Diagenesis can be a fundamental control on porosity and permeability, modifying depositional textures. In many carbonate systems, diagenesis starts as early sediment modification in the marine realm, where it can be essentially syndepositional and rapid. Although previous work has shown that reef margin carbonates tend to be better cemented than platform interior sediments, studies quantifying changes in abundance or type of cement across platforms are rare. This study explores spatial variability in the character and extent of early cementation in the context of potential controls by examining well-exposed Holocene reefal debris in the equatorial western Pacific. Preliminary results indicate differences in morphology and texture of cements among atolls and trends in cement volume and morphology along individual transects, from the platform margin to interior.

To explore the variability of early diagenesis, multiple transects from platform margins to interiors sample late Holocene deposits on three atolls in the country of Kiribati. Petrographic and SEM characterization allow for analysis of cement morphology, texture, and abundance, supplemented with stable isotope analysis to constrain the diagenetic environment(s). Integrating porosity and permeability data and quantitative data on early cements within a known spatial and climatic context allows for the creation of predictive conceptual models of spatial heterogeneity. This information is valuable for accurately modeling early diagenesis in strata of similar ancient reservoir systems.