Biozonation and biochronology of Miocene through Pleistocene calcareous nannofossils from low and middle latitudes

Abstract

Abstract. Calcareous nannofossils are widely used in Cenozoic marine biostratigraphy. At present, the two most widely used calcareous nannofossil biozonations were established approximately 40 years ago. These were derived from marine land sections and Deep Sea Drilling Project rotary cored sediments. Over nearly three decades, we have generated Miocene through Pleistocene calcareous nannofossil data from deep sea sediments in low and middle latitude regions. The sediments used here have been mostly recovered using the advanced piston coring technique, generating less core disturbance and complete recovery via multiple penetration of the sediment column at single sites. A consistent trait in our work on calcareous nannofossil biostratigraphy has been to use semi-quantiative methods in combination with short sample distances, close enough to capture the details of the abundance behaviour of individual calcareous nannofossil taxa. Such data represent the foundation of the new biozonation presented here, which still partly relies on the pioneering work presented by Erlend Martini and David Bukry about 40 years ago. A key aim here has been to employ a limited set of selected biohorizons for the purpose of establishing a relatively coarsely resolved and stable biozonation. We present 31 biozones using a new code system: CNM1-CNM20; Calcareous Nannofossil Miocene biozones 1 through 20. CNPL1-CNPL11; Calcareous Nannofossil Plio-Pleistocene biozones 1 through 11. As the new biozonation encompasses 23 million years, the average biozone resolution becomes 0.74 million years, ranging from 0.15 to 2.20 million years. A single biohorizon is used for the definition of each biozone boundary. Auxiliary markers are avoided, as well as subzones, in order to maintain stability to the new biozonation. Virtually every biozone holds one or several additional biohorizons. These, together with all biozone boundary markers, are assigned age estimates derived chiefly from astronomically tuned cyclostratigraphies.

Data report: a revised biomagnetostratigraphic age model for Site U1338, IODP Expedition 320/321

“…Base Amaurolithus spp. seems to appear at ~0.3 My earlier (7.7 Ma rather than 7.4 Ma) to the Site U1338 region compared with its calibrated first appearance from both the western equatorial Atlantic and two sites in the eastern equatorial Pacific (Backman et al, 2012). In Monte dei Corvi section on the Adriatic Sea coast, base Amaurolithus spp.…”

“…Age estimates for equatorial Pacific diatom biohorizons were synthesized by Barron (1992) and are here converted from the timescale by Berggren et al (1985) to that by Lourens et al (2004). Age estimates for calcareous nannofossils mainly represent astronomically tuned calibrations from the western equatorial Atlantic (Backman et al, 2012).…”

“…The short overlap between two nannofossil biohorizons at 15.69 Ma (Discoaster deflandrei decreases to <30% of the total Discoaster assemblage) and 15.73 Ma (base Discoaster signus) indicates that CP10 can be confidently placed at the latter biohorizon. The base of common Sphenolithus heteromorphus provides CP11, which has a consistent first common occurrence in Chron C5Dr in the Indian Ocean, Atlantic Ocean, and Mediterranean Sea (Backman et al, 1990(Backman et al, , 2012Di Stefano et al, 2015).…”

Fossil whale barnacles from the lower Pleistocene of Sicily shed light on the coeval Mediterranean cetacean fauna

“…using a polarized light microscope on a smear-slide prepared from the sample, following standard techniques (BOWN & YOUNG, 1998 TAN, 1927, emend. BRAMLETTE & RIEDEL, 1954, allowed us to attribute the assemblage detected in the analyzed samples to the lower Pleistocene Mediterranean Neogene Nannoplankton (= MNN) zone 19a of RIO et al (1990), corresponding to the Calcareous Nannofossil Plio-Pleistocene (= CNPL) zone 7 of the more recent Neogene and Quaternary biozonation of BACKMAN et al (2012). The bioevents that bound this zone have recently been calibrated by BACKMAN et al (2012) to 1.93 Ma and 1.71 Ma; consequently, the analyzed samples should be regarded as latest Gelasian to earliest Calabrian (i.e., early Santernian, following the 'Italian Marine Stages' regional scheme of GIBBARD & COHEN, 2008).…”

“…BRAMLETTE & RIEDEL, 1954, allowed us to attribute the assemblage detected in the analyzed samples to the lower Pleistocene Mediterranean Neogene Nannoplankton (= MNN) zone 19a of RIO et al (1990), corresponding to the Calcareous Nannofossil Plio-Pleistocene (= CNPL) zone 7 of the more recent Neogene and Quaternary biozonation of BACKMAN et al (2012). The bioevents that bound this zone have recently been calibrated by BACKMAN et al (2012) to 1.93 Ma and 1.71 Ma; consequently, the analyzed samples should be regarded as latest Gelasian to earliest Calabrian (i.e., early Santernian, following the 'Italian Marine Stages' regional scheme of GIBBARD & COHEN, 2008). Our biostratigraphic results partially contradict those of RUGGIERI (1976( , 1987( ) and CIPOLLA (1978, who referred to the deposits exposed at Cinisi as middle Calabrian (i.e., Emilian substage of the 'Italian Marine Stages' regional scheme) while evoking the persistence or reappearance of some 'Pliocene' (i.e., pre-Emilian) taxa.…”