GSSP for Serravallian Stage
Definition:
The base of the Serravallian Stage is defined at the base of the Blue Clay Formation (i.e. top of the "transitional" bed of the uppermost Globigerina Limestone) in the Ras il Pellegrin Section, Fomm Ir-Rih Bay, Malta, Europe. The GSSP coincides with the end of the major Mi-3b global cooling step in the oxygen isotopes and reflects a major increase in Antarctic ice volume. The GSSP level has an astronomical age of 13.82 Ma.
Location:
The Ras il Pellegrin section is located some 20 km west of Valetta town and exposed in coastal cliffs along the Fomm Ir-Rih Bay on the west coast of Malta at a latitude of 35°54’50" North, and a longitude of 14°20’10" East.
The Ras il Pellegrin section is located in the SW facing cliffs on the NE side of Fomm Ir-Rih Bay. The section contains the middle Globigerina Limestone up to the Uper Coralline Limestone. A transitional bed separates the yellowish marly limestones of the Globigerina Limestone from the softer grayish clayey marls of the Blue Clay. The Blue Clay reaches a thickness of less than 70m. It has a distinct pattern of alternating homogeneous grey and white coloured marls. The GSSP is at the base of the Blue Clay Formation (i.e. top of the "transitional" bed of the uppermost Globigerina Limestone).
Primary Markers:
Oxygen IsotopesThe GSSP coincides with the end of the major Mi-3b global cooling step in the oxygen isotopes and reflects a major increase in Antarctic ice volume.
Secondary Markers:
Foraminifera:The GSSP is 0.5m below the acme end of Globigerina cf. quinqueloba.
Nannoplankton: The GSSP slightly predates the L(C)O of the calcareous nannofossil Sphenolithus heteromorphus, dated astronomically at 13.654 Ma, and falls within the younger part of Chron C5ACn. The GSSP postdates the FCO of Helicosphaera walbersdorfensis.
Paleomagnetics: The formation boundary between the Globigerina Limestone and the Blue Clay and therefore the Serravallian GSSP falls within Chron C5ACn.
Correlation Events:
Oxygen-isotopic event (global cooling episode) Mi3b; near calcareous nannofossil LAD ofSphenolithus heteromorphus
Other Locations around the World:
The FCO of Helicosphaera walbersdorfensis is considered a reliable biostratigraphic marker event of regional importance for the Mediterranean middle Miocene. In the low-latitude open ocean the calcareous nannofossil events Sphenolithus. heteromorphus and Cyclicargolithus floridanus LCOs occur above the oxygen isotope event Mi-3b as recorded in the Mediterranean, although the astronomical age for the S. heteromorphus L(C)O seems slightly younger at Ceara Rise (13.523 Ma; Backman and Raffi, 1997) than in the Mediterranean (13.654 Ma; Abels et al., 2005). The GSSP corresponds approximately to the Barstovian 2 to 3 Subage boundary in North America (Woodburne and Swisher, 1995; Alroy, 2002). The boundary falls within the younger part of Chron C5ACn (Fig. 9) (Abels et al., 2005) and supposedly coincides with sequence boundary TB2.5.
Notes on Derivation of Age:
Astronomical cycles in sediments
References:
Abels, H.A., F. J. Hilgen, W. Krijgsman, R. W. Kruk, I. Raffi, E. Turco, and W. J. Zachariasse, 2005. Long-period orbital control on middle Miocene global cooling: Integrated stratigraphy and astronomical tuning of the Blue Clay Formation on Malta. Paleoceanography, 20, PA4012, doi: 10.1029/2004PA001129.
Backman, J., and I. Raffi, 1997. Calibration of Miocene nannofossil events to orbitally-tuned cyclostratigraphies from Ceara Rise. Proc. ODP, Sci. Res., 154, 83-99.