Abstract: A Volume-Based Approach to Submarine Carbonate Erosion Rates: A Case Study of a Middle Triassic Reef Margin (Latemar Buildup, Northern Italy)

Mark T. Harris

Submarine erosion rates for the Middle Triassic Latemar reef margin are estimated from foreslope debris volumes. The buildup consists of flat-lying platform strata surrounded by a narrow (25 m wide) reef margin. Steeply dipping foreslope talus piles, derived from the reef margin, flank the platform and pass into basin deposits. Previous workers estimated durations for stacked platform facies at 1.5 to 6 million years. Outcrop relations tightly constrain buildup geometry for these intervals.

Debris volume and erosion rates may be calculated because the buildup geometry is simple, the sediment source area is limited, redeposited sediment volumes can be calculated, and the platform section provides temporal control. The buildup geometry is simulated as a truncated cone with corrections for basinal sediments and slope breccia porosity (35%).

The erosion rate per meter of margin front is 4.7 to 10.9³/m/ka. The vertical erosion rate per preserved reef area is 0.435-0.190 m/ka (or 435-190 Budnoffs; 1 Budnoff=mm/ka=m/m.y.). These rates provide an initial guide for modeling of carbonate platform geometry from sediment dynamics. They are calculated for temporal durations of 1.5 to 6 million years, thus avoiding problems associated with extrapolating short-term rates over geological time scales. Curiously, the lowest rate corresponds to an interval of decreasing platform accommodation.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994