The role of pore water circulation during the deformation of foreland fold and thrust belts

Abstract

Volume‐loss strain accompanying pressure solution of calcite occurred within both the Umbria‐Marches Apennines of Italy and the Appalachian Mountains of western New York. Data from strain markers show that volume‐loss strain was greater within the shallow portions of the Apennines than within the Appalachians. Within the deeper portions of both fold and thrust belts, strain was nearly volume‐constant. Calcite solubility data suggest that downward circulation of meteoric water is necessary for the 35% volume‐loss strain of the limestones within the Apennines. Strain at a depth of about 1 km was volume‐constant and is interpretated as indicative of restricted pore fluid circulation. In the Appalachians, calcite comprises less than 1% of the clastic rocks, and a 10% volume‐loss of this calcite may occur during circulation of connate or dehydration water derived from dewatering of the shales but in an environment that restricts the circulation of meteoric water. Here, the volume of calcite removed (0.1% of the total rock) is so small that circulation of meteoric water is not necessary for strain by pressure solution.