilling Project/Ocean Drilling Program sites. However, high‐resolution quantitative biostratigraphic studies, integrating planktonic foraminifera and calcareous nannofossils, are still lacking for the time interval spanning the Oligocene–Miocene transition. Here, we present a reinvestigation of Deep Sea Drilling Project Hole 516F (Rio Grande Rise) and 4 oil wells drilled by Petróbras Brasileiro SA in the Campos Basin (SW Atlantic Ocean). We identified 12 planktonic foraminiferal and 18 calcareous nannofossil bioevents that have been integrated with an updated magnetostratigraphy of Hole 516F allowing the correlation with the GPTS and the identification of the Oligocene/Miocene boundary (base of Subchron C6Cn.2n) between the Top of Sphenolithus delphix and the Base of common Paragloborotalia kugleri. Furthermore, our results give new insights on the reliability of major calcareous plankton events across the Oligocene–Miocene transition: (a) the Sphenolithus ciperoensis Top, the S. delphix Base and Top, and the Sphenolithus cometa Base are reliable events at a global scale; (b) the Bases of Globoquadrina dehiscens and Sphenolithus disbelemnos &gt; 4 μm are correlatable events only within the study sector of the SW Atlantic Ocean; and (c) the Globoturborotalita ciperoensis Top, Globoturborotalita angulisuturalis Top, and Sphenolithus procerus Base are diachronous. Finally, previously unreported biostratigraphic data, such as the distribution range of S. disbelemnos &lt; 4 μm and Sphenolithus cf. S. pseudoheteromorphus, the Tenuitellinata praestainforthi acme interval, and the Top of common Globigerinoides primordius were identified in the Campos Basin.

Plankton biostratigraphy and magnetostratigraphy of the Santonian–Campanian boundary interval in the Mudurnu–Göynük Basin, northwestern Turkey

The Santonian–Campanian boundary interval close to the village of Göynük in northwestern Turkey (Bolu province) was recorded and examined with respect to nannofossil and foraminiferal biostratigraphy, magnetic polarity and magnetic susceptibility. During the Late Cretaceous, the Mudurnu–Göynük Basin was located on the Sakarya continent situated in the northwestern Tethyan Realm, north of the Neo-Tethys.The sections assessed for the present study comprise hemipelagic to pelagic deposits. Five localities were examined and a composite record spanning the Santonian–Campanian boundary was established. The stratigraphically older parts are characterised by uniform reddish limestone, while we frequently recorded shaly marls and marly limestones with recurrent tuff intercalations in the younger subsections.A biostratigraphic investigation of planktonic foraminifera and calcareous nannoplankton assemblages, together with magnetostratigraphy, provides a stratigraphic framework that allows to home in on the Santonian–Campanian boundary. Thus, biostratigraphic data suggest an age that ranges from the late Santonian Dicarinella asymetrica to the early Campanian Globotruncanita elevata planktonic foraminifera biozones, and calcareous nannofossil zones UC12–UC14 and CC16–CC18. The magnetostratigraphic assessment finds a palaeomagnetic reversal that can be recognised as the basal Campanian reversal C33r above polarity chron 34n, the Long Cretaceous Normal.Field magnetic susceptibility (MS) data show a distinct cyclic pattern in the lower Campanian. Sinusoidal patterns in the MS signature curve can presumably be interpreted as the 400 kyr orbital eccentricity cycle, and subsequent smaller-scale cycles of obliquity and precession can be identified even though volcanic activity impacted sedimentation. A sediment accumulation rate of 12 mm/kyr can be inferred for one of the sections.

Integrated stratigraphy of the Priabonian (upper Eocene) Urtsadzor section, Armenia

The transition from the Bartonian to the Priabonian, as traditionally understood, has long been associated with a series of extinctions and originations in several microfossil groups. The planktonic foraminifer genus Morozovelloides and large species of Acarinina suffered a rapid global extinction, as did many radiolarians. Calcareous nannofossils show several assemblage changes including the acme beginning of Cribrocentrum erbae and the lowest and highest occurrences of Chiasmolithus oamaruensis and C. grandis respectively. In shallow water environments, larger foraminifera also show an extinction among large species of Nummulites, as well as the first occurrences of the stratigraphically important genus Spiroclypeus. However, the correlation between shallow and deep water records remains uncertain, as do the mechanisms driving these biotic events. Here we present the results of a new integrated stratigraphical study (calcareous nannofossils, planktonic foraminifera, larger benthic foraminifera, and low-resolution magnetostratigraphy) of the Urtsadzor section in south-western Armenia which appears to be continuous through this interval. The Urtsadzor section consists of calcareous siltstones rich in micro- and nannofossils, with interbedded limestones containing abundant larger benthic foraminifera. Our new data enable us to correlate larger foraminiferal events with global plankton biostratigraphy, in a section outside of southwest Europe where most previous correlations have been based. At Urtsadzor, the large Nummulites species of N. millecaput-group are present throughout the whole section but decrease in abundance toward the top. The first occurrence of Spiroclypeus, also occurs in the upper part of the section, marking the SBZ 18/19 boundary. These events are associated with the phylogenetic development of the Nummulites fabianii and Heterostegina reticulata lineages. However, the calcareous plankton biostratigraphy indicates the section is well within the Priabonian; within planktonic foraminiferal Zones E14 and E15 and calcareous nannoplankton Zones CNE 18 and CNE 19. These results indicate larger foraminiferal events occur well above the planktonic foraminiferal extinction level and nannofossil assemblage changes indicating the events are not synchronous across groups, with implications for biostratigraphy and recognition of the basal Priabonian in different depositional settings and regions.

HIGH RESOLUTION BIOSTRATIGRAPHY AND PALEOECOLOGY OF THE EARLY PLIOCENE SUCCESSION OF PISSOURI BASIN (CYPRUS ISLAND)

The Pissouri basin (Cyprus Island) corresponds to a small tectonically controlled depression elongated NNW-SSE and widening southward in the direction of the deep Mediterranean domain. In the centre of the basin, the section Pissouri South, about 100 m thick, consists of well-preserved cyclic marine sediments including laminated brownish layers alternating with grey homogeneous marls. Plankton biostratigraphy (calcareous nannofossil and planktonic foraminifera) revealed a remarkable number of biovents bracketing the Zanclean-Piacenzian boundary. In particular the Highest Occurrence (HO) of Reticulofenestra pseudoumbilicus suggests the presence of NN14/15-NN16 nannofossil biozone boundary, dated at 3.84 Ma. Additionally the defined planktonic foraminiferal MPL3-MPL4a and MPL4a-MPL4b zone boundaries point to ages between 3.81 and 3.57 Ma, in Pissouri North section. Zanclean/Piacenzian boundary (3.6 Ma) is placed at 75.8 m from the base of the section, considering Discoaster pentaradiatus top paracme (3.61 Ma) and Globorotalia crassaformis first influx (3.6 Ma) bioevents. The cyclically developed sapropelic layers around the Zanclean – Piacenzian boundary suggest a climate characterized by a period of warm temperate conditions and a highly stratified water column that occurred at times of precession minima.

Assessing pelagic palaeoenvironments using foraminiferal assemblages — A case study from the late Campanian Radotruncana calcarata Zone (Upper Cretaceous, Austrian Alps)

Two upper Campanian sections in the Austrian Alps representing the north western Tethyan biogeographic realm from either sides of the Penninic Ocean (Alpine Tethys) have been examined aiming at a high-resolution assessment of foraminiferal assemblages: the Postalm section from the Northern Calcareous Alps (southern active margin) and the Oberhehenfeld section from the Ultrahelvetics (northern passive margin). This study focuses on plankton biostratigraphy and foraminiferal palaeoecology of the Radotruncana calcarata Total Range Zone.The Postalm section displays cyclic red deposits with marls and marly limestones, while we find uniform grey marls at Oberhehenfeld. The Oberhehenfeld section from the Ultrahelvetics can be correlated stratigraphically to the Postalm section using foraminifera, calcareous nannoplankton and stable isotope stratigraphy, and provides a point of comparison from the northern margin of the Penninic Ocean.The two sections show minimal difference in faunal composition and few distinct local stratigraphic signals. Palaeoenvironmental trends from the late Campanian can be recognised relating the two sections from the Austrian Alps. The depositional water depth can be reconstructed as some 500–800m. Plankton assemblages show a remarkable stability despite the sudden appearance and disappearance of R. calcarata, hinting at the late Campanian as a time interval of general foraminiferal stasis without significant evolutionary events. We speculate that the origin and extinction of R. calcarata are related to the prolonged evolution of ocean stratification during the Campanian from the mid-Cretaceous sluggish hothouse during a time of general slow greenhouse climate decline.

