Journal metrics

Journal metrics

  • IF value: indexed IF
    indexed
  • IF 5-year value: indexed IF 5-year indexed
  • CiteScore value: 0.79 CiteScore 0.79
  • SNIP value: 0.533 SNIP 0.533
  • SJR value: 0.255 SJR 0.255
  • IPP value: 1.70 IPP 1.70
  • h5-index value: 8 h5-index 8
  • Scimago H index value: 23 Scimago H index 23
Volume 36, issue 2 | Copyright
J. Micropalaeontol., 36, 137-152, 2016
https://doi.org/10.1144/jmpaleo2015-034
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

  07 Dec 2016

07 Dec 2016

Biostratigraphy and evolution of Miocene Discoaster spp. from IODP Site U1338 in the equatorial Pacific Ocean

Marina Ciummelli1, Isabella Raffi2, and Jan Backman3 Marina Ciummelli et al.
  • 1PetroStrat Ltd, Tan-y-Graig, Parc Caer Seion, Conwy LL32 8FA, UK
  • 2Dipartimento di Ingegneria e Geologia, Università ‘G. d’Annunzio’ di Chieti-Pescara, I-66013 Chieti Scalo, Italy
  • 3Department of Geological Sciences, Stockholm University, SE-106 91 Stockholm, Sweden

Keywords: Miocene, Discoaster spp., equatorial Pacific, five major morphogroups, abundance variations

Abstract. Assemblages of upper lower through upper Miocene Discoaster spp. have been quantified from Integrated Ocean Drilling Program (IODP) Site U1338 in the eastern equatorial Pacific Ocean. These assemblages can be grouped into five broad morphological categories: six-rayed with bifurcated ray tips, six-rayed with large central areas, six-rayed with pointed ray tips, five-rayed with bifurcated ray tips and five-rayed with pointed ray tips. Discoaster deflandrei dominates the assemblages prior to 15.8 Ma. The decline in abundance of D. deflandrei close to the early–middle Miocene boundary occurs together with the evolution of the D. variabilis group, including D. signus and D. exilis. Six-rayed discoasters having large central areas become a prominent member of the assemblages for a 400 ka interval in the late middle Miocene. Five- and six-rayed forms having pointed tips become prominent in the early late Miocene and show a strong antiphasing relationship with the D. variabilis group. Discoaster bellus completely dominates the Discoaster assemblages for a 400 ka interval in the middle late Miocene. Abundances of all discoasters, or discoasters at the species level, show only (surprisingly) weak correlations to carbonate contents or oxygen and carbon isotopes of bulk sediment when calculated over the entire sample interval.

Download & links
Publications Copernicus
Download
Citation
Share