GLAUCONY AND SEQUENCE STRATIGRAPHY - A CONCEPTUAL-FRAMEWORK OF DISTRIBUTION IN SILICICLASTIC SEQUENCES

Detailed analysis of recent literature on glaucony and selected case s tudies (Eocene, Isle of Wight; Miocene, northern Apennines) shows that the presence of glaucony alone is not diagnostic of a specific system s tract of a depositional sequence, A reliable sequence stratigraphic interpretation of glaucony bearing units requires additional informati on on glaucony, including: (1) spatial distribution, (2) maturity (dis tinction between nascent, slightly evolved, evolved, and highly evolve d glaucony), and (3) genetic attributes (differentiation of autochthon ous from allochthonous, and intrasequential from extrasequential glauc ony). Autochthonous glaucony is common at various stratigraphic levels in the transgressive systems tract (TST) and the lower highstand syst ems tract (HST), showing an upward increase (TST) and then decrease (H ST) in abundance and maturity, The condensed section can be distinguis hed from the overlying and underlying deposits by the higher concentra tion and maturity of glaucony, Allochthonous intrasequential (parautoc hthonous) glaucony can be present in the entire TST, HST, and lowstand systems tract (LST), generally showing lower concentration and maturi ty than its autochthonous counterpart, Al lochthonous extrasequential (detrital) glaucony is present mainly in the LST, its concentration an d composition depending on the characteristics of the source horizon, The association between autochthonous and allochthonous (intrasequenti al and extrasequential) glaucony commonly exists in the LST and in the lower TST.