Quantitative 3-dimensional Image Analysis of Mineral Surface Modifications—Chemical, Mechanical and Biological

Abstract

Three principally different mechanisms contribute to the wear-down process of mineral aggregates in sedimentary environments: (1) mechanical abrasion by forces of wind and water and by floating or saltating neighbouring grains, (2) chemical attack and dissolution by fluids, and (3) physical bioerosion and chemical biocorrosion. It is however, difficult to attribute the specific surface changes to specific environments and processes. Quartz sand grains from subaerial and subaquatic environments were analysed by atomic force microscopy (AFM) for traces of natural and experimental aeolian, aquatic and biological wear-down processes. Quantitative topographical parameters of surface alterations were extracted from topography data by non-linear methods derived from digital image analysis. These parameters were examined by multivariate statistic, yielding three well-distinguishable groups. Morphological surface alterations dominated by subaerial, subaquatic and by biological impact could be differentiated. The method may also be used for the detection of aeolian, subaquatic, and biological modification of sedimentary grains and rock surfaces in extraterrestrial environments, and for assessment of environmental damage on monuments and buildings.

Keywords:

• sediment grain corrosion
• chemical grain pitting
• biolological grain pitting
• aquatic grain corrosion
• biopitting
• weathering
• surface analysis
• nano-structure of grain and mineral surfaces

Acknowledgments

The authors acknowledge support by DFG grants Kr 333/30-1, Go 897/2-1,2 and BMBF grant 03G0709A.