Calcareous Plankton 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.

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.

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.

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 > 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 < 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.

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.

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.

Integrated stratigraphy of the La Vedova section (Conero Riviera, Italy) and implications for the Burdigalian/Langhian boundary

We present a high resolution integrated stratigraphy (calcareous plankton biostratigraphy and magnetostratigraphy) of the upper Burdigalian to lower Langhian interval in the La Vedova section (Conero Riviera, Italy). The succession of planktonic foraminifer and calcareous nannofossil events and their relative position in the La Vedova section are comparable with those recorded in other Mediterranean sections suggesting a continuous deposition across the Burdigalian/Langhian boundary interval. The high resolution magnetostratigraphic record, integrated with calcareous plankton events, has been correlated to the ATNTS2004 and ranges from sub-chrons C5Cn.1n to C5Bn.2n. In addition, the integrated magnetobiostratigraphic record of the La Vedova section provides a new magnetostratigraphic calibration of calcareous plankton events, thereby improving the existing Mediterranean biochronology for the upper Burdigalian to lower Langhian. On the basis of our magnetobiostratigraphic results, the deep marine La Vedova section could be considered a suitable succession for defining the Langhian GSSP (Global Stratotype Section and Point). The recommended guiding criteria to identify the base of the Langhian stage (the Praeorbulina datum and the magnetic reversal C5Cn/C5Br) are recorded in the section. In this work the Praeorbulina datum is represented by the first occurrence of P. glomerosa curva following Blow (1956; 1969). In the La Vedova section, this bioevent postdates the Acmea End of the planktonic foraminifer Paragloborotalia siakensis and the Paracme End of the calcareous nannofossil Sphenolithus heteromorphus, approximates the C5Br/C5Bn.2n reversal boundary and is dated at 15.23 Ma. The top of Chron C5Cn, dated at 15.974 Ma, is better approximated by the Last Common Occurrences of the calcareous nannofossil Helicosphaera ampliaperta and the planktonic foraminifer Paragloborotalia bella. At La Vedova the first occurrence of P. glomerosa curva is about 740 kyrs younger than C5Cn /C5Br reversal boundary, which represents the provisional guiding criterion to define the base of the Langhian (Lourens et al. 2004). The age difference between the Praeorbulina datum and the top of C5Cn implies that the Langhian GSSP cannot be located in a position close to both Chron C5Cn and the Praeorbulina datum (Lourens et al. 2004) and that the selection of either of these guiding criteria to identify the base of the Langhian will strongly affect its duration.

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.

Paleomagnetic evidence for a post-1.2 Ma disruption of the Calabria terrane: Consequences of slab breakoff on orogenic wedge tectonics

In the past few years, a wealth of paleomagnetic data gathered from Neogene sediments consistently showed that since ca. 10 Ma the Calabria terrane coherently drifted ~500 km ESE-ward from the Sardinian margin, and rotated 15°–20° clockwise (CW) as a rigid microplate between 2 and 1 Ma. Here we report on a high-resolution paleomagnetic investigation of the Crotone forearc basin of northern Calabria. The integrated calcareous plankton biostratigraphy indicates early Pliocene (Zanclean) to late early Pleistocene (Calabrian) ages for 29 successful paleomagnetic sites and/or sections. Unexpectedly, four domains undergoing distinct rotations are documented. Two blocks have undergone a CW rotation statistically undistinguishable, for both timing and magnitude, from the rigid Calabria rotation documented in the past. Two additional ~10-km-wide blocks yielded a 30.8° ± 22.5° and 32.0° ± 9.2° post–1.2 Ma counterclockwise rotation, likely due to left-lateral shear along two NW-SE fault zones. We infer that since advanced early Pleistocene times, after the end of the uniform CW rotation, left-lateral strike-slip tectonics disrupted the Calabria terrane, overwhelming a widespread extensional regime accompanying the Calabria drift since late Miocene times. Seismological evidence reveals that only the southern part of the Ionian slab subducting below Calabria is continuous, while beneath northern Calabria a slab window between 100 and 200 km depth is apparent. We suggest that the partial breakoff of the Ionian slab after 1 Ma induced the fragmentation of the Calabria wedge, and that strike-slip faults from the Crotone basin decoupled “inactive” northern Calabria from southern Calabria, still drifting towards the trench.

