USING COSMOGENIC 26AL AND 36CL BASIN-AVERAGED EROSION RATES IN CARBONATES TO QUANTIFY RATES OF TECTONIC PROCESSES AND THE VARIATIONS OF PROPORTIONS OF CHEMICAL WEATHERING AND MECHANICAL DENUDATION IN LONG-TERM DENUDATION PROCESS: A CASE STUDY IN OMAN

The preliminary results of this study of the stream analysis of the wadies at the northeastern watershed at Oman show variations in steepness above and below knickzones that are located at same drainage area of 10⁷ m². In uniform lithology and climate at the watershed, the steepness index (ksn) scaled positively with both rock uplift rate and erosion rate and the denudation rates scale positively with hillslope gradient, stream gradient, and rock uplift rate. While this study attempts to quantify the erosional response to tectonic forcing using ³⁶Cl as a widely used nuclides in carbonates, the nuclide ²⁶Al is used as a proof of concept that will opens the opportunity to apply multi-nuclide approaches to non-siliciclastic systems. The cosmogenically determined basin average erosion rates from the “adjusted” channels is compared with rock uplift rate determined from the ages and elevation of marine terraces present at the same watershed.

Given mean annual precipitation of 90mm/yr and high temperature at the watershed, we predicted carbonate solution potential is low, and the remnants of mechanical erosion reside where dissolution was insufficient to remove them. To test the dominant control of denudation, the mechanical long-term denudation rate using 36Cl basin-averaged erosion rate below knickzones is compared with the short-term chemical weathering from wadies water sample. Given these data, we are able to assess a relationship between elevation, mean annual precipitation, mechanical erosion rate, and carbonate dissolution. Also, the measured rated of mechanical denudation in arid carbonate watershed might follow a similar scaling relationships with channel and hillslope gradient as observed in silicate bearing watersheds.