Results of high-resolution integrated stratigraphic studies (calcareous plankton andmagnetostratigraphy) of three Mediterranean sections (La Vedova in Central Italy, ContradaPesciarello in Sicily and St. Peter’s Pool in Malta) and one deep-sea core from the mid-latitude NorthAtlantic (DSDP Hole 608) are here synthesized. They are compared with those of previously studieddeep marine sections in the Mediterranean including the historical stratotype, with the aim to select themost suitable section and criterion to define the Langhian GSSP (Global Stratotype Section and Point). This study significantly improves the existing magnetobiostratigraphic framework for the upperBurdigalian-lower Langhian and opens new perspectives for defining the Langhian GSSP.An extensive review of the first stages of the Globigerinoides-Praeorbulina evolutionary lineagepointed out that the Praeorbulina datum, historically used (and/or suggested) to approximate the baseof the Langhian, coincides with the First Occurrence (FO) of P. glomerosa curva instead of P. sicanawhich is here included in the genus Globigerinoides. The FO of P. glomerosa curva occurs close tothe C5Br/C5Bn.2n reversal boundary. As a consequence, the two recommended guiding criteria torecognize the base of the Langhian, i.e. the Praeorbulina datum and the top of Chron C5Cn.1n, cannot be applied together, as these two events differ in age by ~740 kyr. The selection of either of thesetwo criteria will imply a different duration for the Langhian: relatively short, in case the FO of P.glomerosa curva is selected, or longer and probably more acceptable, in case the top of ChronC5Cn.1n is selected.The primary calcareous plankton biohorizons which, according to our data, appoximate the top ofChron C5Cn.1n, are the Last Common Occurrence (LCO) of the calcareous nannofossilHelicosphaera ampliaperta and the LCO of the planktonic foraminifer Paragloborotalia bella. Othercalcareous plankton events have been recorded close to the same magnetic reversal, such as a shortinflux of H. ampliaperta (Ia1) and the Paragloborotalia siakensis Acme0. The P. siakensis Acmea End(AaE) and the Sphenolithus heteromorphus Paracme End (PE) represent the primary planktonbiohorizons associated with the P. glomerosa curva FO.Two of the three studied Mediterranean sections (La Vedova and St. Peter’s Pool), each from differentpoint of view, are potentially suitable to be proposed as candidates for the definition of the LanghianGSSP. Yet, further studies on stable isotope stratigraphy and cyclostratigraphy, including astronomicaltuning are necessary before the most suitable section and guiding criterion can be selected.
|Titolo:||High-resolution integrated stratigraphy of the upper Burdigalian-lower Langhian in the Mediterranean: the Langhian historical stratotype and new candidate sections for defining its GSSP|
|Data di pubblicazione:||2011|
|Appare nelle tipologie:||1.1 Articolo in rivista|