Magnetic fabric of Plio-Pleistocene sediments from the Crotone fore-arc basin: Insights on the recent tectonic evolution of the Calabrian Arc (Italy)

Low-field anisotropy of magnetic susceptibility (AMS) analyses were performed on 532 samples collected in 36 (mostly lower Pliocene to lower Pleistocene) marine clay sites from the Crotone basin, a fore-arc basin located on top of the external Calabrian accretionary wedge. The Crotone basin formed since mid-late Miocene under a predominant extensional tectonic regime, but it was influenced thereafter by complex interactions with NW–SE left-lateral strike-faults bounding the basin, which also yielded post-1.2Ma ∼30° counterclockwise block rotations. The basin is filled by continental to marine sediments yielding one of the thickest and best-exposed Neogene succession available worldwide. The deep-marine facies – represented by blue-grey marly clays gave the best results, as they both preserved a clear magnetic fabric, and provided accurate chronology based on previously published magnetostratigraphy and calcareous plankton (i.e. foraminifers and nannofossils) biostratigraphy. Magnetic susceptibility range and rock magnetic analyses both indicate that AMS reflects paramagnetic clay matrix crystal arrangement. The fabric is predominantly oblate to triaxial, the anisotropy degree low (<1.06), and the magnetic foliation mostly subparallel to bedding. Magnetic lineation is defined in 30 out of 36 sites (where the e12 angle is <35°). By also considering local structural analysis data, we find that magnetic fabric was generally acquired during the first tectonic phases occurring after sediment deposition, thus validating its use as temporally dependent strain proxy. Although most of the magnetic lineations trend NW–SE and are orthogonal to normal faults (as observed elsewhere in Calabria), few NE–SW compressive lineations show that the Neogene extensional regime of the Crotone basin was punctuated by compressive episodes. Finally, compressive lineations (prolate magnetic fabric) documented along the strike-slip fault bounding the basin to the south support the significance of Pleistocene strike-slip tectonics. Thus the Crotone basin shows a markedly different tectonics with respect to other internal and western basins of Calabria, as it yields a magnetic fabric still dominated by extensional tectonics but also revealing arc-normal shortening episodes and recent strike-slip fault activity. The tectonics documented in the Crotone basin is compatible with a continuous upper crustal structural reorganization occurring during the SE-migration of the Calabria terrane above the Ionian subduction system.

A major change in the sedimentation regime in the Crotone Basin (Southern Italy) around 3.7–3.6 Ma

The Lower Pliocene succession of the Crotone Basin (Calabrian Arc, Southern Italy) is mainly comprised of blue-grey marly clay with good magnetic properties. Here the bio-magnetostratigraphic data indicate a mean sedimentation rate of about 12–15cm/kyr. Around 3.7–3.6Ma a major change in the sedimentation regime occurred: the blue-grey hemipelagic marls grade rapidly into silty marls with a significant increase in the terrigenous fraction and with abundant siliceous remains throughout the whole interval. Magnetic properties of these sediments are very poor, but an integrated calcareous plankton biostratigraphy (foraminifera and nannofossils) infers a high average sedimentation rate (about 50–60cm/kyr). The abrupt onset of this sedimentation regime in the Crotone Basin is contemporaneous with a major unconformity already recognized in the northern sector of the basin, part of a major reorganization phase in the whole Apenninic–Maghrebid Chain known as “Globorotalia puncticulata event”. Reports of coeval siliceous sediments in other marginal basins of the Apennines (Southern Calabria, Southern and Northern Apennines) suggest that this “siliceous event” might have been regionally extensive, having important palaeoceanographical implications. We infer that the “siliceous event” is characterized by a combined tectonic- and climate-induced change in palaeoceanographic conditions. The tectonic triggering factors may have been linked to two synchronous events in the Tyrrhenian–Apennine system: 1) the shortening event also known as “G. puncticulata event”, and 2) the coeval opening of the Vavilov Basin in the Tyrrhenian Sea which yielded profound influences in terms of physiography and characteristics of the Crotone Basin. The consequent uplift of the Southern Apennines would have increased sediment supply and availability of silica, resulting in eutrophication and enhanced silica preservation. Strong winter mixing and possibly upwelling conditions could have increased primary productivity during heavy isotope stages Gi4, Gi2 and MG8, at the onset of the “siliceous event”. This important event, lasting from ca. 3.6Ma to ca. 3.2Ma, would have recorded a peculiar transitional period before further climatic deterioration and more drastic palaeoceanographic changes occurred around 3.1Ma, leading to cyclic sapropel deposition in the whole of the Mediterranean sea.

