Inorganic carbon (IC) is a major component of the carbon cycle in coastal waters, but it is an understudied component. Tidal salt marsh soils are a reservoir of IC, as CaCO3. contributed by calcifying organisms like crabs, mollusks and foraminifera, whose shells are buried in the soil as it accumulates. In eastern Canada extensive areas of salt marsh have been drained for agriculture, causing a reduction of the soil pH and possibly dissolution CaCO3, yet there has been no study of the stocks or their changes with drainage. Sequential loss-on-ignition (LOI) is an inexpensive way to measure CaCO3 in soils but requires ~1 g of sample per replicate measurement. As this is a destructive process it may require more soil samples than may be available. We test a non-destructive method using X-ray fluorescence (XRF) to measure Ca concentrations as a proxy for CaCO3 concentrations. We compare Ca concentrations measured by XRF to the CaCO3 concentration determined by LOI over multiple depths in cores from different elevations (i.e., vegetation) zones in several salt marshes on the coast of eastern Canada. We eliminate the proportion of Ca associated with other lithogenic minerals by normalizing the Ca concentrations with corresponding Al concentrations. Results obtained by XRF after normalization are highly correlated (R2=0.87, P<0.05) with measurements of IC obtained by LOI.