Foraminiferid Architectural History; A review using the MinLOC and PI Methods

Abstract. Geometrical models of unit volume are used to examine the effects of differing rates of chamber or test volume expansion, growth plan, chamber shape and apertural form upon internal-external lines of communication within foraminiferid tests. The main quantitative measure is the minimum line of communication (MinLOC) from the back of the proloculus to the nearest aperture in contact with the external milieu. The Parsimony Index (PI) is a qualitative measure, here used to illustrate some basic changes in foraminiferid architecture through time. Three general trends from longer to shorter MinLOC are indicated, particularly in shallow water tropical carbonate facies, with climaxes in the Devonian, the Carboniferous to Permian and the Cretaceous to Recent.