Astronomical calibration of upper Campanian–Maastrichtian carbon isotope events and calcareous plankton biostratigraphy in the Indian Ocean (ODP Hole 762C): Implication for the age of the Campanian–Maastrichtian boundary

An integrated framework of magnetostratigraphy, calcareous microfossil bio-events, cyclostratigraphy and δ13C stratigraphy is established for the upper Campanian–Maastrichtian of ODP Hole 762C (Exmouth Plateau, Northwestern Australian margin). Bulk-carbonate δ13C events and nannofossil bio-events have been recorded and plotted against magnetostratigraphy, and provided absolute ages using the results of the cyclostratigraphic study and the recent astronomical calibration of the Maastrichtian. Thirteen carbon-isotope events and 40 nannofossil bio-events are recognized and calibrated with cyclostratigraphy, as well as 14 previously published foraminifer events, thus constituting a solid basis for large-scale correlations. Results show that this site is characterized by a nearly continuous sedimentation from the upper Campanian to the K-Pg boundary, except for a 500kyr gap in magnetochron C31n. Correlation of the age-calibrated δ13C profile of ODP Hole 762C to the δ13C profile of the Tercis les Bains section, Global Stratotype Section and Point of the Campanian–Maastrichtian boundary (CMB), allowed a precise recognition and dating of this stage boundary at 72.15±0.05Ma. This accounts for a total duration of 6.15±0.05Ma for the Maastrichtian stage. Correlation of the boundary level with northwest Germany shows that the CMB as defined at the GSSP is ~800kyr younger than the CMB as defined by Belemnite zonation in the Boreal realm. ODP Hole 762C is the first section to bear at the same time an excellent recovery of sediments throughout the upper Campanian–Maastrichtian, a precise and well-defined magnetostratigraphy, a high-resolution record of carbon isotope events and calcareous plankton biostratigraphy, and a cyclostratigraphic study tied to the La2010a astronomical solution. This section is thus proposed as an excellent reference for the upper Campanian–Maastrichtian in the Indian Ocean.

Integrated biomagnetostratigraphy of the Alano section (NE Italy): A proposal for defining the middle-late Eocene boundary

