Control of crystal shape and size on formation of twin lamellae in calcite: Implications for deep burial diagenetic fabrics in limestones

Abstract

Quantitative data from four shallowly buried and tectonically undisturbed Paleozoic limestones show that twin lamellae develop preferentially in large and irregularly shaped, non-equant crystals. Frequency of lamellae increases with length/width ratio of crystals, and lamellae are more abundant in larger crystals than in small ones. Because burial cements commonly consist of large crystals that fill non-equant remnant voids, these morphologic controls can cause burial cements to undergo preferential twinning. Morphological control on twinning thus causes the seeming paradox of untwinned early cements accompanied by twinned late cements.