SGER: Buckle vs Bend Folding: An Examination of Their Progressive Development, Anti-Atlas Mountains, Morocco

Franklin And Marshall College, Lancaster PA

Investigators

Abstract

Within fold-thrust belts (FTBs), folds that form under shallow crustal conditions (i.e. elastico-frictional regime) initiate primarily by either buckling or bending mechanisms. Theoretical and analog modeling as well as some limited field-based data sets on folding mechanisms under shallow-crustal conditions leave us with two critical unanswered questions: What are the limits (e.g. interlimb angle, bed thickness, strain rate) to buckling and bending? Beyond initial folding, do 'buckle' and 'bend' folds continue to tighten in their own unique ways or, at a certain stage, are their folding mechanisms indistinguishable? Surely, folding is much more complex than most models predict; studying natural fold examples provides a more complete picture to folding histories. The P.I. proposes to better understand folding processes using natural fold examples in the Anti-Atlas FTB (Morocco), which is primarily composed of buckle and bending folds that formed within the elastico-frictional (EF) regime. Unique strain patterns associated with each fold type are accommodated by fracture networks and large-scale cataclastic flow within the EF regime. These fractures will be examined to unravel the strain histories, and therefore, folding mechanisms.