Orbital chronology of Early Eocene hyperthermals from the Contessa Road section, central Italy

High-resolution geochemical analyses of the Lower Eocene Contessa Road section (Italy) reveal orbitally controlled fluctuations in the percent concentration of calcium carbonate (wt.% CaCO 3) that include the ETM2 (Elmo) and ETM3 (“X”) hyperthermal events. Patterns of increased dissolution, negative carbon isotope excursions, and warmer global climates are intimately linked to maxima in insolation, through the global carbon cycle. Extraction of short- and long-eccentricity orbital periodicities of the wt.% CaCO 3 record provides a relative cyclochronology for the interval ranging from ∼ 52 to ∼ 55.5 Ma. The Contessa Road section is easily accessible and offers a continuous integrated stratigraphic record (stable isotopes, standard calcareous plankton biostratigraphy, magnetostratigraphy, and cyclostratigraphy), thus providing a potential type succession for the study of Early Eocene hyperthermals.

The Messinian – Zanclean boundary in the Northern Apennine

The Miocene-Pliocene boundary in the Northern Apennine was the object of several studies prior to the definition of the GSSP of the Zanclean stage in the Eraclea Minoa section (Sicily, Italy). This definition came at the end of the ’90s, after an accurate and Mediterranean wide high resolution biostratigraphic study of the basal Pliocene deposits. Since then calcareous plankton biostratigraphy allows to correlate the very base of the Zanclean through the occurrence of two consecutive sinistrally coiled Neogloboquadrina acostaensis influxes, respectively placed within the 1st/2nd cycle and the 2nd/3rd cycle from the base astronomically dated at 5.33Ma (insolation peak 510). Besides these bioevents, the classical Spheroidinellopsis spp. acme interval, the base of subchron Thvera and the cyclic signal of both biota and lithology help recognize the base of the Zanclean stage. Several sections and boreholes were studied in an east (Marche region) to west (Emilia region) transect along the Northern Apennine. Despite different sampling resolution, the two N. acostaensis sinistral influxes were recognized in each sites except the Montepetra borehole were the definition of the Zanclean base was achieved through cyclostratigraphic features. Some nannofossil bioevents, such as the drop of abundance of D. variabilis and the beginning of a paracme interval of R. pseudoumbilicus, revealed to be useful for a better constraining of the basal Zanclean. Thus the sedimentary succession across the Messinian – Zanclean boundary was recognized to be continuous and the base of the Zanclean stage coeval to its GSSP at Eraclea Minoa, thus dated at 5.33 Ma. This demonstrates that the Zanclean restoration of marine condition that ended the Messinian salinity crisis was a synchronous event, geologically speaking within the present resolution power, throughout the entire Mediterranea region.

Integrated stratigraphy and 40Ar/ 39Ar chronology of early Middle Miocene sediments from DSDP Leg 42A, Site 372 (Western Mediterranean)

An integrated magneto-biostratigraphic framework is presented for Middle Miocene sediments of DSDP Site 372 located in the Western Mediterranean. Detailed biostratigraphic analysis shows a nearly complete sequence of early Middle Miocene calcareous plankton bioevents in the Mediterranean, including the LCO (Last Common Occurrence) of the nannofossil Sphenolithus heteromorphus which has been astronomically dated in the Ras il Pellegrin (RIP) section on Malta Island [Abels, H.A., Hilgen, F.J., Krijgsman, W., Kruk, R.W., Raffi, I., Turco, E., Zachariasse, W.J., 2005. Long-period orbital control on middle Miocene global cooling: integrated stratigraphy and astronomical tuning of the Blue Clay Formation on Malta, Paleoceanography, 20, PA4012. doi: 10.1029/2004PA001129. 11 pp]. Thermal demagnetization of discrete samples revealed a characteristic low-temperature component with dual polarities despite a weak paleomagnetic signal. The resultant magnetostratigraphic record, combined with the calcareous plankton biostratigraphy, is straightforwardly correlated to the geomagnetic polarity time scale (CK95) of Cande and Kent [Cande, S.C., Kent, D.V., 1995. Revised calibration of the Geomagnetic Polarity Time Scale for the Late Cretaceous and Cenozoic, J. Geophys. Res., 100, 6093–6095] and the Astronomical Tuned Neogene Time Scale (ATNTS04) of Lourens et al. [Lourens, L.J., Hilgen, F.J., Laskar, J., Shackleton, N.J., Wilson, D., 2004. The Neogene Period. In: Gradstein F.M., Ogg J.G., Smith A.G. (Eds.), A Geologic Time Scale, Cambridge Univ. Press, pp. 409–440]. The subchrons recorded in Site 372 succession range from C5Br up to C5AAr. To confirm the magnetostratigraphic calibration, 40Ar/ 39Ar dating was performed on feldspar of two volcanic ash layers. The radio-isotopic dating indicates a younger age for these two ash layers compared to the magnetostratigraphic calibrated ages according to the CK95 and ATNTS04 age models. However, if the astronomically calibrated age of 28.21 ± 0.04 Ma is used for the Fish Canyon standard (FCs), the age for the older ash layer exactly matches its ATNTS04 age. Ages for bioevents were calculated assuming constant sedimentation rates between magnetostratigraphic age-tie points. The S. heteromorphus LCO has an age of 13.54 Ma and 13.63 Ma according to CK95 and ATNTS04, respectively, which is consistent with the astronomical tuned age of 13.65 Ma determined at RIP section [Abels, H.A., Hilgen, F.J., Krijgsman, W., Kruk, R.W., Raffi, I., Turco, E., Zachariasse, W.J., 2005. Long-period orbital control on middle Miocene global cooling: integrated stratigraphy and astronomical tuning of the Blue Clay Formation on Malta, Paleoceanography, 20, PA4012. doi:10.1029/2004PA001129. 11 pp]. We therefore conclude that the magnetostratigraphic calibration of DSDP Site 372 is correct and that, for the time being, this site can be considered as a reference section for the early Middle Miocene of the Mediterranean region.

