Publication Date:
2020-11-16
Description:
The Gorrondatxe section, a prospective Lutetian Global Stratotype Section and Point
(GSSP), has recently been used as the master reference section to reassess the correlation
between Eocene magnetostratigraphic and calcareous planktonic biostratigraphic
scales. However, the exact calibration of some events remained ill defined, as they were thought to be missing in Gorrondatxe due to a fault. The most important missing
events were the first occurrence of the planktonic foraminifera Turborotalia frontosa
and the C22n/C21r chron boundary. Either might be a reliable correlation criterion for
the Ypresian/Lutetian boundary, as both approach the age of the original Lutetian
Stratotype. New studies allowed the identification of the former event 9 m above the Gorrondatxe fault, within magnetic polarity Chron C21r and calcareous nannofossil Zone CP12a. Distinctive test features that characterize the most primitive morphotype of T. frontosa are described. Despite the high turbidite content, recurrent pelagic limestone–marl couplets and bundles occur, whose formation was driven by precession and eccentricity astronomical cycles. The first occurrence of T. frontosa
was found 27 couplets and 5.5 bundles (60 m) below the first occurrence of the calcareous nannofossil Blackites inflatus, which is dated at 48 Ma. Hence, the age of the first occurrence of T. frontosa is estimated at 48.55 Ma, confirming that it is the most suitable planktonic foraminiferal correlation criterion for the Ypresian/Lutetian boundary. These results show that the stratigraphic interval missing due to the Gorrondatxe fault cannot be greater than a few metres and reinforce the value of this section as a prospective Lutetian GSSP.
Description:
Published
Description:
255-264
Description:
1A. Geomagnetismo e Paleomagnetismo
Description:
JCR Journal
Description:
reserved
Keywords:
cyclostratigraphy
;
Eocene
;
GSSP
;
Gorrondatxe
;
Lutetian
;
planktonic foraminifer
;
Turborotalia frontosa
;
Ypresian
;
04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy
;
04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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