A VOLUME-BASED APPROACH TO REEF PRODUCTIVITY AND SUBMARINE EROSION RATES - A CASE-STUDY OF A MIDDLE TRIASSIC REEF MARGIN (LATEMAR BUILDUP, NORTHERN ITALY)

Reef productivity and submarine erosion rates for the Middle Triassic Latemar reef margin are estimated from debris volumes produced over ti me intervals of 1.5 to 6 Ma. This direct approach is applicable becaus e the buildup geometry is simple, the sediment source area is limited (>95% of talus blocks are reef boundstone), and the platform section p rovides temporal control. The buildup geometry is simulated as a trunc ated cone with corrections for toe-of-slope geometry and 40% depositio nal porosity of slope breccias. Reef productivity per meter of perimet er was 5.0-18.9 m(3)/m/ka; corresponding erosion rates were 4.4-18.2 m (3)/m/ka. Rate estimates of productivity and erosion demonstrate redep osition of approximately 85% of the reef. Productivity and erosion rat es averaged across the 30 m wide preserved reef are 166-629 Bubnoffs a nd 146-606 Bubnoffs, respectively. Vertical accumulation rates (20-125 Bubnoffs) strongly underestimate reef productivity. Alternative time scales increase calculated rates such that Triassic reef productivity matches Holocene carbonate accumulation rates.