Micropaleontological study on the Miocene calcareous turbidite deposits of Faeto and Tufillo formations (eastern sector of the Southern Apennine chain)

A biostratigraphic study was carried out on four sections of the Miocene Tufillo and Faeto Formations (Southern Apennines). The sediments analyzed were referred to the late Burdigalian-early Tortonian on the basis of planktonic foraminifers (MMi2b Subzone through the MMi8 Zone) and calcareous nannofossils (MNN3b Zone through the MNN7 Zone). Almost the majority of the bioevents of the recently published Miocene biozonal schemes of Mediterranean area were identified. Particularly, the marked changes in the abundance pattern of Paragloborotalia siakensis resulted very useful to correlate the sediments. A new acme abundance of the letter species has been recorded in the uppermost part of the Burdigalian planktonic foraminiferal MMi2b Subzone. Moreover, the integrated calcareous plankton biostratigraphy revealed that the First Common Occurrence (FCO) of Sphenolitus heteromorphus occurs before the Last Occurrence (LO) of Catapsidrax dissimilis , in the upper part of Burdigalian record. This study indicates that the lower Langhian portion of the Tufillo Formation is characterized by arkose sandstones which pass upwards into calcarenites and/or calcirudites and marly deposits. Field data suggest that these sandstones directly overly the Numidian Sandstones. The Faeto Formation starts with calcarenites and calcareous marls, in the calcareous nannofossil MNN3b Zone (Burdigalian), and lies on the Numidian Sandstones as well. High-resolution sampling and biostratigraphy reveal that the deposition of the Numidian Sandstones ends in the late Burdigalian stage, just below the FCO of S. heteromorphus (MNN3b Zone) and the LO of C. dissimilis (MMi2b Subzone).

Integrated quantitative biostratigraphy of the latest Tortonian–early Messinian Pissouri section (Cyprus): An evaluation of calcareous plankton bioevents

A quantitative study was performed on planktonic foraminifera and calcareous nannofossils of the astronomically dated Late Miocene Pissouri section (Cyprus). Our results confirm the reliability of well-known planktonic foraminiferal events as Catapsydrax parvulus LO (Last Occurrence), sinistral coiling change of Globorotalia scitula, Globorotalia miotumida group FRO (First Regular Occurrence), Globorotalia nicolae FO (First occurrence) and LO, sinistral coiling change of Neogloboquadrina acostaensis and also of several important calcareous nannofossil events ( Amaurolithus primus FO, Amaurolithus delicatus FO, Reticulofenestra rotaria FO and FCO). Integrated planktonic foraminifera and calcareous nannoplankton data contribute to an enhanced time resolution of the Tortonian - early Messinian interval in the Levantine basin, and contribute to detailed correlations throughout the Eastern Mediterranean. In addition, we compare methodologies commonly used in calcareous plankton biostratigraphy, and shortly outline sources of bias that can influence the results of stratigraphic studies.