Detecting compositional, spatial, and temporal attributes of glaucony: a tool for provenance research

Abstract

A reliable interpretation of glaucony-bearing units requires the characterization of compositional, spatial, and temporal attributes of glaucony. The criteria that can readily determine the differentiation of the various types of glaucony (autochthonous, parautochthonous or allochthonous intrasequential, and detrital or allochthonous extrasequential) are discussed in detail.Autochthonous vs allochthonous glaucony may be often detected on the basis of detailed sedimentological investigations, including facies interpretation of glaucony-bearing deposits and careful examination of spatial distribution of glaucony. Textural and morphological features, although generally not diagnostic on their own, provide a significant contribution to glaucony interpretation.The distinction between parautochthonous and detrital glaucony can be sometimes performed by radiometric dating; more commonly, it requires that compositional attributes of glaucony be matched against those of putative sources. Glauconies from distinct parent rocks generally have different maturity and carry unique geochemical and mineralogical fingerprints that may contribute definitive data for provenance research.Previous work on glaucony and examples from units formed in tectonically stable areas (Cretaceous/Eocene deposits of Paris Basin and Hampshire Basin) and active tectonic basin settings (Miocene strata of southern Alps and northern Apennines) provide the opportunity to discuss the validity of the proposed criteria across different structural domains and emphasize the need for an integrated approach to the study of glaucony.