Integrated Stratigraphy and Astronomical Tuning of Lower-Middle
Total Page:16
File Type:pdf, Size:1020Kb
ARTICLE IN PRESS Quaternary International xxx (2009) 1–12 Contents lists available at ScienceDirect Quaternary International journal homepage: www.elsevier.com/locate/quaint Integrated stratigraphy and astronomical tuning of lower–middle Pleistocene Montalbano Jonico section (southern Italy) N. Ciaranfi a,*, F. Lirer b, L. Lirer c, L.J. Lourens d, P. Maiorano a, M. Marino a, P. Petrosino c, M. Sprovieri b, S. Stefanelli a, M. Brilli e, A. Girone a, S. Joannin f, N. Pelosi b, M. Vallefuoco b a Dipartimento di Geologia e Geofisica, Universita` di Bari, Via E. Orabona 4, 70125 Bari, Italy b Istituto per l’Ambiente Marino Costiero (IAMC) Sede Napoli - CNR, Calata Porta di Massa, Interno Porto di Napoli, 80133, Napoli, Italy c Dipartimento di Scienze della Terra, Universita` degli Studi di Napoli Federico II, L.go San Marcellino 10, 80138 Napoli, Italy d Faculty of Geosciences, Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands e Istituto di Geologia Ambientale e Geoingegneria (IGAG)dCNR, Via Bolognola 7, 00138 Rome, Italy f UMR 5125 PEPS, CNRS, France; Universite´ Lyon 1, Campus de La Doua, Baˆtiment Ge´ode, 69622 Villeurbanne Cedex, France article info abstract Article history: Astronomical calibration of the lower–middle Pleistocene Montalbano Jonico section located in the Available online xxx Lucania Basin (Southern Italy) is presented. Previous papers widely discussed the integrated stratigraphy (calcareous nannofossils, sapropel stratigraphy, benthic and planktonic oxygen stable isotopes) and the paleoenvironmental features of this section and its potential suitability for the selection of the Middle Pleistocene Global Stratotype Section and Point (GSSP). In this study, new planktonic d18O data, additional biostratigraphical constraints and new tephrochronology on volcaniclastic layers occurring within the studied record are reported. The new chronostratigraphic framework provides a robust base for correlation of the oxygen isotope stratigraphy for the Montalbano Jonico section with the glacial and interglacial fluctuations of the Oceanic and Mediterranean d18O reference deep-sea records. Specifically, the lower part of the Montalbano Jonico section (Interval A) provides correlation of the planktonic and benthic d18O cycles to Marine Isotope Stage (MIS) 36 to MIS 23. Interval A includes a distinct peak of left-coiled neo- globoquadrinids, the Globoratalia crassaformis influx, the First Occurrence of Gephyrocapsa omega, and the First Common Occurrence and Last Common Occurrence of Reticulofenestra asanoi. These stratigraphical constraints support the tuning of five sapropel layers included in this part of the section to insolation cycles i-112, i-104, i-102, i-90 and i-86. The upper part of the section (Interval B), which includes the temporary disappearance (td2) of G. omega and tephra layer V5, Ar/Ar age dated at 719.5 Æ 12.6 ka, is consistent with identification of MIS 22 to MIS 16 in the planktonic d18O pattern. The d18O time series of the whole section was reconstructed using the midpoints of individual sapropels and their correlative precession minima, visual comparison of the d18O pattern with the record available at the Mediterranean ODP Site 975, and, in the upper part of the section, the Ar/Ar age of tephra V5. The developed astronomical tuning revealed that the Montalbano Jonico section covers an interval from 1240 ka to 645 ka. A significant change in sedi- mentation rate occurs between Intervals A (0.53 m/ky) and Interval B (0.91 m/ky) at about 870 ka and is consistent with a sea-level drop from a bathyal to a circalittoral environment. Bioevents recognised in the Montalbano Jonico section have been dated according to the astronomical calibration, and age assign- ments of tephra V1–V4 and V6–V9 are also proposed. The Montalbano Jonico section fills the gap between the top of the Vrica section and the base of the Ionian informal Middle Pleistocene stage, and represents a Mediterranean reference section for the Mid-Pleistocene transition. Ó 2009 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction Astronomical dating of late Neogene sedimentary sequences from the Mediterranean has now been well established and forms the backbone of the Astronomical Tuned Neogene Time Scale * Corresponding author. (ATNTS2004; Lourens et al., 2004). The dating method is purely E-mail address: [email protected] (N. Ciaranfi). based on the calibration of sedimentary cycles such as sapropels, 1040-6182/$ – see front matter Ó 2009 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2009.10.027 Please cite this article in press as: Ciaranfi, N., et al., Integrated stratigraphy and astronomical tuning of lower–middle Pleistocene..., Quaternary International (2009), doi:10.1016/j.quaint.2009.10.027 ARTICLE IN PRESS 2 N. Ciaranfi et al. / Quaternary International xxx (2009) 1–12 carbonate cycles, diatomite layers, combined with several (Cita and Castradori, 1995; Ciaranfi et al., 1997; Ciaranfi and D’Ales- geochemical and petrophysical climate sensitive proxies, to the sandro, 2005; Cita et al., 2006, 2008), although the absence of a clear computed time series of the quasi-periodic variations of Earth’s paleomagnetic signal in the succession prevents the recognition of orbit and axis (Hilgen, 1991a,b; Hilgen et al., 1995, 2000a,b, 2003; the Brunhes/Matuyama boundary, the primary criterion for the Hilgen and Krijgsman, 1999; Krijgsman et al., 1999; Langereis et al., definition of GSSP.This paper presents the astronomical calibration of 1997; Lourens et al., 1996a,b, 1998, 2001; Sierro et al., 2001, 2003; the composite Montalbano Jonico section based on the previously Lourens, 2004; Abels et al., 2005). This time scale provides precise developed benthic and planktonic stable oxygen isotope stratig- and accurate numerical ages, not only for the sedimentary cycles, raphy, together with new planktonic d18O data, additional biostrati- but also for calcareous plankton events and magnetic polarity graphical constraints and new tephrostratigraphic study of the reversals recorded in the tuned sections. Accordingly, all the middle volcaniclastic layers occurring in the studied record. to late Neogene stages are by now defined in tuned land-based marine sections in the Mediterranean region. The Pleistocene part 2. Study section of the ATNTS2004 is based on a few ODP Sites (964, 969 and 967) and piston cores (RC9-181, MD84641, KC01B, KC01), with the The lower–middle Pleistocene Montalbano Jonico composite exception of the Lower Pleistocene interval in which data from the section crops out in the Lucania Basin (Balduzzi et al.,1982), a minor land-based marine sequences of Vrica and Singa (Calabria, Italy) basin of Bradano Trough (Casnedi, 1988) between the Apennines were also included. The Vrica section includes the GSSP of the Chain to the west and the Apulia foreland eastward (Fig. 1A). It Pliocene–Pleistocene boundary (Aguirre and Pasini, 1985). At belongs to the argille subapennine unit (Azzaroli, 1968) and is present, the Calabrian Stage and the Lower/Middle and Middle/ about 450 m thick consisting of coarsening upwards deposits from Upper Pleistocene boundaries should be regarded as informal (Cita muddy clays to muddy sands and including nine volcaniclastic and Castradori, 1995; Cita et al., 2006, 2008). layers (V1–V9) (Fig. 2). Locally, some terraced marine deposits and The Montalbano Jonico composite section, cropping out in sandy-conglomerate bodies of continental origin lie horizontally on Southern Italy, due to its continuity and exposure condition, together the muddy succession (Ciaranfi et al., 2001). The whole section has with the available detailed integrated stratigraphy, has been been reconstructed in the field by means of selected stratigraphic proposed as the reference succession for the upper portion of Cala- sections including volcaniclastic layers, diagnostic macrobenthic brian Stage (Cita et al., 2008). The section can fill the gap between the assemblages and biostratigraphic data (Ciaranfi et al., 2001; top of Vrica section (according to Lourens et al., 1998 the top of Vrica D’Alessandro et al., 2003; Stefanelli, 2003; Maiorano et al., 2004). A section is directlyabove insolation cycles i-116) and the base of Ionian stratigraphical gap divides the Montalbano Jonico section into two informal Middle Pleistocene stage. Further, the section has been parts: the lower part, termed ‘‘Interval A’’ 168 m thick and the considered suitable for the selection of the Middle Pleistocene GSSP upper part, termed ‘‘Interval B’’ 280 m thick. A B Fig. 1. Location map of Montalbano Jonico section (A) and of Ocean Drilling Program sites cited in the present paper (B). Please cite this article in press as: Ciaranfi, N., et al., Integrated stratigraphy and astronomical tuning of lower–middle Pleistocene..., Quaternary International (2009), doi:10.1016/j.quaint.2009.10.027 ARTICLE IN PRESS N. Ciaranfi et al. / Quaternary International xxx (2009) 1–12 3 Fig. 2. Lithological sequence of Montalbano Jonico section with indication of a few volcaniclastic layers. The main results concerning stratigraphical data and paleo- 3. Methods environmental reconstruction are shown in Fig. 3. Several deep- ening–shallowing cycles forming a regressive succession and the 3.1. Stable Isotopes middle Pleistocene infill of Lucania Basin have been recognised based on micro- and macro-invertebrate benthic assemblages, Oxygen and carbon stable isotope analyses throughout the which mainly indicate changes in paleo-bathymetry from bathyal Montalbano Jonico