Research Article| May 01, 2011 Integrated biomagnetostratigraphy of the Alano section (NE Italy): A proposal for defining the middle-late Eocene boundary Claudia Agnini; Claudia Agnini 1Dipartimento di Geoscienze, Università di Padova, Via G. Gradenigo, I-35131 Padova, Italy2Istituto di Geoscienze e Georisorse, CNR-Padova c/o Dipartimento di Geoscienze, Università di Padova, Via G. Gradenigo, I-35131 Padova, Italy Search for other works by this author on: GSW Google Scholar Eliana Fornaciari; Eliana Fornaciari 1Dipartimento di Geoscienze, Università di Padova, Via G. Gradenigo, I-35131 Padova, Italy Search for other works by this author on: GSW Google Scholar Luca Giusberti; Luca Giusberti 1Dipartimento di Geoscienze, Università di Padova, Via G. Gradenigo, I-35131 Padova, Italy Search for other works by this author on: GSW Google Scholar Paolo Grandesso; Paolo Grandesso 1Dipartimento di Geoscienze, Università di Padova, Via G. Gradenigo, I-35131 Padova, Italy Search for other works by this author on: GSW Google Scholar Luca Lanci; Luca Lanci 3Facoltà di Scienze Ambientali, Università di Urbino, Loc. Crocicchia, 61029 Urbino, Italy4Alpine Laboratory of Paleomagnetism (ALP), Via Madonna dei Boschi 76, I-12016 Peveragno (CN), Italy Search for other works by this author on: GSW Google Scholar Valeria Luciani; Valeria Luciani 5Dipartimento di Scienze della Terra—Polo Scientifico Tecnologico, Università di Ferrara, Via G. Saragat, 1, I-44100, Ferrara, Italy Search for other works by this author on: GSW Google Scholar Giovanni Muttoni; Giovanni Muttoni 4Alpine Laboratory of Paleomagnetism (ALP), Via Madonna dei Boschi 76, I-12016 Peveragno (CN), Italy6Dipartimento di Scienze della Terra, Università di Milano, Via Mangiagalli 34, I-20133 Milano, Italy Search for other works by this author on: GSW Google Scholar Heiko Pälike; Heiko Pälike 7National Oceanography Centre, University of Southampton Waterfront Campus, European Way, SO14 3ZH Southampton, UK Search for other works by this author on: GSW Google Scholar Domenico Rio; Domenico Rio 1Dipartimento di Geoscienze, Università di Padova, Via G. Gradenigo, I-35131 Padova, Italy Search for other works by this author on: GSW Google Scholar David J.A. Spofforth; David J.A. Spofforth 7National Oceanography Centre, University of Southampton Waterfront Campus, European Way, SO14 3ZH Southampton, UK Search for other works by this author on: GSW Google Scholar Cristina Stefani Cristina Stefani 1Dipartimento di Geoscienze, Università di Padova, Via G. Gradenigo, I-35131 Padova, Italy Search for other works by this author on: GSW Google Scholar GSA Bulletin (2011) 123 (5-6): 841–872. https://doi.org/10.1130/B30158.1 Article history received: 22 Aug 2009 rev-recd: 22 Oct 2009 accepted: 29 Oct 2009 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Claudia Agnini, Eliana Fornaciari, Luca Giusberti, Paolo Grandesso, Luca Lanci, Valeria Luciani, Giovanni Muttoni, Heiko Pälike, Domenico Rio, David J.A. Spofforth, Cristina Stefani; Integrated biomagnetostratigraphy of the Alano section (NE Italy): A proposal for defining the middle-late Eocene boundary. GSA Bulletin 2011;; 123 (5-6): 841–872. doi: https://doi.org/10.1130/B30158.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Alano section has been presented at the International Subcommission on Paleogene Stratigraphy (ISPS) as a potential candidate for defining the global boundary stratotype section and point (GSSP) of the late Eocene Priabonian Stage. The section is located in the Venetian Southern Alps of the Veneto region (NE Italy), which is the type area of the Priabonian, being exposed along the banks of the Calcino torrent, near the village of Alano di Piave. It consists of ∼120–130 m of bathyal gray marls interrupted in the lower part by an 8-m-thick package of laminated dark to black marlstones. Intercalated in the section, there are eight prominent marker beds, six of which are crystal tuff layers, whereas the other two are bioclastic rudites. These distinctive layers are useful for regional correlation and for an easy recognition of the various intervals of the section. The section is easily accessible, crops out continuously, is unaffected by any structural deformation, is rich in calcareous plankton, and contains an expanded record of the critical interval for defining the GSSP of the Priabonian. In order to further check the stratigraphic completeness of the section and constrain in time the critical interval for defining the Priabonian Stage, we performed a high-resolution study of integrated calcareous plankton biostratigraphy and a detailed magnetostratigraphic analysis. Here, we present the results of these studies to open a discussion on the criteria for driving the “golden spike” that should define the middle Eocene–late Eocene boundary. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Calcareous plankton events at the Early/Middle Miocene transition of DSDP Hole 608: comparison with Mediterranean successions for definition of the Langhian GSSP

We propose a revision of the calcareous plankton biostratigraphy of the upper Burdigalian/early Langhian interval (Early/Middle Miocene) of the DSDP Hole 608 succession (northeastern Atlantic Ocean), one of the most complete open-ocean Miocene sequences. We detected a set of calcareous plankton events through a 26m thick succession (320-346 mbsf), spanning the interval from 14.969 to 17.268 Ma, chronologically constrained through paleomagnetic and astrochronological data. "Standard" bioevents were tested and in some cases they resulted poorly applicable to the investigated succession. Conversely, the quantitative biostratigraphic analysis highlighted additional biohorizons (Helicosphaera ampliaperta Last Common Occurrence, Sphenolithus heteromorphus Paracme Inter-val, Paragloborotalia siakensis Acme "a") considered till now restricted to the Mediterranean region. This results in a better applicability of Mediterranean zonal schemes, providing a higher biostratigraphic resolution. Our results point out strict affinity between Atlantic and Mediterranean successions in Early/Middle Miocene. Thus, in the perspective of establishing the Langhian GSSP, that according to the historical criterion must be located in the Mediterranean region, our results provide significant correlation tools between Mediterranean and open-ocean successions.