An Analysis of Chevron Folds from the Delhi Rocks Around Biliawas, Central Rajasthan

An analysis based on measurements made on the profile sections of several chevron folds developed in the biotitic limestone and calc gneiss units of the Delhi system of rocks around Biliawas in Central Rajasthan reveals that while folds in calc gneisses locked up after no great shortening across the layers had been accomplished and limbs had attained only moderate dips, those in biotitic limestones underwent considerable shortening normal to axial surfaces and locked up at much smaller interlimb angles. Estimates made of the ratios of viscosities between two sets of layers in each lithology indicate that the contrast between properties of two sets of layers is greater in biotitic limestones. The greater shortening in biotitic limestones than in calc gneisses is envisaged rather as a widely differing behaviour of different multilayer complexes than any likely finite strain variability across the area.