GSSP for Selandian Stage
Definition:
The base of the Selandian Stage is defined in the sea-cliff along the
main beach of the coastal town Zumaia, Basque Country, northern Spain.
The GSSP is at the base of the Itzurun Formation about 49m above the
Cretaceous/Paleogene boundary. The best event for global marine
correlation is the second radiation of the fasciculith group of
calcareous nannofossils, occurring from slightly below to 1.1 m above
the GSSP. The marker species for the base of nannofossil Zone NP5
(Fasciculithus tympaniformis) occurs 1.1m above the GSSP. The
GSSP level is interpreted to be coincident with a widespread rapid
sea-level fall, and to be 30 precession cycles (~630 kyr) above the
top of magnetic polarity Chron 27n.
Location:
The GSSP of the Selandian Stage is located along the main beach, of the coastal
town Zumaia, Basque Country, northern Spain at a latitude of 43° 17' 57.1"N,
and
a longitude of 02° 15' 39.6"W. The GSSP for the Selandian is about 49m above
the
Cretaceous/ Paleogene boundary, equivalent to the base of the marls overlying
the uppermost limestone bed of the ca. 10 meters of limestone - marl couplets in
the upper part of the Aitzgorri Limestone Formation.
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Sedimentology:
The upper 10m of the Aitzgorri Limestone Formation are dominated by
limestones with marl intercalations. The overlying Itzurun Formation
consists of greyish marlstones, however the lower 2.85 m of marls and
marlstones have a reddish color. The GSSP is defined at the abrupt
lithological change between the two formations.
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Primary Markers:
The base of the Selandian corresponds to the second radiation of the
calcareous nannofossil group, the fasciculiths. Species, such as
Fasciculithus ulii, F. billii, F. janii, F. involutus, F.
pileatus and F. tympaniformis have their FAD in the
interval from a few centimeters below to 1.1 meter above the GSSP.
The marker species for the base of nannofossil Zone NP5
(Fasciculithus tympaniformis) occurs 1.1m above the GSSP.
Secondary Markers:
The GSSP occurs 30 precession cycles (630kyr) above the top of
magnetochron C27n.
Correlation Events:
Onset of a carbon isotope shift and sea-level drop, 30 precession
cycles (~630 kyr) above the top of magnetic polarity Chron 27n
Notes on Derivation of Age:
Astronomical cycles in sediments scaled from base Paleocene, using magnetic
polarity chronozone placement of C26r
References:
Schmitz, B., Pujalte, V., Molina, E., Monechi, S., Orue-Etxebarria, X., Speijer,
R.P., Alegret, L., Apellaniz, E., Arenillas, I., Aubry, M-P., Baceta, J.I.,
Berggren, W.A., Bernaola, G., Caballero, F., Clemmensen, A., Dinarès-Turell, J.,
Dupuis, C., Heilmann-Clausen, C., Hilario Orús, A., Knox, R., MartÃn-Rubio, M.,
Ortiz, S., Payros, A., Petrizzo M.R., von Salis, K., Sprong, J., Steurbaut, E.,
& Thomsen, E., 2011. The Global Stratotype Sections and Points for the bases of
the Selandian (Middle Paleocene) and Thanetian (Upper Paleocene) stages at
Zumaia Spain. Episodes 34/4, p. 220-243.
