GSSP for Gelasian Stage
Definition:The base of the Gelasian Stage is defined as the base of the marly layer overlying sapropel MPRS 250, located at 62m in Monte San Nicola section, Italy. The astronomical age of sapropel MPRS 250 (mid-point), corresponding to precessional cycle 250 from the present, is 2.588 Ma, which can be assumed as the age of the boundary.
Sedimentology:The lower 36m of the section are constituted by rhythmically bedded marls and limestones of the Trubi Formation, transitionally grading upward into marly-silty Monte Narbonne Formation. The Monte Narbonne Formation is characterized by brownish-red laminated intervals (sapropels) and by brownish non-laminated manganesiferous levels. Both are important for regional correlations; the sapropels are an important tool for astronomical calibrations.
The depositional environment for the boundary is inferred to be a slope-basin setting with water depth ranging from 500 to 1000m.
Primary Markers:In the boundary interval a cluster of six sapropel or manganesiferous levels is recognized and correlated to coeval sections in Sicily, Calabria and Northern Italy. The single sapropels of this cluster have been coded as the Mediterranean Precession Related Sapropels (MPRS) and linked to the corresponding precessional cycle. The base of the Gelasian Stage is defined as the base of the marly layer overlying sapropel MPRS 250, According to Rio et al. (1998) the astronomical age of sapropel MPRS 250 (mid-point), is 2.588 Ma, which "can be assumed as the age of the boundary".
The section spans the interval from the upper part of the Gilbert Chron (C2Ar) to the Matuyama Chron above the Olduvai Subchron (C1r). The Gauss/Matuyama boundary is clearly detectable and located at 1m below the GSSP.
The last occurrence of Discoaster pentaradiatus occurs in most low and mid-latitude areas close to isotopic stage 99, some 80kyrs above the boundary.
Correlation Events:Magnetic -- Matuyama/Gauss boundary (C2r/C2An) is 1m below GSSP. GSSP level is within Marine Isotope Stage 103.
Notes on Derivation of Age:Astronomical cycles in sediments
Additional Comments:The base of the Quaternary System/Period, and thus the Neogene-Quaternary boundary, is formally defined by the Monte San Nicola GSSP and thus is coincident with the bases of the Pleistocene and Gelasian. The Gelasian Stage/Age was transferred from the Pliocene Series/Epoch to the Pleistocene. Ratified by IUGS on 29 June 2009
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