Anita É. Csoma¹, Robert H. Goldstein¹, Andrea Mindszenty², Lucia Simone³

(1) The University of Kansas, Lawrence, KS
(2) Eötvös L. University, Budapest, Hungary
(3) University Federico II, Napoli, Italy

ABSTRACT: Diagenesis of Platform Strata as a Tool to Predict Downslope Depositional Sequences, Monte Camposauro, Italy

Diagenetic study of Albian/Cenomanian limestones of Monte Camposauro, revealed three possible sea level oscillations, represented by diagenesis associated with a single Cenomanian/Turonian unconformity. After deposition and micritization, aragonitic shells were dissolved and filled with internal sediment and bladed calcite with fluid inclusion Tm ice of -0.6°C, d 13C of -2.94o/oo and d 18O of -3.75o/oo (VPDB), indicating precipitation in a meteoric-marine mixing zone. Afterward, meteoric waters produced karstic cavities. These were filled with alternating peloidal marine sediments, aragonite rays (d 13C -2.26o/oo, d 18O 0.38o/oo) and radiaxial fibrous calcite (d 13C 0.06o/oo, d 18O -2.05o/oo), indicating a return to marine conditions and a possible relative rise in sea level. Later, another generation of cavities and collapse features, filled by bauxite fragments, internal sediments and carbonate clasts, indicates a return to meteoric vadose conditions, probably coincident with a minor sea-level drop. Fibrous calcite with d 13C of -4.45o/oo and d 18O of -7.33o/oo forms next. The stable isotope signature suggests meteoric origin. The remaining porosity is filled by partially recrystallized radiaxial calcite with Tm ice of -1.7°C to -1.3°C, followed by calcite overgrowth with Tm ice of -1.3°C to 0.0°C, and finally by mosaic calcite with Tm ice of - 0.2°C to 0.0°C. This progression indicates a transition from marine domination to meteoric domination, consistent with another relative rise and fall in sea level. The paragenesis is followed by deposition of marine Turonian sediments above the unconformity.

This diagenetic record of sea level oscillations, not recorded by deposition on the platform top, may help to predict depositional sequences downslope.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado