Stanley C. Finney

Three new Ordovician global stage names

Extensive work by the International Subcommission on OrdovicianStratigraphy (ISOS) has led to considerable progress in the establish-ment of a new chronostratigraphic classification of the OrdovicianSystem which now includes seven stages (Webby 1998; Finney 2005).However, until recently, only three of these global stages havebeen formally named and ratified by the International Commissionon Stratigraphy (ICS). These are the lower stage of the LowerOrdovician (Tremadocian or 1

GSSPs as International Geostandards and as Global Geoheritage

Abstract The International Commission on Stratigraphy (ICS) formally approves the chronostratigraphic units of the International Chronostratigraphic Chart that serve as the basis of the Geologic Time Scale. An essential part of this process is the definition of a Global Stratotype Section and Point (GSSP) that defines the lower boundary of each chronostratigraphic unit of Stage, Series, System, Erathem, and Eonthem rank. Once approved by the ICS and ratified by the International Union of Geological Sciences, each GSSP is an international geostandard, and it is marked and dedicated. It is imperative that GSSPs, once ratified, are preserved, protected and maintained for the purpose of future scientific study. Furthermore, each GSSP can serve as a local focal point of educational outreach that educates the public on the nature of the stratigraphic record and the marvels it reveals about Earth’s history. Preservation, protection, maintenance and education are best accomplished when a GSSP is located in a nature preserve as exemplified by the two GSSPs located in the Basque Coast UNESCO Global Geopark on the north coast of Spain.

87 Sr/ 86 Sr evidence from the epeiric Martin Ridge Basin for enhanced carbonate weathering during the Hirnantian

A pronounced positive δ13C excursion in the Hirnantian Age has been documented globally, reflecting large perturbations of carbon cycling in the Late Ordovician oceans. Increased organic-carbon burial or enhanced carbonate weathering during glacioeustatic sea-level regression has been proposed to account for this anomalous C-isotope excursion. To test the two competing hypotheses, we measured 87Sr/86Sr and δ13C of carbonates from the Copenhagen Canyon section in Nevada, USA. Our data reveal two rapid negative 87Sr/86Sr shifts that coincide with two prominent positive δ13C excursions and glacial advances. Numerical model simulations suggest that enhanced weathering of carbonates driven by glacio-eustatically controlled sea-level fall is required to produce the observed drops of 87Sr/86Sr and the coeval large positive δ13C excursions, possibly with or without increased organic carbon burial.