GSSP for Bathonian Stage
Definition:
The base of the Bathonian Stage is defined at the base of limestone
bed RB071 in the Ravin du Bès Section, Bas-Auran area,
southern Subalpine Chains, France. The boundary coincides with the
first occurrence of the ammonites Gonolkites convergens and
Morphoceras parvum.
Location:
The GSSP of the Bathonian Stage is located in the Bas-Auran area, southern
Subalpine Chains, France, approximately 25 km SSE of Digne-les-Bains. The GSSP
is located at a latitude of 43°57'38"N and a longitude of
6°18'55"E.
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Sedimentology:
The GSSP succession is a cyclic marl-limestone alternation. In the
Bas-Auran area, Lower Bathonian deposits comprise black or gray
limestone beds alternating with marls. The Bajocian - Bathonian
Boundary is defined at the base of limestone bed RB071. These deposits
are relatively uniform mudstones to wackestones, with common
ammonoids, scarce sponges and very scarce nautiloids, brachiopods,
bivalves, belemnites, echinoids, crinoids and gastropods.
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Primary Markers:
Ammonites:
The boundary coincides with the first occurrrence of the ammonites
Gonolkites convergens and Morphoceras parvum.
Secondary Markers:
Nannofossils:
The FO of Watznaueria barnesiae (NJT11) was observed in sample
68a of earliest Bathonian age (Zigzag Zone). This event defines the
base of the Tethyan NJT11 Zone, comparable to most of the Boreal NJ11
Zone and NJ12a Subzone.
Correlation Events:
Ammonite FAD Gonolkites convergens (defines base of
Zigzagiceras zigzag Zone)
Other Locations around the World:
An auxiliary section for the Bathonian Stage is located in Cabo
Mondego, 40 km west of Coimbra, 7 km north of Figueira da Foz,
Portugal (40°11'18"N, 8°54'30"W). It provides complementary
data about
the ammonite succession and biochronostratigraphic subdivision of the
Sub- Mediterranean parvum Subzone and the Northwest European
convergens Subzone.
Notes on Derivation of Age:
Equal subzones scale Bajo-Bath-Callov
References:
Fernández-López, S. R., Pavia, G. Erba, E., Guiomar, M.,
Henriques, M. H.,
Lanza, R., Mangold, C., Morton, N., Olivero, D., and Tiraboschi, D., 2009. The
Global Boundary Stratotype Section and Point (GSSP) for base of the Bathonian
Stage (Middle Jurassic), Ravin du Bès Section, SE France. Episodes 32/4,
p. 222
- 248.
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