THE MONTE-DEL-CASINO SECTION (NORTHERN APENNINES, ITALY) - A POTENTIAL TORTONIAN MESSINIAN BOUNDARY STRATOTYPE/

Results are presented from a high-resolution integrated stratigraphic study of the Monte del Casino section, which is considered as a candid ate boundary stratotype section for the Tortonian/Messinian (T/M) boun dary. The section yields a good to excellent cyclostratigraphy, tephra stratigraphy and planktonic foraminiferal and nannofossil biostratigra phy, It can be correlated in detail to other Mediterranean sections us ing cyclostratigraphic patterns in combination with the planktonic for aminiferal biostratigraphy. These correlations indicate that the succe ssion of the Monte del Casino composite section is continuous in the T /M boundary interval and that all sedimentary cycles, volcanic ash lay ers and bio-events can be accurately dated by tuning the sedimentary c ycles to astronomical target curves. The quality of the paleomagnetic signal varies considerably throughout the section. A reliable magnetos tratigraphy cannot be established for the T/M boundary interval becaus e of a secondary magnetisation carried by iron sulphides, Cyclostratig raphic correlations indicate that discrepancies exist between the posi tion of the reversals recorded here and those found in earlier magneto stratigraphic studies. Comparison of Ar-40/Ar-39 ages of ash layers wi th their astronomical ages, show that biotite ages give a good approxi mation of the age of the section, but are not suitable for high-resolu tion chronology. Despite these short-comings the Monte del Casino sect ion remains a candidate to define the T/M boundary, but its qualities should be critically weighted against those of other sections. (C) 199 7 Elsevier Science B.V.