Along-strike changes in fold-thrust belt architecture: Examples from the Hudson Valley, New York

The Hudson Valley fold-thrust belt of eastern New York State involves a relatively thin sequence of shallow-marine Silurian and Lower Devonian strata. Because of the thinness of this sequence, structures of the belt are relatively small. Thus, firstorder ramps and flats, and fault-related folds can be seen in their entirety at a single roadcut. A field trip in the southern half of the Hudson Valley fold-thrust belt, from the latitude of Catskill to the latitude of Rosendale, provides an opportunity to see many examples of these structures, and to discuss the three-dimensional architecture of fold-thrust belts in an orocline. In particular, we will see how along-strike changes in stratigraphy affect fold wavelength and the depth of detachment horizons. The trip also provides the opportunity to examine the relationship between mesoscopic structures (e.g., solution cleavage and veining) and first-order structures.