Publication Date:
2021-07-14
Description:
The 91.15 m thick St. Thomas section belongs to the Middle Globigerina Limestone, which is the intermediate
member of the Globigerina Limestone Formation, and crops out along the eastern cliff of the Delimara Peninsula
(the south-eastern part ofMalta Island). The sedimentary record is composed of alternating calcareous marls and
marly limestones with subordinated prominent bioturbated indurated limestones that are deposited in a pelagic
environment.
For the first time paleomagnetic analyses of a Burdigalian succession have provided reliable data that allow the
identification of five magnetozones that have been correlated to the Astronomically Tuned Neogene Time
Scale, spanning the Early Miocene C6n–C5Dn interval. Calcareous plankton quantitative analyses integrated
with paleomagnetic analyses, allowed us to identify and date several bioevents that have great potential for
Mediterranean and extra-Mediterranean correlations in the interval between ~19.7 and ~17.2 Ma. In particular,
the complete distributional range of the calcareous nannofossil Sphenolithus belemnos has been recorded as
follows: the First Occurrence (FO) at 19.12 Ma, the First Common Occurrence (FCO) at 19.05 Ma, the Last
Common Occurrence (LCO) at 18.44 Ma, and the Last Occurrence (LO) at 18.02 Ma. In addition, the FO and the
FCO of Sphenolithus heteromorphus have been documented at 18.29 Ma and at 17.99 Ma, respectively. A new
paracme interval in the lower part of the range of this species is described between 17.56 and 17.31 Ma.
Concerning the planktonic Foraminifera, the main bioevents are the Common Interval top of Paragloborotalia
siakensis at 19.55 Ma, a Common Interval of Globoquadrina dehiscens between 19.34 and 18.48 Ma, the
Globigerinoides subquadratus FO at 18.43 Ma, and the onset of an acme interval of Paragloborotalia acrostoma
that changes its coiling from random to prevalently sinistral at the same time, at 18.40 Ma. These new biostratigraphic
data allowed us to place the succession in the standard Mediterranean calcareous plankton zonal
schemes and to make some amendments to these schemes. The FCO of S. belemnos was revealed a more reliable
marker than its FO for the base of the MNN3a Zone.With regard to the planktonic Foraminifera, the P. acrostoma
AB-r/s has been used as a subzonal marker of the G. dehiscens/Catapsydrax dissimilis Zone, which now comprises
three subzones instead of two.
The deep marine paleoenvironmental setting, the excellent outcrops and the recognition of a continuous succession
of bio-magnetostratigraphic events suggest that the St. Thomas section should be considered as a reference section
for the lower Burdigalian of theMediterranean area and for future studies in the definition of the Burdigalian GSSP.
Description:
Published
Description:
66-89
Description:
1A. Geomagnetismo e Paleomagnetismo
Description:
JCR Journal
Description:
restricted
Keywords:
Mediterranean; Early Miocene; Calcareous nannofossils; Planktonic Foraminifera; Magnetostratigraphy
;
04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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