Abstract: Deformation Mechanisms and Resultant Strains in Folded Quartz Sandstones, a Field and Laboratory Based Study, Southern Appalachians

The purpose of this research is to determine the deformation mechanisms and resultant strains associated with folding of a series of quartz sandstone beds in the southern Appalachians. In recent years considerable advances have been made in our knowledge of the general buckling mechanisms by which folds initiate and grow with progressive deformation using both numerical and analogue modeling techniques. However these laboratory studies have not taken into account the potential grain-scale deformation mechanisms (e.g. brittle fracture, pressure solution etc.) by which strains may accumulate in growing folds. This is important from both applied and academic viewpoints because partitioning of finite strains into different domains within the limbs and hinge regions of a fold can lead to important variations in both local rock properties (porosity, permeability) and the driving forces for metamorphic reactions. Using three previously identified and well exposed folds (amplitude and wavelengths ranging between 10 and 20 meters) I propose to make a detailed study of the relationships between position within the fold structures and: i) operative deformation mechanisms indicated by diagnostic microstructures and, ii) finite strains associated with these deformation mechanisms. These folds have been chosen for detailed analysis because previous studies indicate that they are located in a region which has only been subjected to one major phase of Alleghanian deformation and therefore have not been penetratively overprinted by later structural events. Research will include field analysis and sample collection followed by thin section-based analysis of the deformation mechanisms and associated strains. 

AAPG Search and Discovery Article #90940©1997 AAPG Foundation Grants-in-Aid