PRELIMINARY OPTIMIZATION OF THE AQUEOUS FORMIC-ACID SOLUTION FORMULATION AND DISSOLUTION PROCEDURES USED IN THE REMOVAL OF FOSSIL VERTEBRATE MATERIAL FOR CARBONATE ROCKS

Paleontological literature contains few detailed procedures for acid preparation of macrofossils. While researchers have reported comprehensive methods for the safe extraction of microscopic conodont elements from carbonates, they virtually ignore the extraction of macrofossils such as teeth, scales, and other boney remains. Many times workers identify the acid reagent used, but fail to describe the acid-to-buffer ratios or step-by-step procedures employed. In the past, researchers have utilized a 10% acetic acid solution. While this system is safe, it is not efficient and the process is relatively slow. A more efficient system uses a 10% aqueous formic acid solution that is typically buffered in situ with calcium carbonate. This acid is stronger, has a comparatively short dissolution time, and requires much less volume with regard to mass of sample dissolved. However, it does have its drawbacks. Buffering an acid raises the solution pH considerably, thus diminishing the acid solution’s ability to break down the carbonate matrix. The formation of calcium formate coats the remaining carbonate medium, risking damage to fossil material and effectively quenching the reaction between acid and carbonate matrix. The purpose of this study is to investigate the optimization of the formic acid dissolution procedure by: (1) comparing the efficacy of buffered formic acid solution in contrast to unbuffered formic acid solution; (2) preventing formation of calcium formate crystals and increased reaction rate via continual heating and stirring of the acid solution; and (3) determining the effective length of time the acid solution retains the ability to dissolve carbonate matrix. Results found no statistical difference between the number of micro- and macrofossil returns in buffered and unbuffered solutions. Carbonate matrix breakdown was most effective when the acid solution was heated and stirred, with no calcium formate crystal formation noted. Analysis of a possible correlation between pH and carbon dioxide levels, when stirring and heating was applied, suggest the effectiveness of the acid solution dropped exponentially, reaching an inert state after approximately two days.